THIS INVENTION relates to improvements to joystick assemblies and in particular to joystick assemblies for use with computers, video games or other similar apparatus. Background Art

Joysticks for use with computers, video games or the like normally are in two forms to suit the type of computer with which the joystick is associated. In one form the joystick includes a plurality of switches which may be depressed upon pivotal movement of a control arm in a swivelling type manner. Such joysticks provide through the switches an on/off control mechanism for controlling the computer or video game. A second form of joystick employs a similar type of control arm. however, in this instance the joystick includes a variable resistor normally in the form of a straight line potentiometer which is operated through a lever mechanism to provide a variable output resistance upon pivotal movement of the control shaft. Alternatively other forms of variable resistors or potentiometers are mechanically controlled by movement of the control shaft to provide a varying output resistance. A disadvantage of the latter types of joystick is that considerable wear occurs because of the mechanical contact between the sliding terminal of the potentiometer and the potentiometer resistance member so that breakages often occur resulting in machine down time. This is undesirable both in household situations and in situations where the joystick is used in a video machine for the purposes of earning income.

U.S. Patent No. 4748323 in the name of Holiday discloses a joystick device of the first type wherein a light emitter and light detector are employed and a blocking member is moved by the joystick control arm to a position to either block the light between the emitter and detector or allow the passage of light. This device is only suited to providing an on/off type output and not a variable output and accordingly its application is limited.

Summary of the Invention

The present invention aims to overcome or alleviate the above disadvantages by providing a joystick assembly which may provide a variable output upon actuation but which substantially eliminates or reduces the wear associated with conventional joystick assemblies and which therefore enables an increased working life for such joysticks assemblies. Other objects and advantages of the invention will become apparent from the following description. With the above and other objects in view the present invention provides a joystick assembly including a moveable control arm, light emitting means, light sensing means for receiving light from said light emitting means and providing an output dependant upon the amount of light received from said light emitting means, and shutter means disposed adjacent said light emitting means and said light sensing means, said shutter means being coupled to said control arm and being moveable across the path of light between said l ght emitting means and said light sensing means upon movement of said control arm whereby to vary the amount of light received by said sensing means and thereby the output thereof.

Preferably said shutter means comprises a shutter member having a tapered shutter portion. Suitably said tapered shutter portion comprises a tapered slot. Preferably said shutter member includes a planar tongue-like member and said tapered slot is formed in said tongue like member.

Suitably said light emitting means comprises a light emitting diode and said light sensing means comprises a light dependent resistor. The joystick assembly also most preferably includes a substantially closed housing in which said shutter means are located and said control arm is supported on said housing for pivotal movement, preferably universal pivotal movement. The joystick assembly also- most preferably includes further shutter means within said housing coupled to said control arm so as to be movable thereby, and further light emitting means and light sensing means associated with said further shutter means, said further shutter means varying the amount of light received

by said further light sensing means when moved by said control arm.

Suitably said first and further shutter means are supported for movement along orthogonal axes. Preferably guide means are provided for guiding movement of said shutter means along said orthogonal axes. Suitably said guide means for said shutter means comprise recesses for slidabely receiving said shutter means. Preferably also each said shutter means includes a slot extending normal to the its direction of movement and said control arm includes a member disposed within said slots and coacting therewith to cause movement of said shutter means upon movement of said control arm. Movement of the shutter means depend upon both the direction of movement and degree of movement of the control arm. The joystick assembly also preferably includes support bracket means for supporting the or each said light emitting means relative to said light sensing means and means are provided for adjustably mounting said support bracket means whereby to enable variation of the position of said light emitting means and associated light sensing means relative to their associated shutter means. Brief Description of the Drawings

In order that the invention may be more readily understood and put into practical effect reference will now be made to the accompanying drawings which illustrate a preferred embodiment of the invention and wherein:-

Fig. 1 is a side elevation view of the joystick assembly according to the present invention;

Fig. 2 is a plan view of the joystick assembly of Fig. 1;

Fig. 3 is an underside view illustrating the control components of the joystick assembly;

Fig. 4 is a sectional side elevational view along the line A-A of Fig. 3; Fig. 5 is a plan view illustrating the shutters of the control apparatus in a neutral mode;

Fig. 6 to Fig. 8 illustrate the manner in which the shutters are moved;

Fig. 9 illustrates schematically the principles of operation of the present invention; and

Fig. 10 is an electrical circuit diagram of the joystick assembly. Detailed Description of the Invention

Referring to the drawings and firstly to Figs. 1 and

2 there is illustrated a joystick assembly 10 according to the present invention including a casing or housing 11 which is formed in two interconnected parts comprising an upper part 12 and a base or lower part 13 which may be interconnected in any suitable manner such as by adhesives or screw connectors as is common in the trade to form a hollow enclosure which is substantially sealed and shielded from external light conditions. The upper part 12 of the casing 11 supports a control arm 14 which is mounted to the upper part 12 of the casing at 15 via a ball and socket type connection (shown cut away in Fig. 4) for universal pivotal or tilting movement in vertical planes and which includes an enlarged end 16 for supporting a button 17 which may be depressed to actuate a firing switch (not shown) in conventional manner. Also supported on the upper casing part 12 are respective zero adjustment slides 18 and 19 which are adapted to adjust the centre position of the cursor on the computer screen as described further below. The upper housing part 12 may also support further buttons 20 for actuator of further firing switches again in a conventional manner.

The control arm 14 as more clearly illustrated in Figs.

3 and 4 extending into the housing part 12 and is provided with a contact bush 21 at its free end whilst a return spring 22 is located about the arm 14 and between the bush 21 and the adjacent normally upper wall 23 of the housing part 12 so as to return the arm 14 to a central upstanding neutral position after it has been tilted or pivoted therefrom.

Mounted to the underside of the housing part 12 is a controlling mechanism 24 which is associated with the control arm 14 to provide an output say to a computer dependent upon the direction of movement of the control arm 14. The control mechanism 24 includes a base part 25 and a top part 26 which is engaged with the base part 25 and the assembly of top part 26 and

base part 25 are secured to support posts 27 extending outwardl from the top wall 23 of the housing part 12 by means of screw 28 which pass through aligned apertures 29 in the parts 26 an 25 and into the posts 27. The base part 25 is provided with rectangular guide recess 30 in its upper surface (with referenc to Fig. 4) which opens at 31 at one side of the base part 25. The top part 26 is provided with a similar recess 32 which open at 33 to one side of the part 26 but which extends at righ angles to the recess 30 as is apparent in Fig. 3. Each recess 30 and 32 is adapted to slidably receive a shutter 34 and 35 as shown in Figs. 3 to 5. Each shutter 3 and 35 includes a base portion 36 and 37 respectively which is of a size to be neatly received in the respective recesses 30 and 32 so as to be slidable therein. The shutters 34 and 35 also include shutter members 38 and 39 respectively which project outwardly through the openings 31 and 33 of the respective recesses 30 and 32. The shutter member 38 is provided with a triangular aperture 40 which reduces in width outwardly of the member 38 to terminate short of the end thereof, whilst the other shutter member 39 is provided with a triangular recess 41 which is open to the end of the shutter member 39 and reduces in width inwardly from the end of the shutter member 39. When assembled, the shutters 34 and 35 rest on each other for sliding movement relative to each other. As is apparent in Fig. 5 the longitudinal axes of the respective triangular apertures 40 and

41 extend generally in the direction of the axes of movement of the respective shutters 34 and 35.

The shutter base parts 36 and 37 are also provided with elongated slots 42 and 43 respectively of a width to neatly receive the bush 21 on the end of the control arm 14, the slots

42 and 43 being rounded at their opposite ends as i lustrated. In each case the slots 42 and 43 extend normal to the direction of movement of the respective shutters 34 and 35. The function of these slots will be described further below. Associated with each shutter 34 and 35 is a light source in the form of a light emitting diode (LED) 44 and a light dependent resistor (LDR) 45 which are mounted on opposite sides of each shutter member 38 and 39 as shown in Fig. 4. For this

purpose respective support arm assemblies 46 are provided, each arm assembly 46 including a first arm portion 47 terminating in a bush 48 which is supported rotatably on an upstanding post 49 on the base part 25 and a second arm portion 50 spaced from the arm portion 47 and extending substantially parallel thereto and interconnected for movement therewith through a pillar 51. The arm portion 50 carries the LDR 45 which is mounted on a printed circuit board 52 whilst the arm portion 46 carries the LED 44 also mounted on a printed circuit board 53 so that the LED 44 and LDR 45 are located on opposite sides of the shutter member 39. The end of the arm portion 50 is provided with a hook 54 for location about a tang 55 secured to the zero adjustment slide 19, the tang 55 projecting through a slot 56 (see Fig. 3) in the wall 23. Movement of the slide 19 in opposite directions will cause through engagement of the tang 55 with the hook 54 pivotal movement of the arm assembly 46 about the post 49 and adjustment of the positions of the LED 44 and LDR 45 relevant to the shutter member 39. A similar arrangement is provided for the other shutter member 38 with adjustment, in this case, being made through the slide 18.

Referring now to Figs. 5 to 8, assuming that the arm 14 is pivoted in one direction parallel to the recess 30 the arm 14 will through engagement of the bush 21 with the side of the slot 42 cause outward movement of the shutter 34 and thus shutter member 38, this movement being accommodated by the slot 43 in the shutter 35, the latter not being moved as shown in Fig. 6. The extent of outward movement of the shutter 34 depends upon the degree of pivoting of the control arm 14. Similarly movement of the arm 14 from its upright neutral position in a direction parallel to the recess 32 will cause via the bush outward movement of the shutter member 35 with movement of the arm 14 being accommodated by the slot 42 as shown in Fig. 7 so that the shutter 35 does not move. Pivotal movement of the arm 14 in other directions will cause movement of both shutter members 34 and 35 with the extent of movement of the shutter members 34 and 35 being dependant both upon the direction of movement of the control arm 14 and the angle through which the control arm 14 is pivoted. This will be apparent from Fig. 8 where the bush 21 has

been moved by the arm 14 to an upper right hand corner positio thus coacting with the slots 42 and 43 of both shutter member 34 and 35 to withdraw the shutters 42 and 43 into the base an top parts 25 and 26. Movement of the control arm 14 in othe directions is transformed into orthogonal components of movemen resulting in equivalent movements of the shutters 34 and 35.

Referring now to Fig. 9 which illustrates the principl of the invention, the light emitting diode 44 and light dependen resistor 45 are located on opposite sides of a shutter member say 39. The amount of light which the light dependent resisto 45 receives from the light emitting diode 44 through the slot 4 depends upon the extent that the shutter member 39 intersects th path of light. Movement of the shutter member 39 in th direction X will enable increased light to be received by the LD 45 because a larger region of the aperture 41 is aligned with th light source 44. Movement of the shutter member 39 in th direction Y will reduce the effective size of the aperture 1 between the LED 44 and LDR 45 to therefore reduce the amount o light received by the LDR 45 as a smaller region of the apertur 41 will be available through which light can be transmitted. Thus the LDR 45 will have a variable resistance in accordanc with the extent of light received so as to provide a variabl output proportional to the extent that the shutter member 39 blocks the light path. This principle applied to the apparatu of the invention will result in an output from both LDRs 45 which depends upon the extent that the light from their associated LEDs is blocked by their associated shutter 34 and 35.

Fig 10 illustrates a preferred electric circuit diagram of the joystick assembly 10 of the invention. The LEDs 44 are placed in series with resistors 56, the latter limiting current flow through the LEDs 44 and thereby the intensity of light emitted by the LEDs 44. Potentiometers 57 are placed in parallel across the LDRs 45 to set the maximum output resistance at the vertical and horizontal output terminals 58 and 59. The switches designated A and B are actuated by the buttons 20 (see Figs. 1 and 2) and comprise the "firing" switches of the joystick assembly 10. For automatic "firing" a type 555 timer 60 is arranged in circuit to provide a pulsed output which

may be switched into the circuit by a switch 61.

The circuit also includes a switch 62 to enable the mode of the joystick assembly to be switched between IBM (Registered Trade Mark) mode and APPLE (Registered Trade Mark) mode. In the latter mode resistors 63 in series with diodes 64 connect the "firing" switches A and B to ground.

The shutters 34 and 35 may be of many different forms including a tapering portion which moves across the light path or simply with a transverse edge which moves across this path. The light sensitive means may comprise any device which responds to light and provides an output signal in accordance with the extent to which the device is exposed to light. Thus the device may comprise a phototransistor or any other photosensitive device. Similarly the light source may comprise an incandescent light source or any other light source.

The shutters 34 and 35 may be formed of any opaque material which will perform a light blocking function whilst any suitable means may be provided for supporting the shutters 34 and 35 for movement across the path of the light. Suitably, the shutters 34 and 35 are formed of plastics material as are the other main components of the joystick assembly 10.

The shutters 34 and 35 are preferably designed so as to provide linear output from the LDRs 45 proportional to the shutter's movement across the light path. This is most suitably achieved by forming the shutter apertures 40 and 41 into the form shown, that is in the form of triangular apertures. Alternatively the LDR's 45 may be placed in a circuit so as to provide a linear output which is again proportional to the linear movement of the shutter 16 across the light path. In use, the joystick assembly 10 is connected to the joystick socket of a suitable computer or other apparatus having a VDU such as a games machine and when set up to suit a particular software program, the control arm 14 is pivoted in any desired direction and to any desired degree. The corresponding movement of the shutters 34 and 35 will cause a variable resistance output at the terminals 58 and 59 in accordance with the direction and degree of movement of the control arm 14 and therefore movement of the screen cursor or other image on the

computer VDU being controlled by the joystick assembly 10. For centering of the image, one or both adjustment slides 18 and 19 may be manipulated to vary the positions of the LEDs and LDRs relative to the shutter members 38 and 39. This will cause the resistance of the LDRs to be change as a result of change of relative positioning of the shutter members 38 and 39 across the light path. The resistance change of the LDRs will be translated into a proportional change of image positioning on the VDU.

All modifications and variations to the invention other than those described above as would be apparent to persons skilled in the art are deemed to fall within the broad scope and ambit of the invention as defined in the appended claims.