GB2107030A

GB2107030A - Control mechanism

Info

Publication number: GB2107030A
Application number: GB08227202A
Authority: GB
Inventors: Dwayne R Elmberg
Original assignee: Sundstrand Corp
Current assignee: Sundstrand Corp
Priority date: 1981-10-02
Filing date: 1982-09-23
Publication date: 1983-04-20
Also published as: FR2514166A1; SE8205269L; JPS5864521A; IT8249192A0; SE8205269D0; DE3236480A1; AU8759082A

Abstract

A joystick handle 11 extends through an aperture 19 in a mounting plate 12. An edge of the aperture 19 has a cam surface 20 which engages a cam follower 22 biassed towards the cam surface 20 by a coil spring 24 secured by a retainer 25. Pivotal movement is provided by a gimbal 13. The corporation of the cam surfaces provides good return-to-centre characteristics. <IMAGE>

Description

SPECIFICATION Control mechanism The invention relates to control mechanism comprising a handle capable of pivotal movement about axes transverse to the handle, i.e. a joystick, having good return-to-centre characteristics.

Joysticks are used as switch or valve actuators in a variety of applications in which a number of independent functions are controlled from a single handle. Exampies include controlling the angle and height of blades, scrapers, and/or cutters, on earth and/or snow moving machinery, controlling airfoil surfaces, controlling cutter positions in multi-axis machine tools, and controlling electron beam position in a variety of instruments.

Mechanism according to the invention comprises a mounting plate having an aperture through which the handle extends, an edge of the aperture having a cam surface, a cam follower slidable along the shaft, and means biassing the cam follower towards the cam surface.

This arrangement is simple to manufacture from a small number of easily assembled parts, and can accommodate a variety of switches, proportional electronic output devices, and/or valves. Accommodation of such devices is facilitated by maximizing the space n the controller which is uncommitted to other features, such as mechanism for mounting the handle shaft for pivotal movement and for biasing the handle to a neutral position. The overall size, and particularly the depth of such mechanism, or the distance it extends behind the structure on which it is mounted, can be small. The force-displacement ratio can be substantially the same in any direction of handle pivotting.

The pivotal movement may be provided by means of a gimbal or ball and socket joint, for example. The cam surface is preferably of circular section, and the cam follower preferably has a conical surface engaging therewith. The aperture is preferably circular. The biassing means may be a coil spring compressed between the cam follower and a retainer.

DRAWINGS Figure 1 is a perspective view, partially cut away, of control mechanism in accordance with the invention; Figure 2 is a section of the mechanism of Figure 1 with the handle in a centred position; Figure 3 is a section of the mechanism of Figure 1 with the handle pivoted to a position of extreme excursion from the centred position; Figure 4 is a plan of a mounting plate in the mechanism of Figure 1; and Figure 5 is an enlarged section of a portion of the plate in Figure 4 along a line 5-5.

With particular reference to Figure 1, mechanism 10 comprises a control handle 11 pivotally supported on a mounting plate 1 2 by means of a gimbal 13. The handle 11 has a longitudinal axis 14, and is pivotable about orthogonal and transverse axes 1 5 and 1 6 which have a pivot point 1 7 thereon (Figures 2 and 3).

The plate 12 has an upper surface 1 8 and an aperture 1 9 therethrough surrounding the shaft 11. As shown in Figure 4, the aperture 19 is circular, and symmetrical about the axis 1 4 when the shaft 11 is centred. A cam surface 20 (Figure 5) is formed around an edge of the aperture 1 9 at its intersection with the surface 1 8. The cam surface 20 is shaped so that its radial cross section with respect to axis 14 is a circular arc.

A cam follower 22 in the form of a sleeve having a conical surface 23 thereon is mounted on the shaft 11 for sliding movement along the axis 14. The surface 23 is a surface of revolution about the axis 14. The cam surface 20, which also is a surface of revolution, is shaped and positioned to interact with the conical surface 23, which is on the side of plate 12 opposite the pivot point 1 7.

A coil spring 24 surrounding the shaft 11 is compressed between the cam follower 22 and a retainer 25 fixed to the shaft 11. The spring 24 comprises biassing means for urging the cam follower 22 towards the pivot point 17.

Accordingly, the spring.24 tends to cause the cam follower 22 to seat in the aperture 1 9 to establish a centred position of the shaft 11. The cam follower 22 is permitted by the cam surface 20 to make its closest approach to or reach a minimum distance from the pivot point 1 7 when the shaft 11 is in the centred position, As shown in Figure 3, as the shaft 11is pivoted away from the centred position in any direction transverse to the axis t4, the cam surface 20 causes the cam follower 22 to move away from the pivot point 1 7 against the spring 24. Conversely, the spring 24 in connunction with the cam follower 22 and the' cam surface 20 tend to return the shaft 11 to the centred position.

The gimbal 13 comprises a ring 30 which'is .

pivotally connected to the shaft 11 by pivot pins 31 aligned with the axis 16. The ring 30 is also pivotally mounted on the plate 12 by brackets 32 fixed to the plate 12, and pivot pins 33 aligned with the axis 1 5 pivoting in the brackets 32.

Accordingly, the shaft 11 pivots independently about the axes 1 5 and 1 6. The upper end of shaft 11 would be fitted with a handle, and the lower end adapted to actuate the switches and/or valves. A suitable mechanism is generally illustrated in Figures 1 to 3.

Supporting structure 34 is attached to the plate 12 by means of screws 35 extending through counter sunk holes 36 (Figure 4). The structure 34 has an aperture 37 through which the lower end of the shaft 11 extends. The structure 34 also has a lower planar surface 38. A retainer 39 having a planar upper surface is mounted on but spaced from the structure 34 by means of posts 40, leaving a cavity with parallel surfaces between the structure 34 and the retainer 39. A disc 41 is mounted in the cavity. The disc 41 comprises a flexible centre web 42 having an aperture snugly receiving the end of the shaft 11, and a thickened rim 43 having parallel sides and a thickness slightly less than the distance between the structure 34 and the retainer 39. Pivoting of the shaft 11 about the pivot point 1 7 is converted into planar motion of the rim 43 by its connection to the shaft 11 through the web 42. Switches 44 are mounted on the supporting structure 34 around the disc 41 so that their operators, which may comprise levers and/or plungers, may be displaced by the rim 43. Accordingly, a desired one or more of the switches 44 may be actuated by pivoting the shaft 11 in an appropriate direction.

Claims

1. Control mechanism comprising a handle capable of pivotal movement about axes transverse to the handle, a mounting plate having an aperture through which the handle extends, an edge of the aperture having a cam surface, a cam follower slidable along the shaft, and means biassing the cam follower towards the cam surface.

2. Control mechanism according to Claim 1 in which the cam surface is of circular section, and the cam follower has a conical surface engaging the cam surface.

3. Control mechanism according to claim 1 or claim 2 in which the aperture is circular.

4. Control mechanism according to any preceding claim in which the biassing means comprises a coil spring surrounding the handle and compressed between the cam follower and a retainer.

5. Control mechanism as herein described with reference to the drawings.