A anchor for fixation of an artificial or natural ligament or tendon into a drill-hole in the bone. The device features an anchoring member and a clamp member. According to one embodiment, the anchoring member is U-shaped with two arms that are joined at one end, around which the transplant is passed. The clamp member is designed to be placed between the two arms of the anchoring member or one arm and the wall of the drill-hole thereby locking the anchor in place in the drill-hole.

1. Field of the Invention
Embodiments of the present invention are related to orthopaedic surgical devices, such as implants, and procedures using the implants. More particularly, embodiments of the present invention are directed to surgical devices involved in replacing, reconstructing or securing synthetic or biological connective tissue to a bone surface, such as, for example, attaching and maintaining a replacement anterior cruciate ligament (ACL) against a bone.
Embodiments of the present invention particularly relate to surgical implants manufactured of biocompatible (permanent or bioabsorbable) material, e.g., plastic, metal, or bioabsorbable (or biodegradable) polymer, copolymer, polymer alloy or composite and which implants are used for fixation of a synthetic or biological (connective tissue) graft into a drill-hole in a bone. Grafts according to the present invention include natural (auto- or allograft) and/or synthetic substitutes to ligament or tendon. Synthetic implants according to the present invention may be ceramic and/or polymeric and include fibrous braid implants or other implants comprised of fabric.
2. Description of Related Art
Reconstruction is the standard of care after anterior cruciate ligament (ACL) injury. In surgery it is generally known to use an autograft taken e.g., from the knee of the patient, to replace the ruptured ACL. The two most commonly used are the bone-patellar tendon bone (BPTB) and the hamstring tendon (semitendinosus tendon with or without gracilis tendon), although allografts, synthetic grafts and quadriceps tendon grafts have also been used as ACL substitutes. The surgical techniques of the ACL reconstruction using bone-tendon bone (BTB) graft and hamstring tendon graft are described in detail in the following references: Beck, C. L., Jr.; Paulos, L. E.; Rosenberg, T. D.: xe2x80x9cAnterior cruciate ligament reconstruction with the endoscopic technique,xe2x80x9d Operative Techniques in Orthopaedics, 2:96-98, 1992; Stxc3xa4helin, A. C.; Weiler, A.: xe2x80x9cAll-inside anterior cruciate ligament reconstruction using semitendinosus tendon and soft threaded biodegradable interference screw fixation,xe2x80x9d Arthroscopy, 13:773-779, 1997; Fu, F. H.; Ma, C. B.: Anterior Cruciate Ligament Reconstruction Using Quadruple Hamstring. Operative Techniques in Orthopaedics, 9:264-272, 1999. Additional references of interest include Hoffman, R. F. G.; Peine, R; Bail, H. J.; Sudkamp, N. P.; Weiler, A.: xe2x80x9cInitial fixation strength of modified patellar tendon grafts for anatomic fixation in anterior cruciate ligament reconstruction,xe2x80x9d Arthroscopy, 15:392-399, 1999.
In brief, the ruptured ACL is removed and drill-holes are made into the distal femur and proximal tibia into or into close vicinity of the original insertion sites of the ACL. The replacement substitute (graft) is harvested either from the patellar tendon (BTB) or from the semitendinosus- and gracilis muscle tendons (hamstring graft), pulled through the drill-holes to replace the ruptured ACL and finally fixed into these drill-holes, leaving the tendon part to act as a new ACL.
Rigid fixation of the ACL graft has been recognized as one of the most important factors that determine the long-term success of an ACL reconstruction (Kurosaka, M; Yoshiya, S; Andrish, J T: xe2x80x9cA biomechanical comparison of techniques of graft fixation in anterior cruciate ligament reconstruction, Am. J. Sports Med., 15:225-229, 1987; Brand, J., Weiler, A., Caborn, D. N. M., Brown, C. H. Johnson, D. L.: xe2x80x9cCurrent Concepts: Graft Fixation in Cruciate Ligament Reconstruction.xe2x80x9d Am. J. Sports Med. 28: 761-774, 2000). Further, the tibial fixation of hamstring tendon grafts is considered more problematic than femoral fixation (Larson, R.: xe2x80x9cFixation techniques for hamstring and other soft tissue ACL grafts. The science: Comparative laboratory and clinical studies,xe2x80x9d Proceedings of the Specialty Day, the American Orthopaedic Society for Sports Medicine p. 99-102, Orlando, Fla., Mar. 18, 2000; Brand, J., Weiler, A., Caborn, D. N. M., Brown, C. H. Johnson, D. L.: xe2x80x9cCurrent Concepts: Graft Fixation in Cruciate Ligament Reconstruction.xe2x80x9d Am. J. Sports Med. 28: 761-774, 2000), mainly because the forces are subjected to the ACL substitute (graft) parallel with the tibial bone tunnel and the bone quality is substantially inferior in the tibia than in the femur.
Among the currently available soft tissue (hamstring) graft fixation implants, interference technique, in which the so called interference screw is inserted into the space between the drill-hole and the end of the graft to lock the graft into the drill-hole, is currently the most commonly used method to secure an ACL substitute to a bony drill-hole in an ACL reconstruction. The fixation screws, like interference screws, are normally made of metal, like stainless steel or titanium or of a bioabsorbable polymer, like polylactide. Metallic and/or bioabsorbable polymeric materials and composites suitable for manufacturing of fixation screws, are described in the literature (Vainionp{umlaut over (aa)}, S.; Rokkanen, P.; Txc3x6rmxc3xa4lxc3xa4, P.: xe2x80x9cSurgical Applications of Biodegradable Polymers in Human Tissues.xe2x80x9d Progr. Polym. Sci., 14:679-716, 1989; Weiler, A.; Hoffman, R. F. G.; Stahelin, A. C.; Helling, H. J.; Sudkamp, N. P.: Biodegradable Implants in Sports Medicine: The Biological Base. Current Concepts Arthroscopy 16:305-321, 2000).
During interference screw insertion, technical complications such as the threads of the screw damaging the graft or passing sutures, the graft rotating with the screw so that the optimal position of the graft is lost and/or the graft is damaged or the screw becomes inserted non parallel (divergent) to the graft thereby significantly decreasing the strength of fixation, often occur. There are also concerns specific to the metal interference screws. For example, in case of a need for revision surgery, metal screws can significantly complicate the operation, as the hardware inserted in the primary reconstruction has to be removed, sometimes resulting in considerable loss of bone in the fixation site, and thus, decreasing the strength of the fixation of the revised graft. In most severe cases, it may even be necessary to perform bone grafting prior to revision surgery (Brown, C. H.; Steiner, M. E.; Carson, E. W.: xe2x80x9cThe uses of hamstring tendons for anterior cruciate ligament reconstruction: Technique and results,xe2x80x9d Clin. Sports Med., 12:723-756, 1993; Schroeder, F. J.: xe2x80x9cReduction of femoral interference screw divergence during endoscopic anterior cruciate ligament reconstruction,xe2x80x9d Arthroscopy, 15:41-48, 1999). Metal screws have also been shown to disturb postoperative MRI evaluation (Shellock, F. G.; Mink, J. H.; Curtin, S.; Friedman, M. J.: xe2x80x9cMR imaging and metallic implants for anterior cruciate ligament reconstruction: assessment of ferromagnetism and artifact,xe2x80x9d J. Magn. Reson. Imaging, 2:225-228, 1992). The problems specific to metal screws can naturally be avoided by the use of screws made of bioabsorbable materials, but other problems arise, such as the bioabsorbable screw breaking during screw insertion. Also, the drill-hole has to be threaded for the insertion of the bioabsorbable screw, which not only delays surgical operation, but also increases trauma and removes mechanically stronger cortical bone, thus reducing the grip of the screw into the bone. Complications associated with the surgical technique, like those listed above, are also provided in the literature (Bach, B. R.: xe2x80x9cArthroscopy-assisted patellar tendon substitution for anterior cruciate ligament insufficiency,xe2x80x9d Am. J. Knee Surg., 2:3-20, 1989; Barber, A. F.; Buxton, E. F.; McGuire, D. A.; Paulos, L. E.: xe2x80x9cPreliminary results of an absorbable interference screw,xe2x80x9d Arthroscopy, 11:537-548, 1995; Matthews, L. S.; Soffer, S. R.: xe2x80x9cPitfalls in the use of interference screws for anterior cruciate ligament reconstruction: Brief report,xe2x80x9d Arthroscopy, 5:225-226, 1989; Matthews, L. S.; Lawrence, S. J.; Yahilo, M. A.; Sinclair, M. R.: xe2x80x9cFixation strength of patellar tendon-bone grafts,xe2x80x9d Arthroscopy, 9:76-81, 1993; Pierz, K.; Baltz, M.; Fulkerson, J.: xe2x80x9cThe effect of Kurosaka screw divergence on the holding strength of bone-tendon-bone grafts,xe2x80x9d Am. J. Sports Med., 23:332-335, 1995; Rupp, S.; Krauss, P. W.; Fritsch, E. W.: xe2x80x9cFixation strength of a biodegradable interference screw and a press-fit technique in anterior cruciate ligament reconstruction with a BPTB graft,xe2x80x9d Arthroscopy, 13:61-65, 1997; Safran, M. R.; Harner, C. D.: xe2x80x9cTechnical considerations of revision anterior cruciate ligament surgery,xe2x80x9d Clin. Orthop., 323:50-64, 1996).
Finally, although providing a possibility for a bioabsorbable and apertural (anatomic) fixation of the ACL substitutes and despite their adequate initial fixation strength in pull-out studies, interference technique has been shown to result in early slippage or even complete failure of the graft-anchor-bone complex during cyclic loading of hamstring grafts fixed interference screws (Giurea, M., Zorilla, P. Amis, A. A., Aichroth, P.: xe2x80x9cComparative Pull-Out and Cylic-Loading Strength Tests of Anchorage of Hamstring Tendon Grafts in Anterior Cruciate Ligament Reconstruction.xe2x80x9d Am. J. Sports Med. 27: 621-25, 1999; Havig, M. T.; Paulos, L. E.; Weiss, J.; Ellis, B. S.; Bote, H.: xe2x80x9cInterference screw fixation of soft tissue ACL grafts: Effects of cyclic loading on initial fixation strength,xe2x80x9d Proceedings of the Specialty Day, the American Orthopaedic Society for Sports Medicine, p. 28, Anaheim, Calif. Feb. 7, 1999; Van der Reis, W. L.; Deffner, K. T.; Rosenberg, T. D.: xe2x80x9cComparison of hamstring fixation devices under cyclic loading,xe2x80x9d Proceedings of the Specialty Day, the American Orthopaedic Society for Sports Medicine, p. 88, Orlando, Fla., Mar. 18, 2000; Brand, J., Weiler, A., Caborn, D. N. M., Brown, C. H. Johnson, D. L.: xe2x80x9cCurrent Concepts: Graft Fixation in Cruciate Ligament Reconstruction.xe2x80x9d Am. J. Sports Med. 28: 761-774, 2000).
Because of complications found in clinical use of interference screws, several attempts have been done to develop other types of anchoring devices for fixation of synthetic or natural ligaments or tendons in ACL reconstruction. For example, free tendon grafts can be fixed outside the drill-holes using either staples, screws and washers, so-called endobuttons, or tying sutures over buttons or screw posts.
Extra-articular or suspensory fixation methods, for example, methods that require fixation outside the bone tunnel such as is found with staples placed either on the anterior cortex of the tibia or implants with staples placed partially within an entrance opening of the tunnel, are another commonly used alternative to fix soft tissue grafts into bone drill-holes. Although these methods have been shown to provide superior fixation strengths to the interference technique, they require at least that a portion of the implant be exterior to the drill-hole. Further, in comparison to the apertural fixation methods, the stiffness of the suspensory methods has been shown to be clearly inferior (Ishibashi, Y; Rudy, T. W.; Livesay, G. A.; Stone, J. D.; Fu, F. H.; Woo, S. L.: xe2x80x9cThe effect of anterior cruciate ligament graft fixation site at the tibia on knee stability: Evaluation using a robotic testing system,xe2x80x9d Arthroscopy, 13:177-182, 1997). Suspensory or extra-articular fixation of grafts has also been accused of permitting micromotion of the individual tendons of the four-strand graft within the bone tunnel, which in turn, has been associated with the enlargement of the bone tunnels, increased AP-laxity and decreased stiffness of the reconstruction, possibly jeopardizing the success of the operation (Hoher, J., Moller, H. D., Fu, F. H. xe2x80x9cBone Tunnel Enlargement after Interior Cruciate Ligament Reconstruction: Fact or Fiction?xe2x80x9d Knee Surg. Sports Traumatol. Arthrosc. 6:231-240, 1998).
Crossbar or toggle fixators are the latest in the fixation implants developed to secure tendon graft in bone tunnel. In short, the basic principle of these implants is that the tendon(s) is/are looped over a crossbar/toggle-like structure placed in the bone drill-hole. To date, these devices have been designed for the femoral fixation of hamstring grafts, with two exceptions:
UK Pat Appl. GB 2 288 739 describes an anchor for anchoring a ligament or the like at or adjacent one end of a bone or channel in a bone, comprising a head portion and a near portion adapted to extend into the bone or channel and to receive the ligament. Even if this implant can be applied for fixation (anchoring) a ligament, it has the head portion which remains outside of the drill-hole on the surface of bone. This portion, located on bone surface, causes tension in soft-tissue on bone. This tension can cause irritation, pain and foreign body reactions (swelling or oedema) in soft tissue. The head portion may also be palpable below the skin, which is inconvenient for the patient. Further, this implant does not provide an anatomic fixation or enable the tensioning of the graft.
A more advanced version of the same principle has been described in GB 2,337,463, which is otherwise very similar to the device described in GB 2,288,739 except of having the means for holding the ligament under tension, and then, when appropriate tension is achieved, maintaining the desired tension by a locking means comprising of a crimpable washer and a lock nut. Although enabling the tensioning of the graft, this design is also not endosteal (intraboreal) and does not provide an anatomic fixation.
U.S. Pat. No. 5,632,748 describes an endosteal anchoring device for urging a ligament graft against a bone surface comprising an anchoring body, a member for resisting slippage of the anchoring body into the periphery of a bone tunnel under ligament tension, a member for avoiding puncturing, piercing or tearing of cross-fibers of the ligament graft and a member for urging the ligament graft flush against the inner surface of the bone tunnel for accelerated healing. This device can be located totally inside of the drill-hole of bone. However, this device is bulky because (a) the anchor member, (b) the ligament graft, which is encircled around the anchor member and positioned within the cross-sectional area of the groove on the anchor member and (c) the insertion member (which in combination with the anchor member provides a means of locking the ligament graft at a fixation site) all are located side by side inside of the drill-hole. Therefore a substantial amount of the drill-hole is filled with the device (anchor member+insertion member) and typically less than half of the space inside of drill-hole is left for the ligament graft, as can be seen from FIG. 1, FIG. 3, FIG. 6, FIG. 8 or FIG. 9 of U.S. Pat. No. 5,632,748. When the device is bulky in comparison to the ligament it means that a large amount of degradable foreign material is located near the ligament. Accordingly, the diameter of the drill-hole must be substantially larger than the diameter of the ligament. Also a large amount of foreign material means a large amount of polymer debris degrading in the vicinity of the ligament, resulting in an increasing risk for compromised healing of the ligament.
FI. Pat. No. 100217 B describes an implant for fixation of a tendon loop in ACL reconstruction. The implant comprises the first end which includes a hole through which a tendon has been slipped to form a loop and a transverse locking element for locking of the implant into the drill-hole inside of bone. The implant further comprises a base member which includes a fixation notch for inserting an installation instrument. Even if this fixation implant will be located totally inside of the drill-hole into the bone, the installation of the transverse locking element is difficult and causes the formation of additional trauma (wound into the soft tissues and an additional transverse hole into the bone)
U.S. Pat. No. 5,425,767 describes an anchor for an artificial ligament in a bone. The anchor comprises a Y-shaped socket having first and second arms angled with respect to each other. The first arm is sized to receive the ligament and has cross-grooves for gripping the ligament. A bullet shaped clamp element is rotatably mounted to the second arm. The clamp element also has grooves that directly contact the ligament to apply an oblique force against the ligament. The clamp element and cross-grooves in the first arm completely surround and compress the ligament to frictionally secure the ligament to the socket. This implant is bulky, because of the intersecting openings (the Y-shape) of the socket. Therefore the opening of the drill-hole in the bone must be significantly larger than the drill-hole deeper inside of bone. A larger drill-hole opening means increased trauma to the bone surface. Additionally the clamp element compresses the ligament, which may cause similar problems for the ligament as found with the fixation of a ligament with an interference screw.
U.S. Pat. No. 5,899,938 describes a graft ligament anchor comprising a graft ligament engagement member disposed in an opening in a bone, the graft ligament engagement member being arranged to receive a graft ligament alongside the engagement member, and a locking member for disposition in the opening, and at least in part engageable with the graft ligament engagement member. Movement of the locking member in the opening causes the locking member to urge the engagement member, and the graft ligament therewith, toward a wall of the opening to secure the graft ligament to the wall of the opening. Also in this case the compressing of the ligament may cause problems by damaging the ligament and/or by disturbing its nutrition and healing.
As illustrated by the foregoing summary, efforts are continuously being made to improve devices, instruments and surgical methods used in replacing and reconstructing torn or dislocated ligaments so as to make the process more efficient and effective. However, significant disadvantages still remain with all the presently known devices and methods offered by the prior art.
Accordingly it would be advantageous to overcome the disadvantages of the prior art and to design an implant for use in securing a transplant, such as a hamstring tendon graft, in a bone, such as a tibia, that would: (a) be bioabsorbable; (b) provide a rigid fixation of the transplant at the tunnel opening (apertural/anatomic fixation); (c) have no external hardware, i.e. the implant should be a completely intraboreal or endosteal design such that no part of the implant should protrude outside the bone drill-hole or be located on the outer surface of the tibia; (d) require no additional surgical trauma in addition to the single drill-hole in the tibia as would occur with additional drill-holes or additional skin incisions, etc.; (e) permit/provide a circumferential contact, i.e. ideally 360xc2x0 contact, between the transplant and bone drill-hole walls, and (f) enable tensioning of the transplant before it is secured into the drill-hole, e.g., by pulling the transplant/implant construct by hand.
Embodiments of the present invention are directed to implants that can be used to secure a graft or transplant, such as a tendon, to bone, and more particularly, within a hole that is drilled into bone, i.e. a so-called xe2x80x9cdrill-holexe2x80x9d. Drill-holes, according to the present invention, can be made into or through a bone. When the drill-hole is made through a bone, it has an entrance opening and a corresponding exit opening. In addition to its ordinary and accustomed meaning, the term xe2x80x9ctransplantxe2x80x9d includes according to specific embodiments an artificial or natural ligament or tendon graft that is used as a reconstruction material to replace a torn/injured ligament, e.g. an anterior cruciate ligament. The implants of the present invention may also be referred to herein as xe2x80x9canchorsxe2x80x9d as they anchor or secure the transplant to the bone. The anchors are designed to be placed completely within a drill-hole with no part of the anchor protruding beyond the surface of the bone adjacent to the opening of the drill-hole once it has been properly implanted. Stated differently, the anchor is absent from the surface of the bone after the implantation surgery.
The anchor of the present invention includes an anchoring member and a clamp member. The anchoring member includes an anchor element and a locking element connected to the anchor element, preferably in series relation. The anchor element is configured to retain the transplant such as by allowing the transplant to loop around the anchor element. According a certain embodiment of the invention, the anchor element may include a groove, hole or other opening through which the transplant may be slid or inserted and then looped around the anchor element. However, the anchor element may include a wide variety of other configurations to retain a transplant such as the anchor element being uni- or multi-compartmental and including a slot, a hole, a hook, one or more tabs or extensions or other types of a recess through or around which a transplant can be looped.
The portion of the anchor element forming the groove, hole or other opening has a surface area and is configured so as to allow the transplant to be looped without any substantial compression, crimping, cutting or other deleterious effect on the transplant. According to a certain embodiment, the surface area is smooth and free from structure which would abrade or otherwise damage the transplant. The transplant, when looped, is co-extensive with a portion of the length of the anchor element. The anchor element around which the transplant is looped advantageously serves to encourage contact between the wall of the drill-hole and the transplant, and in particular, at the intra-articular opening of the drill-hole, to facilitate healing and securing of the transplant to the bone. The anchor element around which the transplant is looped is configured so as to exclude excessive compression of the transplant against the wall of the drill-hole.
However, the transplant, when looped, is advantageously non-extending along the entire length of the anchoring member. That is, according to the present invention, the anchoring member is configured such that the transplant need not extend along the entire length of the anchoring member, but rather can be fixedly retained within a drill-hole by being looped around only a portion of the anchoring member, such as the anchor element, with the remaining portion of the anchoring member, such as the locking element, being free of transplant contact.
The locking element extends as one or more arms from the anchor element and, in certain embodiments of the invention, includes frictional elements that frictionally engage a wall of the drill-hole. Thus, the locking element serves to prevent the anchoring member from slipping out of the drill-hole. A clamp member is provided which engages the anchoring member to provide further frictional force between the anchoring member and the wall of the drill-hole and to further secure or xe2x80x9clockxe2x80x9d the anchoring member within the drill-hole. The clamp member is designed to engage the anchoring member within the drill-hole with no part of the clamp member protruding beyond the surface of the bone adjacent to the opening of the drill-hole. Stated differently, the clamp member, when fully engaged with the anchoring member once proper fixation has been achieved, is absent from the surface of the bone.
According to certain embodiments of the present invention, the locking element is generally cylindrical in design and has a width or diameter that is equal to or slightly less than the diameter of the drill-hole so as to provide for a snug fit of the anchoring member into the drill-hole while still facilitating ease of adjusting the anchoring member within the drill-hole. Although it can be, the diameter of the drill-hole need not be any larger than the width or diameter of the locking element because the transplant does not contact the locking element at a position where the locking element contacts the wall of the drill-hole. Also, the locking element itself may be fashioned from compressible materials allowing its insertion into a drill-hole having substantially the same diameter as the locking element.
According to certain embodiments of the present invention, the locking elements are free from transplant contact. The transplant is not present between the wall of the drill-hole and the locking elements, i.e. the locking elements make direct contact with the wall of the drill-hole. Since the transplant is coextensive with only a portion of the anchoring member, such as the anchor element, any contact between the transplant and degraded material from the anchoring member is advantageously minimized.
In view of the foregoing, it is an object of the present invention to provide an ACL reconstruction fixation implant or anchor for fixation of tendon or synthetic grafts inside of a drill-hole. The implant is safe and simple to insert into a drill-hole with minimal trauma.
Another object of the present invention is to provide a device which is manufactured of biocompatible (permanent or bioabsorbable) material, e.g., plastic, metal, or bioabsorbable (or biodegradable) polymer, copolymer, polymer alloy or fiber reinforced or particle filled bioabsorbable polymer composite, which implant could be inserted into a drill-hole made into a bone, to fixate an ACL graft into the drill-hole.
It is also an object of the present invention to provide an ACL reconstruction fixation device which has such a geometry that the implant slips easily into the drill-hole but expresses, when locked into the drill-hole, a strong resistance against slip-in or pull-out from the drill-hole.
It is another object of the present invention to provide a device for fixing an ACL graft into a bone, which does not interfere with non-invasive examinations (such as radiographs, MRI or CT), is biocompatible and results in/provides a strong and rigid fixation of a graft in ACL reconstruction.
Further, it is an object of the present invention to provide an ACL reconstruction fixation device that does not damage the graft and minimally disturbs the tissue metabolism and blood circulation, when located totally inside of a drill-hole in a bone so that no part of the implant protrudes the outer surface of the bone.
It is a still further object of the present invention to provide an ACL reconstruction fixation device which locks the tendon loop effectively inside of the drill-hole with minimal contact between the tendon and the device, thus enabling maximal filling of the drill-hole with the tendon substance and facilitating effective growth of tendon tissue to contact with the walls of the drill-hole.
It is also a still further object of the present invention to provide an ACL reconstruction fixation device which presses the individual (tendon) bundles of the graft firmly against the walls of the drill-hole at or near the intra-articular tunnel opening (apertural/anatomic fixation).
Consistent with the foregoing objects, and in accordance with the invention as embodied and broadly described herein, a permanent or bioabsorbable intraboreal (endosteal) graft fixation anchor for being simply and safely inserted into a hole or drill canal made into a bone, to securely fix a tendon graft (transplant) into the drill-hole, the anchor device comprising an anchoring member and a clamp member, the anchoring member including an anchor element for holding a loop of a transplant and a locking element to engage a clamp member in a manner to secure or lock the anchor within a drill-hole. The anchor device provides for the rigid fixation of the transplant against the walls of the drill-hole at or near the intra-articular tunnel opening to facilitate the healing of the transplant.


Injection molding method and apparatus for repeatedly performing an injection molding cycle including the steps of closing and clamping a mold having a mold cavity, injecting a resin material into the mold cavity, cooling and solidifying the resin material filling the mold cavity, and opening the mold so as to remove a molded product, in order to successively form the molded product, wherein a cycle time is measured at a measuring point in the injection molding cycle, and a difference between the measurement of the cycle time and a predetermined reference cycle time is obtained, and then a time compensation on the basis of the difference is executed at a time-controlled step which is arranged to be executed before the next measuring point comes.

This application is based on Japanese Patent Application No. 11-258800 filed on Sep. 13, 1999, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates generally to a method and an apparatus of an injection molding, which are arranged to successively mold articles made of a resin material. More particularly, the present invention is concerned with a novel method and a novel apparatus of an injection molding, which assure a sufficiently high degree of stability of a heat history of the resin material and a temperature of a mold, in every molding cycle, while permitting an execution of a successive injection molding of the resin material with high stability.
2. Description of the Related Art
As one type of an injection molding machine, there is known an injection molding machine, such as an inline-screw-type injection molding machine, a plunger-type (torpedo-type) injection molding machine and a preplasticating injection molding machine, wherein an injection screw or plunger which is reciprocally movably disposed in a bore of a heating cylinder is rotated so that a resin material is heated to be molten and metered in the heating cylinder. Successively, the injection screw or plunger is moved so as to inject the resin material into a mold cavity of a mold which is clamped by a suitable clamping device. The resin material filling the mold cavity is held within the cavity under a predetermined holding pressure and then cooled for a predetermined period of time. Then, the mold is opened and the molded product is ejected or released from the mold cavity, thereby obtaining a desired molded product. Such an injection molding machine is operated to perform repeatedly a cycle of molding operations so as to successively form a multiplicity of desired products.
In order to produce successively the desired products with a desired good quality, by means of the injection molding machine, there is required that a molding condition is kept substantially constant in every molding cycle. In particular, it is important that a heat history of the resin material and a temperature of the mold are kept substantially constant in every molding cycle.
However, one molding cycle includes various kinds of steps such as a cooling step wherein a time of the step is controlled, a mold closing and opening step wherein an operation velocity of the injection molding machine is controlled by adjusting an amount of discharge of a hydraulic pump, and an injection step wherein an injection pressure or a position of the injection screw are controlled. Therefore, it is difficult to keep the injection molding condition substantially constant, and a conventional injection molding machine inevitably is likely to suffer from variation in heating conditions and heating times of the resin material or the mold, leading to difficulty in keeping the heat history of the resin material and the temperature of the mold substantially constant in the every molding cycle, upon performing the above-indicated successive injection molding. Due to this drawback, the conventional injection molding machine may be insufficient in attaining a desired degree of stability in quality of the products, depending on kinds of the products.
It is therefore a first object of the present invention to provide a method of injection molding for successively producing a resin product by repeatedly performing an injection molding cycle, which method permits a high degree of stability of molding conditions in terms of a heat history of a resin material and a temperature of a mold, in every molding cycle, thereby permitting successive production of the resin products with a stabilized quality thereof.
It is a second object of the invention to provides an injection molding apparatus which is novel in construction and which permits that molding conditions such as a heat history of a resin material and a temperature of a mold are kept substantially constant, during its successive injection molding operation, thereby permitting a successive production of desired resin products with a stabilized quality thereof.
The first object may be achieved according to a first aspect of this invention, which provides a method of injection molding for repeatedly performing an injection molding cycle including the steps of closing and clamping a mold having a mold cavity, injecting a resin material into the mold cavity, cooling and solidifying said resin material filling the mold cavity, and opening the mold so as to remove a molded product, in order to successively form the molded product, the method comprising the steps of: (a) measuring a cycle time at at least one measuring point in the injection molding cycle to thereby obtain a measurement of the cycle time; (b) obtaining a difference between the measurement of the cycle time and a predetermined reference cycle time; and (c) executing a time compensation on the basis of the difference at a time controlled step which is arranged to be executed before the next measuring point comes.
In the injection molding method according to the first aspect of the invention, the entire time required to execute one injection molding cycle is suitably controlled to be made substantially constant, although the injection molding cycle includes steps which are not controlled based on time. Therefore, the present method is capable of restricting or reducing an amount of variation in the cycle time of each injection molding cycle, making it possible that a period of time required from a current injection action to a next injection action is kept substantially constant. Thus, the present method permits a substantially constant molding conditions in terms of the heat history of the resin material and the temperature of the mold, in the every molding cycle.
For the above reasons, the present injection molding method assures an improved stability in quality of the products formed by the successive injection molding, while effectively attaining a sufficiently reduced ratio of reject of the molded product and an improved yield of the molded product.
It is noted that the measuring point for measuring the cycle time may be previously fixed to a point or points in the injection molding cycle, but not particularly limited. For instance, the measuring point may preferably be set to any point in the cycle at which an electric signal is generated. In this case, the electric signal is advantageously utilized to measure the cycle time. More specifically, the measuring point is set to a point in the cycle at which the injection molding cycle changes its steps. Namely the point may preferably be an initiation or a completion point of a mold clamping operation, an initiation or a completion point of an injection operation, for example. In this respect, the electric signal may be an output signal of a positioning sensor like a limit switch, an output signal of a timer or a time counter, for example.
The reference cycle time may be set to a desired value by a manual operation. It is preferable that the cycle time is timed in every molding cycle and if a desired product is obtained, then the timed cycle time is set as the reference cycle time. It is noted that the reference cycle time may be suitably changed taken into account molding conditions or the like.
The time compensation based on the obtained difference between the measurement of the cycle time and the reference cycle time may be executed at any one or more of the time controlled step(s) in the injection molding cycle. In this respect, the time controlled step should be interpreted as a step wherein a time or period of the step is controlled. For an effective time compensation, the time compensation is executed as follows: In this case where an injection molding cycle includes a plurality of measuring points for measuring the cycle time, if the difference is obtained in a current measuring point, then the time compensation based on the obtained difference should be executed until the next measuring point comes. In this case where an injection molding cycle include one measuring point for measuring the cycle time, if the difference is obtained in the measuring point in the current cycle, then the time compensation based on the obtained difference is executed until the measuring point in the next cycle comes.
In one preferred form of the method of the present invention, the time controlled step at which the time compensation is executed, may be selected from the group consisting of (i) an injection delay time after the step of clamping the mold is completed and before the step of injecting the resin material is initiated, (ii) a cooling time after the step of injecting the resin material is completed and before the step of opening the mold is initiated, and (iii) an intermediate time after the step of opening the mold is completed and before the step of closing the mold is initiated.
In the above preferred form of the method, the time compensation can be effectively executed in the above-indicated time controlled steps (i), (ii), (iii), so that the difference between the measurement of the cycle time and the reference cycle time is effectively compensated or zeroed in these time controlled steps, while an adverse effect of the time compensation on the molded product is effectively minimized or avoided.
It is required that at least one measuring point is set in an optional point in the injection molding cycle. Preferably, a plurality of measuring points (e.g., two, more preferably three or more measuring points) are set in respective points in the cycle. In this case, the method is desirably arranged such that the differences between the measurement of the cycle time and the reference cycle time are detected at respective measuring points, and the time compensation based on the respectively detected differences are executed at the different time controlled steps. In this arrangement, the measurements of the cycle time and the time compensations are executed at the plurality of points in the injection molding cycle. This means that a control of the cycle time can be performed at each time controlled step, resulting in an improved accuracy of the control of the cycle time, and a resultant accuracy of control of the heat history of the resin material and the temperature of the mold. In this arrangement, moreover, an amount of compensation of time to be compensated in one cycle time is effectively divided with the plurality of time controlled steps. This means that an amount of compensation of time in one time compensation action is effectively reduced, thereby reducing adverse effect of the time compensation action on the molded product.
In this respect, it is noted that the time compensation based on the time difference between the measurement of the cycle time and the reference cycle time, which difference is detected in one measuring point, may be executed at one time controlled step in the cycle, or alternatively may be executed at the plurality of time controlled steps in the cycle. The latter case is effective to reduce an amount of compensation of time to be executed in each step, thereby reducing the adverse effect of the time compensation on the quality of the molded product.
In another preferred form of the method, there is determined an upper limit of an amount of compensation of time executed at one time controlled step. In this form of the method of the invention, the presence of the upper limit of the amount of compensation of time is effective to prevent excessively large amount of change in a period of the time controlled step, even in the case where an excessively large amount of difference between the measurement of the cycle time and the reference cycle time is detected in the measuring point, thereby eliminating or minimizing the adverse influence of the time compensation on the operation of the injection molding during the time controlled step. The upper limit of the amount of compensation of time is not particularly limited to the specific value, but may be suitably determined taken into account a tolerable amount of change in the operation time of the time controlled step, a required quality of the product, a degree of influence of the change of the operation time of the time controlled step on the quality of the product, an amount of difference between the measurement of the cycle time and the reference cycle time generated under a standard molding condition, and the like. In a general injection molding apparatus, the upper limit of the amount of the compensation of time is preferably set at about xc2x10.5 second, more preferably, at about xc2x10.2 second.
The second object indicated above may be achieved according to a second aspect of the present invention which provides an injection molding apparatus for repeatedly performing an injection molding cycle including the steps of closing and clamping a mold having a mold cavity, injecting a resin material into the mold cavity, cooling and solidifying the resin material filling the mold cavity, and opening the mold so as to remove a molded product, in order to successively form the molded product, the apparatus comprising: (a) a time counter adapted to count a cycle time at at least one measuring point in the injection molding cycle; (b) a calculator adapted to calculate a difference between the cycle time obtained by the time counter and a predetermined reference cycle time; and (c) a compensating means for executing a time compensation on the basis of the difference calculated by the calculator at a time controlled step which is arranged to be executed before the next measuring point comes.
In the injection molding apparatus according to the second aspect of the present invention, the above-described injection molding method according to the first aspect of the present invention is effectively performed. Therefore, the present apparatus is capable of reducing or eliminating an amount of variation in the cycle time of each injection molding cycle, due to the variation of the operation time of the steps which are not controlled based on time, thereby assuring a high stability of the heat history of the resin material and the temperature of the mold in every molding cycle. This arrangement makes it possible to successively form a desired product with a stabilized quality.
While the time counter, the calculator, and the compensation means may be effectively embodied by utilizing a microcomputer, for example. Such a microcomputer may be a microcomputer used as a controller for controlling injection molding operations of the injection molding apparatus.
In one preferred form of the apparatus of the present invention, the apparatus further comprises a reference cycle time setting means for storing and renewing a measurement of the cycle time as the reference cycle time in a suitable memory device based on an inputted signal applied from an external area.
In this case where the present injection molding apparatus is constituted by utilizing a microprocessor, the actual measurement of the cycle time may be stored in a memory device of the microprocessor as the reference cycle time, based on an input signal applied to an input portion of the microprocessor from an external area. The stored cycle time may be renewed also based on the input signal applied to the input portion. This arrangement permits an easy and rapid setting or adjustment of the reference cycle time. For instance a cycle time which is measured when the injection molding apparatus produces a desired product, can be easily set as the reference cycle time, facilitating setting and renewing an appropriate cycle time.
In another preferred form of the apparatus of the present invention, the apparatus further comprises a switch device for allowing or prohibiting execution of the time compensation in the time controlled step or steps. The provision of the switch device permits optionally selecting execution of the time compensation in the injection molding cycle. Therefore, the time compensation can be prohibited in the case where a precise control of time is required in the time controlled step, for example, whereby the adverse effect of the time compensation on the step can be avoided as needed. In the case where the time compensation is executed at the plurality of time controlled steps, a plurality of the switch devices may be provided for the respective time controlled steps.

Method and apparatus for injection molding wherein cycle time is controlled


A method of making a fluorinated ether includes combining, in a polar aprotic solvent: a fluorinated alcohol represented by the formula X—Rf1CH2OH, and a fluorinated sulfonate ester represented by the formula Rf2CH2OS(═O)2Rf3, and base; and obtaining a fluorinated ether represented by the formula Y—Rf1CH2OCH2Rf2—Y. Rf1 is selected from perfluorinated C1-C10 alkylene groups having from 1 to 10 carbon atoms and partially fluorinated C1-C10 alkylene groups, and derivatives thereof having catenated heteroatom(s). X represents H, F, or an HOCH2— group. Rf2 is selected from perfluorinated C1-C10 alkyl groups and partially fluorinated C1-C10 alkyl groups, and derivatives thereof having catenated heteroatom(s). Rf3 is a C1-C4 alkyl group. Y represents H, F, or an Rf2CH2OCH2— group. A variant method, useful for preparing symmetric fluorinated ethers, is also disclosed. The present disclosure also provides fluorinated ethers preparable according to the methods. Use of fluorinated ethers in various applications is also disclosed.

Various fluorinated ethers are known. The term hydrofluoroether, as used in the art, commonly refers to those ethers having partial substitution of hydrogen atoms by fluorine atoms. Some hydrofluoroethers are commercially available. Examples include those hydrofluoroethers available under the trade designations 3M NOVEC ENGINEERED FLUID 7000, 7100, 7200, 7300, 7500, and 7600 from 3M Company of Saint Paul, Minn.

Methods of making fluorinated ethers, fluorinated ethers, and uses thereof


A barricade to prevent a door from being opened and entry gained by an unauthorized or unwanted person. The doorway security barricade apparatus removably attaches to a door frame and includes a bar which extends across the doorway, bar brackets which attach to the bar, mounting brackets which are attached to the wall and the door frame and receive the bar brackets to mount the security apparatus across the door, and an assembly coupled to the bar which allows a user to apply a positive pressure to the door and restrict movement of the door latch or deadbolt within the door jamb, prevent opening of the door, and restrain against extraordinary external forces applied against an exterior surface of the door.

The present invention relates generally to security devices which act as a physical barrier against unauthorized entry through an entryway. More particularly, the present invention relates to devices which act as restraining barricades to prevent a door from being opened and entry gained by an unauthorized or unwanted person.
Concern for the safety of one's person, residence or business property is an unfortunate fact of daily life. A myriad of apparatus and devices have been devised to increase personal safety as well as the safety of residences and business premises against unauthorized access and intrusion. The present invention is particularly well-suited to assist the homeowner, renter or business owner in securing entry doorways against unauthorized intrusion.
Various types of doorway security devices are known. Such types of doorway security devices include mechanical apparatus such as deadbolt locks, deadbolt latch locks, locking hasps, sliding pins which engage locking recesses, door handle wedge bars, hinge locks and barrier bars, and electronic devices such as electromagnetic switches and infrared sensors. The following patents are representative of types of mechanical apparatus:
The Palmer patent, U.S. Pat. No. 4,082,332, issued in 1978, discloses a security apparatus which comprises a rigid bar and a pair of brackets. A hollow cylinder of resilient foam material surrounds the bar over a short length. The cylinder is positioned to overlie the doorknob side of the door, thus cushioning the shock of the door being forcibly opened. The end of the bar is inserted into and through the closed loop of one bracket and between the inner portion and flange of the J-shaped bracket. The bar may be hung from one of the brackets in a non-operative position by inserting an extension on the bar into an aperture in the bracket.
The O'Neal, et al. patent, U.S. Pat. No. 4,429,911, issued in 1984, discloses a security door bar system in which a rigid bar extends in front of a door between a pair of mounting brackets. One bracket has an elongated slot and the other has a T-shaped slot. The opposite ends of the bar have a reduced diameter and a flange, allowing the bar to axially penetrate, and be restrained by and between, the bracket members.
The Fizer patent, U.S. Pat. No. 5,282,656, issued in 1994, discloses a door security bar system which comprises an adjustable cylinder bar with a self-contained hinge on one end for rotating the bar to the storage position and a locking pin on the other end which restrains the bar when it is in security position. A closed-ended bracket, with an indentation for holding the locking pin, holds the bar in security position and a catcher holds the bar in the storage position. The third bracket allows the bar to rotate. This security bar extends across the width of the door, but does not extend beyond the door molding, as in your device. The brackets do not include pintles or coaxial cylindrical members and the bar does not include an adjustment knob.
The Dameron patent, U.S. Pat. No. 4,779,910, issued in 1988, discloses a self-releasing security bar which device includes a telescoping bar with opposite ends engaging wall brackets. Aligned transverse holes in the bar allow a release pin to maintain the bar in its extended length. When the release pin is pulled, a spring pulls the bar sections to a shorter overall length, permitting the bar to fall away from the mounting brackets.
The Sweet patent, U.S. Pat. No. 5,340,172, issued in 1994, discloses a door security system for use on both inward and outward opening doors. This system includes an elongated telescoping bar that engages both door knobs and docking ferrules incorporated into the opposing door hinges. Door jamb mounting brackets are used for outward opening double doors.
The Hutson patent, U.S. Pat. No. 5,253,905, issued in 1993, discloses a door locking system which engages the door frame on an outwardly opening door and includes a panic bar which moves towards the door for disengaging the locking system. An outer sleeve fixedly mounts to the interior surface of the door and an inner sleeve pulls against a spring to a door frame engagement position.
The Rice patent, U.S. Pat. No. 5,364,140, issued in 1994, discloses a door security device which includes a security bar extending across the surface of the door, opposing blocking members resting against the door frame and an attachment mechanism including J-shaped hooks which engage a portion of the door.
The Teaff patent, U.S. Pat. No. 5,232,254, issued in 1993, discloses a door securing device which consists of a first bracket with a slot and a second hinged bracket with a slot mounted outside the door jambs. The second latch includes a slit which extends around an outwardly extending receiving latch. A security bar, with stops on both ends, extends across the surface of the door and the door jambs and engages the brackets.
The Watson, Jr. patent, U.S. Pat. No. 5,398,982, issued in 1995, discloses a door security bar consisting of an elongated rod with an arcuate handle end. The handle end has a downward extension which is rotatable within a ferrule bar sleeve portion mounted adjacent to the door. The elongated rod is insertable within the floor adjacent to the door.
The Black patent, U.S. Pat. No. 2,882,088, issued in 1959, discloses pin-like connectors for removable cattle racks for vehicles. This patent discloses a hook and eye type connector. An elongated tongue projects forwardly from the body of the hook. A vertical shank extends from the tongue and terminates in a long tapered pin. A bore extends through the body of the hook, allowing the pin to mate with the body of the hook.
The Ellis patent, U.S. Pat. No. 4,014,571, issued in 1977, discloses a locking means for doors and windows. The device consists of a pair of plates. One of the plates is mounted on the back of the door proximate each hinge and the other plate is mounted on the jamb with its angled end portion projecting behind the angled end portion of the plate.
The Schrader patent, U.S. Pat. No. 5,291,760, issued in 1994, discloses a portable lock for doors. The lock consists of a unitary plate, attached to the inner side of a door, with a clamping and locking mechanism. The clamping mechanism is a wing nut and the locking mechanism is a lock cylinder and an opening for insertion of a peg.
Conventional doorways consist primarily of doors which are mounted on hinges to a door jamb. The door jamb is, in turn, mounted into a structural opening in a wall. It is well known in the construction field that when building a wall which is to have a door, an opening is created by framing a door opening of the same structural support material used to make the wall. For example, in typical home construction, interior walls are made of generally horizontally oriented header and toe members and vertical studs, all typically made from wood "two-by-fours" having a nominal transverse cross-sectional dimension of 11/2 inches by 31/2 inches. Door openings in wood framed walls are typically made by framing the lateral aspects of the door opening using two or three "two-by-four" studs positioned adjacent and attached to one another so that their largest lateral dimensions are in abutting relationship. The upper aspect of the door opening is also created by cutting two or three "two-by-fours" to the desired width of the door opening, attaching them to one another so that their largest lateral dimensions are in abutting relationship, thereby creating a door header assembly and then attaching the door header assembly to each of the lateral aspects of the door opening. Front and rear entry-way door openings are typically 32 inches or 36 inches in width. The rough framing for the door opening, consisting of the wall studs and cripple studs, typically extends four inches on each lateral side of the door opening, thereby adding a total of eight inches to the total door frame width. Thus, a 36 inch door opening has rough framing which extends 44 inches in width, while a 32 inch door opening has rough framing which extends 40 inches in width. The door opening is known in the art as the door frame. Once the framed wall having the door frame therein is in place, a wall surface is typically applied over the wall. Typical wall surfaces are drywall sheets made of compressed plaster or concrete having paper or paperboard planar front and back surfaces. The drywall sheets, having a typical wall thickness of 1/2 inch, are applied to the framed wall and attached to the wall studs using nails or screws.
After the drywall is secured to the wall, a door mounted on hinges in a door jamb may be mounted into the door frame and secured therein using nails or screws. Door trim pieces are then applied around the perimeter of the door frame to cover any opening between the door jamb and the door frame. The door trim is largely esthetic in nature and is non-structural, but typically covers up to 11/2 inches of the rough door frame around its perimeter. Thus, approximately 21/2 inches of door frame remain in which to secure a mounting bracket to retain a security device in a strong fixed position in the door frame studs.
Virtually anyone familiar with hinged doors understands that hinged doors open by pivoting on hinges through an arc typically from 0.degree., where 0.degree. represents the door in its closed position coplanar with the wall, to greater than 90.degree. to permit passage through the doorway.
Virtually all of the conventional barricade-type doorway security devices permit the door to open a small distance, for example less than 15.degree. relative to the wall, to permit visual identification of persons outside the doorway. Because many unauthorized intrusions occur because extraordinary forces are applied to the door, such as by kicking, prying, ramming, etc., any small opening in the door provides increased opportunity for the unwanted intruder to access the door hinges or break the door off of its hinges and obtain unauthorized entry.
It has been found desirable, therefore, to provide a doorway security barricade apparatus which removably attaches to the door frame and which includes a means to apply a positive pressure to the door and restricts movement of the door latch or deadbolt within the door jamb, prevents opening of the door, and restrains against extraordinary external forces applied against an exterior surface of the door.

Doorway security device and method of using same


The present invention provides for methods and compositions for lightweight composite antiballistic assemblies comprising interlocking ceramic plates or modules. The modules may be self-contained and include both ceramic and ductile elements. Alternatively, interlocking ceramic plates may be arrayed over a ductile backing layer of metal or antiballistic fiber or polymer. The ceramic elements may be enhanced with carbon nanotubes or other reinforcing nanomaterials. In one or more embodiments, the strike-face, or front-facing surface, of this assembly may feature a non-planar design to assist in defeating incoming projectiles.

1. Field of the Invention
The field of art disclosed herein pertains to armor materials, and more particularly for composite ceramic materials for ballistic protection.
2. Description of the Related Art
Military standard body armor plates are presently based on technologies that are many decades old. For example, monolithic boron carbide (B4C) or Silicon Carbide (SiC) plates over an Aramid backing layer are frequently used. Aramid is a type of polymer and includes the generic family of Kevlar and Nomex. Military standard ESAPI (Enhanced Small Arms Protective Insert) plates are relatively primitive, based on technologies that are many decades old. For example, monolithic boron carbide (B4C) or Silicon Carbide (SiC) plates over an Aramid backing layer are frequently used. Aramid is a type of polymer and includes the generic family of Kevlar and Nomex.

Modular ceramic composite antiballistic armor


A diversity switch combiner for use in systems for receiving wideband signals is arranged to split the received signal into separate channels each carrying a respective frequency band. Respective switch means are provided for each channel in order to switch the input of each channel between different antennas. A switch control determines the switch setting in accordance with the result of a comparison operation, preferably performed during a guard period, in which the signal qualities for different settings are compared.

1. Field of the Invention
This invention relates to antenna diversity receivers, particularly those suitable for use for wideband radio reception and more particularly for multi-carrier systems.
2. Description of the Prior Art
Antenna diversity receivers use multiple antennas to overcome signal quality degradation caused by multipath fading. If the antennas are arranged such that their outputs fade independently, then the signals from the antennas can be combined to produce a signal with higher quality since it is unlikely that both antennas (branches) will simultaneously be in a deep fade. This allows the receiver to be used in areas with lower signal strengths or to provide higher signal quality and reliability within the normal system coverage area.
A common form of diversity combiner is a switch combiner, in which only one complete receiver is needed. The receiver is switched between the antennas and makes a judgment as to which antenna provides the strongest signal. Numerous schemes for doing this exist, but it is believed that none of them address suitable strategies for wideband channels. In all cases, switch combining performs less well than selection combining, in which two receivers are available so that the performance of both antennas can be simultaneously monitored, but a switch is used to select the signal from only one of them at a time. Maximal ratio combining (MRC) involves using, simultaneously, a plurality of receivers each operating on a signal from a respective antenna, and using signal processing to combine the outputs of the receivers. This gives better performance than either switch combining or selection combining, but is somewhat more expensive.
In a wideband fading channel, the bandwidth of the transmitted signal is wider than the coherence bandwidth of the channel (see S. R. Saunders, "Antennas and Propagation for Wireless Communication Systems", John Wiley & Sons, ISBN 0471986097, July 1999, for precise definitions). This implies that different parts of the received signal bandwidth will be faded to different extents, so the choice of the best antenna is not clear. A switch combiner could make a decision based on the total power available over the whole signal bandwidth, by performing a vector sum of the respective channel outputs of the receiver filter. However this yields only minor diversity gain when the delay spread is large, i.e. when there are significant delayed versions of the signal arriving at the receiver due to multipath echoes The results when selection combining is used instead of switch combining are not significantly better.
Choosing a single antenna, based on whichever criteria, and using this for the reception of the whole ISDB-T bandwidth can lead to significant degradation in performance. Mostly, this will be due to the fact that somewhere within the signal bandwidth there will be a deep null, so although at some carriers within the bandwidth there may be excellent diversity gain, there is none achieved at other carriers, with the resultant diversity gain essentially an average across the bandwidth.
Given that delay spread has been shown to produce this significant performance degradation, it would be attractive to have a combining technique which avoids this problem, but without the expense of MRC systems, and preferably using only one receiver.
Accordingly, it would be desirable to provide a switch diversity combiner which preserves the low cost of having a single receiver, but has improved performance in high delay-spread environments than available from any conventional single receiver combiner.


An adjustable load-bearing apparatus capable of being operatively disposed on the end of an elongate structural member having a substantially fixed length so as to produce a structural member having an adjustable length. The apparatus includes a saddle for receiving a load-carrying beam, at least two adjustment screw members fixedly attached to the saddle, and respective nuts which bear on a bearing surface of a cross-bar disposed on a bearing plate. A guide sleeve depending from the saddle and slidable longitudinally along a portion of the elonate structural member provides moment coupling between the saddle and the elongate structural member, without subjecting the adjusting screws or nuts to bending moments.

Adjustable support posts or columns are well known in the art. Typically, conventional support columns, such as lifting jacks for lifting and supporting of various structures employ a single, threaded support rod disposed in a main column. Many of these assemblies comprise a main column composed of two or more telescoping elements which can be extended and locked at predetermined intervals, such that the column can be adjusted to a length which is slightly shorter than that which is actually required. The threaded support rod, which may either engage an internal screw in the main column or an adjusting nut which bears on the top of the column, is then extended as required to support and/or raise the structure in question.
In many situations, the main column will be extended and locked into a position, and thereafter will not be further adjusted. The adjusting screw therefore constitutes the primary height adjusting means, while the main column remains locked at one length. Typically, however, adjustable columns are made as an integrated unit. Thus one is forced to purchase a large (and in some cases complex) adjustable column, even if the adjustment capabilities of the main column are not to be used. This unnecessarily increases the cost incurred by the user in order to obtain an adjustable column.
Furthermore, because the main column typically includes substantially rigid telescoping elements, it is not possible to employ the column within a space which is shorter than the shortest length (or substantially longer than the maximum extended length) of the main column. This means that one is forced to first measure the height of the location in which the column is to be placed, obtain a column having an appropriate length, and then install the column. This is a time consuming and laborious process, and, because the column almost invariably has a greater range of adjustment than is actually required, unnecessarily expensive. Furthermore, it is necessary for suppliers to stock adjustable columns having various sizes and extension capabilities, which results in increased storage costs, which are invariably passed on to the user.
U.S. Pat. No. 3,027,140 discloses an adjustable element which is adapted to be quickly and removably fitted to a fixed length column. The disclosed adjustable element comprises an adjusting screw and nut, a bearing plate, and a base plate. The adjustable element is intended to be used in conjunction with a column or post which is obtained separately, and cut approximately to length, by the user, on site.
This overcomes many of the above-stated problems related to adjustable columns. However, in a case where the column is made of wood, a hole must be bored into the end of the post in order to receive the adjusting screw. This hole must be carefully aligned with the central axis of the post, and must be properly sized so that the screw can slide within the hole, while being substantially prevented from rotation due to off-centre loading. Thus satisfactory on-site fabrication of the adjustable column is dependent on the skill of the builder, and may require special tools, thereby adding to the cost of installation of the post.
When the column is made using a metal pipe, it is necessary to employ spacer elements between the adjusting screw and the interior of the pipe. These adjusting members are intended to substantially prevent rotation of the adjusting screw due to off-centre loading. However, the requirement for purchasing spacer elements increases the cost of the column, and places a restriction on the size of the pipes which can be satisfactorily used.


A vent accumulator for a hydraulic integrator of the type having at least three pistons arranged in end-to-end relationship within an elongated housing. Each piston is adapted to move under hydraulic pressure in a direction away from one longitudinal end of the housing towards the opposite longitudinal end. Each of the pistons, except for the last piston adjacent the opposite end of the housing, is provided with a piston rod operatively connected to the piston next adjacent towards one end of the housing. Each piston is defined as having a first side directed towards one end of the housing and a second side directed towards the opposite end of the housing. Each of the pistons, except for the last two pistons in line, is provided with means for receiving hydraulic fluid under pressure from a load cell on its first side and an air vent communicates on it second side. The next-to-last piston, adjacent the opposite end of the housing, has means for receiving hydraulic fluid under pressure on its firstside, with the other side of the next-to-last piston being mechanically connected to the last piston. The last piston exerts its pressure on a body of hydraulic fluid which is located on its second side, whereby the pressure on this body of fluid represents the total of the pressures exerted on the remaining pistons by the load cells which are connected thereto. An air vent communicates with the last piston on its first side. The improvement over the prior art is the vent accumulator which is formed by an elongated cylindrical hollow closed chamber and a conduit connecting each of the air vents of the hydraulic integrator to the vent accumulator.

1. Field of the Invention
The present invention relates to a vent accumulator and, more particularly, to one which is designed to provide an air reservoir for a hydraulic integrator.
2. Description of the Prior Art
There are a large number of mining operations which use large off-the-road vehicles to haul minerals or coal from the mine to a transportation point. A record of the tonage of material removed from the mine is kept by the operators of the mine, this tonage being obtained by weighing the vehicles when loaded and substracting the known empty weight of the vehicle therefrom. These vehicles are usually weighed upon transportable hydraulic scales which are either placed upon a level roadway or are placed within a shallow pit. In the operation of these scales, air is drawn in and expelled from a hydraulic integrator located within the scales. Dirt and other foreign matter are often drawn into the hydraulic integrator thereby fouling the operation thereof. Further, when the hydraulic scales are placed within a shallow pit, water is sometimes permitted to be drawn into the hydraulic integrator. If the temperature drops below freezing, the water which may be within the hydraulic integrator freezes and thereby renders the hydraulic scales inoperable.
In the past, numerous filtration devices have been used on the hydraulic integrator within the hydraulic scales. However, none of these prior art devices has been designed to provide a closed air reservoir system for a hydraulic integrator thereby preventing foreign matter from being drawn into the hydraulic integrator.

Vent accumulator for hydraulic integrator


An automatic transmission fluid exchanging device includes drain and supply tubes to conduct used transmission fluid from and unused transmission fluid to a vehicle transmission. The device further includes a supply pump in the supply tube to flow unused transmission fluid into the transmission. A pair of flow control valves are disposed in the respective drain and supply tubes to allow the operator to match the flow rates of fluid through the respective tubes.

1. Field of the Invention
The subject invention relates to vehicle maintenance and, more particularly, to an apparatus for withdrawing and replenishing transmission fluid in an automatic transmission.
2. Description of the Prior Art
Automatic transmissions require transmission fluid because such fluid is employed in part as a driving means within the transmission and is additionally employed to lubricate the internal components within such transmissions. Over time such fluid becomes less viscous and thus less efficient in lubricating such components. It is therefore desirable to periodically perform an exchange of fluid to maintain the viscosity of such fluid within the transmission and to maintain the cleanliness of the transmission and thereby increase the useful life of the transmission. A complete exchange of fluid is preferred so that the used fluid as well as undesirable foreign matter contained therein is completely removed and is replaced with new, more viscous fluid.
In the field of devices for flushing and filling fluids in an automobile engine or transmission, various different embodiments of such apparatus have been known for a number of years and, by way of example, forms of such embodiments can be found in U.S. Pat. Nos. 3,513,941, 3,867,999 4,095,673, 4,674,456, and 5,056,621.
The above mentioned prior art flushing and filling apparatus have some disadvantageous features associated with them. For example, flushing and filling automatic transmissions with fluid or oil according to many prior art methods is a relatively time-consuming, cumbersome and inefficient process. The conventional method is to replace the fluid housed in the pan of the transmission. The pan typically holds from 1 to 5 quarts of the total 7 to 15 quart capacity of the transmission. Thus emptying the pan and then adding that amount of new fluid only serves to dilute the used fluid with some 15-25% of new fluid. Hence this conventional service is inefficient since it only serves to mix new fluid with a large quantity of used fluid. Furthermore, this service requires the removal of the transmission fluid pan from the transmission for emptying of the fluid therefrom and replacement of the pan on the transmission housing. This is a messy and time consuming process. Furthermore, the pan is often not replaced squarely over the pan seal or, on occasion, will trap small foreign obstacles in the seal area resulting in leakage.
More recently, there have been efforts to change all the fluid in an automobile's transmission by disconnecting a fluid tube and draining the fluid into a waste oil dump while manually pouring new fluid into the transmission dipstick hole. This procedure has proven to be inefficient, inadequate and so time consuming that it has failed to gain broad popularity.
Another prior method involved disconnecting a transmission fluid cooler line and allowing one end of such cooler line carrying used fluid to drain freely, while the other end of the line was connected to a pressurized tank which injected unused fluid into the cooler line connected to the transmission. One major disadvantage associated with this method is that, in many instances, the rate at which fluid exits the transmission cannot be matched by the rate at which unused fluid is injected into the transmission because the transmission, due to internal resistances, cannot accept fluid at the same rate as the rate at which used fluid is flowed by the transmission pump into an unrestricted cooler line. As such, there is a risk that the fluid seals, rear bearings and other internal components of the transmission could suffer damage due to the progressively diminishing level of fluid in the transmission during such a process. This difficulty is compounded by the fact that the flow resistance varies with the different models of transmissions.
Other work in this field has led to the proposal of a transmission changer including air pressurized tanks for supply and extraction of transmission fluid via the transmission cooling lines. A device of this type is shown in U.S. Pat. No. 5,318,080 to Viken issued on an application filed Oct. 25, 1991, subsequent to the time I conceived my invention. I am unaware of any commercialization of this device.
As such, it may be appreciated that there continues to be a need for an automatic transmission fluid exchanging device which efficiently removes substantially all of the used fluid in an automatic transmission and simultaneously replaces the removed fluid with the same amount of unused transmission fluid, while at the same time posing minimum risk of damage to the transmission. The instant invention addresses such needs.

Automatic transmission fluid changer apparatus


A data communication system for use in downhole applications wherein electrical energy is supplied over a multiple-conductor power cable to an ESP motor assembly. A downhole unit is AC-coupled to the conductors of the power cable through the wye point of the ESP motor assembly. A surface unit is AC-coupled to the conductors of the power cable. Uplink communication of telemetry data occurs over an AC communication scheme supported by the downhole unit and the surface unit. Downlink communication of remote control command data occurs over a different AC communication scheme supported by the surface unit and the downhole unit. These AC communication schemes provide an independent supply of power to the downhole environment. All communication between the surface and downhole environment is accomplished through the power cable without the use of additional communication lines. Data communication is maintained in the event of a ground fault on the power cable.

1. Field of the Invention
This invention relates broadly to data communication systems for downhole devices. More particularly, this invention relates to data communication systems over a power cable to an electrical submersible pump (ESP).
2. Description of Related Art
Various communication systems for telemetry signals that represent physical parameters measured by sensors within a borehole have been proposed and/or utilized. Several such systems employ the three-phase power cable (which transmits power to the ESP) for transmission of such telemetry signals.
An example of such a system is shown in U.S. Pat. No. 5,515,038. In this system, direct current (DC) offsets to the alternating current (AC) power signal carried on the cable are used to carry the telemetry data.
Disadvantageously, such communication systems cannot tolerate a ground fault, for example, where one conductor of the power cable is shorted to ground. Moreover, such systems typically employ large isolation chokes on the surface and in the downhole environment, which limit the data transfer rates of the system, and also fail to operate in noisy environments.
In another system shown in U.S. Pat. No. 6,587,037, phase-to-phase signaling is used to carry the telemetry data over the conductors of the power cable. Disadvantageously, the communication requires access to all three conductors in the downhole environment, which is difficult and expensive to implement and maintain.
Thus, there is a need in the art to provide a communication system for downhole devices that is tolerant to ground faults and is also cost-effective. Moreover, the communication system should advantageously avoid the use of large isolation chokes, provide relatively high data transfer rates, provide two-way communication, and also operate efficiently in noisy environments.

Data communication and power supply system for downhole applications


A fiber optic cable and method of manufacturing the same having at least one optical fiber component, at least one strength member and at least one ultra-low shrinking filament. The at least one ultra-low shrinking filament having a shrinkage of about 0.2% or less when heated and held at about 85xc2x0 C. for about seven days. At least one strength member and at least one ultra-low shrinking filament being disposed generally between the at least one optical fiber component and a cable jacket. The jacket generally surrounding the at least one optical fiber component, the at least one strength member and the ultra-low shrinking filament. The cable can include an interfacial layer interposed between said at least one optical fiber component and the jacket. Additionally, the cable can be riser or plenum rated.

The present invention relates generally to fiber optic cables and, more particularly, to fiber optic cables having ultra-low shrinking filaments.
Fiber optic cables include optical fibers that are capable of transmitting voice, video, and data signals. Fiber optic cables have advantages over electrical voice, video and data signal carriers, for example, increased data capacity. As businesses and households demand increased data capacity, fiber optic cables can eventually displace electrical voice, video, and data signal carriers. This demand for fiber optic cables has led to shortages of fiber optic cable materials.
Aramid fibers are cable materials that can serve several functions, such as: providing tensile strength to the fiber optic cable; cushioning the optical fibers from compression and impact loads; covering the optical fibers during the extrusion of the outer jacket to prevent the optical fibers from sticking to the extruded outer jacket; and binding the optical fibers together to prevent relative movement. Aramid fibers can, however, be expensive.
In addition to being cost effective, cables should be simple to manufacture and have a relatively small diameter. An example of a reduced diameter indoor fiber optic cable is disclosed in U.S. Pat. No. 5,627,932, which is incorporated herein by reference. This fiber optic cable requires a tight buffered optical fiber or fibers disposed within a layer of loose aramid fibers, more specifically kevlar(copyright) aramid fibers, which are surrounded by an outer jacket. This cable can be made of flame retardant materials for riser or plenum applications; however, the cable has disadvantages. For example, the cable requires a significant quantity of aramid fibers, which are typically expensive, thereby increasing cable manufacturing costs.
Fiber optic cables should also have acceptable levels of attenuation. An example of a fiber optic cable designed to prevent attenuation as a result of the manufacturing process is disclosed in U.S. Pat. No. 5,822,485, which is incorporated herein by reference. This fiber optic cable or cable element requires a jacket surrounding an optical fiber and aramid fibers, such as kevlar(copyright), without an intended lay. The manufacturing process requires that the tension applied to the aramid fibers during manufacturing does not exceed the tension applied to the optical fiber during manufacturing. Although this fiber optic cable is designed to prevent attenuation induced during the manufacturing process, this design has several disadvantages. For example, the cable requires a significant quantity of aramid fibers, which are typically expensive, thereby increasing cable manufacturing costs.
FIG. 1 (prior art) is a cross-sectional view of a fiber optic premises cable 10. Cable 10 comprises four ends of aramid fibers 12, more particularly four 2450 denier kevlar(copyright) fibers, forming a layer 16 that can be layless or stranded around a single tight buffered optical fiber 14. Outer jacket 18 generally surrounds layer 16. The present inventor has discovered that cable 10 only requires two of the four aramid fibers 12 to provide the requisite tensile strength, the two additional aramid fibers 12 are required to provide coverage and padding for optical fiber 14.
An aspect of the present invention includes a fiber optic cable having at least one optical fiber component, at least one strength member and at least one ultra-low shrinking filament. The at least one ultra-low shrinking filament having a shrinkage of about 0.2% or less when heated and held at about 85xc2x0 C. for about seven days. The at least one strength member and at least one ultra-low shrinking filament being disposed generally between the at least one optical fiber component and a jacket. The jacket generally surrounds the at least one optical fiber component, the at least one strength member and the at least one ultra-low shrinking filament. The cable can include an interfacial layer interposed between the at least one optical fiber component and the jacket. Additionally, the cable can be riser or plenum rated.
Another aspect of the present invention includes a fiber optic cable having at least one optical fiber component generally stranded around a central member. A first layer including at least one strength member and at least one ultra-low shrinking filament. The first layer being disposed generally between the at least one optical fiber component and a jacket. The at least one ultra-low shrinking filament having a shrinkage of about 0.2% or less when heated and held at about 85xc2x0 C. for about seven days. The jacket generally surrounds the at least one optical fiber component, central member and the first layer. The cable can include an interfacial layer interposed between the at least one optical fiber component and the jacket. Additionally, the cable can be riser or plenum rated.
A further aspect of the present invention includes a fiber optic cable including a first group of tight-buffered optical fiber components being generally adjacent a central member. A first layer being disposed generally between the first group of tight-buffered optical fiber components and a second group of tight-buffered optical fiber components. A second layer being disposed generally between the second group of tight-buffered optical fiber components and a jacket. The jacket generally surrounds the central member, the first and second groups and the first and second layers. One of the layers includes at least one ultra-low shrinking filaments having a shrinkage of about 0.2% or less when heated and held at about 85xc2x0 C. for about seven days. The cable can include an interfacial layer interposed between the central member and the jacket. Additionally, the cable can be riser or plenum rated.
Yet another aspect of the present invention includes a method of manufacturing a fiber optic cable. The method includes paying off at least one optical fiber component, at least one strength member, and at least one ultra-low shrinking filament. The at least one ultra-low shrinking filament having a shrinkage of about 0.2% or less when heated and held at about 85xc2x0 C. for about seven days. Defining a cable core by placing said at least one strength member and at least one ultra-low shrinking filament adjacent to at least one optical fiber component. The method also includes extruding a jacket around said core.

Fiber optic cables having ultra-low shrinking filaments and methods of making the same