WO1996015004A1

WO1996015004A1 - Trailer suspension and locking column therefor

Info

Publication number: WO1996015004A1
Application number: PCT/US1994/013046
Authority: WO
Inventors: William J. Hicks; Steven M. Stojic
Original assignee: Nai Neway, Inc.
Priority date: 1994-11-14
Filing date: 1994-11-14
Publication date: 1996-05-23
Also published as: AU1288695A

Abstract

A lockable column (50) is mounted between a trailer frame (14) and a trailing arm suspension (16) and has a primary fluid chamber connected to a reservoir chamber. The chambers are filled with an incompressible fluid and a valve (130) in the fluid path between the two chambers selectively permits or prevents fluid flow between them. When fluid flow is prevented, the column is locked.

Description

TRAILER SUSPENSION AND LOCKING COLUMN THEREFOR

Background of the Invention Field of the Invention

The invention relates to vehicle suspensions for semi-trailers, and more specifically to a vehicle suspension with a lockable support between the suspension and vehicle frame for limiting the relative downward and forward movement of the vehicle frame relative to grade during trailer loading.

Description of the Prior Art

During loading, a trailer is typically backed up against a dock by the tractor. The operator then lowers the front dolly legs on the trailer until they touch the ground. Most trailers have either leaf spring suspensions or trailing arm suspensions with air springs to control the relative position of the frame with respect to an axle and also to cushion the relative movement of the axle toward the frame due to bumps in the road. The resistance of a trailer suspension to loading is not readily adjustable, especially when the trailer is parked and separated from the tractor. For example, although the air springs are pressurized during loading, the air compressor is off during the loading operation.

As the trailer is loaded, the force from the weight of the goods loaded into the trailer including the loading equipment, such as a forklift or a handcar, lowers the rear portion of the frame rail with respect to the axle. Because the compressor is off during the loading operation, the air pressure in an air spring suspension is not adjusted to compensate for the increased load. While the rear portion of the trailer frame moves downwardly, the front portion of the trailer frame is substantially fixed at the height of the dolly and the trailer frame effectively rotates about the contact point of the dolly with the trailer frame. The downward movement of the rear portion of the trailer frame results in the pivotable movement of the pivotal connection between the trailer frame and the trailing arm. This pivotable movement results in the slight rotation of the trailing arm wheel to move the trailer forward away from the dock. In other words, the trailer tends to move away from the loading dock. This movement is referred to as "creep." Creeping of the trailer can create hazards for loading of the trailers. U.S. Patent No. 5333,645, issued August 2, 1994, discloses an apparatus for overcoming this problem by providing a dump valve to exhaust air from the air spring when the trailer door is opened. The trailer thus bottoms out on the suspension before loading begins and cannot creep away from the dock. Whereas this system has worked well to prevent creep, the door switch sometimes malfunctions and the dump valve does not always exhaust air from the air spring.

Therefore, there is a significant need to reduce or eliminate the creeping associated with a trailer during loading. The anti-creeping solution must also be simple, reliable and inexpensive if it is to be commercially viable.

Further, the anti-creep solution must also not interfere with the normal function of the trailing arm suspension during normal operation thereof.

Summary of Invention The foregoing problems are solved by the present invention of a locking column that can be installed between a trailer frame and a conventional trailing arm suspension supporting the trailer frame. The locking column, according to the invention, comprises a first housing which defines a primary fluid chamber. The first housing has an open end and carries a piston for reciprocal movement within the primary fluid chamber. The piston extends out of the open end, and is adapted to connect, for example, to the trailing arm suspension. The first housing is typically mounted to the trailer frame.

A second housing, which defines a reservoir chamber, is fluidly connected to a primary fluid chamber by means of a fluid path. An incompressible fluid fills both the primary and reservoir fluid chambers and the fluid path. A valve is positioned within the fluid path and can be selectively operated between a first position where fluid flow is permitted through the fluid path, and a second position were fluid flow is blocked through the fluid path. When the valve is in the second position, the piston is effectively prevented from reciprocal movement relative to the housing, thereby locking the column.

The device is particularly applicable where it is desired to restrict the phenomenon known as creep whereby a trailer tends to creep away from a loading dock while it is loaded. Locking the column disposed between the trailer frame and the trailer suspension effectively prevents the trailer from "creeping" away from the loading dock.

Preferably, the valve is air operated and comprises a tube and a plunger. The tube has a first aperture fluidly connected to the first housing and a second aperture fluidly connected to the second housing. The plunger is movably mounted within the tube where, in the second position, it is in the fluid path between the first and second apertures, thereby effectively blocking fluid flow between the two chambers. The plunger preferably comprises a head and a base connected by a rod, and a spring is positioned in the tube to bias the head toward the second position.

Typically, the volume of fluid in the reservoir chamber will be defined in part by a second piston which is biased by a spring to respond to changes in fluid volume.

Brief Description of the Drawings The invention will now be described with reference to the drawings wherein:

FIG. 1 illustrates a trailing arm suspension incorporating a locking column according to the invention; and

FIG. 2 is a cross-sectional view in elevation of the lock column illustrated in FIG. 1.

Description of the Preferred Embodiments Figure 1 illustrates a trailing arm suspension 10 incorporating an anti-creep device 12 according to the invention. The trailing arm suspension 10 is mounted to a longitudinal frame rail 14 of a trailer frame and supports an axle 16 to which wheels 18 are mounted on opposite ends of the axle 16.

In a typical trailer application, two trailing arms are used to mount the axle 16 to the frame rail 14. The trailing arms are mounted on opposite sides of the frame rail 14 and support opposing ends of the axle 16. Only one of the trailing arms will be described in detail. The trailing arm suspension 10 comprises a hanger bracket 22 fixedly mounted to the frame rail 14 and to which is rotatably mounted a trailing arm 24 by means of a bushed connection 26 at the forward end of the trailing arm 24. The rearward end of the trailing arm 24 carries an air spring assembly 30, the upper end of which is connected to the frame rail 14. The air spring assembly 30 resiliently resists upward movement of the trailing arm 24 with respect to the frame and comprises a sealed air bag 32 mounted to the frame rail 14 by air spring mounting plate and a piston 34 mounted to a platform 36 on the trailing edge of the trailing arm 24. As the trailing arm 24 rotates in a counterclockwise direction as viewed in FIG. 1, the piston 34 is urged into the air bag 32. Under normal operating conditions, the air bag 32 is pressurized to resiliently retard movement of the trailing arm 24 toward the frame rail 14. The axle 16 is mounted to the trailing arm 24 in a manner well known in the art, such as by an axle mounting bracket 40 having opposing plates 41, which are connected to the trailing arm 24 through two bushed connections 42 and 44.

Referring now to FIG. 2, the anti-creep device 12 according to the invention is a locking column 50, which is pivotally mounted at one end to the frame rail 14 and pivotally mounted at the other end to a portion of the trailing arm suspension, preferably the trailing arm 24. The lockable column 50 is, in general, similar to common struts, such as shock absorbers and the like, in that the lockable column 50 comprises a dampener 52 and a reciprocating piston 54 within the dampener 52. The piston 54 comprises a piston shaft 74 and a piston head 76.

Although the locking column 50 is described herein in the context of an anti-creep device, it should be apparent that the locking column 50 can perform the function of a shock absorber along with the anti-creep function. It is contemplated that the locking column 50 can function as a shock absorber in the trailing arm suspension.

Unlike common struts, the dampener 52 of the lockable column 50 has a housing 56 that defines a cylindrical primary fluid chamber 58 and a cylindrical reservoir fluid chamber 60, which are fluidly connected by a valve 62 for selectively controlling the flow of fluid between the primary fluid chamber 58 and the reservoir fluid chamber 60. Although the valve is illustrated as an air valve 62, any suitable independently actuated valve can be used. The primary fluid chamber 58 is partially defined by an annular wall 68 and upper wall 66 of the housing 56 and is open at a lower end thereof in which the piston head 76 is received for reciprocating movement within the primary fluid chamber 58. The annular wall 68 has a separating wall portion 64, separating the primary chamber 58 from the reservoir chamber 60. An O- ring 68 is positioned within an annular groove 70 of the piston head 76 to fluidly seal the piston head 76 with respect to the primary fluid chamber 58.

The reservoir fluid chamber 60, unlike the primary fluid chamber 58, is closed and is defined by top wall 90, bottom wall 92 and a cylindrical wall 94. A portion of the cylindrical wall 94 forms part of the separating wall portion 64. A spring 96 is disposed within the reservoir fluid chamber 60. One end of the spring 96 abuts the bottom wall 92 and the other end supports a reservoir piston 98, which is fluidly sealed with respect to the housing 56 by an O-ring 100 disposed in an annular groove 102 of the reservoir piston 98. The air valve 62 comprises a hollow cylindrical tube 110 having an open end 112 and a closed end 116, the open end abutting an aperture 114 in the separating wall portion 64. The cylindrical tube 110 extends from the separating wall portion 64 through the side wall 94 so that a portion of the cylindrical tube 110 extends beyond the side wall 94. The cylindrical tube 110 has a reservoir chamber aperture 118, fluidly connecting the reservoir fluid chamber 60 to the primary fluid chamber 58 by establishing a fluid flow path through the reservoir chamber aperture 118, the hollow interior of the cylindrical tube 110 and the separating wall aperture 114. The cylindrical tube 110 has a second aperture 120 in its side forming an air inlet, which fluidly connects a source of pressurized air from the vehicle to the interior of the cylindrical tube 110. Preferably, the source of pressurized air is the emergency brake air system, which contains air pressurized to approximately 100 psig during operation of the vehicle and unpressurized air when the vehicle is not operated. The air valve 62 comprises an air-operated plunger valve 130.

The plunger valve 130 includes a plunger 132 positioned within the hollow interior of the cylindrical tube 110 and biased away from the closed end 116 by a spring 134. The plunger comprises a head 136 connected to a base 138 by a rod 140. Rod 142 runs through and is sealed by an interior wall 142 with O-ring seal 143. The spring 134 is placed between the closed end 116 of the cylindrical tube 110 and the base 138 of the plunger 132 to bias the head 136 toward the reservoir chamber aperture 118. The plunger 132 moves reciprocally within the cylindrical tube 110 by the addition or exhaustion of air through the air inlet opening 120. The introduction of pressurized air to the tube 110 through the air inlet 120 urges the plunger 132 away from a sealed position where the head 136 of the plunger blocks fluid flow between the reservoir chamber aperture 118 and the separating wall aperture, and toward the closed end 116 to an unsealed position where fluid flow is permitted.

Under normal operating conditions, the emergency brake air system is pressurized and the head 136 of the plunger 132 is withdrawn from sealing the reservoir chamber aperture 118. Therefore, fluid is free to flow between the primary fluid chamber 58 and the reservoir fluid chamber 60. As the piston 54 reciprocates in response to swinging movement of the trailing arm 24, the fluid disposed within the primary fluid chamber is directed into the reservoir fluid chamber 60 when the piston 54 moves into the primary fluid chamber 58. As the fluid flows from the primary fluid chamber 57 into the reservoir fluid chamber, the reservoir piston 98 is urged toward the bottom wall 92 against the force of the spring 96 in response to the pressure associated with the incoming fluid. As the piston 54 moves out of the primary fluid chamber 58, the reservoir piston 98 is biased by the spring 96 away from the bottom wall 92 to force the fluid from the reservoir fluid chamber 60 into the primary fluid chamber 58, hence, frothing of the fluid is prevented. The fluid in the housing 56 is substantially incompressible and will maintain a constant volume. The piston 54 and the reservoir piston 98 thus move in response to each other. As can be seen, during normal operation, the anti-creep devices 12 according to the invention functions substantially like a typical shock absorber in that the fluid in the primary chamber is passed through a reduced orifice to dampen the movement of the piston 54.

However, when the trailer is loaded, the emergency brake air system is exhausted and the spring 134 of the plunger valve 130 urges the head 136 of the plunger 132 into a sealing position with respect to reservoir chamber aperture 118. When the head 136 of the plunger valve 130 is in the sealing position, the fluid flow path between the primary fluid chamber 58 and the reservoir fluid chamber 60 is blocked, preventing the flow of fluid between the two chambers. As the trailer is loaded, there is no relative movement between the frame rail 14 and the trailing arm 24 because the fluid in the housing 56 is incompressible and can no longer flow into the reservoir fluid chamber 60. Therefore, the piston 54 is effectively prevented from moving inwardly of the primary fluid chamber 58 to effectively lock the position of the frame rail 14 with respect to the trailing arm 24 and to prevent the creeping of the trailer.

Once pressurized air is restored, it will urge the plunger 132 against the force of the spring 134 of the plunger valve 130 to withdraw the plunger head 136 away from its sealing position with respect to the reservoir chamber aperture 118. The fluid will then be free to flow between the primary fluid chamber 58 and the reservoir fluid chamber 60, allowing relative movement between the frame rail 14 and the trailing arm 24.

While particular embodiments of the invention have been shown, it will be understood, of course, that the invention is not limited thereto since modifications may be made by those skilled in the art, particularly in light of the foregoing teachings. For example, the piston 54 is illustrated as being solid and the reservoir fluid chamber 60 is positioned at the side of the housing 52. It is within the scope of the invention to use a hollow piston and place the reservoir fluid chamber 60 within the hollow piston. The valve would be positioned at the end of the piston head and could be electrically actuated by use of a solenoid valve, for example, or mechanically actuated by use of an air valve, for example. Reasonable variation and modification are possible within the scope of the foregoing disclosure of the invention without departing from the spirit of the invention.

Claims

AMENDED CLAIMS[received by the International Bureau on 22 December 1995 (22.12.95) ; original claims 1 , 8-11 and 21 amended ;remaining claims unchanged (5 pages ) ]The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A locking column for a trailing arm suspension mounted to a trailer frame, the trailing arm suspension comprising a trailing arm rotatably mounted at one end to the trailer frame, a spring mounted between another end of the trailing arm and the trailer frame to resiliently resist the rotation of the trailing arm toward the trailer frame, an axle mounted to the trailing arm, and a wheel mounted to the axle, the locking column comprising: a first housing defining a primary fluid chamber and having an open end, the housing being adapted to pivotally connect to one of the frame and a portion of the suspension; a piston disposed within the first housing for reciprocal movement relative thereto, and having a portion thereof extending out of the housing through the open end, the piston being adapted to pivotally connect to the other of the frame and a portion of the suspension; a second housing defining a reservoir chamber with a fluid path connecting the primary fluid chamber only to the reservoir fluid chamber; a substantially incompressible fluid filling the primary and reservoir chambers and the fluid path; and a valve positioned within the fluid path and selectively operable between a first position where fluid flow is permitted through the fluid path and a second position where fluid flow is blocked; whereby, when the valve is in the second position, the piston will be prevented from reciprocating relative to the housing.

2. A locking column according to claim 1 wherein the valve is an air-operated valve adapted to connect to a source of pressurized air and comprises a tube and a plunger, the tube having a first aperture fluidly connected to the first housing and defining in part the fluid path and a second aperture fluidly connected to the second housing and defining in part the fluid position, it is in the fluid path between the first and second apertures and, in the first position, it is not in the fluid path between the first and second apertures.

3. A locking column according to claim 2 wherein the plunger comprises a head and a base connected by a rod.

4. A locking column according to claim 3 wherein one end of the tube is closed and a spring is positioned between the closed end of the tube and the base to bias the head toward the second position.

5. A locking column according to claim 1 and further comprising a second piston movably mounted within the reservoir for reciprocal movement thereto in response to the flow of fluid between the housing and the reservoir.

6. A locking column according to claim 5 wherein the second piston further comprises an O-ring disposed within a groove in the second piston for sealing the piston with respect to the reservoir.

7. A locking column according to claim 5 and further comprising a spring positioned in the second housing to bias the second piston toward a position to reduce the volume of incompressible fluid in the reservoir chamber.

8. A locking column according to claim 1 wherein the piston further comprises a shaft and a head, the head mounted on the end of the shaft and received within the first housing.

9. A locking column according to claim 8 wherein the piston head has an annular groove and an O-ring is received in the annular groove to seal the piston head with respect to the housing.

10. In a trailing arm suspension for a trailer frame, the trailing arm suspension comprising a trailing arm for rotatably mounting at one end to a trailer frame, a spring for mounting between another end of the trailing arm and the trailer frame to resiliently resist the rotation of the trailing arm toward the trailer frame, and a shock absorber comprising a first part adapted to be mounted at one end to the trailing arm and a second part adapted to be mounted at an end to the trailer frame, the first and second parts having a telescoping relationship and adapted to function as a shock absorber by the relative reciprocal movement of the first and second shock absorber parts as the trailing arm rotates with respect to the vehicle frame; the improvement which comprises: one of the first and second shock absorber parts defines a primary fluid chamber and one of the first and second shock absorber parts defines a reservoir fluid chamber, which is fluidly connected along a fluid path only to the primary fluid chamber, whereby the reciprocating movement of the first shock absorber part relative to the second shock absorber part moves fluid from one of the primary fluid chamber and the reservoir fluid chamber to the other of the primary fluid chamber and the reservoir fluid chamber; a lock positioned within the fluid path between the primary fluid chamber and the reservoir fluid chamber to selectively fix the first and second shock absorber parts with respect to each other to thereby selectively lock the trailing arm with respect to the trailer frame.

11. In a trailing arm suspension according to claim 10 wherein the lock is a selectively actuable valve positioned within the fluid path between the primary fluid chamber and the reservoir fluid chamber such that when the valve is open, fluid is free to flow between the primary fluid chamber and the reservoir fluid chamber, and when the valve is closed, fluid is prevented from flowing between the primary fluid chamber and the reservoir fluid chamber and the first shock absorber part is locked with respect to the second shock absorber part.

12. In a trailing arm suspension according to claim 11 wherein the first shock absorber part defines the primary fluid chamber.

13. In a trailing arm suspension according to claim 12 wherein the first shock absorber part defines the reservoir fluid chamber is formed by another portion of the first shock absorber part.

14. In a trailing arm suspension according to claim 11 wherein the valve is an electrically actuated valve.

15. In a trailing arm suspension according to claim 14 wherein the electrically actuated valve is a solenoid valve.

16. In a trailing arm suspension according to claim 11 wherein the valve is an air-operated valve adapted to connect to a source of pressurized air and comprising a tube and a plunger, the tube having a first aperture fluidly connected to the primary fluid chamber and defining in part the fluid path and a second aperture fluidly connected to the reservoir fluid chamber and defining in part the fluid path, the plunger being movably mounted within the tube where, in a second position, it is in the fluid path between the first and second apertures and, in a first position, it is not in the fluid path between the first and second apertures.

17. In a trailing arm suspension according to claim 16 wherein the plunger comprises a head and a base connected by a rod.

18. In a trailing arm suspension according to claim 17 wherein one end of the tube is closed and a spring is positioned between the closed end of the tube and the base to bias the head toward the second position.

19. In a trailing arm suspension according to claim 18 and further comprising a piston movably mounted within the reservoir fluid chamber for reciprocal movement thereto in response to the flow of fluid between the primary fluid chamber and the reservoir fluid chamber. -12-

20. In a trailing arm suspension according to claim 19, wherein the piston further comprises an O-ring disposed within a groove in the piston for sealing the piston with respect to the reservoir.

21. In a trailing arm suspension according to claim 10, the first shock absorber part comprising: a first housing telescopically receiving the second shock absorber part and defining a primary fluid chamber between the first housing and the second shock absorber part; a second housing defining a reservoir chamber with a fluid path connecting the primary fluid chamber only to the reservoir fluid chamber; a substantially incompressible fluid filling the primary and reservoir chambers and the fluid path; and a valve positioned within the fluid path and selectively operable between a first position where fluid flow is permitted through the fluid path and a second position where fluid flow is blocked; whereby, when the valve is in the second position, the second shock absorber part will be prevented from reciprocating relative to the housing.