US 3900817 A
Description (OCR text may contain errors)
[451 Aug. 19, 1975 SPHERICAL POTENTIOMETER WITH Primary Examiner-Bruce A. Reynolds BALL CONTACT MEANS  Inventor: Vernon E. Punt, Fairport, NY.
ABSTRACT  Assignee: Xerox Corporation, Stamford.
A potentiometer having as an input a manually con-  Filed: Dec. 10, 1973 trolled, bearing supported conducting sphere which, when rotated simultaneously varies two resistances Appl. No.: 423,633
representative of an X coordinate and a Y coordinate. The potentiometer comprises a first stationary outer  US. 338/157; 338/202 partial sphere on the inner surface of which is carried  Int. Field of Search HOlc 5/04 a continuous helical strip of conductive material. A 338/157, 128,130, 131
stationary insulating ball surface is located interior of 338/143, 190. 202, 162, 163; 74/471 XY said outer sphere and carries a second strip of conductive material on its outer surface. A second sphere is supported for rotational movement intermediate the  References Cited UNITED STATES PATENTS first sphere and ball surface on a plurality of ball bear- 338/202 x ings, two of which are made of a conductive material.
338/130 X By moving the second sphere either one of the resist- H 333/202 X ances may be varied independently of each other. or
338/157 x both may be varied simultaneously.
2.704.798 3/1955 Gaylord et al.
2.866.124 12/1958 Giuffrida et a1.
2.912.662 11/1959 Faymoreau 2.993.184 7/1961 Mims et FOREIGN PATENTS OR APPLICATIONS 4 Claims, 1 Drawing Figure SPHERICAL POTENTIOMETER WITH BALL CONTACT MEANS BACKGROUND OF THE INVENTION This invention relates to a new and improved adjustable potentiometer in which two resistances may be varied simultaneously by rotating a movable sphere. In particular, it is directed to a potentiometer in which two resistances may be varied independently of each other. That is, the first resistor may be held constant while the second is varied to any magnitude within its range and conversely the second may be held constant while the first is varied to any value between its range. In addition, both resistances may be varied simultaneously to any desired value.
This invention has particular utility to circuits for moving a cursor or marker on a CRT screen. In such arrangements, the position of the marker is a function of an X-coordinate voltage and a Y-coordinate voltage. In some prior art techniques the marker may be moved only by individually changing the X-coordinate voltage and the Y-coordinate voltage in succession.
With the arrangement of the invention, movement of a single manually adjustable sphere simultaneously varies both X and Y coordinates parameters such that the marker may be moved to any position more easily and quickly.
OBJECTS AND SUMMARY OF THE INVENTION It is therefore an object of the invention to provide a potentiometer in which two resistances may be simultaneously varied by the single movement of a control sphere.
A further object is to provide a potentiometer of the above noted type which responds to an operators touch in a smoother and more uniform fashion than was heretofore known in the prior art.
In accordance with the present invention there is provided a twoaxis potentiometer having as an input a manually controlled, bearing-supported conducting sphere which, when rotated may simultaneously vary two resistances depending upon the degree and direction of movement of the sphere. The potentiometer comprises a stationary non-conductive outer partial sphere on the inner surface of which is carried a first continuous helical strip of conductive material. A stationary ball surface is located interior of said outer sphere and carries on its outer surface a second strip of conductive material. Another conductive partial sphere is supported for rotational movement intermediate the outer sphere and the ball surface on a plurality of ball bearings, two of which are made of a conductive material, the remainder being non-conductive. By moving the second sphere, either one of the resistances may be varied while holding the other constant, or both may be varied simultaneously. Means including the conductive ball bearings are provided for conducting a first current through the first strip and a second current through the second strip; thus, by varying the resistances, both the voltage thereacross and the currents therethrough are also varied, the latter voltages being used to control movement on a marker.
BRIEF DESCRIPTION OF THE DRAWINGS The drawing is an illustrative side view, partly in section, showing the elements of the potentiometer of the present invention.
DETAILED DESCRIPTION The two axis potentiometer of the invention comprises a hollow outer partial sphere 3 which may be mounted in a stationary position by means of spaced flanges 4. The top of the sphere, as seen in the drawing, is cut to define a circular opening 7. An electrical terminal 6 extends through the wall of the sphere 3 and is connected to one end of the resistive strip 5. The strip 5 defines generally a helical path starting at one end adjacent the mid point of the sphere 3 and continuing in one direction to cover substantially one half of the inner surface of the sphere. The material 5 is selected so as to provide increasing values of resistance in proportion to the length thereof through which current flows.
Inside the outer sphere 3 is supported a second partial sphere 8 made of an electrically conductive material. The top portion of the sphere 8 is accessible through the opening 7 in the sphere 3 for rotation to various positions, as will be explained in greater detail hereinafter. The sphere 8 is formed to define a downwardly directed opening 9, as seen in the drawing.
Interior of the sphere 8 and spaced therefrom is a ball surface 12 made of an insulating material and coated in a fashion similar to the inner surface of sphere 3 with a continuous strip of resistive conductor 13. The conductor defines a helical path extending from a point midway of the ball 12 to cover substantially one half of the outer surface thereof. The end of the strip 13 near the midpoint of the ball I2 is connected to a terminal 14 located at the bottom of the potentiometer assembly. The ball surface 12 is supported in a stationary position by means of a centering compression spring arrangement 17 which extends through the opening 9 in the sphere 8. The spring arrangement 17 is supported on one end by the interior surface of the outer sphere 3 and at the other end by the outer surface of the ball 12.
A plurality of ball bearings are arranged in conventional fashion in pockets or depressions in the walls of the spheres (as depicted in the drawing) to permit rotational movement of the sphere 8 with respect to the outer sphere 3 and ball surface 12. In the ball bearing arrangement shown in the drawings all bearings are carried by the movable sphere 8, but some may be mounted, as matter of design choice, on the inner surface of the outer sphere. The only constraint in this regard is that the conductive balls, to be discussed in detail below, must be mounted for movement with the sphere 8.
The ball bearing arrangement shown in the drawing includes four sets 20, 30, 40 and 50, each set located in a common, horizontal plane and including three bearings spaced from each other. Only two of the bearings in each set are shown in the drawing for the sake of clarity. Also, for the sake of ease of illustration, the balls, as shown, are displaced from the 120 positions noted above.
Ball bearing set 20 includes bearings 21 and 22 and another bearing (not shown). Bearing 2] is made of a conductive material, while the bearing 22 and the other bearing of set 20 are made of a non-conductive material. Ball bearing set 30 is comprised of bearings 31 and 32, and a third bearing (not shown) each made of a non-conductive material. Ball bearing set 40 is comprised of bearings 41 and 42 and another (not shown),
each bearing made of an insulating material. Ball bearing set 50 is comprised of bearings 51 and 52, bearing 51 being made of a conductive material and the remainder of the set being made of a non-conductive material.
it should be noted that only two of the ball bearings in the above-noted arrangement, bearings 21 and 51, are electrically conductive. It is through these two bearings that current is made to pass from the terminals 6 and 14, through the associated strips 5 and 13 to the movable intermediate sphere 8 which serves as an electrical common.
The potentiometer of the invention operates as follows: By connecting the conductive sphere 8 to operate as an electrical common, two currents are made to flow through the potentiometer. The path followed by the first current includes the terminal 14, the portion of the helical strip 13 between the terminal 14 and the conductive ball 21, the conductive ball 21, and the movable sphere 8.
The path followed by the second current includes the terminal 6, the portion of the strip 5 between the terminal 6 and the conductive ball 51, the conductive ball 51 and the movable sphere 8.
Assuming an arrangement as described above, and which with the potentiometer in the position shown, the magnitude of the first current would depend on the resistance of that portion of the helical strip 13 between the terminal 14 and the conductive ball 21. it may be appreciated that if the sphere 8 is rotated in such a manner that the conductive ball 21 carried thereby also moves relative to the helical strip 13 the above discussed resistance will change since the length of the strip 14 between the terminal 13 and bearing 21 changes, there by altering the magnitude of the first current. It is, of course, possible to rotate the sphere 8 without altering the position of the ball 21 by using it as a pivot point about which the sphere 8 is rotated in which case no change will be made in the above-noted resistance offered to the first current despite rotation of the sphere.
In a similar manner, the second current noted hereinbefore is dependent in magnitude on the resistance of that portion of the helical strip 5 on the inner surface of the outer sphere 3 between the terminal 6 and the conductive ball bearing 51 in contact therewith. It may be seen that rotation of the movable sphere 8 about a pivot point other than the bearing 51 changes this resistance, thereby changing the magnitude of the second current.
A photoresist technique suitable for forming the helical conductive path on the inner surface of sphere 3 and the outer surface of the ball 12 is described in U.S. Pat. No. 3,615,470.
What is claimed is:
1. A potentiometer comprising:
a first hollow stationary sphere,
a first continuous convoluted strip of resistive material carried on the inner surface of said first sphere,
a first terminal means coupled to one end of said first strip of resistive material,
a stationary ball surface located within said first sphere,
a second continuous convoluted strip of resistive material carried by said ball surface,
a second terminal means coupled to one end of said second strip of resistive material,
a second hollow sphere, and
bearing means for mounting said second sphere for rotational movement intermediate said ball surface and said first sphere, said means including at least two conductive ball bearings, one in contact with said first strip and the other in contact with said second strip.
2. The combination recited in claim 1 wherein said first sphere defines an opening through which said sec ond sphere is manually adjustable.
3. The combination recited in claim 1 wherein said conductive ball bearings are carried by said second sphere.
4. The combination recited in claim 1 wherein said second sphere defines an opening through which extends a compression spring, said spring in contact with said first sphere and said ball surface.