Transmission of an electrical current via a sliding contact

Abstract

A device (100) for transmitting an electrical current between two elements that are movable relative to each other, by a strip (30) containing carbon, which extends in a longitudinal direction and is designed to rub against one of the elements so as to transmit an electrical current, the transmission device including: a strip holder (6), and bearing structure (10) designed to exert force on the strip (30), which urges same against the holder (6), the force being transverse relative to the longitudinal direction, wherein the bearing structure (10) and/or the holder (6) are shaped so as to occupy only a portion of the length of the strip (30) in the longitudinal direction.

Claims

1. A device for transmission of electrical current between a mobile element and a stationary element mobile relative to each other, by means of a strip containing carbon, extending in a longitudinal direction and designed such that one of its faces rubs against one of the mobile element and the stationary element so as to transmit the electrical current, said transmission device including: a strip support arranged for fixing the device to the other one of the mobile element and the stationary element and for transmitting the electric current to/from said other element, and bearing means, each bearing means being adapted to exert on the strip a force pressing it against the support, said force being transverse relative to the longitudinal direction, wherein the bearing means includes at least two bearing means spaced apart from each other and/or the strip support includes at least two supports spaced apart from each other, the at least two bearing means all together and/or the at least two supports all together are conformed to occupy 50% or less of the length of the strip, the bearing means includes an element with an inclined surface and spring means that cooperates with said element with the inclined surface, the spring means are located on a side of the strip that is opposite to the side of the face that rubs against one of the mobile element and the stationary element, and the bearing means are able to change from a closed state in which the bearing means press the strip against the support and the spring means exerts compression forces against the element with the inclined surface, to an open state for removing or installing the strip from/in the current transmission device, by compressing the spring means.

2. The electrical current transmission device as claimed in claim 1, further including the strip and wherein the strip includes means for mechanical reinforcement of the strip.

3. The device as claimed in claim 2, wherein the means for mechanical reinforcement of the strip include at least one portion produced in at least one composite material.

4. The device as claimed in claim 3, wherein the composite material includes carbon fibers and/or glass fibers.

5. The device as claimed in claim 2, wherein at least some of the mechanical reinforcement means are disposed on the back of the strip and on two lateral sides of the strip.

6. The device as claimed in claim 1, wherein two bearing means taken from said at least two bearing means and/or two supports taken from said at least two supports are provided at two respective neighborhoods of the ends of the strip.

7. The device as claimed in claim 1, wherein the bearing means include or are conformed to cooperate with a tool including an eccentric.

8. The device as claimed in claim 1, wherein the bearing means include or are conformed to cooperate with a tool including a toggle clamp.

9. The device as claimed in claim 1, wherein the bearing means include two jaws adapted to be disposed on either side of the strip and conformed to press the strip against the support.

10. The device as claimed in claim 1, wherein the bearing means include elastic means for exerting the force pressing against the support.

11. A tool in combination with the electrical current transmission device as claimed in claim 1, wherein the tool is adapted to cooperate with the electrical transmission device.

12. A pantograph or shoe system including a transmission device as claimed in claim 1.

13. The device as claimed in claim 1, wherein the strip has a length of 200 millimeters or more.

14. A method for installing/uninstalling a carbon-containing strip for a device for transmission of electrical current between a mobile element and a stationary element mobile relative to each other, said strip extending in a longitudinal direction and being designed such that one of its faces rubs against one of the mobile element and the stationary element so as to transmit the electrical current, the method including a step of withdrawing/positioning bearing means adapted to exert on the strip a force pressing it against a support, said force being transverse relative to the longitudinal direction, wherein the bearing means includes at least two bearing means spaced apart from each other and/or the support includes at least two supports spaced apart from each other, the support is arranged for fixing the device to the other one of the mobile element and the stationary element and for transmitting the electric current to/from said other element, the at least two bearing means all together and/or the at least two supports all together are conformed to occupy 50% or less of the length of the strip, the bearing means includes an element with an inclined surface and spring means that cooperates with said element with the inclined surface, the spring means are located on a side of the strip that is opposite to the side of the face that rubs against one of the mobile element and the stationary element, and the bearing means are able to change from a closed state in which the bearing means press the strip against the support and the spring means exerts compression forces against the element with the inclined surface, to an open state for removing or installing the strip from/in the current transmission device, by compressing the spring means.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be better understood in relation to the following figures, in which:

(2) FIG. 1 shows one example of a portion of a pantograph system in accordance with one embodiment of the invention,

(3) FIG. 2A is a perspective view of bearing means and a strip portion in one embodiment,

(4) FIG. 2B is a sectional view of bearing means and a strip portion in one embodiment,

(5) FIG. 2C is a perspective view of bearing means and a strip portion in one embodiment,

(6) FIG. 2D is a perspective view to show the change to an open state of bearing means in accordance with one embodiment of the invention,

(7) FIG. 3A is a perspective view to show the change to an open state of bearing means in accordance with one embodiment of the invention,

(8) FIG. 3B is a perspective view of the tool from FIG. 3A,

(9) FIGS. 4A and 4B are sectional views in a section plane of the strip showing very diagrammatically an example of localized bearing engagement in accordance with another embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

(10) FIG. 1 shows a device 100 for transmission of current via a sliding contact, here between a moving element and a catenary wire.

(11) This device 100 includes two strips 30 that rub on the catenary wire. These strips 30 include a carbon-based portion for picking up current, for example a strip 31 of graphite, and a portion 7 for mechanical reinforcement of the strip 30.

(12) This mechanical reinforcement portion 7 is produced in a composite material. This reinforcement portion 7 may for example include carbon fibers braided and then densified with carbon as described in the application FR2807365 and then impregnated with phenolic resin.

(13) The strips 30 are manufactured by molding the composite onto three sides of the carbon portion 31. The strip 30 is produced by steps of polymerization, machining the molded-on strip and sand-blasting/copper-plating the ends of the strip (this enabling improved electrical contact).

(14) The reinforcement portion 7 of the strip surrounds the strip 31 on three of its sides, namely the lateral sides and the back of the strip 31. This reinforcement portion 7 provides the mechanical strength of the strip 30, notably resistance to impact or deformation.

(15) The current transmission device 100 further includes two bearing means 10 for each of the strips 30. These bearing means 10 include two jaws 1, 3 adapted to press against the strip 30. The strip 30 has a section with oblique sides and the jaws 30 have a bearing surface matching these oblique sides so that when the jaws 1, 3 are clamped against the strip 30 a component of the bearing forces linked to the clamping action presses the strip 30 against the support. These bearing means will be better understood in relation to FIGS. 2A, 2B, 2C and 2D.

(16) In the embodiments of FIGS. 2A, 2B, 2C the strip 30 includes in addition to a current pick-up portion 31:

(17) a composite material portion 7 for mechanical reinforcement of the strip, and

(18) a reinforcement element 17 including a metal rod disposed inside the strip 30, here in a recess in the carbon-containing portion 31 on the face opposite the contact face 33 intended to rub against the catenary wire. The central reinforcement element may in particular be stuck to the carbon portion 31. This reinforcement element 17 can enable further reinforcement of the strip 30.

(19) It may be noted that the strips represented in FIGS. 2A and 2B correspond to an embodiment in which the composite portion 7 is disposed on only the lateral sides of the strip 30.

(20) On the other hand, in the FIG. 2C embodiment, the composite material portion 7 is disposed on the lateral sides and on the back of the carbon-containing portion 31.

(21) Referring to these FIGS. 2A to 2D, the bearing means include a fixed jaw 1 and a mobile jaw 3. The mobile jaw is adapted to slide in a transverse direction perpendicular to the longitudinal direction of the strip 30.

(22) The mobile jaw 3 can be pressed against the strip 30 so that the jaws 1, 3 press the strip 30 against a support, for example a connecting or contact portion 6.

(23) This connecting or contact portion 6 extends over a portion of the strip 30 held pressed into the fixing means. This portion 6 is made of a conductive metal, preferably copper, in order to provide a good electrical connection.

(24) The ends of this connecting portion 6 are conformed to fasten the horns 20 (FIG. 1). The horns 20 make it possible to prevent the pantograph snagging the catenary wire and enable the contact wire to be moved onto the wear strips. The horns 20 may be made from a lightweight and corrosion-resistant material such as aluminum.

(25) The bearing means 10 include elastic means, here a coil spring 8. This spring 8 enables loading of a back portion 5 of the mobile jaw, this mobile jaw back portion 5 being fastened to, and possibly in one piece with, the mobile jaw 3. The loading forces exerted by the coil spring 8 are therefore transferred to the mobile jaw 3.

(26) The coil spring 8 is retained in a housing 2 between the back portion 5 of the mobile jaw and a back portion 4 of the housing.

(27) The bearing means represented in FIGS. 2A to 2D are adapted to be able to adopt, in addition to the bearing position represented in FIGS. 2A, 2B, 2C, an open position allowing removal of the strip 30 and installation of a new strip.

(28) FIG. 2D shows an example of the change to this dissociated state.

(29) The dissociated state may be obtained by locking the back portion 5 of the mobile jaw in a position closer to the back portion 4 of the housing than that represented in FIG. 2B.

(30) This may be achieved by means of a tool 50 including a rod (not visible in FIG. 2D) adapted to interengage with this back portion 5 of the mobile jaw, a handle 52 for holding it in the hand and an eccentric 51 fastened to the handle and articulated to the rod.

(31) This rod may be inserted via the back portion 4 of the housing and therefore have a section with dimensions slightly smaller than those of the main orifice 40 (FIG. 2A) of this back portion 4 of the housing. The section of the rod may be circular, for example.

(32) The end of the rod is designed to interengage with the back portion 5 of the mobile jaw after rotation of the tool about the axis of the rod, for example through 90°, this axis being perpendicular to the longitudinal direction of the strip 30. The rod and the portion 5 are therefore conformed so as to be able to interengage with each other after a rotation of 90°. A person skilled in the art will know how to design a rod and an element with appropriate recesses and protuberances to enable this interengagement.

(33) This interengagement is effected when the eccentric 51 is oriented with its face 53 facing the back portion 4 of the housing, i.e. with the cylindrical portion 54 extending along the rotation axis of the handle 52 then substantially aligned with the axis A1 of the rod. The handle 52 is turned about the axis A1 of the rod, for example through 90°, and the end of the rod then comes to cooperate with the back portion 5 of the mobile jaw. The rod may interengage with the portion 5 from behind, i.e. so that interengagement takes place on the exterior side of the housing 2.

(34) Once the rod of the tool 50 is interengaged with the portion 5, it is then possible to pull on this portion 5 by means of the rod to open the clamp consisting of the jaws 1, 3.

(35) This may advantageously be effected by rotating the assembly comprising the handle 52 plus the eccentric 51 90° about an axis A2 parallel to the longitudinal direction of the strip. The eccentric 51 enables this rotation movement to be transformed into a movement in translation of the rod.

(36) The eccentric 51 may have a shape such that once the rotation has been effected the eccentric 51 comes to rest against the portion 4 over a portion 55 of the surface of the eccentric, thus locking the open position. It is then possible to remove the worn strip and to install a new strip.

(37) Such a tool 50 can therefore enable much quicker maintenance than in the prior art, in which the strip plus bracket assembly has to be unscrewed. As explained above, it in fact suffices to insert the rod of the tool 50 inside the coil spring, to unlock the stop notch of the fixing means, to execute a quarter-turn to interengage with the portion 5 and to lower the handle (or lever) of the tool to open the clamp. The worn strip can then be removed and a new strip installed, after checking that the bearing faces of this new strip are clean. The lever is then raised: the fixing means are closed and the spring acts on the mobile jaw, which compresses the strip. The tool may then be removed.

(38) Referring to the embodiment of FIGS. 3A and 3B, the tool 74 represented in FIG. 3B is adapted to cooperate with bearing means of the type represented in FIGS. 2A to 2D, advantageously with the same bearing means.

(39) The bearing means are intended to be received between a fixed back member 75, fixed to and possibly in one piece with a U-shaped portion 72, and a mobile back member 70.

(40) The fixed back member 75 includes an alignment stud 71 adapted to be received in the main orifice of the portion 5 (FIGS. 2A to 2D).

(41) The mobile back member includes two alignment pins, not represented, adapted to be inserted into orifices 76 in the back of the housing 4.

(42) The assembly comprising the stud plus the main orifice in the portion 5 therefore enables relatively coarse positioning of the bearing means and the assembly comprising the pins plus the orifices 76 enables relatively fine positioning.

(43) The mobile back member 70 is fastened to a handle 73 so that when this handle 73 is actuated in the upward direction the mobile back member is moved closer to the fixed back member 75. If the bearing means 10 are positioned in the tool 74, the mobile back member then comes into abutting engagement against the portion 4. This portion being fixed, the force exerted by the tool on the bearing means will move the portion 5 toward the portion 4, compressing the spring.

(44) The mobile jaw 3 being fastened to the portion 5, this mobile jaw is then moved toward the handle 73 and the strip can be removed and replaced with a new strip.

(45) The handle is then lowered. The mobile back member 70 is then moved back toward the handle and separates from the portion 4. Because of the compression forces exerted by the spring, the portion 5 resumes its initial position. The spring still being compressed, the forces exerted by the spring hold the jaws 1, 3 against the strip (not represented in FIG. 3A).

(46) The walls of the strip and the jaws are oblique, so that the strip is pressed against the support 6.

(47) The invention is in no way limited by bearing means including jaws for clamping the strip.

(48) For example, in the embodiment shown very diagrammatically in FIGS. 4A and 4B, a housing 60 may be provided fastened to the back of the strip (not represented), this housing being adapted to receive a locking portion 61 or quarter-turn latch. This locking portion includes a cam portion 62 with an oval base and oblique lateral walls 63 so that the cross sections of this cam portion are trapezium-shaped. The housing 60 includes oblique walls 64 intended to come into contact with the walls of the cam portion when this cam portion is in the locking position. The cam portion 62 then exerts a force against the housing 60 and therefore against the strip.

(49) The cam portion goes from an insertion position, as represented in FIG. 4A, to the locking position of FIG. 4B by rotation about an axis A3. The locking portion includes a portion 65 adapted to cooperate with a tool. This portion 65 may define a recess of hexagonal section, for example, so that the locking portion 61 can be driven in rotation by a tool comprising a rod of hexagonal section. Because of the oval shape of the cam portion 62, the oblique walls 63, 64 of the cam portion and the housing then come to bear against one another.

(50) The walls 63, 64 being oblique, a force is then exerted against the strip.

(51) The portion 61 is partially accommodated in an element (not represented) in contact with a support that is not represented. The force exerted by the locking portion 61 presses the strip against this support.

(52) The cam portion may advantageously define a recess that is not represented and is adapted to receive a stop portion when the locking portion is in the locking position. Return means of the spring type (not represented) can enable engagement of the stop portion in the recess, thus locking the cam portion in the locking position.

(53) To replace the strip, it is necessary first to release the cam portion, for example by applying traction to the stop portion, and then to turn the locking portion by one quarter-turn by means of the hexagonal-section tool. The locking portion can then be removed from the housing.