GB2135517A - Operating mechanism for limit switches - Google Patents

Abstract

An operating mechanism comprises a lever arm (16) mounted for pivotal movement and operatively connected to an operating device which comprises a switch actuating element (58). The operating device comprises a body (32) providing a central cavity (34), within which there is mounted an operating member (38), which is itself provided with a central cavity (46), a portion (47) at least of which is of non-circular shape in cross-section. Mounted within the cavity (46) is a further operating member (48), comprising a head (50) which is a sliding fit within said portion (47). The operating member (48) is resiliently urged from a depressed to an advanced position, and is guided for such movement in any one of at least three orientations, carrying at its lower end the switch actuating element (58). The operating member (48), when in its first orientation, is moved from its advanced to its depressed position only by anticlockwise movement of the lever arm (16), when in its second orientation is so moved only on clockwise movement of the arm, and when in its third orientation is so moved by movement of the arm in either direction. Preferably a semi-cylindrical portion (26) of a spindle carrying the lever arm (16) moves the operating member (48) and is accommodated in a recess (54) of the head (50) when movement of the lever arm (16) without resulting switch actuation is desired (e.g., in clockwise lever arm movement with the illustrated orientation of the operating member). <IMAGE>

Description

SPECIFICATION Improvements relating to limit switches This invention is concerned with improvements relating to limit switches, particularly of the kind (hereinafter referred to as being of the kind specified) known as roller lever operated limit switches.

A switch of the kind specified is operated by a mechanism which comprises a lever arm mounted for pivotal movement, and which carries at its outer end a roller, the lever arm being operatively connected to an operating device which comprises an operating element to actuate the switch mechanism. It is generally desired that the arm be spring-urged into a rest position, and it may be desired that the switch be actuated by movement of the arm in one but not the other direction, or in the other, but not the one direction, or in both directions.

Difficulty has hereinbefore been encountered in the provision of an operating mechanism for a switch of the kind specified which can readily be changed from one make of operation to another, and it is one of the various objects of this invention to provide such a mechanism.

According to this invention there is provided an operating mechanism for a switch of the kind specified comprising a body, an operating member mounted within the body and which is resiliently urged from a depressed to an advanced position, the operating member being guided for such movement in any one of three orientations and carrying a switch operating element adapted to operate the switch on movement of the operating member to its depressed position in any one of said of three orientations.

In the use of the operating mechanism, the operating member, when in its first orientation, is adapted to be moved from its advanced to its depresed position by movement of a lever arm operatively connected to the operating member in one but not the other direction, when in its second orientation is adapted to be moved from its advanced to its depressed position on movement of the arm in the other but not said one direction, and when in its third orientation is adapted to be moved from its advanced to its depressed position by movement of the arm in either direction.

Preferably the operating mechanism comprises an actuating member connected or adapted to be connected to the lever arm and which is so constructed and arranged to depress the operating member.

(a) when the operating member is in its first orientation, on movement in one direction but not the other direction; (b) when the operating member is in its second orientation, on movement in said other but not said one direction; or (c) when the operating member is in its third orientation, on movement in both directions.

Preferably the mechanism comprises a second operating member mounted within the body and which is resiliently urged independently of the first operating member from a depressed to an advanced position.

Preferably the first operating member is mounted for movement within a cavity of the second operating member.

Preferably the second operating member provides means to guide the first operating member for rectilinear movement throughout the range of its normal movement between its advanced and depressed positions. Preferably the first operating member is capable of rectilinear movement beyond its depressed position into a position in which its orientation relative to the second operating member maybe changed, subsequent to which on return to its depressed position the first operating member again guides the first operating member for rectilinear movement from its depressed to its advanced position.

In this manner the arm will be urged to return to its rest position by the first operating member whether or not movement from its rest position has caused actuation of the switch.

This invention also provides a limit switch of the kind specified, comprising an operating mechanism as set out in any of the preceding seven paragraphs.

There will now be given a detailed description, to be read with reference to the accompanying drawings, of an operating mechanism for a switch of the kind specified, which has been selected for the purposes of illustrating the present invention by way of example.

In the accompanying drawings, FIGURE 1 is an end elevation of said switch operating mechanism; FIGURE 2 is a longitudinal cross-sectional view of the operating mechanism taken on the line 2-2 of Figure 1; FIGURE 3 is a transverse cross-sectional view, taken on the line 3-3 of Figure 2; FIGURES 3a and 3b are views illustrating in side elevation alternative orientations of an operating member of the operating mechanism; FIGURE 4a is a side elevatiori illustrating certain operative parts of the switch mechanism, seen as viewed in the direction of the arrow 4 in Figure 2; FIGURE 4b is a side elevation illustrating certain other operative parts of the switch mechanism, seen as viewed in the direction of the arrow 4 Figure 2; and FIGURES 5, 5a and Sb are views illustrating in plan the alternative orientations of said operating member.

The operating mechanism which is the preferred embodiment of this invention is particularly for a limit switch of the kind known as a roller lever operated limit switch, and comprises a generally rectangular housing 6, conveniently of metal, provided with a generally rectangular cavity 8. Extending from one side of the housing 6 is a generally cylindrical stem 10, which is provided with a bore 1 2 which opens into the cavity 8.

Located in the bore 12 is a bush 13, through which extends a spindle 14, an external end portion of which being connected to an operating arm 16, which carries an operating roller 1 8.

The spindle 14 is provided with a circumferential groove, within which is located a resilient seal 19.

The spindle 14 is provided with a second circumferential groove 21, into which a pin 22 driven through the housing extends, restraining axial movement of the spindle relative to the housing from the position shown in Figure 2.

A forward end portion 26 of the spindle within the cavity 8 is of hollow, generally semi-cylindrical construction comprising radially opposite diametrical side edges 28 and 30, said portion affording an actuating member of the operating mechanism. A projection 1 5 extends from the body towards the longitudinal axis of the bore 12, engagement of the forward end portion 26 therewith limiting the degree of permitted rotation of the spindle 14 and preventing the pin 22 from being moved from the groove 21, and the spindle from the housing (see Figure 4b).

Mounted in the cavity 8 is a hollow plastics body 32, provided on one side with a tongue 31 engagable in a keyway in the body, and which is provided with a central cavity 34, and recesses 36 in diametrically opposites of an upper edge thereof.

Mounted within the cavity 34 is an operating member 38, which is generally circular in crosssection, and which is provided with semi-circular recesses 40 in diametrically opposite side of an upper edge thereof. A spring 42 acts between an underside of the operating member 38 and a lower lip 31 of the body to resiliently urge the operating member 38 into an advanced position (as shown in Figure 2).

The operating member 38 is provided with a central cavity 46, from which an aperture 47 extends through an upper part of the member, as is shown in Figure 2. The aperture 47 is of non circular shape in cross-section, and in the preferred embodiment is octagonal, as is shown in Figure 5.

Mounted within the body 32 is a further operating member 48, comprising a head 50 which is also octagonal in cross-section, being a sliding fit within the aperture 47, and an elongate hollow stem 52. One side of the head is recessed as at 54.

A lower end portion of the stem 52 is provided with a circlip 55, which limits upward movement of the second operating member, under the influence of a spring 56, and which defines an advanced position of the member 48.

Protruding from the lower end of the stem 52 is a switch actuating element 58, retained by pin 60 which extends diametrically through the stem 52, being held in position by the circlip 55, and through an axial slot of the element 58, said switch actuating element being urged to an advanced position by a spring 64 within the stem 52, the element 58 absorbing any unwanted overtravel.

In use, the housing 6 is bolted to the housing of the switch, into which the switch actuating element is adapted to protrude.

Operation of the switch of which the preferred embodiment of this invention forms part will now be described, with the operating member 48 in the orientation shown in Figures 2 and 3.

On movement of the operating arm in the direction A, Figure 3, causing the spindle 14 to rotate in an anti-clockwise direction about its longitudinal axis, the side edge 28 of the forward end portion of the spindle, at spaced locations, engages the walls of the operating member 38 in spaced regions bounding the recesses 40 thereof, and depresses the operating member against the action of the spring 42 from its advanced position (see Figure 4). Said side edge 28 also engages the head 50 of the operating member 48 (Figure 3) and depresses the operating member 48 from its advanced position against the action of the spring 56. The switch actuating element 58 is caused to protrude and actuate the switch mechanism (not shown).

The head 50 is provided with a central elevated portion 51 which, towards the end of the movement of the forward end portion of the spindle, is engaged by the side edge 28 or 30 to produce a slightly larger terminal movement of the second operating member 48.

On removal of the force on the operating arm 16, both the springs 42 and 56 urge the arm to its rest position, shown in Figure 3.

On movement of the arm 1 6 in the opposite direction B, causing movement of the spindle 14 in a clockwise direction about its longitudinal axis, whilst the side edge 30 of said forward end portion 26 of the spindle engage the operating member 38 in wall portions thereof defining the recesses 40, the side edge 30 does not engage the head 50 of the operating member 48, but passes into the recess 54. Thus although the operating member 38 is depressed from its advanced position, providing spring return of the operating arm to its rest position, such movement of the arm does not cause actuation of the switch mechanism.

By depression of the operating member 48 beyond the position to which it is depressed by the spindle 14, the head 50 may be moved beyond the aperture 47 into the central cavity 46, within which the member 48 may be rotated about its longitudinal axis. The profiling of the central cavity 46 of the operating member 38, and the profiling of the head 50 of the operating member 48, permits the operating member 48 to be returned into the aperture 47 in any one of four orientations, although two of these orientations are functionally identical. Thus from the orientation shown in Figures 2, 3 and 5, by rotation of the operating member 48 through 1 8or, the operating member may be moved to a second orientation, shown in Figures 3a and 5a, in which it is depressed by arcuate movement of the spindle 14 in the clockwise, but not the anticlockwise direction, and by rotation of the operating member 48 through 900, the operating member may be moved to a third orientation (as shown in Figure 3a and Sb) in which movement of the spindle 14 in either direction causes movement of the operating member from its advanced position and hence actuation of the switch mechanism.

Thus, simply by removing the body 32 from the housing 6, together with the operating members 38 and 48, and fully depressing the operating member 48 relative to the operating member 38, conveniently with the aid of a screwdriver, the operating member 48 may be rotated to whatever orientation is desired, before re-assembly of the body 32 in the housing.

The operating mechanism described and illustrated above may be mounted on a switch housing in any one of four orientations, permitting actuation of the switch in the manner desired.

When the body 32 and operating members 38 and 48 are removed from the cavity 8, movement of the operating member 38 is limited by engagement of catch portions 43 within upper end portions of siots 44, 45 in the wall of the body, and by engagement of the circlip 55 with the underside of the body 32.

Claims (9)

1. An operating mechanism for a switch of the kind specified comprising a body, an operating member mounted within the body and which is resiliently urged from a depressed to an advanced position, the operating member being guided for such movement in any one of three orientations and carrying a switch operating element adapted to operate the switch on movement of the operating member to its depressed position in any one of said of three orientations.

2. An operating mechanism according to Claim 1 wherein the operating member, when in its first orientation, is adapted to be moved from its advanced to its depressed position by movement of a lever arm operatively connected to the operating member in one but not the other direction, when in its second orientation is adapted to be moved from its advanced to its depressed position on movement of the arm in the other but not said one direction, and when in its third orientation is adapted to be moved from its advanced to its depressed position by movement of the arm in either direction.

3. An operating mechanism according to one of Claims 1 and 2 wherein the operating mechanism comprises an actuating member connected or adapted to be connected to the lever arm and which is so constructed and arranged to depress the operating member, (a) when the operating member is in its first orientation, on movement in one direction but not the other direction; (b) when the operating member is in its second orientation, on movement in said other but not said one direction; or (c) when the operating member is in its third orientation, on movement in both directions.

4. An operating mechanism according to any one of the preceding claims comprising a second operating member mounted within the body and which is resiliently urged independently of the first operating member from a depressed to an advanced position.

5. An operating mechanism according to Claim 4 wherein the first operating member is mounted for movement within a cavity of the second operating member.

6. An operating mechanism according to Claim 5 wherein the second operating member provides means to guide the first operating member for rectilinear movement throughout the range of its normal movement between its advanced and depressed positions.

7. An operating mechanism according to any one of Claims 4 to 6 wherein the first operating member is capable of rectilinear movement beyond its depressed position into a position in which its orientation relative to the second operating member maybe changed, subsequent to which on return to its depressed position the first operating member again guides the first operating member for rectilinear movement from its depressed to its advanced position.

8. A limit switch of the kind specified, comprising an operating mechanism according to any one of the preceding claims.

9. Operating mechanism for a limit switch of the kind specified, constructed and arranged substantially as hereinbefore described with reference to the accompanying drawings.

1 0. Any novel feature or novel combination of features disclosed herein and/or shown in the accompanying drawings.