US3830990A

US3830990A - Pantograph wearing strip support

Info

Publication number: US3830990A
Application number: US00316913A
Authority: US
Inventors: R Gray
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1972-12-20
Filing date: 1972-12-20
Publication date: 1974-08-20
Anticipated expiration: 1991-08-20
Also published as: FR2211362A1; DE2362822A1; CA974308A; FR2211362B3

Abstract

A pantograph shoe has a plurality of wearing strips each being independently supported by elastic members preloaded against stops to provide a high average force against the contact wire while retaining the desired low spring constant within the working range. The high average force, resulting from a relatively large pre-displacement, counteracts the constant pushup force on the pantograph frame plus the aerodynamic lift of the pantograph plus the dynamic forces due to varying contact wire profile at high speeds. The low spring constant provides for a ''''soft shoe'''' which is flexible to the changes in pressure due to variation in the contact wire profile, and it prevents separation that would otherwise occur at high speeds.

Description

United States Patent Gray [ Aug. 20, 1974 PANTOGRAPH WEARING STRIP SUPPORT [75] Inventor: Richard Thurby Gray, Erie, Pa.

[73] Assignee: General Electric Company, Erie, Pa.

[22] Filed: Dec. 20, 1972 [21] Appl. No.: 316,913

Primary Examiner-M, Henson Wood, Jr.

Assistant ExaminerD. W. Keen Attorney, Agent, or Firm-Walter C. Bernkopf; Dana F. Bigelow [5 7] ABSTRACT A pantograph shoe has a plurality of wearing strips each being independently supported by elastic members preloaded against stops to provide a high average force against the contact wire while retaining the desired low spring constant within the working range. The high average force, resulting from a relatively large are-displacement, counteracts the constant pushup force on the pantograph frame plus the aerodynamic lift of the pantograph plus the dynamic forces due to varying contact wire profile at high speeds. The low spring constant provides for a soft shoe which is flexible to the changes in pressure due to variation in the contact wire profile, and it prevents separation that would otherwise occur at high speeds.

21 Claims, 12 Drawing Figures PATEN IE0 2 0 i974 SPRING FORCE $830,990 SHEEI 20$ .4

FIG. 3

IIIIII b FIG. .5

RANGE OF WORK/N6 DISPLACEMENT RANGE OF FORCE l VARIATION AVERAGE SUPPORT/N6 FORCE" CLAMP/N6.

FORCE I i X DISPLACEMENT FROM CLAM PED POSITION P I I PAIENIEBmszomn V RANGE OF won/(we I DISPLACEMENT 1 F/G 9 RANGE 05 FORCE g VARIATION l U I O: l 3 3 o z AVERAGE I E SUPPORT/N6. v FORCE PRELOAD i FORCE 1 i l I 0 v VERTICAL DISPLACEMENT FROM PRELOADED POSITION 0.06- roams LINKAGE APPLIED rams vs o/s mcsumr 0,05 //v omens/amass ram 1 PANTOGRAPH WEARING STRIP SUPPORT BACKGROUND OF THE INVENTION This invention relates generally to power collection systems and more particularly to pantographs for transmitting power from a wayside contact wire to a high speed vehicle.

A customary approach to collecting relatively heavy currents from an overhead conductor for propelling an electrically operated vehicle, such as a transit car or comotive is to utilize a current collector of the pantograph type having a plurality of slider shoes mounted on a pantograph structure for engaging the contact wire. Because of the irregularities in the construction and suspension of the overhead contact wire there is a tendency in the pantograph structure of the prior art to move out of engagement with the conductor wire and thereby disrupt the flow of current therebetween. This tendency is accentuated with increases in vehicle speed, and may become prohibitive when operating at speed ranges in excess of 100 mph. In addition to the increased relative speed of the engaged catenary and collector shoe members, with the attendant propensity for separation, the aerodynamic forces acting on the pantograph also affect its disposition with respect to the conductor wire.

Various schemes have been devised to provide the required biasing force to maintain engagement between the sliding members. Generally, a degree of resiliency must be provided to allow for slight deviations of contact wire profile and still maintain mutual contact. However, it is found that a relatively small biasing force between the collector and the contact wire is insufficient to maintain the desired contact. Conversely, a relatively small degree of resiliency force is not entirely satisfactory since it does not allow for slight changes in the pantographs postion in response to the small irregularities of the contact wire.

It is therefore an object of this invention to provide a pantograph assembly which is effective in use with high speed vehicles.

Another object of this invention is the provision for maintaining engagement of a high speed pantograph shoe with a wayside contact wire whose construction and profile have variable characteristics.

Yet another object of this invention is the provision for biasing a collector element against a contact wire to prevent momentary separation due to the deviation of force therebetween.

Still another object of this invention is the provision for minimizing the adverse affects of aerodynamic lift of a pantograph as they tend to lift the associated slider shoes toward the engaged contact wire.

A further object of this invention is the provision for a pantograph assembly which is simple to fabricate, economical to operate and extremely functional in use.

These objects and other features and advantages will become more readily apparent upon reference to the following description when taken in conjunction with the appended drawings.

SUMMARY OF THE INVENTION Briefly, in accordance with one aspect of the invention a plurality of short flat wearing strips are supported by a shoe base with elastic mediums placed therebe-' tween to bias the wearing strips towards the contact wire with which they are engaged. For each strip the elastic medium is compressed through a relatively large displacement and then clamped against stops to prevent the loss of this displacement but allowing it to be free to displace further. The displacement and spring gradient of the elastic medium is chosen such that the force at zero displacement due to clamping the preloaded elastic medium is set to equal the push-up force plus the aerodynamic lift for a relatively slow speed, whereas the average supporting force, as seen by onehalf the total possible displacement from the clamped position is set to equal the push-up force plus the aerodynamic lift at the highest desired speed of the pantograph. The result is that a relatively high force is provided to support the force from the contact wire and yet a low spring constant is provided within the working range so that the strip is responsive to small changes in this force.

In the drawings as hereinafter described, a preferred embodiment and modifed embodiments are depicted; however, various other modifications and alternate constructions can be made thereto without departing from the true spirit and scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front view of the pantograph assembly and associated contact wire as contemplated in the present invention.

FIG. 2 is a top view thereof showing the wear strip segments.

FIG. 3 is a partial sectional view as seen along line 33 of FIG. 2.

FIGS. 4 and 4A illustrate a modified embodiment thereof.

FIG. 5 is a graphic illustration of the force variation of the elastic medium as a function of displacement from a clamped position.

FIG. 6 is a partial front elevational view of a modified embodiment of the subject invention using torsional springs.

FIG. 7 is a top view thereof.

FIG. 8 is a sectional view thereof as seen along line 8-8 of FIG. 7. 7

FIG. 9 is a graphic illustration of the force variation of the elastic medium in the embodiment shown in FIG. 4 as a function of displacement from a clamped position.

FIG. 10 is a front elevational view of a third embodiment of the invention utilizing tension springs.

FIG. I l is a graphic representation of the force analysis of a linkage approximating that in FIG. 10.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIGS. 1 and 2, a pantograph 10 of the present invention is shown in combination with a continuous contact wire or contact wire 11 charged with a voltage from a wayside power source (not shown) and extending along the longitudinal direction of travel. The contact wire may be one of any of the wayside power delivery types; however, that which will be referred to for purposes of this description and which is particularly suited to use with the present invention is that of the overhead catenary type, wherein the profile with respect to a horizontal plane is necessarily non-uniform and further wherein vertical irregu- Iarities exist along the length thereof and tend to cause intermittent separation from frictional engagement with contact portions of the pantograph 10.

The pantograph 10 is of the type normally mounted to the superstructure of a transit car or locomotive (not shown), and comprises a frame 12 extending transversely across the top portion of the car and held up by a constant push-up force mechanism in its base (not shown). Connected to opposite ends 13 and 14 of the frame 12 are

spring plunger assemblies

16 and 17 respectively having their plungers l8 and 19 extending upwardly to resiliently support a shoe base 21 with respect to the upper frame 12. Increased downward dynamic force resulting from contact with the contact wire 11 as the vehicle moves will cause the

plungers

18 and 19 to depress and lower the base 21 with respect to the frame ends 13 and 14. When the vehicle is at rest, the force between the contact wire 11 and the pantograph wear strips 22 is then constant and is commonly referred to as the pantograph push-up force.

Secured to the upper side of the shoe base 21, on a substantially horizontal plane, is a plurality of resiliently supported wear strip segments 22 electrically connected to the vehicle propulsion system and insulated from the car superstructure which indirectly supports them. The strips are adapted to maintain frictional contact with the contact wire 11 as the vehicle travels along the wire in a longitudinal direction. The number of segments 22 is not critical to this invention nor is the geometric arrangement thereof, that shown being a typical arrangement having a pair centrally located with respect to the base 21 and a pair transversely spaced on each side thereof. Each pair is longitudinally spaced to provide a broad base with which the contact wire 11 can maintain frictional engagement as the contact wire moves transversely across the shoe. As seen in FIG. 1 the segments 22 are straight along their lengths except those portions proximate their ends which are curved downwardly to prevent fouling of the contact wire 11 as it moves transversely from one deflected pair to another undeflected pair. The ends of adjacent pairs also overlap at the curved portions to further facilitate a smooth transverse movement of the wire relative thereto. In the embodiment illustrated the wire 11 will generally be in contact with the centrally disposed pair of segments. However, during periods in which the pantograph and wire move relatively transversely, as for example when the car leans in rounding a curve, the wire may slide transversely to the point where it contacts a side pair of segments. Outside of these segments on each end of the shoe base 21 is an end horn 23, having its inner end at substantially the same level as the outer end of its adjacent segments, and having its outer end curve gradually downward. The purpose of the end horns is to allow the conductor wire 11 to slide to the outer sides of the pantograph shoe during occasional periods of operation, as for example, in a yard, and subsequently return smoothly to the central portion of the shoe.

The wear strip segments 22 are each secured to the shoe base 21 by linkage means 24 at each end thereof. The construction of linkage means 23 is best understood by reference to FIG. 3 which shows the wear strip segment 22 mounted to the shoe base 21 by the interconnecting rod 26 and compression spring 27. The rod 26 is secured at its one end to the segment 22 by suitable means, such as by a pin 28 passing through the rod and secured at its ends to a clevis 29 attached to and extending downwardly from the segment 22. The pin is preferably rotatably mounted with respect to either the base or the rod so as to allow the rod to pivot with respect to the segment.

The other end of the rod 26 extends through an aperture 31 in the shoe base 21 and has attached thereto a stop collar 32 secured in a conventional manner by a retaining pin 33. The stop collar 32 is adapted to be biased upwardly against a base stop 34 which forms that portion of the base surrounding the aperture 31. A rebound spring 36 is preferably inserted between the base stop 34 and the stop collar 32 to reduce shock and chatter when the two elements are intermittently brought together. Also preferred is a guide bushing 37 interfacing the walls of the aperture 31 and the rod 26. The elements of the linkage means 24 are assembled in a manner such that the compression spring 27 is precompressed in accordance with a predetermined range of force as will be more fully explained hereinafter.

A modified embodiment of the linkage means is shown at 24 in FIGS. 4 and 4A. At the upper end of the rod 26 is a normally extending pivot 38 rotatably mounted in a pivot strap 39 secured to the underside of the segment 22. Abutting the underside of the segment 22 is the top end of a guide tube 41 extending downwardly around the rod 26 and through the aperture 31. The lower end of the guide tube 41 abuts a stop washer 42 which in turn abuts the stop collar 32. In place of the rebound spring of FIG. 3 a rebound ring 43 of an elastomeric material such as rubber or plastic may be inserted between the base stop 34 and the stop washer 42.

Returning now to a discussion of the compression spring 27, it should be pointed out that any form of an elastic medium may be used for biasing the wear strip segment away from the base 21. However, an important aspect of this invention is that in the assembly of the linkage means 24 of FIGS. 3 and 4, the elastic medium, or spring in the embodiment shown, is compressed through a relatively large displacement and then clamped by means such as with the stop collar 32, to prevent the loss of this displacement while allowing freedom for further displacement. FIG. 5 illustrates the spring force variation as a factor of relative displacement of segment and base from the clamped position. It will be seen that in the clamped position, or at X 0, the force of the spring, which is available for counteraction against downward force of the conductor wire, is relatively high, while that force which exists on the spring at the point of maximum displacement is not significantly greater. Stated in another way, the range of force variation" is small as compared with the clamping force. The spring constant, which is represented by the slope of the curve P, is then relatively low, thereby allowing the spring to be responsive to small changes in force from the conductor wire. On the other hand, the average supporting force which the spring will resist is relatively high.

The force from the wire which must be supported by the elastic medium if the shoe is to remain soft is that of the constant push-up force of the pantograph frame plus the aerodynamic lift on the complete pantograph plus dynamic forces due to varying wire profile. A typical design of the subject invention would be such that the force at zero displacement due to clamping would be equal to the push-up force plus the aerodynamic lift for a specified lower speed, as for example, 90 mph. Similarly the Average Supporting Force as indicated in FIG. 5 could be set to equal the push-up force plus the estimated aerodynamic lift at the highest expected speed of the pantograph.

As an example, assume a typical pantograph with a push-up force of 28 lbs and an estimated aerodynamic lift of 16 lbs at 90 mph and 50 lbs at 160 mph. Assume further that spring gradient of 60 lb/in is desirable for adequate response. Then the preload force at 90 mph would be 28 16 =44 lb and the spring would be compressed 44/60 0.73 in. before it is clamped. The Average Supporting Force at 160 mph would be 28 50 78 lbs and the full compression would be 78/60 1.30 in. Half the Range of Working Displacement would be 1.30 0.73 =0.57 in., or the full range would be 1.14 inches.

As mentioned hereinbefore, the wire 11 will be in contact principally with the central portion of the pantograph and specifically with the centrally disposed wear strip segments. Accordingly, the linkage means 24 of FIGs. 3 and 4 need only be installed in the centrally located segments, and at the inner ends of the outside segments. The outer ends of the outside segments are preferably only pivoted and not resiliently fastened to the base, thereby preventing their moving downwardly when the wire moves to that area. If the ends were resiliently supported, like 24, the wire would tend to be below the top surface of the end of the horn element 23 and could become fouled even though that portion of the horn 23 is curved downwardly similarly to the segment ends as described heretofore. Although the outer segments have no elastic medium support adjacent to the horns, they should be pivotably mounted in a manner similar to that of using a rotatable pin 28 in FIG. 3 so as to allow the segments to tip in their length direction while holding their alignment with the wire 1 1 in their width direction.

A modified embodiment of the present invention is illustrated in FIGS. 6, 7 and 8 wherein the end horn 44 becomes a base element on which the wear strip segments 46 are resiliently supported. The pantograph frame 12 and plunger assembly 16 is essentially identical to that of the preferred embodiment. Pivotally secured to the plunger 18 is a shackle 47 interconnecting to a bail 48 extending downwardly and substantially 'normal to the end horn 44. The placement of the shackle is such that when the end horn 44 is rotated as a result of the shoe being deflected downwardly, the distance between supports as defined by the pivot pins 49 on the one end thereof and their symmetrical equivalents on the other end thereof, is increased proportionately to allow the proper freedom of movement in the downward direction.

(Connected to the upper end of the end horn 44 by a pivotal shaft 51 is one end of a center link 52 extending transversely in a substantially horizontal plane, across the path of motion to similarly connect to the opposite end horn. The center link 52 comprises a pair of spaced body members 53 and 54 interconnected by cross ties 56. Secured to the upper surfaces of body members 53 and 54, as well as to the upper surfaces of the oppositely disposed end horns are the wear strip segments 46 which frictionally engage the contact wire 11. As can be seen from FIG. 6, the interconnecting ends of the horn and center link are curved downwardly and are overlapped to prevent hooking the wire if it tends to slide outwardly onto the end born 44.

As previously stated the horn 44 and center link 52 are pivotable about the shaft 51. Torsion springs 57 are installed at that shaft so as to bias the center link upwardly, or in a clockwise direction with respect to the shaft 51. The extent to which the relative rotation occurs is limited by mutual impingement of opposing

stops

58 and 59 located on downwward protruding portions of the end horn 44 and center link 52, respectively. The stops 58 and 59, which are preferably of the elastomeric type, allow the torsion springs 57 to be preloaded in a manner similar to that described in the preferred embodiment and tend to preserve the flat arch shape in the preloaded position. In FIG. 9 is graphically illustrated the estimated spring force variation as a factor of vertical displacement of the center link from the preloaded position. Design parameters may be arrived at by consideration of those factors and in a manner similar to that set forth in the discussion of the preferred embodiment.

Another alternative embodiment of the invention is shown in FIG. 10 wherein the torsion springs of the FIG. 6 embodiment are eliminated'and instead tension springs 61 and 62 are installed between the respective bails 63 and 64 and

arms

65 and 66. The tension springs 61 and 62 are preloaded against the elastic stops in a manner similar to that previously described. The shoe is then in an arched position, and as the downward force is applied and increased to exceed the preload, the shoe deflects with a relatively soft spring constant. The static equations for a linkage geometry that approximates the linkage of FIG. 10 can be solved and the results represented in dimensionless form as shown in FIG. 11.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. A current collecting pantograph assembly for the transfer of electrical power from a continuous overhead conductor to an electrical vehicle for propulsion in the longitudinal direction comprising:

a. a pantograph frame secured to the vehicle;

b. a shoe base secured to said pantograph frame by resllient means, said base having a first stop element attached thereto;

c. at least one wearing strip having a substantially flat top surface for maintaining frictional contact with the overhead conductor as said wearing strip moves in the longitudinal direction of travel;

d. linkage means interconnecting said shoe base and said wearing strip, said linkage means having a second stop element for direct impingement against said first stop element; and

e. an elastic medium disposed between said shoe base and said wearing strip for biasing said wearing strip toward the overhead conducter, said elastic medium being substantially precompressed to a first position wherein said first and second stop elements are in direct impingement so as to limit the upward movement of said wearing strip with respect to said shoe base, the force of said elastic medium when compressed to said first position being substantially equal to the constant push-up force of the pantograph plus the aerodynamic lift force resulting from movement of the vehicle at a predetermined speed, and being further compressible to a second position when a downward force is imposed on said wearing strip so as to provide a relatively high average force against said wearing strip while retaining a relatively low spring constant between said first and second positions.

2. A pantograph assembly as set forth in claim 1 wherein the force of said elastic medium when compressed to said first position is substantially equal to a constant push-up force of the pantograph plus the aero dynamic lift force resulting from movement of the vehicle at a predetermined low speed.

3. A pantograph assembly as set forth in claim 1 wherein the average supporting force as defined by that force of the elastic medium when compressed to a point halfway between said first and second positions is equal to the push-up force plus the aerodynamic lift at a predetermined highest expected speed of the pantograph.

4. A pantograph assembly as set forth in claim 1 wherein said wear strip is elongate in form as aligned transversely with respect to the longitudinal direction of travel, and further wherein said contact wire is free to slide across its length while maintaining constant frictional engagement therewith.

5. A pantograph assembly as set forth in claim 4 and including an end horn connected to said shoe base at each end of said wear strip, the ends of both the wear strip and the end horns respectively overlapping in a direction transverse to the direction of travel and being turned downwardly to allow said conductor wire to slide smoothly thereover as it slides in a transverse direction.

6. A pantograph assembly as set forth in claim 4 and including means for restraining said wearing strip from tipping along its width but allowing pivotal movement, about its ends to permit tipping along its length.

7. A pantograph assembly as set forth in claim 1 and including a plurality of elongate wearing strips extending transversely across said base in a continuous single plane, the ends of adjacent strips being spaced longitudinally turned downwardly, and mutually overlapping in the transverse direction to allow said conductor wire to slide smoothly thereover as it slides in the transverse direction.

8. A pantograph assembly as set forth in claim 7 and including an end horn connected to each end of said base so as to overlap at least one of said wear strips the overlapping portions of both the end horn and its adjacent wear strip being turned downwardly to allow said conductor wire to slide smoothly thereover as it slides in the transverse direction.

9. A pantograph assembly as set forth in claim 8 wherein the portions of those wear strips overlapping said end horns are restricted from reciprocal movement with respect to said base but are permitted to rotate relative thereto to allow the opposite end of said wear strip to so reciprocate.

10. A pantograph assembly as set forth in claim 1 wherein said linkage means comprises:

a. an elongate rod pivotably secured at its upper end to said wear strip and depending therefrom to slidably extend through an aperture in said base; and

b. a collar attached to the lower end of said rod to restrict its upward movement to said first position.

11. A pantograph assembly as set forth in claim 10 and including a cylindrical guide tube concentrically disposed with respect to said rod between said wear strip and said collar and wherein said elastic medium comprises a helical spring concentrically disposed on the outer side of said cylindrical guide, between said wear strip and said shoe base.

12. A pantograph assembly as set forth in claim 1 wherein said shoe base comprises a pair of spaced outer members aligned in the transverse plane, said outer members being pivotably secured at their inner ends to opposite ends of said wear strip and pivotably secured at distal points thereon to said pantograph frame, and wherein said elastic medium tends to cause said members to rotate with respect to said wear strip so as to bias said wear strip upwardly.

13. A pantograph assembly as set forth in claim 12 wherein said elastic medium comprises a torsion spring disposed at the inner ends of each of said outer members and interacts with the wear strip and the respective outer member.

14. A pantograph assembly as set forth in claim 12 wherein said wear strip includes an arm extending downwardly from each end thereof and further wherein said elastic medium comprises a tension spring interconnecting each of said arms with its adjacent outer member at a point removed from its inner end.

15. A current collecting pantograph assembly for the transfer of electrical power from a continuous overhead conductor to an electrical vehicle for propulsion in the longitudinal direction comprising:

a. a pantograph frame secured to the vehicle;

b. a shoe base secured to said pantograph by resilient means;

at least one elongate wearing strip aligned transversely with respect to the longitudinal direction of travel and having a substantially flat top surface for maintaining frictional contact with the overhead conductor as said wearing strip moves in the longitudinal direction of travel, with the contact wire being free to slide across the length of said wearing strip while maintaining constant frictional engagement therewith;

d. an end horn connected to said shoe base at each end of said wear strip, the ends of both the wear strip and the end horns respectively overlapping in a direction transverse to the direction of travel and being turned downwardly to allow said conductor wire to slide smoothly thereover as it slides in a transverse direction, and

e. linkage means interconnecting said shoe base and said wearing strip.

16. A current collecting pantograph assembly for the transfer of electrical power from a continuous overhead conductor to an electrical vehicle for propulsion in the longitudinal direction comprising:

a. a pantograph frame secured to the vehicle;

b. a shoe base secured to said pantograph frame by a resilient means and c. a plurality of elongate wearing strips extending transversely across said base in a continuous single plane, the ends of adjacent strips being spaced longitudinally turned downwardly, and mutually overlapping in the transverse direction to allow said conductor wire to slide smoothly thereover as it slides in the transverse direction, and

d. linkage means interconnecting said shoe base and said wearing strip.

17. A current collecting pantograph assembly as set forth in claim 16 and including an end horn connected to each end of said base so as to overlap at least one of said wear strips the overlapping portions of both the end horn and its adjacent wear strip being turned downwardly to allow said conductor wire to slide smoothly thereover as it slides in the transverse direction.

18. A current collecting pantograph assembly as set forth in claim 17 wherein the portions of those wear strips overlapping said end horns are restricted from reciprocal movement with respect to said base but are permitted to rotate relative thereto to allow the opposite end of said wear strip to so reciprocate.

19. A current collecting pantograph assembly for the transfer of electrical power from a continuous overhead conductor to an electrical vehicle for propulsion in the longitudinal direction comprising:

a. a pantograph frame secured to the vehicle;

b. at least one wearing strip having a substantially flat top surface for maintaining frictional contact with the overhead conductor as said wearing strip moves in the longitudinal direction of travel;

c. a shoe base secured to said pantograph frame by resilient means, said shoe base comprising a pair of spaced outer members aligned in the transverse plane and being pivotally secured at their inner ends to opposite ends of said wear strip and pivotably secured at distal points thereon to said pantograph frame;

d. linkage means interconnecting said shoe base and said wearing strip; and

e. an elastic medium disposed between said shoe base and said wearing strip tending to cause said outer members to rotate with respect to said wear strip so as to bias said wear strip toward the overhead conductor.

20. A current collecting pantograph assembly as set forth in claim 19 wherein said elastic medium comprises a torsion spring disposed at the inner ends of each of said outer members and interacts with the wear strip and the respective outer member.

21. A current collecting pantograph as set forth in claim 19 wherein said wear strip includes an arm extending downwardly from each end thereof and further wherein said elastic medium comprises a tension spring interconnecting each of said arms with its adjacent outer member at a point removed from its inner end. =l=

Claims

1. A current collecting pantograph assembly for the transfer of electrical power from a continuous overhead conductor to an electrical vehicle for propulsion in the longitudinal direction comprising: a. a pantograph frame secured to the vehicle; b. a shoe base secured to said pantograph frame by resllient means, said base having a first stop element attached thereto; c. at least one wearing strip having a substantially flat top surface for maintaining frictional contact with the overhead conductor as said wearing strip moves in the longitudinal direction of travel; d. linkage means interconnecting said shoe base and said wearing strip, said linkage means having a second stop element for direct impingement against said first stop element; and e. an elastic medium disposed between said shoe base and said wearing strip for biasing said wearing strip toward the overhead conducter, said elastic medium being substantially precompressed to a first position wherein said first and second stop elements are in direct impingement so as to limit the upward movement of said wearing strip with respect to said shoe base, the force of said elastic medium when compressed to said first position being substantially equal to the constant pushup force of the pantograph plus the aerodynamic lift force resulting from movement of the vehicle at a predetermined speed, and being further compressible to a second position when a downward force is imposed on said wearing strip so as to provide a relatively high average force against said wearing strip while retaining a relatively low spring constant between said first and second positions.

2. A pantograph assembly as set forth in claim 1 wherein the force of said elastic medium when compressed to said first position is substantially equal to a constant push-up force of the pantograph plus the aerodynamic lift force resulting from movement of the vehicle at a predetermined low speed.

10. A pantograph assembly as set forth in claim 1 wherein said linkage means comprises: a. an elongate rod pivotably secured at its upper end to said wear strip and depending therefrom to slidably extend through an aperture in said base; and b. a collar attached to the lower end of said rod to restrict its upward movement to said first position.

15. A current collecting pantograph assembly for the transfer of electrical power from a continuous overhead conductor to an electrical vehicle for propulsion in the longitudinal direction comprising: a. a pantograph frame secured to the vehicle; b. a shoe base secured to said pantograph by resilient means; c. at least one elongate wearing strip aligned transversely with respect to the longitudinal direction of travel and having a substantially flat top surface for maintaining frictional contact with the overhead conductor as said wearing strip moves in the longitudinal direction of travel, with the contact wire being free to slide across the length of said wearing strip while maintaining constant frictional engagement therewith; d. an end horn connected to said shoe base at each end of said wear strip, the ends of both the wear strip and the end horns respectively overlapping in a direction transverse to the direction of travel and being turned downwardly to allow said conductor wire to slide smoothly thereover as it slides in a transverse direction, and e. linkage means interconnecting said shoe base and said wearing strip.

16. A current collecting pantograph assembly for the transfer of electrical power from a continuous overhead conductor to an electrical vehicle for propulsion in the longitudinal direction comprising: a. a pantograph frame secured to the vehicle; b. a shoe base secured to said pantograph frame by a resilient means and c. a plurality of elongate wearing strips extending transversely across said base in a continuous single plane, the ends of adjacent strips being spaced longitudinally turned downwardly, and mutually overlapping in the transverse direction to allow said conductor wire to slide smoothly thereover as it slides in the transverse direction, and d. linkage means interconnecting said shoe base and said wearing strip.

19. A current collecting pantograph assembly for the transfer of electrical power from a continuous overhead conductor to an electrical vehicle for propulsion in the longitudinal direction comprising: a. a pantograph frame secured to the vehicle; b. at least one wearing strip having a substantially flat top surface for maintaining frictional contact with the overhead conductor as said wearing strip moves in the longitudinal direction of travel; c. a shoe base secured to said pantograph frame by resilient means, said shoe base comprising a pair of spaced outer members aligned in the transverse plane and being pivotally secured at their inner ends to opposite ends of said wear strip and pivotably secured at distal points thereon to said pantograph frame; d. linkage means interconnecting said shoe base and said wearing strip; and e. an elastic medium disposed between said shoe base and said wearing strip tending to cause said outer members to rotate with respect to said wear strip so as to bias said wear strip toward the overhead conductor.

21. A current collecting pantograph as set forth in claim 19 wherein said wear strip includes an arm extending downwardly from each end thereof and further wherein said elastic medium comprises a tension spring interconnecting each of said arms with its adjacent outer member at a point removed from its inner end.