GB2061841A - Load carrying vehicle - Google Patents

Abstract

A damping system (43) for use in a lift truck (10) to damp oscillating motions of the vehicle frame (14). The system includes a pair of hydraulic tilt cylinders (46a, 46b) which sense moments of force of a carried load (12). A pair of second hydraulic cylinders (72a, 72b) are in communication with the tilt cylinders, and are connected to a rear axle (28) of the vehicle. The rear axle is resiliently mounted from a second end portion (18) of the vehicle frame (14), and is moved by the second cylinders in directions substantially normal to the vehicle frame. Such movement is responsive to sensed moments of force of the lifted load. Two damping system embodiments (43 and 43') are disclosed.

Description

SPECIFICATION Load carrying vehicle The invention relates to load carrying vehicles such as lift trucks.

When load carrying vehicles, such as lift trucks, traverse uneven terrain, their operators are subjected to oscillating motions of the vehicle frame. Such motions are also encountered when applying the brakes, and when picking up or dropping loads. These oscillations are made more acute by changes in moments of force caused by a load being carried. As a consequence, an operator is subjected to a hard, loping ride which tends to be quite uncomfortable, and may hinder maneuverability.

In accordance with the present invention a load carrying vehicle comprises a frame having first and second ends; an axle mounted on the second end; a load carrying device connected to the first end; sensing means for sensing variations in the force imposed on the first end by the load carrying device; and damping means for moving the axle and the frame second end up and down relatively to one another in response to the variations in the moment of force sensed by the sensing means to reduce oscillation of the vehicle frame.

The load carrying device may be pivoted to the frame first end.

Accordingly, the damping system acts to damp oscillating motions of the vehicle, provides a smoother, more comfortable ride for its operator thereof, and also provides for ease of maneuverability.

Preferably, the sensing means comprises at least one fluid cylinder.

Two examples of a vehicle constructed in accordance with the present invention are illustrated in the accompanying drawings, in which: Figure 1 is a side elevation partly in phantom and partly in section of the first example; Figure 2 is an enlarged diagrammatic view part of which is taken on the line ll-ll in Fig.

1; Figure 3 is an enlarged, perspective view of part of the second example; and, Figure 4 is a section taken on the line IV-IV in Fig. 3.

Fig. 1 illustrates a vehicle 10, herein illustrated as a lift truck, for lifting and carrying a load 1 2. The vehicle 10 has a horizontally disposed frame 14 with a frame first end portion 1 6 and a frame second end portion 1 8. The vehicle 10 includes a pair of first ground engaging members or wheels 20 and a pair of second ground engaging members or wheels 22, such as rim-mounted standard tyres.

Wheels 20 may be mounted on a conventional drive axle (not shown) whereas wheels 22 are mounted on an axle 28 (illustrated in Figs. 1 and 2), or an axle 28' (illustrated in Figs. 3 and 4). The axles 28 and 28' are massive, with substantial weights, and are mounted on the frame second end portion 1 8.

The mountings for axles 28 and 28' and the differences therebetween are further discussed hereinafter.

Returning to Fig. 1, a standard load lifting and carrying device 30 for load 1 2 comprises a mast member 32, a carriage 34 slidably mounted thereupon, and a fork member 36 connected to carriage 34 for supporting the load 1 2 when lifted by device 30. The load carrying device 30 is normally pivotally connected to the frame first end portion 1 6 by various conventional means, such as a pillow block 35 on the frame first end portion 16, to permit the mast member 32 to tilt. This connection between the carrying device 30 and the frame first end portion 1 6 defines a substantially horizontal pivot axis 42.

In a vehicle, such as vehicle 10 above described, a damping system embodiment 43 includes sensing means 44 for sensing a moment of force about the pivot axis 42 of a load 1 2 lifted on the load lifting device 30, and a damping means 45 for responsively moving the axle 28 in directions substantially normal to the frame second end portion 1 8 in response to moments of force sensed by the sensing means 44 and communicating thereby. The damping means 45 will be more fully discussed hereinafter.

Sensing means 44 may conveniently be a pair of double-acting hydraulic tilt cylinders 46a and 46b as shown in Fig. 2. Each tilt cylinder 46a, 46b is substantially the same as the other, and the description will thus describe tilt cylinder 46a as representative of both unless otherwise noted.

Referring to Fig. 2, hydraulic tilt cylinder 46a has a rod end 48a, a head end 50a, and a piston assembly 51 a. Piston assembly 51 a has a piston head 52a and a piston rod 53a extending therefrom. The piston head 52a is slidable within the tilt cylinder 46a and isolates the rod end 48a from the head end 50a.

The tilt cylinder 46a is connected to the load carrying device 30, more specifically to the mast member 32, by the piston rod 53a and is connected to the frame first end portion 1 6 at the head end 50a. Inside each of the rod and head ends 48a, 50a is contained a full quantity of pressurized hydraulic fluid. This fluid has a steady-state (carry) pressure when both ends of the cylinder are blocked at the control valve (not shown) which is determined by a hydraulic system of vehicle 10 (the hydraulic system being conventional and not herein illustrated or further discussed).

A moment of force of load 1 2 about pivot axis 42, with a direction inward with respect to tilt cylinder 46a, will be sensed by the rod end 48a as a decrease in the pressure of the fluid therein; whereas a moment force of load 1 2 about pivot axis 42 outward with respect to tilt cylinder 46a will be sensed by the rod end 48a as an increase in the pressure of the fluid therein. As may be appreciated, since a fixed quantity of hydraulic fluid fills both the rod end 48a and the head end 50a, the piston 51 a will not substantially move.

The tilt cylinder 46a has an outlet 60a in the rod end 48a thereof which is in communication with a conduit 62. Conduit 62 crosscommunicates between each tilt cylinder 46a, 46b and thence to a conduit 63. Conduit 63 is adapted to carry pressurized hydraulic fluid therethrough, and extends toward the frame second end portion 1 8. Alternatively, conduit 62 could be interconnected between the head ends 50a, 50b of cylinders 46a, 46b. Tilt cylinders 46a, 46band connecting conduits 62, 63 are completely filled with fluid.

The conduit 63 communicates hydraulic fluid to the damping means 45. Damping means 45 is for responsively moving the axle 28 in directions substantially normal to the frame second end portion 1 8 which leads to damping the oscillations of frame 14.

Referring to Fig. 2, the damping means 45 of the damping system embodiment 43 includes a pair of double-acting hydraulic cylinders 72a and 72b preferably disposed in tandem relationship along the longitudinal axis 73 of the vehicle. Each hydraulic cylinder 72a and 72b is substantially the same as the other, and thus the cylinder 72a will be hereinafter discussed as representative of both unless otherwise noted.

Turning to Fig. 1, the hydraulic cylinder 72a is pivotally connected at a cylinder first end 74a to the frame second end portion 18.

The cylinder 72a has a piston assembly 76a slidably received within a rod end 78a of the cylinder 72a. The rod end 78a is in communication with a second end portion 68 of the conduit 63. The piston assembly 76a has a piston head 84a and a piston rod 88a slidably disposed in cylinder 72a. The rod 88a extends from rod end 78a of cylinder 72a and is pivotally connected to axle 28.

Referring to Fig. 2, the axle 28 is mounted from the frame second end portion 1 8 by a pair of frame members 104, 106 which extend vertically downwardly and substantially transverse to the second end portion 18. The frame members 104, 106 each include a respective longitudinally extending bore 108, 110. Axle 28 has a pair of opposed trunnions 112, 114 extending longitudinally outwardly therefrom and which extend through bores 108, 110. Interposed between the trunnion 11 2 and the frame member 104 (and between the trunnion 11 2 and frame member 106) is an annular bushing 11 6 which includes an elastomeric member made of rubber, or various synthetic rubber-like materials which have resilient properties.The means for mounting axle 28 on frame second end portion 1 8 described above is hereinafter referred to as a trunnion mounting means.

In the above described embodiment, each hydraulic cylinder 72a and 72b is connected to a respective trunnion 112, 114 with the connections being spaced longitudinally outwardly of the mounting for axle 28 on frame second end portion 1 8.

Figs. 3 and 4 illustrate a damping system embodiment 43' which is similar to the damping system embodiment 43, wherein identical structures are indicated by identical reference numerals, and wherein variations are indicated by the addition to the reference numerals of a prime symbol. The chief differences between the damping system embodiments stem from the different mounting of axle 28'. A damping means of the second example has one hydraulic cylinder 72' rather than the pair of hydraulic cylinders 72a, 72b. The hydraulic cylinder 72' is centrally located and pivotally connected directly to the axle 28'. This connection is by a rod 88'. Hydraulic cylinder 72' is otherwise constructed substantially the same as hydraulic cylinders 72a and 72b. The modified axle 28' is mounted as follows.

Axle 28' has a pair of flanges 120, 122 extending longitudinally outwardly therefrom.

The flange 1 20 has a pair of bores 124, 1 26 vertically extending therethrough, and the flange 1 22 has a bore 1 28 vertically extending therethrough. Fitted within each of the bores 124, 126, 128 is bushing 116' which includes an elastomeric member made of rubber or various synthetic rubber-like materials with resilient properties. As illustrated in Fig.

4, a pair of downwardly extending frame members 104', 106' are adapted to pass through bores 124, 126, 128. The mounting of axle 28a from the frame second end portion herein described is hereinafter referred to as a shear mounting means. The elastomeric member included by bushing 116' flexes, or deflects, upon movement of axle 28'.

Thus, both the trunnion mounting means of the embodiment 43 and the shear mounting means of embodiment 43' permit a small amount of resilient vertical movement of the respective axles 28 and 28', the movement being with respect to the frame second end portion 1 8. Such small amount of resilient movement is utilized by the damping means to oppose the variable load 1 2 imposed on the load carrying device 30.

The damping systems find particular application in use with lift trucks. It should be made obvious to those skilled in the art relating hereto that the damping systems will find other applications, such as the use in construction vehicles, e.g., loaders, wherein a varied load is applied to one end of the vehicle.

Referring to Fig. 1, when the frame front end portion 1 6 of lift truck 10 rises or lowers tdue to the vehicle traversing uneven terrain, the moment of force on the load 1 2 will tend to change and hence the mast element 32 will tend to rotate forwardly or backwardly about axis 42. This leads to a pressure increase or decrease responsive thereto in the rod ends of tilt cylinders 46a and 46b. This pressure variation is communicated through the conduit 63 into the rod ends 78 of cylinders 72a and 72b. The pressure variation causes the damping means 45 to rapidly move, or accelerate, the axle 28 up or down in directions substantially normal to the frame second end portion 1 8. The small amount of movement is, for example, on the order af up to about 0.5".The small amount of move ment is to be substantially similar to the amount of deflection in wheels 20.

As previously mentioned, the axle 28 is of substantial weight with respect to a load 1 2.

For example, the axle 28 may weight about 3,000-4,000 pounds (1,500-2,000 kg) where the vehicle is designed for a load capacity of about 10,000 to about 20,000 pounds (5,000-10,000 kg). As a result of such rapid, though small, movement of the heavy axle 28, the frame second end portion 18 is urged to oppose the movement of load force as it acts upon the frame first end portion 16. Thus the amplitude of the frame oscillations are reduced, or damped because accelerating axle 28 adds a component of force to the frame second end portion 1 8. As may be understood, the damping system of Figs. 3 and 4 functions in an analogous manner. Accordingly, the operator of the vehi cle has a much more comfortable ride thereon.

Claims (11)

1. A load carrying vehicle comprising a frame having first and second ends; an axle mounted on the second end; a load carrying device connected to the first end; sensing means for sensing variations in the force im posed on the first end by the load carrying device; and damping means for moving the axle and the frame second end up and down relatively to one another in response to the variations in the moment of force sensed by the sensing means to reduce oscillation of the vehicle frame.

2. A vehicle according to claim 1, wherein the axle is mounted on the second end of the frame by at least one frame member, and by an elastomeric bushing which connects the frame member to the axle and which permits limited relative up and down movement between the frame member and the axle.

3. A vehicle according to claim 2, further including at least one trunnion secured to the axle, the frame member being connected to the trunnion and the elastomeric bushing be ing interposed between the frame member and the trunnion.

4. A vehicle according to claim 2 or claim 3, wherein the damping means comprises at least one fluid cylinder, one end of which is connected to the frame and the other end of which is connected to the axle, the fluid cylinder also being connected to the sensing means

5. A vehicle according to claim 4, when dependant on claim 3, wherein the one end of the damping means fluid cylinder is connected to the frame second end and the other end of the cylinder is connected to the trunnion.

6. A vehicle according to claim 5, further including another trunnion secured to the axle, the another trunnion being connected to the frame second end by another frame member and by another elastomeric bushing which connects the another frame member to the another trunnion, and which permits limited relative vertical movement therebetween the damping means further including another fluid cylinder one end of which is connected to the another frame second end and the other end of which is connected to the another trunnion.

7. A vehicle according to claim 6, wherein the fluid cylinders are arranged on a longitudinal axis of the vehicle.

8. A vehicle according to claim 2, wherein the axle includes a plurality of flanges extending along a longitudinal axis of the vehicle; a plurality of frame members; and a plurality of bushings; the flanges being connected to the frame second end by the frame members and the elastomeric bushings, the bushings connecting the frame members to one or more of the flanges and permitting limited relative up and down movement therebetween, and the clamping means including a fluid cylinder one end of which is connected to the frame second end and the other end of which is pivoted to a central part of the axle.

9. A vehicle according to any of the preceding claims, wherein the sensing means comprises at least one fluid cylinder.

10. A vehicle according to claim 9, wherein the sensing means fluid cylinder is a tilt cylinder connected between the load carrying device and the frame first end.

11. A vehicle according to claim 9 or claim 10, wherein the sensing means further includes conduit means for communicating fluid between the sensing means fluid cylinder and the damping means.

1 2. A vehicle according to claim 1, substantially as described with reference to either of the examples illustrated in Figs. 1 and 2, or Figs. 3 and 4 of the accompanying drawings.

1 3. A lift truck according to any of the preceding claims, wherein the load carrying device is pivoted to the frame first end.