COMPENSATING MECHANISM FOR A VEHICLE ACCESS RAMP

BACKGROUND OF THE INVENTION Field of the Invention

[0001] The present invention relates to a compensating mechanism for a vehicle access ramp, particularly a low floor vehicle access ramp, sometimes called a flip-over or "fold-out" ramp.

Description of Related Art

[0002] A flip-over ramp assembly is normally stowed in a generally horizontal position in a recess in a vehicle floor and can be pivoted upward and outward to a downward sloping deployed position after the vehicle door has been opened as shown, for example, in U.S. Patent No. 6,179,545 entitled "Flip-Over Ramp." The ramp assembly comprises a mounting enclosure and a ramp which are pivotally connected at their adjacent edges which provides a horizontal axis for movement of the ramp between deployed and stowed positions. [0003] Ramp deploying mechanisms having torque compensating mechanisms are generally known in the art. See, for example, U.S. Patent No. 6,843,635 entitled "Vehicle Fold-Out Ramp." However, typical prior art devices are often very complex and difficult to install and maintain. Thus, the reliability of such devices is reduced. When such devices fail, substantial forces are needed to move the vehicle ramp between stowed and deployed positions, which require excessive manual labor or very heavy bearing loads during power- assisted stowing and deploying. Thus, typical prior art devices impose undue labor and material expense burdens on users.

[0004] Accordingly, there is a general need for a deploying mechanism for a vehicle access ramp that effectively counterbalances the weight of the vehicle access ramp so as to reduce the force required to move the ramp between deployed and stowed positions, eases manual operation, is less complex, lower in cost, and easier to install and maintain in comparison to prior art devices.

SUMMARY OF THE INVENTION

[0005] It is an object of the present invention to provide a compensating mechanism for counterbalancing the weight of a vehicle access ramp being moved between stowed and deployed positions where all components are individually replaceable. [0006] It is an object of the present invention to provide a compensating mechanism that is less complex and where the cost of material, manufacturing and installation of the ramp, the

compensating mechanism, and the driving mechanism are reduced and additionally where labor and maintenance costs are reduced in comparison to prior art devices. [0007] It is an object of the present invention to provide a compensating mechanism that counterbalances, that requires less energy to deploy and stow the vehicle access ramp when operated under power, and that requires less force when operated manually. [0008] The present invention relates to an improvement in a ramp assembly comprising a mounting enclosure for a frame and a ramp. The frame and the ramp are pivotally connected at their adjacent edges which provide a horizontal axis for movement of the ramp between deployed and stowed positions by an actuator assembly mounted to the frame. It is an improvement, according to this invention, that the actuator assembly comprises a double- acting, counterbalance mechanism that utilizes a compression spring (mechanical or pneumatic) to apply a torque to a drive wheel operatively connected to a drive mechanism and a load wheel operatively connected to the ramp via a rigid link and a flexible member encircling the drive wheel and the load wheel. The torque created by the spring opposes the torque caused by the weight of the vehicle ramp proportional to the amount of spring compression in two directions.

[0009] According to one embodiment of the present invention, there is provided a compensating mechanism for a vehicle ramp deployed by a drive mechanism. The compensating mechanism includes a drive wheel operatively connected to the drive mechanism and a load wheel operatively connected to the ramp. A flexible member, such as a belt chain, is disposed about the drive wheel and the load wheel, the flexible member having two opposing ends and being adapted for transmitting a drive torque from the drive wheel to the load wheel and for transmitting a load torque from the load wheel to the drive wheel. A rigid link is connected to the two opposing ends of the flexible member so as to form a loop with the flexible member. First and second retainers are sKdably disposed on the rigid link and spaced apart. A spring is disposed between the first and second retainers about the rigid link. A first restraint is adapted for preventing relative movement of the first retainer with respect to the rigid link in a first direction and a second restraint is adapted for preventing relative movement of the disk retainer with respect to the rigid link in a second direction. A first stop is adapted for limiting relative movement of the first retainer in the first direction with respect to a fixed frame and a second stop is adapted for limiting relative movement of the second retainer in the second direction with respect to the fixed frame. The spring is in a compressed condition in the second direction against the first retainer and the second stop when the ramp is oriented toward a stowed position so as to apply a torque to the

drive wheel and the load wheel in the first direction via the rigid link and the flexible member. The spring is in a neutral, preloaded condition when the ramp is in a substantially vertical position so as to apply minimal torque to the drive wheel and the load wheel. The spring is in a compressed condition in the first direction against the second retainer and the first stop when the ramp is oriented toward a deployed position so as to apply a torque to the drive wheel and the load wheel in the second direction via the rigid link and the flexible member.

[0010] Further details and advantages of the present invention will become clear upon reading the following detailed description in conjunction with the accompanying drawing figures, wherein like parts are designated with like reference numerals throughout. [0011] According to another embodiment of the present invention, the compensating mechanism includes the drive wheel, load wheel, and flexible member as already described. The ends of the flexible member are secured to the ends of a rigid box-shaped follower. A pneumatic spring cylinder is fixed to the frame and has first and second piston rods extending from each end, each extending toward the ends of the rigid box-shaped follower when the follower is placed over the pneumatic cylinder. Depending on the position of the follower relative to the pneumatic cylinder, the ends of the piston rods may both contact the follower or the end of one or the other piston rods may contact the follower. The gas in the pneumatic cylinder is compressed by the piston at the end of the first piston rod when the ramp is positioned toward the stowed position so as to apply torque to the drive wheel and the load wheel in a first direction via the follower. The gas in the pneumatic cylinder is in a neutral preloaded condition when the ramp is in a substantially vertical position so as to apply minimal torque to the drive and load wheels. In this position, the pistons are spaced apart and located near each end of the follower. The gas in the pneumatic cylinder is compressed by the piston at the end of the second piston rod when the ramp is positioned toward the deployed position so as to apply torque to the drive wheel and the load wheel in a second direction via the follower

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Fig. 1 is a plan view of a vehicle access ramp and frame having a drive mechanism and a compensating mechanism according to an embodiment of the present invention for deploying and stowing the ramp;

[0013] Fig. 2 is a side view of the compensating mechanism according to an embodiment of the present invention;

[0014] Fig. 3 is a detailed side view of a portion of a coil spring compensating mechanism;

[0015J Fig. 4 is a schematic of the coil spring compensating mechanism in a state where the ramp is in a stowed position;

[0016) Fig. 5 is a schematic of the coil spring compensating mechanism in a state where the ramp is in a substantially vertical position;

[0017] Fig. 6 is a schematic of the coil spring compensating mechanism in a state where the ramp is in a deployed position;

[0018 j Fig. 7 is a section view of a double-acting air spring compensating mechanism in the state where the ramp is in a substantially vertical position;

[0019] Fig. 8 is a section view of a double-acting air spring where the compensating mechanism is in the ramp stowed position; and

[0020] Fig. 9 is a section view of a double-acting air spring where the compensating mechanism is in the ramp deployed position.

DESCRIPTION OF THE INVENTION

[0021] For purposes of description hereinafter, spatial orientation terms, if used, shall relate to the referenced embodiment as it is oriented in the accompanying drawing figures or otherwise described in the following detailed description.

[0022] Figs. 1 to 6 show a compensating mechanism 10 for a vehicle access ramp R that is moved between the stowed and deployed positions by a drive mechanism 20 via the compensating mechanism 10. The ramp generally comprises a flat plate with top and bottom surfaces. As shown in Fig. 1, the vehicle ramp R is pivotably attached to a frame F that houses the compensating mechanism 10 and the drive mechanism 20. The pivotal connection along one edge of the ramp and an adjacent edge is supported by the frame. In the deployed position, the top surface of the ramp extends from the vehicle to the curb adjacent the vehicle. In the stowed position, the ramp is rotated at least 180° about the pivotal connection and comprises the floor of the vehicle. A flange G is attached to a face of the vehicle ramp R and connects the vehicle ramp R to a load wheel 18 of the compensating mechanism (shown in Fig. 2), thereby applying a load torque Ti (shown in Fig. 2) caused by the weight of the ramp R and the flange G to the load wheel 18. As shown, only one compensating mechanism 10 and flange G is shown. It is to be appreciated that a second compensating mechanism 10 and flange G may be provided at an opposite side of the vehicle ramp R so as to support and move the vehicle ramp at both sides thereof.

[0023] Drive mechanism 20 includes a motor 21 which is preferably an electric motor, though motors of other types may be used and still fall within the scope of the present invention. Alternatively, drive mechanism 20 may be manually operated by a hand crank or the like. Motor 21 is operatively connected to a drive shaft 23 by a flexible member 22, such as a chain, disposed about a rotating shaft of the motor 21 and the drive shaft 23. Drive shaft 23 is operatively connected to a drive wheel 19 of the compensating mechanism, as is shown in Fig. 1. During operation, a rotating shaft of the motor 21 causes the flexible member 22 to move about a path around the rotating shaft of the motor 21 and the drive shaft 23 so as to cause the drive shaft to rotate thereby applying a drive torque T ₂ (shown in Fig. 2) to drive wheel 19.

[0024] As shown in Figs. 2 and 3, compensating mechanism 10 includes a drive wheel 19 and a load wheel 18 rotatably attached to the frame F at distal positions. A flexible member 31 is disposed about the drive wheel 19 and the load wheel 18 and has two opposing ends. The flexible member 31 transmits a drive torque T ₂ from the drive wheel 19 to the load wheel 18 and a load torque T ₁ from the load wheel 18 to the drive wheel 19. A rigid link 12 is connected to the two opposing ends of the flexible member 19 so as to form a loop. As shown in Figs. 2 and 3, load wheel 18 and drive wheel 19 are sprockets with flexible member 31 being a chain for engaging teeth about the perimeter of the sprockets on the load and drive wheels 18, 19. It is to be appreciated that load wheel 18 and drive wheel 19 may be of any type known to those of ordinary skill in the art to be suitable for transmitting torque via a flexible member , including pulleys or sheaves. Likewise, flexible member 31 may be a belt or band made from an elastomeric material as opposed to a chain.

[0025] With reference to Fig. 3, a cup retainer 14 is coaxially disposed on the rigid link 12 and a disk retainer 13 is also coaxially disposed on the rigid link 12 at a position distal to the cup retainer 14. A spring 11 is disposed between the disk retainer 13 and the cup retainer 14 and extends coaxially about the rigid link 12.

[0026 J A first restraint 15 is disposed on the rigid link 12 proximal to the cup retainer 14 and prevents relative movement of the cup retainer 14 with respect to the rigid link 12 in a first or counterclockwise direction. That is to say, first restraint 15 fixes the cup retainer 14 against movement in the first direction unless the rigid link 12 is simultaneously moving in the first direction with the cup retainer 14. A second restraint 9 is disposed on the rigid link 12 proximal to the disk retainer 13 and prevents relative movement of the disk retainer 13 with respect to the rigid link 12 in a second or clockwise direction. That is to say, second restraint 15 fixes the disk retainer 13 against movement in the second direction unless the

rigid link 12 is simultaneously moving in the second direction with the disk retainer 13. As shown in Figs. 2 and 3, first and second restraints 15, 9 are pins disposed on or through the rigid link 12. It is to be appreciated that first and second restraints 15, 9 may be of any type known by those of ordinary skill in the art to be suitable for preventing relative movement between the cup retainer 14 and the rigid link 12 and the disk retainer 13 and the rigid link 12 including washers fixedly attached to the rigid link 12.

[0027] A first stop 17 is disposed on the frame F proximal to the cup retainer 14 and limits the relative movement of the cup retainer 14 with respect to the frame F in the first direction. A second stop 16 is disposed on the frame F proximal to the disk retainer 13 and limits the relative movement of the disk retainer 13 with respect to the frame F in the second direction. That is to say, first stop 17 and second stop 16 are fixedly attached to the frame F and limit the movement of the cup retainer 14 and the disk retainer 13 relative to the frame F to a certain point in either the first or second directions, respectively. As shown in Figs. 2 and 3, first stop 17 and second stop 16 are brackets extending from a sidewall of the frame F. It is to be appreciated that first stop 17 and second stop 16 may be of any type known by those of ordinary skill in the art to be suitable for limiting movement of the cup retainer 14 and the disk retainer 13, including portions of the frame F extending to engage the cup retainer 14 and the disk retainer 13.

[0028] With reference to Figs. 4-6, operation of the compensating mechanism 10 acting as a bidirectional counterbalance to the weight of the ramp R in three basic positions is depicted schematically. A full operating cycle starts with the ramp plate in a stowed position (Fig. 4). The ramp plate is then moved in the first direction (counterclockwise) to a substantially vertical neutral position by the drive mechanism 20 via the compensating mechanism 10 (Fig. 5). The ramp plate is then moved further in the first direction until it reaches the deployed position (Fig. 6). To move the ramp plate to the stowed position from the deployed position, the process is reversed with the ramp plate moving in the second (clockwise) direction. [0029] As shown in Fig. 4, when in the stowed position, the ramp plate is disposed parallel to the vehicle floor (not shown) causing a load torque Ti in the second (clockwise) direction to be applied to the load wheel 18 and the drive wheel 19 via the flexible member 31 and rigid link 12. The spring 11 is in a fully compressed condition in the second direction against the disk retainer 13 and the second stop 16, thereby causing an opposing torque acting in the first (counterclockwise) direction to be applied to the drive wheel 19 and the load wheel 18 via the rigid link 12 and the flexible member 31. The drive mechanism 20 engages the drive wheel 19 to apply a drive torque T ₂ in the first direction so as to cause the drive wheel 19 to

rotate in the first direction, which causes the flexible member 31 and drive link 12 to move in a path about the drive wheel 19 and the load wheel 18. Thus, load wheel 18 is caused to rotate in the first direction, in turn, and lift the ramp plate from the stowed position toward the substantially vertical neutral position. The opposing torque in the first direction resulting from compression of the spring 11 is applied to the drive wheel 19 proportional to the amount of compression of the spring 11 as the ramp plate remains oriented toward the stowed position prior to reaching the substantially vertical neutral position. Thus, the motor 21 is assisted in moving the ramp plate from the stowed position toward the substantially vertical neutral position, which substantially reduces drive motor torque T ₂ and power necessary to deploy the ramp plate. As the ramp plate approaches the substantially vertical neutral position, the ramp plate will be biased toward the neutral position due to bidirectional compression of the spring 11.

[0030] As shown in Fig. 5, as the ramp plate reaches the substantially vertical neutral position, the spring 11 is in a neutral, preloaded condition and applies minimal torque to the drive wheel 19 and the load wheel 18. After passing the substantially vertical neutral position, the ramp plate becomes oriented toward a deployed position and commences compressing the spring in the first direction until it reaches the fully deployed position as in Fig. 6. The spring 11 and drive mechanism 20 act as a brake by causing a torque in the second direction that opposes the load torque Ti, now acting in the first direction, caused by the weight of the ramp plate until the ramp plate tip touches ground. The rigid link 12 extends in the first direction as in Fig. 6 and remains within the confines of the cup retainer 14.

[0031] As shown in Fig. 6, when in the deployed position, the ramp is disposed such that the tip of the ramp plate touches the ground causing a load torque T ₁ in the first direction to be applied to the load wheel 18 and the drive wheel 19 via the flexible member 31 and rigid link 12. The spring 11 is in a fully compressed condition in the first direction against the cup retainer 14 and the first stop 17, thereby causing an opposing torque acting in the second direction to be applied to the drive wheel 19 and the load wheel 18 via the rigid link 12 and the flexible member 31. The drive mechanism 20 engages the drive wheel 19 to apply a drive torque T ₂ in the second direction so as to cause the drive wheel 19 to rotate in the second direction, which causes the flexible member 31 and drive link 12 to move in a path about the drive wheel 19 and the load wheel 18. Thus, load wheel 18 is caused to rotate in the second direction, in turn, and lift the ramp plate from the deployed position toward the substantially vertical neutral position. The opposing torque in the second direction resulting from

compression of the spring 11 is applied to the drive wheel 19 proportional to the amount of compression of the spring 11 as the ramp plate remains oriented toward the deployed position prior to reaching the substantially vertical neutral position. Thus, the motor 21 is assisted in moving the ramp plate from the deployed position toward the substantially vertical neutral position, which substantially reduces drive motor torque T ₂ and power necessary to stow the ramp plate.

[0032] As the ramp plate approaches the substantially vertical neutral position, the ramp plate will be biased toward the neutral position due to bidirectional compression of the spring 11 as shown in Fig. 5. After passing the substantially vertical neutral position, the ramp plate becomes oriented toward a stowed position and commences compressing the spring in the second direction until it reaches the fully stowed position as shown in Fig. 4. The spring 11 and drive mechanism 20 act as a brake by causing a torque in the first direction that opposes the load torque Ti, now acting in the second direction, caused by the weight of the ramp plate until the ramp plate reaches the stowed position.

[0033] Without the compensating mechanism 10, load torque T ₁ would be passed from the load wheel 18 to the drive wheel 19 and drive torque T ₂ would be equal to Ti multiplied by a reduction rate. As can be appreciated, the compensating mechanism 1O ₅ according to the present invention, operates to save energy and reduce manual effort by applying a varying torque to the drive wheel 19 and the load wheel 18 via the rigid link 12 and the flexible member 31 that opposes the load torque T ₁ caused by the weight of the vehicle ramp R. Theoretically, the necessary manual operating force can be reduced to zero. While only one compression spring 11 is necessary for moving the vehicle ramp R between positions, two or more may be used.

[0034] Referring to Figs. 7-9, the compensating mechanism includes the drive wheel, load wheel, and flexible member as already described. The ends of the flexible member are secured to the ends of a rigid box-shaped follower 42. A pneumatic spring cylinder 43 is fixed to the frame and has first and second piston rods 44, 45 extending from each end, each extending toward the ends of the rigid box-shaped follower when the follower is placed over the pneumatic cylinder. Depending on the position of the follower relative to the pneumatic cylinder, the ends of the piston rods may both contact the follower or the end of one or one or the other of the piston rods may contact the follower. The gas in the pneumatic cylinder is compressed by the piston at the end of the first piston rod when the ramp is positioned toward the stowed position (see Fig. 8) so as to apply torque to the drive wheel and the load wheel in a first direction via the follower. The gas in the pneumatic cylinder is in a neutral preloaded

condition (see Fig. 7) when the ramp is in a substantially vertical position so as to apply minimal torque to the drive and load wheels. In this position, the pistons are spaced apart and located near each end of the follower. The gas in the pneumatic cylinder is compressed by the piston at the end of the second piston rod when the ramp is positioned toward the deployed position (see Fig. 9) so as to apply torque to the drive wheel and the load wheel in a second direction via the follower.

[0035] As can also be appreciated, the present invention is not limited to applications regarding the deployment of vehicle ramps but may be used in any device that may benefit from torque and power reduction.

[0036] The presently preferred embodiments described herein are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the full breadth of the appended claims and any and all equivalents thereof.