GB2243344A - Reducing noise of tipping ram - Google Patents

Abstract

A truck has a hydraulic lifting ram 4. The ram has a main cylinder 5 and a cylindrical ram casing 7, mounted on top of the ram, and connected to the load container 1 by pivot pins 11 located in trunnions 8. A buffer 25 of e.g. synthetic rubber is mounted on the cylinder 5 via a metal band 26, and serves to reduce noise caused by the impact of casing 7 on cylinder 5. <IMAGE>

Description

RAMS The invention relates to rams, and particularly, though not exclusively to hydraulic tipping rams for use in heavy trucks.

In heavy trucks, such as those used for carrying loads of earth, sand or other heavy flowable or particulate loads, it is commonly known to employ either a flat load bed or a high sided load container, possibly with one or more hinged gates at the rear or side of the load container. Such trucks generally have a chassis and the load container is generally hinged onto the chassis at one end or side enabling the container to be tipped relative to the chassis thus facilitating emptying of the load. Tipping of the load container or load bed is commonly accomplished by extension of a hydraulic ram which is pivotally connected between one end or side of the load bed and the truck chassis.

The ram has surrounding casing and a widespread problem with such rams is that of excessive noise and rattling owing to knocking of the ram casing against the main cylinder, encountered during movement of the vehicle, when the ram is in the retracted position. This noise is inherent in the design of known ram casings, and the problem generally becomes worse as bearing surfaces become warn.

Known attempts at solving this problem include placing a rubber tyre around the base of the ram, or wrapping cloths around the base of the ram, or jamming cloths between the main ram and the casing when in the retracted position. These makeshift methods have proved largely ineffective.

The problem can be solved for a limited period by welding on additional components to take up the play between the ram and casing, but in due course the components wear and the problem returns.

The invention aims to provide a more successful and more permanent solution to the problem.

The invention provides a noise reduction device for use with a ram cylinder and a surrounding casing, the device comprising a buffer device shaped to fit between the cylinder and the casing.

The buffer may have a first face arranged to contact a surface of the cylinder, and a second face arranged to contact the casing, the second face being at an inclined angle to the first face.

The first face may have an area which is greater than the area of the second face.

The buffer may comprise a continuous ring or loop.

Alternatively the buffer may comprise a strip arranged to be wrapped around the cylinder.

The noise reduction device preferably includes means arranged to compress the buffer against the cylinder.

The buffer may be made of elastic and/or plastic material. The preferred material is synthetic rubber.

Protrusions, grooves or a combination thereof may be provided on one or more surfaces of the buffer to prevent or reduce slippage of the buffer with respect to the cylinder and/or casing.

The invention includes a ram fitted with a noise reduction device according to the invention.

The invention includes a truck or other vehicle provided with a ram according to the invention.

By way of example, a specific embodiment of the invention will now be described, with reference to the accompanying drawings, in which Figure 1 is a side view of a truck according to the invention; and Figure 2 shows in cross-section, the noise reduction device of the truck shown in Figure 1.

Figure 1 shows a side elevation of a truck with a load container 1 hinged at one end of a chassis 2 by a pivot 3 and having a hydraulic lifting ram 4. The load container 1 is shown in an unloading position, in which the ram 4 is fully extended, and in a transport or parked position in which the ram is fully retracted. Owing to the long length of the load container, which can be of the order of 10 metres, such hydraulic rams are commonly designed to extend to a length of up to four or five times their retracted length. Such extension is accommodated in the design of the ram but providing a series of ram cylinders having progressively smaller bores, such that each upper ram cylinder may slide into its connected supporting cylinder which has a larger diameter bore.Nevertheless, even when retracted, extendable rams of this type still occupy a length which is of substantial proportion of the vehicle's height.

All of the concentrically nested upper cylinders of the ram 4 slide into a main base cylinder 5 which is originally connected -to a tank 10 for hydraulic fluid, the tank being pivotally mounted on a support 6 fixed to the chassis 2. The main cylinder 5 also accommodates hydraulic connection points for hydraulic lines from the truck chassis 2, to pressurise the ram for extension.

The combined ram and support is necessarily mounted so that the lower end of the combination does not extend substantially below the vehicle chassis 2, because the space here is occupied by the vehicle's transmission.

Also, encroachment of the ram on the ground clearance space below the vehicle may cause a fouling of the ram when the vehicle is driven over rough ground.

When fully retracted, the main cylinder of the ram is housed inside a cylindrical ram casing 7, which is connected at its lower end to the load container 1 by pivot pins 11 located in trunion mountings 8. The axis of the pins 11 extend in a direction transverse to the length of the load container 1. The uppermost cylinder of the extendable ram 4 is connected to the uppermost part of the ram casing 7. Thus, the casing 7 performs the dual functions of connecting the uppermost cylinder of the ram to the load container 1, and also of protecting the ram cylinders from the elements or from damage during loading, when the ram is in the retracted position.

Figure 2 shows components of the ram in more detail. It will be seen that the casing 7 is surrounded by a collar 12 from which the pivot pins 11 project. A part spherical bearing surface 23 of the lower part of the ram casing 7 engages with a complimentary shaped surface 24 on the collar 12. These mating bearing surfaces 23, 24 enable the container 1 to tilt slightly in the transverse direction with respect to the ram 4.

This tilting may, for example, occur when the vehicle is standing on uneven ground, causing the chassis 2 to twist slightly.

The surfaces 23 and 24 are held in contact by a ring 13 which is welded to the casing 7, and which rests on two diametrically spaced apart projections on the top of the collar 12, one of which can be seen in dotted lines in Figure 2, indicated by the reference numeral 14.

The upper surface of the projection 14 is curved, to accommodate rocking movement of the collar 12 with respect to the ring 13, as the bearing surfaces 23 and 24 slide over one another.

Noise may be caused by the impact of the casing 7 against the main ram cylinder 5, as the whole assembly vibrates with normal vehicle movements. With older vehicles, the problem increases, owing to wear. Not only is there some wearing of the surfaces 23 and 24, but there is also a more serious problem caused by wearing of the ring 13 and projections 14. When the components 13 and 14 wear, the casing 7 drops slightly from the position shown in Figure 2. Because of the angle of the faces 23 and 24, even a slight drop of the casing 7 produces a significant gap between the surfaces 23 and 24, which in the prior art arrangement, brings about considerable impact and rattling.

The preferred embodiment of the present invention comprises a noise reduction device in the form of a buffer 25 which is positioned between the lower end of the ram casing and the ram cylinder, and a constrictive fastening device 26 to fasten the device to the ram cylinder. The noise reduction device has a face 30 which is angled with respect to the main axis of the ram cylinder and which makes contact with the ram casing when the ram is fully retracted. The insert also has a surface 27 which is parallel to and in contact with the main cylinder surface.

Because of the angled face 30, one size of noise reduction device 25 may be manufactured, which nevertheless can be fitted to vehicles having varying sizes of gaps 31 between the ram 5 and casing 7. The device 25 can be firmly wedged into position as shown, to take up all the play between the components and hence reduce noise. The buffer also counteracts any tendency for the casing 7 to drop from the position is shown, and helps to maintain contact between the surfaces 23 and 24.

As the vehicle is operated, and the casing 7 lifts to the upper position shown in Figure 1, and then returns to the position shown in Figure 2, any tendency for the device 25 to be pushed down the ram 5 is counteracted by the fastening device 26 and the fact that downward movement of the casing 7 causes a corresponding increase in the grip exerted on the cylinder 5 by the device 25, owing to the wedge shape.

The fastening device 26 comprises a metal band located in a groove in the device 25, the band being capable of being tightened by turning a threaded member 28 in the manner of a jubilee clip.

The buffer device 25 is made from synthetic rubber.

The device 25 may be manufactured in the form of an unbroken loop which can be fitted over the cylinder ram 5 during the assembly stage of the ram. In an alternative embodiment, the device 25 may have an inside diameter which is less than the outside diameter of the ram cylinder, such that the loop needs to be stretched in order to fit over the cylinder. In place, the contracting tension of the loop keeps the insert in place by friction between the inner surfaces 27 of the loop and the corresponding outer surface of the cylinder 5, and in this case the fastening device 26 may be optional.

In the preferred embodiment shown however, the device 25 is manufactured in the form of a flexible strip, or collar, which is wrapped around the main cylinder 5, and the fastening device 26 is required to keep the device 25 in place. This embodiment can be assembled during manufacture, but can also be fitted subsequently to existing trucks. Long lengths of strip of appropriate profile may be manufactured, which can then be cut to any desired length dependent upon the circumference of the ram in question.

The embodiment shown has a large surface area in contact with the ram cylinder 5, thus increasing friction and further reducing the risk of slippage down the ram cylinder as the casing is lowered. This feature may be further enhanced by the inclusion of locating grooves, projections or combinations thereof, on the device 25 and/or the components 5 or 7. Another advantage is that the angled face which contacts the casing as it is lowered, allows some slippage of the casing over the device 25 and automatically centralises the casing with respect to the device and ram cylinder.

The buffer device shown in Figure 2 can readily be replaced by a new buffer device if the device becomes damaged or worn.

Other configurations are possible and the buffer device shown in Figure 2 can be utilised with other types of ram and casing. For example, some trucks have a separate tank 10 which is connected to the main cylinder 5 by hose connections.

The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims (13)

1. A noise reduction device for use with a ram cylinder and a surrounding casing, the device comprising a buffer device shaped to fit between the cylinder and the casing.

2. A noise reduction device as claimed in Claim 1, in which the buffer device has a first face arranged to contact a surface of the cylinder, and a second face arranged to contact the casing, the second face being at an inclined angle to the first face.

3. A noise reduction device as claimed in Claim 2, in which the first face has an area which is greater than the area of the second face.

4. A noise reduction device as claimed in any one of the preceding Claims, in which the buffer device comprises a continuous ring or loop.

5. A noise reduction device as claimed in any one of Claim 1 to 3, in which the buffer device comprises a strip arranged to be wrapped around the cylinder.

6. A noise reduction device as claimed in any one of the preceding Claims, including means arranged to compress the buffer device against the cylinder.

7. A noise reduction device as claimed in any one of the preceding Claims, in which the buffer device is made of elastic and/or plastic material.

8. A noise reduction device as claimed in any one of Claims 1 to 6, in which the buffer device is made of synthetic rubber.

9. A noise reduction device as claimed in any one of the preceding Claims in which protrusions, grooves or a combination thereof are provided on one or more surfaces of the buffer to prevent or reduce slippage of the buffer with respect to the cylinder and/or casing.

10. A noise reduction device constructed and arranged substantially as herein described, with reference to the accompanying drawings.

11. A ram having a cylinder and a surrounding casing, a noise reduction device as claimed in any one of the preceding Claims being fitted between the cylinder and the casing.

12. A vehicle fitted with a ram as claimed in Claim 11.

13. A vehicle as claimed in Claim 12, comprising a truck.