GB2055451A

GB2055451A - Drive Coupling for Transmitting Rotary Motion

Info

Publication number: GB2055451A
Application number: GB8020592A
Authority: GB
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1979-08-03
Filing date: 1980-06-24
Publication date: 1981-03-04
Also published as: GB2055451B

Abstract

A drive coupling for transmitting rotary motion between a pair of rotary members comprises first and second members one of which carries pins 17 off-set from but parallel to the axis of rotation of the coupling, the pins carrying weights 18 which are coupled to the other member by further pins 19 carrying abutments 20 engaged in slots 21 in the weights 18. The weights are biassed against outward movement by leaf springs 22 which are located against curved outer surfaces of the weights. The end of the springs engage an annular part which is a skirt portion of said other member and the springs have ears 24 intermediate their ends which locate in slots 25 formed in the side faces of the weights. <IMAGE>

Description

SPECIFICATION Drive Coupling Devices This invention relates to drive couplings of the kind intended to transmit rotary motion between a pair of rotary members, the coupling including a pivotal weight which under the action of varying centrifugal force moves against the action of a spring to alter the relative angular position of the members.

Such couplings have application in the drive connection between an engine driven member such as a shaft and the drive shaft of a fuel injection pump. The purpose of the coupling in this application is to adjust the timing of delivery of fuel by the pump in accordance with variation in the speed at which the pump is driven.

A known construction of the coupling comprises a first member which carries a pair of pins the axes of which extend parallel to but spaced from the axis of rotation of the device. The pins carry a pair of weights respectively the centres of mass of the weights being off set from the axes of the pins. A second member is provided and this carries a further pair of pins which carry slide blocks engaging within slots respectively formed in the weights. The axes of the further pair of pins are off set from the axes of the first mentioned pair of pins whereby as the weights move outwardly relative angular movement about the axis of the device will take place between the members. Leaf springs are carried by the weights respectively and these oppose the outward movement of the weights.The springs are of arcuate form and are positioned between the weights and the inner surface of an annular portion which surrounds the weight and is formed as part of or is connected to one of the members.

It has been the practice to secure as by bolts, one end of the spring to the associated weight.

This involves machining the weight to produce a flat surface to receive the end of the spring. The mass of the weight is therefore reduced and in addition the effective length of the spring is reduced since it is only that portion which lies beyond the machined surface which can act as a spring. Moreover, in use, the spring is highly stressed in the region of said surface.

The object of the invention is to provide a drive coupling of the kind specified in a simple and convenient form.

According to the invention a drive coupling of the kind specified comprises a first member carrying a pin extending parallel to but spaced from the axis of rotation of the coupling, a weight pivotally mounted about said pin with its centre of mass off-set therefrom a second member spaced from said first member with the weight disposed therebetween, an abutment on the second member and located within a slot in the weight, an annular portion surrounding said weight and an arcuate leaf spring having its ends engaging the internal surface of said annular portion, said leaf spring defining intermediate its ends, a pair of ears which are located within slots respectively formed in the side faces of the weight, the surface of the weight which is presented to the internal surface of said portion being curved and the curved surface of the weight and the internal surface of said portion having a smaller radius of curvature than the spring, the arrangement being such that as the speed at which the coupling rotates increases, the weight will move outwardly against the action of the spring to alter the relative angular setting of the first and second members, the radius of curvature of the spring decreasing as the weight moves outwardly.

An example of a drive coupling in accordance with the invention will now be described with reference to the accompanying drawings in which: Figure 1 is a sectional side elevation of the coupling taken on the line BB of Figure 2; Figure 2 is a sectional end elevation on the line AA of Figure 1; and Figure 3 is a part sectional view to an enlarged scale, on the line CC of Figure 2.

Referring to the drawings the coupling comprises a first member 10 having a boss portion 11 and an integral flange portion 12. The flange portion and boss portion are provided with shaped bores whereby the member can be secured to the drive shaft of a fuel injection pump.

A second member 13 is provided and this is of generally cup shaped form the base wall of which is provided with a central aperture through which extends the boss portion 11. Moreover the member 13 is provided with an outwardly extending flange 14 whereby it can be secured to a part which is driven by an associated engine for example, a geared wheel. The two members can move angularly relative to each other about the rotary axis of the device, the two members being held in assembly relationship by means of washers mounted on the boss 11 and held in position by a circlip 1 6.

The flange 12 carries a pair of pins 1 7 the axes of which extend parallel to the axis of rotation of the device, the pins being diametrically disposed relative to each other and offset from the axis of rotation of the device. Each pin carries an arcuate weight 18. The centres of mass of the weights are off-set from the pins 1 7 and conveniently the weights are provided with bearing sleeves surrounding the pins 17.

The base wall of the member 13 carries a further pair of pins 19 and each pin 19 carries an abutment 20 which is of square shaped form and which is located within a slot 21 formed in the weights at a position adjacent their pivot axes.

As the weights move outwardly under the action of centrifugal force, the members 10 and 13 will be moved angularly relative to each other about the axis of rotation of the device thereby in use affecting the timing of delivery of the fuel injection pump.

The outward movement of the weights is opposed by a pair of springs respectively and as shown in Figure 2, the springs which are referenced 22, are leaf springs which are located in the generally annular space disposed between the outer curved surfaces of the weights 18 and the inner surface of the skirt of the member 13.

The springs have a radius of curvature which is greater than the radii of curvature of the aforesaid outer surfaces of the weights and the inner surface of the skirt of the member 13. The free ends of the springs bear against the inner surface of the portion 23 and the springs engage intermediate their ends, the curved surfaces of the weights 1 8. The springs are retained in position relative to the weights by a pair of ears 24 which extend outwardly from the springs and which are bent so that they are located within recesses 25 formed in the side faces of the weights. This method of retention ensures that the minimum necessary amount of material is removed from the weights to provide the necessary location of the springs and in addition, no undesirable stress regions are created in the springs themselves.

As the weights move outwardly there will be a change in the curvature of the spring and therefore a small relative movement between the ends of the spring and the internal surface of the skirt of the member 13.

Claims

1. A drive coupling for transmitting rotary motion between a pair of rotary members comprising a first member, said pin extending parallel to but spaced from the axis of rotation of the drive coupling, a weight pivotally mounted about said pin with its centre of mass off-set therefrom, a second member spaced from said first member with the weight disposed therebetween, an abutment on the second member and located within a slot in the weight, an annular portion surrounding said weight and an arcuate leaf spring having its ends engaging the internal surface of said annular portion, said leaf spring defining intermediate its ends, a pair of ears which are located within slots respectively formed in the side faces of the weight, the surface of the weight which is presented to the internal surface of said portion being curved and the curved surface of the weight and the internal surface of said portion having a smaller radius of curvature than the spring, the arrangement being such that as the speed at which the coupling rotates increases, the weight will move outwardly against the action of the spring to alter the relative angular setting of the first and second members, the radius of curvature of the spring decreasing as the weight moves outwardly.

2. A coupling according to Claim 1, in which said annular portion comprises a skirt portion forming part of said second member.

3. A drive coupling for transmitting rotary motion between a pair of rotary members comprising the combination and arrangement of parts substantially as hereinbefore described with reference to the accompanying drawings.