GB2087977A

GB2087977A - Bearing arrangement or a telescopic cylinder

Info

Publication number: GB2087977A
Application number: GB8134004A
Authority: GB
Original assignee: Partek Oy AB
Current assignee: Partek Oy AB
Priority date: 1980-11-11
Filing date: 1981-11-11
Publication date: 1982-06-03
Also published as: DE3142687A1; FI61950B; SE8106365L; FI61950C

Abstract

A bearing arrangement for a telescopic cylinder of a tipping device for a vehicle, said cylinder comprising a plurality of cylinder tubes (2A, 2B) which are mounted axially slideably within each other pairwise by means of two bearing surfaces (5a, 6a) located between the cylinder tubes in each pair of cylinders. Both bearing surfaces are provided on the inner surface (2a) of the outer cylinder tube (2A) close to the mouth of the tube to remain at a constant distance from each other during a stroke. The outer surface (2b) of the inner cylinder tube (2B) is machined to form a sliding surface for said bearing surfaces. Due to this, the inner surface of the outer cylinder tube need not be machined to form a sliding surface and this increases the dimensional accuracy of the bearing arrangement and improves the stability of the telescopic cylinder. <IMAGE>

Description

SPECIFICATION Bearing arrangement for a telescopic cylinder The present invention relates to a bearing arrangement for a telescopic cyclinder, particularly for a tipping device.

In a tipping device for emptying the loading space of a vehicle, a hydraulic cylinder providing a long stroke is generally required. For this reason the cylinder is made as a telescopic construction comprising a plurality of cylinder tubes which are mounted axially slideably within each other pairwise by means of two bearing surfaces located between the cylinder tubes in each pair of tubes at an axial distance from each other. It is previously known to mount the tubes coaxially within each other so that in each pair the upper part of the outer cylinder tube is, on the inner surface of the tube, provided with a first bearing surface and the lower part of the inner cylinder tube is, on the outer surface of the tube, provided with a second bearing surface by means of which transverse stresses exerted on the tubes are absorbed.In this case the first bearing surface slides during a stroke relative to the outer surface of the inner cylinder tube and the second bearing surface slides relative to the inner surface of the outer cylinder tube.

A disadvantage associated with the known bearing arrangement is the necessity to machine the inner cylindrical surface of the outer tube which cannot be carried out at reasonable costs with a sufficient precision as regards bending situations to which the cylinder tubes can be subjected to in use. The poor dimensional accuracy due to the required machining of the inner surface results in great plays and poor tipping stability as well as great deformations and, because of them, great risks of leakage in the bearings. In addition, internal machining cannot provide a satisfactory tubular sliding surface and, consequently, results in rapid wear.

In order to improve the tipping stability, one might easily think of compensating the relatively great plays in each cylinder tube pair by positioning both bearing surfaces still farther away from each other in the axial direction of the cylinder tubes. However, this is limited by the limited length of the cylinder tubes and, in the known construction, the bearing surfaces are already positioned as close as possible, on the one hand, to the upper end of the outer cylinder tube and, on the other hand, to the lower end of the inner cylinder tube.

The object of the present invention is to provide a bearing arrangement for a telescopic cylinder of e.g. a tipping device which eliminates the abovementioned disadvantages and permits a firmer mounting in a simple way. Thus, according to the invention, there is provided a bearing arrangement for a telescopic cyclinder having an outer tube, and an inner tube mounted axially slidably therein, said arrangement comprising two axially spaced bearing surfaces located between the tubes, wherein both bearing surfaces are arranged on the inner surface of the outer tube adjacent the same end thereof and are in slidable engagement with the outer surface of the inner tube.

The invention is based on the idea that a better stability can be achieved in the bearing arrangement of a telescopic cylinder by positioning the bearing surfaces closer to each other and by arranging both bearing surfaces on the same cylinder tube, i.e. on the outer cylinder tube. Owing to this, the inner surface of the outer cylinder tube need not at all be machined to form a sliding surface due to which a higher precision of dimensioning and smaller plays are obtained. The small plays lead to smaller deformations when transverse stresses act on the bearing arrangement and, consequently, to a better tipping stability and smaller risks of leakage.The bearing surfaces are simply machinable with a high precision even in the event that they are formed as fixed rings directly on the outer cylinder tube, instead of loose attachment rings, because both rings can be located close to the mouth of the cylinder tube. Because both bearing surfaces are located within the same continuous cylinder tube, the rigidity of the entire cylinder is utilized.

An advantage of the invention will now be described by way of example and with reference to the accompanying drawings in which: Figure 1 is an axial section of a bearing arrangement for a telescopic cylinder in accordance with the invention; and Figures 2 and 3 illustrate two cooperating cylinder tubes spaced apart from each other.

Fig. 1 illustrates a hydraulic telescopic cylinder 1 of a tipping device of a vehicle which cylinder comprises a plurality of cylinder tubes 2 positioned coaxially within each other. Between each pair of cylinder tubes are provided bearings 3 so that the cylinder tubes are axially slideable on each other. The outermost cylinder tube is fastened on a common support plate 4.

As shown in Fig. 2, each bearing 3 comprises two bearing rings 5 and 6 fastened on the inner surface 2a of the outer cylinder tube 2A of a pair by means of threads. A flexible intermediate sleeve 7 is positioned between the rings to maintain the axial distance between the rings during the stroke of the cylinder tubes. Each ring forms a cylindrical bearing surface 5a and 6a, respectively. The outer surface 2b of the inner cylinder tube 2b of the pair is machined to form a sliding surface. To the outside of the lower end of the inner cylinder tube 2B is fastened a retaining ring 8 which limits axial movement of the tube and does not engage the inner surface 2a of the outer cylinder tube 2A.

It will be noted that both bearing surfaces 5a, 6a included in the bearing are fastened to the same cylinder tube, i.e. on the outer cylinder tube 2A, while the inner cylinder tube is provided for this bearing with an outer sliding surface 2b only.

The bearing surfaces remain stationary during the stroke of the cylinder tube 2B. At the end of the stroke the support reaction forces pass through both bearing surfaces. Due to such a construction, only the cylindrical outer surfaces of the cylinder tubes of the telescopic cylinder need be machined, while the inner surfaces, which are difficult to machine with a sufficient precision, need not at all be machined to form bearing surfaces. The dimentional accuracy of the bearing arrangement is improved, and small tolerances can be used which increases the stability.

The drawings and the description related thereto are only intended to illustrate one embodiment of the invention. In its details a bearing arrangement in accordance with the invention may vary considerably. Thus, it is possible to machine the bearing surfaces 5a and 6a directly in a cylinder tube, in which case the location of both bearing surfaces close to the mouth of the cylinder tube permits the machining of the bearing surfaces to precise dimensions without any major difficulties.

Claims

1. A bearing arrangement for a telescopic cylinder having an outer tube, and an inner tube mounted axially slidably therein, said arrangement comprising two axially spaced bearing surfaces located between the tubes, wherein both bearing surfaces are arranged on the inner surface of the outer tube adjacent the same end thereof and are in slidable engagement with the outer surface of the inner tube.

2. An arrangement as claimed in claim 1 wherein the bearing surfaces consist of rings fastened on the inner surface of the outer tube.

3. An arrangement as claimed in claim 2, wherein between the rings is provided an intermediate sleeve which maintains the distance between the rings during relative movement of the tubes.

4. An arrangement as claimed in claim 1 wherein the bearing surfaces consist of rings machined on the inner surface of the outer tube.

5. A bearing arrangement for a telescopic cylinder, substantially as hereinbefore described with reference to the accompanying drawings.