US3823278A

US3823278A - Aerodynamically adjustable pantograph

Info

Publication number: US3823278A
Application number: US00318182A
Authority: US
Inventors: R Gray
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1972-12-26
Filing date: 1972-12-26
Publication date: 1974-07-09
Anticipated expiration: 1991-07-09
Also published as: FR2211363A1; DE2363683A1; FR2211363B3

Abstract

Apparatus for maintaining a substantially constant force between a pantograph collector shoe and an overhead contact wire by aerodynamically moving the shoe to follow the vertical profile of the contact wire. The position of the contact wire is detected with respect to the collector shoe or its supporting frame and an airfoil attached to the pantograph is adjusted in response thereto to provide the requisite amount of positive or negative aerodynamic lift for the shoe to adjust its vertical position in correspondence with that of the overhead contact wire.

Description

United States Patent 1191 Gray 7 1111' 3,823,278 1451 July 9, 1974 AERODYNAMICALLY ADJUSTABLE PANTOGRAPH [75] Inventor: Richard T. Gray, Erie, Pa.

[73] Assignee: General Electric Company, Erie, Pa. [22] Filed: Dec. 26, 1972 [21] Appl. No.: 318,182

[52] U.S. Cl 191/66, 191/45, 191/65 [51] Int. Cl B601 5/12 [58] Field of Search 191/45, 47, 48, 49, 50,

[56] References Cited UNITED STATES PATENTS 2,996,267 8/1961 Warren 244/75 A 3,238,314 3/1966 Faivelbyf. 191/66 FOREIGN PATENTS OR APPLICATIONS 1,074,622 2/1960 Germany 191/66 Primary Examiner-M. Henson Wood, Jr.

Assistant Examiner-D. W. Keen Attorney, Agent, or FirmWalter G. Bemkopf; Dana F.Bigelow [57] ABSTRACT Apparatus for maintaining a substantially constant force between a pantograph collector shoe and an overhead contact wire by aerodynamically moving the shoe to follow the vertical profile of the contact wire. The position of the contact wire is detected with respect to the collector shoe or its supporting frame and an airfoil attached to the pantograph is adjusted in responsethereto to provide the requisite amount of positive or negative aerodynamic lift for the shoe to adjust its vertical position in correspondence with that of the overhead contact wire.

f 12 Claims, 14 Drawing Figures PATENTEDJUL 91w 3.823.278

SKEU 1 BF 6 PR/OR ART PATENTED 91914 3.823.278 SHEET 2 F 6 m mi 2. M a

PATENIEuJuL 9mm 3,823,278

SHEET 3 OF 6 FIG. 6 32 Pmimmm slam sum 6 or 6 AERODYNAMICALLY ADJUSTABLE PANTOGRAPH This invention relates generally to pantograph structures and more particularly to mechanisms for adjusting the vertical position thereof to accommodate a contact wire having a variable vertical profile.

Conventional pantographs of the type used for the high speed pickup of power from an overhead cantenary comprise at least two elastic suspensions; the springs which balance the weight of the frame, and the springs which suspend resiliently the comparatively low inertia power pickup element on the collector shoe. The frame, which is necessarily of considerable weight, moves vertically in response to high amplitude and low frequency variations in the height of the contact wire with respect to the vehicle. Poor response is thus obtained from pressure variations between the shoe and the contact wire. These pressure variations may be brought about by variation in the height of the contact wire above the truck, variation in the nature of the supporting system for the contact wire, and variation in loading on the current collector brought about, for example, by variation of the wind pressure as the speed of the'vehicle changes or by icing.

The collector shoe which is adapted to maintain frictional contact with the overhead wire is made as light as possible so that it can readily move in response to small amplitude high frequency variations in the height of the contactor wire with relation to the vehicle. However, since the collector shoe supporting springs have a limited elastic range, their effect is removed from the mechanism during periods in which greater variations exist.

In combination, the stiff support offered by the frame springs, and the soft support given by the shoe springs provide an upward force, commonly called the push up force which presumably maintains a uniform force between the-shoe and the overhead wire. However, because of the degree of variations and the nature of the supporting springs the response is inadequate to provide such a uniform force.

In recognition of the problem, various devices have been. fabricated in which supplementary apparatus is utilized to vary the height of the shoe or the frame in response to the pressure variationsmentioned herein above. The pressure variations are measured either directly, such as by piezoelectric methods, or indirectly by measurement of displacement values. Translation of the measurements is then applied to some form of elevating device to raise or lower the collector shoe in response thereto. The elevating device is conventionally powered by servocontrolled devices of thepneumatic, hydraulic or'electrical type. Provision of this auxiliary power is costly and difficult to obtain. For example, in

frameor to the contactor shoe. Aerodynamic lift is thus provided thereto as the pantograph travels along the rail. This lift, however, varies only in relation to vehicle speed and does not accommodate the aforementioned pressure variations. Further, the apparatus does not selectively provide for either positive or negative lift nor, in some cases, for operation in either direction of vehicle travel.

It is therefore an object of this invention to provide an improved apparatus for controlling the vertical motion of a pantograph in relation to the force between the collector shoe and the overhead wire.

Another object of this invention is the provision for controlling the vertical position of a pantograph without the use of an external power source.

Yet another object of this invention is the provision for a controlled pantograph which operates equally well in either direction of vehicle travel.

Still another object of this invention is the provision in a controlled pantograph without an external power source, for moving the pantograph down when the shoe/wire interface force increases and up when that force decreases.

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

SUMMARYOF THE INVENTION Briefly, in accordance with one aspect of the invention an airfoil element is attached to either the collector shoe or the pantograph frame to provide aerodynamic lift thereto in relation to the speed at which the vehicle and mounted pantograph are traveling along an hydraulic control system a fluid at high pressure must be constantly delivered to the pantograph frame. Besides the requirement for considerable horsepower to deliver the fluid, additional problems are encountered since the pantograph frame is charged to the same high electrical potential'as the overhead contact wire. Clearly it is desirable to have a supplementary system to control the pantograph height, but the power requirement may not justify the advantages gained by use thereof.

Various types of elevating means have been devised wherein wind vanes are secured to the pantograph the contact wire. A feedback device adjusts the attitude of the airfoil in response to the interactive force between the collector shoe and the overhead contact wire so as to provide to the shoe an appropriate aerodynamic lift over a range of positive and negative values to maintain a substantially constant contacting force with the contact wire. The apparatus which raises and lowers thepantograph is powered entirely by the air currentsinteracting with the pantograph and associated airfoil, and provision is made for its effective usage regardless of the direction in which the vehicle is traveling.

BRIEF DESCRIPTION OF THE DRAWINGS collector shoe.

FIG. 3 is a sectional view of the collector shoe and airfoil portions of the preferred embodiment.

FIGS. 4, 5 and 6 are sectional views of modified embodiments of the airfoil portion thereof.

FIG. 7 is a modified embodiment of the invention.

FIGS. 8 and 9 show another embodiment of the invention as applied to the pantograph frame.

FIGS. 10 and 11 illustrate a type of sensing and adjusting means utilized with the structure of FIGS. 8 and 9.

FIG. 12 is a modified embodiment thereof.

FIG. 13 illustrates another type of sensing and adjusting means utilized with the structure of FIGS. 8 and 9.

DESCRIPTION OF THE PREFERRED EMBODIMENT Reference is now made to FIG. 1 wherein a portion of an electrical propulsion vehicle 11 has mounted thereon, through insulators 12, a pantograph 13 of the conventional type. The pantograph 13 comprises a base 14; a frame having lower arms 16 pivotably attached thereto, and upper arms 17 connected at their upper ends by a joint 18; and a collector element 19 extending upwardly from the joint 18 to contact an overhead wire (not shown). A pair of tension springs 21 are attached, one to each of the frame lower arms 16, to bias them inwardly towards each other so as to cause the joint 18 and the attached collector shoe 19 to be biased upwardly. Crank arms rigidly attached to the respective lower ends of the lower arms 16 and connected by a common link tend to maintain the diamond configuration.

The collector element 19 is typically mounted at the joint 18 by a shaft 22 slidably disposed in a cylindrical casing 23 and biased upwardly therein by a compression spring 24. A casing stem 26 having the ends of pivotal links 27 slidably attached thereto maintains the casing 23 and associated shaft 22 in a constant vertical position.

The combination of the two tension springs 21 biasing the frame upwardly and the compression spring 24 urging the collector element 19 upwardly with respect tothe frame, is designed to push against the contact wire with a substantially constant force commonly referred to as the push-up-force. However, for reasons discussed hereinbefore, the reaction of the springs alone is inadequate to provide a uniform contact force between the collector element 19 and an overhead wire having a variable disposition.

Referring now to FIG. 2, one concept of the improved pantograph is illustrated. A portion of the collector element '19 is shown with a pair of

collector shoes

28 and 29 having

wear strips

31 and 32, respectively, forfrictional contact with the overhead wire 33. Extending oppositely from the

shoes

28 and 29 along the line of travel are

airfoil elements

34 and 36 respectively, whose structure and function will be more fully described hereinafter.

Also attached to the

shoes

28 and 29, and extending oppositely along the line of travel, are support

arms

37 and 38, respectively. The rigid combinationof collector element 19, the symmetrically disposed

collector shoes

28 and 29, and the

arms

37 and 38, provide a balanced structure which is free to move vertically as heretofore explained. The

support arms

37 and 38 have for their purpose the supporting of

sensing mechanisms

39 and 41.

It should be noted that various types of sensing mechanisms may be utilized as, for example, photo-electric means or electro-magnetic means. The function, however, is the same in any case; the detection of height variation in the contact wire 33 at a point forward of the collector shoes in the direction of vehicle travel.

The illustrated

mechanical sensing mechanisms

39 and 41 are identical and are designed for use, one at a time, in either direction of vehicle travel, with the leading mechanism in operation and the trailing one in an ineffective condition. The following description of the mechanism 41 can be applied as well to the mechanism 39 as to that mechanism 41. It comprises a sensor arm 42 having attached at its one end a'sensor 43 for maintaining frictional contact with the overhead wire 33, and a link i 44, pivotally interconnecting the support arm 38 and the sensor arm 42. A signal arm 46, also interconnecting the support arm and the sensor arm, provides for a fourbar linkage so as to maintain the sensor arm 42 in a vertical disposition and ensure that the sensor 43 does not rotate. A linkage spring 47 is provided to support the dead weight of the sensor 43 and keep it against the wire when the vehicle is at rest or moving slowly. The sensor 43 preferably includes a thin wear strip 48 attached to the top of a wedge which acts like an airfoil to hold the wear strip up against the overhead wire.

The signal arm 46, which is pivotable on the support arm 38, is linked at its rearward end 49 to a rocker arm 51 rotatably mounted to the contactor shoe 29. Rotation of the rocker arm 51 on its axis 52 transmits motion to an actuator lever 53 which in turn brings about the shoe configuration causes a change in its aerody- I namic character and results in a positive or negative lift thereto, to move the wear strip 32 toward or away from the overhead wire 33. The opposite rocker arm 55 operates simultaneously with the rocker arm 51 to similarly adjust its associated airfoil element 34. However, in this design, only the airfoil element of the leading collector shoe will be aerodynamically effective.

Operation of the apparatus is as follows when the vehicle is moving from left to right. If the contact wire ahead of the moving shoe 29 is lower than the shoe, excessive force will build up between the shoe and the wire absent the apparatus. But with the subject apparatus, the sensor 43 is pushed down rotating the signal arm 46 and in turn the rocker arm 51, clockwise. This causes the airfoil element 36 to be further extended from the shoe29 and the aerodynamic force to push down on the shoe, thus reducing the excessive force between the shoe and the overhead wire. Conversely, if the wire ahead of the moving shoe is higher than at the shoe, the linkage spring 47 and the aerodynamic lift on the sensor picks it up, rotating the signal arm and rocker arm clockwise. The airfoil element 36 is retracted and a second airfoil element (not shown), lo 'cated at apoint on the upper portion of the shoe, is extended so as to change the aerodynamic lift to a positive value. As a result the shoe is pushed up so that it can follow the rising overhead wire and maintain contact'therewith. The trailing sensing device 39 just follows along in an inoperative condition since its airfoil elements are out of the air stream and thus rendered ineffective. However, when the vehicle is reversed, the sensing mechanism 39 then leads and becomes operative in a manner just described and the mechanism 41 becomes the inoperative trailing mechanism. The apparatus thus works equally well in either direction of travel.

In the arrangement shown at FIG. 2, it is possible that there will be insufficient force available at the rocker arm to move the actuator levers under each shoe element, or, if there is sufficient force, the interface force between the sensor and the overhead wire will be so high as to cause excessive wear of the wear strip 48 and to lift the wire ahead of the shoe. This would present an undesirable false signal back to the main shoe. Thus, it may be necessary to give the sensor more leverage by increasing the length a and reducing the length b. Another alternative is to utilize the signal arm 46 to operate an air valve which would control booster air cylinders 50. If the external power boost is necessary, it can be obtained from the vehicle air supply through an insulated tubing arrangement. It would only require a fraction of the power to control aerodynamic lift that it requires to drive the entire pantograph frame directly as is done in the prior art. An alternate arrangement of FIG. 2 would be to attach the

support arms

37 and 38 to the cylindrical casing 23 as in another embodiment of this invention shown by FIG. 14. In FIG. 2 this alternate attachment would require that length a be increased and length b decreased because the sensors 43 would then undergo relatively larger displacements.

Construction of one embodiment of the contactor shoe 29 can be better understood by reference to FIG. 3. A frame 54 has secured thereto by screws 56 the wear strips 32. Also attached to the frame 54 is a casing 57 which is held in place by a plurality of screws such as screw 58. Formed in the casing 58 at one end thereof are upper and lower apertures, 59 and 61 respectively, in which the airfoil elements are slidably disposed and adapted to protrude therefrom. The lower airfoil element 36 is disposed between the lower wall of the casing 57 and a parallel guide tab 62, and has a pair of normally projecting ribs 63 defining a notch in which a crankarm post 64 is fitted. The crank 66 is mounted on a shaft 67 and is caused to rotate by movement of the actuator lever 53 which extends downwardly through a casing slot 68. The opposite crankarm post 69 similarly fits between ribs 71 of an upper airfoil element 72 which is disposed in the aperture 59 and vertically supported by upper and

lower guide tabs

73 and 74, respectively. Movement of the actuator lever brought about by rotation of the rocker arm 51 (FIG. 2) causes rotation of the crank 66 which moves the

airfoil element

36 and 72 in and out of the apertures to change the aerodynamic characteristics of the shoe 29. The po-- Various modified embodiments of the shoe configu-- ration are shown in FIGS. 4, 5 and 6, all of which have for their design purpose the provision for selectively changing the aerodynamic characteristics of the shoe.

The design shown in FIG. 4 is similar to that of FIG. 3

in that it has a lower lip 36 which protrudes by an amount determined by the degree of lift desired. Instead of a crank, a fourbar-linkage arrangement is utilized with

parallel links

76 and 77, pivot posts 78 and 79, and connecting posts 81 and 82.

The design of FIG. 5 utilizes a back surface 83 hinged at the lower edge such that the trailing element has increasing aerodynamic lift as the back is further opened. With such a design the leading element is not affected by the manipulation of its back surface.

In FIG. 6 a design is shown wherein a concave airfoil 86 is exposed in the direction of travel with its attitude being controlled by a four-bar-linkage 87. In the position shown a positive aerodynamic lift would result; however, a rotation of the four-barlinkage in the clock wise direction would bring about a negative aerodynamic lift.

Various other designs and combinations of those designs heretofore described may be utilized to effect a change in shoe configuration as contemplated by this invention.

The embodiment shown in FIG. 2 senses vertical variations in the overhead wire position with respect to the contactor shoe 29. Various other sensing and actuating schemes may be utilized, such as sensing the displacement of the contactor shoes with respect to the pantograph frame as it varies in relation to the force of the overhead wire on the shoe wear strips. One type of mechanism to accommodate this function is shown in FIG. 7. The design is similar to that of FIG. 2 in that a pair of

contactor shoes

28 and 29 are rigidly connected to the collector element 19, and each has a rocker arm 51 to move the actuator lever 53 by rotation of the rocker arm about its axis 52. The collector element 19 of its shaft 22 are, however, sprung from the casing 23 in a manner similar to that shown in FIG. 1. As the force between the overhead wire and the contactor shoes 28 and 29 varies the collector element and shoes will accordingly move vertically with respect to the casing 23 which forms part of the pantograph frame. It is this movement which causes adjustments to be made in the position of the

airfoils

34 and 36 and thereby bring about vertical movement of the shoes to correspond with that of the overhead wire position.

Rigidly secured to the casing 23 is a mounting plate 88 having

pivots

89 and 91 thereon. Rotatably secured to the

pivots

89 and 91 are the ends of

pivot links

92 and 93 whose opposite ends are pivotably linked to

rocker arms

55 and 51, respectively.

In operation, when the leading shoe 29 is pushed downward against the spring suspension of the collector element 19 by an excessive force from the overhead wire, the vertical distance between the shoe and the pantograph frame (the casing 23) is shortened. The link 93 pushes up on the rocker arm 51 rotating it clockwise and actuating the negative lift configuration as shown. A downward aerodynamic force would be applied to the shoe 29 to relieve the high interface force between the overhead wire and the shoe. Conversely, as the force on the shoe decreases below the desired value, the spring suspension pushes upward with respect to the frame, and the positive aerodynamic lift configuration is actuated to raise the shoe forward to the overhead wire. It should be noted that the

airfoil element

34 and 36 are adjusted simultaneously with only the leading element being aerodynamically effective, regardless of the direction of travel.

In the mechanisms thus far described, airfoil elements have been attached directly to the collector shoes to change the vertical position thereof. An alternative arrangement which is shown in FIG. 8 and 9 utilizes an airfoil element 94 secured directly to the pantograph frame casing 23 on an axis 96 transverse to the direction of travel. An airfoil element similar to that shown in FIG. 9 is secured to the other side of the pantograph frame and operates in unison with the airfoil element 94. Together, the two airfoils act to raise or lower the entire pantograph frame in either direction of vehicle travel, with the degree of lift being determined by the attitude of the airfoils with respect to the axis 96. A flap 97 is mounted above (or below) the airfoil 94 for the purpose of meeting the bi-directional travel requirement. For example, if the vehicle is moving from left to right, the air pressure on the flap tends to rotate the entire airfoil 94 counterclockwise and thereby provide a positive angle of attack (upward force). After this initial orientation, the airfoil may be controlled to produce varying degrees of positive and negative lift forces as will be described hereinafter. A light spring 98 is preferably installed to maintain the airfoil in substantially a neutral position when the vehicle is at rest or moving slowly.

Illustrated in FIGS. 10 and 11 is one method of controlling the airfoils 94 by using the relative displacement between the shoe 29 and the frame casing 23. Attached to the bottom of the shoes and depending therefrom are a pair of struts 99 (only one shown) interconnected at their lower ends by a central shaft 101 aligned transverse to the direction of travel. The shaft is supported by bearings 102 at the struts and has on each of its ends a crankarm 103. Attached to the end of each of the crankarms 103 are a pair of

flexible links

104 and 106 such as cords or chains. The opposite ends of 'the flexible links are attached to the airfoil 94 at the connection point 105. The length of the

links

104 and 106 are such that they are almost slack when the shoe is not touching the overhead wire (i.e., when the shoe is at the maximum vertical height with respect'to the frame). When the shoe is held up against the wire with just the static push-up force, the links will then be slack. With little or no motion of the vehicle the crankarms 103 will be in the downward vertical position. The light spring 98 and crankarm counterweights would further assure this.

Also attached to the bottom of the shaft 101 is a central flap 107. This flap is utilized to orient the shaft 101 and crankarms 103 so as to render effective the proper link, 104 or 106, in accordance with the direction of travel. For example, as the vehicle beings to move from left to right in FIG. 10, the shaft 101 is rotated clockwise by the force of the air on the central flap 107. When it reaches the horizontal position shown, the crankarms 103 will impinge on their stops 108 at the left with the link 104 being in a slackened condition and the link 106 being pulled taut by the crankarm 103. As the interface force between the overhead wire and the shoe increases excessively, the shoe with its attached shaft 101 and crankarms 103, is pushed downward against its support springs. The link 106 pulls down on the leading edge of the airfoil 94 to cause the aerodynamic lift thereof to move towards a more negative value. It should be noted that the airfoil flap 97 keeps the link 106 taut, and, due to the position of the crankarm stop 108, .the position of the crankarms 103 are fixed for that direction of travel. The central flap 107 merely positions the crank initially to its correct operating position for the particular direction of vehicle travel.

As the interface force between the overhead wire and the shoe decreases excessively, the shoe is raised up by its support springs, and the crankarms 103 raise with respect to the casing 23, thereby allowing the airfoil 94 to be rotated counterclockwise by the flap 97 or a more positive angle of attack. This causes an upward force on the airfoil 94 to raise the frame casing 23 and the shoes upward toward the wire.

When the train stops the central flap 107 and crankarms 103 return to the vertical position and the link 106 is nearly slack. If the vehicle then moves in the opposite direction (right to left), the shaft is rotated counterclockwise so as to bring the crankarms 103 up against the stops 109 on the right side. The link 106 is thus slackened, and the link 104 is pulled taut to control the airfoil in that direction of travel.

A variation of the embodiment just described is shown in FIG. 12, wherein the airfoil flap 97 is attached below the airfoil and the central flap 107 is attached above the shaft-101. The crankarm stops 108 and 109 are then positioned below the crankarms 103 instead of above them. The crankarms are counterweighted and a light spring is attached to assure that the central flap 107 is vertical when the vehicle is at rest.

In operation, as the vehicle moves from left to right, the central flap 107 rotates the shaft counterclockwise until the crankarms 103 contact the stop 108. The link 106 is pulled taut and becomes the controlling link for that direction of travel in a manner 'similar to that described for the design of FIG. 10.

FIGS. 13 and 14 illustrate a modified embodiment, which combines the sensing mechanism of FIG. 2 with the aerodynamic arrangement of FIG. 8. The sensing mechanism comprises the sensor 43 supported by the sensor arm 42 in the center and by sensor arms 11 1 and 112 (not shown) on the sides. The sensor arm 42 is linked to the support arm 38 as shown in FIG. 14 and the sensor arms 111 and 112 are linked to similar support arms 113 and 114 (not shown), respectively. The

' support arms 1 13 and 114 are mounted directly to their respective pantograph frame casings 23 as shown in FIG. 13 whereas the central support arm 38 is I mounted, as for example by welding, to a carrier shaft 1'16 extending between the opposite casings 23. The carrier shaft 116 does not itself rotate but has a bearing 117 on each end thereof and attached to the upper arms of the pantograph which do rotate.

Also attached to the carrier shaft 116 by a pair of brackets 118 is a shaft 119 having rigidly attached thereto at a central point thereon, a double crankarm 121 with arms extending downwardly and having a middle flap 122 projecting upwardly at equal angles therebetween. The shaft 119 is rotatable in bearings 123 and has secured to each end a double crankarm 124 similar to the crankarm 121 but having no flap. The double crankarm 121 is adapted to be positioned by the wind resistance on the middle flap 122 so as to engage the

appropriate signal arm

46 or 126 as shown in FIG. 14. The crankarms 124, which are rotated in I unison with the crankarm 121, are each adapted to engage, with either of its pegs 127or 128, a lever arm 129 projecting upwardly from its associated airfoil 94.

In operation, when the vehicle is at rest, the middle' flap 122 protrudes upward vertically and the arms of both the double crankarm 121 and the double crankarms 124 hang on either side atequal angles with the horizontal. Neither of the signal arms 46 nor 126 are contacting the crank 121 and the airfoils 124 are held in the neutral (horizontal) position by a light spring. As the vehicle moves from left to right, the force of the arm on the middle flap 122 rotates the shaft 119 and crankarms counterclockwise as shown in FIG. 14. On each side of the pantograph the peg 127 on the crankarm 124 contacts the lever arm 129 of the airfoil 94 and the airfoil flap 97 (FIG. 13) tends to rotate the airfoil counterclockwise so as to maintain a positive angle bias. At the same time, the centrally located crankarm 121 is rotated in unison with crankarm 124 so that its forward arm contacts the signal arm 46. The signal arm 46 then controls its position in response to the vertical position of the overhead wire in a manner similar to that as described in FIG. 2. For example, if the vertical position of the overhead wire starts to go lower than that at the shoe, the sensor 43 is pushed downward, the signal arm rotates clockwise, and the crankarrn 122 is moved counterclockwise. The shaft 119 and attached crankarms 124 are also rotated counterclockwise to change the attitude of the airfoil 94 to a more negative attack angle. The aerodynamic force then pushes down on the airfoils 94 and the frame to relieve the buildup of interface force between the shoe and the overhead wire. Conversely, if the vertical position of the overhead wire at the sensor starts to go higher than at the shoe the sensor 43 raises itself up against the wire and the signal arm 46 is rotated counterclockwise. This allows the airfoils 94 to be rotated counterclockwise by their flaps 97, and the angle of attack to be increased. The aerodynamic force raises the pantograph frame to maintain the proper contact force between the shoe and overhead wire.

As set forth in the description of FIG. 2, this mechanism may not provide sufficient force at the end of the signal arm 46 to activate the airfoils. Accordingly, it may be necessary to have the signal arm operate an air valve which controls vehicle air pressure to a cylinder which in turn activates the airfoils. The middle flap 122 i would then be used to switch the air between two cylin-v ders, depending on the direction of travel.

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

1. An improved pantograph arrangement of the type having a collector shoe resiliently supported on a frame to maintain frictional contact with an overhead wire, wherein the improvement comprises:

a. at least one airfoil element secured to the pantograph and being adjustable to provide aerodynamic lift thereto throughout a range of positive and negative values as the pantograph travels at various speeds along the wire in a given direction;

b. means for sensing the force between the collecting shoe and the overhead wire; and

l c. means for adjusting without supplementary power means said airfoil element in response to said sensing means to move the collecting shoe down when the force from the overhead wire increases and up when that force decreasesso as to maintain a substantially constant force between the collector shoe and the overhead wire.

2. A pantograph arrangement as set forth in claim 1 wherein said sensing means comprises a mechanical linkage between the collecting shoe and the frame and further wherein the displacement of the shoe with respect to the frame is indicative of the pressure between the shoe and the overhead wire.

3. A pantograph arrangement as set forth in claim 1 wherein said at least one airfoil element is secured to said collector shoe and is so constructed as to alter the shoe configuration but not tip the shoe from its longitudinal plane when acted on by said adjusting means.

4. A pantograph arrangement as set forth in claim 3 wherein said at least one airfoil element comprises a rigid member extending from said shoe in the direction 5. A pantograph arrangement as set forth in claim 4 wherein said at least one airfoil element comprises a pair of horizontal spaced lips slidably disposed in said collector shoe with their adjacent ends extendable at one end, one at a time, from said shoe and at their other end connected to said adjusting means, the upper of said lips tending to cause an upward aerodynamic lift on said shoe when it is extended and the lower of said lip tending to cause a downward aerodynamic lift thereon when it is extended.

6. A pantograph arrangement as set forth in claim 1 wherein said sensing means comprises:

a. a support arm secured to and extending from said collector shoe in the direction of vehicle travel,

b. a sensor element adjustably secured to said sup port arm at a point displaced from said collector shoe, and extendingupwardly to impinge on said contactor wire;

c. biasing means for urging said upward end to maintain frictional contact with said contactor wire but allow said sensor element to move with respect to said arm in response to change in the vertical profile of the contactor wire as the pantograph travels therealong, and

d. detecting means responsive to the movement of said sensor element with respect to said support arm to activate said adjusting means.

7. A pantograph arrangement as set forth in claim 1 wherein said at least one airfoil element is secured to said frame and, further, wherein said frame moves up and down with the collecting shoe when said airfoil element is adjusted in response to said sensing means.

8. A pantograph arrangement as set forth in claim 7 wherein said airfoil element comprises a wing symmetrically mounted on an axis transverse to the direction of travel, said wing being pivotable on said axis to selecof travel and secured in such a manner as to have the degree of extension determined. by said adjusting means.

tively provide negative and positive aerodynamic lift in either of two opposite directions of travel.

9. A pantograph arrangement as set forth in claim 8 wherein said wing includes a biasing flap attached to one side thereof and extending substantially normally therefrom, whereby as the pantograph travels in either of said two .opposite directions, said biasing flap tends to pivot said airfoil element or its axis in a direction such that its leading edge is biased towards the side of the airfoil element to which said biasing flap is attached.

10. A pantograph arrangement as set forth in claim 9 wherein said adjusting means includes a control flap pivotally attached to said pantograph on an axis transverse to the direction of travel, said control flap being larger in cross section than said biasing flap and linked to said airfoil element in such a manner as to apply a torque thereto opposing that exerted by said biasing flap.

11. A pantograph arrangement as set forth in claim 7 wherein said sensing means comprises a mechanical linkage between the collecting shoe and the frame and further wherein the displacement of the shoe with respect to the frame is indicative of the pressure between the shoe and the overhead wire.

12. A pantograph arrangement as set forth in claim 7 wherein said sensing means comprises:

a. a support means secured to and extending from the pantograph frame in the direction of vehicle travel;

b. sensor element adjustably secured to said support in response to change in the vertical profile of the arm at a point displaced from said collector shoe contactor wire as the pantograph travels thereand extending upwardly to impinge on said contacalong; and tor wire; (1. detecting means responsive to the movement of c. biasing means for urging said upward end to mainsaid sensor element with respect to support arm to tain frictional contact'with said contactor wire but activate said adjusting means.

allow said sensor to move with respect to said arm

Claims

1. An improved pantograph arrangement of the type having a collector shoe resiliently supported on a frame to maintain frictional contact with an overhead wire, wherein the improvement comprises: a. at least one airfoil element secured to the pantograph and being adjustable to provide aerodynamic lift thereto throughout a range of positive and negative values as the pantograph travels at various speeds along the wire in a given direction; b. means for sensing the force between the collecting shoe and the overhead wire; and c. means for adjusting without supplementary power means said airfoil element in response to said sensing means to move the collecting shoe down when the force from the overhead wire increases and up when that force decreases so as to maintain a substantially constant force between the collector shoe and the overhead wire.

4. A pantograph arrangement as set forth in claim 3 wherein said at least one airfoil element comprises a rigid member extending from said shoe in the direction of travel and secured in such a manner as to have the degree of extension determined by said adjusting means.

5. A pantograph arrAngement as set forth in claim 4 wherein said at least one airfoil element comprises a pair of horizontal spaced lips slidably disposed in said collector shoe with their adjacent ends extendable at one end, one at a time, from said shoe and at their other end connected to said adjusting means, the upper of said lips tending to cause an upward aerodynamic lift on said shoe when it is extended and the lower of said lip tending to cause a downward aerodynamic lift thereon when it is extended.

6. A pantograph arrangement as set forth in claim 1 wherein said sensing means comprises: a. a support arm secured to and extending from said collector shoe in the direction of vehicle travel, b. a sensor element adjustably secured to said support arm at a point displaced from said collector shoe, and extending upwardly to impinge on said contactor wire; c. biasing means for urging said upward end to maintain frictional contact with said contactor wire but allow said sensor element to move with respect to said arm in response to change in the vertical profile of the contactor wire as the pantograph travels therealong, and d. detecting means responsive to the movement of said sensor element with respect to said support arm to activate said adjusting means.

8. A pantograph arrangement as set forth in claim 7 wherein said airfoil element comprises a wing symmetrically mounted on an axis transverse to the direction of travel, said wing being pivotable on said axis to selectively provide negative and positive aerodynamic lift in either of two opposite directions of travel.

9. A pantograph arrangement as set forth in claim 8 wherein said wing includes a biasing flap attached to one side thereof and extending substantially normally therefrom, whereby as the pantograph travels in either of said two opposite directions, said biasing flap tends to pivot said airfoil element or its axis in a direction such that its leading edge is biased towards the side of the airfoil element to which said biasing flap is attached.

12. A pantograph arrangement as set forth in claim 7 wherein said sensing means comprises: a. a support means secured to and extending from the pantograph frame in the direction of vehicle travel; b. sensor element adjustably secured to said support arm at a point displaced from said collector shoe and extending upwardly to impinge on said contactor wire; c. biasing means for urging said upward end to maintain frictional contact with said contactor wire but allow said sensor to move with respect to said arm in response to change in the vertical profile of the contactor wire as the pantograph travels therealong; and d. detecting means responsive to the movement of said sensor element with respect to support arm to activate said adjusting means.