AU740374B2 - Improvements in and relating to hydraulically driven wheel and brake assemblies and wheeled elevating work platforms - Google Patents

Description

d l P/00/011 Regulation 3.2

AUSTRALIA

Patents Act 1990

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C

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Invention Title: "IMPROVEMENTS IN AND RELATING TO HYDRAULICALLY DRIVEN WHEEL AND BRAKE ASSEMBLIES AND WHEELED ELEVATING WORK PLATFORMS" The following statement is a full description of this invention, including the best method of performing it known to us: -1 A IMPROVEMENTS IN AND RELATING TO HYDRAULICALLY DRIVEN WHEEL AND BRAKE ASSEMBLIES AND WHEELED ELEVATING WORK PLATFORMS One aspect of this invention relates to a brake for preventing a wheel which is substantially static from rotating. In particular this aspect of the invention relates to wheels which are actuated by hydraulic motors.

The invention also particularly relates to wheels of self-propelled elevating work platforms, often referred to as cherry pickers, or similar vehicles.

Another aspect of this invention particularly relates to driving wheel arrangements of wheeled elevating work platforms or similar vehicles.

ee **Yet another aspect of this invention relates to an arrangement of nondriving wheels of a wheeled elevating work platform.

Hydraulic motors are commonly used to drive wheels of vehicles. Included in this set of vehicles are wheeled elevating work platforms, often called cherry pickers. The hydraulic motor may act as a brake for the vehicle.

One disadvantage of this arrangement is that when the vehicle is substantially stationary these hydraulic motors often allow an amount of creep of the wheels. This allows the vehicle to move a little when it is preferred that the vehicle be completely stationery. This is particularly S: undesirable for a vehicle such as a cherry picker where an operator is in an elevating position, and stability is important.

A standard technique is to use conventional disc or drum brakes. These work by forcing a brake pad against a disc or drum. Large forces must be supplied to the pad, requiring relatively large and expensive brake cylinders or similar. Frequent service is required to ensure that slippage does not occur. This adds to the cost of running the vehicle.

Conventional wheeled elevating work platforms have a wheel arrangement comprising two wheels at one end, usually the driving wheels, and one castor wheel at the other end. This arrangement has the disadvantage that on rough ground the work platform may be unstable.

It is an object to come some way in overcoming the abovementioned disadvantage relating to brakes for hydraulic motor actuated wheels, or at least to provide the public with a useful choice.

It is a further object to come some way to overcoming the abovementioned disadvantage relating to wheel arrangements, or at least to provide the public with a useful choice.

Other objects of this invention will become apparent from the following description.

According to one aspect of the invention there is provided an hydraulically driven wheel and brake assembly comprising: 10 an hydraulic motorfor driving a wheel; at least one plate, for securement to the wheel, having the plurality of engageable features; at least one engaging means for engaging the engageable features; loo ~at least one actuating means for actuating the at least one engaging S 15 means between a first and a second position, wherein, when the engaging means is in the first position, it engages at least one surface of at least one engageable feature so that the wheel is prevented from rotating and wherein, when in the second position, the engaging means does not engage an engageable feature.

According to another aspect there is provided a vehicle, such as a wheeled elevating work platform, including the hydraulically driven wheel and brake wherein the actuating means is mounted on the vehicle and the plate is mounted to a wheel driven by the hydraulic motor such that in the first 2 5 position the engaging means engages at least one engageable feature.

1.

-3- Brief descriDtion of the drawinas Embodiments of the invention are now described by way of example only with reference to the drawings in which: Figure 1 a: shows a side view of a brake.

Figure 1 b: Figure 2: Figure 3: Figure 4: Figure 5: Figure 6: Figure 7: Figure 8 shows a top view of the brake shown in figure 1 a.

shows an exploded view of the brake and wheel arrangement shown in figures 1 a and 1 b.

shows a cut-away section of the actuating means shown in figures la and lb.

is a schematic view of an hydraulic actuation system for the actuating means.

shows a side view of a wheeled elevating work platform.

shows a plan view of the platform shown in figure shows a front view of the platform shown in figure shows a rear view of the platform shown in figure Detailed description of the invention Referring to figures 1 to 4 there is shown a brake 1 for preventing a substantially static wheel from rotating. In figure la there is shown an engageable plate 2 which, in use, is fixed to a wheel 21 (shown in figure The engageable plate 2 has a plurality of radially spaced holes 3 drilled through it, although other engageable features such as transverse protrusions may be provided. There is also provided a pin 4 of a diameter slightly smaller than the holes 3 in the plate 2. Pin 4 may be driven in the axial direction of piston actuator 6. The housing of -4actuator 6 is mounted in use onto part of the elevating work platform by means of a mounting bracket 7.

The piston actuator is mounted onto a part of the vehicle that does not rotate by means of a mounting plate 7. By these means the pin 4 is held in one axis with respect to the vehicle and may be advanced towards the engageable plate 2.

When the engageable plate 2 is at a rotated position such that one of the holes 3 is in line with the pin 4, the pin advances through the hole when biased and thereby positively engages the engageable plate 2. As the 10 engageable plate 2 is fixed to the wheel 21, the wheel is prevented from ••*rotating.

One preferred arrangement for actuating the pin will now be described with reference to figure 3. A piston 31 is provided inside the piston housing 37, ;dividing it into two regions 33 and 34. The region 34 contains hydraulic 15 fluid which enters the housing through inlet port 35. Region 33 contains a coil spring 32. The spring biases the piston 31 which is connected to the Spin 4 so that the pin is biased to extend out of the housing 37 into a first position when the fluid pressure at inlet port 35 is below a certain level.

Hydraulic fluid may be pumped through port 35 forcing the piston back to 20 retract the pin 4 into the housing 37. When hydraulic fluid is allowed to leave the region 34, the spring 32 forces the piston 31 to extend the pin 4 into the first position. When the pin is so extended, it pushes against the engageable plate. When one of the holes comes in line with the pin, which may happen as the wheeled elevating platform or vehicle settles, the pin 4 slides into or through one of the holes 3 and so a positive engagement with the engageable plate is made.

Figure 4 is a schematic diagram of a preferred embodiment of the invention wherein a brake system is provided in combination with an hydraulic wheel actuating system. There are provided two inlet/outlet lines 41 and 42 which supply/remove fluid to drive the hydraulic wheel motor 48 and the brake 6.

The hydraulic wheel motor 48 may be used to power the wheel clockwise or anticlockwise. The power and direction of the operation of the hydraulic wheel motor is determined by the pressure difference across hydraulic inlet/ outlet lines 41 and 42.

Between these two inlet/outlet lines is connected a valve 43. The operation of this valve 43 is such that if there is a pressure difference across the hydraulic inlet/outlet lines 41 and 42, hydraulic fluid is supplied via the hydraulic line 44 to the piston actuator 6. In particular the hydraulic fluid is supplied to the region 34 of the piston actuator to drive piston 31 against spring 32 to retract pin 4. Also provided is a fluid outlet 45 from region 33.

o 10 The operation of the valve 43 and piston actuator 6 is such that if the *°°hydraulic wheel motor 48 is in use, to rotate the wheel, the pin 4 is retracted from the engageable plate 2. When not in use pin 4 is biased by spring 32 to engage with disc 2. Thereby, the brake 6 and hydraulic wheel motor 48 are synchronised.

15 Although an hydraulic embodiment has been described it will be appreciated that pin 4 may be retracted by electromechanical means etc.

Another embodiment of the invention consists in a wheel arrangement for a wheeled elevating work platform. The preferred embodiment of this wheeled elevating work platform has a set of two in-line pivotally S• 20 connected front wheels to replace each single front wheel of a conventional wheeled elevating work platform. These wheels 52 and 53 are attached by axles 65 and 66 to a subchassis 56. This subchassis is attached to main chassis 68 by an axle 55. This axle allows the subchassis 56 to rotate in the plane of the wheels 52 and 53. This provides that the wheeled elevating work platform is more stable on rough ground. It also allows that if both wheels are driven, more traction will be provided by the two wheels than by a single wheel.

Another aspect of the preferred embodiment is a dual castor wheel system.

Wheels 60 and 60a are connected to supports 64 and 64a which are rotatable about a vertical axis with respect to chassis 62. The two castor wheels 60 and 60a are located near the ends of the chassis 62 and the length of chassis 62 is chosen so that the two castor wheels 69 are separated by a width which is nearly equal to the width of the wheeled elevating work platform. This arrangement provides greater stability than a single controlly located castor wheel.

The driving wheels 52 and 53 of the preferred embodiment 50 are driven and statically braked by the hydraulic motor wheel and brake system described above and shown in figure 4. Both of the wheels 52 and 53, and the wheels on the opposite side, may be driven and braked by the above system or only one wheel on each side may be driven and braked by this system. Also, one wheel may be driven and the other braked. It is preferred that both wheels on either side are each driven by an individual hydraulic motor and braked by an individual brake.

One advantage of the brake system is that only a relatively slight force on the pin 4 is required for positive engagement with the plate. Therefore only a relatively small and cheap actuator is required. Another advantage is that due to the spring arrangement an hydraulic failure will cause the wheel to be locked preventing the wheel from rotating. This is safer than an arrangement where the force braking the wheel is supplied by hydraulic means where a failure allows the wheel to roll.

One advantage of the wheel arrangement is that the wheeled elevating work platform will be more stable on rough ground.

20 Another advantage is that the weight of the wheeled elevating work platform will be spread over a greater wheel surface. This is advantageous on soft ground.

Where in the foregoing description reference has been made to integers or components having known equivalents then such equivalents are herein incorporated as if individually set forth.

Although this invention has been described by way of example it is to be appreciated that improvements and/or modifications may be made thereto without departing from the scope of the present invention as defined in the appended claims.

Claims (13)

1. An hydraulically driven wheel and brake assembly comprising: an hydraulic motor for driving a wheel; at least one plate, for securement to the wheel, having a plurality of engageable features; at least one engaging means for engaging the engageable features; at least one actuating means for actuating the at least one engaging means between a first and a second position, wherein, when the engaging means is in the first position, it engages at least one surface of at least one "*"engageable feature so that the wheel is prevented from rotating and 10 wherein, when in the second position, the engaging means does not engage an engageable feature.

2. An assembly as claimed in claim 1 wherein the actuating means includes an hydraulic cylinder.

3. An assembly as claimed in claim 2 including valve means which receives fluid from hydraulic lines driving the hydraulic motor and supplies Sofluid to the actuating means when there is a pressure differential between the hydraulic lines so as to urge the engaging means into the second position.

4. An assembly as claimed in claim 3 wherein the valve is a shuttle valve.

An assembly as claimed in any one of the preceding claims wherein the actuating means includes biasing means which biases the engaging means towards the first position.

6. An assembly as claimed in claim 5 wherein the hydraulic cylinder of the at least one actuating means works against the biasing means to move the engaging means to the second position when driven.

7. An assembly as claimed in any one of the preceding claims wherein the engageable features lie substantially within the periphery of the plate.

8. An assembly as claimed in any one of the preceding claims wherein the engageable features have surfaces transverse to the plate. 8

9. An assembly as claimed in any one of the preceding claims wherein the engaging means moves transversely with respect to the plate.

An assembly as claimed in any one of the preceding claims wherein the engageable features comprise a plurality of holes through the plate.

11. An assembly as claimed in any one of the preceding claims wherein the engaging means is a pin. 9ooo ooo

12. A vehicle including an assembly as claimed in any one of the preceding claims wherein the actuating means is mounted on the vehicle and the plate is mounted to a wheel driven by the hydraulic motor such that in the first position the engaging means engages at least one engageable feature.

13. An hydraulically driven wheel and brake assembly substantially as herein described with reference to figures la to 4 of the accompanying drawings. DATED this Third day of September 2001. A J J P SMITH LIMITED by its Patent Attorneys FISHER ADAMS KELLY