GB2195417A - Twistgrip control - Google Patents

Abstract

The twistgrip control includes a potentiometer of which the electrical resistance is adjusted by turning the grip to control for example an electric motor. The control is provided on a shaft (10) of an invalid vehicle, lawnmower or golf trolley and comprises an outer rotatable component (16) journalled on an inner component (14) fast with the shaft. The potentiometer is fixed to the shaft and the potentiometer spindle (30) is adjustably connected to the outer component (16). <IMAGE>

Description

SPECIFICATION Twistgrip control It is known to make a twistgrip control for mechanical connection to the carburettor of an i.c. engine with an annular first component provided with means for fixing it angularly and axially upon e.g. the handlebar of the vehicle which is provided with the engine, and a second component or grip journalled thereon (that is to say journalled on the first component).

The grip is movable angularly, usually but not essentially between limit stops.

The object of the present invention is to provide a twistgrip control for electrical control purposes.

In accordance with the invention a twistgrip control comprises a first component which is generally annular and provided with means for fixing it angularly and axially upon a bar or tube extending through the component, a second component journalled thereon, a potentiometer adapted to be fast with the first component and with the spindle of the potentiometer adjustably fast with the second component.

Hence, angular movement of the second component (grip) varies the potentiometer setting, i.e. the electrical resistance, and this can be used in electric circuits so as to control the speed of an electric motor. This is particularly useful for an invalid vehicle, an electrically powered lawnmover, golf cart or the like which can have its speed controlled by use of such a twistgrip.

According to an important feature of the invention, the twistgrip is angularly movable through a first arc and the potentiometer is wound so that the desired electrical control is achieved through a smaller arc of movement.

Typically, the twistgrip may be movable through 100 degrees of arc and the potentiometer movement for full control may require 45 degrees of arc. When rechargable batteries are used to power the vehicle provided with the electric motor and the twistgrip control, the voltage available from those batteries is expected to vary considerably according to their state of charge. A different 45 degrees of grip movement is- used according to the state of charge.

According to a further feature of the invention, the twistgrip is provided with a detent to set the off position, which is duplicated at the opposite extreme of angular movement, enabling the same mechanical parts to be employed whether the twistgrip is to be moved clockwise or anticlockwise from the off position.

The potentiometer may be varied in a housing which is made fast with said bar or tube, e.g. is a complementary shape to a squaresection tube used as a vehicle handlebar, and the housing may also provide a further journal bearing for the second component.

One presently preferred embodiment of the invention will now be more particularly described by way of example and with reference to the accompanying drawing wherein the sole figure is a sectional elevation of the twistgrip installed on a handlebar end.

Referring to the drawing, the tube 10 is of square cross section and is the end portion of the steering component of a golf cart. The cart is driven by an electric motor associated with one or more of the wheels, and the electric motor circuit includes a potentiometer provided in the twistgrip illustrated.

The twistgrip comprises a first component 12 which maybe of circular external cross section but with a square bore to be a sliding fit on the tube 10. The component includes an axial extension 14 which is of circular cross section externally to journal the second component of the twistgrip.

The second component or grip is in the form of a tube 75 journalled on the portion 14, having an end face 18 abutting against the radially extending face of the first component. The tube is closed by an end wall 18 spaced a suitable distance from the free end of the tube 10.

Part 14 has diametrically aligned bores, as has the tube 10. part 18 has a circumferentially extending slot provided at a single radial position which can be aligned with those bores. Transverse pin 20 is threaded through the slot and through the aligned bores and at one and the same time serves to hold the parts together axially and fix the first component 12 angularly, whilst permitting the second components to move between limit stops provided by the extreme ends of the circumferentially extending slot.

The pin is retained in place and hidden from sight by a ring 22 which is snapped into place through an axial movement over the length of the component 16, and has a cross sectional shape cooperating with a shallow groove on the periphery of the parts 16 for this purpose.

Moreover, the ring 22 is also shaped complementary to the parts so that it can be located only in a single angular position. It is provided with an indication of twistgrip function, for example with arrows pointing to "off" and "on" directions of movement of the components 16.

An additional location at the two extreme positions of movement is provided by a detent in the form of a spring 24 loaded ball 26 carried in a pocket in the component 12 and with the ball capable of seating in a recess in the adjacent face of the part 16 when in either extreme end position. When the twistgrip is turned from that off position the ball rides on the plain face.

This twistgrip is designed to be used for either clockwise or anticlockwise movement from the off position. One or other of the detents holds the grip in such off position.

The function indicia mentioned above will also be "handed" according to the intended direction of movement.

Potentiometer housing 28 includes a square portion so as to be received non-rotatably in the end of the tube 10 and a circular flange which serves as an additional journal surface for the portion 15. The potentiometer itself is square so as to be non-rotatable in the housing, and is fixed by lock-nut 40.

End wall 18 is bored axially and the potentiometer spindle 30 extends into that bore. A radially extending grub screw 32 can be tightened to make the component 18 fast with the spindle 30 when the two are in a desired position of angular adjustment relative to one another. A closure plug 34 may be used behind the grub screw.

The electrical connections to the potentiometer are conveniently taken through the tube 10 for simplicity and also to make the complete installation neat and unobtrusive.

The extent of angular movement of the grip may be of the order of 100 degree of arc.

The winding of the potentiometer may be such that a movement of about 45 degree of the spindle takes the motor from off to full speed or vice versa. With (rechargeable) batteries, the voltage available is expected to vary considerably according to whether the batteries are fully charged or not. A different 45 degree of grip movement may be used according to requirements, by winding the potentiometer appropriately to give suitable resistance according to such varying states of battery charge, and of course providing the grip with the facility for movement over the wider range.

The potentiometer housing also encloses an on/off switch actuated by a first part of movement from the one extreme angular position.

Claims (8)

1. A twistgrip control comprising a first component which is generally annular and provided with means for fixing it angularly and axially upon a bar or tube extending through the component, a second component jour nalled thereon, a potentiometer adapted to be fast with the first component and with its spindle adjustably fast with the second component.

2. A twistgrip control as claimed in Claim 1 wherein said two components are held together axially and are also adapted to be fixed axially upon the bar or tube extending through the components, by one and the same pin passed generally transversely through aligned apertures.

3. A twistgrip control as claimed in Claim 2 wherein the second component has a circumferentially extending slot receiving an end of the pin, so that the ends of the slot act as limits to angular movement.

4. A twistgrip as claimed in any preceding claim wherein the second component is adapted to be moveable angularly through a first arc and the potentiometer is wound so that the desired control is achieved by movement of its spindle through a narrower arc.

5. A twistgrip as claimed in any preceding claim wherein the potentiometer housing includes an on/off switch.

6. A twistgrip as claimed in any preceding claim provided with a detent to releasably hold the grip in either of two extreme positions of angular movement.

7. A twistgrip as claimed in any preceding claim wherein the potentiometer spindle extends axially through a closure at the end of said second component and is made fast therein by radially extending grub screw or the like.

8. A twistgrip control substantially as described with reference to the accompanying drawings.