US3127138A

US3127138A - Railroad switch stands

Info

Publication number: US3127138A
Authority: US
Publication date: 1964-03-31
Anticipated expiration: 1981-03-31

Description

Mal 'ch 31, 1964 R. L. WILSON ETAL RAILROAD SWITCH STANDS Filed April 28. 1966 3 Sheets-Sheet 1 IN V EN TORSZ ROSSER L. WILSON ELMER E. CATON March 31, 1964 R. 1.. WILSON ETAL RAILROAD SWITCH STANDS 3 Sheets-Sheet 2 Filed April 28, 1960 INVENTORS W\LSON ROSSER L. %},MER E. CATON l vA & k wimv g3 March 31, 1964 R, L. WILSON ETAL RAILROAD SWITCH STANDS 3 Sheets-Sheet 3 Filed April 28) 1960 INVENTORSZ ROSSER L. WILSON ELMER E. CATON E i-l United States Patent OHIIC 3,127,138 Patented Mar. 31, 1964 3,127,138 RAILROAD SWITCH STANDS Rosser L. Wilson, Mahwah, N.J., and Elmer Ellsworth Caton, Pearl River, N.Y., assignors to American Brake Shoe Company, New York, N.Y., a corporation of Delaware Filed Apr. 28, 196i), Ser. No. 25,297 2 Ciaims. (Ci. 246-693) This invention relates to a railroad switch stand, and in particular to a railroad switch stand that is adapted to be mechanically operated manually or automatically by a locomotive approaching the switch, or by remote control from a control tower.

As is well known in the art, a railroad switch is thrown from one limit position between the stock rails to the other limit position by a throw rod which usually connects the switch points. The conventional mode of operation is one usually accomplished locally by means of a manual hand lever connected to the throw rod by a mechanical crank linkage or a gear arrangement. It has also been proposed to position the switch in either of its two positions by remote control from a distant location by utilizing fluid under pressure for driving a piston means which in turn operates gearing connected to the switch point throw rod, but in such systems the need for rather elaborate controls has somewhat retarded general adoption. There are times when it is important not only to operate the switch selectively by controls at a remote location, but also locally by a manually operable lever.

The primary object of the present invention is to enable a railroad switch to be operated from a remote location, automatically by a locomotive, or alternatively to be locally operated mechanically without interference from the mechanism associated with remote operation, and without need for the introduction of any settable device for changing the conditions of operation of the throw rod from local to remote operation or vice-versa.

It is anther object of this invention to construct a powerthrow mechanism for throwing the switch points of a railroad switch in either direction of movement between the two limiting positions of the switch points by the use of a force applying mechanism that need have an effective stroke in only one direction. In a preferred form of the present invention such a force applying mechanism may comprise a single-acting, fluid actuated piston.

It is an object related to the foregoing to effectively disconnect the piston, or other force-applying mechanism, from the switch points except during those periods whenever the piston or the like is actuated to throw the switch points. In this manner the piston or other force-applying mechanism offers no restriction to the movement of the switch points by other apparatus, such as a manually actuated switch stand.

In accordance with this invention the force-applying mechanism for throwing the switch points of a railroad switch includes a cam member which is mounted for rotational movement about a pivot fixed in position with respect to the stock rails of the railroad switch. Linkage means connect the cam member with a conventional throw rod of the railroad switch for shifting the switch points in a direction dependent upon the direction of rotation of the cam member. The force-applying mechanism also includes a single-acting powered element, such as a fluid-actuated piston, having an articulated push rod extending therefrom and engageable with the cam member upon actuation of the powered element to effect rotation of the cam member. It is an important feature of this invention that the articulated push rod is normally biased to a position wherein the push rod is disconnected from the cam member so that the force-applying mechanism offers no restriction to the movement of the switch points by other apparatus. It is another feature of this invention that the cam member is formed with a particular configuration so that movement of the switch points to one of the limit positions conditions the force-applying mechanism for throwing the switch points to the other limit position upon subsequent actuation of such mechanism. And to construct novel force-applying mechanism for throwing the switch points of a railroad switch which embodies the foregoing features is yet another object of this invention.

Other objects of the present invention are: to materially simplify the construction of a railroad switch stand arranged for selective operation from a remote location; to render the control less sensitive whereby the switch stand is rugged and reliable and does not require delicate adjustment and continuous maintenance; to conserve on power necessary for operation of the switch; and to produce a switch stand embodying the foregoing characteristics at an attractive cost.

Other and further objects of the present invention will be apparent from the following description and claims and are illustrated in the accompanying drawings which, by way of illustration, show a preferred embodiment of the present invention and the principles thereof and what is now considered to be the best mode contemplated for applying these principles. Other embodiments of the invention embodying the same or equivalent principles may be used and structural changes may be made as desired by those skilled in the art without departing from the present invention.

In the drawings:

FIG. 1 is a plan view of a railroad switch installation constructed in accordance with one form of the present invention;

FIG. 2 is a plan view of another form of a railroad switch stand constructed in accordance with the present invention;

FIGS. 3A through 3F are schematic views illustrating, in various phase of operation, component parts of the switch installation shown in FIG. 1;

FIG. 4 is a schematic plan view and illustrates in phantom outline relative dispositions of a plunger and roller member with respect to a cam member during both forward and return strokes of the plunger member;

FIG. 5 is an elevation view of the structure shown in bold outline in FIG. 4;

FIG. 6 is a sectional plan view of the switch stand and its mechanical operating mechanism;

FIG. 7 is a sectional elevation view of the structure shown in FIG. 6; and

FIG. 8 is a sectional view of the links of the crank shaft assembly for the switch stand shown in FIG. 6.

In FIG. 1 of the drawing there is illustrated part of a railroad switch including the two

stock rails

20 and 21 which are spiked in the usual fashion to the ties T, and the two

movable switch points

23 and 24 which are connected by the usual front and rear throw rods 27 and 28. As shown in FIG. 1, the railroad switch is conditioned for straight through movement of the locomotive.

The conventional mode of throwing a railroad switch from one of its set or limit positions to the other is by means of a switch stand which includes an operating handle having a crank connection to an arm which in turn is connected to the throw rod of the switch. In this connection, it will be observed in FIG. 1 that a switch stand 510 is mounted on the ties T outwardly of the lef hand stock rail 20. This switch stand embodies mechanical operating structure to be explained in detail hereinafter in connection with FIGS. 6, 7, and 8 of the drawings. It may here be pointed out, however, that the switch stand 510 embodies a throw handle H which is 3 adapted to operate a reciprocal connecting rod 31 in turn connected to the front throw rod 27.

Under the present invention, throwing of the

switch points

23 and 24 can be effected by a fluid-operated piston 35 which constitutes a component part of a force-applying or power-throw mechanism 36. In the form of the invention illustrated in FIG. 1, the piston 35 and related actuator mechanism are contained within a housing 37 located on the ties T outward of the right-hand stock rail 21. As will be explained in detail hereinafter the powerthrow mechanism 36 includes a cam member 38 which is pivotally mounted in the housing and linked to the throw rod 27. The power-throw mechanism also includes an articulated push-rod member 39 which is normally spaced from the cam member 38 so as to disconnect the piston from railroad switch and thereby enable the switch to be thrown by the switch stand 510 or by a train trailing the switch with no interference from the actuating cylinder 35. While the housing 37 containing the piston and related mechanism is illustrated in FIG. 1 as mounted on the opposite side of the railroad switch from the switch stand 510, the piston and related mechanism can be located adjacent the switch stand 510 with the cam member 38 mounted so as to have its pivotal axis aligned with the axis of a double-arm crank 513. This arrangement is illustrated in FIG. 2 wherein parts which correspond to like parts in FIG. 1 are designated by like reference numerals, but with the addition of the suflix A in FIG. 2.

It will be realized from the foregoing that the railroad switch in the present instance is arranged for dual operation, either by the connecting rod 31 which is operated through the switch stand mechanism 510 or by the piston 35 which is associated with the power-throw mechanism 36 to be described hereinafter. It is important to point out, however, that the mechanical operating mechanism of the switch stand 510 can be used to augment the action of the piston 35 in a unique fashion, and moreover, the power-throw mechanism 36 is so arranged as to enable the railroad switch to be thrown when desired solely by means of the operating handle H or by a locomotive approaching the switch.

The switch stand 510, shown in detail in FIGS. 6-8, for the most part is of known construction and is in the nature of that disclosed in US. Patent No. 2,575,037 and includes a housing assembled from upper and

lower castings

520 and 521. The lower casting is provided with left and right-hand horizontal flanges 523 which are reinforced by vertical gusset plates 524 and which are formed with bolt holes 529 enabling the switch stand to be fastened securely to a pair of railroad ties T as shown in FIG. 1.

The ends of the housing are formed with

sleeves

525 and 526 serving as hearing mounts for a horizontal crank assembly to be described hereinafter. The upper wall of the housing is provided with a bearing 527 and the lower wall of the housing is provided with a bearing 528, FIG. 7, for receiving and supporting a vertical spindle 533. The spindle 533 is formed at the lower end with a hub 5331-1, and oppositely directed arms 512 and 513A, FIG. 7, constituting a throw-rod operating lever are connected to the hub 533H. In the form of the invention illustrated in the drawings, the connecting rod 31, which at one end is connected to the throw rod 27, FIG. 1, is in turn connected at its other end to the arm 513A. If it is desired to locate both the switch stand 510 and the housing 37 on the same side of the railroad switch (see FIG. 2), rather than on opposite sides as shown in FIG. 1, then the cam member 38 will be mounted beneath the crank 513 with the pivotal axis of the cam member coincident with the vertical axis of the spindle 533.

The horizontal crank shaft assembly which is disposed within the switch stand 510 includes at one end a thrust bushing 541 which is mounted within the sleeve 525 as shown in FIG. 7, and at the other end the crank shaft assembly includes a spring base 542. Arranged between the bushing 541 and the base 542 is an articulated link arrangement including a pivot link 543, an intermediate link or crank pin 544 connected as a toggle unit with a rear link or crank arm 545, and a cross head 546, the latter being part of the crank shaft as will be explained. The hand lever H for manually operating the switch stand is connected to the spring base 542 by bolts 547, the hand lever fitting in a groove 548 at the outer end of the spring base 542.

The thrust bushing 541 is formed with an annular positioning flange 550 which abuts a complemental annular surface at the inner end of the sleeve 525. The bushing 541 is formed with an internal tapered socket 551 which is narrowed in the direction of the outer end of the sleeve 525. A ball 552 is mounted in a recess at the narrow end of the socket 551, and the pivot link 543 is disposed within the socket 551 and is also formed with a recess in which the ball 552 seats. It will be seen from this that the link 543 has both rotative movement and limited pivotal or lateral movement in all directions within bushing 541.

The intermediate link or crank pin 544 is formed with two end recesses so as to be generally H-shaped in section as shown particularly in FIG. 8, and the outer surface of the crank pin 544 is cylindrical so as to be capable of rotation within a spindle block 557 in which it is mounted. The block 557 has a snug sliding fit within a flat-sided opening 559 formed in a spindle box 537, and the spindle box 537 is rigidly joined to the spindle 533.

The rear link 545 is pivoted to the crank pin 544 and is also pivoted to the cross head 546. Such pivoted interconnections are conveniently aiforded by

pivot pins

552, 553, and 554 as shown in FIG. 8, and locking pins 549 are provided to hold the pivot pins in proper parallel position. The pivot pins are long enough as shown in FIG. 7 to confine the spindle block 557 on the intermediate link 544. The axes of the

links

543 and 544 and the pin 552 intersect at a common point located on the axes of the spindle 533 and the crank shaft 54246. This geometrical relationship is unstable due to play and loose fits as will be explained.

An annular spring cap 553, FIG. 6, is formed with a flange engaged by one end of a coil spring 561, and the cap 558 is formed with a relatively short stub sleeve 5585 which is centered in one end of the spring 561. The cap 558 is formed with recesses for receiving positioning and holding lugs 560, FIG. 7, of the cross head 546. The cross head 546 and the coil spring 561 constitute a crank shaft, and the cross head 546 is adapted to slide axially within the bore 555, FIG. 5, of the spring base 542. The bore 555 is rectangular in cross section, and the cross head 546 fits somewhat loosely therein but closely enough to permit no substantial relative rotation between these parts while permitting relative axial movement. When the cross head 546 slides in the bore 555 toward the operating handle H, the spring 561 is compressed.

The spring 561 also seats on a flange 556, FIG. 7, on the spring base, and the spring base has a reduced hubportion 563 which is loosely journalled in the bearing sleeve 526. An adjusting bolt 564 is passed through openings in the cross head 546 and the spring base 542 as shown in FIG. 6, and a nut 567 on the bolt 564 adjusts the outermost position to which the spring cap 558' can move with respect to the spring base 542. A builtin socket wrench 565 is used for rotating the nut 567, this wrench having a square boss 566 which fits into a complemental square opening in the hand lever H. When the hand lever is bolted to hub 563, wrench 565 and nut 567 are locked thereby in position, and bolt 564 is prevented from turning due to the engagement of its head between the legs of the strap-shaped cross head 546 as will be apparent from FIGS. 7 and 8. When it is desired to adjust nut 567, bolts 547 are removed permitting thehand lever H to be used for turning the wrench 565.

The normal position of the switch stand 510 is illustrated in FIGS. 6 and 7, and it will 'be noted that the spindle box 537 is in an off-center position defining a stable home state of the railroad switch points, and hence in efiect constitutes an actuatable crank arm with the intermediate link 544 constituting a crank pin. Moreover, the rear link 545 constitutes a crank arm while the cross head 546 and the spring base 542 constitute a crank shaft. Movement of the crank pin 544 due to any rotation of the crank shaft 54246 causes rotation of the spindle 533 which is afiixed to the spindle box 537. Such rotation of the vertical spindle may occur in one of three ways, namely, due to manual throwing of the railroad switch by means of the handle H, or as an incident to operation of the railroad switch through the hydraulic unit described hereinafter, or incidental to the warming or wedging action of the wheel flanges of the train approaching the switch points.

Thus, if it is desired to operate the railroad switch manually, the handle H is thrown through 180 from the position shown in FIG. 6. This causes rotation of the spring base 542 as well as rotation of the associated link 546 as a unitary crank shaft. At the same time, link 54-5 will describe a generally conical path as it is carried from right to left as viewed in FIG. 6 (and as indicated by the arrowed line in FIG. 7); the crank pin 544- will of necessity rotate in the spindle block 557 as it shifts the spindle block from right to left; the link 543 will of necessity rotate and oscillate in the socket 551; and the spindle block 557 turns the spindle box 537, in turn rotating the spindle 533 and arm 513-513A through 90 and imparting reciprocal movement to the connecting rod 531 which is connected to the switch point throw rod.

Now on the other hand, if the switch points of the railroad switch, FIG. 1, are operated from. a remote location through the power-throw mechanism 36 in a manner to be described hereinafter, movement of the railroad switch points to the right as viewed in FIG. 1 will of course be accompanied by movement of the connecting rod 31, and as viewed in :FIG. 6 such movement of the connecting rod 3-1 will correspond to .a clockwise rotation of the

arms

513 and 513A causing the spindle box 537 to rotate from right to left as viewed in FIG. 6. The spring base 542 is not now under this circumstance being rotated, so rotation of the spindle box 537 simply tends to straighten out

toggle links

544 and 545 causing link 5% to move axially in the direction of the handle H. It will be noted that the ball 552 and tapered socket 551 for link 543 are designed to ofier little or no resistance to the straightening out tendency, that is, link 5 13 does not bind or tense. When the links 544 and 54-5 pass through a dead-center position when straightening, their axes will be aligned with the axes of link 543, link 546 and the base 542. This dead-center position is completely unstable because of the ball 552 and the joining pins, and of course in the meantime spring 551 was undergoing compression. Therefore, as the spindle box rotates through and past dead-center position, the spring 56d immediately expands and tends in effect to drive the switch points home thereby assisting the action of the hydraulic piston. The action of the spring 561 under this circumstance, therefore, assures proper home positioning of the switch points, and it is this feature of the present invention which materially simplifies the nature of the control circuit for the hydraulic switch-throwing unit.

The operation of the parts in the switch stand 510 due to automatic throwing of the switch points by the train itself approaching the switch points is essentially the same as that to be described hereinafter in connection with what occurs when the connecting rod 31 moves under the influence of the piston 35'.

The adjusting bolt 564 enables the state of the spring 561 to be determined as of an optimum degree. in other words, the bolt 564 can be adjusted to assure that the switch points are preferably held closed by a slight degree of tension in the spring 561. It will be further noted that the links 543-546 are disposed substantially in a common plane as viewed in FIG. 7 and that the several pivots connecting these links have their" axes perpendicular to this plane. Over-centering movements of the links when the spring 561 is being compressed due to automatic operation occurs entirely within this common plane. It will also be observed that the bushing 541, the base 542 and the link 543 have substantial angular play and that the sliding fits of the spring cap 558 in the crosshead 546 are loose. Such loose play and fitting increases the instability of the linkage system during automatic operation and assures a high degree of sensitivity of the linkage system at dead-center position.

In accordance with this invention fluid-powered means are provided for throwing the switch points 23 and 24 of the railroad switch illustrated in FIG. 1 from a remote location. Such means may comprise a power-throw mechanism indicated generally by the reference numeral 36 in FIG. 1 and include the piston 35, the cam member 38, and the articulated push rod 39, which, as noted hereinabove, are disposed within the housing 37. Preferably, the housing 37 may comprise a base casting so as to afford a rigid frame on which the piston 35 and the cam member 38 are mounted. In a preferred embodiment of this invention the piston 35 is a single-acting hydraulic piston which is connected to a hydraulic pump 41 by a single conduit 42. The pump 41 is connected for rotation by an electric motor 43 so that energization of the electric motor 43 is effective to supply pressurized hydraulic fluid to the piston 35 to move the push rod 39 leftwardly as viewed in FIG. 1. The piston 35 also includes biasing means which are not illustrated, but which may comprise a conventional coil spring acting on the rod end of the piston for returning the push rod 39 to the position illustrated in RIG. 1 whenever the electric motor 43 is not energized. While in the preferred embodiment of the present invention the piston 35 is hydraulically actuated, it will be recognized that this invention is not limited to the use of such a hydraulic piston. Thus, other apparatus could be utilized for moving the push rod 3 9 into engagement with the cam member 38. For example, mechanical, electrical or pneumatc means could equally well be utilized.

Guide means in the form of a pair of guide members 44 are also mounted within the housing 37 and function to insure that the push rod 39 remains straight until it engages the cam member 38. The guide members 44 are slightly beveled at their inner edges 4413 at the ends adjacent the cam member 33 for facilitating re-entry of a swingable end portion of the illustrated push rod 39 during the return stroke of the push rod, as will be apparent from the description to follow.

The articulated push rod 39*, as best illustrated in FIGS. 4 and 5, includes a first portion 49, preferably in the form of a yoke as illustrated and which is pinjointed by a pin 51 to a second portion or piston rod 52 which extends outwardly of a piston 35. A flanged roller 43 is journalled within the free end of the yoke -49 so as to be freely rotatable therein.

The cam member 38 is of a generally T-shaped configuration with the opposite ends of the bar portion of the T turned downwardly so as to define

concave pockets

46 and 47 for the reception of the flanged roller 48 of the articulated push rod 39. The cam member 38 is fixed to a spindle 53 which is mounted in a bearing 54 (see FIG. 5) in the housing 37. As is apparent in FIGS. 3A3F, the

pockets

46 and 47 are symmetrically disposed with respect to the rotational axis of the spindle 53.

A link member 56 is keyed or otherwise non-rotatably mounted on the spindle 53 so as to be rotatable with the cam member 38. An elongated slot-shaped aperture 57 is formed in the outer end portion of the link member 7 56, which end portion is interposed between two lugsformed on the end of the throw rod 27 (see FIG. and receives a vertically extending bolt or pin 58 therein. In this manner the link member 56 interconnects the cam. member 38 with the throw rod 27 so that rotation of the cam member is eifective to throw the switch points 23 and 24. The slotted construction of the link member 56 affords a limited amount of lost motion in the connection between the cam member and the throw rod 27 so that the switch points 23 and 24 may be adjusted without the necessity of making corresponding adjustments in themechanism in the housing 37.

In FIGS. 3A3F the relative dispositions of the component parts of the power-throw mechanism are schematically illustrated in a sequence illustrating a single power stroke and subsequent return stroke of the push, rod 39, with the switch points 23 and 24 initially in the position illustrated in FIG. 1. Thus, the push rod 39 is shown in its fully retracted position in FIG. 3A. In FIG. 3B the piston 35 has been actuated to move the flanged roller 48 into initial engagement with the periphery of the cam member 33. At this time it should be noted that the guide members 44 are still effective to maintain the yoke 4% in alignment with the piston rod 52. Continued movement of the yoke 49 outwardly of the guide members. 44 enables the flange roller to move into position in the pocket 47, as illustrated in FIG. 3C. Thereafter, movement of the piston rod 52 to the left rotates the cam member 38 about the axis of the spindle 53 to the position illustrated in FIG. 3D. Such rotation of the cam member 38 effects a like rotation of the link member 56 to pull the throw rod 27 to the right, as viewed in FIG. 1, and thereby throw the switch points 23 and 24 to the limit position opposite that illustrated in FIG. 1. During such rotation of the cam member 38 it is necessary only that the piston 35 move the articulated push rod 39 sufficiently far to move the over-center linkage of the switch stand 510, described hereinabove with respect to FIGS. 6 and 7, beyond the center position of this linkage. Thereafter, the spring 561 of the switch stand 510 insures that the switch points 23 and 24 complete the movement to the limit position opposite that illustrated in FIG. 1. Thus, the manner in which the switch stand 510 coacts with the power throw mechanism of the invention insures that the switch points do not remain in an open position even if some malfunction should occur during the power stroke of the piston 35. The yoked construction of the articulated push rod 39 enables the push rod to clear the cam member 38 during rotation of the cam member from the position illustrated in FIG. SC to that illustrated in FIG. 3D.

Upon completion of the rotation of the cam member 38 to a position corresponding to movement of the overcenter linkage of the switch stand 510 some distance beyond its center position, the supply of pressurized fluid to the piston 35 is cut-off and the return biasing means, hereinabove described, retract the articulated push rod 39 in the sequence illustrated in FIGS. 3E and 3F. During such return movement, the beveled surfaces 4413 return the yoke to alignment with the rod 52.

Upon the conclusion of the retraction stroke of the articulated push rod 39, the power throw mechanism 36 is conditioned to throw the switch points 23 and 24 in an opposite direction on the next power stroke of the piston 35. Thus, as illustrated in FIG. 3F, movement of the push rod 39 leftwardly on the next power stroke of the piston causes the flanged roller 48 to seat within the pocket 46 and rotate the cam member 38 and link member 56 in a counterclockwise direction, as viewed in FIG. 3F, about the spindle 53. Such rotational movement of the link member 56 is effective to shift the throw rod 2'7 leftwardly, as viewed in FIG. 3F, to return the switch points 23 and 24 to the position illustrated in FIG. 1.

In FIG. 4 the mode of operation of the power throw mechanism as described immediately above is illustrated in a single figure. The positions of the cam member 38 and the link member 56 which correspond to the disposition of the switch points 23 and 24 in the limit position illustrated in FIG. 1 are shown by the bold outline of the cam member 38 and the link member 56. In such a disposition of the cam member and the link member the flanged roller 48 successively travels through the positions indicated as 483-1, 48B-2, 4813-3, and 48B-4 on a power and return stroke of the push rod 39. On the next power and return stroke of the push rod 39 the flanged roller 43 successively travels through the positions indicated as 4884., 48A-1 (in which position the flanged roller seats within the pocket 46), 4-3A2, and 48A-3.

As noted hereinabove, it is not necessary that the powerthrow mechanism be disposed on the opposite side of the railroad track from that of the switch stand 510. The power throw mechanism can as well be mounted adjacent the switch stand 513A, as illustrated in FIG. 2. In such a case, the spindle 53A of the power-throw mechanism 36A is axially aligned with and connected to the spindle 533 (see FIG. 7) of the switch stand immediately beneath the crank

arms

513 and 513A. In such an arrangement, and as illustrated in FIG. 2, the articulated push rod is maintained in spaced relation from the cam member 38A except whenever the piston 35A is actuated. Thus, the switch points 23A and 24A may be thrown by the switch stand SlilA without any resistance by the piston 35A, but the beneficial relationship of utilizing the force of the spring 56 (see FIG. 7) to insure closing of the switch points 23A and 24A on actuation of the power-throw mechanism 36A is obtained in the same manner as in the arrangement illustrated in FIG. 1, and as described in detail hereinabove.

As noted hereinabove, the hydraulically actuated mechanism illustrated and described represents only a preferred form of the present invention. If desired, suitable mechanical, pneumatic, or electrical apparatus could as well be used for supplying the switching force; the novel and useful aspect of the present invention being particularly manifest in the ability to utilize a forceapplying mechanism, such as the specifically described hydraulic piston, that need have an effective stroke in only one direction.

It will be seen from the foregoing that we are able to throw a railroad switch by a force applied by a mechanism controlled from a remote location while at the same time allowing for local throwing of the switch by a mechanically applied force. The remotely controlled mechanism is disconnected from the switch points during all periods except those whenever such mechanism is actuated to throw the switch points so that the force-applying mechanism offers no resistance to the throwing of the switch points by either the switch stand or a train trailing the switch. By reason of the configuration of the cam member and articulated push rod employed in the present invention, only one single-acting piston or the like is requiredto throw the switch points in either direction. Throwing of the switch points in one direction is effective to condition the remotely controlled mechanism for throwmg the switch points in an opposite direction on subsequent actuation of the mechanism. Additionally, the means for throwing the switch by a mechanically applied force embodies a helical spring and a toggle linkage so connected thereto that when the switch is thrown by the remotely controlled mechanism the toggle is straightened, applying a compressing force to the spring about midway 0f the switch point throwing distance, and as the switch point is moved through the remainder of its distance, the toggle passes through and beyond its dead-center (or over-center) position whereupon pressure on the spring is released and the spring expands to assist or aid the remotely controlled mechanism which is moving the sw tch point. Hence, while we have illustrated and described preferred embodiments of our invention it is to U be understood that this is capable of variation and modification, and we therefore do not Wish to be limited to the precise details set forth, but desire to avail ourselves of such changes and alterations as fall within the purview of the following claims.

We claim:

1. Apparatus for shifting the switch points of a railroad switch between two limit positions and comprising: a manually operable switch stand including over-center linkage means connected to said switch points for shifting said switch points between the two limit positions, said over-center linkage members having a spring exerting a biasing force for maintaining said switch points in each of the limit positions; power means connected to said switch points and operable to move said over-center linkage means past dead center whereby said switch stand is operable to shift the switch points to a limit position and to exert a biasing force for maintaining the switch point in a limit position; said power means including cam means mounted for rotational movement about a pivot axis fixed in position with respect to the railway switch, link means interconnecting said cam means and said switch points and being rotatable with the switch points for moving the switch points in a direction dependent upon the direction of the rotation of the cam means, and remotely actuatable means including a push rod normally spaced from said cam means so that the switch points are shiftable by the manually operable switch stand without restriction by said push rod, said push rod being engageable with the cam means upon actuation of the remotely actuatable means to move said switch points through said link means short of each one of said limit positions and to move said over-center linkage means over the dead center position whereby said spring-biased over-center linkage means moves said switch points to a References Cited in the file of this patent UNITED STATES PATENTS 922,396 Davenport et a1 May 18, 1909 980,473 Allen Jan. 3, 1911 997,897 Blattle July 11, 1911 1,007,886 Miller Nov. 7, 1911 1,106,576 Miller Aug. 11, 1914 1,666,911 Prescott Apr. 24, 1928 1,667,473 Howe Apr. 24, 1928 1,694,050 Young Dec. 4, 1928 1,886,987 Taylor Nov. 8, 1932 2,092,828 Home Sept. 14, 1937 2,126,033 Randol Aug. 9, 1938 2,169,822 Armstrong et al Aug. 15, 1939 2,575,037 Andersen Nov. 13, 1951 FOREIGN PATENTS 9,784 Great Britain 1912 114,898 Australia Mar. 17, 1942 311,450 Switzerland Jan. 31, 1956 954,609 Germany Dec. 20, 1956

Claims

1. APPARATUS FOR SHIFTING THE SWITCH POINTS OF A RAILROAD SWITCH BETWEEN TWO LIMIT POSITIONS AND COMPRISING: A MANUALLY OPERABLE SWITCH STAND INCLUDING OVER-CENTER LINKAGE MEANS CONNECTED TO SAID SWITCH POINTS FOR SHIFTING SAID SWITCH POINTS BETWEEN THE TWO LIMIT POSITIONS, SAID OVER-CENTER LINKAGE MEMBERS HAVING A SPRING EXERTING A BIASING FORCE FOR MAINTAINING SAID SWITCH POINTS IN EACH OF THE LIMIT POSITIONS; POWER MEANS CONNECTED TO SAID SWITCH POINTS AND OPERABLE TO MOVE SAID OVER-CENTER LINKAGE MEANS PAST DEAD CENTER WHEREBY SAID SWITCH STAND IS OPERABLE TO SHIFT THE SWITCH POINTS TO A LIMIT POSITION AND TO EXERT A BIASING FORCE FOR MAINTAINING THE SWITCH POINT IN A LIMIT POSITION; SAID POWER MEANS INCLUDING CAM MEANS MOUNTED FOR ROTATIONAL MOVEMENT ABOUT A PIVOT AXIS FIXED IN POSITION WITH RESPECT TO THE RAILWAY SWITCH, LINK MEANS INTERCONNECTING SAID CAM MEANS AND SAID SWITCH POINTS AND BEING ROTATABLE WITH THE SWITCH POINTS FOR MOVING THE SWITCH POINTS IN A DIRECTION DEPENDENT UPON THE DIRECTION OF THE ROTATION OF THE CAM MEANS, AND REMOTELY ACTUATABLE MEANS INCLUDING A PUSH ROD NORMALLY SPACED FROM SAID CAM MEANS SO THAT THE SWITCH POINTS ARE SHIFTABLE BY THE MANUALLY OPERABLE SWITCH STAND WITHOUT RESTRICTION BY SAID PUSH ROD, SAID PUSH ROD BEING ENGAGEABLE WITH THE CAM MEANS UPON ACTUATION OF THE REMOTELY ACTUATABLE MEANS TO MOVE SAID SWITCH POINTS THROUGH SAID LINK MEANS SHORT OF EACH ONE OF SAID LIMIT POSITIONS AND TO MOVE SAID OVER-CENTER LINKAGE MEANS OVER THE DEAD CENTER POSITION WHEREBY SAID SPRING-BIASED OVER-CENTER LINKAGE MEANS MOVES SAID SWITCH POINTS TO A LIMIT POSITION AND EXERTS A BIASING FORCE FOR MAINTAINING THE SWITCH POINTS IN SAID LIMIT POSITION.