Track ball device

Abstract: A selection device includes a trackball (10) rotatably mounted on rollers (12, 14). The rollers are connected with rotational encoders (16, 18) for producing a series of pulses. Up/down counters (20, 22) convert the pulses into an indication of translation along two axes. Downward, non-rotational pressure on the trackball causes a transducer (50) to output an electrical signal which is recognizable as a selection signal. In some embodiments, the transducer is a strain gauge or other transducer which provides an output whose magnitude varies with the amount of force. A comparator (54) compares the output of the transducer with a selectable threshold to indicate whether a selection signal is to be issued. In other embodiments, the transducer has two states, e.g. is a mechanical switch (70), and changes state in response to the force on the trackball exceeding a preselected minimum.

Description: The present invention relates to selection devices. It finds particular application in conjunction with multi-axis direction and motion encoding and selection devices and will be described with particular reference thereto. Heretofore, two and three-dimensional trackball selection devices have been readily available. Typically, a two-dimensional trackball was supported on two perpendicular rollers. Frictional engagement between the ball and the rollers caused rotation of the ball to be translated into corresponding rotation of each roller. More specifically, the rotation of each roller was indicative of rotation of the ball relative to an axis parallel to the central axis of the roller. Encoders were connected with each roller to convert the rotation of the corresponding roller into electrical signals, e.g. an electrical pulse signal for each increment of rotation. For a three-dimensional trackball, a third roller was typically positioned orthogonal to the other two to contact a side of the trackball. Commonly, the trackball has been utilized to move a cursor to selected regions of a video display. Upon reaching a desired position, e.g. a menu selection, the operator lifted his hand from the trackball and depressed a nearby selection button to indicate selection of the menu item associated with the cursor. One of the problems with lifting one's hand from the trackball is that the hand motion sometimes applied rotational forces to the ball causing it to reposition itself, i.e. the cursor moved. Other operators maintained contact with the trackball with the palm of the hand or some fingers while reaching for the selection button with another finger. In this manner, the operator was able to maintain continued contact with the trackball, hence continuous positional control of the cursor. However, reaching for the selection button sometimes caused unwanted rotation of the trackball. Not only was the separate selection device, typically a pushbutton, cumbersome, it was also more expensive to manufacture and produce. DE-A-3726939 discloses a control ball unit with a roller ball, with which by turning the freely rotating roller ball in two vertically opposing axes and located on a bearing, two independent value signals can be produced. The control ball unit further includes a power sensor, which on pressing the roller ball in the direction of a further axis produces a transmission signal. This document is used for the delimitation of claim 1. According to the present invention there is provided a selection device comprising: a ball member; means for rotatably supporting the ball member in a housing with a portion of the ball member extending from an upward side of the housing; means for converting rotational movement of the ball member into at least first and second signals indicative of rotation of the ball member relative to first and second axes, respectively; and a transducer means for converting non-rotational force on the ball member in excess of a preselected threshold level into an electrical selection signal, characterised in that: a hinge pivotally supports one side of the housing; and the transducer means supports the housing such that downward pressure on the ball member tends to rotate the housing about the hinge and apply force to the transducer means. In one particular device according to the invention the means for rotatably supporting the ball member includes at least two rollers and the rotational movement converting means include means for converting rotation of the rollers into a series of pulses and a resolver means for resolving the series of pulses into the first and second signals. In one such particular device the transducer means is connected between the housing and an associated structure. One advantage of the present invention is that it integrates the motion encoding and selection signal producing means. Another advantage of the present invention is that it eliminates the awkward repositioning of fingers for engaging a separate pushbutton or other selection device. True one hand (or even one finger) operation is possible. Another advantage of the present invention resides in its reduced cost. Another advantage of the present invention resides in its compactness. Two selection devices in accordance with the invention will now be described, by way of example, with reference to the accompanying drawings in which:- Figure 1 is an exploded view of a selection device, but not one of the two according to the invention; Figure 2 is a diagram of the first selection device of the two according to the invention; and Figure 3 is a diagram of the second selection device of the two according to the invention. Each of the devices comprises a multi-axis trackball assembly A which converts rotational movement into displacement or rotation relative to two or more axes, and a selection device B which converts non-rotational or downward force into a selection signal. With reference to FIGURE 1, the trackball assembly A includes a solid or hollow spherical member 10 of plastic or the like. The ball member 10 is supported on a first rod or roller member 12 and a second roller member 14 orthogonal to the first. The first roller member is connected with a rotation sensing means or encoder 16 for converting rotation of the first roller member into a first rotationally encoded signal, e.g. a train of pulses, each pulse indicative of a preselected angular increment of rotation in a direction perpendicular to the axis of the associated rod. A second rotation sensing or encoding means 18 converts rotation of the second rod into a second rotationally encoded signal. Optionally, a third rod may be mounted orthogonal to the first and second rods in contact with the ball member to drive a third rotation sensor or encoder means. Various rotation sensors may be utilized for generating a pulse train. For example, the rollers may rotate a disk with a series of apertures at even angular increments therearound. A light emitting diode on one side of the disk may transmit light through the apertures to a light sensitive diode or other light sensitive structure. The transmission and interruption of the light as the apertures and solid portions of the disk move between the light emitter and light sensor, generate the appropriate pulse train. By using a pair of photodiodes or other light detectors, a pair of pulse trains can be generated whose frequency varies with rotational speed and whose phase indicates the direction of rotation. A first resolving means 20 , such as an up/down counter is connected with the first rotation sensor 16 . A phase indication controls the counter to count up or down and each pulse increments the counter in the appropriate direction. In this manner, the first position resolver or counter converts the pulse train into an indication of rotation in a first direction. Analogously, a second resolver 22, such as an up/down counter, converts the output of the second resolver into an indication of movement relative to a second axis. Analogously, an additional resolver may be provided for converting movement of the ball relative to the third axis into a third relative position or movement indication. In FIGURE 1, encoding along a further axis is provided by a ring or collar 30 which surrounds the ball 10 and is rotatable independently thereof. A roller 32 engages the ring to move a rotation sensor or encoder 34 that generates a pulse train in accordance with the movement of the ring 30. Another up/down counter 36 converts the pulse train and phase information into an indication of the angular position of the ring 30. The selection device B produces a select signal or pulse in response to downward pressure on at least one of the ball member and the ring. It is to be appreciated, that downward pressure on the ball member causes a corresponding force to be exerted on the rollers 12, 14 on support posts and other structures 40 for the rollers, on ancillary support member 42 which with the rollers provides three-point support for the ball member, a housing 44, and the like. Downward force on the ball member can cause deflection of the rollers, deflection of the rollers within the support members 40, deflection of the support members, and the like. In Figure 1, a transducer 50, such as a strain gauge or other electric force sensor means, is affixed to one of the structures that are flexed, strained, or moved by force exerted on the ball member. The strain gauge 50 is connected with an amplifier 52 and a threshold comparing means 54. The threshold comparing means determines whether the sensed strain exceeds a selected, adjustable threshold. In this manner, the amount of force which must be applied to the ball to signal a selection is adjustable. Analogously, the selection device may include a ring force detector 60 such as a strain gauge or mechanical switch which is interconnected with the ring 30. The force detector might be located below the ring member, on a mounting structure 62 for the ring member motion sensing or encoding transducer 34, or the like. The ring member force detector 60 is connected with an amplifier 63 and a comparing means 64. The comparing means 64 compares the signal from the strain gauge 60 with an adjustable threshold or reference value. A means 66 transforms the counts of counters 20, 22, 36 to x, y and z (or ) coordinate values and the outputs of threshold circuits 54, 64 to select or enable signals, such as a "0" or a "1", on or off, etc. In the embodiment of Figure 2, the trackball housing is mounted on a hinge 80 adjacent one side thereof. A mechanical switch 82 supports the other side. Downward pressure on the trackball urges the trackball assembly A to pivot relative to the hinge, changing the state of the mechanical switch 82. With reference to Figure 3, the trackball assembly A is mounted on an arm member 90. The arm is supported by a hinge 94. A movement detecting transducer 96 is disposed between the arm and an associated stationary housing 98 to be compressed by downward pressure on the trackball assembly. Various types of transducers are contemplated. As illustrated above in the specific examples, mechanical switches and strain gauges may be used. Various other types of transducers such as inductive pick-ups which sense relative movement of a magnetic or ferrous member, capacitive pick-ups which sense proximity or relative movement of two plates or portions of a capacitor, Hall effect transducers which detect movement of a magnet, piezoelectric transducers which generate electrical potentials in response to pressure, and the like.

Claims: A selection device comprising: a ball member (10); means (12, 14, 42) for rotatably supporting the ball member (10) in a housing (A) with a portion of the ball member (10) extending from an upward side of the housing (A); means (16, 18, 20, 22) for converting rotational movement of the ball member (10) into at least first and second signals indicative of rotation of the ball member (10) relative to first and second axes, respectively; and a transducer means for converting non-rotational force on the ball member (10) in excess of a preselected threshold level into an electrical selection signal, characterised in that: a hinge (80, 94) pivotally supports one side of the housing (A); and the transducer means (82, 96) supports the housing (A) such that downward pressure on the ball member (10) tends to rotate the housing (A) about the hinge (80, 94) and apply force to the transducer means (82, 96). A device according to Claim 1, wherein the means (12, 14, 42) for rotatably supporting the ball member (10) includes at least two rollers (12, 14) and wherein the rotational movement converting means (16, 18, 20, 22) include means (16, 18) for converting rotation of the rollers (12, 14) into a series of pulses and a resolver means (20, 22) for resolving the series of pulses into the first and second signals. A device according to Claim 1 or 2, wherein the transducer means (82, 96) is connected between the housing (A) and an associated structure (98). A device according to any one of the preceding claims, wherein the transducer means (82, 96) includes at least one of a mechanical switch, a strain gauge, a Hall effect transducer, a piezoelectric transducer, an inductive transducer, a capacitive transducer, and an optical transducer. A device according to any one of the preceding claims further including: a ring member (30) mounted around the ball member (10) for rotation independently thereof; and means (32, 34) for converting rotational movement of the ring member (30) into a signal indicative of rotation of the ring member (30) relative to a third axis.

Inventors: CECIL ROBERT A, MAILEY FREDERICK C, CECIL, ROBERT A., MAILEY, FREDERICK C.
Applicants: PICKER INT INC, PICKER INTERNATIONAL, INC.
Application year: 1992
Main classification: G06F3
IPC codes: G06F3