This invention relates to a selector mechanism, especially though not exclusively for use in actuating an electric switch device of the kind incorporating a series isolator, and the object of the invention is to provide a" simple form of selector mechanism capable of selectively operating in two different modes, utilising the same operation of a common actuator- According to the invention such a selector mechanism comprises an actuating member movable under the control of the actuator, a pair of links pivotally connected at one end to the actuating member, and each carrying at a position spaced from said end a projection engaging in a respective slot in an operating member, and a selector device operable to restrain one or other of the projections from moving along its respective slot, such that, on movement of the actuator, the operating member is caused to move in one or other direction, depending upon which of the projections is restrained from movement relative to the member, the other projection being free to slide along its respective slot.

The operating member may itself comprise a device required to be actuated under the control of the selector mechanism, or it may be coupled to such a

device, possibly through one or more further links. Thus, movement of the operating member may be employed to actuate, either directly or through an intermediate link, a movable conducting member of an interrupter/isolator assembly to cause it to engage either an isolator contact or an earth contact, the interrupter/isolator assembly being, for example, as described in United Kingdom Patent Application No. 8416825 (2143090). The actuating member and the operating member are preferably both pivotable about respective axes. The selector device is preferably also pivotable, and has a surface capable of engaging the projections in different angular positions of the device so as to restrain one or other of the projections in dependence upon the position of the device. The slots preferably terminate in transverse recesses in which the projections, conveniently in the form of rollers, are alternatively retainable by said surface, being thereby prevented from movement along the respective slot.

The actuator may be manually operable, and may, for example, comprise a handle connected or connectable to a rotatable shaft, carrying a lever coupled by means of a connecting link to the actuating member, although the means for moving the actuating member can alternatively take any other suitable form.

The invention will be further explained by describing, by way of example, with reference to Figures 1 and 2 of the accompanying schematic drawings, one selector mechanism in accordance with the invention for operating a switch device of the kind having an isolator position.

In the drawings Figure 1 represents a side view of the mechanism in diagrammatic form to illustrate its manner of operation, and Figure 2 represents an end view of the mechanism.

Thus referring to the drawings, a shaft 1,

pivotably supported in a framework F, carries a U-shaped bracket 2 into which can be fitted an operating handle shown in part at 3 in Figure 1. A lever 4, fixed to the shaft 1, is pivotably coupled to a link 5, which is, in turn, pivotably coupled to a further lever 6 mounted for rotation on a shaft 7 as indicated by the arrow 7'. Downward movement of the handle 3 through approximately 90 causes the link 5 to move to the left (in the view shown in Figure 1), this causing the lever 6 to rotate in the anti-clockwise direction. A pair of links 8, 9 are pivotably attached to the lever 6 and therefore also move to the left as the lever rotates. An output lever 11, is mounted on a shaft 12, and comprises two parallel plates 11' 11" (Fig 2) each of which has a pair of generally straight slots 13, 14, terminating at the ends furthest from the lever 6 with transverse recesses 13A, 14A. The ends of the links 8, 9 remote from the lever 6 are fixed to shafts 15, 16 ^" respectively, each carrying at their ends rollers 17, 18 which engage within corresponding ones of the slots 13, 14.

A selector 19 rotatably supported on the shaft 12 between the output lever plates 11 ' and 11" and can be rotated relative to the shaft in an anticlockwise direction through about 70° from the position shown in Figure 1 , by means of a suitable control device such as a bowden-type cable or other mechanical linkage (not shown) .

In the neutral or "OFF" position of the output lever, as shown in Figure 1, the rollers 17, 18 are located at the recessed ends of the slots 13, 14. Now, with the selector 19 in the position shown, if the handle 3 is moved downwards the links 8, 9 will also move to the left as previously explained. The rollers 18 on the link 9 are held within the respective recesses 14A by the operative surface of the selector 19 and, as a result, the output lever 11 will

rotate in the clockwise direction and, as the selector 19 is not interfering with the rollers 17 on the link 8, these will just idle along the respective slots 13. The plates 11' and 11" of the output lever 11 carry between them a spindle 21 which passes through a drive link 22, so that as the output lever rotates the drive link moves downwards. This link can be arranged to operate a switch mechanism as described in the aforesaid Patent Application No. 8416825, to cause a movable conducting member of the switch to engage an isolator contact, for example.

However if, with the output lever in the "OFF" position, the selector 19 is rotated through approximately 70 in the anticlockwise direction, the rollers 17 of the link 8 will be restrained by the operative surface of the selector, and the rollers 18 of the link 9 will be free to move along the respective slots 14. Consequently when the links 8, 9 are moved to the left on downward movement of the handle 3, the output lever 11 will rotate in the anticlockwise direction and move the drive link 22 upwards, so causing the conductor bar of the switch mechanism to move to the "earth" position. The shaft 1 to which the handle 3 can be connected conveniently carries a cam 23 having a depression into which a spring loaded roller 24 is urged when the handle is in the raised "OFF" position thereby ensuring that the remainder of the mechanism is held securely in the "OFF" position until the lever is positively actuated, this resulting in the compression of the spring 25.

Although the lever 6 has been shown as being operated by a handle and link mechanism it will be appreciated that other methods of achieving the required rotation of the lever can alternatively be employed.

Moreover although the selector mechanism, as above described, is concerned with the operation of a switch mechanism it could also be used to advantage for other purposes where the same movement of an actuating member is required to produce two different modes of operation.