GB2096953A

GB2096953A - Front fork for motorcycles

Info

Publication number: GB2096953A
Application number: GB8210309A
Authority: GB
Original assignee: Showa Seisakusho Co Ltd; Showa Manufacturing Co Ltd
Current assignee: Showa Corp; Showa Manufacturing Co Ltd
Priority date: 1981-04-17
Filing date: 1982-04-07
Publication date: 1982-10-27
Also published as: JPS57166990U; DE3213904A1; FR2504082A1; BR8202222A; GB2096953B

Abstract

In a front fork for motorcycles and the like a pair of guide bushes 13a, 13b in sliding contact with a fork tube 5 are fixed at a fixed spacing inside an enlarged diameter length 2a at the lower end of a bottom tube 2 which supports the front axle. <IMAGE>

Description

SPECIFICATION Front fork for motorcycles This invention relates to front forks for motorcycles and the like.

In prior constructions of front forks for motorcycles, as shown in Figures 1 and 2 of the accompanying drawings, a fork tube 5, to which handle bars 4 are secured by a pair of brackets 3 and 3' at the upper end is slidably fitted in a bottom tube 2, carrying at its lower end the front axle 1. In order to reduce the friction between the bottom tube 2 and fork tube 5, as seen in Figure 2, an annular groove 6 is provided on the outer periphery of the fork tube 5 and a guide bush 7 is fitted and secured in the groove 6 so that the outer surface of the guide bush 7 may slide on the inner surface of the bottom tube 2 and an annular region 8 of increased diameter is provided at the upper end of the bottom tube 2 in which a guide bush 9 is fixed so that the inner surface of the bush 9 may slide on the outer surface of the fork tube 5.

In order to prevent oil from leaking from between the bottom tube 2 and fork tube 5 and to hold the guide bush 9 in position, a circlip 12 is fitted through an oil seal 10 and seal spacer 11 at the upper end of the bottom tube 2. In addition, a buffer mechanism (not shown) is provided below the fork tube 5.

Since the front fork is slightly inclined to the vertical as seen in Figure 1 it is therefore normally subjected to lateral force. When the operational load is added and the distance D between the guide bushes 7 and 9 becomes longer, owing to the telescopic action, larger loads will be applied to the guide bushes 7 and 9 and these bushes and their co-operating parts will tend to wear. Since the point of application of the lateral force to the fork tube 5 varies with the longitudinal position of the fork tube 5, the guide bushes will receive most wear and therefore the performance and life of the buffer will deteriorate.

According to the present invention, a plurality of guide bushes are provided within which the fork tube slides and which are fixed at a fixed spacing inside the bottom tube.

An example of construction in accordance with the invention will now be described with reference to Figure 3 of the accompanying drawings, which is a longitudinal sectional view.

As shown in the drawing, a bottom tube 2 is provided with an increased diameter length 2a towards the end into which a fork tube 5 extends and guide bushes 1 3a and 1 3b are fitted at both ends of the length 2a and are held at a fixed spacing by circlips 1 4a and 1 4b. Instead of the circlips, a collar 1 5 may be inserted between them to fix the guide bushes as shown by the broken lines in Figure 3.

Thus, even at the time of maximum extension of the bottom tube 2 and fork tube 5, the distance D between the guide bushes 1 3a and 1 3b will be always constant and, therefore, even if a lateral force is applied by the load, the friction will be lower and therefore the wear will be less. Further, the internal surface of the bottom tube 2 may be finished precisely only for the shorter distance of fixing the guide bushes 1 3a and 1 3b.

In the illustrated embodiment, the increased diameter part 2a is provided in the end portion of the bottom tube 2. However, so long as the lower guide bush 1 4b slidably engages with the lower end of the fork tube 5 at the point of maximum extension, the increased diameter part may be provided toward the middle of the tube 2 or two or more guide bushes may be provided.

As just described, in a construction according to the present invention, despite the simple arrangement, the partial wear of the guide bushes and the co-operating parts of the fork tube can be reduced and therefore a front fork of longer life can be obtained.

1. A front fork for motorcycles and the iike comprising a bottom tube carrying a front axle at its lower end and a fork tube fitted into the bottom tube and having handle bars fixed at its upper end and also including a plurality of guide bushes within which the fork tube slides and which are fixed at a fixed spacing inside the bottom tube.

2. A front fork according to claim 1 wherein the guide bushes are fixed with circlips.

3. A front fork according to claim 1 wherein the guide bushes are fixed with a collar interposed between them.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Front fork for motorcycles This invention relates to front forks for motorcycles and the like. In prior constructions of front forks for motorcycles, as shown in Figures 1 and 2 of the accompanying drawings, a fork tube 5, to which handle bars 4 are secured by a pair of brackets 3 and 3' at the upper end is slidably fitted in a bottom tube 2, carrying at its lower end the front axle 1. In order to reduce the friction between the bottom tube 2 and fork tube 5, as seen in Figure 2, an annular groove 6 is provided on the outer periphery of the fork tube 5 and a guide bush 7 is fitted and secured in the groove 6 so that the outer surface of the guide bush 7 may slide on the inner surface of the bottom tube 2 and an annular region 8 of increased diameter is provided at the upper end of the bottom tube 2 in which a guide bush 9 is fixed so that the inner surface of the bush 9 may slide on the outer surface of the fork tube 5. In order to prevent oil from leaking from between the bottom tube 2 and fork tube 5 and to hold the guide bush 9 in position, a circlip 12 is fitted through an oil seal 10 and seal spacer 11 at the upper end of the bottom tube 2. In addition, a buffer mechanism (not shown) is provided below the fork tube 5. Since the front fork is slightly inclined to the vertical as seen in Figure 1 it is therefore normally subjected to lateral force. When the operational load is added and the distance D between the guide bushes 7 and 9 becomes longer, owing to the telescopic action, larger loads will be applied to the guide bushes 7 and 9 and these bushes and their co-operating parts will tend to wear. Since the point of application of the lateral force to the fork tube 5 varies with the longitudinal position of the fork tube 5, the guide bushes will receive most wear and therefore the performance and life of the buffer will deteriorate. According to the present invention, a plurality of guide bushes are provided within which the fork tube slides and which are fixed at a fixed spacing inside the bottom tube. An example of construction in accordance with the invention will now be described with reference to Figure 3 of the accompanying drawings, which is a longitudinal sectional view. As shown in the drawing, a bottom tube 2 is provided with an increased diameter length 2a towards the end into which a fork tube 5 extends and guide bushes 1 3a and 1 3b are fitted at both ends of the length 2a and are held at a fixed spacing by circlips 1 4a and 1 4b. Instead of the circlips, a collar 1 5 may be inserted between them to fix the guide bushes as shown by the broken lines in Figure 3. Thus, even at the time of maximum extension of the bottom tube 2 and fork tube 5, the distance D between the guide bushes 1 3a and 1 3b will be always constant and, therefore, even if a lateral force is applied by the load, the friction will be lower and therefore the wear will be less. Further, the internal surface of the bottom tube 2 may be finished precisely only for the shorter distance of fixing the guide bushes 1 3a and 1 3b. In the illustrated embodiment, the increased diameter part 2a is provided in the end portion of the bottom tube 2. However, so long as the lower guide bush 1 4b slidably engages with the lower end of the fork tube 5 at the point of maximum extension, the increased diameter part may be provided toward the middle of the tube 2 or two or more guide bushes may be provided. As just described, in a construction according to the present invention, despite the simple arrangement, the partial wear of the guide bushes and the co-operating parts of the fork tube can be reduced and therefore a front fork of longer life can be obtained. CLAIMS