CA2070975A1 - Pivot connection for single braced truck - Google Patents

Abstract

Abstract A truck for a rail vehicle has a pair of sideframes supported on axles. Each wheelset is pivoted to one of the sideframes and is connected to the other sideframe to allow relative longitudinal movement between the sideframe and wheelset. To inhibit lozenging of the sideframes, a diagonal brace extends between the sideframes and is aligned with the axis of pivotal movement of the axle relative to the sideframe.

Description

207~975 PIVOT CONNECTION FOR SINGL~L~E8-s ~

The present invention relates to a truck for a rail vehicle.
In USP 4,285,280, a steerable truc~ is described in which the axles may be steered to radial positions by a connection between the vehicle body and the truck. The axles support the truck sideframes and are connected to them through pivotal axle boxes. One bearing assembly of each axle pivots about at least a fixed vertical axis. The other bearing assembly of the axle swivels about a vertical axis within a carrier which is pivoted about a parallel vertical axis by the steering links for movement relative to the sideframe. In this way, each of the axles may assume a radial position in a curve.
With the arrangement shown in USP 4,285,280, relative sliding movement between the components is avoided as the connections between the relatively movable components are made as pivotal ConnQctions. These connections are sub;ected to vertical and bending loads as well as torque loads and therefore must be robust.
To accomodate the loads imposed on the truck during normal service, it is desirable that the truck be flexible 80 that upward movement of one wheel will not cause another wheel to leave the track. This is known as torsional flexibility. Conventional trucks exhibit this fl~xibility through utilizing a three-piece design comprising a pair of sideframes and a spring mounted transom. With such designs, however, the flexibility leads to dynamic instabilities due to lozenging of the sideframes in use, particularly during curving, and so this arrangement is mainly used on low speed, non-steered trucks.
With the arrangement shown in USP 4,285,280 there is a need not only to provide a torsional flexibility for the frame but also some degree to lateral 20~97~

flexibility to permit the movement of the carrier during steering action. While the arrangement shown in this earlier patent achieves very desirable characteristics for a truck, it is desirable nevertheless to improve the inherent stability of the truck.
USP 4,570,544 disclose~ a three-piece truck in which the stability is improved by utilizing a pair of diagonal braces between the ~ideframes to increase the shear stiffness of the truck frame. At the same time, the out-of-phase yaw stiffness between the axles is reduced by utilizing elastomeric pads between the sideframes and wheelsets. This arrangement leads to a considerable increase in stability over the prior art.
However, the pair of diagonal braces results in an increased weight and mechanical complication. Moreover, the pair of braces prohibits the use of this arrangement with steerable trucks of the type referred to above.
It is therefore an object of the present invention to obviate or mitigate the above dicadvantages.
According to the present invention, there is provided a rail truck comprising a truck frame supported by a pair of longitudinally spaced wheelsets each rotatable about a transverse horizontal axis, said frame including a pair of spaced parallel sideframes supported at opposite ends by said wheelsets and a brace member extending diagonally between opposite ends of each of said sideframes and connected thereto ad~acent respective on~ of said wheelsets, said frame being connected to each of said wheelsets by a pivotal connection acting between said wheelset and one of said sideframes and by a second connection acting between said wheelset and the other of said sideframes to permit longitudinal displacement of said wheelset relative to said other sideframe to facilitate motion of said wheelset relative to said frame about said pivotal connection, said pivotal connection being located adjacent the connection of said brace member to said sideframe.

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By providing a brace that is inclined to the longitudinal axis, lozenging of the sideframe is reduced without increasing the lateral stiffness of the truck.
It is preferred that the longitudinal axis of the strut is aligned with the pivotal connections of each wheelset to the sideframes. This allows the frame to be effective as a lozenging restraint without depending upon or influencing the lateral stiffness of the connection between the sideframe and the opposite end of the wheelset~ The opposite end of the wheelset is thus able to accomodate a lateral displacement of the sideframes for steering action. Moreover, the alignment between the brace and pivot connection avoids bending loads being imposed on the sideframes.
Embodiments of the invention will now be described with reference to the accompanying drawings, in which Figure 1 is a plan view of a steerable truck:
Figure 2 is a view on the line 2-2 of Figure l;
Figure 3 is a view on the line 3-3 of Figure 2;
Figure 4 is a view on the line 4-4 of Figure 2;
Figure 5 is a detailed view of a component used in the truck of Figure l;
Figure 6 is a plan view of a furthex embodiment of truck;
Figure 7 is a side view of the truck shown in Figure 6; and Figure 8 is a view on the line 8-8 of Figure 6.
As shown in Figure 1, a truck lO includes a frame ll having a pair of sideframes 12 and a bolster 14 extending between the sideframes to support a vehicle body 15. Bolster 14 c~rries a slewing ring 16 to connect the body 15 to the bolster 14. Bolster 14 is supported in the sideframes 12 on springs 18 to provide a suspension for the body relative to the truck.
Sideframes 12 are supported at opposite ends by wheelsets 20,22 each of which includes an axle 24 and a 2~7~97~

pair of wheels 26. Each of the axles 24 is rotatably supported in a pair of bearing assemblies 28,30 located between the axle and a respective one of the sideframes 12. Bearing assembly 28 is pivotally connected to the sideframe 12 through a fixed pivotal connection indicated at 32. Bearing assembly 30 is pivotally connected at 37 to a carrier 34 which in turn is pivotally supported at 3s for movement about a vertical axis relative to the sideframe 12. The carrier 34 may pivot relative to the sideframe 12 about pivot 35 to cause a longitudinal displacement of the axle 24 so that it pivots about the pivotal bearing 32. In this way, the axles may attain a radial disposition relative to the curve around which the truck may pass.
Each of the carriers 34 is connected to the vehicle body by steering links 36 extending from steering arms 38 associated with each of the carriers 34. Thus, upon rotation of the body 15 relative to the bolster 14, steering links 36 move the carriers 34 about their pivotal connections 35 with the sideframes 12 to attain steering of the axles.
In the arrangement of truck shown in Figure 1, one end of each axle 20,22 is fixed to a respective sideframe 12 to pivot about the fixed vertical axis 32, and the opposite end is longitudinally displaceable relative to th~ sideframe as indicated by the arrow "S".
The fixed vertical pivots 32 are located at diagonally opposite locations so that each wheelset is moved longitudinally in the same direction on opposite sides of the truck to achieve steering. As such, the configuration of the bearing assemblies 28,30 associated with each of the wheelsets 20,22 is similar but certain changes are made between the outboard and inboard wheelsets to achieve the desirable steering action. The outboard wheelset is shown in Figure 3 and the inboard wheelset is illustrated in Figure 4.

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Referring therefore to Figure 3, the bearing assembly 30 provides for relative longitudinal displacement between the sideframe 12 and wheelset and includes a pair of tapered roller bearings 60 located in s a bering housing 62 to allow rotation of the axle 24 about a transverse horizontal axis. Bearing housing 62 is located in a carrier 34 by upper and lower pivots 66,68 that define the pivot 37. As best seen in Figure 2, the carrier 34 is formed as a C-shaped yoke that extends around the bearing housing 62 and terminates in upper and lower bosses 70,72 to receive the upper and lower pivots 66,68. The opposite ends of the carrier 34 also extend laterally inwardly to provide bosses 73,74 that are offset to one side of the upper and lower pivots 66,68. The bosses 73,74 each receive a bearing 76,78 that constitute the pivot 35 and connect the carrier 34 with the sideframe 12.
The sideframe 12 includes a boss 80 that projects laterally inwardly and is received within the boss 73. Similarly, the lower portion of sideframe 12 includes a forward extension 82 that i8 bolted to the underside of the sideframe 12 and includes an ear 84 that extends laterally inwardly toward the opposite sideframe 12. Ear 84 has a central bore 86 that receives a pin 88 that also extends through the pivot 78 in boss 74.
Th~ pivots 66,76 are each formed with a pair of oppo~ed part-~pherical surfaces 90,92 with elastomeric laminations 94 interpoced between the surfaces. The part-spherical surfaces 90,92 permit the elastomeric lamination 94 to provide vertical, longitudinal and lateral stiffness while permitting relative rotation between the surfaces 90,92 about a vertical axis.
The lower pivot 74 is formed from an elastomeric bush 96 having inner and outer sleeves 98,100 which are received on the pin 88 and in the bore 74 respectively. The bush 96 has a uniform radial stiffness 207~.~7.~

about its circumference and allows relative xotation ~etween the extension 82 and the carrier 34.
The pivot 68 is located between a pin 102 secured to the housing 60 and a bore 104 formed in the carrier 34. An elastomeric bushing 106 is located between the pin 102 and the bore 104 and exhibits a lower lateral stiffness than longitudinal stif~ness. The form of the bushing is best seen in Figure 5 and has an outer sleeve 108 and an inner sleeve llo for engagement with the bore and pin respectively. An elastomeric web 112 separates the sleeves 108,110 but does not extend uniformly about the circumference of the sleeve 110. It will be noted that voids 114 are formed at diametrically opposed locations so that the radial stiffness over the portion f the circumference denoted by the arc A is significantly greater than that over the portion denoted by the arc B. With the bushing installed and the web 112 orientated in the longitudinal direction, longitudinal loads between the steering lever and the sideframe will tend to place on one of the webs in compression and the other in tension. ~owever, lateral loads will tend to place the web 112 in shear and so a differential stiffness is obtained. It is preferred that the lateral stiffness should be as low as po~sible and in practical terms can be between 10% and 20% of the longitudinal stiffness.
The bearing assembly 28 is of significantly simpler construction than bearing assembly 30 and includes a pair of tapered roller bearings 114 located within a housing llfi. The sideframe 12 includes a casting 118 that has a central cavity 120 to receive a pivot 122. The pivot 112 is similar in construction to the pivot 66 having elastomeric laminations 124 located between opposed part-spherical surfaces 126,128. The laminations 124 thus are able to accomodate vertical, lateral and longitudinal loads while allowing pivotal movement between the opposed surfaces 126,128. The 207~75 bearing housing 116 is located at its lower end on an extension 130 bolted to the sideframe 12. A pivot 132 similar in configuration to the pivot 74 having an elastomeric bushing 134 secures the housing 116 to the extension 130. The axle 24 may thus pivot about a vertical axis relative to the sideframe 12 by virtue of the pivots 122,132 to allow steering motion of the wheelæet 20 xelative to the sideframes 12.
The inboard wheelset shown in Figure 4 is similar in construction to the outboard wheelset shown in Figure 3 and therefore like reference numerals will be used to denote like parts with the suffix "a" added for clarity. In view of the similarity of the constructions, a detailed explanation of the wheelset will not be given except to note that the boss 80a extends laterally outwardly from the sideframe 12 so that the pivot 76a is laterally outboard of the pivot 66a. Similarly, the extension 82a is located laterally outwardly of the bearing assembly 60a so that the pivot connection 74a is laterally outwardly of the pivotal connection 68a. A
similar bush 106a to that shown in Figure 5 is utilized at the pivot 68a to have a lower lateral stiffness than longitudinal stiffness.
ThuR, as the truck enters a curve, the outboard wheelset 20 is centered by the conicity of wheels 26 and causes relative rotation between the vehicle body 15 and the truck 10. This moves the steering links 36 longitudinally but in opposite directions. The links rotate their respective carriers 34,34a relative to the sideframes 12 about the pivots 76,78 and 76a,78a so that the bearing a~sembly 30 is longitudinally displaced relative to the respective one of the sideframes. The - displacement is accomodated by rotation of the bearing housing 62 about the vertical pivots 66,68 and by rotation of the bearing assembly 28 relative to the sideframe 12 by virtue of the pivots 122,132. The 207~97~

wheelsets 20,22 thus adopt a radial position relative to the track to avoid flange contact with the rail.
The differential stiffness provided by buches 106,106a allows the sideframe 12 to twist about its longitudinal axis relative to the bearing housing 62 and so introduces a torsional flexibility to the truck 10.
This is described more fully in the application filed on even date herewith entitled "Low Lateral Stiffness Cylindrical Bush" by Peter E. timan. The arrangement of axle shown in Figures 3 and 4 does therefore provide for a pivotal connection to one sideframe and longitudinal displacement of the axle relative to the other sideframe.
Returning to the frame construction of the truck frame 11 shown in Figure 2, a pair of support beams 40 extend between the sideframes 12 at longitudinally spaced locations. The support beams 40 are secured to the sideframes 12 at each end by resilient connections 41. The resilient connection of the beams 40 to the sideframes 12 is through an elastomeric bushing 43 having a high radial stiffness but low lateral stiffness. The bushing 43 is therefore able to accomodate vertical and longitudinal horizontal loads but offers minimum resistance to lateral movement of the sideframes 12.
The beams 40 support a linear induction motor 42 of conventional construction. The motor 42 is secured to one of the beams 40 by a pair of hangers 44 so that the motor 42 moves with the beam 40. The opposite end of motor 42 is supported by a single hanger 46 to the other be~m 40 through a horizontal pin 48. This allows pivotal movement between the beam 40 and the motor as the truck 10 is subjected to torsional loads and inhibits the torsional loading of the motor 42. The high radial stiffness of the bushings 43 accomodates the thrust loads of the motor 42 while maintaining its position relative to the truck.
The truck 10 thus exhibits good torsional flexibility to avoid wheel unloading and good curving 2~7~97~

characteristics by virtue of the forced steering of wheelsets 20,22. However, to maintain stability of the truck in operation it is necesæary to control relative movement of the sideframes 12 without adversely affecting the other parameters. Undue flexibility of the frame 11 in shear will permit the wheelsets to move in phase to a position in which they are no longer tangent to the track which introduced dynamic instabilities into the truck performance.
To inhibit relative longitudinal movement between the sideframes 12, i.e. lozenging, a strut 50 extends diagonally between the sideframes 12. Strut 50 is inclined to the longitudinal axis of the truck 10 and is aligned with the vertical pivot points 32 of the bearings 28 to their respective sideframes 12. Thus, the line of action of the strut 50 passes through the vPrtical pivot points 32 and so not only provides the longitudinal stiffness required to prevent lozenging but avoids imposing significant bending moments in the sideframes 12 between the axles 24. The alignment of the strut 52 with the fixed pivot 32 also maintains the beneficial steering action of the carrier 34 and permits the adjustment of the sideframes to accomodate the displacement of the bearings 30 for steering motion.
Strut 50 is secured to brackets 52 cantilevered from the sideframe 12. In practice, the strut 50 extends as close a~ possible to the pivot axis 32 of the bearings 28 and in some cases may be connected to the bearing itsQlf rather than the sideframe 12. An elastomeric 30 element 54 is located between the strut 50 and bracket 52 to provide the optimum shear stiffness for the truck 10.
As shown, the elastomeric element 54 is a cylindrical elastomeric bush with a pin 53 connecting the strut 50 and bracket 52. If preferred, a ball joint incorporating elastomeric elements may be used or resilient washers interposed between juxtaposed flanges to provide the desired stiffness. A more complicated ' 2~7~7~

structure would include a resilient element in the strut 50 with a direct mechanical connection of the strut 50 to the bracketc 52. The low lateral stiffness bush 106 is located in the bearing assembly 30 opposite to the bearing 28. In this way, the loads induced in the sideframes 12 by the action of the strut 50 do not cause lateral displacement of the bushing or induce torsional loads in the sideframes 12.
It will be seen therefore that a truck is provided in which a forced steering action is maintained but in which lozenging between the sideframes is inhibited by means of a simple lightweight brace constituted by strut 50.
The general arrangement of truck shown in Figures 1 through 5 also has benefits when used in a non-steerable truck such as that commonly employed as a three-piece freight truck. This arrangement is shown in Figures 6 through 8 where components similar to those described above with respect to Figures 1 through 5 are indicated with like refersnce numerals but with a suffix "b" added for clarity.
In the arrangement shown in Figures 6 through 8, the sideframes 12b are supported on wheelsets 20b,22b.
Each of the wheelsets 20b,22b is pivoted to a respective one of the sideframes 12b as indicated generally at 32b.
The opposite end of the respective wheelsets is connected to the sideframe by elastomeric pads 140. As can be seen in Figure 8, the pivot connection 32b i8 formed in a manner similar to that of the embodiment of Figure 3 with a bearing assembly 28b including a bearing housing 116b rotatably supporting the axle 24b by roller bearings 114b. Bearing assembly 28b further includes pivots 122b and 132b to define the pivot axis of the wheelset relative to the sideframe 12b.
The opposite end o the axle 24b is also rotatably supported within a bearing housing 62b by roller bearings 60b. However, in this case the relative 207~97~

longitudinal movement between the sideframes 12b and the bearing housing 62b is accomodated by the elastomeric shear pad 140. As seen in Figure 3, the shear pad 140 includes upper and lower bearing pads 142,144 and an elastomeric element 146. The elastomeric element 146 permits longitudinal movement of the bearing housing 62b relative to the sideframe 12b and thereby allows pivotal movement of the axle relative to the sideframe 12b about the pivots 122b,132b.
As noted above with reæpect to Figures 1 through 5, the strut SOb extends diagonally between the sideframes and is aligned to pass through the pivot axes 32b. Strut 50b is connected to respective sideframes 12b by brackets 52b each of which includes an elastomeric element 54b. The element 54b is a cylindrical elastomeric bush having a uniform radial stiffness or one of the alternatives described above. The strut 50b and element 54b determine the shear stiffness of the truck lOb to inhibit lozenging between the sideframes 12b. The elastomeric element 146 determines the yaw stiffness between the axles; that is, the stiffness to out-of-phase movement of the axles from a parallel position. In this manner, as explained in the above reference USP
4,570,544, the shear stiffness and yaw stiffness of the truck may be selected to provide optimum stability or critical velocity.
The provision of the pivots defined by the bushings 124b,134b at tAe pivotal connections 122b,132b, sideframe 12b and bearing housing 116b permits the use of an elastomeric element that exhibits a high radial stiffness but low torsional stiffness. In this way, the transverse stiffness of the axle relative to the sideframe is improved without affecting the longitudinal stiffness selected for the shear pad 146. Thus, the 3S stability of the truck is improved without adversely affecting the curving performance.

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The strut 50b is connected to the sideframe 12b adjacent to the bearing assembly 12b. This ensures that the forces induced in the strut 50b pass through the pivotal connection 50b where they are transferred by the high radial stiffness bushings 124b,134b to the wheelsets 20b,22b. With such an arrangement, the shear pad 140 is not subjected to the forces in strut 50b and so the lateral stiffness of the elastomeric element 140 may be selected to provide optimum yaw stiffness for the wheelset.

Claims (25)

1. A rail truck comprising a truck frame supported by a pair of longitudinally spaced wheelsets each rotatable about a transverse horizontal axis, said frame including a pair of spaced parallel sideframes supported at opposite ends by said wheelsets and a brace member extending diagonally between opposite ends of each of said sideframes and connected thereto adjacent respective ones of said wheelsets, said frame being connected to each of said wheelsets by a pivotal connection acting between said wheelset and one of said sideframes and by a second connection acting between said wheelset and the other of said sideframes to permit longitudinal displacement of said wheelset relative to said other sideframe to facilitate motion of said wheelset relative to said frame about said pivotal connection, said pivotal connection being located adjacent the connection of said brace member to said sideframe.

2. A rail truck according to claim 1 wherein said pivotal connections and the connections of said brace member to said sideframes are aligned.

3. A rail truck according to claim 2 wherein said brace member includes a resilient element interposed between said sideframes to provide a resilient connection therebetween.

4. A truck according to claim 2 wherein said pivotal connection includes a bearing housing rotatably supporting said wheelset for rotation about a transverse horizontal axis and a pair of vertically aligned bearings connecting said housing to said sideframe for rotation about a vertical axis.

5. A truck according to claim 4 wherein each of said bearings includes an elastomeric element acting between said housing and said sideframe.

6. A truck according to claim 5 wherein one of said elastomeric elements is disposed to transfer vertical loads between said housing and said sideframe.

7. A truck according to claim 6 wherein said one elastomeric is part spherical and transfers radial and vertical loads between said sideframe and housing.

8. A truck according to claim 1 wherein said second connection includes a resilient member interposed between said wheelset and said sideframe to accomodate relative longitudinal movement therebetween.

9. A truck according to claim 8 wherein said pivotal connections and said connections of said brace member to said sideframes are aligned.

10. A truck assembly according to claim 9 wherein said brace member includes a resilient element interposed between said sideframes to provide a resilient connection therebetween.

11. A truck according to claim 10 wherein said brace member includes a strut and elastomeric elements disposed between said strut and respective sideframes.

12. A truck according to claim 11 wherein said brace member is connected to said sideframes by brackets cantilevered from said sideframes and spaced longitudinally from said pivotal connection.

13. A truck according to claim l wherein said second connection includes a steering lever pivotally secured to said sideframe and to said wheelset, for rotation about respective spaced vertical axes.

14. A truck according to claim 13 wherein a steering link extends from said steering lever to a vehicle body supported by said truck to control pivotal movement of said lever.

15. A truck according to claim 14 wherein said pivotal connections and said connections of said brace member to said sideframes are aligned.

16. A truck according to claim 10 wherein said brace member includes a resilient element interposed between said sideframes to provide a resilient connection therebetween.

17. A truck according to claim 16 wherein said brace member includes a strut and elastomeric elements disposed between said strut and respective sideframes.

18. A truck according to claim 17 wherein said brace member is connected to said sideframes by brackets cantilevered from said sideframes and spaced longitudinally from said pivotal connection.

19. A truck according to claim 15 wherein said steering lever is pivotally connected to said wheelset through a bearing housing rotatably supporting said wheelset.

20. A truck according to claim 19 wherein said bearing housing and steering lever are pivotally connected by vertically aligned bearings each of which includes an elastomeric element.

21. A truck according to claim 20 wherein one of said elastomeric elements is disposed to transfer vertical loads between said housing and said sideframe.

22. A truck according to claim 21 wherein said one elastomeric is part spherical and transfers radial and vertical loads between said sideframe and housing.

23. A truck according to claim 19 wherein said steering lever is pivotally connected to said frame by a pair of vertically aligned bearings each of which includes an elastomeric element.

24. A truck according to claim 23 wherein one of said elastomeric elements is disposed to transfer vertical loads between said housing and said sideframe.

25. A truck according to claim 24 wherein said one elastomeric is part spherical and transfers radial and vertical loads between said sideframe and housing.