A reduction or elimination of symptoms is obtained by administering the drug selegiline. The invention is also directed to a method for treating patients with cancer by administering a chemotherapeutic agent known to have a toxic affect on peripheral nerves together with selegiline.

The present invention relates to a medical treatment for preventing or alleviating the symptoms associated with peripheral neuropathy caused by disease or exposure to a toxic agent, e.g., a chemotherapeutic cytotoxic agent. A reduction or elimination of symptoms is accomplished by administering the drug selegiline.
Peripheral neuropathy is associated with a wide variety of causes, including genetically acquired conditions, systemic disease or exposure to toxic agents. It can manifest itself as a dysfunction of motor, sensory, sensorimotor or autonomic nerves.
Among the most important toxic agents causing peripheral neuropathy are therapeutic agents, particularly those used for the treatment of neoplastic disease. In certain cases, peripheral neuropathy is a major complication of cancer treatment and is the main factor limiting the dosage of chemotherapeutic that can be administered to a patient (Macdonald, Neurologic Clinics 9:955-967 (1991)). This is true for the commonly administered agents cisplatin, paclitaxel and vincristine (Broun, et al., Am. J. Clin. Oncol. 16:18-21 (1993); Macdonald, Neurologic Clinics 9:955-967 (1991); Casey, et al., Brain 96:69-86 (1973)). The identification of methods for preventing or alleviating dose-limiting peripheral neuropathologic side effects would allow higher, and more therapeutically effective doses of these chemotherapeutics to be administered to patients, i.e., the therapeutic efficacy of such chemotherapeutics is typically a function of dose and therefore, increasing dosage provides increased patient survival (Macdonald, Neurologic Clinics 9:955-967 (1991); Oxols, Seminars in Oncology 16, suppl. 6:22-30 (1989)).
Beyond the potential for increasing the effectiveness of cancer chemotherapy, the identification of new methods for treating peripheral neuropathy has obvious value in alleviating the suffering of patients with a wide variety of systemic diseases and genetic conditions. In many cases, progressive neuropathy in the peripheral nervous system can be debilitating or fatal.
Although selegiline has been used extensively as a treatment for Parkinson""s disease, its effectiveness in the prevention or treatment of peripheral nerve dysfunction caused by toxic agents has not been previously known. The present invention is directed to methods which rely upon this surprising and unexpected discovery to reduce or eliminate symptoms associated with peripheral nerve dysfunction.
Selegiline is a potent and selective irreversible inhibitor of monoamine oxidase B (MAO-B) and has been reported to have an action in protecting or rescuing neurons of the central nervous system. For example, in a rat optic nerve crush model, selegiline has been reported to increase the survival of retinal ganglion cells that are at risk of undergoing apoptosis (Buys, et al., Invest. Opthalmol. Vis. Sci. 35:1484 (1994)). Selegiline has also been shown to have a neuroprotective effect in a model of axotomy-induced cell death in spinal motor neurons of the rat (Iwasaki, et al., J. Neurol. Sci. 125:11-13 (1994)) and to enhance neurite outgrowth in a cultured spinal cord neuron (Iwasaki, et al., Annals of Neurology 36:282-283 (1994)). In addition, selegiline has been reported to increase the survival of CNS neurons after exposure to various chemical toxins such as MPP+, kainic acid, or DSP-4 (Gelowitz, et al., Soc. Neurosci. Abstr. 20:246 (1994); Tatton, et al., J. Neurosci. Res. 31:394-400 (1992); Yu, et al., J. Neurochem. 63:1820-1828 (1994)).
With respect to peripheral nerves, selegiline has been reported to be capable of rescuing axotomized rat facial motor neurons (Salo, et al., J. Neurosci. Res. 31:394-400 (1992)). A recently issued patent also suggests that it may be used in stimulating muscle reinnervation in traumatic and non-traumatic peripheral nerve damage (U.S. Pat. No. 5,444,095).
The present invention is based upon the discovery that selegiline can be used to prevent or alleviate the symptoms associated with peripheral neuropathy. In particular, the invention provides a method for protecting a patient from, or treating a patient for, peripheral neuropathy caused by a toxic agent by administering selegiline in an amount sufficient to reduce or eliminate one or more of the symptoms associated with the neuropathy. Typically, the patient will be a human and the toxic agent will be a chemotherapeutic agent, e.g., an agent administered for the treatment of cancer. Although the method is effective for any toxic chemotherapeutic agent causing dysfunction of peripheral nerves, it is most effective for those agents with particularly severe neuropathic side effects such as cisplatin, paclitaxel, vincristine and vinblastin
Any route of delivery may be used for administering the drug, but preferred routes avoid absorption of selegiline from the gastrointestinal tract. Thus, administration transdermally, buccally, or sublingually are among the preferred methods of delivery. The preferred non-oral dose of selegiline is between 0.01 mg/kg per day and 0.15 mg/kg per day, based upon the weight of the free amine. When the oral route of delivery is used, the preferred dosage range is between 0.15 mg/kg per day and 0.75 mg/kg per day based upon the weight of the free amine (typically between about 10 and 50 mg per day).
The present invention is also directed to a method for treating a patient for peripheral neuropathy caused by a genetically inherited condition or systemic disease by administering selegiline in an amount sufficient to reduce or eliminate one or more of the symptoms associated with the neuropathy. As in the case where peripheral neuropathy is due to exposure to a toxic agent, it is preferred that selegiline be administered by a route that avoids absorption of the drug from the gastrointestinal tract. Transdermal, buccal and sublingual routes of administration are among the routes preferred. Again, the dosage of selegiline for non-oral routes of administration should be between 0.01 mg/kg per day and 0.15 mg/kg per day and, when given orally, the preferred dosage range is between 0.15 mg/kg per day and 0.75 mg/kg per day.
The present invention is also directed to a method for treating a patient with cancer by: a) administering a chemotherapeutic agent known to have a toxic effect on peripheral nerves at a dose effective at slowing the progression of the patient""s cancer; b) concurrently administering selegiline to the patient at a dose effective at preventing, reducing or eliminating the peripheral neuropathy associated with the chemotherapeutic agent; and c) increasing the individual or cumulative dosage of chemotherapeutic agent until peripheral neuropathy becomes unacceptably severe. Individual dosage refers to the amount of chemotherapeutic given at a single time, e.g. in a single infusion or injection, whereas cumulative dosage is the total amount of a chemotherapeutic administered over the full course of therapy. Thus, cumulative dosage may be increased by increasing individual dosages, extending the period of therapy or both increasing individual dosages and extending the length of therapy.
The present invention provides the following:
In a method for maximizing the individual or cumulative dose of an anti-neoplastic agent used in the treatment of a patient suffering from a cancer that exhibits a dose-dependent response to said agent, the improvement that comprises the concurrent administration of a selegiline compound in an amount sufficient to permit the individual or cumulative dose of said agent to be maximized without unacceptably severe neurotoxic side effects.
As used herein xe2x80x9cconcurrentxe2x80x9d administration of selegiline and chemotherapeutic means that the drugs are given sufficiently close in time so that their therapeutic effects overlap. The term xe2x80x9cunacceptably severexe2x80x9d refers to side effects that the patient finds intolerable or which the patient""s physician judges to reflect neuropathy that poses so serious a threat to the patient""s health that the dosage of chemotherapeutic agent must be reduced or terminated. Typically, the patient will be a human. The preferred chemotherapeutic agents are cisplatin, paclitaxel, vincristine and vinblastine.
As with the methods discussed previously, selegiline may be administered by any route, but routes that avoid absorption across the gastrointestinal tract, e.g., transdermal, buccal and sublingual routes, are generally preferred. The non-oral dosage of selegiline administered in conjunction with chemotherapeutic agent should, preferably, be between 0.01 mg/kg per day and 0.15 mg/kg per day based upon the weight of the free amine. In general, patients administered selegiline orally should receive a dose of between 0.15 mg/kg per day and 0.75 mg/kg per day.
In the following description, reference will be made to various methodologies well known to those skilled in the art of medicine and pharmacology. Such methodologies are described in standard reference works setting forth the general principles of these disciplines.
A. Definitions
Peripheral Neuropathy;
As used herein, the term xe2x80x9cperipheral neuropathyxe2x80x9d refers to abnormal function or pathological changes in nerves located outside of the brain or spinal column. The nerves may be sensory, motor, sensorimotor or autonomic and dysfunction may manifest itself in any of the various symptoms discussed herein.
Toxic Agent;
For the purposes of the present invention, the term xe2x80x9ctoxic agentxe2x80x9d is defined as any substance that, through its chemical action, impairs the normal function of one or more components of the peripheral nervous system. The definition includes agents that are airborne, ingested as a contaminant of food or drugs, or taken deliberately as part of a therapeutic regime.
Selegiline;
Selegiline, also known as R-(xe2x88x92)-N-methyl-N-(prop-2-ynyl)-2-aminophenylpropane, L-(xe2x88x92)-deprenyl, or R-(xe2x88x92)-deprenyl, has the following structural formula:
Unless otherwise specified, the term xe2x80x9cselegiline,xe2x80x9d as used herein includes both the free base and pharmacologically acceptable salts of selegiline.
B. Symptoms of Peripheral Neuropathy
The present invention is directed to the prevention or treatment of peripheral neuropathy using selegiline. The neuropathy may be genetically acquired, developed as the result of systemic illness, or due to the exposure of a patient to a toxic agent. The treatment objective is to prevent, reduce or eliminate the symptoms associated with peripheral nerve dysfunction.
Symptoms vary widely depending upon the cause of the peripheral nerve damage and the particular types of nerves affected. Dysfunction of peripheral sensory neurons typically manifests itself as a loss of sensation in the limbs or elsewhere. For example, there may be numbness in the fingers, toes or elsewhere. Clinically, a physician may evaluate such loss by testing the ability of a patient to sense pain, vibration, or temperature or by using nerve conductance studies.
Dysfunction in peripheral motor neurons typically manifests itself as a clumsiness in performing physical tasks or as muscular weakness. For example, a patient may experience difficulty in buttoning a shirt or combing their hair. Muscular weakness may cause patients to become exhausted after relatively minor exertion and, in some cases, may create a difficulty in standing or walking. Clinically, a physician may diagnosis dysfunction in motor neurons using electrophysiological tests or by direct evaluation of patient strength or dexterity. Peripheral motor neuron dysfunction may also be diagnosed on the basis of an attenuation or absence of a neuromuscular reflex, e.g., as an absence of the ankle jerk reflex.
Dysfunction of peripheral autonomic nerves may lead a patient to experience constipation or cardiac irregularities or toxicities. It is often seen clinically as an attenuation of the postural hypotensive reflex.
C. Diseases and Toxic Agents Causing Peripheral Neuropathy
The particular systemic disease, hereditary condition or toxic agent responsible for peripheral neuropathy is not critical to the invention. Thus, selegiline is effective for neuropathies associated with systemic diseases such as: uremia; childhood cholestatic liver disease; chronic respiratory insufficiency; alcoholic polyneuropathy; multiple organ failure; sepsis; hypo-albuminemia; eosinophilia-myalgia syndrome; hepatitis; porphyria; hypo-glycemia; vitamin deficiency; chronic liver disease; primary biliary cirrhosis; hyperlipidemia; leprosy; Lyme disease; herpes zoster; Guillain-Barre syndrome; chronic inflammatory demyelinating polyradiculoneuropathy; sensory perineuritis; acquired immunodeficiency syndrome (AIDS)xe2x80x94associated neuropathy; Sjogren""s syndrome; primary vasculitis (such as polyarteritis nodosa); allergic granulomatous angiitis; hypersensitivity angiitis; Wegener""s granulomatosis; rheumatoid arthritis; systemic lupus erythematosis; mixed connective tissue disease; scleroderma; sarcoidosis; vasculitis; systemic vasculitides; acute tunnel syndrome; pandysautonomia; primary, secondary, localized or familial systemic amyloidosis; hypothyroidism; chronic obstructive pulmonary disease; acromegaly; malabsorption (sprue, celiac disease); carcinomas (sensory, sensorimotor, late and demyelinating); lymphoma (including Hodgkin""s), polycythemia vera; multiple myeloma (lytic type, osteosclerotic, or solitary plasmacytoma); benign monoclonal gammopathy; macroglobulinemia; cryoglobulinemia; tropical myeloneuropathies; herpes simplex infection; cytomegalovirus infection; and diabetes.
Genetically acquired neuropathies suitable for treatment by selegiline include, without limitation: peroneal muscular atrophy (Charcot-Marie-Tooth Disease) hereditary amyloid neuropathies, hereditary sensory neuropathy (type I and type II), porphyric neuropathy, hereditary liability to pressure palsy, Fabry""s Disease, adrenomyeloneuropathy, Riley-Day Syndrome, Dejerine-Sottas neuropathy (hereditary motor-sensory neuropathy-III), Refsum""s disease, ataxia-telangiectasia, hereditary tyrosinemia, anaphalipoproteinemia, abetalipoproteinemia, giant axonal neuropathy, metachromatic leukodystrophy, globoid cell leukodystrophy, and Friedrich""s ataxia.
A very large number of toxic agents have been described that cause peripheral neuropathy amenable to treatment by the present invention. The list includes, but is not limited to, acetazolamide, acrylamide, adriamycin, alcohol, almitrine, amiodarone, amphotericin, arsenic, aurothioglucose, carbamates, carbon disulfide, carboplatin, chloramphenicol, chloroquine, cholestyramine, cisplatin, clioquinol, colestipol, colchicine, colistin, cycloserine, cytarabine, dapsone, dideoxycytidine, dideoxyinosine, dideoxythymidine, disulfiram, doxorubicin, ethambutol, ethionamide, glutethimide, gold, hexacarbons, hormonal contraceptives, hexamethylolmelamine, hydralazine, hydroxychloroquine, imipramine, indomethacin, inorganic lead, inorganic mercury, isoniazid, lithium, methylmercury, metformin, methylbromide, methylhydrazine, metronidazole, misonidazole, nitrofurantoin, nitrogen mustard, nitrous oxide, organophosphates, ospolot, penicillin, perhexiline, perhexiline maleate, phenytoin, platinum, polychlorinated biphenyls, primidone, procarbazine, pyridoxine, sodium cyanate, streptomycin, sulphonamides, suramin, tamoxifen, paclitaxel, thalidomide, thallium, triamterene, trimethyltin, L-tryptophan, vacor, vindesine, megadoses of vitamin A, megadoses of vitamin D, and zimeldine.
Although the particular disease or toxic agent causing peripheral nerve damage is not critical, the present invention will be particularly valuable in the treatment of peripheral neuropathy resulting from the administration of chemotherapeutic agents to cancer patients. Among the chemotherapeutics known to cause peripheral neuropathy are vincristine, vinblastine, cisplatin, paclitaxel, procarbazine, dideoxyinosine, cytarabine, alpha interferon, and 5-fluorouracil (see Macdonald, Neurologic Clinics 9: 955-967 (1991)).
D. Method of Preventing or Treating Peripheral Neuropathy by the Administration of Selegiline
Dosage
The total daily dosage of selegiline administered to a patient, typically a human patient, should be at least the amount required to minimize, reduce or eliminate one or more of the symptoms associated with peripheral neuropathy, typically one of the symptoms discussed above. Ordinarily, the attending physician will administer an initial daily non-oral dose of at least about 0.01 mg per kg of body weight, calculated on the basis of the free secondary amine, with progressively higher doses being employed depending upon the response to therapy. The final daily dose will be between about 0.05 mg/kg of body weight and about 0.15 mg/kg of body weight (all such doses again being calculated on the basis of the free secondary amine).
These are simply guidelines since the actual dose must be carefully selected and titrated by the attending physician based upon clinical conditions. The optimal daily dose will be determined by methods known in the art and will be influenced by factors such as the age of the patient, the condition or disease associated with the peripheral meuropathy, the severity of both the neuropathy and the disease, the condition of the patient to whom treatment is being given, the desired degree of therapeutic response, and the concomitant therapies being administered. Dosages may be provided in either a single or multiple dosage regimen
Dosage Forms and Route of Administration
Any route of administration and dosage form is compatible with the present invention and there are numerous references that provide guidance in this respect. For example, U.S. Pat. No. 4,812,481 discloses the use of concomitant selegiline-amantadine therapy in which selegiline is used with amantadine in oral, peroral, internal, pulmonary, rectal, nasal, vaginal, lingual, intravenous, intraarterial, intracardial, intramuscular, intraperitoneal, intracutaneous, and subcutaneous formulations. U.S. Pat. No. 5,192,550 describes a dosage form for selegiline comprising an outer wall with one or more pores, in which the wall is impermeable to selegiline but permeable to external fluids. This dosage form may have applicability for oral, sublingual, or buccal administration. Similarly, U.S. Pat. No. 5,387,615 discloses a variety of selegiline compositions, including tablets, pills, capsules, powders, aerosols, suppositories, skin patches, parenterals, and oral liquids, include oil aqueous suspensions, solutions, and emulsions. Further disclosed therein are selegiline-containing sustained release (long acting) formulations and devices.
Although any route of administration is compatible with the present invention, those that avoid the absorption of selegiline from the gastrointestinal tract are generally preferred. Thus, preferred routes include parenteral, transdermal, buccal, intraocular and sublingual administration. Parenteral compositions containing selegiline may be prepared according to conventional techniques. For example, sterile isotonic saline may be used in preparations designed for intamuscular, intravenous, intrathecal or intrarterial delivery. Sterile isotonic solutions can also be employed for intraocular administration.
Transdermal dosage unit forms can be prepared utilizing a variety of techniques that have been described in the art. For example, in U.S. Pat. Nos. 4,861,800; 4,868,218; 5,128,145; 5,190,763; and 5,242,950; and in the foreign patent documents EP-A 404807; EP-A 509761; and EP-A 593807. A monolithic patch structure can be utilized in which selegiline is directly incorporated into the adhesive and this mixture is cast on to a backing sheet. Alternatively, selegiline as an acid addition salt can be incorporated into a multi layer patch which effects a conversion of the salt to selegiline-free base, as described for example in EP-A 593807. One can also employ a device using a lyotropic liquid crystalline composition in which, for example, 5-15% of selegiline is combined with a mixture of liquid and sold polyethylene glycols, a polymer, and a non-ionic surfactant, optionally with the addition of propylene glycol and an emulsifying agent. For further details on the preparation of such transdermal formulations, reference can be made to EP-A 5509761.
Buccal and sublingual dosage forms of selegiline may be prepared utilizing techniques described in, for example, U.S. Pat. Nos. 5,192,550; 5,221,536; 5,266,332; 5,057,321; 5,446,070; 4,826,875; 5,304,379; or 5,354,885.
Form of Selegiline
The present invention is not limited to a particular form of selegiline and the drug may be used either as a free base or as a pharmaceutically acceptable acid addition salt. In the latter case, the hydrochloride salt is generally preferred. However, other salts useful in the invention include those derived from organic and inorganic acids such as, without limitation, hydrobromic acid, phosphoric acid, sulfuric acid, methane sulfonic acid, acetic acid, tartaric acid, lactic acid, succinic acid, citric acid, malic acid, maleic acid, aconitic acid, salicylic acid, thalic acid, embonic acid, enanthic acid, and the like.
Manner of Treatment
The methods disclosed herein may be used for both human and non-human subjects. With regard to the latter, the methods are particularly, but not exclusively, directed to domesticated mammals such as canine and feline species.
Treatment by the administration of selegiline should be continued until the symptoms associated with peripheral neuropathy subside. The drug may be either administered at regular intervals (e.g., twice a day) or delivered in an essentially continuous manner, e.g., via a transdermal patch. Patients should be regularly evaluated by physicians, e.g. once a week, to determine whether there has been an improvement in symptoms and whether the dosage of selegiline needs to be adjusted. Since delayed progressive neuropathy has been demonstrated after the cessation of cisplatin therapy (see e.g. Grunberg et al., Cancer Chemother. Pharmacol. 25:62-64 (1989)), it is preferred that administration of selegiline be continued for a period (e.g. from about 1- 12 months) after the end of chemotherapy.
E. Method of Treating Cancer Patients Using a Combination of Selegiline and Chemotherapeutic
The present invention is also directed to a method for treating cancer patients using a combination of chemotherapeutic agent and selegiline. Except as noted below, the same considerations discussed in the sections above apply equally to the situation in which selegiline is used as part of a therapeutic regime for such patients.
Chemotherapeutic Agents
Selegiline may be used in combination with any chemotherapeutic agent that causes peripheral neuropathy as a side effect. However, treatment is especially preferred for chemotherapeutic agents that are so toxic that their dosage is limited by the peripheral neuropathy which they cause. Included in this group are paclitaxel, cisplatin, vincristine and vinblastine. By preventing or reducing the peripheral neuropathy associated with these agents, selegiline allows higher individual doses to be administered to patients, thereby increasing the overall efficacy of the therapy. In addition, the administration of selegiline allows patients to receive a higher cumulative dose of chemotherapeutic agent. Increased cumulative dose may result from higher doses of agent being administered at each therapeutic cycle, an increase in the number of cycles, or a combination of higher doses and more cycles.
The most preferred chemotherapeutic agents for use in the present invention are cisplatin and paclitaxel, both of which have severe toxicity for peripheral nerves limiting their upper dosages (see Macdonald, Neurologic Clinics 9: 955-967 (1991)). Although dose intensity of these agents is an important factor in achieving optimal therapeutic results, doses substantially above about 100-120 mg/m2 for cisplatn (Ozols, Seminars in Oncology 16: 22-30 (1989)) and about 175 mg/m2-225 mg/m2 for paclitaxel (Gianni, et at., J. Nat""l Cancer Inst. 87:1169-75 (1995)), typically cannot be given.
The symptoms associated with peripheral neuropathy caused by the administration of cisplatin include sensory polyneuropathy with paresthesias, vibratory and proprioceptive loss, loss of pin and temperature sensation, and reduced deep tendon reflexes (see Macdonald, Neurologic Clinics 9:955-967 (1991); Ozols, Seminars in Oncology 16, suppl. 6:22-30 (1989)). Symptoms associated with other agents such as vincristine and paclitaxel include loss of deep tendon reflex response at the ankle which may progress to complete areflexia, distal symmetric sensory loss, motor weakness, foot drop, muscle atrophy, constipation, ileus, urinary retention, impotence, and postural hypotension (Id.; Casey, et al., Brain 96:69-86 (1973)). For the purposes of the present invention, the severity of these symptoms is considered to be unacceptable when either a patient judges them to be intolerable or the patient""s physician judges them to pose so serious a threat to the patient""s health that the dosage of chemotherapeutic agent must be reduced or discontinued.
Dosage Forms and Routes of Administration
The particular route of administration that is most preferred will be determined by clinical considerations and may include any of the routes of delivery or dosage forms discussed above. Routes of administration which avoid gastrointestinal absorption will often be preferred in that these are believed to reduce the concentration of undesirable metabolic products of selegiline generated in vivo. Thus, preferred routes will typically include transdermal, parenteral, sublingual and buccal administration.
Dosage and Manner of Treatment
In some instances, patients administered selegiline according to the invention, will already have been on chemotherapy at the time that selegiline treatment is initiated. As a result, an upper limit on dosage of chemotherapeutic may already have been established, beyond which the patient experiences unacceptably severe peripheral neuropathy. In these cases, administration of the chemotherapeutic agent should be maintained and treatment with selegiline initiated at a non-oral dose of between 0.01 mg/kg of body weight per day and 0.15 mg/kg per day. The exact time at which chemotherapeutic and selegiline are given relative to one another is not critical to the invention provided that their therapeutic effects overlap. For example, it is not essential that chemotherapeutic and selegiline be administered in a single dosage form or within an hour or two of one another.
In instances in which a patient is taking multiple drugs or in which there is some reason to believe that they may be unusually sensitive to selegiline, it may be desirable to start with a low initial dose (e.g., 0.01 mg/kg) in order to ensure that the patient is able to tolerate the medication. Once this is established, the dosage may be adjusted upward with the preferred final dosage for non-oral routes of administration being approximately in the range of 0.05 to 0.15 mg/kg per day. When given orally, patients should typically receive a total daily dose of between 0.15 mg/kg per day and 0.75 mg/kg per day divided into several doses. For example, a patient may receive a dose of 5 mg orally, twice a day.
The effect of selegiline on the symptoms of peripheral neuropathy should be evaluated by the patient over a period of time and by the patient""s physician on a regular basis (e.g., once a week). If the results reveal that symptoms have not subsided, the daily dosage of non-oral selegiline may be increased up to a limit of about 0.15 mg/kg. Once a concentration of selegiline is established which is effective at reducing symptoms, the dosage of chemotherapeutic is increased until a new upper limit is established, i.e. until a dosage is established which cannot be exceeded without causing unacceptable side effects. The administration of selegiline should be continued for a period of time after the administration of chemotherapeutic has ceased in order to prevent delayed progressive neuropathy. For example, the patient may continue to receive selegiline for a month or more after the end of chemotherapy.
The same basic procedure described above can be used for patients beginning chemotherapy. In these cases, both the dosage of chemotherapeutic agent and selegiline will have to be established. The preferred procedure is to begin by pretreating patients with selegiline before the administration of chemotherapeutic is begun. For example, a patient may be given 10 mg of selegiline per day for a period of one week before treatment with chemotherapeutic is initiated. The dosages of both chemotherapeutic and selegiline are then optimized as described above. Again, selegiline administration should be continued after the administration of chemotherapeutic has stopped.
The examples below are for illustrative purposes only and are not intended to limit the scope of the invention.

Method for preventing and treating peripheral neuropathy by administering selegiline


A wound mediating device is provided to facilitate healing of tissue. The wound mediating device includes a wound mediating substance encapsulated in microbubbles which are suspended in a slurry. The slurry is stored in, and supplied from, any suitable container configured for use with a surgical instrument capable of propelling the slurry towards tissue.

1. Technical Field
The present disclosure relates to wound mediating devices. More particularly, the present disclosure relates to a wound mediating device using a pressurized fluid to serve as a propellant for the wound mediating substances.
2. Background of Related Art
Many surgical procedures are enhanced by the use of wound mediating substances to assist in the healing of tissue. The substances may include blood clotting factors, wound closing adhesives, growth factors, interleukins, cytokines, inflammatory mediating factors, chemokines, matrix-metalloproteinase or other biochemicals known to mediate wound healing. These wound mediating substances are typically expressed naturally in tissue after the surgery and wound healing can be enhanced through topical application of these substances. Application generally includes direct, manual application of the mediating substances to the appropriate area of the tissue.
Various surgical instruments are known for treating tissue. For example, surgical instruments used for tissue division, dissection, ablation, or for arresting blood loss and coagulation are well-known. In a particular application, for example a coagulation instrument, an electrode is used in conjunction with a heated probe to arrest bleeding. However, since the probe must come into close contact with the tissue, the probe may adhere to the tissue during probe removal and possibly cause repeat bleeding.
Some prior art devices include a tube-like coagulation instrument in which an ionizable gas is supplied to the instrument and ionized by the electrode. The atmosphere of ionized gases is beneficial because it helps focus and arc energy adjacent the electrode, displace oxygen from the area, and reduce oxidative stress of the tissue. The gas is propelled from the instrument toward the tissue.
However, energy based medical devices often rely on the body's own wound healing process as an integral element of their use. As noted above, wound mediating substances are often manually applied to the tissue after the surgery to mediate wound healing. This, however, requires direct contact of the applicator, i.e., wand, brush, probe, etc. to the tissue which may re-injure the previously operated on tissue.


A ramped cap unit is provided for installation into a swimming pool in a position covering a main pool drain equipped with an upstanding antivortex safety drain cover plate, wherein the ramped cap unit has a smoothly contoured shape to permit a pool cleaner device to travel thereover without interrupting or obstructing cleaning operation. The cap unit comprises a generally inverted saucer defining a smoothly sloping and convex or ramped upwardly presented surface having a diametric size and shape to fit over the safety drain cover plate. An array of ribs formed on the underside of the cap unit engage an outer periphery of the upstanding cover plate to retain the cap unit in position thereon. A large plurality of vents are formed in the cap unit at spaced-apart locations to permit downward water flow therethrough substantially without disrupting the antivortex and safety functions of the underlying drain cover plate. The ramped upper surface of the cap unit permits a pool cleaner device to climb directly over the cap unit in the course of pool cleaner travel over submerged pool surfaces to collect and dislodge particulate debris settled thereon.

This invention relates generally to a ramped cap unit for use in combination with an antivortex or safety cover plate of the type installed over a main suction drain of a swimming pool or the like, wherein the ramped cap unit permits a pool cleaner device to travel directly over the ramped cap unit and the underlying safety drain cover plate without interrupting pool cleaning operation, and further without disrupting the antivortex and safety functions of the underlying safety cover plate.
Pool cleaner systems and related devices are generally well known in the art for use in maintaining residential and commercial swimming pools in a clean and attractive condition. In this regard, swimming pools conventionally include a water filtration system equipped with a pump for drawing or suctioning water from the pool for circulation through a filter canister having filter media therein to remove and collect water-entrained debris such as leaves and twigs as well as fine particulate including sand and silt. In a typical arrangement, at least a portion of the pool water is vacuum-drawn over a weir mounted within a so-called skimmer well positioned substantially at the water surface to draw and collect floating debris to the filter equipment, while another portion of the pool water is vacuum-drawn to the filter equipment through at least one so-called main suction drain located in the pool floor typically at a deep end thereof. From the filter canister, the water is recirculated to the pool via one or more return lines. Such filtration equipment is normally operated for several hours on a daily basis and serves, in combination with traditional chemical treatments such as chlorination or the like, to maintain the pool water in a clean and clear sanitary state.
The water filtration system is generally ineffective, however, to filter out debris which settles onto submerged floor and side wall surfaces of the swimming pool. In the past, settled debris has typically been removed by coupling a vacuum hose to the suction side of the pool water filtration system, such as by connecting the vacuum hose to the skimmer well located near the water surface at one side of the pool, and then manually moving a vacuum head coupled to the hose over the submerged pool surfaces to vacuum settled debris directly to the filter canister where it is collected and separated from the pool water. However, manual vacuuming of a swimming pool is a labor intensive task and is thus not typically performed by the pool owner or pool cleaning service personnel on a daily basis.
So-called automatic pool cleaner devices have been developed over the years for cleaning submerged pool surfaces, thereby substantially eliminating the need for labor intensive manual vacuuming. Such automatic pool cleaners typically comprise a relatively compact cleaner housing or head coupled to the pool water filtration system by a hose and including water-powered means for causing the cleaner to travel about preferably along a random path within a swimming pool to dislodge and collect settled debris. In one form, the pool cleaner is connected to the return or pressure side of the filtration system for receiving positive pressure water which powers a turbine for rotatably driving cleaner wheels, and also functions by venturi action to draw settled debris into a filter bag. See, for example, U.S. Pat Nos. 3,882,574; 4,558,479; 4,589,986; and 4,734,954. In another form, the pool cleaner is coupled by a vacuum hose to the suction side of the filtration system, whereby water is drawn through the pool cleaner to operate a drive mechanism for transporting the cleaner within the pool while vacuuming settled debris to the filter canister of the pool filtration system. See, for example, U.S. Pat. Nos. 3,803,658; 4,023,227; 4,133,068; 4,208,752; 4,643,217; 4,679,867; 4,729,406; 4,761,848; 5,105,496; 5,265,297; and 5,634,229. See also, copending U.S. Ser. No. 09/090,894, filed Jun. 4, 1998, and 09/176,532, filed Oct. 21, 1998.
In addition, in recent years, antivortex or safety cover plates have been developed for covering suction drains in a swimming pool or spa to reduce or eliminate the risk of suction-entrapment of a swimmer, particularly by suction-entrapment of a swimmer""s hair or clothing. More specifically, the water filtration system pump is normally designed to draw water to the filtration equipment at a substantial flow rate and thus has the capacity to develop a significant suction or vacuum within filtration system flow lines. If a significant portion of the flow area of a suction drain is obstructed by a swimmer""s hair or clothing or portion of the body while the filtration system is operating, the swimmer can be vacuum-drawn and retained at the drain with a substantial force to result in suction-entrapment of the swimmer and creating a risk of drowning. To safeguard against suction-entrapment accidents, many swimming pools are being constructed or retrofitted with an antivortex safety drain cover plate mounted over each pool suction drain and defining a geometric array of spaced-apart vents positioned to reduce or eliminate the risk of any significant portion of the vents being obstructed by a swimmer at one time.
Unfortunately, such safety drain cover plates typically project upwardly a short distance from the pool floor to define the multiple vents which may open in different directions, whereby the cover plate provides a raised obstruction to a pool cleaner as it traverses submerged pool surfaces to perform its desirable cleaning functions. In this regard, the pool cleaner can become trapped against the raised cover plate to interrupt normal cleaning operation.
The present invention relates to a relatively simple yet effective ramped cap unit for installation into a swimming pool in a position overlying an upstanding safety drain cover plate, wherein the cap unit is contoured to permit a pool cleaner to climb and travel directly thereover for uninterrupted cleaning operation, and further wherein the cap unit includes a large plurality of open flow vents to permit downward water flow therethrough substantially without disrupting the antivortex and safety functions of the underlying drain cover plate.
In accordance with the invention, a ramped cap unit is provided for installation into a swimming pool in a position covering a main pool drain equipped with an upstanding antivortex safety drain cover plate, wherein the ramped cap unit has a smoothly contoured shape to permit a pool cleaner device to travel thereover without interrupting or obstructing cleaning operation.
The ramped cap unit comprises a generally inverted saucer defining a smoothly sloping and convex or ramped upwardly presented surface having a diametric size and shape to fit over the safety drain cover plate. An array of ribs formed on the underside of the cap unit engage an outer periphery of the upstanding cover plate to retain the cap unit in position thereon, and to define a downwardly open central cavity into which the upstanding antivortex safety cover plate is nestably received. A large plurality of vents are formed in the cap unit at spaced-apart locations to permit downward water flow therethrough substantially without disrupting the antivortex and safety functions of the underlying drain cover plate. The ramped upper surface of the cap unit permits a pool cleaner device to climb directly over the cap unit in the course of pool cleaner travel over submerged pool surfaces to collect and dislodge particulate debris settled thereon.
In a preferred configuration, the ramped cap unit comprises a central disk having a size and shape corresponding generally with the size and shape of the safety cover plate. The central disk is assembled with an outer annular ring which may by formed from an assembled plurality of part-circle ring segments. Each ring segment has a plurality of vents formed therein to permit downward water flow therethrough to the underside of the annular ring into a plenum chamber in flow communication with vents formed in the safety cover plate. The annular ring tapers radially outwardly and downwardly from the central disk to an outer perimeter disposed substantially flush with the pool floor.
Other features and advantages of the present invention will become more apparent from the following detailed description, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention.

Ramped cap unit for a main pool drain cover plate


A high durability circular polarizer includes an unprotected K-type polarizer, such as a KE polarizer sheet, and a quarter-wavelength retarder. An optical system using the circular polarizer further includes an emissive display module such as an organic light emitting diode or a plasma display device.

This invention relates to circular polarizers, and more particularly to high durability circular polarizers for use with emissive displays.
Unpolarized ambient light waves vibrate in a large number of directions without a single characterizing electromagnetic radiation vector. By contrast, plane polarized light consists of light waves having a direction of vibration along a single electromagnetic radiation vector. Also, circularly polarized light has a direction of vibration along an electromagnetic radiation vector that rotates as the light propagates through space. Polarized light has many applications in electro-optical devices, such as the use of plane and circular polarizing filters to reduce glare in displays.
Much commercial attention has been directed to the development and improvement of flat panel displays, particularly flat panel displays that are thinner and more compact than displays requiring backlighting for luminescence. Such flat panel displays may use emissive or electroluminescent displays, i.e., self-luminous displays for which no backlight is required.
Polarizers in the form of synthetic polarizing films are desirable for their comparative ease of manufacture and handling and the comparative ease with which they may be incorporated into electro-optical devices such as flat panel displays. In general, plane polarizing films have the property of selectively passing radiation vibrating along a given electromagnetic radiation vector and absorbing electromagnetic radiation vibrating along a second electromagnetic radiation vector based on the anisotropic character of the transmitting film medium. Plane polarizing films include dichroic polarizers, which are absorbing plane polarizers utilizing the vectorial anisotropy of their absorption of incident light waves. The term xe2x80x9cdichroismxe2x80x9d refers to the property of differential absorption of the components of incident light, depending on the vibration directions of the component light waves. Light entering a dichroic plane polarizing film encounters two different absorption coefficients along transverse planes, one coefficient being high and the other coefficient being low. Light emerging from a dichroic film vibrates predominantly in the plane characterized by the low absorption coefficient.
Dichroic plane polarizing films include iodine, dyestuff and H-type polarizers. An H-type polarizer is a synthetic dichroic sheet polarizer including a polyvinyl alcohol-iodine complex. Such a chemical complex is referred to as a chromophore. The base material of an H-type polarizer is a water-soluble high molecular weight substance, and the resulting film has relatively low moisture and heat resistance and tends to curl, peel or otherwise warp when exposed to ambient atmospheric conditions.
In contrast to H-type polarizers and other synthetic dichroic plane polarizers are K-type polarizers. A K-type polarizer is a synthetic dichroic plane polarizer based on molecularly oriented polyvinyl alcohol (PVA) sheets or films with a balanced concentration of light-absorbing chromophores. A K-type polarizer derives its dichroism from the light absorbing properties of its matrix, not from the light-absorbing properties of dye additives, stains, or suspended crystalline materials. Thus, a K-type polarizer may have both good polarizing efficiency and good heat and moisture resistance.
An improved K-type polarizer, referred to as a KE polarizer, is manufactured by 3M Corp., Norwood, Mass. The KE polarizer has improved polarizer stability under severe environmental conditions, such as high temperatures and high humidity. In contrast to H-type polarizers, in which the light absorption properties are due to the formation of a chromophore between PVA and tri-iodide ion, KE polarizers are made by chemically reacting the PVA by an acid catalyzed, thermal dehydration reaction. The resulting chromophore, referred to as polyvinylene, and the resulting polymer may be viewed as a block copolymer of vinylalcohol and vinylene.
For H-type polarizers, stability is achieved by sandwiching the polarizer between two plastic substrates, such as two layers of cellulose triacetate (CTA), one on each side of the polarizer. However, even in these structures the application of heat, humidity and/or vacuum can adversely affect the properties of the polarizer. By contrast, K-type polarizers such as KE polarizers do not need to be sandwiched between sheets of CTA. The polyvinylene chromophore of the KE polarizer is an extremely stable chemical entity, since the chromophore is intrinsic to the polymer molecule. This chromophore is thermally stable as well as resistant to attack from a wide range of solvents and chemicals.
A K-type polarizer such as a KE polarizer has several advantages over other types of polarizers, e.g., iodine and dyestuff polarizers. K-type polarizers have more durable chromophores, are thinner, and may be designed with variable transmission levels. Most notably, K-type polarizers such as KE polarizers may be used in applications that require high performance under severe environmental conditions, including high temperatures and high humidity, such as 85xc2x0 C. and 85% relative humidity, for extended periods of time. Under such extreme environmental conditions, the stability of iodine and dyestuff polarizers is greatly reduced, thus limiting their usefulness in applications such as emissive flat panel displays. Due to the inherent chemical stability of K-type polarizers, a wide variety of adhesive formulations, including pressure sensitive adhesives, can be applied directly to K-type polarizers. Further, a single-sided plastic support is adequate to give physical support for K-type polarizers, and since this support can be located outside of the display module, it need not be optically isotropic and lower-cost substrates such as polyethylene terephthalate (PET) are acceptable alternatives. Moreover, the ability to construct single-sided laminates allows the optical structures to be thinner, allowing for additional flexibility in the design and manufacture of flat panel display elements. These advantages of K-type polarizers may be used in optical applications such as flat panel displays.
A circular polarizer may be constructed of a plane polarizer and a quarter-wavelength retarder. A quarter-wavelength retarder shifts the phase of light waves propagating along one plane through the retarder by one-quarter wavelength, but does not shift the phase of light waves propagating through the retarder along a transverse plane. The result of combining light waves that are one-quarter wavelength out of phase and that vibrate along perpendicular planes is circularly polarized light, for which the electromagnetic radiation vector rotates as the combined light waves travel through space.
Circularly polarized light may be described with respect to two distinct polarization states: left-handed (L) and right-handed (R) circularly polarized light. A circular polarizer absorbs light of one of these polarization states and transmits light of the other polarization state. The use of circular polarizers to reduce glare in displays is well known. In particular, light from an emissive display can be selectively transmitted through a circular polarizer, while background ambient light reflected in the display, which causes glare, may be reduced or eliminated.
A typical thin film circular polarizer 10 is shown in FIG. 1. A dichroic plane polarizer 12 such as an iodine polarizer usually has 3 mil cellulose triacetate (CTA) coatings 14, 16 applied to both surfaces of the polarizer prior to laminating the polarizer to a quarter-wavelength retarder 18. The cellulose tri-acetate coatings in this construction protect the dichroic plane polarizer from heat and moisture, which can damage the polarizer.
In general, in one aspect, the invention features a high durability circular polarizer including an unprotected K-type polarizer and a quarter-wavelength retarder.
Implementations of the invention may also include one or more of the following features. The K-type polarizer may include a KE polarizer sheet. The K-type polarizer and the quarter-wavelength retarder may be thin films.
The K-type polarizer may have a first surface and the quarter-wavelength retarder may have a lower surface, and the circular polarizer may include a first adhesive layer disposed on the first surface of the K-type polarizer to secure the K-type polarizer to the lower surface of the quarter-wavelength retarder. The K-type polarizer may have a second surface, and the circular polarizer may include a support layer disposed on the second surface of the K-type polarizer. The support layer may include polyethylene terephthalate. The quarter-wavelength retarder may have a top surface, and the circular polarizer may include a second adhesive layer disposed on the top surface of the quarter-wavelength retarder for attaching the circular polarizer to a display surface. A removable release liner may be disposed over the second adhesive layer.
In general, in another aspect, the invention features a high durability circular polarizer including a K-type polarizer lacking a protective coating thereon and a quarter-wavelength retarder.
In general, in another aspect, the invention features an optical system, including an emissive display module and a circular polarizer including an unprotected K-type polarizer and a quarter-wavelength retarder.
Implementations of the invention may also include one or more of the following features. The emissive display may be an organic light emitting diode or a plasma display device. The circular polarizer may absorb ambient light to decrease interference of the ambient light with a light signal emitted by the display module.
An advantage of the present invention is that a high durability circular polarizer may be constructed that will be stable in severe environmental conditions such as high temperatures and high humidity. A further advantage of the present invention is that an emissive display may be constructed with such a high durability circular polarizer.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.

High durability circular polarizer for use with emissive displays


The scissors for cutting filamentary material, especially hair, include two shanks (4) pivotally connected to each other at a pivot joint (2); respective blades (7) for cutting the filamentary material extending from the shanks (4) and an electrically powered vibrator (5) for vibrating one of the shanks in a longitudinal direction at an ultrasonic frequency and with a displacement of about 100 to 200 xcexcm. The pivot joint (2) includes a nail (14) extending from one shank, an eccentric washer (15) embedded in the other shank which engages around the nail and a miniature motor (17) for rotating the washer (15) and the shank in which it is embedded. In other embodiments the electrically powered vibrator (5) include a piezoelectric transducer (8) arranged to connect a shank to one of the blades or an exciter coil (19) wrapped around a strut region made of a magnetostrictive material in one shank.

1. Field of the Invention
The invention relates to a pair of scissors with two shanks joined to one another via a pivot joint, in particular hairdressing shears.
2. Prior Art
Known scissors operate with cutting edges that move about a common, fixed pivot point relative to one another. In the process, the cutting edges slide on one another so that they touch at point (the cutting point).
When the scissors close, the cutting point moves out from the common pivot point of the scissors in the direction toward the tip of the scissors.
In this process, the opening angle of the scissors, that is, the angle of the cutting edges converging on one another, also changes.
Filament-like material to be cut, such as hair, depending on the opening angle, edge sharpness, and so forth, slides more or less far in front of the actual cutting point until it begins to be cut, is held, and then severed. Since in this cutting method, the material to be cut does not execute a defined rolling motion about its longitudinal axis, necessarily only a partial cross section of the material to be cut is actually cut, while the rest is virtually pinched off or torn off.
Poorly cut hair is finally the starting point for subsequent damage and can cause splitting, among other effects.
The object of the invention is to cut filamentary material to be cut, especially hair, uniformly over its circumference and cross section without any zones of pinching and tearing.
According to the invention this object is attained by a scissors comprising two shanks pivotally connected to each other at a pivot joint; respective longitudinally extending blades for cutting the filamentary material attached to a corresponding shanks and means for vibrating at least one blade in the longitudinal direction, which comprises an electrically powered vibrator. Accordingly, at least one shank can be made to vibrate parallel to the longitudinal direction of this shank by means of the electrically powered vibrator.
The invention has the advantage that filamentary material to be cut, in particular hair, can be cut uniformly over its circumference and cross section without pinching and tearing zones. With the scissors of the invention, the hair slides between the cutting edges while it is being cut through. In the process it is reliably and uniformly severed. When the scissors are closed, the axially oscillating motion component that is additionally superimposed on at least one cutting edge leads to improved cutting properties.
Further advantageous features of the invention are described hereinbelow.
Good cutting results are attained if the vibrator includes a piezoelectric travel transducer, which is located between the blade and an end of the shank toward the handle, and connects the blade and the end of the shank. The oscillating motion is determined by the frequency and amplitude at which the piezoelectric travel transducer vibrates.
The oscillating motion should be executed at such a high frequency that during normal use of scissors, the hair rolls over its circumference on the cutting edges at least once during the cutting operation.
The amplitude of the vibration depends on the circumference of the hair. The initial amplitude value can be approximately 100 to 200 xcexcm.
If both cutting edges vibrate simultaneously with phase-offset from one another, then half the amplitude suffices.
A system with adjustable amplitude and frequency for different material to be cut is thus possible.
The piezoelectric travel transducer can be operated at an ultrasonic frequency. It is integrated into at least one cutting edge. In a manner analogous to an ultrasonic cleaning sonotrode or a welding sonotrode, the longitudinal wave is transmitted along the cutting edge. The vibration generator, which in the final analysis is mechanical, may be disposed on the side of the cutting edge or strut of the scissors. If on the side of the strut, corresponding mechanical play at the bearing point would have to be considered. This applies equally to other vibrators on the strut.
The system is triggered electrically by an ultrasonic generator, which is coupled via electrical connecting cords to the electromechanical vibrator.
Good cutting results are also attained if, as the vibrator, an eccentric washer that surrounds the nail of the joint is provided; if the eccentric washer is inserted into a round recess in the shank and is rotatably joined to the nail; and if a miniature motor is provided for rotating the eccentric washer about the nail. To that end, a standard connecting nail is replaced with an electromechanically driven eccentric unit. The axial component of the eccentric motion leads to the desired cutting motion. As the drive for the eccentric unit, a miniature motor is sufficient and has the advantage of not making the scissors harder to manipulate.
The vibrator can also be embodied such that the shank at least in some regions comprises a magnetostrictive material, and a rigid, stationary exciter coil is wrapped around this material. The cutting edges of the scissors are mounted here on a base body of magnetostrictive material. By applying an electromagnetic field to the magnetostrictive material, a change in length of the material and finally an oscillation of the cutting edges relative to one another are brought about. The exciter coils may be disposed in the strut region of the scissors. The exciter coil is connected to a generator via an electric connecting cord.
Nickel or a nickel alloy is suitable as the material. First, nickel has the required magnetostrictive properties, and second, nickel steel is very highly suitable for manufacturing scissors. To prevent contact allergies, the material may have a plastic coating.

Scissors for cutting filamentary material, especially hair, uniformly without pinching or tearing


A current-modulation method of transmitting high voltage direct current (HVDC) power over a transmission system comprising at least three conductors, wherein each conductor has a nominal thermal limit to its current-carrying capacity. The method involves transmitting DC current over at least one conductor at a level which can exceed each such conductor""s nominal thermally-limited current-carrying capacity, returning the transmitted current over a quantity of conductors greater than the quantity used to transmit at the higher level, so that each return current is less than the transmitted current, and periodically switching the current level in the conductors so as to rotate the higher level current among at least two of the conductors, such that, over time, the resistance heating of the conductors does not exceed any conductors"" thermal limit.

This invention relates to current modulation of direct current transmission lines.
In utility, industrial, commercial, marine, and military power systems Alternating Current (AC) supply lines have intrinsic limits to the amount of power they can transfer from source to load. That limit is proportional to both voltage and current, voltage being limited by the insulation provided, the current by the thermal limit of conductors. It is not unusual for power demand to outgrow either the capacity or the reliability limits of the transmission system already in place, both circumstances being addressed by the invention. While not limited to high voltage electric power transmission lines, the invention will be illustrated in that context.
Line loading on large AC power systems varies according to demand but seldom reaches the thermal maximum of the conductors. Actual transfer limits are more often set by characteristics of the electrical network of which a line is a part than by the thermal limitations of its conductors. Beyond a certain level of transfer; (1) synchronism of the AC system may be jeopardized (2) voltages may become depressed or unstable or (3) the inadvertent loss of the line in question could not be accommodated by other lines on the system. Furthermore the flow on an AC line cannot easily be controlled independent of flow on other lines in the system. For example when the thermal limit is reached on the weaker of two parallel AC lines, the stronger cannot be independently controlled to carry its maximum.
There are a number of AC equipment options, well described in the technical literature, that can overcome some or all of the system limitations to flow on a particular line. They include series compensation, phase shifting transformers, and other options, sometimes enhanced by thyrister controls. Such recourses, to the extent they are effective, are less expensive than construction of additional lines where that is even a practical option.
Present trends in many countries exacerbate the system-based limitations on AC line transfers, particularly those which interconnect major system segments. Growth in the ratio of intra-regional generating capacity to inter-regional transmission capacity may eventually threaten stable operation. Furthermore power brokering, now a common practice in the new generation market place is made difficult on AC systems since contracts must specify or infer a path over which the power is to flow even though it is difficult on an AC system to control the actual route of flow.
High Voltage Direct Current (HVDC) transmission overcomes many of the above limitations. It is possible, for example, to insert an AC/DC/AC (Back-to-Back) converter at one end of an AC line, thus operating the line at AC but gaining the power control advantages of DC. That option can usually bring the line""s maximum loading up to the thermal limit of conductors, thus making full use of the line investment. However by leaving the line itself as an AC medium of transfer, back-to-back schemes forfeit the advantage HVDC has in its ability to make more efficient use of overhead or cable insulation. Insulation on AC systems is dimensioned to accommodate the peak of a sinusoidal voltage wave, even though the voltage is lower during other parts of the cycle. HVDC uses the insulation constantly and does not require as high an allowance for surges. The product of these two factors alone can boost transfer capacity by a factor from 2 to as much as 2, depending on insulation conditions.
In addition to improved transfer ability due to physical attributes of the line or cable, transfers on an HVDC lines have far fewer system-imposed limitations. Thus where there is a demand for more transfer, it is easier for an HVDC line to operate up to the thermal limits of the conductors. Being controllable, HVDC is also much more compatible with modern power brokering practices.
HVDC is inherently more reliable than AC, primarily because the loss of one conductor on an AC line forces the whole line out of service. Operation with two of three phases in service is not possible. Bipolar HVDC lines, equipped with metallic ground return, can loose one conductor and still operate at half power.
It is for the above reason that the industry contemplates conversion of selected existing AC lines to HVDC. The primary barrier to that recourse is economic. To convert an AC line to DC, all of the transmitted power must pass through an AC/DC inverter at one terminal and a DC/AC converter at the other. Thus even if the conversion achieves no increase in power level, the full cost of the conversion equipment must be justified by operational advantages of HVDC. On the other hand if system-imposed limitations allow the AC line to operate at only half its thermal limit and HVDC conversion allows loading to be brought to that limit, the conversion, while sized for full capacity, can be written off over the incremental one half of full capacity achieved.
In the case of some underground or underwater cables there are technical limits to HVDC conversion as well. Paper insulated cables are judged to be suitable for either AC or DC, thus delivering the advantages cited above. But cables with solid insulation, e.g. cross-linked polyethylene have two problems when used for DC. Over a period of time a static electrical charge builds up in the solid insulation which, upon reversal of power flow, achieved by most systems through a sudden reversal of polarity, can almost double the local electrical gradient in the insulation causing a risk of failure. Additionally, continuous DC systems applied to solid cable there is tendency for impurities to migrate in the insulation causing a weakened insulation path. Both problems are ameliorated this invention.
A double-circuit AC line, having two three-phase circuits on one structure (six conductor positions), is easily adapted to bipolar DC since it can be converted into three independent 2-pole circuits or into a single 2-pole circuit with three parallel conductors for each pole, thus making full use of the conductivity available.
The odd number of phase positions (3) on a single circuit AC line means that only two phase positions can be fully used, the third serving as an emergency ground should one normal pole be out of service. Thus whatever per-conductor advantages are achievable in the double circuit case, are penalized by a factor of ⅔ in the single circuit case Normally this would render the thermal limit of single circuit AC lines, converted to DC, about the same as the prior AC limit.
The same arguments apply to underground cables where, in the case of a single three-phase cable, one third of the inherent conductivity would be left unused under normal conditions.
Conductor xe2x80x9cthermal limitxe2x80x9d in the ensuing explanation is simplified as though it corresponded to a fixed ampere limit. Actual temperature rise of bare conductors depends not only on conductor characteristics but a number of environmental factors including, ambient temperature, sun exposure, and the magnitude and direction of wind. Technical literature provides details of these effects for specific conductors and current levels. The effects of high conductor temperature which depend on the magnitude of current, its duration and the cumulative exposure time, include mechanical weakening and embrittlement. To simplify application, most transmission owners use very conservative assumptions and assign a single xe2x80x9cthermal limit,xe2x80x9d in amperes, which is applied irrespective of actual conditions. Some assign two or more such values, each depending on conditions. Some actively monitor conditions and set the limits to correspond more closely to actual conditions. It will be apparent that any of the foregoing approaches would adapt equally well to implementation of the invention as they do to operation of the AC line.
Heating of a conductor is proportional to the square of current flowing through it and directly proportional to its electrical resistance. The electrical resistance of a particular conductor to DC current depends on the metal it uses, the configuration of conductor strands, and other design factors. When the same conductors is subject to an AC current, electric fields within the conductor tend to distort the internal current distribution, forcing more current to the outer edges, thus effectively reducing the useful conductor cross section. This (xe2x80x9cskin effectxe2x80x9d) increases AC resistance. The AC/DC resistance ratio can range from roughly 1.01 to as much as 1.10 depending on conductor characteristics. Thus any given conductor can, for the same temperature rise, carry a higher DC than AC current.
The current carried by overhead conductors, and most electrical equipment must be limited to levels where the equilibrium between the heat generated by that current and heat loss from cooling leaves the component at a temperature which will not damage it. That requirement notwithstanding, the current through conductors or any other system component can exceed the maximum continuously sustainable level (termed herein the xe2x80x9cnominal thermally limited current-carrying capacityxe2x80x9d) if (1) the component is already below its maximum temperature, (2) such excessive current is compensated for by periods of lower current and (3) the time constant of the variations in current is short compared to the thermal time-constant of the component effected. This, in fact, is the basis for root-mean-square current ratings of all AC equipment. The period of variation in heat generation (current squared) for 60 Hz systems is approximately 8 millisecondsxe2x80x94exceedingly short compared to thermal time constants of power system lines and equipment components. Recognizing that those time constants are measured in minutes (for most cables in tens of minutes), lines and equipment can sustain high and low variations in heat generation over time periods orders of magnitude greater than they see at 60 Hz operation.
The invention modulates current magnitudes so that (1) the current is assigned a high value for a period of time, then a low value for a period of time such that the average heating effect is the same as a constant current of intermediate value and (2) the higher value is rotated among conductors so as to distribute the heating effect equally among them, thus using all of their inherent thermal capability. The invention, as embodied in the context of a single circuit three-phase transmission line, would cause one (the xe2x80x9cburdenedxe2x80x9d) phase position to carry a higher than normal current, ib which may be in excess of the conductor""s thermal limit while the return (xe2x80x9crecoveryxe2x80x9d) currents, ir, whose sum is equal and opposite to ib, return on the other two phase positions. This regime is continued for a time interval, T, after which a thyrister bridge configuration assigns another phase position the value ib, likewise reassigning the recovery currents. Thus the net thermal burden on each phase position and its attendant terminal equipment is within limits assigned to both conductors and equipment components. In any given embodiment of the invention T may be assigned a value consistent with and shorter than the thermal time constant of the most sensitive component in the current path or to address other effects that continuous DC voltage has on equipment or the environment.
Examples of current modulation implementing this invention on a single circuit AC line converted to DC are illustrated in FIG. 1. FIG. 1a shows symmetrical modulation in which, again for purposes of illustration, ib is assigned a value of 1.5, and the two equal recovery currents, ir, have values of xe2x88x920.75. Thus the average DC current in each phase position is 1.0. FIG. 1b shows an example of asymmetrical modulation using the same respective values of ib and ir, but in sequence such that phase position 1 is always positive. The invention is not limited to any particular modulation regime or to regimes where the time periods, 1, 2, and 3 are equal. It applies to any sequence of current system of current modulation where (1) the sum of transmitted and return currents is always zero and (2) the DC current overload burden rotates among one or more phases or wires, the others recovering thermally from their overload duty.
The modulations shown in FIG. 1 are shown as an abrupt transition from one current level to another. It is apparent that the transition can be ramped or softened to minimize harmonic generation or to reduce the stress on insulation or equipment. The change from positive to negative could, for example, emulate the positive to negative peak variation on a cycle of power frequency voltage.
The 1.5 value in the foregoing example, while useful in illustrating the principle introduced by the invention, is slightly optimistic since, in a practical case, the over-current, ib would have to be adjusted so that the average heating of the conductor would be the same as if the current were constant at a value of 1.0. That limit would require that average value of ib2 rather than ib over each of the three time intervals equal 1.0, the loss that would have occurred over those time intervals with normal current. Solving the equation:
[ib2+2xc3x97(xe2x88x92ib/2)2]/3=1xe2x80x83xe2x80x83(1)
shows that ib would have to be equal to {square root over (2)} or 1.414. Thus an over-current of 1.414 for one third of the time combined with a current of 0.707 for two thirds of the time would generate the same conductor heat as would a constant current of 1.
An example calculation will help illustrate the improvement the invention brings to reliability of a single-circuit AC line converted to DC. Assume that the AC line is operating at unity power factor so that the total AC power is equal to three times the product of phase-to-ground voltage VI-g and the phase current, IAC, i.e.
PAC=3xc3x97VI-gxc3x97IAC=3puxe2x80x83xe2x80x83(2)
On conversion to DC the effective voltage could be increased by a factor, kv, the product of {square root over (2)} (the peak-to-rms ratio) and a factor which allows DC to use a somewhat higher voltage for the same insulation level based on DC""s relatively milder demand for accommodation of over-voltage surges. For purposes of example, assume the second of those factors gives a 10% advantage so that:
xe2x80x83VDC=kvxc3x97VAC={square root over (2)}xc3x971.1=1.56xe2x80x83xe2x80x83(3)
Furthermore, the DC current could be increased to benefit from the resistance ratio, RAC/RDC, typically 1.03. Recalling that heat generation is proportionate to current squared:
IDC/IAC={square root over (RAC/R)}DCxc3x971.015xe2x80x83xe2x80x83(4)
Thus for two-pole DC transmission the total power at the conductors"" thermal limits would be:
PDC(2-pole)=2xc3x971.56xc3x971.015=3.16puxe2x80x83xe2x80x83(5)
Or, noting that the thermally limited AC power transfer was 3.0 pu, an increase about 5% over the AC case represented in equation (2).
If one were to achieve the same power per pole in the modulated case as characterized the 2-pole case, maximum current would have to be increased by a factor of 1.5 so that average power per pole would again be 1 pu. However as stated in equation (1), thermal limits require that the maximum current be 2 rather than 1.5 so that maximum power will be diminished proportionately. In that case:
PDC(modulated)=({square root over (2/)}1.5)xc3x973xc3x971.56xc3x971.015=4.46xe2x80x83xe2x80x83(6)
Or, in this case, almost 50% more than the AC limit described in equation (2)
Equation (6) illustrates the case where current modulation is used to achieve maximum power per pole. If the same total power is transmitted in the modulated case as would be in a bipolar case, then the ratio of losses in the modulated case to the bipolar case would be proportional to the sum of the squares of currents over a representative time period in the two cases or:
xe2x80x83(12+xc2xd2++xc2xd2)/(12+12)=1.5/2=0.75xe2x80x83xe2x80x83(7)
Thus by dividing the return current between two return paths instead of one, the invention reduces losses, as a percent of power transmitted, by 25%.
The actual advantage of conversion to HVDC is usually much greater than indicated by equations (5) and (6). The latter imply that the AC line, prior to conversion, is already loaded to its thermal limit. System characteristics usually limit the loading of AC lines to well below that limit. Thus the advantages shown in equations (5) and (6) should be multiplied by the ratio of the AC thermally limited transfer to the system-limited transfer level. It is not unusual for that ratio to exceed 1.5.
The above data, normalized to set thermally limited AC power equal 1, is shown in Table 1. The table also shows the effect on each transfer limit of an outage of one phase position.
Even with one phase position out of service the current modulated configuration transmits the same amount of power as the 2-pole configuration since the bridges would revert to 2-pole unmodulated system under those circumstances. Neither the original AC line nor the same line terminated in a back-to-back converter can transmit any power when one phase is out of service.
It is important to the understanding of the invention to realize that at all times the single circuit, thee conductor line is functioning as a 2-pole line with a split return path. Thus all of the converter and control technology developed over the history of modem HVDC is as applicable to lines using the invention as it is to lines built to operate as HVDC lines or converted from AC with other schemes for using the phase wires. Examples of the many systems capable of being accommodated by the invention include those described by U.S. Pat. Nos. 5,910,888 and 4941,079.
In a like sense, transmission lines which implement the invention, could function as continuous bipolar DC so long as the transfer demand can be satisfied with two active conductors, reverting to modulation only when the thermal capacity of the third conductor is needed.
The invention applies to underground or underwater cables as well as overhead lines. In the cable case the incentive for increasing loading is often higher since the investment in the transmission medium is greater and is correspondingly more expensive to augment. The technical limitations which prevent use of AC-designed solid insulation cable for traditional versions of DC are also overcome by the invention. By adjusting T to an appropriate value, (probably several minutes) and causing the transition from one polarity to another to be gradual, e.g. emulating a portion of a 50 Hz or 60 Hz sine wave, charge no more opportunity to build up than with AC energization, nor does the modulated voltage wave form provide the long-term constant voltage condition which causes migration of impurities.
At least two related benefits will accrue to overhead lines embodying the invention. On bipolar HVDC lines, ion clouds are generated by the constant DC potential. They have long been one of the environmental concerns associated with HVDC application. By alternating the reversals of polarity at relatively short intervals, a concomitant of current modulation, the invention will mitigate ion cloud generation in the same sense as do AC electric fields. More importantly, HVDC lines using existing transmission systems require additional insulation because constant DC fields surrounding the insulators attract particles from the air which eventually coat the insulator surface. The problem does not occur with AC since the field is constantly reversing. Even though it is a form of DC, the invention will lessen the accumulation of particles by periodic reversal of electric field, thus making it more likely that existing AC lines can be converted to DC without replacement of insulator strings.
The invention has been described as it pertains to large electric power systems. It will be apparent that the invention also applies to power delivery systems at any voltage level and frequency where (a) there is a need for greater power transfer using an existing multi-conductor medium and/or (b) the control advantages of direct current enhance operation of the system and/or (c) direct current, as a transmission medium has advantages, e.g. the absence of induced voltages in parallel circuits and/or (d) improved reliability is desired. With respect to the reliability advantage, it is apparent that the invention has two very desirable general characteristics.
1. It provides a high degree of redundancy by distributing the transmission burden over multiple conductors such that the loss of any one will have less impact on the total delivered power.
2. It constantly uses all conductors rather than holding some in reserve whose failure would not be detected until they were called on for service.
Thus it could be embodied in a system with an even number of conductors, e.g. a double circuit AC transmission line. In that case a simple two-pole conversion would require either that (1) one phase position be devoted to an emergency ground return, leaving only four useful conductors for DC transmission or that no emergency ground return be provided in which case an outage of one conductor would cause a third of the transfer capability to be lost. In the later case the invention would limit power the impact of power loss to one sixth rather than one third of the pre-outage total. It would also allow full utilization of one circuit, converted to DC, while the other remained at AC either as a staging strategy or in a case where both AC and DC ties were of value.
This invention features a current-modulation method of transmitting high voltage direct current (HVDC) power over a transmission system comprising at least three conductors, wherein each conductor has a nominal thermal limit to its current-carrying capacity, the method comprising transmitting DC current over at least one conductor at a high level which may exceed each such conductor""s nominal thermally-limited current-carrying capacity, returning the transmitted current over a number of conductors greater than the number used to transmit at the higher level, so that each return current is less than the transmitted current, and periodically switching the current level in the conductors so as to rotate the high level current among at least two of the conductors, such that, over time, the resistance heating of the conductors does not exceed any conductors"" thermal limits.
Preferably, for any conductor, the average of the square of each level of DC current multiplied by the time to which it carries that current is such as to ensure that the heating of that conductor does not exceed its thermal limits. The sum of currents in all conductors carrying the high current level is preferably equal and opposite to the sum of currents in conductors carrying the lower current level. The current flow in one or more conductors may be always in the same direction. The current flow in one or more of the return conductors may switch directions. In this case, the levels of higher current and lower current may be rotated among conductors such that the fraction of time which each conductor experiences each level of currents is such that no conductor is overheated. The current levels and the time during which each conductor is subjected to each current level may be such that no conductor""s thermal limit is exceeded. The method may further comprise converting AC to DC before transmission, and converting DC to AC after transmission. This conversion may be accomplished using converter and inverter bridges of many configurations. The switching may be accomplished by control of the valves comprising those converters and inverters.

Current modulation of direct current transmission lines


The invention concerns a grinding spindle, comprising a spindle housing and two coaxial shafts which are driven by a drive motor. A concentric grinding disk is fixed to each of said shafts. The shafts can be moved in an axial direction in relation to each other with a lifting or lowering movement in order to engage one grinding disk or the other. The inner shaft is connected to the drive motor as a main shaft (1), the outer shaft (8) is coupled to said main shaft (1) by a carrier device (10). In addition, a bush (4) is coaxially semimounted on the spindle housing (3), the outer shaft (8) is pivotably mounted on the bush (4) with a pivot bearing (9), and the bush (4) is provided with an actuator (13) which executes the lifting or lowering movement.

1. Technical Field of the Invention
The invention concerns a grinding spindle, comprising a spindle housing and two coaxial shafts which are driven by a drive motor. A concentric grinding disk is fixed to each of said shafts. The shafts can be moved in an axial direction in relation to each other with a lifting or lowering movement in order to engage one grinding disk or the other.
2. Description of the Prior Art
When the surfaces of flat work pieces are worked, which may, for example, comprise wood, metal, stone, ceramic or also semiconductor material, and for which high requirements must be fulfilled in respect of the surface quality, grinding technology, especially surface grinders, can be used advantageously. To that end, a rotating, multicut cutting tool is used, for example, a grinding disk mounted on a rotating grinding spindle, which is fitted with an abrasive layer comprising bonded grains, for example, a cup grinding wheel with ring-shaped contact surface. An axial feed movement of the rotating grinding tool, generally of the total grinding spindle, brings the grains of the abrasive layer to bear on the surface of the work piece, which results in a removal of material. The use of a fully sintered grinding wheel is also possible. An additional linear or circular feed of the work piece ensures the even working of the total surface of the work piece.
To attain a high work piece surface quality, generally a multi-step, frequently two-step, machining process is applied, where first a coarse-grained grinding disk with a high cutting performance (coarse or rough grinding disk) removes the bulk of the material. The still relatively coarse surface obtained is postprocessed in a subsequent, further work step using a fine-grained grinding disk (fine or finishing grinding disk), which although it only removes a small amount of material achieves a good surface. If both work steps are carried out using the same grinding spindle, it is appropriate to use a grinding spindle which is provided with two grinding disks, each with a different grain size, which can engage selectively with the surface of the work piece. This allows the disadvantages to be avoided which otherwise prevail when grinding tools are changed, such as the time required to reset and the necessary new profiling of the grinding disk owing to the non excludable imprecise fitting, which requires time and leads to a high consumption of abrasive materials. From the state-of-the-art, a grinding spindle of the generic concept is known, for example, (DE-PS 846 663), which has two concentric cup grinding disks carried on two shafts disposed coaxially in a single spindle. The outer shaft is rotated by a motor, while the inner shaft is also moved by means of a carrier device. Thereby, the inner cup grinding disk is disposed in the grinding spindle so as to be moveable axially. Thus selectively the inner or the outer cup grinding disk can be brought to engage, without needing additional resetting or profiling time. A further grinding spindle of the class mentioned at the beginning (DE-PS 42 08 615) uses two cup grinding disks whose abrasive layers comprise uninterrupted ring segments with the same diameter, which engage with one another so that they essentially form one ring and can selectively engage the work piece surface. With this arrangement, both grinding disks function on an identical working radius, which is especially advantageous for the rotary grinding technique, where the feed function of the work piece comprises rotation about an axis extending essentially parallel to the grinding spindle and through the grinding disk abrasive layer. Therefore, different working radiuses of the two grinding disks mean disadvantageously that for the coarse and fine working of identical parts of the work pieces surface a repositioning of the work piece between the two work steps is necessary.
With precision work, for example, the grinding and polishing of silicon wafers, whose breaking strength is determined by their surface quality, sufficient rigidity of the used spindle in the radial direction is of decisive importance, because with a lack of rigidity axial loads upon the spindle can trigger radial oscillations, which can impair the resulting surface quality of the wafer and possibly form grooves, which may provide a predetermined breaking point for the single crystal. To increase the radial rigidity, in the state-of-the-art, the diameter of the spindle is increased, which, however, is only possible in a limited scope. Especially in the case of spindles with an integrated electric motor, where the stator is mounted in the spindle housing and the moved rotor is attached with the outer side to the outer shaft, the diameter of the inner and outer shaft is limited by the space available inside the electric motor. Especially in the case of small grinding spindles, therefore, the necessary radial rigidity cannot be achieved needed for precision work.
Against this background, it is the object of this invention to create a grinding spindle which can engage two different grinding disks selectively with the work piece and which even when compact in design provides sufficient radial rigidity to fulfil all existing requirements during precision working, such as, for instance, those required when grinding silicon wafers.
In accordance with the invention this task is solved therein that the inner shaft is connected to the drive motor as the main shaft, while the outer shaft is coupled to the main shaft by a carrier device. In addition, a bush is coaxially semimounted on the spindle housing, the outer shaft is pivotably mounted on the bush with a pivot bearing and the bush is provided with an actuator which executes the lifting or lowering movement.
The underlying idea of the present invention is to connect the inner shaft to the drive motor as the main shaft, and to fix the outer shaft which is coupled to the main shaft by means of a suitable carrier device, for example, a carrier pin, so that it rotates together with the main shaft, to the outer side of the spindle housing. To that end, a bush is coaxially semimounted on the spindle housing, the outer shaft is pivotably mounted on the bush with a pivot bearing. For the selective engagement of the grinding disks mounted on the inner and the outer shaft with the work piece, the bush is provided with an actuator which executes the necessary axial lifting or lowering movement Thereby, the grinding disk of the outer shaft can be moved, by means of a lowering movement, below the level of the grinding disk of the inner positioned main shaft and can thus engage with the work piece surface. The lifting movement in the opposite direction of the outer shaft allows the grinding disk of the main shaft to again appear below its counterpart so that it can engage the work piece surface. The advantage of this design of a grinding spindle lies especially in the significant increase in the diameter of the outer shaft and the resulting substantially higher radial rigidity.
Simultaneously, space is acquired inside the grinding spindle for an increase in the diameter of the inside shaft, which also acquires further radial rigidity. Overall, therefore, a grinding spindle is obtained, which enables the successive working of the work piece surface with two different grinding disks, for example, a coarse and fine grinding disk and which at the same time, even when of compact design, owing to the large diameter of the shafts carrying the grinding disks, is stable against radial oscillations and so advantageously can be used especially for precision work.
The drive of the inventive grinding spindle can be realized, for example, by means of a belt pulley fixed coaxially to the main shaft, which drives the drive motor via a suitable belt.
In a preferred inventive embodiment, to drive the grinding spindle, however, an electric motor is used which is integrated in the spindle housing and which penetrates the main shaft. Thereby, for example, the rotating rotor of the electric motor can be attached by the outer side to the inner shaft and the fixed stator can be integrated in the spindle housing. In this way, one obtains a very compact grinding spindle, which does not require exterior drive parts for its rotary actuation. Motors driven hydraulically or by compressed air can also be considered for the drive of the grinding spindle.
As an actuator for the axial lifting and lowering movement of the outer shaft, preferably a pneumatically driven cylinder is used in conjunction with a return spring. However, hydrostatic, electromagnetic, electromotive or mechanical actuators are for example also conceivable.
To machine a work piece, the grinding spindle must be lowered, or the work piece lifted, until the grinding disk engages the work piece surface. Thereby the problem arises that the distance between the grinding disk and the work piece surface is not known in many cases with sufficient exactness. Therefore, in an inventive development, the grinding disk is equipped with a sensor, which registers the contact of grinding disk and work piece, for example, via the vibrations generated or displacements of the shaft, and emits a signal which stops the movement of the grinding spindle and starts the predefined grinding cycle.
If especially high requirements exist in respect of the surface quality of the work piece, as, for example, may be the case for silicon wafers for use in chip cards, a two-hour working of the surface with a coarser and a finer grinding disk is frequently insufficient so that at least a further working step with an extra fine grinding disk or a polishing cloth is necessary. To also operate in such a case with a single grinding spindle without a time-consuming and costly change of tool, in a further development of the invention, it is proposed to provide the grinding spindle with a further inner shaft disposed coaxially within the main shaft, which can be equipped with a further grinding disk or a polishing cloth as a tool and which can also engage the work piece surface. This inner shaft, owing to its comparatively low diameter, has a low radial rigidity and thus is especially suitable for the polishing process for which high rigidity is not needed. This special embodiment of the inventive grinding spindle can therefore be advantageously used to first pre-grind a work piece surface, then to finish the grinding and finally to polish the work piece in a single machine.
When needed, the inventive grinding spindle can of course have more than one bush coaxially semimounted on the spindle housing to which respectively one shaft provided with a grinding disk is coaxially pivotably mounted in relation to the main shaft and is connected rotationally rigidly to the main shaft via a carrier device. Here, too, the additional grinding disks can also selectively individually engage the work piece surface by means of actuators disposed on the bushes for lifting and lowering movements. In this way, the number of machining and removing processes executable using the inventive grinding spindle can be increased and varied virtually infinitely.
In an especially simple embodiment of the invention, the two or also more grinding disks used comprise concentrically disposed cup grinding disks so that the abrasive layers used form concentric rings. Here, the abrasive layer of the inner grinding disk can also be embodied in the form of a circular disk, which, depending on the embodiment of the grinding spindle, is surrounded by the other abrasive layer as a concentric circular ring or by the other abrasive layers as concentric circular rings with possibly different working radiuses. With different working radiuses, different groove ring diameters and groove depths can also be cut.
When the inventive grinding spindle is to be used for the technique of rotary grinding, identical working radiuses of the used grinding disks are highly advantageous. For that purpose, the inventor recommends configuring the grinding disks used as cup grinding disks with an identical working radius whose abrasive layers have the form of uninterrupted circular rings whose segments engage one another and complement one another to form one circular ring. With this special embodiment of the grinding disks, the inventive grinding spindle can also be advantageously used for rotary grinding. Of course, any combination of grinding disks with the same and different working radiuses is conceivable.
During the grinding process, the work piece is ordinarily cooled. For that purpose, the inventor recommends providing the outer shaft or the additional inner shaft of the grinding spindle with a continuous axial bore by means of which a suitable coolant can be supplied to the machining process.
When it is necessary, to achieve the required quality of a work piece surface, to use more grinding disks than can be suitably disposed on a single grinding disk, the inventor recommends providing a grinding system with at least two inventive grinding spindles. Thus even multi-step machining processes can be carried out advantageously without the disadvantages associated with tool changes such as long setting-up times and the necessity of re-profiling the grinding disk, whereby the high radial rigidity of the grinding spindles used allows high precision work piece surfaces to be achieved.