text:
The present invention relates to a sling, methods of making and using a sling, and kits comprising a sling for treating urinary incontinence. The sling has multiple elongation properties that serve to improve the support of the urethra. The sling may comprise a coated material adapted for urethral suspension. The coated sling has properties that appear to enhance the sling elongation characteristics. The coated sling further includes properties that reduce its susceptibility to bacterial infections. The sling further includes properties to enhance the proper tensioning of the sling.
1. A method of treating urinary incontinence with a sling device, comprising:
providing a multi-zone elongate mesh sling having first and second end portions and a central portion, wherein at least a coated portion of the sling includes a coating material impregnated with a medicament, the coating material applied such that the longitudinal elongation properties of the coated portion of the sling is reduced;
inserting the elongate mesh sling into a patient;
positioning the central portion of the elongate mesh sling under the patient's urethra; and
adjusting the elongate mesh sling such that the central portion supports the urethra.
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9. A method of treating incontinence with a sling device, comprising:
providing an elongate mesh sling having first and second elongate end portions and a support portion, with the first elongate end portion defining a first zone, the second elongate end portion defining a second zone and the support portion defining a third zone, wherein at least one of the first, second and third zones includes a coating material including a medicament, the coating material applied such that the longitudinal elongation properties of the coated portion of the sling is reduced;
inserting the elongate mesh sling into a patient;
positioning the support portion of the elongate mesh sling under the patient's urethra; and
adjusting the elongate mesh sling such that the support portion improves support of the urethra.
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This is a divisional of U.S. patent application Ser. No. 09/939,098, filed on Aug. 24, 2001 now U.S. Pat. No. 7,025,063. The present application also claims priority to 60/230,647 filed Sep. 7, 2000, all of which are fully incorporated herein by reference.
The present invention generally relates to the repair of tissue defects in a patient, including such defects as hernia. The present invention specifically relates to devices and methods in the long-term cure of recurrent female urinary incontinence. More particularly, the present invention relates to slings for use in treating female urinary incontinence and methods of making and using the slings.
Normal urination and continence is dependent upon normal function of the urinary tract, kidneys and nervous system. In addition, in women, continence requires correct coaptation and urethral support. Specifically, in order for continence to be maintained, the urethra must be supported and stabilized in its normal anatomic position behind the pubic bone, adjacent to the vaginal wall. The natural support system for the female urethra is a layer of support composed of pelvic and vaginal wall tissue and ligaments, which attach to the pubic bone. Relaxation, weakening or loss of this support system results in hypermobility of the urethra and bladder to an unnaturally low position within the pelvis. This defect contributes to about 30% of incontinence in women.
One form of incontinence, referred to as stress incontinence, is an involuntary loss of urine that occurs with increased abdominal pressure such as with coughing, sneezing, laughing, or lifting. Urethral hypermobility may be a result of pregnancy (one reason why stress incontinence is common in women who have had multiple pregnancies), or may be due to pelvic prolapse. In pelvic prolapse, there is a protrusion or falling of the bladder, urethra, or rectal wall into the woman's vaginal space. Additionally, in women with low estrogen levels such as in post-menopausal females, stress incontinence is more likely to occur due to decreased vaginal muscle tone resulting from the loss of estrogen.
Approaches for treating female urinary incontinence vary and include methods directed at elevating the urethra or the bladder neck (upper region of the urethra) to return it to its normal anatomical position behind the pubic bone. These methods include needle suspension procedures and sling procedures. The needle suspension procedure is a commonly used procedure which involves placement of sutures in the support tissue (fascia) on either side of the displaced urethra and attaching these sutures to fixed sites such as bone and soft tissue. Therefore, a variety of devices have been developed to aid in the fixed attachment of the sutures to the support structures. A disadvantage with this approach, however, is that the tissue support structures being used for the urethra are themselves stretched or otherwise deficient, thereby, making them inefficient as support structures and a less effective solution.
Another approach for treating female incontinence is the sling procedure. In this procedure a sling is formed by taking a piece of human abdominal tissue (fascia) or a piece of synthetic material and using this as a platform to provide support and/or restore the urethra to its normal retropubic position. Slings made of biological tissue require either growing or harvesting autologous tissue or using processed cadaveric tissue. Therefore, these types of sling materials are sometimes undesirable in that they increase the expense, surgeon's time required and complexity of the procedure.
As an alternative to human tissue, prefabricated or synthetic slings have been developed for use in treating incontinence and are described, for example, in U.S. Pat. No. 6,042,534. These slings are said to offer improvements to the sling procedure for treating incontinence in that the synthetic slings are supplied to the physician in shapes and dimensions adapted for urethral stabilization. This eliminates the need for sizing of the sling material by the surgeon during surgery, which greatly reduces the time required for the surgical procedure.
Another example of a synthetic sling and system for use in treating incontinence is described in U.S. Pat. No. 6,039,686 issued Mar. 21, 2000 to Kovac. The sling system of Kovac involves stabilizing the urethra using a mesh sling having an innovative mesh suturing pattern that is secured in vivo by short sutures attached to the posterior/inferior (lower, back) portion of the pubic bone instead of the superior (upper) portion of the pubic bone as with other methods.
The tissue and mesh used in prior slings can be fabricated or obtained from a variety of materials and sources. There does not appear to be any attention given to configuring, creating or modifying these slings in a manner to provide optimal elongation characteristics to the support tissue. Particular elongation properties are desirable in some circumstances, such as when the amount of tension or support at the region immediately surrounding the bladder neck of the urethra is important.
Tissue ingrowth, infection resistance and capacity to erode surrounding tissue are also factors in sling designs. The specific effect of the elasticity of the sling on these factors is not known in great detail.
In view of the above, although improvements in surgical treatment of urinary incontinence have been made, there is a need to provide even more improved sling systems so as to further enhance reliability and to better respond to patient kinetics.
In view of the foregoing, it is an object of the present invention to provide a surgical sling that addresses the limitations and disadvantages associated with prior devices and systems, yet meets the needs of the user.
A further object of the invention is to provide a sling apparatus having distinct elongation properties along its length and its width and that minimizes the complexities of the placement procedure for the surgeon.
A further object of the invention is to provide a surgical sling fabricated such that it has one elongation property in one direction and a second elongation property in a second direction.
An additional object of the invention is to provide a coating to a sling material that contributes to appropriate elongation property, improves biocompatibility and inhibits or resists infection.
An additional object of the invention is to provide a method of making and using a multiple elongation sling system for treatment of urinary incontinence. The system can include a surgical sling having several distinct elongation properties and adapted to be passed under the urethra for supporting the urethra in its normal anatomic position. When inserted into a patient, the sling can also prevent abnormal urethral descent in a patient.
An additional object of the invention is to provide a sling material made from a mesh wherein the mesh is coated but contains open holes or pores to promote tissue in-growth.
An additional object of the invention is to provide a sling material that provides visual indicia to the user that is indicative of a particular tensioned state of the sling material.
The present invention includes coated slings and slings having certain physical and biologic characteristics that increase the overall effectiveness and comfort of the sling once implanted in vivo. Such systems also include slings that provide visual indicia to the user indicating when the sling has been manipulated into a desired state, e.g., into a desired tension.
The present invention provides efficient and reliable slings for use in treating males and females. The sling is particularly suitable for pelvic floor reconstruction surgery and for treating urinary incontinence. The features of the invention as described herein provide a surgical sling having at least two different elongation characteristics along its surface area. In addition, the slings may be coated with, for example, a silicone coating. Such coating is believed to contribute to the desired elongation properties of the mesh, assist with ensuring biocompatibility, and provide a carrier for anti-microbial agents.
Referring to
Materials suitable for use in fabricating the coated slings of the present invention include man-made materials such as filamentous mesh materials. Filamentous mesh materials include synthetic fibers such as polyester, polyurethane, nylon, or polypropylene which can be woven or braided to form a mesh 12. The filaments in such materials may be oriented in a single direction or may be multidirectional.
As will be further described below, the pattern formed by the weave can be designed so as to provide a mesh material having directionally oriented elongation properties. In a preferred embodiment of the present invention, the mesh material comprises a weave pattern where the holes 24 have a diamond shape. As would be apparent to one skilled in the art, the degree of "stretch" or elongation properties in either direction of the mesh pattern can be adjusted as preferred by a user by altering the weave of the mesh material.
In a preferred embodiment, a synthetic filamentous material suitable for fabricating a mesh for use as a sling include a commercially available material comprised of a Rashel knit mesh made from 150 denier polyester yarn. Such a mesh has a hole size of approximately 1/32″ (0.794 mm) and a weight of approximately 4.7 oz/yd. (133.25 gr/.914 m). The yarn is a multi-filament yarn. In another embodiment a mesh known as Mersilene™ may be used.
The weave of the mesh according to one aspect of the invention is such that it has greater elongation properties in one direction 20 than it does in a second direction 22 transverse (or perpendicular) to the first direction 20.
In a preferred embodiment wherein the mesh is cut in a rectangular, sling-like configuration, the elongation properties of the mesh in the longitudinal direction are such that the mesh will elongate in the range of about 24%-28% beyond its normal state when placed in tension by a 20 lb. (9.072 kg) load. The elongation properties in a direction transverse (i.e., perpendicular) to the longitudinal direction, that is, in the latitudinal direction, are such that the mesh will elongate in the range of about 65% -75% beyond its normal state when placed in tension by a 20 lb. (9.072 kg) load.
By virtue of the longitudinal direction having lesser elongation properties than the latitudinal direction, there is less tendency for the longitudinal edges of the sling to curl in on themselves when the sling is in tension along the longitudinal direction. This is a desired property along the longitudinal direction of the mesh insofar as an implanted sling that becomes curled in this manner can be more prone to cause tissue irritation and ultimately tissue erosion in the patient.
Conversely, by virtue of the latitudinal direction of the mesh sling having greater elongation properties, the sling provides greater flexibility and "give" in a direction parallel to the urethra. As a result, the sling can still serve its function of treating incontinence but it does so with less trauma and greater comfort since the sling is now more responsive to patient movements and activities.
These desirable properties of the mesh are particularly acute in sling operations where the sling is attached to the pubic bone at the sling's opposite longitudinal ends. That is, the properties of the invention are best utilized when the sling is attached to opposite sides of the pubic bone and placed in tension along its longitudinal axis. In this manner, elongation is allowed in the longitudinal direction with minimal edge curling while at the same time the elongation is enhanced in the latitudinal direction to promote responsiveness to patient movement. This result is believed to make the sling procedure a more clinically stable procedure that improves patient comfort.
Alternatively, in some surgical procedures, the sling may be placed in the body in a tension free rest position. Even in this tension free rest position, the sling according to the present invention is believed to resist edge curling when anatomical movement (e.g. a stress event such as a cough) places tension on the sling.
As depicted in
As is evident from the figures, the coating is applied in a manner such that the holes or pores 24 of the mesh remain open and clear of silicone. That is, the exposed surfaces within the holes or pores 24 themselves remain open and free of silicone. As a result, a sling is obtained that resists infection (due to the coating) but also promotes tissue in-growth (due to the holes or pores 24).
A synthetic sling fabric material that is coated with a substance such as silicone is also advantageous in that the coating can provide lubricating characteristics to the mesh that enables easier adjustment of the sling during the implantation procedure. Further, the silicone coating creates in the sling a composite structure of the fabric and the silicone that better interacts with the patient's tissue. The silicone also coats the yarn material to the degree that the yarn functions much like a monofilament. Such a monofilament is believed to be less prone to infection. It is also believed to lead to less erosion of the tissue.
A coating such as silicone provides a platform from which therapeutic substances like antibiotics or antimicrobial agents can be introduced to the patient. Such agents can be impregnated into the silicone coating or, alternatively, may be formulated with the composition comprising the silicone coating and applied during the coating procedure. In some embodiments, a silicone coating containing or impregnated with antibiotic agents may contain a drug that is formulated to be time-released. Examples of agents suitable for use include antibiotics and antimycotics such as, gentamicin, fungizone, rifampin or minocycline HCL. Other agents may also be incorporated in the silicone, such as, but not limited to antiseptic agents, radioopaque agents and other antimicrobial agents.
In a preferred embodiment of the invention, the coating of the sling will also impact the dual elongation properties of the sling. For example, the fabric mesh discussed previously, which is later coated with silicone, will result in a mesh that elongates in its longitudinal direction about 19.5%-21.5% beyond its normal state when placed in tension at about 20 lbs. (9.072 kg) of force. Conversely, the mesh elongates in its latitudinal direction about 120%-130% beyond its normal state when placed in tension at about 20 lbs. (9.072 kg) of force. This is a desired result insofar as elongation properties are tending to be enhanced in the latitudinal direction (to provide patient comfort) but are tending to be minimized in the longitudinal direction (to reduce any curling propensities).
In this preferred embodiment, the reduced elongation properties in the longitudinal direction are believed to have been achieved as a result of holding the mesh in tension in the longitudinal direction at the time the mesh was coated. In other words, it appears that pre-stretching, or at least pre-tensioning the mesh in the longitudinal direction during the coating process, led to the reduction in elongation properties in the longitudinal direction as compared to the elongation properties in the longitudinal direction in the uncoated mesh sling. As a result, it is contemplated as part of the invention, that, should it be desired to avoid reduction of the elongation properties in the longitudinal direction, the mesh should not be held in tension along the longitudinal direction and perhaps should be held free of tension altogether, or in uniform tension, or in tension along the latitudinal direction prior to silicone coating.
In this regard, a number of tests have been performed to more fully expand the explanation and implementation of the present invention. These tests involve the acquisition of data on the elongation properties of the sling according to how the sling has been processed with a silicone coating. The result of the tests are set forth in the following table.
As is evident from the table, there were four types of slings that were tested, namely: (1) an uncoated sling; (2) a sling that was not held in tension while being coated with silicone; (3) a sling that was held in longitudinal tension while being coated with silicone; and, (4) a sling that was held in latitudinal tension while being coated with silicone. As is also evident from the table, each of the four slings were tested for respective elongation properties both in the longitudinal direction and the latitudinal direction. These tests were conducted using a 5 lb tension-loading device.
The resulting data is consistent with the elongation figures discussed previously. For example, when the sling is coated with silicone while under longitudinal tension, there is a dramatic decrease in longitudinal elongation properties in the resulting sling accompanied with a dramatic increase in latitudinal elongation properties in the sling as compared to the corresponding elongation properties of an uncoated sling. In addition, a sling coated with silicone under latitudinal tension leads to a sling having increased longitudinal elongation properties accompanied with reduced latitudinal elongation properties. As a result, it can be seen that desirable elongation properties that would otherwise not be available under normal conditions can be "locked" into the sling during the coating process.
One embodiment of the invention that is particularly exemplary of a manner in which to exploit the invention is set forth in
For example, in one embodiment, the central region 502 of the sling 500 has been coated with silicone while in latitudinal tension thus giving this central region 502 a somewhat increased longitudinal elongation property and a somewhat decreased latitudinal elongation property over a non-pretensioned coated sling (see Table A).
The intermediate regions 504 of the sling 500 have been coated with silicone while in longitudinal pre-tension, thus giving the intermediate region 504 a dramatically decreased longitudinal elongation property and a dramatically increased latitudinal elongation property over a non-tensioned, coated sling. Moreover, the intermediate regions 504 may molded into place to form the sling in a transverse direction (i.e., rotated 90�) as compared to the configuration of the fabric in the central region 502. As a result the longitudinal and latitudinal elongation properties exhibited by these intermediate regions 504 of the sling 500 actually correspond to the latitudinal and longitudinal properties, respectively, set forth in Table A for the sling that was silicone coated while in longitudinal tension.
The end regions 506 of the sling 500 have been coated with silicone while in longitudinal tension thus giving the end regions 506 a decreased longitudinal elongation property and an increased latitudinal elongation property (see Table A). The end result is a sling 500 that provides varying elongation properties along the length of the sling 500 that can be best suited to mitigate undesirable curling tendencies of the sling while enhancing the desirable flexibility characteristics of the sling.
Although the aforesaid embodiment is disclosed as comprising discrete portions of coated fabric that are molded into a complete sling, this aspect of the invention is not so limited. For example, it is within the scope of the invention to create a similar "multi-zone" sling merely by coating various regions or zones of a unitary sling under differing tension parameters at these various regions or zones.
In view of the above disclosure, it will be seen that the dual elongation properties of the invention as well as the coating by a substance such as silicone, enhances and improves the efficiency of the sling when placed in the patient. Furthermore, the coating and method of coating improves the lubricity between the mesh and the tissue and also appears to enhance the elongation properties of the sling. In other words, a sling in accordance with the present invention provides the needed long term support for effectively stabilizing the urethra to its normal anatomical position while also permitting temporary movement of the urethra (due to the dynamic nature of the patient's anatomy and movements) with the pelvis.
Depending upon the parameters of the coating process used, varying degrees of silicone thickness surrounding the mesh yarns can be obtained. However, in preferred embodiments, the holes or pores 24 remain open after coating. Referring to
In a preferred embodiment, a silicone-coated sling will have a generally rectangular shape that is approximately 2-12 cm wide (more preferably 10 cm) and 5-20 cm long. In particular, a silicone-coated sling of the present invention will be of sufficient size and dimension so as to pass behind the urethra and support the urethra in its normal anatomic position when implanted in vivo. In addition, the silicone-coated sling should be adapted so as to be capable of preventing abnormal urethral descent under increased intra-abdominal pressure.
It is contemplated that the present invention can be used with a variety of sling systems and methods for treating urinary incontinence. For example, a coated sling in accordance with the present invention, can be used with the system for the long term cure of recurrent urinary female incontinence as described in co-pending U.S. Pat. No. 6,328,686, the entire disclosure of which is hereby incorporated by reference. When used in such a system, a silicone-coated sling can be installed in vivo using the vaginal installation procedure as described in the application. Alternatively, a coated sling in accordance with the present invention can be prefabricated according to the dimensions and shapes as described, for example, in U.S. Pat. No. 6,042,534 issued Mar. 28, 2000 entitled "Stabilization sling for use in minimally invasive pelvic surgery" and installed as described in U.S. Pat. No. 6,042,534. A coated sling of the present invention can also be installed abdominally or laparoscopically using procedures well known in the art.
In addition, sheets of silicone coated fabric may be prepared in a similar manner for general pelvic floor reconstruction.
Next, in step 50, a container such as an aluminum pan is filled with the silicone dispersion for immersion of the mesh material. The pan should be kept covered (with foil, for example) when not in use, so as to prevent evaporation.
In step 60, the mesh material is placed into the dispersion mix and is held flat by use of, for example, 6″ (15.24 cm) embroidery hoops. When using embroidery hoops, the mesh material should be pulled through the edges of the hoop until the mesh material is taut, flat, and constrained along most if not all of the peripheral edges of the mesh material. Care should be taken not to inordinately stretch the material as this could result in distortion of the holes of the mesh material or in uneven coating of the mesh material, which can affect the dual elongation aspect of the sling. The mesh material should be trimmed to be sized closely to the dimensions of the hoop so as to minimize material overlap. The hoop containing the mesh material is placed into the pan containing the silicone dispersion for about 15 seconds, or more, and then removed.
In other embodiments, the sling material can be held in tension at opposite ends of the sheet prior to applying the coating. As discussed previously, depending on which direction of the mesh is in tension during coating, differing elongation properties in the sling may be obtained.
In step 70, excess silicone dispersion 42 is removed by allowing the silicone to drip off of the mesh material as the hoop is placed flat over the pan for about 1-5 minutes.
In step 80, the coating within the holes of the mesh material are cleared. This can be performed by using a foot-controlled air nozzle having an air setting of approximately 55-psi and 600 pulses per minute. Using the air nozzle, the coated mesh material can be continuously sprayed to clear the openings until there are minimal or no holes filled with silicone dispersion mix. In one embodiment, the spraying is performed intermittently. For example, pulsed air may be used.
In step 90, the coated mesh material is rested, air-sprayed side up, for approximately 5 to 15 minutes.
In step 100, the entire procedure outlined above in steps 50-90 is then repeated with the exception that the second side of the mesh material is now air-sprayed so as to ensure a uniform distribution of the silicone coating over all surfaces of the mesh material.
The spraying steps are performed also to ensure that the holes or pores of the mesh are not filled or closed with silicone. As stated previously in one embodiment of the invention, the sling has been coated with silicone but still contains open holes or pores to promote tissue growth.
In a preferred embodiment, the entire procedure outlined in steps 50-100 is repeated until both sides of the mesh material have 2 coats or more of dispersion 120. During the repeating process, alternate sides of the mesh material may be air-sprayed.
In step 140, the silicone coating is heated to set the silicone dispersion. This can be performed, for example, by hanging the hoops holding the mesh in an oven that is set at 160� C. (+/−10�) for about 20 minutes.
It is noted that the sling according to the present invention may be constructed using a batch processor a continuous process. For example, in a continuous process, the silicone dispersion may be placed in a large reservoir, and the strip material may be provided in an elongate, substantially continuous strip that is substantially continusously fed into the reservoir using, for example, rollers and/or mechanical clamping structures.
In step 160, the silicone coated mesh material is removed from the oven and allowed to cool. Following cooling, the material is then cut from the hoop. If desired, an anti-microbial substance or medicament can be impregnated into the silicone elastomer in a subsequent process.
After removing the material from the hoops, the silicone coated mesh material can then be fabricated as desired into a sling for use in treating urinary incontinence. As described previously, a silicone coated mesh material of the present invention, can be used to fabricate a sling such as described in U.S. Pat.No. 6,328,686, and then surgically implanted into a patient suffering from urinary incontinence.
In another embodiment, the sling material is configured in a long narrow elongated piece of mesh. The width is approximately the same width as a sling used in a patient. When coated, the edges of the material along the length of the material are coated with the silicone. When an elongated material is used in this manner, all that is required to obtain a sling suitable for use in a patient is to cut the elongated material through its width at the desired length of the sling. This will yield a sling that has the edges along the longitudinal side of the sling completely coated with silicone. In other words, since there is no necessary cutting in the longitudinal direction (because the material is already formulated to have the desired sling width) to obtain a desired size of sling, the integrity of the coating along the uncut edges remains intact, thus better ensuring the advantageous properties introduced in the sling as a result of coating.
A silicone coated sling as described herein can be fabricated into a variety of dimensions or can be manipulated to conform to a variety of sling specifications, depending upon user or manufacturer's preference. In addition, the coated sling can also be adapted so as to include structures to aid in the attachment or connection of the sling to the patient in vivo. It is also to be emphasized that silicone is only one coating that may be used, and, as such, is only exemplary, not limiting, in the context of the invention.
In still further embodiments in accordance with the present invention, it is desired to enable the user to more easily determine the presence and magnitude of tension in the sling material during placement of the sling. The ability to accurately make this determination will allow the user to adapt the fixation of the sling in the patient in a manner to maximize the potential of successfully treating the incontinence problem.
Referring to
When in the unstretched condition (
Referring to
The invention as disclosed in the embodiment of
The visual indicia described above could be integrated into the mesh material a variety of ways. For example, the mesh could actually be integrated into the fibers that are woven into the mesh so that the indicia is present upon weaving the material. In another example, the visual indicia could be added to the mesh as a component of a coating (e.g., silicone) applied to the mesh material.
Referring next to
It will be evident to the reader that the visual tension indicia component of the present invention is not limited to the isolated embodiments disclosed in the figures and that various combinations of visual tension indicia is also contemplated. For example, a mesh using a varying hole pattern indicia as in
The present invention provides a simple, safe and stable system for treating urinary incontinence. The invention, as described herein, with reference to preferred embodiments, provides a coated sling that supports an abnormally distended urethra to effectively remedy urinary incontinence.
Although the invention has been described in terms of particular embodiments and applications, one of ordinary skill in the art, in light of this teaching, can generate additional embodiments and modifications without departing from the spirit of or exceeding the scope of the claimed invention. Accordingly, it is to be understood that the drawings and descriptions herein are proffered by way of example to facilitate comprehension of the invention and should not be construed to limit the scope thereof.
All publications and patent applications in this specification are herein incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated by reference.
Patent Citations
Non-Patent Citations
Referenced by
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Photo by Cedric Angeles
YIELD: Makes 3 cups
For mousse:
Mellow the flavor of the chicken livers by placing them in a glass bowl with 2 cups milk. Cover; chill for 2 hours. Drain; discard milk. Return livers to same bowl, add the remaining 2 cups milk, cover, and chill for 2 more hours (or overnight). Drain; discard milk and rinse livers. Pat dry with paper towels.
Set a fine-mesh strainer over a medium bowl; set aside. Melt 2 tablespoons butter in a large skillet over medium-low heat. Add shallots and thyme and cook, stirring occasionally, until shallots are very soft, about 10 minutes. Add livers, increase heat to medium, and cook, turning once, until livers are firm but still pink inside, about 4 minutes. Remove pan from heat and stir in Calvados. Return to heat; cook until Calvados is reduced by half, about 30 seconds. Discard thyme.
Transfer liver mixture to a food processor; add 2 teaspoons salt and pepper. Process until smooth. With processor running, add remaining butter by tablespoonfuls until all butter is incorporated. Transfer mousse to prepared strainer. Using a rubber spatula, press mousse through strainer. Rinse and dry strainer, then strain mousse again, discarding solids in strainer. Divide among small jars. Chill until firm, 1-2 hours.
For gelée and toasts:
Place 1/4 cup water in a medium microwave-safe bowl. Sprinkle gelatin over water and let stand until softened, about 10 minutes. Microwave gelatin mixture until gelatin dissolves and mixture becomes clear, about 30 seconds. Add sugar; stir until dissolved. Stir in wine.
Spoon gelée over mousse in jars, forming a 1/4" layer (not all gelée may be used). Top each jar with thyme sprigs or leaves, if desired. Cover with plastic wrap and refrigerate until gelée is set, about 1 hour. DO AHEAD: Can be made 3 days ahead. Keep chilled.
Preheat oven to 450°F. Arrange bread triangles on a rimmed baking sheet. Brush with melted butter. Bake until golden brown, about 5 minutes. DO AHEAD: Can be made 1 day ahead. Store airtight at room temperature.
Let mousse soften slightly at room temperature for 30 minutes before serving with toasts.

subset: commoncrawl


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FROM now on Feedback will be looking a lot more closely at TV images of crowds apparently listening intently to a politician, nodding support for the company chairman or swaying in time with the music at a concert. A Californian called John Stanier has been granted a patent on a way of making politicians and performers look a lot more popular than they really are.
Stanier's idea was originally cooked up for movie and TV producers who need to show a crowd scene but cannot afford the huge cost of computer-generated graphics, let alone real members of Actors' Equity. Instead, they can now use a gaggle of "inflatable humanoid forms" - life-size dolls that are blown up when needed and positioned far enough behind the main action to be slightly out of focus.
The many pages of drawings that come with the patent (US 6688940) duly show dolls of all ...
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By John J. KruzelAmerican Forces Press Service
WASHINGTON, March 30, 2007 Over the last year, coalition forces have laid the foundation for stability and provincial Iraqi control in Anbar province, the commander of Multinational Force West said today.
"Our strategy of clear, hold and build, combined with an energized governmental and tribal engagement, is beginning to bear fruit," Marine Maj. Gen. Walt Gaskin told reporters at the Pentagon via satellite.
Progress is evident in the region's increased Iraqi security forces recruiting figures, decreased number of attacks, and in the upswing in economic commerce, he said.
Prime Minister Nouri al-Maliki's benchmark visit to the region, Gaskin added, was a large step in the right direction for reconciliation and reconstruction. "We cannot overemphasize the significance of having the prime minister come to an overwhelmingly Sunni chapter of Ramadi," he said.
"An important event which occurred in Ramadi while the prime minister was (here) was the first locally held meeting of the Al Anbar Provincial Council in 11 months," the commander said. "The council adjourned last spring from Al Anbar because of security concerns. This dialogue makes me very hopeful for the future of the province."
Anbar governance, Gaskin said, is beginning to function independently. Residents there are starting to put in place city mayors and provincial and municipal governorships, all of which are helping to stimulate economic development and provide input to the council.
Public sentiment toward al Qaeda in Iraq has shifted from "tolerance to open hostility" in the province, the general said.
"Anbar is different than the other 17 provinces in Iraq," Gaskin said, describing the unique challenges in Anbar. "It is predominately Sunni, the main threat that we have is al Qaeda in Iraq, and what we see is that once we gain the peace and stability into the major cities, then we can work on … pushing al Qaeda out."
Purging al Qaeda elements from Anbar cities requires three important aspects, including "getting the Iraqi police into the cities, getting the Iraqi army in support of the police (and) getting the coalition forces in overwatch," he said.
Many tribal sheikhs, a highly influential sector of Anbar society, believe reconstruction strategy is consistent with the principles of human rights, the rule of law and due process, and are encouraging young Iraqi men to enlist in Iraqi security forces, Gaskin said.
"It is with their permission and courageous leadership that the men of Al Anbar join the Iraqi army and the police," he said. "With the support of the local tribal leaders, the capabilities of the security forces are growing. The terrorists are finding it increasingly difficult to operate and hide within the civilian population."
There are about 2,500 members of the various emergency relief units, 13,200 policemen and 13,000 Iraqi army soldiers, alongside about 35,000 men and women of Multinational Force West currently serving throughout Anbar, Gaskin said.


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Lust List: Falling for fashionable flats
By Joy Sewing | August 7, 2013 | Updated: August 10, 2013 10:30pm
Photo By Club Monaco
ANIMAL INSTINCTS: Club Monaco has launched its first shoe collection, including the Makenzie Slipper, $249, at Club Monaco stores or clubmonaco.com.
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Involvement:General (knows how to use it) - Ownership:more than 1 monthPros:
Very high brightness, I believe that reaches over 200 meters. Really almost lit a small room. Looks solid. The type of diode used seems of the last generation and is of very high luminosity. Some comments spoke of warming, but I have not noticed that effect. A large battery. It also has various levels to adjust the brightness and battery consumption.Cons:
Maybe a little heavy and could lighten the material it is made??. Batteries are not standard (non-AA or AAA), which requires the availability of a specific charger. Perhaps, the different operating modes makes a bit complicated to use. But at least, seems to have memory of the last mode.OtherThoughts:
Nothing special. Excellent purchase.Bottomline:
Good product and good service delivery.
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Cognition: An Erica Reed Thriller Review
Played on:
Game developers will tell you, making games is a labor of love. The hours are long, the work is back-breaking, the end-product is as ephemeral as an ice cream cone in July; still, for people passionate about games, it's all worth it. Young development company Phoenix Online Studios is made up of just such passionate people, as its premier point-and-click adventure, Cognition: An Erica Reed Thriller, readily shows.
The titular heroine, Erica Reed, is an FBI agent with a special skill; by touching objects, she can see visions of the past. You'd think this would be an advantage for an officer of the law, but Erica doesn't see it that way. For one thing, she can't control this power and is oftenwithout warninghit in the head with a psychic sledgehammer. For another, she's haunted by the role her visions played in the death of her brother, who was murdered years before by a sibling-obsessed serial sicko called the Cain Killer. Never having nabbed this sadistic creep, Erica's a haunted woman, tormented by guilt, grief and increasingly violent visions. Despite this, when a new serial murderer arrives on the scene, she's determined to do whatever it takes to bring him (or her) to justice.
Cognition starts in the past, during the Cain Killer case and is for me, the weakest part of the game. I'd played this portion before during an earlier demo and was disappointed that it hadn't been polished. The dialog here is wooden, the character exchanges are unconvincing and the gameplay's fairly slow. Fortunately, once that first awkward ten minutes is done, Phoenix Online hits its stride and things get infinitely better.
Like most FBI agents, Erica has a partner; in this case, he's a stout, middle-aged guy in a trench coat called John. I won't say that John and Erica have the chemistry of a Mulder and Scully, but here and there you can control John as well as Erica which adds interest to the proceedings. Personally, I would wish for this mechanic to be developed more in future episodes because in some ways, Cognition hearkens back to Jane Jensen's classic Gabriel Knight series and as such, is a natural for a dose of those games' fictional complexity. Regardless, it still offers us more than the usual linear adventure experience through the use of branching dialog.
For the uninitiated, branching dialog means that different things happen depending on how you talk to people. If you're forceful, you might have to strong-arm your way through a slew of subsequent situations; conversely, if you're friendly, things could be a lot easier for you. In Cognition, it also means you'll have some occasionally weird (the psychic shop owner) but mostly entertaining interactions with a cast of somewhat-exaggerated secondary characters. When things are weird it's largely due to the writing which at times is a little stiff. Even so, the game spins a surprisingly adult yarn (adult in the real sense of the word, not the boom-chicka-wow-wow one). Cognition's narrative is highly disturbing at times and as a fan of cop dramas, movie thrillers and Showtime's Dexter, I can appreciate that. The best thing about the game by far however, even beyond its edgy storytelling, is Erica's psy-power ability.
Cognition's struck gold with this idea since it could easily carry a series of sequels. What's cool about it is that as time goes on, it develops. With the help of her psychic mentor, throughout the game Erica discovers new ways her ability can be used and in gameplay terms, this means a range of interesting and varied skills to use in a range of different situations. When using these skills, the screen changes to an effect that calls to mind Batman: Arkham Asylum's Detective Mode as ghostly images of the past play themselves out on screen. The puzzle aspect of the psy-powers (the most fun part) is figuring out which power to use, which items Erica should touch, in what combination and when. For instance, you might touch items at a crime scene to use Projection. This allows you to replay aspects of the crime as it happened. Or you might use Regression, which when you touch them, enables you to dig around in someone else's memory. This mechanic alone differentiates Cognition from the tons of other crime-themed games out there and while the concept is well-developed already, I can envision it becoming even more fun and more complex in future episodes.
Graphically speaking, Cognition is pretty solid, on par with its spiritual antecedents (such as Jane Jensen's Gray Matter.) There are the occasional hiccupssuch as Erica's rock-hard hair, some questionable draftsmanship in the 2D comic-book-style cutscenes, and some very strange 3D crotch modeling, but overall, it's a job well done. For my money though, it's the sound that steals the show.The acting is generally good and Phoenix Online deserves particular credit for finding such a great voice for its heroine. Her voice is strong, feminine and likable enough to listen to for hours. The music too is pretty great. Not to belabor the Jane Jensen point, but more than a few times, Cognition's dramatic soundtrack gave me the same feelings of anticipation and excitement as the music from Jensen's games.
For a first effort and a brand-new IP, Phoenix Online Studios has done an admirable job. Although in places Cognition's graphics are little rough and the writing's a little unnatural, it offers us an adult-level adventure game full of interesting mechanics, a professional voice cast, great music and a compelling heroine. After playing the first Erica Reed episode, I have no doubt there will be future ones and no doubt that through them, Phoenix Online will iron out the remaining kinks and create for us a truly memorable adventure series.


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Jodie Foster, lead female actor in the epic movie Contact, based on Carl Sagan's book by the same name, donated towards keeping the Allen Telescope Array of SETI alive and kicking. Good news! It's alive and kicking!Read More
A new fourth moon of Pluto has been discovered, thanks to Hubble.Read More


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An electromagnetic active vibration actuator configuration combines two modes of operation to obtain the advantages of long stroke and linearity of voice coil type actuators and high efficiency of dual-gap solenoid type actuators. A coaxial stator shell surrounds an axially vibratable armature. Either the stator or the armature can carry one or more coils and/or permanent magnets, however usually the magnets are located on the armature for their contribution to vibrating mass. Alternate coils and alternate magnets are made opposite in polarity, the stator armature pole pieces being held symmetrically staggered relative to the stator pole pieces by end springs or flexures that allow axial vibration when AC is applied to the coils. Two different types of flux loop paths are associated with each pair of permanent magnet prominent poles: a voice-coil-effect flux loop path including two air gaps, each traversing a coil, that remain relatively constant in separation distance and permeability under vibration, and a solenoid-effect loop flux path traversing a pair of gaps in series flanking a coil prominent pole, that vary in separation distance and permeability in a complementary manner under vibration in the manner of a solenoid type actuator. These two magnetic modes operate in a cooperative additive efficient manner. Multiples of a typical magnet/coil pair can be easily tandemed using common building block component elements, typically being made to have in total an odd number of prominent poles. Wide flexibility is provided in design and manufacture to customize the performance of the actuator by manipulating the proportion of voice coil effect and solenoid effect along with the mechanical spring effect and the vibrating mass.
1. An electromagnetic force actuator, for active vibration control, motivated in a dual magnetic manner by a combination of voice-coil-effect and solenoid-effect flux paths, comprising;
an electromagnetic coil structure of magnetically permeable material constructed and arranged to have a typical cross-sectional shape defining at least one prominent pole facing a common reference line at a predetermined spacing distance and separating two of a plurality of adjacent channels formed in the magnetically permeable material each filled with an oppositely polarized coil winding oriented such that wire ends appear in the cross-sectional shape;
a magnet structure having at least one permanent magnet with a pair of magnetically opposed prominent poles of magnetically permeable material having a cross sectional shape such as to face the common reference line from a direction opposite the coil structure, disposed along the common reference line such that the prominent pole(s) of the coil structure and those of the magnet structure are located in a staggered symmetric disposition about the common reference line so as to be mutually centered axially;
suspension means constructed and arranged to retain the coil structure and the magnet structure facing the common reference line at a constant distance therefrom while providing freedom for the electromagnetic coil structure and the magnet structure to vibrate relative to each other in an axial direction along the common reference line:
magnetic flux path conducting means, including magnetically permeable material, for conducting magnetic flux, configured and arranged to conduct portions of magnetic flux paths extending from a first prominent pole of each magnet through a path to a second and opposite prominent pole thereof, the flux paths including (1) a voice-coil-effect flux path that traverses first and second air gaps serially, each gap being made to have substantially constant separation distance under vibration and each containing respectively a central portion of a first and second one of two adjacent ones of said oppositely polarized coil windings, and (2) a solenoid-effect flux path that traverses serially (a) a first air gap containing an end portion of the first coil winding, (b) a prominent pole of the coil structure that is axially movable with respect to the magnet poles, and (c) a second air gap containing an end portion of the second coil winding; the first and second air gaps being constructed and arranged to have respective separation spacings and permeabilities that vary with vibration in a complementary manner;
said actuator being made to have an odd total number of prominent poles and thus to have at least three prominent poles; adjacent magnets being oppositely polarized and adjacent coils being oppositely polarized; and
spring means constructed and arranged to provide a spring force tending to establish and maintain the mutually centered relationship between each prominent pole of the coil structure and corresponding prominent poles of the magnet structure;
whereby, in response to alternating current applied to the coil windings, at least one of said structures is caused to vibrate relative to the other, operating in first part according to principles of a voice coil type actuator due to e.m.f. of the voice-coil-effect flux path having substantially constant permeability and acting directly on the said oppositely polarized coil windings as a force in an axial direction, and operating in second part according to principles of a dual-gap solenoid type actuator in the solenoid-effect flux path due to magnetic attraction forces typically between a stator prominent pole and an adjacent movable armature prominent pole, with recurrent complementary flux redistribution in the two air gaps from the complementary variation of respective gap separation distances and permeabilities under vibration.
2. The electromagnetic force actuator as defined in claim 1, wherein said coil structure, constituting a stator assembly, comprises:
a tubular shell, of permeable magnetic material;
a pair of end plates disposed one at each end of said tubular shell:
a quantity of n+1 annular coils, connected alternately in opposite phase polarity relationship, disposed around an inner peripheral region of said shell, each centered axially about a corresponding one of said pole pieces of the armature; and
a quantity of n annular stator rings of magnetically permeable material disposed between said coils in an interleaved manner, extending inwardly from said shell so as to constitute the prominent poles of the coil structure;
and wherein said magnet structure, constituting a cylindrical armature assembly disposed coaxially and centrally within said shell, comprises:
a quantity of n identical short cylindrical permanent magnets, each having a pair of parallel magnetically opposite flat pole faces, said magnets, if n>1, being stacked coaxially in alternating polarity directions; and
a quantity of n+1 identical short cylindrical armature pole pieces of permeable magnetic material interleaved with said permanent magnets, each adjacent pair of pole pieces flanking and interfacing with pole faces of a corresponding one of said magnets, said pole pieces extending radially outwardly so as to constitute corresponding prominent poles facing the common reference line and forming an annular air gap extending to said shell.
3. The electromagnetic force actuator as defined in claim 2 wherein the stator assembly further comprises an additional pair of said stator rings, disposed at opposite ends of said stator assembly between a corresponding one of said end plates and a corresponding adjacent outermost one of said coils.
4. The electromagnetic force actuator as defined in claim 2 wherein said suspension means comprises a cylindrical support shaft, secured at each end to a corresponding one of the end plates, traversing a cylindrical passageway provided through said armature assembly, made and arranged to allow said armature assembly to vibrate axially.
5. The electromagnetic force actuator as defined in claim 2 wherein said suspension means comprises a cylindrical support shaft, secured concentrically to said armature assembly with two opposite ends each supported slidably by extending through a corresponding one of the end plates, whereby axial vibration of said armature is enabled and whereby such vibration may be transmitted to an external object via an end portion of said support shaft.
6. The electromagnetic force actuator as defined in claim 2 wherein said spring means comprises a pair of coil springs, each disposed between a corresponding end plate and a corresponding outermost one of said armature pole pieces so as to exert a spring force therebetween.
7. The electromagnetic force actuator as defined in claim 1 wherein said suspension means comprises a pair of spring flexure assemblies, each disposed between a corresponding one of the end plates and a corresponding outermost one of said armature pole pieces, each flexure assembly comprising:
at least one pair of flat spring strips crossing each other centrally so as to form a star-shaped pattern with uniformly spaced ends, secured to a corresponding end of said armature assembly such that the ends extend radially from the central axis; and
a concentric flexure ring of resilient material constructed and arranged to captivate the extending ends of the star pattern and to be secured against an inner surface of a corresponding end plate, and to thusly support said armature disposed coaxially in said shell and centered between the end plates in a manner that allows said armature assembly to vibrate axially in response to alternating current applied to said coils.
8. The electromagnetic force actuator as defined in claim 7 wherein said suspension means further comprises:
a pair of screw fasteners, one disposed centrally at each end of the armature assembly, traversing a central opening provided in each of said spring strips and threadedly engaging the corresponding end of said armature so as to secure said spring strips to the armature assembly.
9. The electromagnetic force actuator as defined in claim 8 wherein said spring means consist of said spring strips in said suspension means.
10. The electromagnetic force actuator as defined in claim 8 wherein wherein said spring means further comprise:
a pair of coil springs, disposed coaxially at opposite ends of armature assembly so as to exert therefrom a spring force against a corresponding end plate, and
said spring strips in said suspension means working in conjunction with said coil springs so as to establish a predetermined spring modulus.
11. The electromagnetic force actuator as defined in claim 6 further comprising an additional pair of stator rings, identical with said stator rings, disposed at opposite ends of said actuator between a corresponding end plate and an adjacent outermost one of said coils.
12. The electromagnetic force actuator as defined in claim 7 wherein each of said spring flexure assemblies is constructed and arranged to have a cross-sectional shape defining (1) a short tubular-shaped portion made to fit against an inwardly-facing surface of a corresponding outermost ring, (2) a first flange, extending radially inwardly from a first edge of the tubular portion, captivating the ends of the spring strips, and (3) a second flange, at a second edge of the tubular portion opposite the first edge, extending radially outwardly for retention between the corresponding outermost ring and the corresponding end plate.
13. The electromagnetic force actuator as defined in claim 12 wherein each of said end plates is configured with an inwardly-facing annular channel dimensioned and located to accommodate and retain the second flange of a corresponding one of said flexure rings.
14. The electromagnetic force actuator as defined in claim 1, wherein said magnet structure, constituting a cylindrical armature assembly, comprises:
a cylindrical permanent magnet having opposite magnetic poles at corresponding opposite flat parallel surfaces; and
two identical cylindrical pole pieces of permeable magnetic material, flanking said permanent magnet, configured and arranged to constitute corresponding prominent armature poles facing said shell;
and wherein said magnetic coil structure, constituting a stator assembly, comprises:
a tubular shell, of permeable magnetic material,
a pair of end plates disposed one at each end of said shell and attached thereto;
two annular coils, connected in opposite phase polarity relationship, disposed around an inner peripheral region of said shell; and
a stator ring of magnetically permeable material, disposed centrally between said two coils, extending radially inward from said shell so as to constitute a prominent pole of the magnetic coil structure;
suspension means for supporting the armature assembly in said shell with positive coaxial constraint and with spring-loaded axial constraint arranged to establish a central quiescent axial armature location at which the two armature pole pieces straddle said stator ring symmetrically and about which the armature can be driven, by alternating current applied to said coils, so as to vibrate axially against the spring-loaded axial constraint.
15. The electromagnetic force actuator as defined in claim 14 wherein the stator assembly further comprises an additional pair of said stator rings, disposed at opposite ends of said stator assembly, each retained between a corresponding one of said end plates and a corresponding one of said coils.
16. The electromagnetic force actuator as defined in claim 1, wherein:
said magnet structure is incorporated in a stator assembly comprising:
a tubular shell, of non-magnetic material, including a pair of end plates disposed one at each end thereof;
a quantity of n annular-shaped permanent magnets located peripherally inside said shell, each having two opposed parallel faces defining magnetic poles of opposite polarity, stacked adjacently with alternating polarity so that poles of like polarity face each other; and
a quantity of n+1 annular-shaped stator rings of magnetically permeable material disposed between said magnets in an interleaved manner, extending inwardly from said shell past said magnets so as to constitute the prominent poles of the magnet structure;
and wherein said coil structure is incorporated in a cylindrical armature assembly, surrounded coaxially by said stator assembly, comprising:
a generally cylindrical central core of magnetically permeable material configured and arranged to define a row of n+1 adjacent annular-shaped coil winding bobbin channels interleaved with cylindrical prominent pole pieces extending radially outward from said core and facing said shell; and
a quantity of n+1 identical annular coils, connected alternately in opposite phase polarity relationship, disposed each in a corresponding one of said bobbin channels and each centered axially about a corresponding one of said stator rings.
17. The electromagnetic force actuator as defined in claim 1 wherein said suspension means comprises a pair of spring flexure assemblies, each disposed between a corresponding one of the end plates and a corresponding outermost one of said armature pole pieces, each flexure assembly comprising:
at least one flat spring strip, secured centrally to a corresponding end of said armature assembly such that two opposite ends thereof extend radially from the central axis; and
a concentric flexure ring of resilient material constructed and arranged to captivate the extending ends and to be secured against an inner surface of a corresponding end plate, and to thusly support said armature disposed coaxially in said shell and centered between the end plates in a manner that allows said armature assembly to vibrate axially in response to alternating current applied to said coils.
The present invention relates to the field of active vibration control for machinery with moving parts such as aircraft, land and marine vehicles and industrial equipment; more particularly it relates to electrically-powered actuators, of the type wherein a mass is driven vibrationally in a manner to suppress vibrational disturbance.
Active vibration actuators, like passive vibration absorbers, generally consist of two separate mass portions, one of which is typically attached to a target region for suppression of vibrational disturbance while the other is suspended so that it can vibrate in a manner to reduce the vibrational disturbance. In an active vibration actuator a suspended mass is driven to vibrate, typically electromagnetically, while in the passive vibration absorber the vibrating mass receives drive excitation only through reaction between the two masses and thus the vibrational disturbance can only be attenuated, never fully cancelled.
In an electromagnetic active vibration actuator, the two masses typically correspond to a stator assembly and a vibratable armature assembly, either or both of which can include a coil powered from an AC (alternating current) electrical source and/or a permanent magnet system; a suspension system between the two mass portions allows reciprocal vibration, which takes place at the frequency of the applied AC. Generally the stator will be solidly attached to a machine, engine frame or other body subject to vibrational disturbance, while the armature is vibratably suspended and is driven to vibrate, relative to the stator, at a predetermined frequency, typically that of the vibrational disturbance, the phase and amplitude being optimized to produce a counter-reaction from the driven vibrating armature mass that act in a manner to suppress the vibrational disturbance.
Another version of active vibration actuator delivers output via a moving shaft, typically driven axially; the main body of the actuator unit is attached solidly to a massive body such as a machine frame, and the output shaft is attached to the part or region in which vibrational disturbance is to be suppressed by transmitting a counteracting vibrational force via the output shaft.
Theoretically, a non-feedback active vibration control actuator could be fine-tuned and adjusted in manner to completely cancel disturbing vibration, however in order to track any change that may take place in the parameters of the vibration, the active vibration actuator is usually placed under control of a feedback loop that responds to sensed vibration.
Typical structure of an active vibration control actuator is coaxial, with the stator assembly including a soft steel tubular shell housing surrounding an axially-vibratable armature assembly. The stator assembly and/or the armature assembly can include any of three basic elements: permanent magnets, coils and/or low-reluctance path segments such as yokes, cores, pole pieces, etc. made from ferromagnetic material such as soft steel or iron. Such magnetic material will be referred to henceforth herein simply as iron.
Such actuators are motivated via magnetic flux paths that can each be represented by a loop that typically includes at least a coil, a permanent magnet, one or more iron segments and one or more relatively small air gaps.
This mass is motivated electromagnetically from AC in the coil in a manner to cause it to vibrate at frequencies, amplitudes and phase angles that optimally suppress the disturbing vibration: this may be accomplished by an electronic feedback loop and control system that senses vibration both at its source and in the disturbed region, and automatically adjusts the frequencies, amplitudes and phase angles to minimize the disturbing vibration.
Typically the vibrating mass is supported by end spring suspension members or flexures which act to hold it centered when in a quiescent condition, i.e. with no current applied to the coils. The mechanical spring is characterized by a spring modulus (sometimes referred to as spring constant or spring rate) defined as force/deflection distance. The combination of the spring modulus and the vibrating armature mass determines a frequency of natural vibration resonance. Current in the coil(s) of the actuator generally acts in a manner of a negative spring modulus to override the force of the mechanical spring suspension and drive the armature to vibrate at the driven frequency; however, at frequencies other than the natural resonant frequency, the actuator may operate inefficiently due to improper magneto-mechanical coupling.
Overall electrical power efficiency, i.e. mechanical output energy versus electrical driving power, is important in an active vibration control actuator; the different configurations of the basic elements found in known art represent different approaches seeking to optimize the important overall parameters such as efficiency, performance, reliability and ease of manufacture. A key factor is the natural mass-spring resonance and the extent to which this can be altered or overpowered by the electromagnetic drive system.
Active electromagnetic vibration control actuators of known art can be categorized in two general types: voice coil type and solenoid type.
The voice coil type of actuator gets its name from well known loudspeaker structure wherein a tubular voice coil assembly, typically a single layer of wire on a vibratable voice coil form, is constrained concentrically by suspension means and centered in an annular magnetized gap of constant separation distance and constant permeability formed in a flux path loop that includes a stationary permanent magnet. When an electrical current is applied to the voice coil, a force equal to the cross-product of current and magnetic flux density is exerted on the voice coil in a direction defined by the classical Right Hand Rule of electromagnetics, driving the voice coil in the direction of the force to a displacement that is constrained by the suspension springs.
Typically the loudspeaker voice coil is made to extend well beyond the region of the magnetic gap symmetrically in both directions, so that at any instant, as it travels back and forth, only that portion of the voice coil within the magnetic gap interacts directly with the concentrated magnetic field to produce the driving force. Alternatively the voice coil may be made much shorter than the extent of the magnetic gap so that, when vibrating to its limit of travel, it remains entirely within the magnetic gap. In either case, in the conventional loudspeaker voice coil driver, there is an inherent sacrifice of efficiency due to this partial coil-to-magnet coupling, in a tradeoff to gain linearity and long stroke travel capability.
In applying the voice coil principle to active vibration actuators, generally the fixed portion or stator is made to include a tubular iron shell housing. The voice coil may be made multi-layer, may be associated with nearby iron members for concentrating flux and may be made fixed rather than moving. The typical fixed central magnetic core pole piece of the loudspeaker may be replaced by a movable central armature suspended in a manner to be vibratable axially, usually constrained by end springs, thus constituting a vibratable mass.
In a moving-coil version of a voice-coil type actuator, permanent magnets may be attached immediately inside the fixed iron outer shell stator assembly surrounding a vibratable armature which carries multi-layer coils wound on a iron core formed with associated iron pole-piece prominences, and which thus constitutes the vibratable mass.
Conversely, in a moving-magnet version of a voice-coil type actuator, multi-layer coils may be attached immediately inside the iron outer shell stator assembly, surrounding the vibratable armature which carries permanent magnets and associated iron pole-piece prominences, and which thus constitutes the vibratable mass.
Typically, in both the moving-coil and the moving-magnet versions of voice-coil type active vibration actuators, a concentric central moving armature is configured with at least two magnetic prominences formed by short cylinders whose circumferences each form an annular magnetic air gap with the iron shell. In typical cross-section, the armature prominences and the stator prominences are made to both face a common reference line from opposite sides so that the armature assembly can be easily inserted into and withdrawn from the stator assembly.
Electromagnetic active vibration actuators can be classified into two general types: voice-coil type and solenoid type. Both types may have a coaxial electromagnetic structure wherein a stator portion and an axially-vibratable armature are linked together by a magnetic flux loop path that includes at least one permanent magnet, an AC-driven coil, and at least one magnetic air gap.
The voice coil type operates on the principle of force acting on wire in a coil in a magnetic field, the force acting in a direction perpendicular to the direction of current and perpendicular to the magnetic field, according to the Right Hand Rule. The magnetic field is concentrated in an air gap (or gaps) having a separation distance and permeability that remain substantially constant in operation as the armature travels axially. The armature, like the voice coil of a loudspeaker, requires some form of spring suspension to establish a normal stabilized centered position, otherwise the armature would free-float axially and drift off center.
In contradistinction, the solenoid type actuator operates generally on the principle of attraction between movable magnetized bodies; more particularly a magnetic force acts on a movable armature through a magnetized air gap whose separation distance varies with armature displacement and thus the permeability is incremental, the armature tending to move in a direction that intensifies the magnetic flux in the air gap.
A simple solenoid without any permanent magnet typically attracts an armature from an offset large-gap position to a centered small-gap position or an end-of-travel closed-gap position in response to DC of either polarity in the coil; thus, with AC applied to the coil, any vibration response would be very inefficient and at a doubled frequency. For use as a vibration control actuator, the solenoid is modified to be magnetically biased, e.g. by the addition of a pair of permanent magnets (or one permanent magnet and a second coil) to form a dual-gap solenoid type actuator.
When the coil of such a dual-gap solenoid type actuator is AC-driven, thus vibrating the armature, there is a recurring redistribution of magnetic flux in each pair of gaps that sets up eddy currents in the pole pieces. Therefore, while the dual-gap solenoid type provides good efficiency, especially in applications where the armature may be allowed to travel to an end limit where the gap closes, in active vibration applications the dual-gap solenoid type generally suffers the disadvantages of complexity of structure and the need for tight tolerances between parts. Another disadvantage is the limitation of the amplitude of travel of the armature, limiting the use of this type of actuator to high frequencies. At such high frequencies, the iron pole pieces may require slotting or lamination to avoid excessive eddy current losses due to the magnetic flux variations. Yet another disadvantage is the small mass of the armature, making it usually necessary to use the exterior mass of the coil and magnet structure as the inertial mass. Also, while a voice coil type actuator can be readily extended by adding more voice-coils and corresponding gaps, the dual-gap solenoid type actuator can be extended only by adding one or more complete similar actuator units in a tandem manner.
In FIG. 1, a cross-sectional representation, shows an example of a moving-magnet version of a voice coil type actuator 10A illustrating in basic form the principles taught by U.S. Pat. No. 5,231,336 disclosing an Actuator for Active Vibration Control and by U.S. Pat. No. 5,231,337 disclosing a Vibratory Compressor-Actuator, both by the present inventor.
A stator portion is formed by two voice coils C1 and C2 located side by side, connected in opposite polarity, and fastened immediately inside a tubular iron shell 12 fitted with end plates E1 and E2.
A cylindrical central vibratable armature portion contains a permanent magnet M, magnetized as shown (N, S) with opposite magnetic poles at opposite parallel end planes fitted with cylindrical iron prominent pole pieces P1 and P2. These, facing iron shell 12, form a corresponding pair of annular air gaps through which a magnetic flux loop path 14 traverses corresponding central portions of voice coils C1 and C2. The moving armature is vibratably supported on a central rod 16 such in an axial direction only, by sliding along rod 16, as indicated by the double arrow. The armature is constrained by a pair of end springs S1 and S2, which, bearing against end plates E1 and E2, also act as elastic end stops or bumpers that limit the axial travel range of the armature.
When AC is applied to coils C1 and C2, the portion of each voice coil within the corresponding magnetic gap receives a Right Hand Rule force as described above; the resulting stator-to-armature forces at the two gaps are additive due to the opposite coil polarities, thus the armature is caused to vibrate axially as indicated by the double arrow. The two magnetic air gaps, moving axially along with the vibrating armature, remain substantially constant in separation distance and permeability.
FIG. 2 illustrates a solenoid type of actuator of known art, wherein the stator portion includes a continuous coil winding C located immediately inside an iron shell 12A and two annular permanent magnets M1 and M2 located inside coil winding C. The magnets are oppositely polarized so that like poles each face an annular iron ring R, i.e. NSRSN as indicated, or alternatively SNRNS. Ring R forms a prominent pole piece facing inwardly toward a reciprocating cylindrical iron armature core 18 fitted with a central support shaft 20 that protrudes through sleeve bearings formed in iron end plates E1 and E2, suspending core 18 with freedom to vibrate axially and to transmit vibration output to an external object via an extending end of shaft 20.
Magnets M1 and M2 set up magnetic flux paths 22A and 22B respectively that loop through the two corresponding opposite ends of armature 18 as shown. In the central position shown, with zero current in coil winding C, the magnet flux paths 22A and 22B tend to balance and in effect cancel each other with regard to driving forces applied to armature. This condition is a critical unstable balance in the absence of end springs to hold the core 18 centered, since core 18 will be magnetically attracted to either end plate E1 or E2 increasingly as it moves off center. Thus, without end springs, the solenoid as shown would be bistable; therefore in most cases some form of spring suspension is required to stabilize the armature in the center position.
When electrical current is applied to the coil winding 10C, an additional flux path 22C is set up as shown in the dashed line, looping through the iron shell 12A, the iron end plates E1 and E2 and the core 18 as shown. The magnetic flux from the coil, having the direction shown by the arrow heads, aids flux path 22A and opposes path 22B, thus urging the core 18 toward the left due to the increased magnetic attraction to iron end plate E1. Conversely, current in the opposite direction in coil winding C will urge the core 18 toward the right. Thus AC in the coil will cause the armature to vibrate reciprocally at the frequency of the AC.
U.S. Pat. No. 4,641,072 to Cummins discloses an Electro-Mechanical Actuator of the solenoid type wherein the moving armature includes a portion located external to the stator shell, containing coils, and a portion enclosed by the stator shell containing a pair of permanent magnets.
U.S. Pat. No. 4,710,656 to Studer discloses a Spring Neutralized Magnetic Vibration Isolater providing an electronically-controllable driven system with a single degree of freedom suspension element exhibiting substantially zero natural frequency of vibration. Non-resonance is obtained through a viscous damping effect from a combination of a spring, a mass, two permanent magnet circuits, and an electromagnetic coil driving a shunting/shorting armature in a solenoid mode.
It is a primary object of the present invention to provide improved efficiency in an active vibration control actuator by combining features of the voice coil type and of the solenoid type in a manner to better overcome the disadvantages of each.
It is a further object to utilize pairs of magnetic gaps in a manner that magnetic flux variations in each gap of a pair are made to be complementary to each other and thus additive with regard to output force, due to the differential in the pair.
It is a further object to utilize a plurality of magnets in a manner to cause the same forces to act on all magnets in the same direction, so that when the current reverses, all the forces are made to reverse.
It is an object of the invention to provide the designer and manufacturer of the actuator with greatly increased design control over the output force as a function of frequency (spectrum) by enabling the forces and damping of each of the two types (voice-coil and solenoid) to be balanced against each other through a selection of standard building block components including properly chosen internal suspension springs.
The abovementioned objects have been accomplished by the present invention of an electromagnetic active vibration actuator configuration that combines features of actuators of the voice coil type with features of the solenoid type. A coaxial stator shell assembly with one or more identical short annular prominences arranged in a row extending inwardly surrounds an axially vibratable armature with one or more corresponding short cylindrical prominences arranged in a row extending outwardly, with either the stator or the armature having one more prominence than the other. In the quiescent central position of the armature, the armature prominences and the stator prominences are constrained midway relative to each other by end springs suspending the armature in the stator.
In a first embodiment, at least two coils are located in the stator, which is made to have at least one central prominence between a pair of adjacent coils, and at least one permanent magnet is located in the armature, flanked by a pair of prominences constituting magnetic poles. In a second embodiment, permanent magnets are located between the stator prominences and coils are wound on a common armature core and located between prominences extending outwardly from the core. Adjacent coils and adjacent magnets are always oppositely polarized.
In either embodiment, there are two distinct operational magnetic flux loop paths associated with each permanent magnet prominence: a voice-coil-effect flux loop path extending directly through the mid region of a coil into the opposite main magnetic element (iron shell or core) forming an air gap that has a substantially constant separation distance and permeability under vibration, and a solenoid-effect flux loop path that extends from a first magnet pole, through a first air gap including a first end of coil, through a coil magnetic prominence, then through a second air gap including a second end of the coil to the second magnet pole, such that under vibration the two gaps vary in separation distance and permeability in a complementary manner. The solenoid effect can be intensified by including iron ring end prominences in the stator and/or by utilizing end plates made of iron material thus setting up a further flux loop. Conversely the solenoid effect can be downsized by omitting stator end prominences and/or iron end plates, or even omitting some of the stator prominences in a multi-section actuator.
Thus the voice coil effect and the solenoid effect act cooperatively in applying force to the armature in an axial direction that depends on the direction of current in the coils, in combination providing improved efficiency in driven vibration of the armature in response to AC power applied to the coils.
Furthermore the solenoid effect created by the structure of the magnet system in this invention acts in a manner to introduce a negative spring modulus that opposes the positive spring modulus of the mechanical spring suspension in determining the system spring modulus and thus the natural resonance frequency.
The above and further objects, features and advantages of the present invention will be more fully understood from the following description taken with the accompanying drawings in which:
FIG. 1 is a cross-sectional representation of an active vibration actuator of known art of the voice coil type in a simple basic form having a single permanent magnet armature and a dual voice coil stator.
FIG. 2 is a cross-sectional representation of an active vibration actuator of known art of the dual-gap solenoid type having a single iron core armature and a stator having two permanent magnets and a coil.
FIG. 3 is a cross-sectional representation of an active vibration actuator of the present invention in its simplest basic embodiment with a dual voice coil stator and a moving permanent magnet armature.
FIG. 4 is a cross-sectional representation of an active vibration actuator of the present invention in a generalized multi-section moving-magnet embodiment based on an expansion of the actuator of FIG. 3, utilizing the same basic elements.
FIG. 5 is a cross-sectional representation of an active vibration actuator of the present invention in a generalized alternative multi-section moving-coil embodiment.
FIG. 6 depicts a basic embodiment similar to that shown in FIG. 3 but with the addition of two stator end rings and a pair of armature suspension flexure assemblies.
FIG. 7 is an end view of a flexure assembly as used in the embodiment of FIG. 6.
FIG. 7A is a central cross-sectional view of the flexure assembly of FIG. 7 with the armature in a central quiescent location.
FIGS. 7B and 7C show cross-sections of a flexure assembly as in FIG. 7A with the spring strips bending in opposite directions corresponding to axial offsets of the armature.
FIG. 8 is a graph showing force generated by an actuator as a function of frequency for the present invention compared to a strictly voice coil type actuator without internal annular iron stator rings.
FIGS. 1 and 2 have been described above.
FIG. 3 is a cross-sectional representation of a basic moving-magnet embodiment of a moving-magnet active vibration actuator of the present invention, shown in its simplest form for ease of understanding. An iron shell 12 is closed at the ends by end plates E1 and E2 which can be made from either magnetic or non-magnetic material, as a design option that alters the magnetic configuration and operation of the actuator.
The stator assembly contains two voice coils C1 and C2, immediately inside shell 12, connected in opposite polarity as indicated by the current symbols I1 (0) and I2 (X). The coils are separated by an annular iron ring R contacting the inside wall of shell 12 and facing inwardly to serve as a prominent electromagnetic pole piece.
The armature assembly includes an annular permanent magnet M, magnetized to provide poles at opposite parallel end surfaces as indicated N and S. These surfaces interface with short cylindrical iron pole pieces P1 and P2 which each set up a pair of magnetic air gaps with shell 12, each gap containing a bundle of concentrated magnetic flux lines, one gap traversing a central portion of coil C1 and the other gap traversing a central portion of coil C2.
The armature assembly is movable in an axial direction by sliding on a central shaft 16 which is fastened to end plates E1 and E2. The armature is constrained in a centered position by springs S1 and S2 which may be selected for spring modulus to provide a desired natural resonant frequency of the vibrating mass, i.e. the armature.
Permanent magnet M sets up two main magnetic flux loop paths: a solenoid-effect path 24A mainly through ring R and magnet poles P1 and P2, including air gaps on either side of ring R that vary inversely to each other in separation distance and permeability when the armature moves axially, and a voice-coil-effect path 24B horizontally through shell 12 and vertically through air gaps of substantially constant separation distance and permeability containing the central portion of coils C1 and C2.
In the absence of current in the coils C1 and C2, the flux paths from the magnets tend to balance overall and in effect cancel each other, thus there is virtually no axial driving force applied to the armature from either voice coil or solenoid effect when it is located in the central position shown, where the permanent magnet forces on the armature are balanced. However the centering forces provided by end springs S1 and S2 are necessary to overcome the negative spring effect of the solenoid mode caused by a magnetic attraction between ring R and the closer one (P1 or P2) of the two poles, whenever the armature becomes offset from center.
When electrical current is applied to the coils C1 and C2, flux paths 24C and 24D (dashed lines) are set up having polarity as indicated by the arrow heads due to the direction of current in the coils C1 and C2. Combining flux paths 24C and 24D from coil C1 with the magnet solenoid-effect flux path 24A, it is seen from the direction of the arrow heads that paths 24A and 24D are additive in region A, while the paths 24A and 24C are subtractive in region B: the net effect of this unbalance is a solenoid-effect force F1 acting axially to move the armature to the left as indicated.
The voice-coil-effect flux path 24B traversing vertically through coils C1 and C2 reacts with the current in the coils to create a voice-coil-effect axial force on each coil, and thus a reaction on the stator portion, that exerts a voice-coil-effect reaction force F2 on the armature in the same axial direction as the solenoid-effect force F1, thus the solenoid effect and the voice coil effect combine additively to drive the actuator.
When the coil current is reversed, all the forces reverse accordingly, driving the armature in the opposite direction, i.e. to the right. Thus the armature can be driven to vibrate at the frequency and amplitude of AC applied to the coils.
From a design viewpoint, the force output spectrum of the actuator can be manipulated in a desired manner in design by a judicial balance between the voice coil effect and the solenoid effect; also the efficiency can be optimized through careful selection of materials in the magnetic circuit, the dimensions of the coils and the suspension characteristics.
FIG. 4 is a cross-sectional representation of an active vibration actuator of the present invention in a generalized moving-magnet embodiment illustrating how the basic embodiment of FIG. 3 can be expanded to any multiple by the addition of coils, magnets and rings. Coils C1 . . . Cn are seen to alternate in polarity as indicated by the current symbols I1 (0) and I2 (X) and are seen to fill corresponding adjacent annular channels separated by rings R2, R3, etc . . . of magnetically permeable material. Functionally, these channels could be formed integrally as part of iron shell 12, e.g. by casting or machining; however, for practical reasons to facilitate assembly, the channels are formed by making the rings R2, R3 . . . as separate parts that are inserted into shell 12 along with coils C1 . . . Cn.
End rings R1 and Rn+1 are an optional design choice in any single or multiple configuration; for example, these could be added to the single magnet embodiment of FIG. 3 at the spaces seen at the outer edges of coils C1 and C2. Adding end rings strengthens the solenoid effect and thus alters the proportions of the voice coil and the solenoid effects in the overall performance characteristic. The option of omitting or including end rings, along with the option of magnetic or non-magnetic material in end plates E1 and E2, provide four steps of such proportioning available for design/manufacturing customizing; further modification is available through selection of springs S1 and S2.
As indicated in FIG. 4, for n coils there will be n-1 magnets, n armature pole pieces. As with a single unit there can be n+1 stator rings (with end rings) or n-1 stator rings (no end rings), furthermore, in a multiple unit one or more additional rings could be omitted as a design/manufacturing option: if all rings were omitted, the actuator would operate entirely in a voice-coil mode as in FIG. 1.
The magnetic influence of end rings is shown by the magnetic flux paths shown on magnet M1: in addition to solenoid-effect path 24A and voice-coil-effect path 24B, as described above in connection with FIG. 3, there is an additional solenoid-effect path 24E extending from magnet pole P1 to the left, passing through ring R1 into shell 12, through ring R2 to pole P2 and thence returning to pole P1 through magnet M1. It is seen that when current is applied to the coils, the total flux in regions A increases due to addition while the total flux in regions B decreases due to subtraction, thus contributing further to the solenoid-effect force F1 as part of the overall force F1+F2 moving the armature to the left. When end plate E1 is made of iron, there will be an additional path similar to path 24E extending further to the left and passing through a portion of the end plate El, thus contributing further to the solenoid-effect. For long armature strokes, associated with low frequencies and high armature mass, the end plates E1 and E2 may be made of non-magnetic material. For short strokes, the end plates can be made of iron and made to conduct magnetic flux sufficiently so that the end rings could be eliminated. For low magnet spring modulus, the designer has the option of omitting one or more of the iron rings.
Flux paths such as path 24E and mirror images thereof are also in effect around each of the (non-end) iron rings R2 . . . Rn.
As with the single-magnet embodiment of FIG. 3, end springs S1 and S2 may be selected for spring modulus and its determining effect on the natural resonant frequency of the vibrating armature, along with the mass of the armature which will depend on n-1, the number of magnets.
FIG. 5 shows an alternative generalized multiple embodiment wherein n coils with n+1 prominent poles are incorporated in the armature and n-1 annular permanent magnets with n prominent poles are located inside the stator shell, surrounding the armature. In simplest form there could be a single coil and two permanent magnets.
FIG. 6 depicts a variation of the basic embodiment shown in FIG. 3 with end rings R1 and R3 added and with the armature suspended at both ends by special flexure assemblies 26, which along with optional coil springs S1 and S2, also act as an elastic end stop or bumper. Flexure assemblies 26 each consist of a resilient surround support 26A into which are molded one or more, typically two spring strips 26B spanning diametrically across surround support 26A. Each flexure assembly 26 is secured to the armature by a corresponding screw 28 traversing spring strips 26B and threaded into the corresponding end of armature shaft 16 as indicated by the dashed hidden outlines.
FIG. 7 is a an end view of a flexure assembly 26 shown in FIG. 6, formed from a pair of similar cross-straps 26B of spring steel each with both ends molded into surround support 26A which is molded from resilient material such as high temperature silicon rubber which may be reinforced with Kevlar fiber. An outer flange of support 26A is constrained in an annular channel formed or machined in the corresponding end plate E1, E2 (refer to FIG. 6).
FIG. 7A is a cross-sectional view of flexure assembly 26 taken through axis 7A--7A' of FIG. 7. Cross strap 26B is shown in its normal unbent state, corresponding to the armature at rest at the center of its travel range. The ends of cross-straps 26B are embedded integrally in surround support 26A, typically in a molding process.
FIGS. 7B and 7C show the cross-section of flexure assembly 26 of FIG. 7A with the cross strap 26B bending in two opposite directions corresponding to axial offsets of the armature at the two opposite extremes of its travel range when vibrating. The resilience of surround support 26A accommodates changes in the length of the cross-straps 26B due to arching.
FIG. 8 shows graphically the effect of the iron stator rings (R1 . . . Rn+1, FIG. 4) that are key elements of the present invention. In the graph showing force generated by an actuator as a function of frequency (spectrum) the present invention, curve 28 shows the response with the iron rings in place, compared to curve 30 with the iron rings removed so as to cause the actuator to operate entirely in a voice coil mode as in FIG. 1.
The predominant peak seen in both curves is due to mechanical spring-mass resonance. Curve 28 shows two important advantages over curve 30; a lower resonant frequency, and higher operating efficiency and flatter response throughout most of the useful frequency spectrum.
The design freedom enabled by the present invention allows the resonant peak to be shifted as low as desired in the spectrum, even to zero or into the negative frequency domain, thus facilitating design for optimal operation throughout the desired frequency spectrum.
The invention may be embodied and practiced in other specific forms without departing from the spirit and essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description; and all variations, substitutions and changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
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