GB1599179A

GB1599179A - Electric switch

Info

Publication number: GB1599179A
Application number: GB3288777A
Authority: GB
Original assignee: Arrow Hart Europe Ltd
Current assignee: Arrow Hart Europe Ltd
Priority date: 1977-08-05
Filing date: 1977-08-05
Publication date: 1981-09-30
Also published as: FR2399726B1; FR2399726A1

Description

(54) AN IMPROVED ELECTRIC SWITCH (71) We, ARROW-HART (EUROPE) LIMITED, a British Company of Plymbridge Road, Estover Plymouth, PL6 7PN, England, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to an electric switch.

According to the invention an electric switch comprises a housing, a movable, electrically-conducting connection element, first and second, spaced-apart switch contacts carried by the housing and electrically isolated from one another, and actuating means comprising a first camming element mounted for movement in first and second opposite directions within the housing to adjust the position of the connection element within the housing, and a second camming element carried by the housing and constrained against movement relative to the housing in said first and second directions, one of said camming elements being provided with a cam track having portions inclined to said first and second directions, and the other camming element comprising a cam follower which cooperates with, and is relatively movable with respect to, said cam track for moving the first camming element into and out of a first position, in which the connection element makes no electrical contact with either of said first or second switch contacts, a second position, in which the connection element makes electrical contact with said second switch contact, and a third position, in which the connection element makes electrical contact with said first switch contact but does not make electrical contact with said second switch contact.

Suitably, the cam track is arranged so that the first camming element is movable directly into said second position from each of said first and third position but is only movable directly out of said second position into one of said first and third positions.

Suitably the cam follower is resiliently urged against the base of the cam track which is provided with teeth to permit relative movement of the cam follower along the cam track in a given direction but not in the opposite direction.

Typically the first camming element is movable in said first direction, against resilient return means providing a return force in said second direction, to urge the first camming element towards one of its first or third positions. The switch may be provided with further resilient return means acting in the second direction and which come into operation when the first camming element is moved out of either of said first or third positions and is subsequently moved into said second position. Suitably a counteracting pressure has to be applied to the first camming element in the first direction to maintain the latter in its second position against the combined forces of the two resilient return means acting in said second direction.

Conveniently the cam track is provided on the first camming element and the cam follower is mounted in the housing for movement transversely of said first and second directions.

The invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 is a partly-sectioned view of an electric switch according to the invention, Figure 2 is a view of a cam track provided in the electric switch of Figure 1, and Figure 3 is a schematic perspective view showing the arrangement of the switch contacts and the connection element within the switch of Figures 1 and 2.

Figure 1 shows a push-button electric switch, generally designated by the reference numeral 1, comprising a substantially parallelepipedic casing 2 housing spaced-apart and electrically-isolated switch contacts 3a, 3b and 3c, and a reciprocable actuating member 4 carrying an electrically-conducting connection element 5 having four flexible legs 5a, 5b, Sc and 5d (see Figure 3). The member 4 can be moved into any one of three positions, namely a first operative position (the position shown in Figure 1) in which neither of the legs 5b, Sc contacts the switch contact contact 3b, 3c, respectively, so that the switch contact 3a is not electrically connected to either of the switch contacts 3b, 3c, this first operative position being at the limit of sliding of the actuating member 4 in a first sliding direction X; a second operative position (not shown) in which the legs 5a, 5b and Sc contact the switch contacts 3a, 3b and 3c, respectively, thereby electrically connecting switch contact 3a to the switch contacts 3b and 3c, this second operative position being at the limit of sliding of the actuating member 4 in a second sliding direction Y opposite to the direction X; and an intermediate, third operative position, in which the legs 5a and 5b contact the switch contacts 3a and 3b, respectively, thereby electrically connecting the the switch contact 3a to the switch contact 3b. A push-button 7 is fixed to the actuating member 4 and can be pressed against a counteracting force provided by a compression spring 8, positioned between the casing 2 and the actuating member 4 and which resiliently urges the actuating member 4 in the direction X towards its first operative position.

The casing 2 includes a side wall 9 having a recess 10 formed therein. A slot 11, extending transversely to the directions X and Y (i.e. perpendicular to the plane of Figure 1), passes completely through the side wall 9 and opens into the bottom 12 of the recess 10. A pin 13 having a shank 14 and an enlarged head portion 15 is located with its shank 14 received in the slot 11. The pin 13 is movable along the slot 11 in a transverse direction (i.e. perpendicular to the plane of Figure 1) and is retained in the slot by resilient means 16 secured to the bottom 12 of the recess 10 and pressing in the direction of the arrow A (see Figure 1) against the enlarged head portion 15 of the pin 13.

The free end of the shank 14 is received in a channel-section groove 17 (see Figure 2), having a bottom 18 and side walls 19 and 20, which is provided in the actuating member 4.

The groove 17 approximately follows a "Figure of 8" path and defines a cam track with respect to which the pin 13, acting as a cam follower, is relatively movable. The paths which can be taken by the pin 13 along the groove 17 are shown by arrows in Figure 2. It should of course be appreciated that the shank 14 can only move transversely in its slot 11 and that the relative movement of the shank 14 with respect to the groove 17 is brought about by the combined effect of the sliding of the member 4 in the directions X and Y and the transverse movement of the pin 13 in the slot 11.

In operation of the switch 1, the actuating member 4 initially occupies its first operative position with the shank 14 located at position I (see Figure 2) in the groove 17. On depression of the push button 7, the shank 14 is moved relatively along the groove 17 in the direction of the arrows to position IV. When the shank 14 is in position IV, the actuating member 4 is moved against a further spring (not shown) requiring an increased pressure to be applied to the push-button 7 to move the actuating member 4 into its second operative position and the shank 14 into position II. In order to retain the actuating member 4 in its second position it is necessary to keep pressure applied on the pushbutton 7 to counteract the force exerted by the spring 8 and the said further spring. If when the shank 14 is in either of its positions II or IV, the pressure on the push-button 7 is released, the shank 14 moves back into position III and the actuating member 4 is moved back into its third operative position.

The actuating member 4 is held in its third operative position because the shank 14 is retained by spring pressure of the spring 8 in a notch 21 in a member 22 which partly defines the groove 17.

In order to move the actuating member 4 out of its third operative position, pressure is again applied to the push button 7 causing the actuating member 4 to move in the direction Y and the shank 14 to move relatively along the groove 17 into position V. On continued movement of the actuating member 4 in the direction Y, the latter is moved against said further spring (not shown) requiring an increased pressure to be applied to the push-button 7 to move the actuating member 4 into its second operative position and the shank 14 into position II. As described previously, on release of the pressure on the push-button 7, the actuating member 4 returns to its third operative position and the shank 14 is moved relatively along the groove 17 to position III. If on the other hand, the pressure on the push-button 7 is released when the shank 14 is in position V, the spring 8 causes the actuating member 4 to be moved in the direction X back to its first operative position and the shank 14 to be moved relatively to position I.

It should of course be realised that in order to ensure that the shank 14 is able to move relative to the groove 17 into different operative positions, it is essential for the shank 14 to move into and out of its positions I, II and III in different directions. For this reason it is neccessary for portions of the cam track, defined by the groove 17, to be inclined to the directions X and Y.

In order further to encourage the shank to move relatively along the groove 17 in the desired path from one operative position to another operative position, of the actuating member 4, it is desirable to provide the bottom 18 of the groove 17 with teeth-like projections at critical parts of the cam track.

Each tooth-like projection consists of a "ramp" and a "drop", the free end of the shank 14 being movable in a direction up the "ramp" and down the "drop" but not in the opposite direction. In Figure 2, the "drops" have been indicated in dotted lines.

In the electric switch described above it will be appreciated that the actuating member 4 cannot be returned directly to its first operative position from its second operative position without first passing through its third operative position. In another embodiment of the invention the cam track could be modified as shown in dashed lines (the dashdot lines representing additional "drops") to enable the actuating member 4 to be returned directly to its first operative position from its second operative position. In this latter case, however, the actuating member 4 cannot be returned directly to its third operative position from its second operative position.

In other embodiments of the invention it is possible to mount a cam track in the casing 2 and to mount a cam follower on the actuating member 4. It is also possible to fix the cam track (or cam follower) in the casing 2 and to mount the actuating member 4 within the casing 2 so as to permit sliding movement of the member in the casing as well as turning movement of the actuating member 4 about an axis paralled to the direction of sliding.

Although this invention has been described with reference to a push-button electric switch, the invention is intended to embrace other types of electric switch, e.g. a pull switch.

Finally in the embodiment of the invention described the leg Sd of the connection element 5 makes no contact with any switch contact. Of course it should be realised that another switch contact could be provided if required to make contact with leg 5d.

WHAT WE CLAIM IS: 1. An electric switch comprising a housing, a movable, electrically-conducting connection element, first and second, spacedapart switch contacts carried by the housing and electrically isolated from one another, and actuating means comprising a first camming element mounted for movement in first and second opposite directions within the housing to adjust the position of the connection element within the housing, and a second camming element carried by the housing and constrained against movement relative to the housing in said first and second directions, one of said camming elements being provided with a cam track having portions inclined to said first and second directions and the other camming element comprising a cam follower which cooperates with, and is relatively movable with respect to, said cam track for moving the first camming element into and out of a first position, in which the connection element makes no electrical contact with either of said first or second switch contacts, a second position, in which- the connection element makes electrical'contact with said second switch contact, and a third position, in which the connection element makes electrical contact with said first switch contact but does not make electrical contact with said second switch contact.

2. An electric switch according to claim 1, in which the cam track is arranged so that the first camming element is movable directly into said second position from each of said first and third positions but is only movable directly out of said second position into one of said first and third positions.

3. An electric switch according to claim 1 or 2, in which the cam follower is resiliently urged against the base of the cam track which is provided with teeth to permit relative movement of the cam follower along the cam track in a given direction but not in the opposite direction.

4. An electric switch according to any one of the preceding claims, in which the cam track resembles a figure of 8, the cam follower being positioned at one end of the cam track when the first camming element is in its first position, at the opposite end of the cam track when the first camming element is in its second position, and at the cross-over point of the cam track when the first camming element is in its third position.

5. An electric switch according to any one of the preceding claims, in which the first camming element is movable in said first direction, against resilient return means providing a return force in said second direction, to urge the first camming element towards one of its first or third positions.

6. An electric switch according to claim 5, in which the switch is provided with further resilient return means acting in the second direction and which come into operation when the first camming element is moved out of either of said first or third positions and is subsequently moved into said second position.

7. An electric switch according to claim 6, in which a counteracting pressure has to be applied to the first camming element in the first direction to maintain the latter in its second position against the combined forces of the two resilient return means acting in said second direction.

8. An electric switch according to any one of the preceding claims, in which the cam track is provided on the first camming element and the cam follower is mounted in the housing for movement transversely of said first and second directions.

9. An electric switch according to any one of the preceding claims, in which the connection element also makes contact with the first switch contact when the first camm

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. "ramp" and down the "drop" but not in the opposite direction. In Figure 2, the "drops" have been indicated in dotted lines. In the electric switch described above it will be appreciated that the actuating member 4 cannot be returned directly to its first operative position from its second operative position without first passing through its third operative position. In another embodiment of the invention the cam track could be modified as shown in dashed lines (the dashdot lines representing additional "drops") to enable the actuating member 4 to be returned directly to its first operative position from its second operative position. In this latter case, however, the actuating member 4 cannot be returned directly to its third operative position from its second operative position. In other embodiments of the invention it is possible to mount a cam track in the casing 2 and to mount a cam follower on the actuating member 4. It is also possible to fix the cam track (or cam follower) in the casing 2 and to mount the actuating member 4 within the casing 2 so as to permit sliding movement of the member in the casing as well as turning movement of the actuating member 4 about an axis paralled to the direction of sliding. Although this invention has been described with reference to a push-button electric switch, the invention is intended to embrace other types of electric switch, e.g. a pull switch. Finally in the embodiment of the invention described the leg Sd of the connection element 5 makes no contact with any switch contact. Of course it should be realised that another switch contact could be provided if required to make contact with leg 5d. WHAT WE CLAIM IS:

1. An electric switch comprising a housing, a movable, electrically-conducting connection element, first and second, spacedapart switch contacts carried by the housing and electrically isolated from one another, and actuating means comprising a first camming element mounted for movement in first and second opposite directions within the housing to adjust the position of the connection element within the housing, and a second camming element carried by the housing and constrained against movement relative to the housing in said first and second directions, one of said camming elements being provided with a cam track having portions inclined to said first and second directions and the other camming element comprising a cam follower which cooperates with, and is relatively movable with respect to, said cam track for moving the first camming element into and out of a first position, in which the connection element makes no electrical contact with either of said first or second switch contacts, a second position, in which- the connection element makes electrical'contact with said second switch contact, and a third position, in which the connection element makes electrical contact with said first switch contact but does not make electrical contact with said second switch contact.

ing element is in its second position.

10. An electric switch according to any one of the preceding claims, including a third switch contact carried by the housing and electrically isolated from the first and second switch contacts, the third switch contact making contact with the connection element when the first camming element is in both its second and third positions.

11. An electric switch constructed and arranged substantially as herein described with reference to, and as illustrated in, Figures 1 to 3 of the accompanying drawings.