US2893718A

US2893718A - Force reversing buffer mechanisms

Info

Publication number: US2893718A
Application number: US541429A
Authority: US
Inventors: Kenneth J J Mcgowan
Original assignee: Westinghouse Air Brake Co
Current assignee: Westinghouse Air Brake Co
Priority date: 1950-09-30
Filing date: 1955-10-19
Publication date: 1959-07-07
Anticipated expiration: 1976-07-07

Description

K. J, J- MQGOWAN FORCE REVERSING BUFFER MECHANISMS 3 Sheets-She et 1 Original Filed Sept; 30. 1950 July 7,1959 K. a. J. M GOWAN FORCE REVERSING BUFFER MECHANISMS Original Filed Sept. 30, 1950 3 Sheets-Sheet 2 INVENTOR. Kenneth J1 MQGowan (d A 121s ATToRMz X \N 5% so m July 7, 1959 K. J. J. M GOWAN FORCE- REVERSING BUFFER MECHANISMS 3 Sheets-Sheet 3 Original Filed Sept. 30, 1950 \6 M M a y w. .M M

HIS

2,893,718 iatented July 7, 1,959

States Patent Ofiice 2,893,718 FORCE G BUFFER MECHANISMS Kenneth J. J. McGowan, Pittsburgh, Pa., assignor to Westinghouse Air Brake Company, Wilmer-ding, Pa., I a corporation of Pennsylvania Original application September 30, 1950, Serial No. 187,789, now Patent No. 2,747,860, dated May 29, 1956. Dividedand this application October 19, 1955, Serial 1N0. 541,429

12 Claims. (Cl. 2671) ing Buffer'Mechanism, which issued as Patent No.

2,747,860 ,.on May 29, 1956.

Spring switch installations on railroads provide means for making trailingtralfic moves from a siding onto the main line, or from one track to another track depending on the direction of the move without the need or requirement of stopping the train or car and throwing the switch to a reverse position before completing the move. Such installations also permit the move to be made without stopping the train or car after the move has been made to reset the switch. The spring switches used in such installations are provided with springs which resiliently connect the movable rails to the respective switch operating mechanisms. The resilient connection of the switch points permits theswitch to be'trailed, the spring bias returning the points to their normal or closed position.

In trailing a spring switch, the flanges of the car wheels move the switch points toward their reverse or open positions, thereby increasing the biasing force exerted by the spring connection. As soon as the car wheels roll off the points, the spring will snap the points toward their normal or closed position, the points being operated against the flanges of the next set of car wheels. The continuous slapping of the switch points by and against the car wheels results in undesirable'wear on the switch points, and the resultant-vibration may cause damage to the switch operating stand.

To minimize the wear in spring switch installations due to the slapping of the switch points, buffer mechanisms and other devices have been provided for such instal1a tions which hold the switch points in their reverse or open position after being trailed fora predetermined period of time and/or retard the return of the switch points by the spring to their normal or closed positions. While such butter mechanisms and devices have reduced the slapping of the switch points to great extent, such mechanisms required the switch points to be moved :by the (flanges of the car wheels toward their open or reverse positions. The moving of the points by the car wheels during a trailing move may cause some damage to the points which would be detrimental in permitting high speed facing point moves over the spring switch.

It is an object of my invention to provide a butter mechanism for a spring switch wherein the movement of the switch points a predetermined distance away from their normal positions during a' trailing move will cause a reversed force to be applied to the switch points by the buflFer mechanism to bias the switch points the remainder. of the distance to their open or reversed positions.

A further object of this invention is to provide a force reversing butter mechanism for a. spring switch whichv will retard the return of the switch points from their trailed positions to their normal or closed positions.

, Another object of my invention is to provide a force reversing buffer mechanism for a spring switch whereby a reversed force is applied to the switch points to move the switch points additional increments of the distance the switch points are moved during a trailing move.

, Still another object of my invention is to provide a double-acting, force reversing butter mechanism for a spring switch which will operate in a forward direction as well as in a reverse direction should the switch be trailed in either its normal or reverse position.

A further object of the invention is to provide a force reversing butter mechanism for a spring switch wherein the energy stored in the butter spring of the mechanism resulting from atrailing move is contained by the mechanism should the switch be reversed by the operation of the hand-throw lever of the operating stand.

In carrying out my invention I provide a double-ended cylinder arrangement mounted on the head rod of a spring switch, in which two independent piston assemblies are slidably received, the two piston assemblies being biased to their extreme outer positions against the cylinder heads by a buffer spring. The two piston assemblies are similar, both being of cylindrical form, the end of one assembly being slidably received in a fluid-tight arrangement withi in the other, and both acting in turn as cylinders for two small pistons receivable therein and fixed in spaced relation on a piston rod. The two piston assemblies are each provided with a bypass valve, while each of the two small pistons cooperate with a dual valve arrangement. The piston rod is provided with two spaced relieved portions forming cavities within the space which cooperate with the dual valve arrangements. I

The bufier mechanism is filled with a suitable fluid, such as light oil. The buffer spring is initially stressed when the switch points and switch operating mechanism are in their normal positions by taking up on a coupling interconnecting the piston rod and the switch operating rod; The take-up on the coupling will cause a relative movement with respect to the cylinder arrangement of the small pistons and one of the piston assemblies. One piston assembly is thus spaced from its cylinder head to form a pressure cavity within the piston assembly. The positioning of the one piston assembly will also close the first valve and open the second valve of the cooperating dual valve arrangement. The dual valve arrangement provided for the other piston assembly will have its two valves in opposite positions, i.e, the first valve open and the second valve closed, the open valve venting the interior of the second piston assembly behind the closed first valve.

When the spring switch is trailed, the cylinder arrangement described will be moved relative to the piston rod, thereby moving one piston assembly relative to the other to telescope the two piston assemblies. The hydraulic pressure in front of one piston will increase due to the decrease in volume of the fluid cavity formed in and by the piston rod within the piston assemblies. The increased pressure of the fluid in the cavity will cause the stationary piston assembly to move in a direction opposite to the movement of the cylinder arrangement.

by the moving cylinder arrangement.

The high pressure of the cavity in the piston rod is finally relieved when the closed second valve of the second dual valve arrangement is brought in alignment with the cavity in the piston rod. This valve now opens relieving the pressure which would permit the piston vas semblies to return to their initial positions under the influence of the stressed buifer spring. The tendency of the piston assemblies to return to their initial positions is checked by the, closing of the byrpassvalves associated with the assemblies. Consequently the fiuid-behind-the pistonassembliesis under pressure. This. pressure is transmitted to the cylinder head to move the cylinder arrangement in the direction in which .it was .moved by the trailed switch, thereby moving the switch points of the spring switchto their full reverse or, open position.

A; small leak orifice is provided ineach of the piston assemblies to permit the return of the piston assemblies to their initial positions to .restore theswitchpoints to their normal positions;

The same action, although in obverse order, takes place when the, switchis trailed in itsreverse position. In .thisinstance the second piston. assembly and thesecnd small piston control the action of the valves.

Otherobjectsand characteristic features of my invention .will become apparent as .the'description-proceeds.

I shall describe oneform of a buifer mechanism; embodying myinvention, and shall then point out the novel features thereof in claims.

In the accompanyingdrawings,

Fig. 1 is a plan. view of a railway switch operated by a switch operating mechanism and showing the connection of.my buffer mechanism. to the head rod of the switchand the operatingrod of' the switch operating mechanism.

Fig. 2 is .aviewof the buffer mechanism and switch operating parts takenalong the section line 11-11 of Fig. 1.

Fig. 3 is a, vertical longitudinal viewof my bulfer mechanism.

Figs. 4 and 5 are fragmentary enlarged sectional views of thevalve assemblies shown in Fig. 3.

Fig. 6 is an enlarged sectionalview.takenalong the line VL-VI of Fig 3,.while Fig. 7 is a sectional viewtaken along the line VII-VII of Fig. 4.-

Similar reference charactersrefer to similar parts in each of the several, views.

Referring to Figs. 1 and 2 0i thedra wings, thereference character A designates a railway switch comprising two fixed railslandlq and two'movable rails Zand 2a.- The fixed raile arelaid on the tie plates 3 andare secured to the cros sties .4- in the usualjmanner. The movablerails .-2 -and2a are fastened togetherby a-front rod 5 and ahead rod 6,, and may be -moved into a normal position-or reverse positionby means of a switeh operating mechanism B which is connected with the head rod ,6. Whenthe switch .Ais in its normal position as illustrated in Fig. 1, the, movable rail ,2 engages the. ,fiXedmail. 1 and the,movable.rail 2a isspaced away-from the fixed rail 1a. When the switch is reversed, the movable rail 2a engagesv the fixed rail 1a while-themovable railZris spaced from. they fixed rail. 1.

The switch operating. mechanism B is similar'to theswitch operating mechanism described in Letters vPatent of the United States No, 2,387,826, grantedto Herbert L. Bone .on October 30, 1945, for-Railway Switch Operating Mechanisms. bolted inthe usual manner to the ,crossties ,4 .and-isprovidedwith-a hand-throw lever 7 cooperating through suitable mechanism (not shown) with anoperatingcr-ank.

7a supported from a housing 8 provided for thernechanism. The .operating crank 7a-is pivoted to a jaw ,9 by

The switch operating mechanism is;

4. switch is trailed in its reverse position, as will hereinafter be described.

The end of the switch operating rod is fastened by way of a threaded coupling 13 and locknut 13a to the end of a piston rod 14 of my novel buifer mechanism 15. The buifer mechanism 15 is pivotally supported on two spaced-lugs 16.,on the, head rod 6 by wayof two vertical trunnions 17 formed on a central housing 18 of the buifer mechanism, the trunnions beingqreceived withinsuitable openings in the spaced lugs- It will be appreciated from the foregoing brief description of the switchA and the switch operating mechanism B, that rotation ofthe hand-throw lever;7 approximately 180 degrees in a counterclockwise direction when viewed from the right side in Fig. 1, will move the switch to its reverse position byway of crank 7a, jaw 9, the switch operating rod 10, bufler mechanism 15, and the head rod .6 so that the .movablerai-l 2a willbe against the fixedrail 1a.. Clockwise rotation of the hand-throw lever 7 will .move the switch back. to-its normalposition in which the movable rail 2 will be against the fixedrail Las illustratedin Fig. 1.- 7

Referring now in detail to-Figs.. 3 to. 7, the ,bufier mechanismls comprises the central housing,,18 andtwo endcylinders. 19@and 19a screwed-into threaded-openings 1811 provided in the endsof the housing. The cylinder-19 is. closed at its outer-end by: a-.cylinder head 21}, while theopen end of. cylinder 19a.is.closed, by a cylinder head. 21. provided with a conventional packing gland. and nut 23 to accommodate-the pistonrod 14.

Assembled within the. cylinders 19--and 19a, are two piston assemblies 24' and ,24a, respectively, biased to. their extreme outer positions. against their. cylinder heads by a coil spring 25. For reasons.hereinafterapp earing,.the piston assembly 24 is illustrated vin Fig; 3 in spaced relation, with respect to. the cylinder head 20. The two pistonassemblies are of similar-construction,.,and-a.description of one assembly-will therefor-be suflicientfor. a complete understanding of the construction of-theother assembly, the same reference characters being. applied to the samei parts followed by the distinguishing subscript a for-,the right-hand assembly,

way. of a-pin Sta,v the jaw being fixed to a switch operating rod 10. The operating rod.has.threaded thereontwo spaced stops 11 and 12 'lo ckedyinrplaceby nuts 11a and;

12a.. T hestop. 11 affords a positivestopin conjunction with the casing 8-for undesired motionof .the operating. rodwhen the bulferspring forces are reversed during-a trailing movement when the switch. is in its normal position, the stop 12- servingthesamefunctionwhen-the= The piston assembly241comprises ar -cylindrical mem. ber -2 6;having threadedthereon a, piston member; 27 previdedwith piston rings; 28 in the 1 usual 'manner. to minimize-fluid leakage. The pistonmember-27 is formed with a plurali ty of elongated arcuate-sports -29'-(Fig. 6). The parts 29- terminatein valve seats 30 engagedby a spring biasedannular valve member 31, ;hereinafter referredto as the ring; relief valve 31. Thering; relief valve 31 is formed with an annular-lip 32 (Fig. 5) form: ing a spring seat forone end ofa-coil compression spring 33.;encircling the cylindrical member 26,- the-other end offthe spring being held by 'a ring;34' fixed'adjacent thend 1 :t e.cylin ric lame ber-z. A e ndring;ssjfixed: to, the;-rnember-26. ,andspaced; from; -the-ring -34 servesas a stop for the ring relief 'valve 31.. For-purposes herein'-;- after appearing; the; ring ;relief;valve z 31 is I formed with. a. cur ent portion which ;registers with: one of the ports ZQiOQfQImarelief orifice:36.,(Fig.-,5 v

Adjacent the inner; end :of the cylindrical :member; 26; are a plurality of relief ;ports 37, WhilQ;,th6. .lI1tITla1Sul'i face of 1 the inner end is provided with. Lthreads' -38 for supportingya cylindrical member 39 :ofreduced :diameter' which"; extends :slightly beyond the middle ;of :the; central housing 18. It will be :noted-that-the extending end-of; the-cylindrical member :39 forming apart of 'the;piston assembly. 2.4 is slidably: received within. the; cylindrical member .39a, forming a .part fOf the. piston-Hassembly'24a, piston. rings .40 .being provided. adjacent '[hBfiIldS of Elem-1 ber. 39at-tol-minimize fluid leakage betweenthe parts ofthe-tw.o. assemblies.

Slidablyre'ceived with the cylindrical members '26:.and: 26a=of th two piston assembliesare small i 'pistons 41 and=- 41a; respectively, fixed in 'spacedrelationeon -re duced portions 42a of axpiston rod extension 42. 'The pistons 41 and 41a,.areprovided with suitable piston rings 43 and 43a. 'For p poses hereinafter appearing, the piston rod extension 42 is formed with relieved portions 44 and 45 which are so spaced that when the two piston assemblies 24 and 24a are in their extreme posi tions illustrated in Fig. 3, the two relieved portions are located approximately equidistant on opposite sides of the center line of the buifer mechanism.- Thepiston rod extension received within the cylindrical member 39 of the pistonassembly 24 forms a space or channel 46 between the rod and the interior of the cylindrical member, the relieved portion 44 forming a cavity 47. The piston rod extension received within the cylindrical member 39a forms a similar space or channel 48, the relieved portion 45 of the rod forming a cavity 49.

An internal annular recess ,50 is provided in the cylindrical member 26 adjacent to the inner ends of the threads 38 (Fig. 4). Received within said recess, and clamped in place by the cylindrical member 39 is an annular insert 51 having a ring portion 52 extending in back of, but spaced from the ports 37, of the member 26. For purposes hereinafter appearing the insert 51 is further provided at its inner end With a bevelled surface 53 forming a valve seat, and a shoulder 54 forming a spring abutment means.

Adjacent to the right-hand end of the small piston 41 and encircling the piston rod is a circular relief valve 55 having a plurality of ports 56 formed at its inner,

edge by radial legs or extensions 57 .(Fig. 7), and having an extending ring portion 58 at its outer edges; A suitable piston ring 59 is provided for the valve 55. A coil compression spring 60 encircling the piston rod and interposed between the small piston and the circular relief valve 55 biases the valve against the seat formed by the edge of the extending ring portion 52 of the insert 51'. It will be noted that the extending ring portions 52 and 58 form a vent to the relief ports 37 which is effectively sealed by the circular relief valve 55.

An annular relief valve 61 is also provided for cooperation with the insert 51 and thecircular relief valve 55, the annular valve being slidably receivable in a fluidtight relationship on the piston rod extension 42. The annular valve 61 is provided at its inner end with an extending ring portion 62, the rear surface of which is bevelled as at 63. The outer end of the circular valve is provided with a radially outwardly extending ring 64 to form a shoulder 65. Interposed between the shoulder 65 of the annular relief valve and the shoulder 54 of the insert '51 is a coil spring 66 tending to bias the annular relief valve in an outward direction against the inner face of the circular relief valve 55. The spring 60 biasing the circular relief valve 55 against the ring 52 of the insert is made stronger than the spring 66. Thus, if the circular valve 55 is maintained in a closed position to seal off the port 37 in the'manner hereinafter described, the annular valve 61 will be maintained in a position wherein the bevelled surface 63 is spaced from the valve seat 53-of the insert. A passage is thus provided from the space 48, cavity 49, cavity 47, and space 46, through the open annular valve 61 to the inner side of the small piston 41.

It will be noted that the valve assemblies on the right side of the bufier mechanism are similar to those de-- scribed for the left side of the mechanism and have been given the same reference characters followed by the subscript a. In the case of the valve assemblies on the right side, the annular valve61a is illustrated in Fig. 3 as being closed, while the circular valve 55a is shown open to provide a passageway to the relief ports 37a.

In placing the buffer mechanism 15 into operation, all available interior space within central housing 18, the

end cylinders

19 and 19a, including the

channels

46 and 48 and the cavities 47 and 49, is filled with a suitable operatfiuid such asa light oil. ..For this purpose a. filler plug 67 is provided on the central housing 18; drain plugs 68 being provided on both sides of the housing near the bottom wall for emptying the buffer mechanism. With the switch A and the switch operating mechanism B both in their normal positions as illustrated in Fig. l, the bufier spring 25 is initially stressed to apply an initial biasing force to the switch points to hold them in their normal positions with a predetermined force. The coupling 13 interconnecting the end of the piston rod 14 and the operating rod 10 is turned by a wrench or other suitable tool While the piston rod 14 is held against tuming. Referring to Figs. 3 and 4, it will be noted that the cylindrical members 26 and 26a are provided on their inner surfaces with integral

annular shoulders

69 and 69a, respectively. The movement of the piston rod 14 to the right caused by taking up on the coupling 13 brings the inner end of the small piston 41 into engagement with the shoulder 69. The cylindrical member 26 is thus moved to the right, away from the cylinder head 20 to form a cavity 70. The buffer spring 25 iscompressed due to abutment of the cylindrical member 26a against the cylinder head 21. The piston assembly 24 may be readily moved in making this adjustment in view of relieved sections 71 (Figs. 3, 5 and 6) provided in the cylindrical member 26 and straddling the piston member 27. The initial stressing of the spring 25 serves to provide a biasing force for maintaining the movable rail 2 against the fixed rail 1 under pressure when the switch is in its normal position as illustrated. When the parts are adjusted in the manner illustrated and described, the coupling 13 is made secure by the locknut 13a.

The parts are so proportioned and the throw of the crank 7a so adjusted that when the switch operating mechanism is operated to its reverse position, the piston rod 14 will be inserted into the buffer mechanism so that the small piston 41a moves to the left carrying the. piston assembly 24a therewith, the buflfer spring 25 forcing the piston assembly 24 against the cylinder head 20 so that the entire buflfer mechanism is moved to the left to reverse the switch points, the biasing force of the buffer spring maintaining the movable rail 2a against the fixed rail 1a.

The movement of the small piston 41 to the right in initially stressing the buffer spring 25 when the switch A is in its normal position, tends to increase the bias of the spring 60, thereby holding the circular valve 55 against the valve seat formed by the extending ringf52 of the annular insert 51. The inner side of the circular valve 55 being abutted by the outer end of the annular valve 61 will hold the valve 61 open as illustrated in Figs. 3 and 4. As previously described the biasing spring 60 for the circular valve 55 is stronger than the biasing spring 66 provided for the annular valve 61, so that the biasing spring 60 will overcome the biasing spring 66. It will be noted that the circular valve 55a is op en and the annular valve 61a is closed on the right side of the buffer mechanism 15. The movement of the piston rod to the right in initially stressing the spring 25, moves the small piston 41a to the right, thereby relieving the biasing spring 60a of the circular valve. The biasing. spring 66a for the annular valve 61a thus closes the annular The housing18 and the

cylinders

19 and 19a will bev moved to the left by the head rod 6 relative to the piston rod 14 which is coupled to and held by the switch operating rod 10.

For a clearer understanding of the operation of the bufifer mechanism, thedescription of operation herein after given- -will'assume--the-housing 18 and} the :

cylinders

19 and 19a-=as remaining stationary andthe piston-rod= 14=as moving and being-moved to the right.-

The relativewithdrawal of' the piston rod to the right will move the pistonassembly 24 therewith to the right. The movement of the piston assembly-will cause-adisplacement of; the fluid in the cavity 49 due to the telescoping of the piston assemblies '24 and 2461. Since the: annul'ar valve- 61-isoperr and the annular valve 610 is closed, the fluid -in channels 46; 48 and in cavities 47, 49"

will enter-the cavity between thesmall piston4-1 and the circular valve-55" sealing 'the'ports 37. Thefluidinthe channels and cavities will beunder pressure due to thedecreasingvolume'of the cavity- 49 due to the movement of the-piston rod andpistonassembly-24. The fluid -un der pressure'entering the cavity inback of the circular valve 55 willforce the-piston assembly 2.4 ahead of the small-piston 41. It will be appreciated-that the movement" of the piston assembly tothe right will not be retarded due to any building upof pressure ahead of the piston member '27. The relieved portions 71 ofthe cyl-' inder 19'and-the open ring valve'31-will permit the free flow of fluid'through and around the piston -member 2 7.-

The continued withdrawal of the piston -rod 14 will move the small piston 41to the right while thepistonassembly- 24 will be movedto the right an equal'di'stanceplusincrements of the distance the piston24' is-moved due tothe increases in the hydraulic pressure;

It will be understoodthat the-withdrawalof the'pis'tonrod 14 moves both of the small pistons 41 and 41a. The

movement 'ofthe small piston-41a will not be retarded by any hydraulic pressure building up-behind it during its movement. The fluid within the cylindricahmember 26a behind'the small pistonwill flow out theend of the cylindrical member, past "the cylinder head 21 and around thepiston'member 27a-by way-of-the leak grooves 71a formed in'the cylinder 19a."

Ata point where the "relieved portion 45 of-thepiston rod extension 42 is aligned with the-left-hand end of the closed annular valve 61a, the piston assembly 24 has i been moved to the right a greater distance than thesmall piston" 41. The buffer sprin-g'25 will thus be under compression'tendingto move the piston assembly 24 'to the left, the piston assembly however beingheld in'its for- Ward position'by the oil pressure in the channels'46',

48" in thecaviti'es 47, 49 and in thecavity between the small'piston 41 and thecircular valve 55'. The con-- tinued withdrawal of the piston rod 14-will bring the cavity 49"into alignmentwith the closed annular valve 61a. The alignment of the relieved portion-45 with the right-hand end of valve 61a provides a by-pass to relievethe 'highpressure of the cavity 49 through the open valve 55a and the relief ports 37d of the cylindrical memher-26a.

The bufferspring 25' being under tension will tend to move the piston assembly 24 to its initial position nowthat the hydraulic pressurehas beenv relieved; However,- any movement of the piston assembly 24 to the left will close the ring valve 31 of thepistonassembly. The

in the-cavity 70. The resultant hydraulic pressure on the fluid-in cavity 70-will be exerted on the left face of the small piston 41 to push the piston rod '14 farther inthe direction in which'it was-withdrawn. The hydraulic pressure which -moved the piston rod 14 will bemain tainedby the closedringvalve 31 thus holding-the piston rod 14 in its withdrawn position;

As previously described, the ring valve 31 is provided with a-relief--orifice 36 which registers with one of the ports 29 provided in the-piston member 27. The fluid behind the piston member 27 is thus permitted to-'-leak slowly pastthe piston member. The reversed *force on i the small piston 41 will be maintained until sufficient leakage through: orifice 36 -l1as --taken place ---which will 6 force of the buffer spring 25 is thus resistedb the'fluid permit the piston assembly to return toward its normal position under the-urgingof the spring 25; When the shoulder-69 of the cylindrical member z6 abuts' the inner" face of the small piston 41 fixed on the piston rod; the cylind-r ical memb'erof the piston assembly 24 and the piston-Tod will move together as aunit toward their-T normal positions illustrated in Fig. 3 This slow returnwill continue until the piston member- 27' is. straddled by the. leakgrooves 71 formed in-the cylinder 19: The:

return-of the piston assembly 24' and the piston to its 15 to the left relativeto :th'e piston rod 14 by theftrailedi switch-will telescope thetwo pistonassemblies 24-andl 24a to'=increase-'the fiuid pressure within the assemblies.- The release of the fluid' pressure'will tend to releasethe compressed buffer spring: 25 to'return the piston assembly 24 to its normal position The resulting closure I of the ring ,reliefivalve 31 will'prevent'the return of'thel piston assembly 24, the force of the compressed spring:

increasing the pressure: of the cavity 70'. The increased pressure of'cavity 70 will act against the cylindenhead" 20, the-pistonrod'being stationary, to move the buffer:

- mechanism 15 an additional :distanceto the left; thereby.

moving the switchpoints to their full reverse positions..-.

The fluid pressure in cavity '70 acts against the outer.

surfaceof'piston- 41 as well as against the cylinder head 203 To prevent any movement of the piston rod and topreventiany force: from. being. applied to'the crank- 7aor other mechanism=of thezswitch operating mechanism: Bi during" the" force reversing stroke of the buffer. mechanism, the :stop. '11'is so adjustedjon the operating).

rod 10 that the inward face-of thestop abuts the hens-'- ing'S-When the switch A and the switch operating mechanism' are 'in their-extreme'normal positions. The piston:

rod "14- is thus ,heldstationary, the full force of the fluid pressure in cavity 7 0: acting against the cylinder; head 20::to move the switch points over-to their full reverse position when the switch points are moved a predetermined distance by the Wheels of a trailing vehicle.

The relieforifice 36-- provided inthe ring;valve 31 i, permits the slow return to the right of the buffer-mech-- anism 15. When the leakgroove 71forn1ed in cylinder 1; 19 straddles the piston member 27 of the piston assembly 24,-.the return of the buffer mechanism will be very.

rapid, the return being accomplished by the full force of thebuffer spring to return the movable rails 2 and la to their full normal positions as'illustrated.

From the foregoingdescription of my buffer mechanismnand its operation, itwill be readily appreciated.

that the operation of the device in and from a-reverse position of the switch A is identical except in reverse.

order. In the case of the switch A being in its reverse w position and trailed, the housing. 18 and the

piston assemblies

19 and 19a will be moved to the right relative to the piston rod 14. As previously described, when switch A is in its reverse position, the circular valve 551; is closed and the annular valve 61a is open. Movement of the housing and cylinders to the right will telescope.

"the piston assemblies to increase the hydraulic pressure in cavity 47, the opening of the annular valve 61 relieving the pressure to permit the hydraulic pressure built' up in cavity 70a by the butter spring to move the housing and cylinders farther to the right to move the switch.

points to their full normal position. Relieving of the hydraulic pressure in cavity 70a through the orifice 36t will eventually permit thereturn of the housing: and cylinders to their extreme reverse positions. It will beappreciated from thesforegoingvdescriptiomi 9 that the energy stored in from a trailing move will be contained by the buffer mechanismdescribed. Theoutward bias of the compressed bulfer spring tends to move the piston assemblies 24 and 24a toward their respective cylinder heads. This outward motion however closes the ring relief valves 31 and 31a to prevent the sudden release of the compressed spring. Thus a reversal of the switch points by operation of the hand-throw lever while the spring 25 is still under compression due to a trailing move will not release the compressed spring.

It will be understood that although I have illustrated and described the buffer mechanism as being mounted on the head rod of the switch and the piston rod coupled to the switch operating rod, the buifer mechanism could very easily be fixed by Way of trunnions 17 to the switch operating rod and the piston rod pivoted or fixed to the head rod 6 of the switch. The operation of the buifer mechanism would be in the manner described 'With the piston rod moving with respect to the buffer mechanism to throw the switch points to their opposite positions when the switch is trailed.

From the foregoing description of the buffer mechanism embodying my invention, it will be appreciated that the force reversing feature of the mechanisms in movingthe switch points an additional distance in the direction in which they are trailed instead of the usual kickback action of the switch points by the wheels, will reduce the wear on the switch points, the operating switch mechanism and associated equipment, all of which tend to reduce the maintenance costs of the spring switches so equipped.

Although I have herein shown and described only one force reversing buffer mechanism embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention. 7

Having thus described my invention, what I claim is:

1. A buffer mechanism comprising two cylinders interconnected in tandem and containing a fluid, a cylindrical piston assembly reciprocable in each cylinder said piston assemblies being telescoped in fluid tight arrange ment, resilient means interposed between said piston assemblies for biasing said assemblies to initial positions, a'piston rod including relieved portions thereon being receivable within said cylindrical piston assemblies, a piston reciprocable in each cylindrical piston assembly fixed in spaced relation on said piston rod, said piston assemblies having a cavity formed therein, each piston assembly having a'relief port interconnecting said cavity with said cylinders, first and second relief valves on each of said piston assemblies controlled by the movement of said pistons and piston assemblies, said first relief valve of one piston assembly and said second relief valve of the other piston assembly sealing the associated port and a portion of said cavity in front of one of said pistons, the movement of said piston rod and pistons in a given direction increasing the fluid pressure in front of said one piston having a portion of said cavity sealed in front thereof to move its associated piston assembly in the same direction additional increments of the distance the pistons are moved to bias said resilient means, said first and second relief valves in said second piston assembly controlled by the movement in the given direction of said pistons, and cooperating with said relieved portions on said rod means to decrease the pressure in front of said one piston to permit the associated piston assembly to return to its initial position under the influence of the biased resilient means, valve means controlling fiuid flow from the front to the back of each of said piston assemblies, the return of said piston assembly increasing the pressure behind said one piston to move saidpiston an additional distance in the given direction it wasmoved.

the 'bufier spring 25 resulting 1 2. A buffer mechanism comprising two interconnected cylinders containing a fluid, a cylindrical pistonassembly reciprocable in each cylinder said piston assemblies being telescoped fluid tight arrangement, resilient means disposed to bias said piston assemblies to an initial position, a piston reciprocable in each cylindrical piston assembly and movable in unison, said piston assemblies having a cavity formed therein at a point in front of the respective pistons, the interior of each piston assembly the movement of said pistons in a given direction in-- creasing the fluid pressure in front of said one piston to move its associated piston assembly in the same direction additional increments of the distance the pistons are initially moved to bias said resilient means, said first and second relief valves in said second piston assembly controlled by the movement in the given direction of said pistons relieving the increased pressure in front of said one piston to permit the associated piston assembly to return to its initial position under the influence of the biased resilient means, the return of said piston assembly increasing the pressure behind said one piston to move said piston an additional distance in the given direction it was moved, a third relief valve including leak orifices disposed between each of said piston assemblies and said cylinders for controlling fluid flow from'the front to the back of said piston assembly, said valve means being controlled by the movements of said piston assemblies with relation to said leak orifices to per-- mit the return of said pistons and piston assemblies to their initial positions. v

3. A buffer mechanism comprising two cylinders interconnected in tandem and containing a fluid, a cylindrical piston assembly reciprocable in each cylinder said piston assemblies being telescoped in fluid tight arrangement,

resilient means interposed between said piston assemblies for biasing said assemblies to initial positions, a piston rod receivable within said cylindrical piston assemblies, said piston rod including relieved portions, a piston reciprocable in each cylindrical piston assembly fixed in spaced relation on said piston rod, said piston assemblies having a cavity formed therein, each piston assem-' bly having a relief port interconnecting said cavity with said cylinder, first and second relief valves on each of said piston assemblies controlled by the movement of said pistons and piston assemblies, said first relief valve of one piston assembly sealing the associated port and a portion of said cavity in front of said one piston, themovement of said piston rod and pistons in a given direction increasing the fluid pressure in front of said one piston to move its associated piston assembly in the same direction additional increments of the distance the pistons are moved to bias said resilient means, said first and second relief valves in said second piston assembly controlled by the movement in the given direction of said pistons cooperating with the relieved portion of said rod to decrease the pressure in front of said one piston to permit the associated piston assembly to return to its initial position under the influence of the biased resilient means, the return of said piston assembly increasing the pressure behind said one piston to move said piston an additional distance in the given direction it was moved, a third relief valve including leak orifices disposed between each of said piston assemblies and said cylinders adapted to coact with said leak orifices in said cylinders and controlled by the movements of said piston assemblies to control fluid flow between said piston mounted in spaced relation on a rod and being movablein unison, said rod including relieved port1ons, meansfor moving each of said piston assemblies by their respeotive pistons in a given direction, one piston assemblyremaining stationary while the other piston assembly is moving, a cavity within said piston assemblies, a relief port on each-piston assembly interconnecting said cavity with respective ones of said cylinders, relief-valves on each ofsaid piston assemblies controlled by the movements of the respective pistons including a first and sec-- 'ond relief valve for each of said piston assemblies,

the first and second relief valves of one piston assembly being closed and opened respectively while the first'and second relief valves of the second piston assembly are opened and closed respectively, saidfirst and second" relief valves sealing off a portion of said cavity between the forward moving face of said one piston and said one piston assembly, the movement of said one piston in a given direction increasing the pressure in said cavity in front of said one piston, a valve member disposed between each of said piston assemblies and said cylinders, the increasing pressure in front of said one piston moving the associated piston assembly ahead of the-piston in one direction to increase the bias on said resilient means, continued movement of said rod aligning the relieved portion thereon with said first and second relief valves associaed with said stationary piston assembly to relieve the pressure within said cavity through said relief port in said second piston assembly, valve means including orifice means on each of said piston assemblies and controlled by the movement of the associated piston assembly, the bias of said spring tending to return the moved piston assembly to its initial position and closing the associated valve means to increase the pressure of the fluid behind said moving piston, the increase in pressure moving said pistons and rod an additional distance in the direction the rod is initially moved, said rod, pistons and moved piston assembly returning to their initial positions by the slow release of the biased spring due to the flow of the high pressure fluid behind said one piston through said orifice means provided for said valve means of said moved piston assembly.

5 A buffer mechanism comprising two intercomiected cylinders containing a fluid, a hollow cylindrical piston assembly reciprocable in each cylinder, the end of one piston assembly being slidably received in fluid tight arrangement with the end of the second piston assembly mechanism, a compressed spring biasing each of said piston assemblies apart toward the ends of their respective cylinders to an initial position, a piston reciprocable in each' cylindrical piston assembly, said pistons being mounted in spaced relation on a rod and being movable in unison said rod including relieved portions, means for moving each of said piston assemblies by their respective pistons in a given direction one of said piston assemblies remaining stationary while the other assembly ismoving, a cavity within each of said piston assemblies, a relief port on each piston assembly interconnecting said cavity with respective ones of said cylinders, relief valves'on each of said piston assemblies controlled by the movement of the respective pistons including a first and secondrelief'valves-for each of said'piston assem blies, the first and-second relief valves'oflone" piston assembly being closed and opened respectively'whilethe first and second relief valves of the second piston assembly are opened and closed respectively, said first and second relief valves sealing off a portionof said cavity between the forward moving face of said one piston and said one piston assembly, the movement of saidpiston in a given direction increasing the pressure within said cavity in front of said one piston, a valve member disposed between-each of said piston assemblies and said cylin ders; the increasing pressure in front of saidone pistonmoving the. associated piston assembly ahead of the-'- piston in one direction to increase the bias onsaid re silient means, continued movement of said rod aligning the relieved portion thereon with said first and second relief valves associated with said stationary piston assembly to relieve the pressure within said cavity through" said relief port in said second piston assembly, valve means including orifice' means on each of' said' piston assemblies and controlled :by the movement of'the as-L sociated piston assembly, the bias'of said spring'ten'ding to return the moved piston assembly to its initial posi-' tion' thereby closing the associated valve' means to increase the pressure of the fluid behind said movingpiston, the increase in pressure moving said pistons and 7 rod an additional distance in the direction the rod is initially moved, said rod, pistons and moved piston assembly returning'to their initial positions by the slow release of the biased spring due to the flow of the high'. pressure fluid behind said one piston through said valve means including said orifice means of said moved piston assembly.

6. A buffer mechanism comprising a housing including two aligned end cylinders containing a fluid, a cylindrical piston assembly reciprocable in each of said'end cylinders, portions of each said piston assembly being spaced from the respective cylinders, said piston assemblies being,

telescoped in one another in a fluid tight arrangement, a spring interposed between both of said piston assemblies for biasing said assemblies toward the ends of their respective cylinders, a rod receivable within said piston assemblies, said rod including relieved portions, a piston reciprocable in each of said piston assemblies, said pistons being fixed in spaced relation on said rod, the interior of each piston assembly in back of the respective piston being open to the respective cylinder, relief ports in each of said piston assemblies venting the interiors thereof, a relief valve arrangement for the relief ports in each piston assembly controlled by the movement of said pistons. and piston assemblies, the movement of said rod in. the one.

direction moving said pistons and one of said piston asv semblies to actuate said relief valvesof said piston assemblies to seal ofl said relief ports to increase the pressure in front of said one piston, the increasing pressure in front of said one piston moving the associated piston assembly ahead of the piston in a direction to increase the bias of said spring, the continued movement of said rod permitting the relief valve arrangement associated withthe other piston assembly to relieve the high pressure; through the relieved portions of said rod and the relief I ports of the other piston assembly, valve means on each said piston assembly controlling theflow-of fluid in the space between each piston assembly, and the associated: cylinder, said valve means being controlled by the movement of the associated piston assembly, the bias of said. spring tending to return the moved piston assemblyto its initial position and closing said associated valve means-i thereon to increase the pressure of the fluid behind said 1 one piston, the increase in pressure moving said pistons: and rod an additional distance in the one directionsaidx rod is initially moved.

7. A buffer mechanism comprising a housingrincludingr'. two aligned end cylinders-containinga fluid, a cylindrical piston assembly reciprocable in each ofsaid end cylinders, the end of one piston assembly beingaslidablyre ceived in fluid tight arrangement withnthe vend of the second piston assembly, a spring interposed between said.

tive piston being open to the respective cylinder, relief ports in each of said piston assemblies venting the interior thereof at a point infront of the respective pistons, a

relief valve for each of said piston assemblies, the movement of said rod in a given direction moving said pistons to close saidrelief valves and to increase the pressure in front of one piston, the increasing pressure in front of said one piston moving the associated one piston assembly ahead of said one piston in the given direction to increase the bias of said spring, said other piston assembly remaining stationary, the continued movement of said rod permitting the relief valve associated with the stationary piston assembly to relieve the high pressure through the relieved portions of said rod and the relief ports of the stationary piston assembly, valve means on each said piston assembly for controlling the flow of fluid from the front side to the back side of said piston assembly, said valve means being controlled by the movement of the associated piston assembly, the bias of said spring tending to return the moved piston assembly to its initial position and closing said associated valve means to increase the pressure of the fluid behind said one piston, the increase in pressure moving said pistons and rod an additional distance in the given direction the rod is initially moved.

8. A buffer mechanism comprising a housing including two aligned end cylinders containing a fluid, a cylindrical piston assembly reciprocable in each of said end cylinders, the end of one piston assembly being slidably received in fluid tight arrangement withlthe end of the second piston assembly, a spring interposed between both of said piston assemblies for biasing said assemblies toward the ends of their respective cylinders, a rod receivable Within said piston assemblies, said rod including relieved portions, a piston reciprocable in each of said piston assemblies fixed in spaced relation on said rod, the interior of each piston assembly in back of the respective piston being open to the respective cylinder, relief ports in each of said piston assemblies venting the interiors thereof, a relief valve for each of said piston assemblies, the movement of the rod in the one direction moving said pistons to close said relief valves and to increase the pressure in front of one piston, the increasing pressure in front of said one piston moving the associated one piston assembly ahead of said one piston in the one direction to increase the bias of said spring, the other said piston assembly remaining stationary, the continued movement of said rod permitting the relief valve associated With the stationary piston assembly to relieve the high pressure through the relieved portions of said rod and the relief ports of the stationary piston assembly, valve means including orifice means on each said piston assembly for controlling the flow of fluid from the front side to the back side of said piston assembly, said valve means being controlled by the movement of the associated piston assembly, the bias of said spring tending to return said moved one piston assembly to its initial position and closing the associated valve means thereon to increase the pressure of the fluid behind said one piston, the increase in pressure moving said pistons and rod an additional distance in the direction said rod is initially moved, said rod, pistons and moved piston assembly being returned to their initial positions as the resilient force on said biased spring is slowly released due to the flow of the high pressure fluid behind the one piston through said orifice means for said valve means of said moved one piston assembly.

9. A buffer mechanism comprising a housing including two aligned end cylinders containing a fluid, a cylindrical piston assembly reciprocable in each of said end cylin= ders, the end of one piston assembly being slidably received in fluid tight arrangement with the end of the second piston assembly, a spring interposed between both of said piston assemblies for biasing said assemblies toward the ends of their respective cylinders, a rod receivable within said piston assemblies, said rod including relieved portions, a piston reciprocable in each of said piston assemblies fixed in spaced relation on said rod, the interior of each piston assembly in back of the respective piston being open to the respective cylinder, relief ports in each of said piston assemblies venting the interiors thereof at a point in front of their associated piston, a first relief valve for said relief ports in each piston assembly, and a second relief valve coacting with each of said first relief valves, movement of said rod biasing the first and second valves associated with said one piston assembly to closed and opened positions respectively and permitting the first valve and the second valve associated with the other piston assembly to open and close respectively the movement of the rod in the one direction moving said pistons to increase the pressure in front of one piston, the increasing pressure in front of said one piston moving the associated piston assembly ahead of the piston in the one direction to bias said spring, the other piston assembly remaining stationary, the continued movement of said rod permitting the second valve associated with the stationary piston assembly to form a passage from the relieved portion of said rod 'to the relief port of the stationary piston assembly to relieve said increasing pressure, the bias of said spring tending to return the moved piston assembly to its initial position and closing the associated relief valve thereon to increase the pressure of the fluid behind said one piston, the increase in pressure moving said pistons and rod an additional distance in the direction the rod is initially moved, valve means including orifice means disposed between each of said piston assemblies and the associated cylinder for controlling fluid from the front to the back of said piston assembly, said valve means being controlled by the movement of the associated piston assembly, said'rod, said pistons and moved piston assembly returning to their initial positions by the slow release of the biased spring due to the flow of the high pressure fluid behind said one piston through said orifice means for said valve means of said moved piston assembly.

10. A buffer mechanism comprising a housing including two aligned end cylinders containing a fluid, a cylindrical piston assembly reciprocable in each of said end cylinders, the end of one piston assembly being slidably received in fluid tight arrangement with the end of the second piston assembly, a spring interposed between both toward the ends of their respective cylinders, a rod receivable Within said piston assemblies, said rod including relieved portions, a piston reciprocable in each of said piston assemblies fixed in spaced relation on said rod, the interior of each piston assembly in back of the respective piston being open to the respective cylinder, relief ports in each of said piston assemblies venting the interiors thereof at a point in front of the respective piston, a relief valve for each of said piston assemblies, means for moving each of said piston assemblies by their respective pistons in a given direction, one of said piston assemblies remaining stationary While the other said assembly is moving, a first relief valve for the relief ports spaced in front of each piston in each associated piston assembly, anda second relief valve coacting with each of said first relief valves, said rod being initially moved inone direction to move said pistons and said one piston assembly therewith, the second of said piston assemblies remaining stationary, the movement of said pistons biasing the first and second valves associated with the moved piston assembly to closed and opened positions respectively, and permitting the first valve and the second valve associated with the other piston assembly to open-and close respectively, the movement of the rod in the one direction moving said pistons-to increase the pressure in front of said one piston, the increasing pressure in front of said one piston moving the associated piston assembly ahead of the piston in said one direction to increase the bias of said spring, the continued movement of said rod aligning the relieved portion thereof with the first and second valves associated with the stationary piston assembly to relieve the high pressure through the relief port of the stationary piston assembly, the bias of said spring tending to return the moved piston assembly to its initial position and closing the associated relief valve thereon to increase the pressure of the fluid behind the first piston, the increase in pressure moving said pistons and rodan additional distance in the direction the rod is initially moved, valve means including orifice means on each said piston assembly controlling fluid flow from the front to the back of said piston assembly, said valve means controlled by the movement of the associated piston assembly, said rod, pistons and moved piston assembly returning to their initial positions bythe slow release of the biased spring due to the flow of-the high pressure fiuid behind said one pistonthrough said orifice provided for said valve means of said moved piston assembly.

ll. A buffer mechanism comprising a housing including two aligned end cylinders containing a fluid, a" cylindrical piston assembly reciprocable ineach of said end cylinders, the end of one piston assemblybeingsl-id ably received in fluid tight arrangement withthe endof" the second piston assembly, a spring interposed between and bearing against said piston assemblies for biasing said assemblies apart and toward the ends of their respective cylinders, a rodreceivable within said piston assemblies, said rod including relieved portions, a'piston reciprocable in each of said piston assemblies fixed in spaced relation on said rod, abutment means within each of said piston assemblies for engagement by their re-- spective pistons moving in a given direction for moving said piston assemblies in the given direction, relief ports controlled "by "the movement of I the associatedl piston as:- sembly, the bias of said spring tending to-retnrn the moved-piston assembly to its initial position thereby clos ing the associatedval-ve' means thereon to increase the." pressure of the fluid behind said one piston,- the: increase in pressure moving said pistons and rod an-ad'diti'onai distance in the direction the rod is initially moved, said rod, pistons and 'moved piston'assembly returning to their initial p'ositions by theslow release of the biased spring:

due to the flbw of the high pressure fluid behind said one piston through: said orifice means in said valve-means of -'sa'i'dmoved piston assembly:

12. A buffer mechanism comprising two intercom" nected cylinders containing afluid, a cylindrical piston assembly reeiprocable in-each-cylinder, said piston'ras semblies' being tele'scoped' in fluid tight arrangement; "reSilientmeans arranged to bias each of-"said piston assemblies to an initial position, a piston reciprocable-in each cylindrical piston assembly, said pistons being connected by rod'means and'beingm'ovable in unison;

saidi rod means including relieved portions, the interior *of'each ofsaid pistonassemblies one side of'the' respecin each of said piston assemblies venting the interiors I thereof at a point in front of the respective piston, a first relief valve for the relief ports in each piston assembly spaced in front of the respective pistons, and" a second relief valve coacting with each of said'first relief valves which when open permit the fluid in said cavity to flow in the space between said first relief'valves and the front of said pistons, said rod being initially movable in either direction to move said pistons, one of said pistons engaging the abutment means of its respective one piston assembly to move said one assembly therewith; the other piston assembly remaining stationary, the movement" of said one piston assembly biasing said spring;. the movement of'saidpistons biasing the first and second valves associated with the moved piston assembly to closed and opened positions respectively and. permitting the first valve and the second valve associated with the other piston assembly to open and close respectively, the movement of the rod inthe one direction moving said pistons to increase the pressure within'the cavity and within the spacein front of said one piston, the increasing pressure in front of said one piston moving the associated piston assembly ahead of the piston in said one direction to increase the bias of said spring, the continued movement of said rod aligning the relieved portion of said rod'withthe secondvalve associated with the stationary piston assembly to relieve thehigh pressure of the cavity through the relief ports of the stationary piston assembly, valve tive'ipiston being 1 open to"the'respective cylinder, said" piston: assemblies having a cavity located 'on the other side of the respective piston, each piston assembly hav ing a relief port interconnecting said cavity with said cylinders, first and second relief valves'on' eachof said piston assemblies controlled by the movement of there spective pistonsand piston assemblie's; the movement of said rod in" one direction moving said pistons and one of said piston assemblies" to' actuate said first relief valve of I one" piston assembly closing, said port, said secondrelief valve of th'e'secon'd piston assembly seal ing on apdrtio'n' of I said cavity in item of the 701161 piston,- the movement of said. pistons'inalgiven direction increasing] the fluid. pressurein front of said one. piston.

to move said associated one piston assembly'inith'e'samei direction additional increments of'the distance the'pis-' tons are moved to bias saidi'r'esillient means, the other.

of'said piston assemblies remaining. in an initial :position said pistons, and cooperating with said relieved'lportions on saidrod means to relieve the increased'pressure in front of said one piston to permit the associated "piston assembly to return to its initial position under theinfluence of saidbiased resilient means, valve means on each piston assembly controlling the flow of fluid in the space between each'piston assembly and the as- V sociated cylinder, the return-offsaidpiston assembly "effecting. olosureof said valve means thereon and causingthe pressure behind said one piston to increase thereby moving said piston an additional distance in the given direction it is initially moved.

References Cited in the file of this patent UNITED STATES PATENTS 2,098,831 McGowan Nov. 9; 1937" 254-1 7-1 8- Howe Feb; 15, 1944:"

2531;368- Tack-et al; Nov.- 21; 1'9'50 2,571,449 Hobbs Oct. 16, 1951 FOREIGN PATENTS 770,716 France Sept. 20,1934- 777,61-1 France Feb. 25, 1935- When said rodis -movedinsaid one direction, the first