|Title of Invention||
A PANTOGRAPH BOW SLIPPER, A PANTOGRAPH BOW, A PANTOGRAPH AND A METHOD FOR MANUFACTURING THE BOW
|Abstract||The invention concerns mounting bracket (3) of pantograph bow contact (1), designed to bear a current collector (2), characterised in that it comprises, entirely or partly, at least an organic composite containing fibres and an organic matrix. The mounting bracket and the bow contact of the invention are lighter, more corrosion-resistant and easier to produce than those of prior art.|
PANTOGRAPH BOW WITH SLIPPER IN COMPOSITE MATERIAL
Field of the invention
The present invention relates to the pantographs used for collecting current from a fixed electrical conductor, called a "catenary", for a railway vehicle either at a stop or in movement. More particularly, the invention relates to the pantograph bow, which comprises a contact strip intended for electrical contact with the catenary, and the slipper of said bow intended to carry said strip.
State of Prior Art
The pantographs used on railway equipment generally comprise a mobile support device and a bow. The support device holds up the bow and allows to put it in contact with the catenary, which is generally a copper wire, thus ensuring current transfer from the catenary to the vehicle at a stop or in movement. The bow comprises a contact strip, which is generally in carbonaceous material, a slipper and means for electrical connection. The contact strip is typically made of graphite and can be impregnated with copper or with a copper-based alloy.
The slipper, generally made of steel or aluminium, is a rigid support which increases the mechanical hold of the contact strip. In fact, the contact strip alone does not possess sufficient mechanical properties to allow fixation of horns at the ends and does not resist well to the impacts produced by contact with the catenary. This mechanical stress can result in the formation of cracks in the strip, which may lead to rupture of the latter. The slipper is generally
provided with means for fixing it mechanically to the support device.
Assembly of the contact strip and the slipper is usually carried out by brazing. Brazing has the disadvantage of needing the contact strip to be very straight, which can be obtained by operations for flattening, typically including a machining operation, which add to production costs. Brazing itself is also a long and costly operation because it involves several intermediary operations, such as stripping of parts, passivation, sanding and tinning.
The applicant therefore sought means for simplifying the manufacture of the slipper and the bow.
Description of the invention
The slipper of the pantograph bow according to the invention is characterised in that it is constituted, either wholly or partially, of at least one organic composite comprising fibres and an organic matrix.
During research for solutions to the problems posed, the applicant thought of using, for the slipper, a material which is soft at the time of shaping and assembly and which can then be hardened by suitable treatment. In this way, the material can cover the surface irregularities of the contact strip more easily, thus avoiding the need for supplementary smoothing operations of the contact strip. Once hardened, the material increases the mechanical properties of the whole assembly considerably, and avoids the need for a metallic material.
Preferably, at least the part of the slipper touching the contact strip is constituted of said composite. So as to limit the number of parts and to
simplify assembly, the slipper can be built entirely out of said composite.
Another aim of the invention is a pantograph bow comprising a contact strip (or wearing strip) and a slipper according to the invention.
A further aim of the invention is a pantograph comprising at least one bow according to the invention.
The invention also has the aim of a manufacturing method for the bow according to the invention.
Brief description of the figures
Figure 1 shows a typical bow of prior art in contact with a catenary: a) seen from the side; b) seen from below. Figure 2 shows a cross-section relative to the longitudinal direction of the bow (plane A-A in figure 1), of a typical bow of prior art.
Figure 3 shows, diagrammatically, a bow according to the invention: a) seen from the side; b) seen in cross-section relative to the longitudinal direction of the bow.
Figure 4 shows a current-collector bow according to the invention: a) seen from the side; b) seen from above. Figure 5 shows the bow of figure 4 seen along the transversal cross-section B-B. Figure 6 shows an end of the bow of figure 4 along a longitudinal section plane A-A. The discontinuous line shows the profile of a typical end horn fixed on the end of the bow.
Figure 7 shows the stages of a manufacturing method for a bow according to the invention. The elements are seen in transverse section.
A bow 1 of prior art, such as that shown in figures 1 and 2, typically comprises a contact strip 2, a slipper 3, fixation means 4, electrical connection
means 5 and means for detecting damage and wear 6. During use, the contact strip comes into contact with catenary 10 to allow transmission of electrical energy between these two elements. The slipper is typically obtained from a hollow profile. The slipper 3 improves the mechanical hold of the contact strip 2 when the latter is graphite-based, and furthermore makes it possible to fix the bow on the pantograph with fixation means 4, The link between the strip and the slipper typically comprises a weld at the contact surface 7 between the two parts and mechanical blocking through a plastic deformation of a border 8. The bow is generally provided with end horns 9 fixed by means of mechanical fixations 90.
Detailed description of the invention
The slipper 3 of the pantograph bow 1 according to the invention is characterised in that it comprises, either wholly or partially, at least one organic composite comprising fibres and an organic matrix.
Said composite is preferably thermally stable at least up to 300°C. The organic matrix is preferably a polymer resin, and more preferably a thermosetting polymer resin. The fibres can be either organic (such as an aramid fibre), or mineral (such as a glass fibre, a carbon fibre, a boron fibre or a ceramic fibre). For example, said composite can be a phenolic resin filled with glass fibres. The fibres can be of different composition in order to combine their properties advantageously.
The fibres may be short (that is of length comprised typically between 2 and 20 mm) or long (that is, of length typically greater than 20 mm) . In the
case of long fibres, the latter can be constituted of a roving of length closely equal to that of the slipper. A roving is an assembly of base threads arranged closely parallel and grouped without torsion. Long fibres have the advantage of avoiding separation of the pieces if the matrix is ruptured.
Preferably, the matrix and fibres are nonconductors of electricity, making it possible to reduce electric arcing phenomena between the catenary and the slipper. Electric arcs can be produced when the catenary is not touching the contact strip although close to it. These electric arcs can harm the bow at the point of impact.
The thickness E of the base 30 of the slipper 3 is typically comprised between 1 and 10 mm, according to the size of the bow and the composition of the composite. The sides 31 of the slipper can be thinner than the base 30. The slipper 3 may not even comprise sides 31.
The slipper 3 according ' to the invention is able to receive a contact strip (or wearing strip) 2.
Another aim of the invention is a pantograph bow 1 comprising a contact strip 2 and a slipper 3, and characterised in that the slipper 3 is constituted, wholly or partially, of at least one organic composite comprising fibres and an organic matrix.
The contact strip 2 can be a graphite, possibly impregnated with a metal, or can comprise, wholly or partially, a composite C/C material, possibly impregnated with a metal. The impregnating metal can be copper or copper-containing alloy (such as a brass or a bronze) or lead or a lead-containing alloy.
A carbon/carbon (C/C) composite is a solid material comprising carbon fibres (or "fibrous substrate") sunk into a carbon matrix. The carbon fibres are, for example, pitch, fibres, ex-polyacrylonitrile fibres or ex-viscose fibres. These fibres can be of different forms, such as a 2D or 3D textile, a single-direction cloth or random fibres.
The carbon matrix can be obtained according to varying techniques, such as infiltration of a liquid rich in carbon which is followed by pyrolisis to leave a carbonaceous skeleton around the fibres, the operation being repeated as many times as necessary (typically 3 or 4 times) , or by infiltration of a gas rich in carbon under thermodynamic conditions suitable for gas cracking, leaving a pyrolytic carbon deposit on the fibres, or by a combination of these two techniques,
Metal impregnation can be obtained by infiltration of the metal in liquid state into the residual porosity of the graphite or C/C composite (that is, the porosity remaining open after the construction phases of the carbon matrix of the composite) and by solidification of the infiltrated metal. The infiltration is generally carried out in an autoclave, at high pressures (typically from 20 to 200 bars) in order to ensure efficient infiltration of the liquid metal into the porosity•
Generally, the bow also comprises means 4, 11 for mechanical fixation and/or means for electrical connection 51, 52. When the composite is an electrical insulator, the electrical connection means enable efficient transmission of the electrical energy picked up by the contact strip. For example, the electrical
connection can be obtained by at least one screw 52 which, on the one hand, penetrates the contact strip and which, on the other hand, is in electrical contact with at least one connection pin 5,1, generally a metallic pin.
The bow according to the invention can furthermore comprise means 6, 61, 62 for detecting damage to and/or wear of the contact strip, as shown in figures 4 to 6. These means generally comprise a conduit 62, typically a metallic tube or a tube in graphite or C/C composite, in which a detection fluid can circulate according to known techniques. The tube 61 is typically located either in a hole made in the contact strip 2 and substantially longitudinal and parallel to the contact surface 20 of the strip 2, or in a substantially longitudinal groove provided in the surface of the strip 2 which is in contact with the slipper 3, said groove generally being in the central part of the surface 21 opposite to the contact surface 20. The conduit 62 may not comprise a tube 61 and be formed by said hole or said groove through sealing means and/or complementary side-walls.
The bow 1 can be provided with end horns 9 fixed by means of mechanical fixations 9, 91, such as openings 9 and screws 91.
With reference to figure 7, the manufacturing
method according to the invention uses a mould 100
comprising a body 101, 102 and a counter-shape 103
(figure 7A) . According to the invention, said method
introduction of a contact strip 2 in the mould 100 (figure 7B);
- application of a mixture of fibres and resin
(called "prepreg") 110 on the contact band 2
- pressing the prepreg using a counter-shape 103
in such a way as to give it a homogeneous distribution
and to ensure close contact between the strip and the
resin (figure 7D) ;
a hardening operation of the composite by polymerisation. This step can be carried out by heating in a furnace, following a cycle appropriate to the resin used. Advantageously, in practice, the hardening step is carried out leaving the "raw" bow in the mould, which enables control of the final shape of the product;
- removal of the bow thus obtained from the mould
To facilitate the removal operation, the mould (and in particular its body) can be constituted of separate and complementary pieces.
Before introduction of the contact strip in the mould, the method can also comprise an operation of preparation or positioning of the mould in which the counter-shape 103 is separated from the body 101, 102 of the mould 100. This operation can also comprise the formation of the body of the mould (for example by assembling complementary pieces 101, 102) and/or application of a product for facilitating removal from the mould.
The method can comprise an operation for fixing the electrical connection means 51, 52, the mechanical fixation means, 4, 11, and/or the end horns 9.
The method according to the invention has the advantage of allowing simple and rapid manufacturing of
the slipper and the bow according the to invention. It also makes it possible to create a close contact between the slipper and the contact strip, able to provide increased adherence and tight . sealing at the junction between these parts.
A further aim of the invention is a pantograph comprising at least one contact strip 2 according to the invention.
The applicant noted that the mechanical resistance of the bows according to the invention was very high. Typically, with a phenolic resin filled with long glass fibres, and with a base thickness 30 of the slipper of about 2 mm, the bows according to the invention could withstand, without breaking, a load of 400 kg at their centre (according to the three point test which consists of resting the slipper on two support points and then applying a given weight from above at the centre). Furthermore, the junction between the strip (in graphite in the trials) and the resin was very strong and ensured very high cohesion. Shock cycles of 40 kg every 2 seconds for 12 hours did not damage the assembly. Finally, during operation, the bows under test resisted temperatures of the order of 300°C in the case of phenolic resins, which is clearly sufficient for most applications.
The slipper according to the invention also has the advantage of being light, of being resistant to corrosion and of limiting electric arcing phenomena between the catenary and the slipper.
The times taken for producing a special profile for a slipper according to the invention are much shorter than those normally required for producing a metal slipper (typically in steel or in aluminium) following prior art which is generally obtained by extrusion.
The invention facilitates the change of shape of the slipper and the pantograph bow and can assume varying shapes.
The slipper and the bow according to the invention can easily be used for manufacturing restricted series.
If the contact strip ruptures, the slipper according to the invention makes it possible to maintain the unity of the bow, that is the strip slipper assembly.
The bow according to the invention is also very tightly sealed. In particular, it makes it possible to eliminate the risks of water infiltration between the strip and the slipper, which can happen in the bows of prior art comprising a metal slipper and assembled by welding, brazing or gluing and which, in particular, can lead to damage to the bow in the event of freezing.
1. Pantograph bow slipper (3)', pharacterised in that it comprises, wholly or partially, at least one organic composite comprising fibres and an organic matrix.
2. Slipper according to claim 1, characterised in that said matrix is a polymer resin-
3. Slipper according to claim 2, characterised in that said polymer resin is a thermosetting polymer resin.
4. Slipper according to claim 3, characterised in that said thermosetting polymer resin is a phenolic resin,
5. Slipper according to any one of claims 1 to 4, characterised in that said fibres comprise organic fibres.
6. Slipper according to any one of claims 1 to 4, characterised in that said fibres comprise mineral fibres.
7. Slipper according to claim 6, characterised in that said mineral fibres comprise glass fibres.
8. Slipper according to any one of claims 1 to 1, characterised in that it further comprises mechanical fixation means (4, 11) .
9. Slipper according to any one of claims 1 to 8, characterised in that it further comprises electrical connection means (51, 52) .
10. Pantograph bow (1) comprising a contact
strip (2) and a slipper (3) according to any one of
claims 1 to 9.
11. Bow according to claim 10, characterised in that the contact strip (2) is in graphite or in a carbon/carbon composite.
12. Bow according to claim 10, characterised in that the contact strip (2) is in graphite impregnated with a metal or in carbon/carbon composite impregnated with a metal.
13. Bow according to claim 12, characterised in that said metal is copper or a copper-containing alloy, such as a brass or bronze, or lead or a lead-containing alloy.
14. Bow according to any one of claims 10 to 13, characterised in that furthermore it contains means (6, 61, 62) for detecting damage to and/or wear of the contact strip.
15. Pantograph comprising at least one bow (1) according to any one of claims 10 to 14.
16. Method for manufacturing the bow according to any one of claims 10 to 14, characterised in that it comprises:
- introduction of a contact strip (2) in the
mould (100) comprising a body (101, 102) and a counter-
shape (103) ;
- application of a mixture of fibres and resin, or "prepreg", (110) on the contact band 2;
- pressing the prepreg using a counter-shape (103) in such a way as to give it a homogeneous distribution and to ensure close contact between the strip and the resin;
a hardening operation of the composite by polymerisation;
- removal of the bow from the mould.
17. Method according to claim 16, characterised in that the mould is constituted of separate and
complementary pieces (101, 102).
18. Pantograph bow slipper substantially as herein described with
reference to the accompanying drawings.
19. Method of manufacturing the bow substantially as herein
described with reference to the accompanying drawings.
|Indian Patent Application Number||IN/PCT/2002/1815/CHE|
|PG Journal Number||35/2007|
|Date of Filing||06-Nov-2002|
|Name of Patentee||M/S. CARBONE LORRAINE APPLICATIONS ELECTRIQUES|
|Applicant Address||10 Avenue Roger Dumoulin F-80080 Amiens (FR).|
|PCT International Classification Number||B60L 5/20|
|PCT International Application Number||PCT/FR2001/000996|
|PCT International Filing date||2001-04-03|