Patent Description:
Known electric railroad vehicles, such as tramways or metros, are generally supplied with electric energy through a rigid overhead catenary system, also called ROCS in short. A ROCS comprises a contact wire, usually made out of copper or one of its alloys, that is rigidly held by a conductive profile, also called busbar. Common busbars are made out of lightweight conductive metal, such as aluminum or one of its alloys. To ensure a good geometric alignment of the contact wire relatively to the rail track, each busbar holds the contact wire continuously and is held by hanger clamps. The hanger clamps are fixed to the infrastructure of the railtrack, for example to a ceiling of a tunnel section or to a steel cantilever linked to the trackside, so that the contact wire is hanging downwardly, the contact wire being arranged along a longitudinal direction parallel to the railtrack.

To avoid electric discharges between the busbar and the hanger clamp and/or the steel cantilever, the busbar and the hanger clamp are electrically connected together, to ensure that the same electric potential is present on the hanger clamp and on the busbar.

In addition, since the busbars are continuous and made from metal, the busbars show relatively high dimensional variations due to the temperature changes, caused for example by seasonal variations or by self-heating when an electric current flows through the ROCS. To avoid local stress and/or deformations, the busbar held by the hanger clamps is allowed to slide relatively to the hanger clamps along the longitudinal direction.

To cope with these two problems, <CIT> describes, for example, a hanger clamp that comprises inserts made from carbon/graphite composite materials. Such inserts are costly to produce and remain relatively brittle, requiring regular maintenance.

The document <CIT> describes also a similar hanger clamp.

The document <CIT> describes a hanger clamp with a plastic material with a small frictional resistance, but with insulating characteristics.

There is a need for an improved hanger clamp, with better durability.

To this end, aspects of the invention pertains to a hanger clamp for holding a conductive profile of a rigid overhead catenary system belonging to a railtrack, the hanger clamp comprising:.

According to the invention, the inserts are made from a material comprising a synthetic polymer and a conductive charge.

Thanks to the invention, the inserts are both cheap to produce and resilient, thus improving the cost price and the durability of the hanger clamp. Thanks to the conductive charge, the busbar held by the hanger clamp and the hanger clamp present the same electrical potential, which reduces the risk of electrical arc, while the synthetic polymer allows sliding of the busbar relatively to the hanger clamp in the longitudinal direction.

According to advantageous but optional aspects, such a hanger clamp may incorporate one or more of the following features, considered alone or according to any combination according to the appended claims.

The invention also concerns rigid overhead catenary system, comprising a contact line held by a conductive profile, the conductive profile being held by hanger clamps, wherein at least one hanger clamp is as described here above.

Other aspects of the invention concerns a railtrack, comprising a track and a rigid overhead catenary system as described here above.

The invention will be better understood, and other advantages thereof will appear more clearly, in light of the following description of one embodiment of an hanger clamp, a rigid overhead catenary system and a railtrack according to the invention, this description being provided solely as a non-limiting example and done in reference to the appended drawings, in which:.

<FIG> represents a railtrack <NUM>. The railtrack <NUM> comprises two rails, which are parallel to each other. Only one rail <NUM> is visible on <FIG>, and is supposed to be straight and horizontal.

The railtrack <NUM> is configured to have a vehicle <NUM> running on the rails <NUM>. The vehicle <NUM> is for example a rail electric vehicle, such as a train, a metro, or a tramway, and comprises wheels <NUM> that are powered by an electric motor. The electric motor is not shown. Alternatively, the vehicle <NUM> runs on tires, and the rails <NUM> are replaced by guideways.

The railtrack <NUM> comprises a rigid overhead catenary system <NUM>, also called ROCS <NUM> within the present description, configured to supply the vehicle <NUM> with electric energy.

To this end, the vehicle <NUM> comprises an electricity collection device <NUM>, such as a pantograph, which comes into contact with the ROCS <NUM> to collect electrical energy. In the example illustrated on <FIG>, the electricity returns to the railtrack <NUM> through the wheels <NUM>.

The ROCS <NUM> is fixed relative to the rails <NUM>, more precisely the ROCS is arranged above the rail <NUM> at a fixed height, so that the electricity collection device <NUM> works properly when the rail vehicle <NUM> moves.

The ROCS <NUM> comprises a contact wire <NUM> and a busbar <NUM>. The contact wire <NUM> is configured to be in contact with the electricity collection device <NUM> and is made from conductive metal, preferably from copper or copper alloy, to ensure a low electric resistance. The wire <NUM> forms a contact line for the ROCS <NUM>.

The contact wire <NUM> presents a cylindrical shape extending along a longitudinal axis A110, which is parallel to the rail <NUM>. The contact wire <NUM> is held by the busbar <NUM>, preferably continuously and rigidly held, so that the contact wire <NUM> does not flex when the current collection device <NUM> is pressing onto the contact wire <NUM>.

The busbar <NUM> is a conductive profile, which extends along a longitudinal axis A120, parallel to the longitudinal axis A110 of the wire <NUM>. The busbar <NUM> is preferably made from a lightweight and conductive metal such as aluminum or an aluminum alloy. The busbar <NUM> is usually produced by extrusion.

The ROCS <NUM> further comprises hanger clamps <NUM>, which are for example fixed to a ceiling <NUM> of a tunnel section of the railtrack <NUM>, above the rail <NUM>. In other words, the ROCS <NUM> is suspended to the ceiling <NUM>.

The busbar <NUM> extends downwardly from the clamps <NUM>, and the contact wire <NUM>, held by the busbar <NUM>, faces the ground. In a not shown alternative, the ROCS <NUM> is attached to a beam belonging to a mast, the mast being arranged on the trackside and the beam extending above the rail <NUM>.

Within the scope of this description, it is assumed that the longitudinal axis A120 is horizontal, and that the busbar <NUM> hangs vertically. Of course in reality the actual orientation of the busbar <NUM> may vary, for example in slope sections or in curve sections of the railtrack <NUM>.

The ROCS <NUM> is further detailed with reference to <FIG>.

The contact wire <NUM> presents a globally round profile, with two slits <NUM> configured to cooperate with clamping tips of the busbar <NUM>, as described later.

The busbar <NUM> comprises a base plate <NUM>, which is configured to cooperate with the hanger clamps <NUM>. The base plate <NUM> has flat and elongated shape, that extends along a median plane P122 and that is arranged along the longitudinal axis A120 of the busbar <NUM>. The medial plane P122 is supposed to be horizontal. The base plate <NUM> comprises two side edges 122A and 122B, which are parallel to a longitudinal plane P120, which is orthogonal to the median plane P122 and parallel to the longitudinal axis A120.

The busbar <NUM> further comprises two holding arms <NUM>. The holding arms <NUM> extend from the base plate <NUM> on the same side of the median plan P122, here from a downward side of the base <NUM>. Each holding arm <NUM> comprises a main portion <NUM> and a clamping portion <NUM>.

In the illustrated example, the main portions <NUM> are parallel to the longitudinal plane P120. The two clamping portion <NUM> converge toward each other and comprise each a clamping tip <NUM>, which cooperate with a respective slit <NUM> of the contact wire <NUM>.

The hanger clamp <NUM> comprises a connecting portion <NUM> and a clamping portion <NUM>. Only a threaded portion <NUM> and a nut <NUM> of the connecting portion <NUM> are represented on <FIG>.

The connecting portion <NUM> is configured to cooperate with an element of the railtrack <NUM>, such as a beam or a tunnel ceiling, etc., in order to connect the clamping portion <NUM> to the railtrack <NUM>, in particular in order to adjust the height of the clamping portion <NUM> above the railtrack <NUM>.

The clamping portion <NUM> is made of metallic lightweight material such as an aluminum alloy. The clamping portion <NUM> is configured to receive the base plate <NUM> of the busbar <NUM>. In other words, the clamping portion <NUM> is configured to connect said base plate <NUM> to a fixed element of the railtrack <NUM>.

When the base plate <NUM> is received in the clamping portion <NUM>, the clamping portion <NUM> extends along a plane that is aligned with the median plane P122, and the clamping portion <NUM> has a cylindrical shape, with a rectangular cross section, extending along an axis that is parallel to the longitudinal axis A120.

The clamping portion <NUM> comprises two jaws <NUM>. The two jaws <NUM> have preferably the same shape and are reversibly assembled to each other with fixing organs <NUM>, such as nuts and bolts.

The two jaws <NUM> are arranged symmetrically from each other apart the longitudinal plane P120. Each jaw <NUM> has a cylindrical shape with a "U" profile extending along the longitudinal axis A120, the jaws <NUM> facing each other with the opening of the "U" being oriented toward the longitudinal plane P120. Each jaw <NUM> defines a reception volume V222, configured to receive a respective side edge 122A or <NUM> of the base plate <NUM>.

The hanger clamp <NUM> further comprises two inserts <NUM>, each insert <NUM> being received within the reception volume V222 of a respective jaw <NUM>. in the illustrated example, each insert <NUM> has a cylindrical shape with a "U" profile extending along the longitudinal axis A120 in the mounted configuration of the hanger clamp <NUM>.

When the base plate <NUM> is received in the clamping portion <NUM>, the inserts <NUM> are sandwiched between the base plate <NUM> and the jaws <NUM>, so that the base plate <NUM> does not contact directly the jaws <NUM>. The inserts <NUM> are in contact with the base plate <NUM> without pressing on the surface of the base plate <NUM>, so that translation movements of the base plate <NUM> relative to the hanger clamp <NUM> along any direction radial to the longitudinal axis A120 are prevented, while translation movements the base plate <NUM> relative to the hanger clamp <NUM> along the longitudinal axis A120 are allowed.

In other words, the base plate <NUM> is just leaning on the inserts <NUM> without additional forces except the busbar <NUM> own weight. Preferably, an air gap is arranged between the inserts <NUM> and the surface of the base plate <NUM>. The air gap allows the free sliding of the busbar <NUM> relative to the clamping portion <NUM>, and also the free orientation of the busbar <NUM> when the busbar <NUM> is curved, for example to follow curved tracks and for staggering.

Each insert <NUM> is received within a respective reception volume V222 and is configured to be positioned between the corresponding jaw <NUM> and the base plate <NUM>, while allowing sliding movements of the busbar <NUM> relative to the hanger clamp <NUM> along the longitudinal axis A120.

The inserts <NUM> are mare from a material comprising synthetic polymer, that is selected for a low friction coefficient and high wear resistance, so that when the inserts <NUM> is in contact with a surface of the base plate <NUM>, sliding movements of the busbar <NUM> relative to the hanger clamp <NUM> along the longitudinal axis A120 are allowed.

Each insert <NUM> is also configured to conduct electricity between the base plate <NUM> and the clamping portion <NUM>. Synthetic polymers used in railroad applications are usually electrically insulating. However, within the scope of the present invention, the material of the inserts <NUM> comprises a conductive charge, so that the material of the inserts <NUM> is conductive enough so the clamping portion <NUM> and the busbar <NUM> have the same electric potential.

in the field of polymers, a charge is a mass of material, usually in the shape of fine powder or fibers, that is dispersed in a polymer material to reduce the cost and/or to adjust the properties of said polymer material, for example to adjust mechanical properties, density, thermal resistance, etc..

Practically, the material of the inserts <NUM> has an electrical resistance lower than <NUM> kΩ - kilo-ohms -, preferably lower than <NUM> kQ. in other words, the inserts <NUM> are configured to conduct electricity between the base plate <NUM> and the clamping portion <NUM>.

The conductive charge is preferably in the shape of fiber, to contribute also to the strength of the material of the inserts <NUM>. More preferably, the conductive charge comprises carbon fibers, which are electrically conductive and contribute to improve the tensile strength of the polymer material.

The polymer material of the inserts <NUM> is preferably a thermoplastic polymer. Compared to other types of polymers, such as thermosetting polymers, thermoplastic polymers show a better mechanical behavior in terms of wear resistance, toughness or thermal resistance. A good example of thermoplastic polymer for the material of the inserts <NUM> is polyamide.

Raw materials comprising polyamide with carbon fibers added as a charge are, for example, commercially available from LATI Company under the brand name "LatiOhm".

Claim 1:
A hanger clamp (<NUM>) for holding a conductive profile (<NUM>) of a rigid overhead catenary system (<NUM>) belonging to a railtrack (<NUM>), the hanger clamp (<NUM>) comprising:
- a clamping portion (<NUM>), preferentially made of an aluminum alloy, configured to receive a base plate (<NUM>) of the conductive profile (<NUM>), the clamping portion (<NUM>) extending along a median plane (P122) and along a longitudinal axis (A120), which is parallel to the median plane,
- a connecting portion (<NUM>), configured to connect said base plate (<NUM>) to a fixed element of the railtrack (<NUM>), such as a beam or a tunnel ceiling (<NUM>),
wherein the clamping portion (<NUM>) comprises two jaws (<NUM>), each jaw (<NUM>) having a U profile extending along the longitudinal axis (A120) and facing each other, each jaw defining a reception volume (V222) configured to receive a respective edge (122A, 122B) of the base plate (<NUM>),
wherein the hanger clamp (<NUM>) further comprises two inserts (<NUM>), each insert being received within a respective reception volume (V222) and being configured to be positioned between the corresponding jaw and the base plate while allowing sliding movements of the conductive profile (<NUM>) relative to the hanger clamp (<NUM>) along the longitudinal axis, each insert being also configured to conduct electricity between the base plate (<NUM>) and the clamping portion (<NUM>),
characterized in that the inserts (<NUM>) are made from a material comprising a synthetic polymer and a conductive charge.