Speed Responsive Devices

Abstract

A speed responsive device including a pair of rotary members, a mass movable outwardly under the action of centrifugal force such outward movement of the mass imparting relative angular movement of the members and spring means for restraining outward movement of the mass. The spring means comprises a pair of coiled tension springs which are connected to a leaf spring engaging with an outer curved surface of the mass. The initial radius of curvature of the leaf spring is greater than that of the aforesaid surface and means is provided to limit the extension of the tension springs.

Description

This invention relates to speed responsive devices of the kind comprising a mass which is adapted to move outwardly under the action of centrifugal force, spring means for restraining such outward movement and means displaceable by said mass upon outward movement thereof.

In known devices of the kind specified the mass is provided with a curved outer surface around which and in close contact therewith, extends a rigid member. The rigid member at its ends is connected to a pair of springs respectively which constitute the spring means. With this arrangement the springs provide a single rate and it is an object of the present invention to provide such a device in a form in which the spring means has two rates.

According to the invention in a device of the kind specified the spring means comprises a leaf spring which engages an outer curved surface of the mass, the ends of the leaf spring engaging with a pair of coiled tension springs respectively and the initial radius of curvature of the leaf spring being greater than that of said surface and means to limit the extension of the tension springs.

One example of a speed responsive device in accordance with the invention will now be described with reference to the accompanying drawings in which :

FIG. 1 is a sectional side elevation of a device which acts as a coupling between a driving and a driven shaft of a fuel pumping apparatus,

FIG. 2 is a section on the line B--B of FIG. 1,

FIG. 3 is a sectional plan view on the line C--C of FIG. 2, and

FIG. 4 is a section on the line A--A of FIG. 1.

Referring to the drawings there is provided a cup-shaped member 10 which constitutes the outer casing of the device and which in use, is connected to a driving shaft (not shown). The open end of the cup-shaped member 10 is partly closed by an annular closure member 11 which is retained in position by a circlip 12 secured within a groove formed in the internal peripheral surface of the member 10. Located within the member 10 is an output member 13 which is provided with a central bore whereby the member can be mounted upon a driven shaft 14. The member 13 has a cylindrical outer surface which cooperates with the internal peripheral surface of the cup-shaped member 10 in a manner to constitute a bearing to allow limited relative angular movement between the members 10 and 13. The member 13 includes a disc portion from which extend in the direction of the base wall of the cup-shaped member 10, a pair of segmental portions 15 having opposed and substantially parallel surfaces 16 which define a slot 17.

Mounted within the slot 17 are a pair of masses 18 and these are guided for outward movement by the opposed surfaces 16. The end surface of each mass which is presented towards the base portion of the cup-shaped member 10 is provided with an inclined slot 19 and within the pair of slots thus defined are mounted a pair of pivotal followers 20 respectively, each follower being mounted about an associated pin 21 which is secured within the base portion of the cup-shaped housing 10.

The arrangement is such that as the masses move outwardly relative angular movement between the members 10 and 13 will occur. In use, the device serves to transmit rotary motion and the masses 18 are subjected to centrifugal force. In order to restrain the movement of the masses spring means is provided the form of the spring means best being seen from FIG. 4. Referring to this figure the outer surface of each mass 18 is curved and located against this surface is a leaf spring 22, the radius of curvature of the leaf spring in its unstressed state, being larger than that of the curved end surface of the associated mass. The member 13 is provided with a pair of bores 23, the bores extending substantially parallel to the surfaces 16. Each bore accommodates a coiled tension spring 24 and the ends of the springs are connected to the adjacent ends of the leaf springs 22. In operation, the initial outward movement of the masses 18 under the action of centrifugal force, is against the action of the coiled tension springs 24 but when the tension springs have extended so that the ends of the leaf springs abut against the internal peripheral surface of the cup-shaped member 10, further outward movement of the masses is against the action of the leaf springs.

It will be understood therefore that the spring means provides two effective rates thereby allowing different rates of relative angular movement of the members 10 and 13 depending upon the speed of rotation of the device. A device as described can be used for transmitting rotary motion between the drive shaft of a liquid fuel pump and a further shaft driven by an associated engine. In this case the device causes the timing of injection of fuel to vary in accordance with the speed at which the engine is driven.

Claims

Having thus described my invention what I claim is new and desire to secure by Letters Patent is:

1. A speed responsive device comprising a mass which is arranged to move outwardly under the action of centrifugal force, spring means for restraining such outward movement, and means displaceable by said mass upon outward movement thereof characterized in that the spring means comprises a leaf spring which engages an outer curved surface of the mass, the ends of the leaf spring engaging with a pair of coiled tension springs respectively and the initial radius of curvature of the leaf spring being greater than that of said surface and means to limit the extension of the tension springs.

2. A speed responsive device comprising a rotary input member and a rotary output member, a mass arranged to move outwardly under the action of centrifugal force, means coupling the members and operable upon outward and inward movement of the mass to effect relative angular movement of the members, a leaf spring engaging an outer curved surface of the mass, a pair of coiled tension springs coupled to the ends of the leaf spring respectively, the springs acting to restrain outward movement of the mass, and the initial radius of the leaf spring being greater than that of the curved surface of the mass.

3. A device as claimed in claim 2 including a further mass and a further leaf spring, the tension springs extending between said leaf springs.

4. A device as claimed in claim 3 including an extended portion on one of said members, said extended portion being positioned to limit the extension of said tension