Abstract: The invention relates to a surgical appliance for forming an opening through the skin of a patient and for distending the opening so formed. The appliance takes the form of a trocar which may comprise two separate components or two component portions formed by openings in a tube extending partially along the tube from the distal end. In either case, the components or component portions are preloaded towards a closed condition, but can be expanded into an open condition, for example by forcing a tubular expander into the trocar from the proximal end. The preloading of the trocar may be by a resilient sleeve surrounding the components or by a "set" introduced into the material forming the components. A cutting edge may be formed across substantially the full width of the distal end of the trocar and it is preferred that in the open condition, there is a no significant increase in the cross-section of the trocar towards the distal end.

Abstract: A fluid-operated ram, for example comprising a cylinder 10 and piston 12, is provided for actuating a device such as a chuck having jaws 15. When the jaws are moved by the ram to grip a workpiece this constitutes a limiting position which impedes the flow of fluid thus causing a build-up of fluid pressure within the ram. This build-up can be detected to give an indication as to when a workpiece has been securely and safely gripped. To ensure that a false indication is not given if the ram reaches an end of its working stroke before the workpiece is securely gripped, means (22) are provided to relieve pressure within the ram when the ram reaches an end of its working stroke.

Abstract: An apparatus is provided which enables the jaws of a chuck 10 to be removed from and inserted into jaw-ways 12, 13, 14 using a conventional workpiece handler, rather than a sophisticated and highly accurate dedicated jaw handling mechanism. A conventional workpiece handler cannot position a jaw to close tolerances but this problem is overcome by using a guide shoe 17 which can receive a jaw from the workpiece handler in any one of a range of positions and then accurately guide the jaw into one of the jaw-ways 12, 13, or 14.A mechanism 16 is provided for releasing the jaws from the jaw-ways, and for re-locking the jaws in position.

Abstract: A work holding device comprises an annular cylinder 14, an annular piston 15 movable with respect to the cylinder within the cylinder in an axial direction by application of fluid pressure, and a jaw drive device 28, 29, 30, 31 projecting from the cylinder 14 for applying radial movement to a work holding jaw 12, 13. The piston and/or the cylinder co-operates with the jaw drive device within the cylinder such that axial movement of the piston with respect to the cylinder causes radial movement of the jaw drive device. Since the translation of axial to radial movement takes place effectively within the cylinder, it is possible to reduce the axial length of the work holding device as compared to known work holding devices in which translational movement occurs outside the cylinder.

Abstract: A chuck comprises a body (10) rotatable about an axis (11) and at least one jaw (12) movable in a radial direction to clamp a workpiece in the chuck. At least one operating lever (14) is mounted on the body (10) and the, or each, lever is operable to move a jaw (12) radially. The, or each, lever is also movable axially with respect to the chuck body (10), to disengage from the associated jaw (12), enabling the associated jaw (12) to be removed simply and quickly from the chuck body (10) by movement in the radial direction.

Abstract: A workholding device comprises a body 10, a plurality of relatively movable base jaws 12, each base jaw 12 carrying one of a plurality of top jaws 13, such that when the base jaws 12 are moved relative to one another, a workpiece 15 can be gripped by the top jaws 13, and a sensing device 14 positioned to sense force transmitted from a top jaw 13 to a base jaw 12. Preferably a second sensing device 16 is provided to sense centrifugal force to permit compensation for its effect on the top jaws, so that a signal can be obtained which is an accurate measure of the force prevailing between the top jaws 13 and the workpiece 15.

Abstract: The invention relates to work holding and is concerned with the provision of a work holding device which is more efficient than known devices. According to the invention a work holding device comprises a device for gripping a workpiece, the device being provided with internal detection means for determining the value of a force between the device and the workpiece. The value of the force can be displayed for the benefit of a user of the device. It can also be used for control purposes.

Abstract: A fluid pressure operated chuck is provided with a stationary slip ring mounted on an axially rotatable chuck body, and a resilient sealing ring is located in substantially opposed grooves in the slip ring and mounted therein by temporary deformation of the resilient sealing ring during fitting, in the absence of fluid pressure. The sealing ring may be of a squat "T" section with the flanges at the head of the T providing marginal edge parts for location in the opposed grooves and the broad base face of the stem of the T forming a sealing contact face. Valve means are also provided in the chuck body to control the fluid pressure which latter acts on an axially displaceable piston to operate the jaws of the chuck.