GB2098402A - Variable-resistance controller - Google Patents

Abstract

A variable-resistance controller for a battery-operated device, of the kind in which a battery (2) is contained within a tubular body (3) of the device, is housed in an end cap for attachment to the body and a cover (16). Two contact members (5, 6) are located within the cap for connection, respectively, to the battery and to the device. A tappable resistor (11) e.g. comprising a winding (13) on a former (12) is mounted on the back of the end cap and is connected to one of the contact members (6). The cover (16) is attached to the end cap by screws (33). A thumbwheel (20) is rotatably mounted on the inside of the cover with part of the periphery of the thumbwheel accessible from outside the cover. An electrically-conductive arm (15) is rotatable together with the thumbwheel and makes tapping contact with the resistor. The arm also makes electrical contact with a part (8) of the contact member (5) which extends through the end cap. As the thumbwheel is rotated, a varying length of the resistance is connected between the contact members. At one end of its rotation the arm (15) may move out of contact with the resistor (11), thereby providing a switching function. <IMAGE>

Description

SPECIFICATION Variable-resistance controller This invention relates to a variable-resistance controller for a battery-operated device of the kind in which a battery is contained within a tubular body of the device, and to a method of constructing such controller. The device may, for example, be a torch, the controller then being effective, in use, to control the light intensity.

Alternatively, the device may include an electric motor, the speed of which is controlled by the controller.

It is an object of the present invention to provide a controller and a method of constructing a controller which are both simple and inexpensive.

According to one aspect of the invention, a variable-resistance controller for a batteryoperated device of the kind in which a battery is contained within a tubular body of the device comprises an end cap for attachment to the body; two contact members located within the cap for connection, respectively, to the battery and to the device; a cover attached to the end cap and forming a chamber therewith; tappable resistance means mounted on the end cap and within the chamber and connected to one of the contact members; a thumbwheel rotatably mounted on the inside of the cover with part of the periphery of the thumbwheel accessible from outside the chamber; and an electrically-conductive arm rotatable with the thumbwheel round a sector of a circle and making tapping contact with the resistance means over at least part of the sector, the arm making electrical contact with the other contact member, whereby as the thumbwheel is rotated a varying length of the resistance is connected between the contact members.

According to another aspect of the invention, a method of constructing a variable-resistance controller for a battery-operated device of the kind in which a battery is contained within a tubular body of the device comprises forming an end cap for fitting on to the body, the end cap having an end wall with first and second surfaces inside and outside the cap, respectively; mounting two contact members on said first surface for connection to the battery and the device, respectively, one of the contact members also providing an electrical contact at said second surface; attaching a tappable resistor to said second surface with one end of the resistor connected to the other contact member; locating a thumbwheel rotatably on the inside of a cover with.part of the periphery of the thumbwheel accessible from outside the cover; locating an electrically-conductive arm in engagement with the thumbwheel for rotation with the thumbwheel, the arm having a boss which is aligned with the axis of rotation of the thumbwheel and having a free end remote from the boss; and fastening the cover over said second surface with the boss of the arm in engagement with said electrical contact, and with the free end of the arm in sliding engagement with the resistor so that rotation of the thumbwheel causes variation of the amount of resistance connected between the first and second contact members.

An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawing, in which: Fig. 1 is an exploded sectional view of a controller in accordance with the invention, Fig. 2 is a front view of a cover forming part of the controller, Figs. 3(a) and 3(b) are rear and front views, respectively, of a thumbwheel of the controller, Fig. 4 is a front view of an arm of the controller, Figs. 5(a) and 5(b) are rear and front views, respectively, of an end cap assembly of the controller, and Fig. 6 shows the relative positions of the cover, the thumbwheel and the arm in the assembled controller.

Referring to the drawing, a variable-resistance controller for a torch, a vibrator, a fan or other battery-operated device 1 of the kind in which a battery 2 is contained within a tubular body 3 of the device comprises an electrically-insulating end cap 4 which is a push fit over the end of the body.

A resilient contact member 5 is provided within the cap 4 for making electrical contact with the end of the battery when the cap is fitted to the body 3. A substantially flat, generally S shaped contact member 6 makes electrical contact with the bottom edge of the body 3 if the body is electrically conductive, or with conductive strips attached thereto if the body is made of an insulating material. The contact member 5 extends through a slot 7 in the face of the end cap 4, and a portion 8 of the member 5 lies flat against the rear of the face and is fixed to the face by means of an eyelet or rivet 9. Tabs 10 on the contact member 6 extend through slots in the cap 4 and are bent over to attach the member to the cap.

A resistor 11 comprises a cylindrical insulating former 1 2 on which is located a helical resistive element 13. A tubular metallic ferrule 14 is crimped over the end of the element 13 and the former 12 to make good electrical contact with the element. The resistor 11 is attached by adhesive to the rear of the end cap 4, in the position shown in Fig. 5(a). The ferrule 14 makes electrical contact with one of the tabs 10 of the contact member 6.

The element 1 3 may comprise a non-insulated resistance wire, provided that adjacent turns of the helix are maintained in spaced-apart relationship. Alternatively, the resistance wire may have an insulating coating to separate the adjacent turns, in which case the insulation must be removed from the upper surface of the element 11, as viewed in Fig. 5(a), to provide a track with which an electrically-conductive arm 1 5 can make wiping contact, as will be explained below. In another alternative arrangement, the resistor 11 may comprise a carbon track which is deposited on a flat elongate former.

A cover 1 6 comprises a disc 17 with an annular wall 1 8 which extends round approximately threequarters of the periphery of the disc, leaving an opening 1 9 between the ends of the wall. A thumbwheel 20 also comprises a disc 21 with an annular wail 22 extending round most of its periphery, but !eaving a gap 23 between the ends of the wall. The wall 22 is serrated around approximately three-quarters of its outer surface for ease of operation by the user. A boss 24 on the rear of the thumbwheel fits into an aperture 25 on the inner surface of the cover 1 6 so that the thumbwheel is pivoted with part of its serrated periphery projecting through the opening 1 9.

Around the boss 24 are radial notches 26 which cooperate with a projection 27 on the inner surface of the cover 16, to act as an indexing device.

The arm 1 5 comprises a boss 28 with a central axial projection 29 and an elongate wiper 30. The arm is located in the thumbwheel (Fig. 6) with the axis of the boss aligned with the rotation axis of the thumbwheel, and with the wiper 30 seated in the gap 23.

The controller is assembled by mating the cove assembly shown in Fig. 6 with the rear of the cap assembly (Fig. 5(a)) so that the wiper 30 is in contact with the resistor 11 and the boss and projection 29 of the arm are in contact with the eyelet or rivet 9. Accurate alignment is ensured by the interengagement of dowels 31 on the cover with apertures 32 in the cap. Self-tapping screws 33 are positioned in holes 34 in the cap 4 and screwed into bosses 35 formed on the inside of the cover 16.

Rotation of the thumbwheel will cause the wiper 30 to make sliding contact with the surface of the resistor 11 so that a variable portion of the resistor 11 will be connected between the ferrule 14 and the wiper 30, and hence between the contact members 5 and 6. This results in an adjustable portion of the voltage of the battery 2 being applied to the device. The amount of rotation which can be achieved is limited by the arm 15 coming up against the ferrule 14 in one direction of rotation and with the dowel 31 in the other direction of rotation In the latter position the wiper 30 will have moved out of contact with the resistor 11 , and so the supply of current to the device will be discontinued. The controller therefore also acts as a switch.

If the switching operation is not required, the rotation of the arm 1 5 can be limited so that the wiper 30 does not lose contact with the resistor 11.

It will be appreciated that the controller is very simple to assemble and inexpensive to produce.

Claims (9)

1. A variabie-resistance controller for a batteryoperated device of the kind in which a battery is contained within a tubular body of the device, the controller comprising an end cap for attachment to the body; two contact members located within the cap for connection, respectively, to the battery and to the device; a cover attached to the end cap and forming a chamber therewith; tappable resistance means mounted on the end cap and within the chamber and connected to one of the contact members; a thumbwheel rotatably mounted on the inside of the cover with part of the periphery of the thumbwheel accessible from outside the chamber; and an electricallyconductive arm rotatable with the thumbwheel round a sector of a circle and making tapping contact with the resistance means over at least part of the sector, the arm making electrical contact with the other contact member, whereby as the thumbwheel is rotated a varying length of the resistance is connected between the contact members.

2. A controller as claimed in Claim 1, wherein the thumbwheel comprises a disc with an annular peripheral wall upstanding therefrom; and wherein the arm extends through a gap in the wall and is held by the wall for rotation with the thumbwheel.

3. A controller as claimed in Claim 2, wherein the disc has, on its face adjacent the cover, a plurality of notches which dooperate with a projection on the cover for indexing the rotation of the thumbwheel.

4. A controller as claimed in Claim 2 or Claim 3, wherein the thumbwheei has serrations on its peripheral wall.

5. A controller as claimed in any preceding claim, wherein the thumbwheel is rotatably mounted on the cover by an axial boss projecting from the thumbwheel, which boss is located in an aperture in the cover.

6. A controller as claimed in Claim 1 and substantially as hereinbefore described with reference to the accompanying drawing.

7. An electrically-operated device including a controller as claimed in any preceding claim.

8. A method of constructing a variableresistance controller for a battery-operated device of the kind in which a battery is contained within a tubular body of the device, the method comprising forming an end cap for fitting on to the body, the end cap having an end wall with first and second surfaces inside and outside the cap, respectively; mounting two contact members on said first surface for connection to the battery and the device, respectively, one of the contact members also providing an electrical contact at said second surface; attaching a tappable resistor to said second surface with one end of the resistor connected to the other contact member; locating a thumbwheel rotatably on the inside of a cover with part of the periphery of the thumbwheel accessible from outside the cover; locating an electrically-conductive arm in engagement with the thumbwheel for rotation with the thumbwheel the arm having a boss which is aligned with the axis of rotation of the thumbwheel and having a free end remote from the boss; and fastening the cover over said second surface with the boss of the arm in engagement with said electrical contact, and with the free end of the arm in sliding engagement with the resistor so that rotation of the thumbwheel causes variation of the amount of resistance connected between the first and second contact members.

9. A method as claimed in Claim 8 and substantially as hereinbefore described with reference to the accompanying drawing.