CA1196227A - Self-steering railway truck - Google Patents

Abstract

Abstract of the Disclosure A railway truck having improved means for decoupling the wheel sets from the truck side frames to provide enhanced self-steering capability for the wheel sets and resultant improved tracking of the railway truck when traversing both curved and tangent track.

Description

~19~ `7 SELF- ~ NG RAILWAY TRUCX
BACRGROUND OF THE INVENTION

This invention concerns self-steering railway tsucks wherein the wheel sets are able to assume a radial orientation with respect to the center of curvature of a curved track section being traversed thereby.
Conventional three-piece railway truck designs comprised of a pair of laterally spaced side frames and a bolster extending transvessely therebetween have become the standard in many railway industry applications; however, in many conventional truck designs utilized in conjunction with conventional track layouts and wheel conics, the wheel sets may not track radially around curves bu~ instead may tend to sliae during negotation of track curves. Additional problems encountered ~ith conventional trucks include the tendency for the wheel sets to traverse curves in a non-radial orientation and with much wheel flange-to-rail rubbing contact. Such rubbing contact and wheel sliding result in undesirably high wheel and rail wear, and the 1ange rubbing in particular may produce a tendency for the wheel to climb the rail and cause a derailment. In addition, imprsper wheel set tracking in curves may result in track misalignment.
Other related problems occur ~hen con~entional t-ucks traverse straight or tangent runs of track. For example, a rigid wheel-axle set, having conventional tapered conical wheels, when displaced laterally of the center line Qf a run of ~tralgh~ track, executes t~o si=u1taneDus ~otiona fil~t, the ?
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wheel set moves toward its equilibrium (centered) position under the influence of gravity, and secondly, the high side wheel, rolling on a larger diam~ter than the low side wheel~
moves along the rail faster than its partner, causing the wheel se~ to yaw. Given the proper set of conditions, this motion may become a sustained harmonic oscillation known as hunting with the sinusoidal peaks being clipped by contact between the rail and the wheel flange.
When rigid wheel sets are coupled in a truck through the side frames, or rigid tr~ck frames, the hunting tendency is transmitted to the truck and causes an oscillatory yawing motion of the truck about its center of rotation. Continuous or semi-continuous motion of this nature is transmitted to the car body which then yaws about its cent2r of gravity, or about the center plate of its second truck if that truck is not hunting.
Railway rolling stock design has be~n evolving toward higher center of gravity cars, heavier loads and highe~
operating speeds, all of which have the potential to seriously aggravate the problems described hereinabove. These problems have been recognized in the prior art with the resultant development of a variety of self-steering railway truck designs which purport to allow the wheel sets to track without sliding and without undue flange rub~ing during negotiation of curves, and with minimal adverse consequence~ resulting fro~ hunting.
A summary of several such prior art arrangements is described and illustrated in a November, 1978, Report No. 5576-78l which was issued by the Departmen~ of Research-Canadian Paci~ic !

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Limited. Cumulative and/or additional examples of ~ome prio~
art which may be germane to self-steering arrangements ~re described and illustrated in U.S. Patent Nos. 4,202,276;
4,173,~33j 4,170,1~9; ~,166,611; 4,151,801; ~,136,6207 4,134,343; 4,06q,809; 3,94~,18~; 3,52~,374; 3,517,520; ;

3,25~610; 2,956,515; 2,908,233; 2,7S6,688; 2~792,791; ~nd 2,207,848.
A review of the art in above non-exhaustive listing reveals that considerable prior work has been done in the area of self-steering railway trucks; nevertheless, there has been no overwhelming commercial acceptance of any self-steering railway tru~ks heretofore even though a significant need exists in the industry. The apparent reason~ for industry non-acceptance of prior self-steering trucks include theis relatively complex designs with resultant operational and maintenance problems; inherent requirements for substantially new truck designs; the inability to readily retrofit and/or to conform to inherent space limitations; and limitations in designs which provide for steering but whish, in turn, ~mplify the tendency of the railway car to hunt in unloaded conditions on straight track to an unacceptable d~gree or to a degree that control thereof is uneconomical or unfeasible.

SUMMARY OF T~E INVENTIO~

The present invention includes in a self-steeing railway truck a suspension system which frees the axles fo~

steering around curves by isolating the side frames fro~ the wheel sets by means of a pendulous swing link arrangement whicb suspends the side frames of the truck from the wheel sets. By virtue of this arrangement the hereinabove described problems of prior art trucks are overcome or, in the least, gr~tly alleviated. More specifically, the pendulous swing lin~
arrangement of the present invention permits limited move~e~t of an inherently self-steering wheel set with respect to tbe side frames in both the direction of the longitudinal e~tent o the side frame and laterally thereo~ in the direction o~ the wheel set axis. Thuss the wheel sets have two degrees ~f freedom with respect to the side frames and are able to s~er through track curves in the optimal radial orientati~n.
Furthermore, the longitudinal and lateral ~ournal freedom of this invention, which is necessary to permit ~heel set steering, is accomplished with extremely low levels o mechanical restraint provided by the primary elements of th~
suspension system.
In a truck constructed according to this invention a6 p6N~61`~
iw~pe*~e~ wheel set hunting may still occur because of the increased longitudinal and lateral freedom of the individual wheel sets; however, the invention provides~rsuf~icient lateral freedom to inherently reduce the lateral car body t~
wheel set coupling.
It is to be noted that although one of the principal uses for the~invention herein is in three-piece freight truck '~
designs, the ~ ~c~ti~is equally applicable to provide for simple and economical self-steering of wheel sets in other types of truck designs such as in transit trucks whesein the truck side ~rames ma~- ~e lnboard of the wheel. sets and which may or may not have conventional. truck bols~ers f.or supporting -the car body.
Broadl~ spea.iing, therefore, the present invention provides a rail~ay truck comprisin~ a pair of laterally spaced, elon~ated side frame members having opposed openings therein in-termedia~e the lenqth thereof, respectively; a-t least one el.ongal:ed rotatable axle extending transversely between the s.ide frame mernbers with the ends thereof being received at least in par-t within the openin~s, respectively; rotatable wheels carried by the axle adjacent the ends thereof laterally inward of the side frame members, respectively; the axle havinq axially spaced and circumferentially extending bearing areas located outwardly adjacent the wheels and the openings, respectively; side frame support members engageable by upwardly facing portions of the bearing areas, respec-tively, for continuous support thereof; each of the side frame support members carryina longitudinally spaced upper support means;
the upper support means including upwardly facing engagement surface portions which are fixedly located with respect to the side frame support members, respectlvely, generally ou-t-ward].y in longitudinally opposite directions with respect to a vertical plane passinq throuah the axis of rotation of the axle; each of the side frame members carrying longitudi.nally spaced lower support means; the lower support means .including downwardly -Eacing enga~emen-t surface portions which are fixedly located wLth respect to the side frame members, respectively, outwardly in opposite directions with respect to such a vertical plane; the downwardly facing engagement ~dJ~ -5-~ tj ZZ7 surface portions ~e.inq spaced a ~reater longltud.inal distance from such ~ertlcal plane than the respective upwardly fac.ing engagement surface portions to ~rovide a pair of longitudinal]y o.fset upper and lower en~agement surface portions on each side of such ver-tical plane adjacent each end of the axle;
and rigid connecting means having fixedly spaced apart, oppositely facing surfaces theret~n which are engageable with respec-tive ~airs of upper and lower engagement surface portions to connect the upper and l.ower support means, respectively, in a manner to permit simultaneous rela-tive lateral and longitudinal movement of the members in response to the relative lateral and longitudinal movement of the wheels and the axle with respec-t to the side frame members while main-iainin~ continuous engagement with the upper and lower engage-ment surface portions.
These and other features and advan-tages of the present invention will become more readily apparen-t upon a reading of the followin~ description with references to the accompanying drawings, in which:

sd/~ -5A-~7 Fig. 1 is a side elevation of a portion of a three-piece railway truck incorporating one emobidment of the present invention;
Fig. 2 is an end elevation taken on lines 2-2 and pa,rtially in section, of the truck of Fig. l s Fig. 3 is a top plan view taken on lines 3-3 of Fig. l;
Fig. 4 is a side elevation of a portion of a three-piece railway truck incorporating another embodiment o~
the present inventi~n;
Fig. 5 is a plan vi~w taken on lines 5-5 and partially in section, of the truck of Fig. 4 and Fig. 6 is 3n end elevation taken on lines ~ 6 of Fig.

4.
Figs. 1, 2 and 3 illustrate a journal-pedestal portion of a four-wheel railway truck constructed in accordance with the principles of the present invention and generally indicated at 10. Truck 10 comprises a laterally spaced pair of side frames 12 ~only a portion of one being shown) in which respective spring groups 14 are included intermediate the longitudinal ends thereof to support a bolster 16. Adjacent each end of side frames 12 is a wheel set comprising conic wheels 18 which are suitably jornaled to live axles 20. The wheel sets are carried by side frames 12 through the use of known roller bearing assemb~ies 22 which cooperate with a suspension means 24 of the prsent invention to support side frames 12 with respect to a~les 20 in a manner to be described hereinafter in detail which permits limited movement of axles 20 with resp~ct to the side rame~ 12.

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Inasmuch as the invention herein is primarily directed to suspension means 24, the other hereinabove described primary elements being well known in the art, further description of such other elements not believed necessary except insofar as may be otherwise nPcessary to describe the invention herein.
In Fig. 1 one end of side frame 12 is formed as a pedestal portion 26 which defines a downwardly open pedestal opening 28. Pedestal opening ZB is ~ormed by: a vertically disposed, longitudinally outward pedestal jaw portion 30 having an inner peripheral surface 32, a pedestal roof portion 34; and a vertically disposed longitudinally inward pedestal ~aw portion 36 having an inner peripheral surface 38.
A conventional roller bearing as~embly 22 is carried adjacent each journal end ~f axles 20 and is retained within the confines of pedestal opening 2B in a manner to be described hereinbelow. Bearing assemblies 22 are secured by any suitable means as by a press fit for e~ample on the journal end of axle 20. Each bearing assembly 22 is a sealed unit which includes a cylindrical roller bearing journalon a carsier 40 that coaxially receives therewithin an inner cone and rollers (not shown~. Bearing assemblies 22 are retained on axles 20 by axle end caps 44 secured with a plurality o cap screws 46.
Suspension means 24 comprises: a bearing adapter S0 position intermediate the pedestal roof 34 and the adjacent portion of bearing carrier 40; a retention member formed as a plate 52 which extends between the lowermost ends of pedestal jaw portions 30 and 36; and inward and outward swing link members 54 and 56, respectl~ely, which engage and e~tend !
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_7_ between generally vertically spaced retainer portions of bearing adapter 50 and member 52 as described hereinbelow.
Bearing adapter 50 comprises a main body portio~ S8 which is of a generally kno~n design for bearing adapt~rs and in~cludes a downwardly, cylindrically concave surface 6~ ~hich seats upon an adjacent upwardly ~acing cylindrical surface of roller bearing journal 40 in the conventional manner. In the assembled configuration upper surface 64 of bearing adaptor main body portion 5B i5 spaced from the pedestal roof 34O
Additionall, a longitudinal clearance is provided between the longitudinal ends of main body portion 58 and the respective adjacent pedestal jaw surfaces 32 and 3B. In the embodiment of Fig. 1 such longitudinal clearance is necessary to provide for the longitudinal component of a~le movement associated with the self-steering characteristics of the wheel sets.
As in known truck structures, side frames 12 are hollow. This feature is utilized in the embodiment of FigO ~-3 by disposing substantial portions of suspension means 24 including link members 56 and 56 within the interior o~
pedestal jaw portion 36, 30. Specifically, an opening is formed in walls 32, 38 of pedestal jaw portions 30 and 36 to re~eive respective lug portions 60 formed adjacent the ~pposite longitudinal ends of bearing adaptor main body portion 58 such that in the assembled conEiguration lug portions 60 project into the interior oE the respective pedestal jaw portions 30 and 36. ~inks 54 and 56 are formed as double ended eye bar~
and are located such that the top eye openings 66 thereof ar~
seated on the respective lug portions 60 adjacent thereto~ A~

~8 shown, the links 54 and 56 extend downwardly ~nd diverge outwardly with respect to the vertical axial plane o~ axle 20~
and the lower eye openings ~4 thereof are captively retained in cooperably formed seating portions 76 adjacent the resp~ctiv~
longitudinal ends of retention member 52~
The lug portions 60 may be of any suitable configuration which will receive and captively seat the eye openings 66 in a manner that the links 54 and 56 are supported thereby with suitable contact geometry to permit links 54, 56 to swing in both the longitudinal and transverse directions.
As illustrated, each lug portion 60 includes gensrally upwardly concave upper surface 70 which, in conjunction wiith the mating, downwardly facing surface 72 of eye opening 66, provides the requisite longitudinal and transverse freedom.
Preferably, surface 70 presents a compound curvature whi~h is upwardly concave in its longitudinal extent and upwardly convex in its lateral or transverse extent. The cooperably formed seating surface of eye opening 66 presents a similar convex configuration in the longitudinal and lateral directions.
Accordingly, each swing link 54, 56 is provid~d with two degrees of freedom for swinging motion both longitudinally of side frames 12 and laterally thereof or axially with respect to axles 20.
The elongated retention member 52 extends longitudinally between the lower ends of pedestal jaws 30, and the respective longitudinal end portions thereof are affix~d to the respective lowermost surfaces of jaws 30 and 36 in any suitable manner, for example by bolts ~not shown). In the , _ g _ 3~

assembled configuaration the lower eye openings 74 of links 54, 56 are seated in the formed seating portins 76 of member 52 ln a manner that the links 54 and 56 support member 52 and ~ide frame 12. Each seating portion 76 presents a dGwnward~y concave lower seating surface 78 which, in conjunction witb a cooperably formed upwardly facing surface portion 80 of ~ye opneing74, provides suitable contact geometry for the requisite longitudinal and transverse freedom. The lower end retention of links 54, 67 by seating portions 76 preferably is provided by cooperable surfaces of compound curvature similar in all salient respects to the surfaces pro~ided for eng~gement of eye openings 66 with lugs 60 as described hereinabove with respect to the retention of the upper ends of links 54, 56.
Accordingly, rolling contact is achieved at all points of engagement or each of the links 54 and 56 provides two degrees of freedom for small ~winging motion both longitudinally and laterally with respect to side frames 12 in much the ~ame manner as the connections bet~een adjacent links in a link chain.
To facilitate assembly of the suspension means ~4 a lower po~tion of the longitudinal end of the side frame 12 includes a vertically extending slot 82 formed therewitbin.
Slot 82 permits the insertion of the eye openings 74 over the respective seating portions 76 prior to securing retenti~n member 52 to pedestal jaws 30 and 36.
The inclusion o~ suspension means 24 as described for each pedestal opening 28 prGvides a structure which permits suficient lateral and longitudinal freedom of movement or - 10 ~

each axle 20 to permit the a~les 20 to track through ~urves on the optimum radial line positiOnA Thus the wheel sets, which are inherently self-steering, track through the curve~ w~th minimal sliding and flange contact as compared t9 prior~art truck designs having journals which are relatively rigldly engaged in the side frame pedestals.
As will be seen from Fig. 1, the side frame 12 is suspended at each end therecf from bearing adaptor 50 by a pair of links 54, 56 such that axles 20 are provided with two desrees of freedom for motion in a generally hor~zontal plane with respe~t to side frames 12. Accordinglyv the side frames 12, bolster 16 and the car body carried thereby are 211 isolated or decoupled from the wheel sets whereby th~
mechanical restraint which ~ould otherwise ten~ to impede self-steering of the wheel sets is minimized. If a longitudinally directed force couple is applied to side frame 12 and an axle 20, the axIe 20 would move freely ~ithin predetermined limit~ with respect to side frame 12 by virt~e of the link members 54 and 56 pivoting or swinging generally in a longitudinally extending vertical plane about the respective lug portions 60 and 76 in a manner that the lower ends of link members 54 and 56 would move longitudinally through an arc ~ith respect to axle 20. A similar force couple applied in the lateral direction will permit a similar limited pivoting or swinging of links 54, 56 for movement of the side frame 12 with respect to the axles 20 in the transverse direction. The freedom of movement in the transverse direction acts in ser~e~
with the lateral stiffness of the spring group 14 to reduce the - , lateral restraint of coupling between the car body and wheel sets. Th~s, within predetermined limits~ the side fram~s 12 are isolated and free to move with respect to the axles 20 ~nd the wheel sets are free to respond to their inherent self-steering charàcteristics to the extent that the a~les 20 are decoupled from the side frames by suspension means 24.
That is, the isolation of the axles 20 with respect to the side frames 12 will permit the self-steering wheel sets to adapt to the layout of the track by moving laterally of the track to roll on the optimum radius of ea~h wheel 18, thus permitting axles 20 to assume a radial line when tracking through curves.
~he wheel sets therefore steer around curves with minimal tendency for sliding or breaking friction. In addition, the reduced car body to wheel se~ restraint, in combination with the shorter kinematic path of the independent wheel sets, can result in a higher frequency wheel set forcing input to a lower frequency car body to wheel se~ resonance thereby alleviating empty car hunting on tangent track over a higher useful speed range for freight ~arsO
An additional featura of the invention is that link members 54, 56 diverge downwardly and outwardly from the upp~r ~nds thereof to apply a gravitational centering bias whereby when the truck 10 leaves a curved section of trac~ the wheel-rail cooperation urges the a~les ~0 toward a normal square alignment. The angle of divergence of links is ~4, 56 is determined by a variety of factors ~i.e., availabl~
clearances, retrofit~or new side frame design, and the like);
however, a preferable angle of each link with respect to a .

vertical plane is in the range of 10 to 50 degrees. ~h~
described centering bias is operative in both the transvers~
and longitudinal directions in that the swinging movements of links 54, 56 associated with all horizontal relative m~ion b~tween side frames 1~ and the wheel sets cause the side frame6 12 to be lifted vertically with respect to the wheel sets. m e gravitutional tendency to seek the lo~est stable point o' suspension accounts for the centering bias.
The invention herein p2rmits ~he ~heel sets of a railway truck to steer independently of each other. This independence, and tbe freedom of axles 20 to move, within predetermined limits, with respect to the side frames 12, may increase the propensity for hunting responses between the side frames 12 and axles 20 in certain circumstances. Such hunting responses may still occur in trucks with the suspension means 24 in spite of the reduction in lateral restraint discussed hereinabove, depending on the particular structural and geometric limits to which the transverse a~le freedom is reduced. In instan~es where track and operating conditions may result in hunting when utilizing the suspension means of the present invention, other design features may be included to alleviate resultant hunting responses. Examples of such other features may include: the alternative embodiment of suspension means 90 of this invention (see Figs. 4-6); elastomeric mean disposed intermediate plate 52 and the adjacent portion of pedestal ~aws 30 and 36; and the like.
Referring now to Figs. 4-6, suspension means 90 i~
quite similar to suspension means 24 descr~bed hereinbeo~e , ; -13- , ~L~ 9~

with the primary distinction therebPtween being that means 90 is configured to be operational with a truck 10' of the type having a bolster 16' rigidly diRposed with respect to side frames 12' with the suspension means therefor being lo~ated in t~e vicinity of the pedestal opening 28'. Because of the similarity between suspension means 90 and 24, elements of the embodiment of Figs. 4-6 which are virtually identical to thos~
of the embodiment of FigsO 1-3 will be identified with identical reference numerals and elements which are sim~lar will be identified with identical reference numerals primed.
Furthermore, a detailed description of such identical and similar elements of the Figs. 4-6 embodiment will not be set forth hereinbelow except as necessary to fully describe dthe suspension means 90. Such detailed description may be found in the description hereinabove with reference to Figs~ 1-3.
In Figs. 4-6, side frmes 12' of truck 10' include enlarged transversely projecting outward and inward pedesal jaws 92 and 94, respectively, each of which has defined therewithin a downwardly open cavity or pocket 96. the suspension means 90 includes a bearing adapter 50; and a pair of swing links 54 and 56, respectively, which diverge downwardly within pockets 96 from the respective lug portions 60 of bearing adaptor 50 to engage individual retention members 98. ~he lower eye openings 74 of links 54, 56 are eaptively and pivotally retained by a central seating portion 100 of the respective retention member 98. Seating portion 100 includes a downwardly concave lower surface 102 which engages a cooperably formed upwardly facing surface portion 80 of eye opening 74 to .

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provide the requisite longitudinaI and transverse freedo~ of motion for the axles 20 with respect to side frames 12'~ m e specific geometry of the interengagement of links 54, 56 with lugs 60 and with seating portions 100 is similar in al~
r~spects to that described hereinabove with reference ~o Figs. 1-3 and the resultant swinging capability of links 54, 56 including all perceived benefits and advantages thereof is likewise similar in all respects. Accordingly, further detailed description of such structure and its advantages is not repeated here.
Truck 10' is provided with plural coil springs 104 at each longitudinal end of each side frame 12~o A pair o~
springs 104 is disposed within each pocket 96 laterally to either side of a respective one of links 54, 56. Springs lD4 extend generally vertically intermediate the ~pper end of the respective pocket 96, where they engage side frame 12' in supporting engagement, and a retention memb~r 98. Accordingly, springs 104 provide the primary spring suspension for truck 10' by supporting side frames 12' with respect to retention members 98. In order to assure the retention of springs 104 within pockets 96 and proper operation thereof within pockets 96, each retention member 98 includes a generally tubular spring guide portion 106 which extends upwardly ~o encompass and retain the lower end of the respective spring 1040 Accordingly, the lower end portion of each spring 104 is received within a respective guiding portion 106 for the captive and guiding retentio~
thereof within the pocket 960 Suspension means 90 is assembled by fir9t positioning and holding bearing adapter 50 in the side ~9t~ 9~ ' frame pedestal opening 28' and hanging link members 54 and 56 o~er the respective lug portions 60. Thereafter the lower ey~
openings 74 are secured to the respective central seat~ng portions 100 of retention members 98 and the suspensio~ means 9~ along with springs 104 and the side frame 12' is lowered as a unit onto the journals of the wheel sets.
Suspension means 90 operates in much the same manner as suspension means 24 as described hereinabove. The primary distinction therebetween is that ~he springs 104 and spring guiding portions 106 cooperate to provide a vertical suspension damping as a result of an inward bias exerted by link members 54 and 56 on the guiding portions 106 which in turn results in friction contact between guide portions 105 and the adjacent interior wall of the respective pockets 96 when the springs 104 extend or compress.
The bearing adapter 50 thus has the same longitudinal and transverse freedom with respect to the side frame 12' as in the embodiment first described hereinabove; however, it i~ to be noted that in the latter described embodiment a lateral space is shown betwe~n members 98 and guiding portions 106 thereof with respect to adjacent peripheral portions of tbe pocket 96 to accommodate side frame-to-journal lateral motion resulting from lateral spring deflection. Such lateral spriDg motion is in addition to the lateral pendulous swing o~ the supporting links 54 and 56.
The embodiments described hereinabove are the presently preferred embodiments of the invention hereln;
however, it is to be understood that various modifications may j be made thereto by those skilled in the art without departing from the scope of the invention which is defined by the Claim~
set forth hereinafter. For example; springs 104 may be replaced or complemented by one or more hydraulic snubbers, if dejsired; the side frames may be modified by enlarging the pedestal opening such that the link members 54 and 56 are not received within the interior of the æide frame; ~arious attachments may be utilized in place of the link members 54 and ~6 and supporting structure therefor so long as the pendulous support as described hereinabove is provided between tbe side frames 12 and axles '0; the concept of the invention is equally applicable for truck designs other than three piece freight truck designs, for example, transit trucks wherein the side frames may be inboard of the wheel sets and which may o~ may r,ot have conventional truck bolsters for supporting th~ car body; and the like. A further modification which may be utilized in instances where a simple retrofit to existing side frames is desired could include the utilization of a transversely spaced pair of link members on each side of each journal adapter with the lower ends of each such link member being pivotally connected to a retention ~ember extending across the pedestal opening adjacent the lower end thereof.
The top end of each such link member would be pivotally connected to respective bearing adapter means therefor. Such alternative suspension means would operate substantially identically to suspension means 24; however, the only needed modification to the side frames would be adjacen~ the lower end ' ~ -17-1. .~, .
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of the pedestal opening and side frame modification would therefor be sig~ificantly simplifiedO
These and other embodiments and modifications having been envisioned and anticipated by the inventor; the inventlon should be construed as broadly as permitted by the sco~e of the claims appended hereto.

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Claims (13)

THE EMBODIMENTS OF THE INVENTION IN WHIC AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A railway truck comprising: a pair of laterally spaced, elongated side frame members having opposed openings therein intermediate the length thereof, respectively; at least one elongated rotatable axle extending transversely between said side frame members with the ends thereof being received at least in part within said opening, respectively; rotatable wheels carried by said axle adjacent the ends thereof laterally inward of said frame members, respectively; said axle having axially spaced and circumferentially extending bearing areas located outwardly adjacent said wheels and said openings, respectively; side frame support members engagable by upwardly facing portions of said bearing areas, respectively, for con-tinuous support thereof; each of said frame support members carrying longitudinally spaced upper support means; said upper support means including upwardly facing engagement surface portions which are fixedly located with respect to said side frame support members, respectively, generally outwardly in longitudinally opposite directions with respect to a vertical plane passing through the axis of rotation of said axle; each of said side frame members carrying longitudinally spaced lower support means; said lower support means including downwardly facing engagement surface portions which are fixedly located with respect to said side frame members, respectively, outwardly in opposite directions with respect to such a vertical plane;
said downwardly facing engagement surface portions being spaced a greater longitudinal distance from such vertical plane than the respective said upwardly facing engagement surface portions to Claim 1 cont'd:

provide a pair of longitudinally offset upper and lower engagement surface portions on each side of such vertical plane adjacent each end of said axle, and rigid connecting means having fixedly spaced apart, oppositely facing surfaces thereon which are engageable with respective said pairs of upper and lower engage-ment, surface portions to connect said upper and lower support means, respectively, in a manner to permit simultaneous relative lateral and longitudinal movement of said members in response to the relative lateral and longitudinal movement of said wheels and said axle with respect to said side frame members while maintaining continuous engagement with said upper and lower engagement surface portions.

2. A railway truck as specified in claim 1 wherein said upper and lower support means are integral with said side frame support members and said side frame members, respectively.

3. A railway truck as specified in claim 1 wherein said upwardly facing engagement surface portions are located above a horizontal plane passing through such of rotation and said downwardly facing engagement surface portions are located below such horizontal plane.

4. A railway truck as specified in claim 1 wherein each said rigid connecting means includes plural rigid connecting members and each said pair of upper and lower engagement surface portions is engageable by a single said rigid connecting member.

5. A railway truck as specified in claim 1 wherein each said rigd connecting means includes an elongated link member which engages a respective said pair of upper and lower engagement surface portions and diverges downwardly with respect to such a vertical plane.

6. A railway truck as specified in claim 5 wherein said link members diverge downwardly from such a vertical plane at substantially equal angles of divergence.

7. A railway truck as specified in claim 1 wherein said upwardly facing and said downwardly facing engagement surface portions are generally curvilinear surfaces.

8. railway truck as specified in claim 1 wherein said upwardly facing engagement surface portions are maintained generally equidistant from such a vertical plane, and the respective said downwardly facing engagement surface portions are maintained generally equidistant from such a vertical plane.

9 . A railway truck as specified in claim 1 wherein said rigid connecting means includes a plurality of rigid link members for engagement with each said pair of upper and lower engagement surface portions.

10. The railway truck as specified in claim 1 wherein each of said side frame members includes a pair of said openings spaced longitudinally thereof and said at least one axle is a pair of axles, each having the ends thereof received at least in part within said openings, respectively, in each said side frame member.

11. The railway truck as specified in claim 1 wherein said slideable support of said side frame support members by said bearing areas is support thereof for rotation within pre-determined circumferential limits about the axis of rotation of said axle.

12. A railway truck as specified in claim 1 wherein said relative lateral and longitudinal movement is sufficient to accommodate self steering by said railway truck.

13. A railway truck as specified in claim 5 wherein said link members diverge, with respect to such vertical plane, at an angle of 10 to 50 degrees.