Patent Application
20140305924
This application is based on and hereby claims the benefit under 35 U.S.C. ยง119 from German Patent Application No. DE 202013101624.1, filed on Apr. 16, 2013, in the German Patent Office. This application is a continuation-in-part of German Patent Application No. DE 202013101624.1, the contents of which are incorporated herein by reference.
The present invention relates to a heatable current collector for establishing an electrical contact between a current carrying line and an electric vehicle as well as to a heating device for use in the heatable current collector.
Current collectors of electric vehicles, such as electrically operated locomotives and streetcars, as well as current carrying lines, such as overhead railway lines for supplying electric vehicles with electrical current for operating the vehicles, are exposed to the effects of weather. A frost or ice layer can form on the current collector or on the current carrying line and interfere with or even prevent the electrical contact between the current collector and the line. Devices are known for de-icing outdoor wire lines that beat the wires, expose the wires to a long lasting uninterrupted vibration, or heat the wires by short-circuiting certain sections of the line. A disadvantage of devices that beat or vibrate the wires is that the lifespan of the line wires is shortened. A disadvantage of devices that heat the wires is that they have to be very powerful, and the operation of electric vehicles has to be interrupted while the section of a line is short-circuited. The German Patent No. DE2324387 discloses a de-icing device for de-icing the surfaces of exposed line wires that is supported by a lifting mechanism arranged on the roof of an electric vehicle. The de-icing device includes a means, in particular an inductor, for generating pulses of an electric field at time intervals. The means is arranged in the immediate vicinity of the surface to be de-iced and causes a resilient deformation of the surface so that the ice layer is chipped off. A disadvantage of this de-icing device is that it only effectively removes an ice layer but not a frost layer.
German Utility Model DE7029001 discloses a current collector for a crane that can be moved along a current rail and that has a sliding body applied against the current rail for establishing an electrical contact with the current rail. The sliding body has bored holes that are formed in a direction perpendicular to the current rail. A heating cartridge can be inserted into each of the bored holes. When a frost or ice layer forms on the current rail, an electrical current is supplied to the heating cartridge, which becomes warm and heats the sliding body and the current rail in the vicinity of the heating contact site between the sliding body and the current rail. A disadvantage of this solution is that the diameter of the bored hole must be sufficiently large so as to accommodate the heating cartridge in a heated and consequently thermally expanded state. When the heating cartridge is in a comparatively colder state, it contacts the inner surface of the bored hole only in a limited area in a support surface of the heating cartridge as opposed to ideally contacting the full surface of the bored hole around the heating cartridge, which would be desirable for an optimal heat transfer from the heating cartridge to the inner surface of the bored hole. It is also disadvantageous that the heating device in a colder state is not firmly connected to the inner surface of the bored hole. Due to the air gap between the surface of the heating cartridge and the inner surface of the bored hole, there is poor thermal contact with the inner surface of the bored hole. Furthermore, there is the disadvantage that the heating cartridge used in the colder state can rotate and/or be axially shifted in the bored hole.
A de-icing device is sought that solves the problems associated with heatable current collectors having bored holes that receive heating devices. A heating device is sought that can easily be inserted into a bored hole and secured after its insertion.
A heatable current collector for establishing an electrical contact between a current carrying line and an electric vehicle includes a sliding contact rail arranged substantially transversely to the current carrying line. The sliding contact rail has a bored hole in which an electrically operated, elongated heating element is disposed. The heating element occupies only a portion of the cross section of the bored hole. The heating element is connected to a clamping device that presses the heating element against the inside surface of the bored hole. A heating device for the heatable current collector has a substantially rigid, rod-shaped heating element with an electrical resistance heating conductor and two free ends. The heating device includes an inherently stable, resilient and thermostable hose that is sealed off at one end. The sealed off end of the hose is firmly connected to one of the free ends of the heating element.
In another embodiment, the heatable current collector for establishing an electrical contact between a current carrying line and an electric vehicle includes a lifting mechanism, a sliding contact rail, a rod, an electrical resistance heating conductor, and insulating layer and a resilient hose. The sliding contact rail is mounted on the lifting mechanism and has a hole disposed longitudinally through the rail and perpendicular to the current carrying line. The electrical resistance heating conductor is helically arranged in grooves of an outer threading of the rod. The insulating layer is a shrink hose that covers the rod and the electrical resistance heating conductor. The insulating layer is electrically insulating and heat permeable. One end of the resilient hose is sealed off and is connected to an end of the rod. The rod, the electrical resistance heating conductor, the insulating layer and the resilient hose are disposed in the hole. The rod, the electrical resistance heating conductor and the insulating layer occupy only a portion of the cross section of the hole. The resilient hose presses the rod, the electrical resistance heating conductor and the insulating layer against the inside surface of the hole.
The hole in the sliding contact rail is formed so close beneath a surface of the rail that faces the current carrying line that a section of the hole forms a slit in the surface facing the line. The resilient hose is disposed in the hole opposite the rod and pushes the rod, the electrical resistance heating conductor and the insulating layer towards the slit. The slit has a width that is smaller than the diameter of the rod.
Other embodiments and advantages are described in the detailed description below. This summary does not purport to define the invention. The invention is defined by the claims.
The accompanying drawings, where like numerals indicate like components, illustrate embodiments of the invention.
Reference will now be made in detail to some embodiments of the invention, examples of which are illustrated in the accompanying drawings.
The heating element 18 is connected to a clamping device 20 that presses the heating element 18 against the inside surface 16 of the bored hole 14. The clamping device 20 secures the heating element 18 inside the bored hole 14. By pressing the heating element 18 against the inside surface 16 of the bored hole 14, the heat transfer from the heating element 18 to the inside surface 16 of the bored hole 14 is improved.
In one embodiment, the clamping device 20 is an inherently stable, resilient and thermostable hose 22. Due to its inherent stability, the hose 22 can also be easily introduced into the bored hole 14. Due to its resilience, the hose 22 takes on shape changes (expansion and contraction) of the heating element 18 that occur due to temperature changes. The resilience of the hose 22 improves heat transfer from the heating element 18 to the inside surface 16 of the bored hole 14 by ensuring that the heating element 18 is pressed against the inside surface 16 of the bored hole 14 even at different temperatures or in the event of different shapes of the heating element 18. Due to its thermostability, the hose 22 maintains its functionality even at the high temperatures that occur during the heating operation of the heating element 18.
The heating element 18 is designed as a substantially rigid rod 28 with two free ends. Due to its design as a rigid rod, the heating element 18 can easily be introduced into and removed from the bored hole 14, for example, when replacing the heating element 18.
The inherently stable resilient hose 22 is positioned along the rod-shaped heating element 18 and is firmly connected to a free end of the heating element 18. As a result of this design, the hose 22 together with the heating element 18 can in one simple work step be introduced into and removed from the bored hole 14 of the sliding contact rail 10.
The hose 22 can be sealed off at one end, and the sealed-off end of the hose 22 can be connected to a free end of the rod-shaped heating element 18. This design allows the inner volume of the hose 22 to be evacuated at its other free end so that the outer diameter of the hose 22 is decreased during the evacuation. As a result of the firm connection of the sealed end to one of the free ends of the heating element 18, the hose 22 together with the heating element 18 can easily be inserted in its evacuated state into the bored hole 14, shifted, and then pulled out.
The bored hole 14 in the sliding contact rail 10 can be formed so close beneath the surface of the sliding contact rail 10 that a slit is formed by a section of the bored hole 14. The width of the slit is selected to be smaller than the diameter of the heating element 18 so that the heating element 18 can reliably be held in the bored hole 14. The clamping device 20 in the bored hole 14 is arranged on the side of the heating element 18 opposite the slit so that the clamping device 20 presses the heating element 18 in the direction of the slit. A portion of the section of the heating element 18 that is exposed at the slit can protrude out of the slit so that the portion protruding out of the slit can be in direct contact with the current carrying line 4.
Alternatively, the bored hole 14 in the sliding contact rail 10 can be formed so far beneath the surface of the sliding contact rail 10 that is turned toward the line 4 that the bored hole 14 is disposed completely within the sliding contact rail 10, but preferably in the vicinity of the surface of the sliding contact rail 10 that is turned toward the line 4.
According to a second aspect, the invention provides a heating device for the heatable current collector 2 described above. The heating device includes a substantially rigid, rod-shaped heating element 18 with an electrical resistance heating conductor and two free ends.
The heating element 18 further includes an inherently stable, resilient and thermostable hose 22 that is sealed off at one end. The sealed off end of the hose 22 is firmly connected to one of the free ends of the heating element 18. As explained above, the hose 22 can easily be introduced into the bored hole 14 due to its inherent stability. As a result of its resilience, the hose 22 takes on shape changes (expansion and contraction) of the heating element 18 that occur as a result of temperature changes. The resiliency of the hose 22 ensures that the heating element 18 is pressed against the inside surface 16 of the bored hole 14 so as to improve the heat transfer from the heating element 18 to the inside surface 16 of the bored hole 14 even for different shapes of the heating element 18 and at different temperatures. The thermostability of the hose 22 maintains its functionality even at the high temperatures that occur in the heating operation of the heating element 18. By sealing off the hose 22 at a free end, the inner volume of the hose 22 can be evacuated from its other free end so that the outer diameter of the hose 22 is decreased during the evacuation. The firm connection of the sealed off end to one of the free ends of the heating element 18 allows the hose 22 in the evacuated state to be introduced in a particularly easy way together with the heating element 18 into the bored hole 14 and removed therefrom.
The heating element 18 includes a rod 28 with an outer threading 34. The electric resistance heating conductor can be inserted into the grooves of the outer threading 34. As a result of the insertion of the resistance heating conductor into the grooves of the outer threading 34, the windings of the resistance heating conductor are connected to the rod 28 in a stable position with respect to the rod 28. Owing to its helical course, the outer threading 34 has a length that is much greater than the rod 28. A resistance heating conductor having a much greater length relative to the length of the rod 28 and a correspondingly greater heating capacity is thereby accommodated into the heating element 18. By making the rod 28 from Teflon, the rod 28 becomes thermostable and the outer threading 34 is easily formed in the relatively soft material (Teflon).
The outer side of the rod 28 with the electrical resistance heating conductor is coated with an electrically insulating and heat permeable layer 48. The insulating layer 48 is formed as an outer sheath of the heating element 18 and provides the heating element 18 with electrical insulation with respect to the outside. The electrical insulation provides protection to the person installing the heating device in the bored hole 14 of a sliding contact rail 10. The insulating layer 48 also permits the electric uncoupling of the heating device in the bored hole 14 from the electric current flowing in the sliding contact rail 10 during the operation of the current collector 2.
The electrically insulating and heat permeable layer 48 is designed as a shrink hose 50 that can easily be pulled in an expanded state over the rod 28 and subsequently shrunk. When the layer 48 is shrunk, it binds firmly to the rod 28, which is then enclosed by the layer 48. The electrically insulating and heat permeable layer 48 includes a layer made of PTFE for the electrical insulation with respect to high voltage.
At the two free ends of the heating element 18, the resistance heating conductor is connected in each case to an electrical feed line 38, i.e., to an electrical line for the current supply. The feed line 38 includes a high-voltage wire for feeding a heating current to the heating element 18 and an insulation layer that insulates sufficiently against the high voltage and the high current from the current carrying line 4. Several heating elements 18 or heating devices can be electrically connected one after the other (series connected) using such feed lines. The heating elements and heating devices that are electrically connected one after the other can be arranged axially one after the other in a bored hole 14 and/or they can be arranged in two or more bored holes formed parallel to one another. At the two free ends, the heating element 18 can be sealed off using silicone seals in order to protect against environmental and weather influences.
The heating element 18 can also include a reinforcement element, such as a strain relief device that extends in the longitudinal direction of the heating element 18. The reinforcement element is used to absorb mechanical stresses, particularly tensile stresses that act on the heating element 18. The reinforcement element is arranged within the insulating layer 48 or radially within the layer, for example, enclosed by the layer together with the rod 28. The feed lines 38 can also comprise suitable second reinforcement elements (strain relief elements). It is also possible to provide a strain relief device around a section in which one end of a feed line 38 is connected in an electrically conducting manner to an end of the resistance heating conductor.
The hose 22 of the clamping device 20 can be a silicone hose 22 that radially contracts and is flattened due to the application of a vacuum so that the heating device, i.e., the heating element 18 together with the clamping device 20 (the hose), can easily be introduced into a bored hole 14 in the sliding contact rail 10. If the vacuum is broken after the heating element 18 is introduced into the hole, then the hose 22 expands and pushes the heating element 18 against the inside surface 16 of the bored hole 14 opposite the hose 22. By mounting the heating element 18 in the bored hole 14 resiliently against the hose 22, the heating element 18 can reliably withstand the shocks and vibrations of the sliding contact rail 10 during operation. Furthermore, the heating device can easily be removed again from the bore, for example, during maintenance when a replacement heating device is installed.
Due to the helical arrangement of the resistance heating conductor in the grooves of the outer threading 34 of the rod 28, the rod-shaped structure of the heating element 18 reaches a maximized heating surface area, which in turn allows the operation at lower heating temperatures and for longer lifespans. Naturally, the materials incorporated in the heating device are robust and resistant with regard to the expected operating temperatures, even in the case of long lasting, continuous use.
A third embodiment involves a heatable current collector 2 that establishes an electrical contact between a current carrying line 4 and an electric vehicle 6. The current collector 2 includes a sliding contact rail 10 arranged substantially transversely to the current carrying line 4 and a lifting mechanism 8 on which the sliding contact rail 10 is mounted. The sliding contact rail 10 includes a bored hole 14 in which an electrically operated heating device is located that occupies only a portion of the cross section of the bored hole 14. The current collector 2 includes the heating device described above.
A bored hole 14 is formed in the sliding contact rail 10 and extends in the longitudinal direction of the sliding contact rail 10. A heating device 12 is arranged in the bored hole 14. The heating device 12 includes an electrically operated, elongated heating element 18 and a clamping device 20. The elongated heating element 18 occupies only a portion of the cross section of the bored hole 14. The heating element 18 is connected to the clamping device 20, which presses the heating element 18 against the inside surface 16 of the bored hole 14.
Electrical current (heating current) is supplied to the heating device 12 through a first feed line 38, which leads out of the electric vehicle 6. The heating current is returned via a second feed line (not shown) back into the electric vehicle 6. The electric vehicle 6 houses a switching and control device (not shown) for switching on and off and for controlling the strength of the heating current supplied to the heating device 12.
The heating current is switched on if an ice or frost layer forms on the sliding contact rail 10 as a result of exposure to weather. The heating device 12 heats the sliding contact rail 10 and causes the ice or frost layer to melt. If the weather conditions are such that an ice or frost layer is likely to form on the sliding contact rail 10 during the operation of the electric vehicle 6, the heating current is switched on so that the heating device 12 heats the sliding contact rail 10, and the formation of an ice or frost layer on the heated sliding contact rail 10 is prevented. As a result of the contact of the sliding contact rail 10 with the line 4, heat energy generated by the heating device 12 can also propagate into the line 4 and contribute to the removal of any ice or frost layer formed on the line 4.
The two heating elements 18a and 18b are arranged one after the other and enclosed by a common electrically insulating and heat permeable layer 48, which is continuous in the direction extending over the two heating elements 18a and 18b. The insulating layer 48 is formed as a shrink hose 50. The clamping device 20 is designed as an inherently stable, resilient and thermostable hose 22 and extends in the longitudinal direction along the two heating elements 18a and 18b. In this manner, the clamping device 20 pushes the two heating elements 18a and 18b against the inside surface 16 of the bored hole 14. At one end (on the right in
As shown in
To connect an end of a feed line 38 to an end of the resistance heating conductor 36, a longitudinal section of the insulation layer 44 is removed so that the core wire 40 is exposed. Then the exposed core wire 40 is connected in an electrically conducting manner to the end of the resistance heating conductor 36 using a connection element 44 that has a luster terminal and/or a fuse. A protective sheath 46 is shifted in each case over the connection sections formed at the two free ends 30 and 32 of the heating element 18. After the two ends of the resistance heating conductor 36 are connected, the insulating layer 48 is pulled over the connection section at the free end 30, over the rod 28 with the heating resistance conductor 36 in the grooves of the outer threading 34, and over the connection section at the other free end 32 of the heating element 18. Subsequently, a shrink hose 50 in its expanded state is pulled and shrunk over the connection section at the free end 30, over the rod 28, and over the connection section at the other free end 32 of the heating element 18. In a section in which the insulating layer 48 and the shrunk hose 50 enclose the insulating sheath 42 of the feed line 38, the sealed off end 24 of the hose 22 is attached to the free end 30 of the heating element by wrapping a wrapping element 54, such as an adhesive tape, around the sealed off end 24 of the hose 22 together with the aforementioned section.
In order to install the resulting premounted heating installation 12 into a prefabricated sliding contact rail 10 of a current collector 2, the bored hole 14 in which the heating device 12 is to be accommodated is first produced as a through hole in the longitudinal direction of the sliding contact rail 10. For the embodiment shown in
Then the hose 22 is evacuated from its open second end opposite from the sealed off first end 24. Thus, the air contained in the inner space of the hose 22 is pumped out and a low pressure is generated. The heating device 12 with the feed line 38 connected at the free end 30 to the sealed off end 24 of the hose 22 is then pushed into the bored hole 14 until the feed line 38 and the free end protrude at the opposite end of the bored hole 14. If necessary, the heating device 12 in the bored hole 14 is rotated about its the longitudinal axis until the heating element 18 is located at the desired position on the inside surface 16 of the bored hole 14, such as against the slit 60. The evacuation of the inner space of the hose 22 is terminated so that the hose 22 expands owing to its resilience. The heating element 18 is pressed against the inside surface 16 of the bored hole 14 and pushes partially through the slit 60 as shown in
A heatable current collector for establishing an electrical contact between a current carrying line and an electric vehicle includes a sliding contact rail arranged substantially transversely to the current carrying line. The sliding contact rail includes a bored hole in which an electrically operated, elongated heating element is disposed that occupies only a portion of the cross section of the hole. The heating element is connected to a clamping device that presses the heating element against the inside surface of the bore. The invention also includes a heating device for the heatable current collector. The heating device has a substantially rigid, rod-shaped heating element with an electrical resistance heating conductor and two free ends. The heating device also has an inherently stable, resilient and thermostable hose that is sealed off at one end. The sealed off end of the hose is firmly connected to one of the free ends of the heating element.
Although the present invention has been described in connection with certain specific embodiments for instructional purposes, the present invention is not limited thereto. Accordingly, various modifications, adaptations, and combinations of various features of the described embodiments can be practiced without departing from the scope of the invention as set forth in the claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202013101624.1 | Apr 2013 | DE | national |
