Abstract:
A gel cushion that can be attached to an existing cursor pointing device (control stick) on a computer or keyboard, or be integrally formed with the cap during manufacture. The gel cushion is flexible enough to prevent tissue damage to the user&#39;s fingers due to repetitive motions over an extended period of use, yet firm enough to transmit the desired pressure to the control stick. The gel cushion designed to be used on an existing control stick can be applied with an adhesive to a cap, or with a frictional fit directly to the control stick. The gel cushion is designed to be easily installed and replaced when worn.

Description:
“CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation-In-Part of Application No. 09/281,126 filed Mar. 29, 1999, now U.S. Pat. No. 6,140,998, which was a Divisional of Application No. 08/717,220 filed Sep. 26, 1996, now U.S. Pat. No. 5,889,508.” 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates in general to a computer input device, and in particular to a cursor pointing device (cursor control stick), of a notebook-type portable computer or similar device. 
     A finger mouse or cursor control stick, as used in this application, is a man-machine interface device which controls the motion of a computer display cursor. In particular, a control stick is a type of miniature joy stick which is intended to be operated by the tip of one finger of the user. 
     Typically, a control stick is mounted in a central location on a computer keyboard, such as between the “G”, “H” and “B” keys on a standard “QWERTY”-type keyboard. The control stick has a position sensing mechanism which detects horizontal pressure in any horizontal direction. The cursor moves in a direction that corresponds to the direction of pressure exerted on the control stick and, in some embodiments, at a speed that corresponds to the amount of pressure exerted on the control stick. The control stick includes an elongated shaft. The shaft of the control stick has a small diameter, thus allowing the control stick to be mounted between the keys of the computer keyboard without causing the placement of the keys to vary greatly from that expected by an experienced user. A cap is typically removably mounted on the upper end of the control stick shaft, in order to provide an enlarged contact surface for a user to press against on the small diameter shaft of the control stick. 
     SUMMARY OF THE INVENTION 
     Some models of control sticks have a cap with a hard smooth surface, which became slippery during use from perspiration or a build-up of natural body oils. Thus a user has to press their finger with relatively great force against the cap to prevent their finger from slipping on the surface of the cap. The need to press hard on the cap makes control difficult, since the user cannot use the finesse and delicate movements typically needed for rapid, accurate cursor movement. Also, pressing hard on the control stick is physically tiring to the finger, hand and forearm muscles of a user, and caused irritation, inflammation, and bruising of the finger tissue after a period of extended use. 
     A period of extended use, as used in this application, means a period of use of more than about one hour, and generally more than four hours and less than twelve hours. During such period of use, the user frequently manipulates the control stick. The frequency of manipulation of the control stick during a representative task, such as word processing, will typically be at least every ten minutes, on average, and may be much more frequently, depending on the particular task and the particular user. 
     Another type of a cap for a control stick has a textured outer surface. For example, one known control stick is equipped with a cap which is stippled with bumps which are about the same size and spacing as the abrasive on 150 grit sandpaper. While this approach may help prevent the slipping common with the earliest model cap, the textured cap is still irritating to the finger of a user when used extensively, even with the lighter touch allowed by the textured surface. The uneven and relatively hard surface of such caps still can cause inflamed tissue, bruising, soreness and finger fatigue in users which limits their ability to comfortably use such a control stick for periods of extended use. 
     The present invention provides a “cushioned” cap for a control stick, which cap may suitably may be formed at least partially of a gel material, with a surface which provides the needed finger to cap friction to easily use the control stick to move the cursor with a light touch, and which is formed of a relatively soft material so that the cap does not irritate the body tissues of the user or result in finger fatigue, even after periods of extended use. 
    
    
     Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a typical portable computer employing a control stick having a cushioned cap in accordance with this invention. 
     FIG. 2 is a side view, partly in section, of the control stick illustrated in FIG.  1 . 
     FIG. 3 is an enlarged sectional side view of the cap and the control stick illustrated in FIGS. 1 and 2. 
     FIG. 4 is a side view of the cushioned cap illustrated in FIGS. 1 through 3. 
     FIG. 5 is a sectional side view of a second embodiment of a cushioned cap in accordance with this disclosure. 
     FIG. 6 is a bottom plan view of the cap illustrated in FIG.  5 . 
     FIG. 7 is a flowchart illustrating a method of manufacturing a control stick in accordance with this disclosure. 
     FIG. 8 is perspective view of a gel cushion for a keyboard cursor control stick. 
     FIG. 9 is a side sectional view of the gel cushion of FIG.  8 . 
     FIG. 10 is a view similar to FIG. 9, except showing an alternate embodiment of the gel cushion. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings, FIGS. 1 through 6 illustrate a first embodiment of a control stick, indicated generally at  10 , according to this invention. The illustrated control stick  10  is a miniature joy stick, such as the TrackPoint, TrackPoint II, or TrackPoint III control sticks on notebook computers sold by the International Business Machines Corporation. However, it will be appreciated, in light of the following disclosure, that the invention may be practiced on control devices other than such miniature joy sticks. 
     The control stick  10  is mounted in a keyboard  12  of a typical notebook-style microcomputer  14  having a pivotally mounted video screen  15 . The control stick  10  is mounted at a first end (not shown) to the microcomputer  14 , between the keys of the keyboard  12 . A cap  18  is removably mounted on the other end  21  of the control stick  10 . The control stick  10  is usually made of a plastic material, and translates the pressure on the cap  18  into a command to move a cursor on a video display of the computer  14 . 
     The cap  18  of the control stick  10  is made of a relatively hard elastomeric material. At least a central portion of the outer surface  17  of the cap  18  is provided with an attached cushion  20 . The cushion  20  can be made of any resilient material that can be attached to the outer surface  19  of the cap  18 . 
     Examples which may be suitable materials include soft rubber, soft foam, and polyurethane foam. The preferred material for the cushion  20  is polyurethane foam such as the type used in expandable ear plugs. This type of foam product provides a surface that is relatively soft so as to not damage the tissues in the finger of a user during periods of extended use. 
     Hardness can be characterized by measuring the force applied to a given area which is required to compress or deflect a material a given distance. For example, a typical prior art cap, such as a cap supplied with the TrackPoint II control stick, is made of a relatively hard elastomeric material. During testing, a probe having a contact surface of approximately 1 mm 2  was pressed against such a cap to cause the probe to deflect the surface of the cap approximately 0.25 mm. A force of approximately 15 grams was required to compress the surface of the cap inwardly this small amount. In contrast, one embodiment of the cushion  20  of the present invention required a force of only 5 grams to be exerted by the probe to compress the surface of the cushion  20  the same distance. According to the invention, a cushion  20  having a hardness which would permit a probe having a contact surface of approximately 1 mm 2  to deflect the surface of the cushion  20  by at least 0.25 mm when urged by a force of 10 grams would generally be acceptable. The preferred embodiment of the invention has a hardness such that only 5 grams of force is required to cause a probe having a contact surface of 1 mm 2  to deflect the surface of the cushion  20  by at least 0.25 mm. 
     Preferably, the cushion  20  also provides a high coefficient of friction with the user&#39;s finger to permit easy positioning of the control stick  10 . The polyurethane foam of the cushion  20  is yielding to a degree dependent upon the thickness of the cushion  20 . The thickness of the cushion  20  can easily be modified during manufacture to any desired thickness. 
     Referring to FIG. 2, when the display  15  is folded down over the keyboard  12  for storage, as is typical for most notebook computers, the display  15  may contact the cushion  20 . The cushion  20  is flattened as indicated by the phantom line  19 , but will resiliently return to the position indicated by the solid outline of the cushion  20 . The resiliency of the cushion  20  allows the cap  18  to have an enlarged contact surface area and greater height above the keyboard  12  for increased comfort of the user, without having to increase the spacing between the screen  15  and the keyboard  12 . It will be appreciated by those skilled in the art that the cushion  20  will preferably not be made from a material which would damage or stick to the display  15  if the display  15  contacts the cushion  20 . 
     Referring to FIGS. 3 and 4, the cushion  20  is, preferably, a disk of material having a generally semi-circular cross section. However, the cushion  20  may have any suitable shape, such as that of a flat-ended or hollow-ended cylinder. In the illustrated embodiment, the cushion  20  has a convex end  22 , and a second end  24 . The convex end  22  is the contact surface of the cushion  20 , that is, the surface that the user of the control stick  10  will contact to move the control stick  10 . The convex end  22  will generally be a surface providing a good frictional interface. In the preferred embodiment, the convex end  22  is a sealed, smooth, easily cleaned surface, such as a closed cell skin formed on a polyurethane foam. The resiliency of the cushion  20  permits the cushion  20  to be deformed and still provide excellent friction, even when the surface thereof is smooth. However, if desired, the surface of the convex end  22  may be textured or knurled. The second end  24  of the cushion  20  will be attached to the outer surface  19  of the cap  18  on the control stick  10 . In the preferred embodiment, a suitable adhesive is used to attach the cushion  20  to the outer surface  19  of the cap  18 . 
     FIG. 5 is a sectional view of a second embodiment of the cushion of this invention, indicated generally at  30 . The cushion  30  is generally cylindrical and includes a convex end  32 , and a relatively flat end  33  opposite the end  32 . Although in the illustrated embodiment the end  32  is convex, the end  32  may be formed to any suitable shape, such as a flat or a concave surface, as may the end  22  of the cushion  20 . 
     A recess  34  is defined in the cushion  30 , which generally conforms to the outer surface of the end  21  of the control stick  10 . For example, as shown in FIG. 6, the recess  34  may have a square perimeter, if the end  21  of the control stick  10  is square in cross-section. The control stick  10  extends into the recess  34 . Preferably, to install the cushion  30  onto the control stick  10 , a suitable adhesive is applied to the upper end  21  of the control stick, to the interior surface of the recess  34  in the cushion  30 , or to both the upper end  21  of the control stick and to the interior surface of the recess  34  in the cushion  30 . The cushion  30  is placed on the end  21  of the control stick  10  so that the cushion  30  adheres to the end  21  of the control stick  10 . Of course, the cushion  30  could also be affixed to the control stick  10  by a resilient fit between the recess  34  of the cushion  30  and the end  21  of the control stick  10 . The cushion  30  is comprised of a soft material to permit use for an extended period of time without causing irritation to the finger tissue. 
     It may be desirable to manufacture the cushion  30  with portions having different levels of hardness. For example, the convex end  32  could be softer than the area of the cushion  30  surrounding the recess  34 . The harder area surrounding the recess  34  would assist in retaining the cushion  30  on the control stick  10  by maintaining its form, while the convex end  32  of the cushion could be relatively soft. 
     One method of manufacturing the cushion  30  with portions having different levels of hardness would involve simultaneously injecting two separate types of material simultaneously into a cavity of single mold to form the cushion  30 . For example, a first material having relatively soft properties would be injected in the mold at the area where the convex end  32  is formed, and a second material which is harder than the first material would be injected in the mold at the area where the recess  34  is formed. Accelerating agents, compatabilizing agents, fillers, mold release agents, and coloring agents can be introduced as well, as will be appreciated by those skilled in the art. Somewhere between the two ends  32  and  33 , the first and second materials come into contact and become affixed to one another. The cushion  30  would, therefore, be a single structure formed from two different materials, having different hardness characteristics when set or cured. For the purposes of the present invention, curing can be accomplished by using any suitable methods of solidifying or hardening a material, such as for example, by adding or removing heat, inducing a catalytic reaction, or containment for a period of time to allow hardening to occur. 
     Another method of manufacturing the cushion  30  having multiple areas with different levels of hardness would be to form the cushion  30  from a single material, but altering the setting or formation of the material so that the different areas have different hardness characteristics. This alteration of the formation process can be accomplished by varying the temperature gradient surrounding the mold, creating miniature air pockets within selected portions of the material, or by any other suitable manufacturing process. 
     As an alternate embodiment, it is contemplated that a cushion of the invention could be formed to completely encompass the cap  18  shown in FIGS. 2 and 3, except where the shaft of the control stick  10  extends outwardly therefrom. Such a cushion would have a cavity therein which includes a flange of material about an opening into the cavity. Such a flange of material would restrict the size of the opening into the cavity to a diameter which is less than the diameter of the cap  18 , and thus retain the cushion on the cap  18 , either alone or in combination with a suitable adhesive. The opening into such a cushion could be resiliently expanded to slip the cushion onto the cap  18  during assembly, or when the cushion is replaced. 
     Although the preferred embodiment of the cushion  20  or  30  is for use on a portable notebook computer  14 , it is envisioned that the cushion  20  or  30  could be used on any keyboard or in any convenient location on any instrument requiring a control stick-like movement. 
     It is contemplated that the cushions  20  or  30  of the present invention can  20  be sold separately from a notebook-type portable computer as replacements or substitutes to the original control stick and cap configuration. The cushions  20  or  30  can be sold in a kit form which preferably includes the necessary materials to affix the cushions  20  or  30  to a control stick of a computer. The kit may include a plurality of cushions  20  or  30  and a suitable adhesive material, such as a container of contact cement or a pressure sensitive self-adhesive strip which is pre-applied to the cushions  20  or  30 . For example, if contact cement is supplied with the kit, the user simply applies a coating of contact cement to either the originally supplied cap  18  or the end  21  of the control stick  10 , depending on the type of cushion  20  or  30  used. A coating of contact cement is also applied to the cushion  20  or  30 . The coatings of contact cement are then allowed to dry. The cushion  20  or  30  is then pressed against the coated portion of the original cap  18  or control stick  10 , thereby affixing the cushion  20  or  30  to the control stick  10 . 
     FIG. 7 is a flow diagram of a method of forming a cushioned control stick according to the invention. The method of forming a cushioned control stick may be summarized as follows: In a first step  100 , a cursor pointing device (control stick) with a cap having a first hardness is provided. In a second step  200 , a soft cushion is provided which has an outer surface of a second hardness which is less than the first hardness of the cap (i.e., the cushion is softer than the cap). In a third step  300 , the soft cushion is affixed to the relatively harder cap. 
     It will be appreciated that the soft cushions described above may be formed in a variety of ways, of a variety of materials. For instance, in an embodiment shown in FIG. 8, a cushion  400  is formed of a gel material. As used herein, the term gel means a semi-rigid solid, and includes a colloidal suspension of a solid dispersed in a liquid, and materials with similar characteristics as load bearing surfaces (e.g., stiffness, hardness, malleability, etc.). 
     The cushion  400  preferably has a generally cylindrical lower portion  402 , and a generally conic upper portion  404 , which increases in diameter toward an upper surface  406  of the cushion  400 . The upper surface  406  is preferably formed with a depression  408  therein that is suitable to receive a fingertip of a user. 
     Like the cushions described in the other embodiments above, the cushion  400  will deform when pressed against the computer display screen with it&#39;s and will still be safe for the computer video screen  15 . It is contemplated that the cushion  400  may be manufactured to have a suitable relatively rigid pocket (seen in FIGS. 9 and 10) to accept the upper end of a control stick of a computer, such as the control stick  10 . It is also contemplated that the cushion  400  could otherwise be fixed to a control stick cap like the cap  18  in FIG. 2, such as by adhesively fixing the cushion  400  to the cap. It is also contemplated that the cushion  400  may be manufactured to form an integral part of a removable control stick or portion of a control stick (not shown). 
     FIG. 9 is a cross sectional view of the cushion  400 . The upper portion  404  of the cushion  400  is made from a different material than the lower portion  402 . The upper portion  404  may be made from any suitable material. It is believed that thermoplastic elastomeric compounds such as KRATON® thermoplastic elastomers (available from the Royal Dutch/Shell Group) may be particularly suitable for this application. The material from which the upper portion  404  is formed is selected to have a relatively low hardness, so that the upper portion  404  is relatively soft and compliant. Thus the material of the upper portion  404  may be said to be a gel. The lower portion  402  defines a pocket  410  in a lower surface  412  thereof. The pocket  410  is adapted to receive the upper end of a cursor control stick, such as the cursor control stick  10 . The lower portion  402  is preferably formed of a material with a higher durometer than the upper portion  404 . The lower portion  402  may, nevertheless, be formed of any suitable material. It is believed that thermoplastic rubber compounds such as SANTOPRENE® thermoplastic rubber (available from Advanced Elastomer Systems, L. P., 388 South Main Street, Akron, Ohio, U.S.A. 44311) may be particularly suitable for this application. These thermoplastic elastomeric and rubber materials are believed to be particularly suitable because of the tack their surfaces have, which gives the cushion  400  a smooth, non-irritating, yet non-slip surface for improved performance. 
     The cushion  400  may be formed by any suitable process on standard thermoplastic equipment. Thermoplastic rubber compounds, for example, can be injection molded, extruded, blow molded and thermoformed with the efficiency and economy associated with thermoplastic materials. In a preferred process, the cushion is formed in a two step injection molding process. In a first step, the lower portion  402  is formed by injection molding. As soon as the lower portion  402  has cured sufficiently to be parted from the mold, the lower portion  402  is placed in a second mold, and the material forming the upper portion  404  is injected into the second mold. The upper portion  404  is thus overmolded onto the lower portion  402 , with the material of the upper portion chemically bonding with the material of the lower portion. The completed cushion  400  is then allowed to fully cure. 
     An alternate embodiment of the cushion  400  is illustrated by the cross sectional view of FIG. 10. A cushion  400 ′ is similar in outer shape to the cushion  400  illustrated in FIG. 8, and has similar qualities of deformation for comfort and protection of computer video screens, and smoothness and tack for ergonomic reasons. However the cushion  400 ′ is constructed somewhat differently, as will be described. 
     Like the cushion  400 , the cushion  400 ′ preferably has a generally cylindrical lower portion  402 ′, and a generally conic upper portion  404 ′, which increases in diameter toward an upper surface  406 ′ of the cushion  400 ′. The upper surface  406 ′ is preferably formed with a depression  408 ′ therein that is suitable to receive a fingertip of a user. 
     The lower portion  402 ′ of the cushion  400 ′ is formed of any suitable material, and, like the cushion  400 , is preferably formed of a thermoplastic rubber compound such as SANTOPRENET® thermoplastic rubber. The lower portion  402  defines a pocket  410 ′ in a lower surface  412 ′ thereof. The pocket  410 ′, like the pocket  410  in the cushion  400 , is adapted to receive the upper end of a cursor control stick, such as the cursor control stick  10 . 
     The upper portion  404 ′ of the cushion  400 ′ is of somewhat different structure that the cushion  400 . The outer surface of the upper portion  404 ′ is an envelope  428  which may be formed of any suitable material. It is believed that a thermoplastic rubber compound such as SANTOPRENE® thermoplastic rubber would be suitable in this application, and the envelope  428  is preferably formed integrally with the lower portion  400 ′. The envelope  428  is filled with a suitable material  430 . The material  430  may be any suitable gel, such as a silicone gel, or a thermoplastic elastomeric compound such as KRATON® thermoplastic elastomer formulated to give a very low hardness (i.e., very soft) gel material. 
     In summary, various aspects of this invention include: 
     A control stick with a contact surface which is relatively soft and non-irritating to the body tissue of a user. 
     A cushion for a control stick, the cushion being softer than the control stick. 
     A cushion for a control stick, the cushion being formed of a gel material softer than the control stick. 
     A control stick cushion which can contact a display screen of a computer display, deform elastically, and not damage the display screen. 
     A cap for a control stick, joy stick, or similar device which is soft and non-irritating to the body tissue of a user during extended periods of normal use. 
     In accordance with the provisions of the patent statutes, the principle and mode of operation of this invention have been explained and illustrated in its preferred embodiment. However, it must be understood that this invention may be practiced otherwise than as specifically explained and illustrated without departing from its spirit or scope.