Detachable clamp with a leaf spring

The disengageable clamp of a cable car or chair lift has a control lever 17 carrying the movable jaw 14, articulated on the fixed jaw 13. At least one flexion leaf spring 23 is interposed between the clamp body 10 and the control lever 17 in order to force this lever into the clamp closure position. Two leaf springs can be disposed on each side of the clamp body 10.

The invention relates to a disengageable clamp for coupling a load to a
 track/traction cable for an overhead cable transportation installation,
 comprising a clamp body extending transversely on one side of the body, in
 a position coupled to the latter, and carrying an articulation of a
 suspension member supporting the load, a cable clamping vice, consisting
 of a fixed jaw carried by the clamp body and a movable jaw articulated on
 the fixed jaw, a control lever, which is integral with the movable jaw and
 extends the latter whilst lying and travelling in a plane perpendicular to
 the cable and containing the clamp body, in order to control the opening
 and closing of the vice, and at least one spring acting on the control
 lever in the closed position of the jaw.
 BACKGROUND OF THE INVENTION
 1. Discussion of Prior Art
 A known clamp of the type mentioned (EP-A-0 056 919) has coil springs
 interposed between the clamp body and the control lever. The coil springs
 require an axial guide rod and articulations in the spring anchoring
 areas. This arrangement is complicated and the springs have a large amount
 of travel and are therefore bulky.
 The aim of the present invention is to permit the production of a
 disengageable clamp with a simple and compact structure, insensitive to
 frost and ice, so as to be able to remain on line permanently.
 The clamp according to the invention is characterised in that the spring is
 a flexion leaf spring, which cooperates on the one hand with the control
 lever and on the other hand with the clamp body, the leaf spring extending
 substantially in the said plane or parallel to this plane and in the
 general direction of the clamp body, and supplying the force for coupling
 the clamp to the cable.
 A leaf spring can be housed in a restricted space and there is no risk of
 it being blocked by ice, the latter breaking under the least flexion of
 the spring. The absence of a guide rod also reduces the risk of blocking.
 The leaf of the spring can have, at rest, various shapes and, through a
 judicious choice of the anchoring points and/or of the configuration and
 structure of the leaf, it is easy to obtain a suitable curve for the
 variation in the clamp control force. The spring can be of a well known
 type with several leaves placed one on top of the other, with different
 characteristics.
 The document WO-A-87 01081 and the document DE-B-10 80 580 disclose clamps
 incorporating a leaf spring, but this spring does not supply the force for
 coupling to the cable, which is derived from the weight of the car.
 2. General Discussion of the Invention
 According to a development of the invention, two springs are disposed
 symmetrically on each side of the plane containing the clamp body and
 control lever, so as to ensure the security of coupling of the clamp to
 the cable in the event of breakage of one of the springs and so as to
 distribute the forces.
 According to one embodiment of the invention, the spring leaf, of elongate
 shape, is interposed between the clamp body and the control lever, one of
 the ends being, for example, anchored rigidly to the clamp body, on the
 same side as the vice, and the other end cooperating with a roller carried
 by the control lever, on the same side as the free end of the latter. The
 leaf thus extends almost parallel to the control lever and releases the
 space around the clamp body in the suspension member articulation area.
 According to a variant embodiment, the leaf spring is almost straight, in
 the position of clamping the clamp, and is fixed at both ends, so as to be
 subjected to a buckling force during the opening movement of the clamp.
 The opening control is exerted on the control lever, in the usual fashion,
 or preferably directly on the spring.
 According to another embodiment, the leaf spring has an appreciable
 curvature, for example in the form of a half loop or several loops in a
 drum shape, with a view to increasing the length of the leaf whilst
 limiting the bulk.
 The ends of the spring leaf can be anchored rigidly, for example by
 embedding, on the clamp body and/or on the control lever, or can have an
 articulation allowing a limited relative movement.
 According to another embodiment of the invention, the leaf spring is
 buttressed by its ends on the clamp body and its middle part cooperates
 with the control lever, a reverse arrangement being possible. One of the
 ends of the spring is, for example, embedded on the clamp body, whilst the
 opposite end is mounted for limited sliding by means of a rocker bar
 articulated on the clamp body. The two supports can consist of articulated
 rocker bars. The middle part of the spring is in abutment on a lug carried
 by the control lever in order to transmit the force of the spring to this
 lever. Two buttress springs with opposite curvatures can be associated by
 connecting their respective ends, the middle part of one of the springs
 cooperating with the control lever and that of the other spring with the
 clamp body. The ends of the springs are perfectly connected by
 articulations and, in this case, at least one of the middle parts is
 rigidly anchored to the clamp body and/or control lever.

DETAILED DESCRIPTION OF THE INVENTION
 In all the figures the same reference numbers are used to designate similar
 or identical parts. A disengageable clamp has an elongate body 10 which
 extends, in the position where the clamp is coupled to the cable,
 transversely to the cable. The body 10 carries an articulation 11 for a
 suspension member 12 and is extended by a pair of jaws 13, 14 forming a
 cable clamping vice. One 13 of the jaws is fixed and the other one 14,
 which is movable, is articulated on a shaft 15 carried by the body 10. In
 the position of clamping of the cable by the jaws 13, 14, the shaft 15
 extends parallel above the cable. The movable jaw 14 is formed at the end
 16 of a control lever 17, which extends and can travel, when pivoting on
 the shaft 15, in a plane perpendicular to the cable, which contains the
 clamp body 10 and which corresponds to the plane of FIG. 1. At the end 18,
 opposite the movable jaw 14, of the lever 17 there is fixed a rotation
 shaft 19 for a control wheel 20, able to cooperate with a control rail 28.
 The clamp body 10 carries bearing rollers 21 and a cross member 22 for
 driving by friction, in order to move the clamp, disengaged from the
 cable, in the stations on transfer rails. Such a clamp is well known and
 it is unnecessary to describe it in any further detail.
 Referring particularly to FIGS. 1, 2 and 9, it can be seen that the control
 lever 17 is acted on in the cable clamping position by a pair of leaf
 springs 23, 24 interposed between the control lever 17 and the clamp body
 10. The two springs 23, 24 are disposed symmetrically on each side of the
 plane defined by the control lever 17 and the clamp body 10 and extend
 parallel to this plane in the general direction of the control lever 17.
 One 25 of the ends of the springs 23, 24 is rigidly anchored by embedding
 in the clamp body 10 on the same side as the jaws 13, 14 whilst the
 opposite end 26 bears on a roller 27, mounted for rotation on the
 controller lever 17 on the same side as the control wheel 20. In the
 closed position of the clamp, depicted in FIG. 2, the leaf springs 23, 24
 are substantially straight, under pretension, and exert a force F on the
 control lever 17, tending to pivot the latter in the counter clockwise
 direction, for clamping the cable. When the control rail 28 moves the
 control wheel 20 downwards, the control lever 17 pivots in a clockwise
 direction towards the position, depicted in FIG. 1, of opening of the
 clamp, counter to the force F' exerted by the springs 23, 24, curved
 downwards. It should be noted that this arrangement of the springs 23, 24
 completely releases the space around the articulation 11 of the suspension
 member 12. The roller 27 can consist of a single stop or conversely have a
 guide runner for the end 26 of the spring. It is clear that the roller 27
 can be disposed on the clamp body 10, the spring 23, 24 then being
 embedded on the control lever 17, and that the clamp can have a single
 spring or conversely a larger number of springs.
 FIG. 3 illustrates a variant in which the springs 23, 24 are embedded on
 the side of the clamp body 10 opposite to the jaws 13, 14, while their
 free end 26 is in abutment on a roller 27 disposed on the middle part of
 the control lever 17. The functioning of the clamp is not changed, but it
 should be noted, that, in the arrangement of the springs 23, 24 according
 to FIGS. 1 and 2, the lever arm of the forces F and F' remains
 substantially constant, while in the arrangement according to FIG. 3 the
 lever arm varies appreciably.
 In the embodiment depicted in FIG. 4, the springs 23, 24 are bent in the
 form of a half-loop, one end of which 25 is embedded on the clamp body 10,
 on the side opposite the jaws 13, 14, and the other end 26 of which is
 embedded on the control lever 17 on the same side as the wheel 20. The
 great length and the bent shape of the spring leaf 23, 24 allow
 compensation for the relative movement of the anchoring points, and the
 leaf can be embedded at both ends, which simplifies the assembly.
 The embodiment illustrated by FIGS. 5 and 6 repeats the arrangement
 according to FIGS. 1 and 2, with the abutment of the spring 23, 24 on
 rollers 27 on the same side as the roller 20 of the control lever 17 and
 embedding on the clamp body 10 on the same side as the jaws 13, 14, but
 the embedding point is shifted upwards level with the cross member 22. In
 this case, the lever arm of the force F' of the open clamp is lower than
 that of the force F of the closed clamp and the control force for the
 clamp can thus be maintained substantially constant or even reduced as the
 clamp opens. It will be understood that a judicious choice of the
 characteristics of the springs 23, 24 and of the anchoring points makes it
 possible to obtain the required curve for the variation in clamp control
 force.
 Referring to FIGS. 7 and 8, it can be seen that the springs 23, 24 are
 coiled in a drum shape, in the form of a clothes peg spring, one 25 of the
 ends of the springs 23, 24 being articulated on the clamp body 10, whilst
 the opposite end 26 is articulated on the control lever 17 on the same
 side as the control wheel 20. In the closed position of the clamp,
 depicted in FIG. 8, the springs 23, 24 are under pre-tension and exert a
 force on the control lever 17, tending to pivot the latter in the counter
 clockwise direction, for clamping of the cable. It should be noted that
 one or both ends 25, 26 can be embedded. With each spring 23, 24 there can
 be associated a conjugate spring 23', depicted in broken lines in FIGS. 7
 and 8. The conjugate spring 23' has the same shape and is articulated at
 the same points as the associated spring, but is arranged opposite and its
 direction of coiling is the contrary. In this way the restoring force and
 the security of the clamp are increased.
 In FIGS. 10 and 11, the springs 23, 24, of elongate shape, are
 substantially straight, under pre-tension and slightly precurved, in the
 position of closure of the clamp, depicted in FIG. 11. They exert a force
 F on the control lever 17, tending to pivot the latter in the counter
 clockwise direction, for clamping the cable. When the control rail 28
 moves the control wheel 20 downwards, the control lever 7 pivots in the
 clockwise direction towards the position, depicted in FIG. 10, of opening
 of the clamp, causing the springs 23, 24 to flex by buckling. The force
 opposed by the springs 23, 24 remains substantially constant from the very
 start of the buckling, which makes it possible to limit the control
 energy. The articulation of the ends 25, 26 of the springs 23, 24 consist,
 for example, of a simple bending of these ends in a loop around a pivot
 carried by the control lever 17 or clamp body 10. One or both ends 25, 26
 of the springs 23, 24 can be embedded. The springs 23, 24 can be precurved
 on one side or the other, and it is advantageous to associate, with each
 spring 23, 24, a conjugate spring 23', of opposite curvature, and
 articulated at the same points, in order to constitute pairs of springs,
 23, 23' in the form of an ellipse, as depicted in FIG. 12, in order to
 double the force and increase security.
 According to the variant illustrated by FIG. 13, the springs 23, 24 are
 articulated in the vicinity of the ends of the lever 17 and clamp body 10,
 the point of fixing to the clamp body 10 advantageously being shifted
 downwards by means of an appendage 31, so as to elongate the springs 23,
 24 and to adapt their characteristics.
 FIGS. 14 and 15 illustrate another method of controlling the clamp. The
 movable jaw 14 of the clamp is carried by a shortened lever 29, on which
 one 25 of the ends of the spring 23, 24 is articulated, the other end 26
 is articulated on the shortened lever 29 on the opposite side to the jaws
 13, 14. In its middle part the spring 23, 24 carries a loose wheel 30,
 able to cooperate with the control rail 28, extending along the path of
 movement of the clamp, in order to cause the spring 23, 24 to buckle and
 the jaws 13, 14 to open. The buckling force on the spring 23, 24 can
 obviously be applied to the spring 23, 24 in any other operative manner,
 notably by means of shoes. Such a clamp is particularly simple and it is
 clear that the spring 23, 24 can be disposed differently, notably
 according to one of the variants described above.
 The method by which the flexion leaf springs 23, 24 work is different in
 the embodiments depicted in FIGS. 16 to 19. In the clamp according to
 FIGS. 18, 19, one 25 of the ends of the springs 23, 24 is anchored rigidly
 by embedding in the clamp body 10 on the same side as the jaws 13 and 14,
 whilst the opposite end 26 is articulated on a rocker bar 34, the opposite
 end of which is articulated on the clamp body 10. The middle part of the
 springs 23, 24 is loaded by a roller 27 carried by the control lever 17.
 In the closed position of the clamp, depicted in FIG. 19, the leaf springs
 23, 24 are curved under pre-tension and exert a force on the control lever
 17, tending to pivot the latter in the counter clockwise direction, for
 clamping the cable. When the control rail 28 moves the control wheel 20
 downwards, the control lever 17 pivots in a clockwise direction towards
 the position, depicted in FIG. 18, of opening of the clamp, counter to the
 force F exerted by the springs 23, 24. It is clear that the roller 27 can
 be disposed on the clamp body 10, the springs 23, 24 then being fixed, in
 abutment through their two ends, to the control lever 17 with an opposite
 curvature.
 FIGS. 16 and 17 illustrate a variant, in which each spring 23, 24 is
 associated with a conjugate spring 23' with an opposite curvature, each
 end 25, 26 and the spring 23, 24 being connected by an articulation 32, 33
 to a conjugate end 25', 26' of the associated spring 23', in order to
 constitute a pair of springs of elliptical shape. The middle part of the
 spring 23, 24 cooperates with the control lever 17, while the middle part
 of the conjugate spring 23' cooperates with the clamp body 10. These
 middle parts can be fixed rigidly, for example by embedding, or be
 articulated on the clamp body 10 and/or control unit 17. They can also be
 in abutment on a roller carried by the control lever 17 and/or clamp body
 10, in a manner similar to that described above, the positioning of the
 conjugate springs 23, 23' being in this case provided by any effective
 means, for example by mounting the articulation 32 for rotation on a shaft
 carried by the clamp body 10, as depicted in FIGS. 16 and 17.
 Arrangements, notably for fixing the springs, described in detail in one of
 the above examples are of course applicable to the other examples.