Terminal clamp for a battery terminal post

A terminal clamp for a battery terminal post including first and second relatively movable jaws defining between them a passage for receiving a battery terminal post, and a screw-operated clamping arrangement for closing the first and second jaws about the terminal post, in use, to grip the post against the action of a resilient restoring force urging the jaws apart, the screw-operated clamping arrangement including first and second components in screw-threaded arrangement with one another, the first component being held against rotation relative to the jaws, the second component having a frusto-conical cam surface cooperable with corresponding part frusto-conical cam surfaces of the jaws, whereby rotation of the second component relative to the first component and the jaws causes rotational and axial movement of the frusto-conical cam surface of the second component relative to the part frusto-conical surfaces of the jaws either to close the jaws or to release the jaws.

BACKGROUND OF THE INVENTION
 The present invention relates to a terminal clamp for connecting an
 electrical cable to a terminal post of a vehicle battery.
 U.S. Pat. No. 5,088,941, German Patent No. 3811629 and UK Patent
 Application No. 2287587 each disclose a screw-operated battery terminal
 clamp comprising a pair of jaws defining between them a passage for
 receiving a battery terminal post, and screw-operated clamping means for
 closing the jaws against a resilient restoring force, in use, to grip the
 post. In each case, the clamping means includes an inclined generally
 rectilinear cam surface on each jaw and cooperating inclined rectilinear
 cam surfaces on a component movable relative to the jaws by the screw
 action, either in a direction to cause the cam surfaces to coact to close
 the jaws about the terminal post in use, or to release the jaws to open
 under said resilient restoring force.
 A problem encountered with such arrangements is that after being operated
 to hold the jaws closed, the cam surfaces may bind together so that
 release of the screw action is ineffective to release the jaws. It is an
 object of the present invention to provide a terminal post clamp wherein
 this problem is obviated.
 SUMMARY OF THE INVENTION
 According to the present invention, there is provided a terminal clamp for
 a battery terminal post comprising first and second relatively movable
 jaws defining between them a passage for receiving a battery terminal
 post, and a screw-operated clamping arrangement for closing said first and
 second jaws about the terminal post, in use, to grip the post against the
 action of a resilient restoring force urging the jaws apart, said
 screw-operated clamping arrangement including first and second components
 in screw-threaded arrangement with one another, said first component being
 held against rotation relative to said jaws, said second component having
 a cam surface cooperable with corresponding cam surfaces of said jaws,
 said cam surfaces being surfaces of revolution, or parts thereof, centred
 on the axis of said screw-threaded arrangement whereby rotation of said
 second component relative to said first component and said jaws causes
 rotational and axial movement of said cam surface of the second component
 relative to said cam surfaces of said jaws either to close the jaws or to
 release the jaws.
 It will be recognised that as the cam surfaces are forced to rotate
 relative to one another while moving axially to effect clamping or
 release, then the cam surfaces cannot bind together to frustrate release
 of the jaws in response to a corresponding rotation of said second
 component.
 Preferably said cam surfaces are frusto-conical.
 Desirably said first component comprises a captive bolt.
 Desirably said second component comprises a nut in threaded engagement with
 the shank of said bolt.
 Preferably said jaws are united at one end and carry said cam surfaces
 adjacent their opposite ends, said post receiving recess being defined
 intermediate said cam surfaces and said one end.
 Preferably a conductive lead is electrically connected to said jaws
 adjacent their united end.

DETAILED DESCRIPTON OF THE PREFERRED EMBODIMENT
 Referring now to FIGS. 1 and 2, the terminal clamp 10 comprises a first
 hollow cylindrical end region 12 open at its free end 12a. Integrally
 connected to said cylindrical end region 12, remote from the end 12a, are
 first and second clamping jaws 14 united with the region 12 by an end
 region 16. The jaws 14 are mirror images and are spaced apart by a gap 20
 which extends continuously from the common first end region 16 to a free
 second end region 22 of each jaw 14. The clamp has a first face 24,
 uppermost in use, and an opposite second face 26. A terminal post (not
 shown) which the terminal clamp 10 is to engage is frusto-conical having a
 small taper angle. Adjacent the end region 16 of the clamp 10, the jaws 14
 define between them a correspondingly frusto-conical passage 27 extending
 through the clamp 10 with the larger diameter end of the passage 27 at the
 face 26 of the clamp 10. Adjacent the end regions 22 of the jaws 14, the
 jaws define between them a cylindrical passage 29 having its axis parallel
 to that of the passage 27 and opening at the faces 24 and 26 respectively.
 Intermediate the free ends of the jaws and the passage 27 the upper
 surface 24 is cut away or otherwise shaped to define an upwardly extending
 frustum of a cone coaxial with the passage 29 and divided by the gap 20.
 The frustum has a cone angle of around 60.degree. and it can be seen that
 each jaw thus carries a respective upstanding part frusto-conical surface
 28. A locating recess 32 is formed in the face 26 of each of said jaws 14,
 opposite said frustum.
 Referring now to FIGS. 3a and 3b, bolt 40 comprises a cylindrical shank 42,
 one end of which is integrally formed with a head in the form of a cross
 piece 44. Said cross piece 44 has a substantially rectangular cross
 section as viewed in FIG. 3a, and a trapezoidal cross-section as viewed in
 FIG. 3b. The cylindrical shank 42 has a diameter less than that of passage
 29 (FIG. 1) to permit the jaws to close without restriction. The width of
 cross piece 44 is slightly less than that of the locating recess 32 (FIG.
 2). The cylindrical shank 42 has a screw-threaded region 46 extending from
 a free second end 48 of shank 42 towards said cross piece 44.
 Referring now to FIGS. 4 and 5, nut 50 comprises a hexagonal nut 52 having
 a screw-threaded bore 53 designed to mate with the screw-threaded region
 46 of bolt 40 (FIGS. 3a and 3b) and an integrally formed skirt 54. Said
 skirt has a cylindrical outer surface 56, an inner surface 58 which
 defines a frusto-conical recess 60 the cone angle of which corresponds
 with that of the frustum defining the surfaces 28 and which flares
 outwardly from the screw-threaded bore 53, and an annular end portion 62.
 Referring now to FIG. 6, in use, an electric cable 70 (shown in part) is
 inserted into the recess in the end region 12 which is then crimped,
 soldered, welded or otherwise arranged to hold the cable in place and to
 make electrical contact thereto. The shank 42 of the bolt 40 is inserted
 through the passage 29 from face 26 of the clamp 10, such that a portion
 of the screw threaded region 46 of the shank 42 extends beyond face 24 and
 the cross piece 44 is seated in the locating recess 32. The assembly is
 then placed on the terminal post 72 of a vehicle battery 74 (shown in
 part) such that the post 72 is located in passage 27 and the cross piece
 44 of the bolt 40 is held in its locating recess 32 by an upper surface
 74a of the battery 74. The nut 50 is then screwed onto the bolt 40 which
 is held in its locating recess 32 against counter-rotation. As the nut 50
 is tightened, the jaws 14 are drawn closer together, causing the terminal
 post to be gripped progressively more tightly therebetween.
 If removal of the clamping element 10 is required, for example for
 maintenance or replacement of the battery 74, the above process is
 reversed. This is a simple procedure even if there is corrosion between
 surfaces 58 of the nut 50 and 28 of the clamping component 10, since
 loosening of the nut 50, which is facilitated by the bolt 40 being held in
 its locating recess 32 against counter-rotation, inevitably results in
 both axial and rotational movement of the surface 58 relative to the
 surface 28, thus breaking any binding of the two surfaces and freeing the
 jaws 14 to spring apart, releasing their grip on the terminal post 72.
 It will be understood that while the provision of a cross-piece 44 and
 corresponding recesses 32 in the jaws is a convenient arrangement to
 inhibit rotation of the bolt 40, other arrangements for locking a bolt
 against rotation relative to the jaws are possible, for example the bolt
 could have a hexagonal head received in corresponding recesses in the
 jaws. Moreover alternative forms of nut 50 can be used, for example wing
 nuts or socket headed nuts provided with an appropriate recess 60 could be
 utilised.
 As will be apparent the cam surfaces 28, 58 could be other tapering
 surfaces of revolution centred on the axis of the bolt shank 42, for
 example part spherical.