GB2328796A - A switch - Google Patents

Abstract

A switch (1) comprises an activation surface (3b) to which in use a user applies pressure to operate the switch (1), a spring (3) for providing a resisting force for resisting the user applied pressure and an adjuster (4) for adjusting the resisting force provided by the spring such that the user applied pressure required to operate the switch (1) is variable. In this manner the user may adjust the force required to operate the switch (1). The invention is particularly useful when used as a push-to-talk switch on a radio transceiver. The spring may be a spring arm the operable length of which is adjustable by the adjuster (4). Alternatively, the spring may be a coil spring disposed around an actuating rod of a pushbutton.

Description

A Switch This invention relates to a switch particularly, but not exclusively, a switch for an electronic device.

Switches are used in a multitude of applications for controlling functionality of devices. One such application of switch is that referred to in the radio communications field as push-to-talk switch or PIT.

The PTT switch is a switch used for activating a transmitter section of a radio transceiver. When depressed the user can speak and the speech is transmitted.

The nature of radio communication is such that the HT switch is operated with great frequency. Its affect on the user should not be under-estimated. It will affect the user's perceptions of the quality of the radio and will also cause fatigue if hard to depress. These factors are subjective and thus switches are design to provide a switch which will be tolerable to most users.

The invention seeks to provide a switch which is adjustable.

According to the invention there is provided a switch comprising an activation surface which in use a user applied pressure to operate the switch, a spring for providing a resting force for resisting the user applied pressure and user-operable adjuster for adjusting resisting force provided by the spring such that the user applied pressure required to operate the switch is variable.

In a first preferred embodiment the spring is a spring arm. In an alternative embodiment the spring is a coil spring. Both springs work in compression but in alternative arrangements the spring may be arranged to resist extension forces to operate the switch Where the spring is a spring arm the adjuster is arranged to vary the operable length of the spring arm. Preferably, the adjuster is a movable fulcrum.

Where the spring is a coil, the adjuster is arranged to vary a spring loading of the coil.

Preferably, the adjuster is provided with detents to allow discrete adjustment.

Where the spring is a coil the adjuster is preferably operable by rotation of a cam surface. Preferably, the cam surface is provided with detents for engaging at least one end of the coil spring.

A specific embodiment of the invention will now be described by way of example only with reference to the drawings in which: Figure 1 is a perspective view of a switch in accordance with a first embodiment of the invention prior to assembly; Figure 2 is a perspective view of the switch assembled into a radio transceiver; Figure 3(a) is a partial cross-section of the assembled switch and Figure 3(b) is a plan view of the switch; Figure 4(a) is a partial cross-section of an alternative embodiment of the switch; Figure 4(b) is a plan view of a button of the switch shown in Fig 4(a); and Figure 4(c) is a perspective view of an actuation rod and button assembled to a coil spring.

With reference to figure 1, a switching arrangement 1 comprises a push-to-make switch 2, a spring arm 3 and an adjuster 4. In this figure for the sake of clarity the arrangement 1 is shown prior to assembly into a blind rectangular location hole 5.

The arrangement is shown in assembled form in figure 2 and it is used to control transmissions from a radio transceiver 6.

The push-to-make switch 2 is a microswitch soldered to a printed-circuit board (not shown) and thus to a microprocessor which controls they functionality of the radio 6. It includes a button 2a which when depressed results in the switching operation by the bridging of two internal contacts( not shown).

The spring arm 3 is formed from plastics material which is resiliently deformable. It has a planar upper surface 3a including a knurled pad 3b for facilitating actuation by a user. At one end of the spring arm is an integrally formed pivot 3 c. At the other end is formed a retaining flange 3 d. The lower surface is a shallow dish bounded by a downwardly directed wall 3e. That part of the wall which extends along the length of the spring arm is provided (on each side) with detents 3f.

As is shown in figure 3a, the spring arm 3 has formed on the lower surface a downwardly directed projection 3 g. From this figure it can also be seen that the spring arm 3 is located in the location hole 5 by the pivot 3c and the flange 3d which engage suitably shaped recesses formed in the side walls defining the location hole 5. This location is achieved by flexing the arm and pressing the pivot 3c and flange into the recesses.

The resilience of the arm then causes it to spring back into shape urging the pivot 3c and flange 3d into retention in the recesses. It will also be seen that the location is such that the projection 3g is immediately adjacent the button 2a of the switch 2.

The adjuster 4 is also formed from plastics material. It comprises a sliding saddle having a generally planar seat 4a and two end walls 4b extending upwardly from the seat 4a.

The end walls 4b have milled upper edges 4c and the junction between the walls and the seat 4a includes upwardly directed pips 4d.

The seat 4a is provided by a hemispherical cut-out to provide clearance as the adjuster approaches the switch 2.

As can be seen from figure 3a, the adjuster 4 is located between the spring arm 3 and the location hole face. It is able to slide along the face when a user pushes using the milled upper edges 4c. During this sliding motion the pips 4d will engage the detents 3f of the spring arm 3.

This will provide a locking action to the adjustment.

It will be appreciated from figure 3 a, in particular, that in moving the adjuster 4 the moment arm of any force applied by the user via the pad 3b will be varied because the adjuster provides a variable position fulcrum.

Thus the ease with which the arm and hence the switch can be depressed will be varied. In the final detent the switch is prevented from operation.

Figure 4 shows an alternative embodiment where adjustment is provided by rotational movement rather than longitudinal movement as in the first embodiment.

In this arrangement, the switch 2 is substantially identical to the microswitch of the first embodiment and is thus numbered with same reference number.

The arrangement also includes an actuation rod 7 of plastics material having disposed at one end an actuation button 8 which is integrally formed in the same molding operation. The button 8 includes a circumferentially extending retaining flange 8a which engages a retaining lip 10a to retain the actuation rod 7 in a cavity 9 defined by an enclosure 10. (The enclosure 10 may define an "open" enclosure by being formed as a cage).

The lower end of the rod extends out of the enclosure via a hole 10b which allows actuation of the button of the switch 2 when the rod is fully depressed.

The button 8 is provided with an axially inwardly extending cam surface 8b. Disposed between the cam surface 8b and the inner wall of the enclosure 10 is a coil spring 11 co-axially located about the rod- & - This spring acts to urge the flange 8a into contact with the retaining lip 10a and the inner end of the rod 8 away form the button of the switch 2.

Thus the spring 11 provides the spring action which the user must overcome by application of pressure to the button 8 before the switch 2 is depressed.

As is shown in figure 4 b a screw slot 8c is provided in the outer face of the button 8. By the use of this slot the button 8 may be rotated. This causes the relative passage of an arm ila of the spring 11 along the cam surface 8b compressing the spring the other end lib being held captive in a hole 10c in the enclosure 10. The cam surface 8b is provided with detents 8d which capture and retain the spring arm ila to maintain the adjustment until further user applied rotation. The final detent locks the switch to prevent actuation.

As the compression of the spring is increased the resistance it provides to user actuation of the switch arrangement increases, and vice versa.

In the described embodiments the switch is a microswitch. Other forms of switch could be used such as rubber membrane keypads or tactile steel plate switches.

Claims (9)

Claims

1. A switch comprising an activation surface which in use a user applies pressure to operate the switch, a spring for providing a resisting force for resisting the user applied pressure and user-operable adjuster for adjusting resisting force provided by the spring such that the user applied pressure required to operate the switch is variable.

2. A switch as claimed in claim 1 wherein the actuation surface comprises a spring arm.

3. A switch as claimed in claim 2 wherein the adjuster is arranged to vary the operable length of the spring arm.

4. A switch as claimed in claim 3 wherein the adjuster comprises a movable fulcrum.

5. A switch as claimed in claim 1 wherein the spring is a coil spring and the adjuster is arranged to vary a spring loading of the coil.

6. A switch as claimed in claim 5 wherein the adjuster is operable by rotation of a cam surface.

7. A switch as claimed in any preceding claim wherein the adjuster is provided with detents to allow discrete adjustment.

8. A switch as claimed in claim 7 when dependant on claim 6 the cam surface is provided with detents for engaging at least one end of the coil spring.

9. A switch substantially as hereinbefore described with reference to Figures 1 or 2 or 3 or 4 of the drawings.