Abstract:
The disclosure describes a button wheel. The button wheel comprises a support frame including a pair of parallel opposed inner surfaces. A platform is nestably mounted in the support frame. The platform includes a pair of parallel opposed outer surfaces forming a pair of linear bearings with the parallel opposed inner surfaces of the support frame to allow the platform to translate from a biased rest position in a direction parallel to the opposed inner surfaces and the opposed outer surfaces. The button wheel also includes first and second spaced apart mounts fixed to one of the support frame and said platform. The button wheel includes a shaft disposed along an axis and including a first end rotatably engaged in the first mount and a second end rotatably engaged in the second mount. A wheel is mounted on the shaft and a rotation sensor is in operative communication with the wheel. The button wheel also includes a translation sensor coupled between the support frame and the platform.

Description:
BACKGROUND 
     This application relates to an electronic device capable of sensing rotary and push-type user inputs. 
     The button-wheel is a device that can sense continuous rotation about a rotational axis as well as switch action in a direction perpendicular to the rotational axis; it increases user efficiency by enabling users to transmit two distinct types of input to a host machine while interacting with only one device. 
     Button-wheels are also related to knob-buttons that include rotational knobs that support a switching function perpendicular to the axis of rotation. These knob-buttons typically actuate switches through movement of knobs and knob mountings. 
     Button-wheels are currently prevalent in cursor control devices such as computer mice. Most conventional mouse button-wheels possess a configuration and switch actuation method similar to the one described in U.S. Pat. No. 5,912,661 to Siddiqui and illustrated in FIG.  1 . The button-wheel is built on a circuit board  28  that physically supports both mechanical and electrical components while placing button-wheel sensors in electrical communication with the rest of the mouse. The wheel  22  has a diameter that is much greater than its width. Wheel  22  is mounted on a relatively rigid shaft  64  that is much longer than wheel  22 &#39;s width. Shaft  64  is held in place by two bearings that allow shaft  64  to rotate about its axis, but not translate along this axis. 
     A first bearing  32  further constrains a first end  991  of shaft  64  from moving in the other two translational directions; however, first bearing  32  does not prevent shaft  64  from tilting about first bearing  32 . A second bearing is formed by two distinct components: a spring  58  that biases second end  992  and wheel  22  toward the user, and a slotted shape  34  that constrains second end  992 , such that it can translate only within the slot cutout. The slot cutout is a straight slot that is perpendicular to the axis of shaft  64 ; this limits the motion of second end  992  to almost directly towards or away from circuit board  28 . Shaft  64  also has a collar-type feature  50 , located near slotted shape  34 , that hovers above a button  51  of switch  52 . 
     With this configuration, when the user pushes on wheel  22 , shaft  64  tilts about first bearing  32  and sweeps a wedge-shaped section of a circle. Shaft  64  compresses spring  58 , and collar  50  touches and depresses button  51  to actuate switch  52 . The magnitude of shaft  64 &#39;s tilt is limited by the length of the slot in slotted shape  34 , the full compression distance of spring  58 , and the actuation distance of button  51 . Spring  58  and button  51  together generate the desired user tactile and auditory feedback for this switch actuation action. Conductive paths along the circuit board  28  route the button signals to the mouse electronics (not shown). 
     Also on shaft  64  is an encoder disc  44 , which forms a complete optical rotary encoder with an optical emitter  46  and an optical detector  48 . Shaft  64  further contains a series of grooves that interact with a ratchet-like feature  42  to form a detent mechanism. When the user rotates wheel  22 , the encoder assembly (formed by encoder disc  44 , optical emitter  46 , and optical detector  48 ) produces digital signals that are typically quadrature in nature. The detent mechanism (formed by grooves  40  and ratchet  42 ) generates the desired user tactile and auditory feedback for the rotational motion. Conductive paths along the circuit board  28  route the encoder signals to the mouse electronics (not shown). 
     Variations on this general button-wheel idea are known in the art. The simplest variations involve using different types of the basic components (such as mechanical encoders instead of optical encoders, ball detents instead of grooves and ratchets, and lever-type switches instead of pushbutton switches) and shifting their relative location (such as moving switch  52  to the other side of slotted shape  34  or placing encoder disc  44  to the opposite side of first bearing  32 ). 
     Slightly more complex variations involve combining many components into one integral unit. U.S. Pat. No. 6,188,393 to Shu, U.S. Pat. No. 6,157,369 to Merminod et al., and U.S. Pat. No. 6,014,130 to Yung-Chou describe devices in which the encoder disc (analogous to encoder disc  44  of the Siddiqui patent &#39;661) is constructed as part of a wheel (analogous to wheel  22  of the Siddiqui patent &#39;661). The devices outlined in U.S. Pat. No. 6,285,355 to Chang and U.S. Pat. No. 5,808,568 to Wu combines at least part of the detent mechanism with the encoder disc and the wheel (analogous to grooves  40 , ratchet  42 , encoder disc  44 , and wheel  20  of the Siddiqui patent &#39;661) to generate one integral unit. 
     Other button-wheel variations involve different switch actuation actions. For example, U.S. Pat. No. 5,473,344 to Bacon et al. describes another tilting-shaft switch actuation method in which an additional slotted shape is utilized, and U.S. Pat. No. 5,446,481 to Gillick et al. discloses an hourglass-shaped wheel that tilts about its center to actuate switches located under either side of the hourglass-shaped wheel. These alternative tilting-shaft devices are more complex and require more components than the device presented in Siddiqui patent &#39;661. 
     In addition to the tilting switch actuation action, alternatives that include semi-tilting switch actuation mechanisms also exist. Both U.S. Pat. No. 6,246,392 to Wu and U.S. Pat. No. 6,188,389 to Yen disclose button-wheels in which the two bearings supporting the wheel shaft include slotted shapes that have slots which help guide the motion of the wheel shaft; the devices disclosed in the Wu patent &#39;392 and the Yen patent &#39;389 bias the wheel shaft toward the user with one single spring located on one side of the wheel. The Merminod patent describes a different system that utilizes only one slotted shape; the end of the wheel opposite to the slotted shape is attached to a formed spring, and can move in a manner limited by the deflection of the spring. Since all three of the Wu patent &#39;392, the Yen patent &#39;389, and the Merminod patent &#39;369 teach biasing the wheel toward the user on only one side of the wheel, a torque results when the user pushes on the wheel of any of these disclosed devices, and significant tilting of the wheel occurs. Thus, the action associated with these switch actuation inputs combines tilting as well as translation, and can be considered semi-tilting. 
     Minimally-tilting switch actuation mechanisms also exist. For example, U.S. Pat. No. 6,292,113 to Wu (Shown in FIG.  2 ), U.S. Pat. No. 6,285,355 to Chang, U.S. Pat. No. 6,188,393 to Shu, U.S. Pat. No. 5,530,455 to Cillick et al., and older Microsoft® INTELLIMOUSE all disclose button-wheels in which the entire wheel mounting moves to achieve switch actuation. In order to enable the movement of the entire mounting, these devices tend to be larger, more complex, and more costly than the device of the Siddiqui reference. In the devices disclosed by the Wu patent &#39;113, the Chang patent &#39;355, and older INTELLIMOUSE, these wheel mountings are biased toward the user by one spring located on one side of the wheel. In contrast, in Gillick &#39;455&#39;s and Shu &#39;393&#39;s devices, the mountings are biased toward the user on both sides of the wheel. With biasing forces on both sides of the wheel, where user push-type forces are applied, the wheel mounting can respond to user push-type force with motion that is more translation than tilting. With this substantially translational motion, in which translation is the primary action of switch actuation, it is possible to produce tactile force and displacement responses that are more uniform across the width of the wheel. However, this additional biasing force usually increases the size, complexity, and cost of the mechanism beyond that associated with a single biasing force as will be explained later in the disclosure. 
     Despite these numerous button-wheel designs, the general tilting-shaft button-wheel idea and configuration described by Siddiqui is still currently the most popular commercial button-wheel embodiment. This is largely because button-wheels are mostly used in mice, and the Siddiqui device is a low-cost and low-complexity device that satisfies mouse design criteria. 
     Mice have minimal space constraints, since they must be at least a minimum external size for ergonomic reasons. This external size leads to internal spaces that are typically much larger than necessary to accommodate the sensors, structures, mechanisms, and electronics associated with conventional mouse features. Faced with this minimal space constraint, conventional mice have focused on minimizing cost and complexity instead of size. Thus, the internal components of mice are usually larger, cheaper, and easier to assemble than those found in more space-constrained input devices, such as PDA touch screens, laptop pointing sticks, and computer touchpads. This minimal space constraint has also affected the development focus of button-wheels in prior art devices. Siddiqui&#39;s device, along with the variations described above, focus on reducing the cost and complexity of the button-wheel, often at the trade-off of increased mechanism size. 
     Mice also have relatively minimal constraints on uniform displacement and force feedback to the user, which makes tilting and semi-tilting button-wheel devices viable devices. Tilting and semi-tilting systems provide varying displacement and force feedback across the width of the wheel; the wheel shaft acts as a lever arm about the center of tilt and scales the force and displacement feedback as dictated by geometry. However, since the width of the wheel is small compared to its lever arm, the differences in force and displacement tactile feedback along the width of the wheel are small and almost unnoticeable to the user. These minimal uniform feedback constraints have enabled mouse button-wheels to utilize simpler mounting designs and fewer components than if uniform feedback were required. 
     Unlike mouse button-wheels, many input devices must provide uniform force and displacement feedback. For example, some computer keyboards contained space bars that tilted about their centers. These space bars were unsatisfactory, since they were long enough such that the non-uniform feedback across the width of the space bar were noticeable to the user—some of these space bars even jammed when they were depressed on their left or right edges. In response, keyboard makers introduced a host of different linkages and mechanisms to ensure uniform feedback across the width of the space bar, and space bars that tilted about the center are no longer used. 
     Although the above observations have highlighted computer mice because button-wheels are most often found in mice, the same observations also apply to any device similar to mice in terms of size and feedback constraints. Examples of such devices include, but are not limited to, trackballs, handheld videogame control pads, and joysticks. However, these minimal constraints on size and feedback will not always apply. For example, as computer mice and similar devices grow in complexity to incorporate features such as wireless communications and force feedback, space constraints will grow tighter. 
     Existing devices such as Personal Digital Assistants (PDA) and laptops also have very tight—especially height to reduce the overall thickness of the PDA or laptop-space constraints. In addition, devices such as PDAs and laptops may best be served by button-wheels with wider wheels and lower ratios of wheel diameter to wheel width and shaft length to wheel width. These lower ratios help the button-wheels meet tighter space constraints and allow users to manipulate the button-wheels in more ways. Unlike button-wheels for mice, which are usually manipulated by one or two dedicated digits, button-wheels for PDAs and laptops may be located where users can access them with thumbs, multiple fingers, or either hand. 
     These lower ratios of wheel diameter to wheel width and shaft length to wheel width also mean tighter feedback requirements that make tilting and semi-tilting designs much less desirable. With these lower ratios, a tilting or semi-tilting design would yield a greater difference in force and displacement feedback along the width of the wheel than a similar design targeted for mice. This difference may be noticeable and disturbing to users. At an extreme case for a tilting shaft system, the user may not be able to actuate the button near the center of tilt, or may jam the button-wheel at the end opposite that of the center of tilt. These failure modes are similar to those of space bars that tilted about their centers, and accentuate the importance of uniform force and displacement response in button systems where the component that interacts with the user is relatively wide. 
     Button-wheels utilizing tilting or semi-tilting designs have a further disadvantage in that they usually need to accommodate a vertical travel height that is greater than that traveled by the wheel during switch actuation. The actual difference is dependent on the lengths of the lever arms from the center of pivot to the wheel and to the farthest pivoting or semi-pivoting point. For example, in a design with a tilting-shaft approach and a wheel mounted equidistant between two bearings, the vertical distance traveled by the section of the shaft within the bearing that does not function as the fulcrum is approximately twice that of the wheel. Mounting the wheel at the section of the shaft that travels the greatest distance during the tilting or semi-tilting switch actuation action (typically one of the end sections of the shaft) may reduce the motion that must be accommodated by the button-wheel during switch actuation. However, this approach also introduces undesirable characteristics associated with a cantilevered-wheel system. 
     The ideal button-wheel for this set of design criteria associated with applications similar to PDAs and laptops is one that minimizes size (especially height), ensures that no parts of the button-wheel need to travel more than the wheel during switch actuation, and provides uniform force and displacement feedback to the user during switch actuation. The ideal button-wheel also minimally increases the complexity and cost of the button-wheel. 
     Some prior-art devices do attempt to address some of the tighter space constraints, but they still utilize tilting as the main switch actuation mechanism. For example, U.S. Pat. No. 6,198,057 to Sato et al. (Shown in FIG. 3) and U.S. Pat. No. 6,194,673 to Sato et al. both shrink a tilting-shaft design by utilizing smaller parts and integrating multiple components into one mechanism; for example, the device of Sato &#39;057 uses smaller mechanical and electrical components, removes the biasing spring and uses the switch as the biasing agent, replaces the optical wheel encoder with a mechanical one, and combines the mechanical encoder, detent, and bearing into one integral part. 
     Even though these two devices of Sato &#39;057 and Sato &#39;673 do shrink the size of the button-wheel noticeably, they do not address the shortcomings of a tilting or semi-tilting mechanism as outlined above. Both devices by Sato &#39;057 and Sato &#39;673 must be tall enough to accommodate the greater vertical distance traveled by the end of the shaft opposite from the center of tilt, which is greater than the actual vertical distance traveled by the wheel. In addition, these systems still have an inherently nonuniform tactile response across the width of the wheel. 
     Another button-wheel design that attempts to fit within the tighter space constraints is U.S. Pat. No. 6,211,474 to Takahashi. Takahashi&#39;s device is similar to the tilting-shaft design described by the Siddiqui patent&#39;661with one exception. The wheel can tilt about the center of the wheel shaft as well as tilt about one of the bearings. Takahashi&#39;s device has the same deficiencies as both of the devices outlined by Sato &#39;057 and Sato &#39;673, and is more complex and even less uniform in tactile response to accommodate the additional degree of wheel tilt freedom about the center of the shaft. 
     A device that attempts to fit within the tight space constraints and does not use shaft tilt to actuate the button is U.S. Pat. No. 6,218,635 to Shigemoto et al. (Shown in FIG.  4 ). Shigemoto &#39;635 describes a mechanism in which the entire wheel mounting is located above a switch. When the user pushes on the wheel, the entire wheel mounting tilts about an external axis distinct from and parallel to the wheel axis to actuate the button of the switch. Although this configuration means that the button-wheel only has to accommodate the vertical travel of the wheel, having a moving mounting still results in a larger overall size and probably greater complexity than that associated with a stationary mounting and moving shaft. In addition, the Shigemoto device must also accommodate some horizontal motion of the mounting that is associated with the mounting tilt. 
     No button-wheel currently exists that fulfills all the design constraints associated with devices such as PDAs and laptops, where tight spaces and uniform tactile feedback are highly desirable. Existing devices hold onto ideas that are more applicable to computer mice, contain features that increase the size of the button-wheel, or introduce more complex and costly mechanisms. The present invention addresses the deficiencies of these prior art approaches. 
     SUMMARY 
     The disclosure describes a button wheel. The button wheel comprises a support frame including a pair of parallel opposed inner surfaces. A platform is nestably mounted in the support frame. The platform includes a pair of parallel opposed outer surfaces forming a pair of linear bearings with the parallel opposed inner surfaces of the support frame to allow the platform to translate from a biased rest position in a direction parallel to the opposed inner surfaces and the opposed outer surfaces. The button wheel also includes first and second spaced apart mounts fixed to one of the support frame and said platform. The button wheel includes a shaft disposed along an axis and including a first end rotatably engaged in the first mount and a second end rotatably engaged in the second mount. A wheel is mounted on the shaft and a rotation sensor is in operative communication with the wheel. The button wheel also includes a translation sensor coupled between the support frame and the platform. 
     The disclosure also describes an alternative embodiment of the button wheel. This embodiment comprises a support frame including a flat-spring region and a first mount disposed on the flat-spring region of the support frame. The button wheel includes a second mount spaced apart from the first mount and disposed on the support frame. A translation sensor is mounted in a fixed position with respect to the fixed region of the support frame. The button wheel also includes a shaft disposed along an axis and including a wheel mounted on the shaft and a first end rotatably engaged in the first mount and a second end rotatably and translatably engaged in the second mount so as to allow the shaft to translate with respect to the support frame in a direction substantially perpendicular to the axis to actuate the translation sensor upon the application of mechanical force to the wheel having a component substantially along the direction. The button wheel has a rotation sensor in operative communication with the wheel. 
     Another button wheel embodiment is described in the disclosure. The button wheel comprises a support frame and first and second spaced apart mounting members mounted to the support frame. A shaft is disposed along an axis and including a first end rotatably engaged in the first mounting member and a second end rotatably engaged in the second mounting member. A first translation limiter is disposed on the shaft proximate to the first end and adjacent to the first mounting member to limit the translation of the shaft along the axis. A second translation limiter is disposed on the shaft proximate to the second end and adjacent to the second mounting member to limit the translation of the shaft along the axis. A wheel is mounted on the shaft and a rotation sensor is in operative communication with the wheel. The button wheel includes a translation sensor coupled between the support frame and the shaft. 
     Another embodiment is described comprising a support frame and first and second biasing members mounted on the support frame. The button wheel includes first and second spaced apart movable mounting members mechanically coupled to the support frame through the first and the second biasing members. A shaft is disposed along an axis and includes a first end rotatably engaged in the first movable mounting member and a second end rotatably engaged in the second movable mounting member. A wheel is mounted on the shaft. A rotation sensor is in operative communication with the wheel and a translation sensor is coupled between the support frame and the shaft. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Referring now to the figures, wherein like elements are numbered alike: 
     FIG. 1 is a partial cut-away view of a prior art button-wheel design for computer mice; 
     FIG. 2 is an isometric view of a prior art button-wheel design used in computer mice; 
     FIG. 3 is a partial cross-sectional view of another prior art button-wheel design that incorporates a tilting shaft to actuate a switch; 
     FIG. 4 is an isometric view of a prior art button-wheel design in which the platform tilts about an axis external to the wheel and parallel to the wheel axis to actuate a switch; 
     FIG. 5 is a cross-sectional view of an exemplary embodiment of a button-wheel that actuates a switch through translation of the platform; 
     FIG. 6 is a cross-sectional view of a button-wheel that actuates a switch through translation of the platform; 
     FIG. 7 is a cross-sectional view of an alternate embodiment for the bottom section of the exemplary embodiment depicted in FIGS. 5 and 6; 
     FIG. 8 is a cross-sectional view of an alternate embodiment for the bottom section of the exemplary embodiment depicted in FIGS. 5 and 6; 
     FIG. 9 is a cross-sectional view of an alternate embodiment for the bottom section of the exemplary embodiment depicted in FIGS. 5 and 6; 
     FIG. 10 is a cross-sectional view of an alternate embodiment for the bottom section of the exemplary embodiment depicted in FIGS. 5 and 6; 
     FIG. 11 is a cross-sectional view of an alternate embodiment for the bottom section of the exemplary embodiment depicted in FIGS. 5 and 6; 
     FIG. 12 is a cross-sectional view of an alternate embodiment for the bottom section of the exemplary embodiment depicted in FIGS. 5 and 6; 
     FIG. 13 is a cross-sectional view of a button-wheel embodiment in which the platform translates and the shaft physically contacts the switch to actuate the switch; 
     FIG. 14 is a cross-sectional view of a button-wheel embodiment in which the shaft translates independently from the platform to actuate the switch; 
     FIG. 15 is a side view that corresponds with FIG. 14; 
     FIG. 16 is a cross-sectional view of the button-wheel embodiment shown in FIG. 14 in the configuration in which the switches are depressed; 
     FIG. 17 is a side view that corresponds with FIG. 16; 
     FIG. 18 depicts an alternate embodiment for the slotted shape that forms part of the mount that constrains the motion of the wheel shaft; 
     FIG. 19 depicts an alternate embodiment for the slotted shape that forms part of the mount that constrains the motion of the wheel shaft; 
     FIG. 20 depicts an alternate embodiment for the slotted shape that forms part of the mount that constrains the motion of the wheel shaft; 
     FIG. 21 is a cross-sectional view of a button-wheel embodiment in which a movable mount supported by a coiled spring enables one end of the wheel shaft to translate independently from the other end of the shaft; 
     FIG. 22 is a side view that corresponds with FIG. 21; 
     FIG. 23 is a cross-sectional view of a button-wheel embodiment in which a movable mount is supported by a flat spring; 
     FIG. 24 is a side view that corresponds with FIG. 23; 
     FIG. 25 is a cross-sectional view of a button-wheel embodiment in which two movable mounts are supported by flat springs; 
     FIG. 26 is a cross-sectional view of a button-wheel embodiment utilizing a non-contact switch in which two movable mounts are supported by flat springs; 
     FIG. 27 is a top view of a button-wheel design in which a movable mount is supported by a cutout of the platform  3 ; 
     FIG. 28 is a cross-sectional view of the button-wheel embodiment depicted in FIG. 27; 
     FIG. 29 is a side view that corresponds with FIG. 28; 
     FIG. 30 is a cross-sectional view of the button-wheel design depicted in FIG. 27 in which the switch is depressed; 
     FIG. 31 is a side view that corresponds with FIG. 30; 
     FIG. 32 is another side view that corresponds with FIG. 28; 
     FIG. 33 is another side view that corresponds with FIG. 31; 
     FIG. 34 is a partial top-view of an alternative cutout for the flexible, biasing member supporting the movable mount shown in FIGS. 27 through 33; 
     FIG. 35 is a partial cross-sectional view that depicts a feature that can be added to the wheel shaft to reduce undesirable tilting of the shaft during switch actuation; 
     FIG. 36 is a side view that depicts an additional shaft mount that reduces undesirable tilting of the shaft during switch actuation; 
     FIG. 37 is a partial cross-sectional view that corresponds with FIG. 36; 
     FIG. 38 depicts an alternate embodiment for the additional mount depicted in FIGS. 36 and 37; 
     FIG. 39 depicts an alternate embodiment for the additional mount depicted in FIGS. 36 and 37; 
     FIG. 40 depicts an alternate embodiment for the additional mount depicted in FIGS. 36 and 37; and 
     FIG. 41 is a partial cross-sectional view of an additional support that reduces undesirable tilting of the shaft during switch actuation. 
    
    
     DETAILED DESCRIPTION 
     Those of ordinary skill in the art will realize that the following description of the present invention is illustrative only and not in any way limiting. Other embodiments of the invention will readily suggest themselves to such skilled persons. 
     FIGS. 5 through 13 outline a preferred embodiment in which biasing members interact with the platform (either by direct physical contact or through other components that support the platform) to bias the platform, shaft, and wheel and ensure substantial translation of these three components and uniform tactile feedback along the width of the wheel in response to push-type force on the wheel along the direction indicated by F. Substantial translation is translation that is substantially parallel to the direction F and having a minimal tilt or deviation from the direction F. This preferred embodiment can utilize any type of rotary encoder that is commercially available as a first sensor, or simply a rotation sensor  102  that senses the rotation of the wheel, and a second sensor, or simply a translation sensor that senses the translation of the wheel created by user push-type forces on the wheel along the direction F. Similarly, if tactile feedback in response to rotation of the wheel is desired, this preferred embodiment can utilize any type of tactile feedback mechanism similar to those found in commercially available button-wheels. One example is to employ a component that combines a mount, a rotary encoder, and a detent mechanism into one unit that reduces or limits shaft tilt. 
     Referring to FIG. 5, a cross-sectional view of an exemplary embodiment of a button-wheel  200  is illustrated. The button-wheel  200  includes a wheel  202  having a generally cylindrical shape in which the width dimension is larger than the diameter dimension. It is contemplated that variations of dimensions and shape of wheel  202  are within the scope of the disclosure. The button-wheel  200  includes a shaft  204 . The shaft  204  can be an axial extension of the wheel  202  wherein the shaft  204  has a smaller diameter than that of the wheel  202 . The shaft  204  and wheel  202  can also have the same diameter, such that the wheel  202  is simply a defined region of the shaft  204 . Wheel  202  is supportable by at least one mount or in a preferred embodiment, two mounts, a first mount  206  and a second mount  208 . The first mount  206  and the second mount  208  provide rotational and translational support for wheel  202  through shaft  204 . Any combination of mount types is contemplated as part of this disclosure. 
     The first mount  206  and second mount  208  are mounted to a platform  210 . Platform  210  can be a structure that provides a substantially rigid surface to attach the first mount  206  and the second mount  208 , as well as minimize shaft  204  binding with first mount  206  and second mount  208 , due to platform deflection relative to shaft  204 . Additionally, platform  210  can provide sufficient stiffness such that translational forces applied to wheel  202  can be transmitted from wheel  202  through shaft  204  into first mount  206  and second mount  208 , and into platform  210 . Platform  210  includes at least a first outer surface  212 . In another embodiment, platform  210  includes two opposed outer surfaces, a first outer surface  212  and a second outer surface  214 . The first outer surface  212  and second outer surface  214  are located at opposite ends of the platform  210 . The first outer surface  212  and second outer surface  214  are located substantially parallel to and on opposite sides of the platform  210 . 
     Further included with the button-wheel  200  is a support frame  216 . The support frame  216  includes multiple surfaces that enclose and support the platform  210 . The support frame  216  includes a base  218  and at least two sides, a first side  220  having a first inner surface  222  and a second side  224  having a second inner surface  226 . The sides  220  and  224  protrude from the base  218  substantially perpendicular to a planar base surface  228  formed by the base  218 . The sides  220  and  224  are affixed on opposite ends of the base  218 . The first outer surface  212  and the second outer surface  214  of the platform  210  are located within the button-wheel  200  such that the first inner surface  222  and the second inner surface  226  guide the first outer surface  212  and the second outer surface  214 . Located between the base  218  and the platform  210  is one type of translation sensor in the form of a push button switch  230 . The switch  230  includes a button  232  disposed on the switch  230 . The switch  230  includes a biasing member  234  that biases the button  232  and in some embodiments the platform  210  and associated button-wheel components and subcomponents. Also included within the button  232  is a button sensor  236 . The operational relationship of the components and subcomponents of the button-wheel  200  can be further explained below. 
     FIG. 5 depicts an embodiment of a button-wheel  200  in which the switch  230  combines the functions of sensing translation and biasing, via the button sensor  236  that senses user push-type inputs on the wheel  202  and the biasing member  234 , respectively. Switch  230 , shown in one of many embodiments as a pushbutton switch, having the button  232  and biasing member  234  that can produce spring-like reaction forces in response to translation of the platform  210  along a direction F indicated by the force direction arrow  238 . When a user of the button-wheel applies a push-type force on the wheel  202  along the direction shown by F  238 , this user force is transmitted through the shaft  204  to the first mount  206  and second mount  208 . Mounts  206  and  208  are designed to minimize the tilting of shaft  204 , and transmit the user force toward the platform  210 . Motion of platform  210  is guided by the sides  220  and  224  of the support frame  216  to translate along the direction shown by direction arrow  238 . The push-type force on wheel  202  causes platform  210  to substantially translate along the direction shown by direction arrow  238 , with minimal tilt or deviation therefrom towards the base  218  of support frame  216 . Platform  210  normally rests on or near button  232 . A downward motion of platform  210  depresses button  232  and actuates switch  230 . The button-wheel configuration shown in FIG. 5 thus biases and guides platform  210  such that translation is the primary action associated with switch actuation. Button  232  and biasing member  234  provide the tactile displacement and force feedback associated with switch actuation, and limit the total possible travel of wheel  202  by limiting the total possible travel of platform  210 . Additional features or components that function as biasing members or hard stops can be added to the button-wheel  200  shown in FIG. 5 to further refine the feel and limit of the travel associated with switch actuation. 
     The components of the current embodiment can be located and oriented in alternative configurations as shown in FIG. 6, to lower cost and complexity of the button-wheel device. For example, in an embodiment in which platform  210  is a circuit board with conductive traces  240  that facilitate the acquisition and transmission of button-wheel signals, switch  230  can be mounted on the side of platform  210  opposite from wheel  202 . The button  232  is adjacent and in contact with planar base surface  228 . When the user applies push-type force on wheel  202  along the direction shown by direction arrow  238 , platform  210  substantially translates toward support frame  216  and depresses button  232  of switch  230  against base  218  and actuates switch  230 . Such a configuration, which is shown in FIG. 6, enables the designer to place switch  230  in direct electrical communication with the conductive traces  240  through surface mount technology, via technology, through-hole technology, or other means if necessary while incurring only negligible changes in the button actuation process or feel. User rotational inputs to wheel  202  can be accomplished without creating substantial translation of platform  210 . 
     In the embodiment of the button-wheel  200  shown in FIGS. 5 and 6, the outer surfaces  212  and  214  of platform  210  and first inner surface  222  and second inner surface  226  of support frame  216  function as linear bearings. Thus, the tolerances between the first outer surface  212  and first inner surface  222  and the second outer surface  214  and second inner surface  226  are preferably tightly controlled to minimize chances of binding and sticking and to ensure uniform tactile feedback. Maintaining uniform feedback means that similar displacement and force feedback are produced regardless of where along the width of wheel  202  the user applies push-type force along the direction shown by direction arrow  238 . Those skilled in the art will note that if button  232  has a larger area of contact with platform  210 , or if outer surfaces  212  and  214  are increased in size to improve alignment precision and to facilitate the interaction between mounting  210  and support frame  216 , then the tolerances between outer surfaces  212  and  214  and inner surfaces  222  and  226  can be made greater. 
     FIGS. 7 through 13 depict alternative embodiments for the components and features of the button-wheel  200  that are located as depicted below platform  210 , including platform  210 . Components and features of the button-wheel  200  depicted above platform  210 , such as wheel  202 , remain unchanged as depicted in FIG.  5  and thus are not explicitly shown in FIGS. 7 to  13 . 
     FIG. 7 illustrates an embodiment of button-wheel  300  where platform  210  is supported by multiple switches, switch  302 , switch  304 , and switch  306 , each switch having buttons. Switch  302  having button  308 , switch  304  having button  310 , and switch  306  having button  312 . Each switch and button also has a biasing member and sensor (not shown). The biasing members can provide spring-like reaction forces in response to platform  210  translation along the direction shown by direction arrow  238 . Switches  302 ,  304 , and  306  are selected and located such that, when the user applies push-type force on wheel  202  (not shown) along the direction shown by direction arrow  238 , platform  210  substantially translates and pushes buttons  308 ,  310 , and  312  and actuate switches  302 ,  304 , and  306 . Those skilled in the art will note that, if biasing members associated with switches  302 ,  304 , and  306  provide similar force and displacement reaction in response to translation of platform  210  along the direction shown by direction arrow  238 , locating them symmetrically about the expected center of user push-type force application locations and close to inner surfaces  202  and  212  helps to ensure that platform  210  will substantially translate along the direction shown by direction arrow  238 . The location will also ensure that platform  210  will minimally deviate from the direction F (tilt), in response to push-type force along the direction shown by direction arrow  238  even when such user push-type force is applied near a portion of wheel  202  closer to switch  302 , and farther from switch  304 , or switch  306 . These multiple locations of support help ensure substantial translation also make it possible for the tolerances between outer surfaces  212  and  214  of FIG.  5  and inner surfaces  222  and  226  to be greater than required by the configurations shown in FIGS. 5 and 6. 
     In another embodiment, only one of the switches  302 ,  304 , and  306  has to be powered and connected to the button-wheel electronics (not shown) to achieve ON/OFF switch functionality. Any of the other two switches, if also powered and in electrical communication with the button-wheel electronics, can serve as a backup switch. If the other two switches are not powered and are not in electrical communication with the button-wheel electronics, then they can be dummy switches that function only as biasing members that help ensure substantial translation and provide uniform tactile feedback. 
     To help ensure substantial translation and uniform tactile feedback for the simple embodiment shown in FIG. 8, compressive biasing members  314  are shown substituted for the switches  302  and  306  mountable between the platform  210  and the base  218  on the planar base surface  228 . The biasing members  314  can produce spring-like reaction forces similar to that of the switch  304 . The biasing members  314  may consist of any component and material able to produce spring-like responses in response to push-type inputs transmitted through the platform  210 , (for example, unpowered switches, coils, snap domes, compression springs, extension springs, torsion springs, flat springs and elastomeric bumps). 
     FIG. 9 shows another embodiment including tensile biasing members  316  in which the tensile biasing members  316  are mountable to the platform  210  at ends near the first side  220  and the second side  224  of the base  218 . A switch  318  is mountable between the platform  210  and the base  218  on planar base surface  228 . In an embodiment the switch  318  is one pushbutton switch. This embodiment allows limited translation of the platform  210  in the directions indicated by G and the bi-directional arrow  320 , which may be desirable in some button-wheel designs. Those skilled in the art will note that, to ensure substantial translation of platform  210  along the direction shown by direction arrow  238  in response to user input forces along the direction shown by direction arrow  238  in the configuration shown in FIG. 9, biasing members  316  may need to be biasing members that generate spring-type reactions different from switch  318  in response to the same input force vector. 
     FIG. 10 shows another embodiment that utilizes a breakbeam sensor  322  for second sensor  104 . The breakbeam sensor  322  is a second sensor variation that utilizes an alternate technology that does not also function as a biasing member. The breakbeam sensor  322 , which is an optical beam-breaking type sensor formed from a photo-emitter  324  and photo-detector  326  fixed to the base  218 , is non-contact and does not provide any spring-type reaction forces. During operation of the breakbeam sensor  322 , emitter  324  transmits photons that are sensed by detector  326 , and they function together to determine the presence or non-presence of a blocking piece  328  extending from platform  210 . Blocking piece  328  can be designed such that the length that extends beyond the platform  210  is short enough to allow detector  326  to detect photons emitted by emitter  324  when the platform  210  is in a normally non-translated position. When the user pushes with a force along the direction shown by direction arrow  238 , the movement of platform  210  causes blocking piece  328  to interpose between detector  326  and emitter  324 ; this prevents detector  326  from sensing the photons from emitter  324 , and results in a change in the state of the detector signals that indicates switch actuation. Two biasing members  330  and  332  which support platform  210  are preferably similar in spring response and placed in a geometrically symmetrical manner to help ensure substantial translation of platform  210  and uniform tactile and displacement feedback in response to user push-inputs on wheel  202  along the direction shown by direction arrow  238 . 
     It is also within the scope of this disclosure to design blocking piece  328  to normally obstruct emitter  324  and detector  326 , and move into a non-blocking state with sufficient user input force along the direction shown by direction arrow  238 . This latter approach may be best accomplished by incorporating a passage  334  or cutout in blocking piece  328 . The passage  334  or cutout can be placed close to platform  210  such that blocking piece  328  obstructs communication between photo emitter  324  and photo detector  326  when there is no translation of the platform  210  along the direction shown by direction arrow  238 . Then, with sufficient user input force along the direction shown by direction arrow  238 , the substantial translation of platform  210  brings the passage  334  into place between emitter  324  and detector  326  such that blocking piece  328  no longer prevents detector  326  from sensing the photons of emitter  324 . Those skilled in the art will also note that a passage or cutout in blocking piece  328  can also be used in the embodiment where blocking piece  328  normally does not obstruct emitter  324  and detector  326 . In this embodiment, the passage  334  can be located such that the photo emitter  324  and detector  326  can optically communicate when there is no translation of the platform  210  along the direction shown by direction arrow  238 . Sufficient user input force along the direction shown by direction arrow  238  translates platform  210  and removes passage  334  from alignment between emitter  324  and detector  326  such that optical communication is broken between emitter  324  and detector  326 . The translated platform  210  places the passage  334  into a position such that blocking piece  328  prevents detector  326  from sensing the signals of emitter  324 . User rotational inputs to wheel  202  can be accomplished without creating substantial translation of platform  210 . 
     Although the embodiment depicted in FIG. 10 explicitly calls out a beam-breaking type sensor as the alternative switching technology used, other switching technologies can also be incorporated into the button-wheel  300 . For example, FIG. 11 illustrates a proximity sensor  336  utilized as a translation sensor for another embodiment of the button-wheel  300 . The proximity sensor  336  can include a first sensor member  338  and a second sensor member  340 . The first sensor member  338  can be fixed to platform  210  and located opposite from second sensor member  340 , which is fixed to planar base surface  228  of base  218 . The proximity sensor  336  senses the movement of platform  210  relative to base  218 , in response to user push-type inputs on wheel  202  (not shown) along the direction shown by direction arrow  238 . A thresholding algorithm can be used in conjunction with the outputs of the proximity sensor  336  to generate appropriate switching signals. 
     FIG. 12 shows strain gauges  342 ,  344 , and  346  as another potential technology for another embodiment of the second sensor. FIG. 12 shows an embodiment in which three second sensors are formed by strain gauges  342 ,  344 , and  346 . The strain gauge  342  is disposed on biasing member  348  that is mounted to base  218 . The strain gauge  344  is disposed on biasing member  350  that is mounted to base  218 . The strain gauge  346  is disposed on biasing member  352  that is mounted to base  218 . The biasing members  348 ,  350  and  352  can, for example, be flat springs that deform and deflect in reaction to forces from platform  210 . Biasing members  348 ,  350  and  352  extend from base  218  and support platform  210 . These biasing members  348 ,  350  and  352  are preferably designed and located to help ensure substantial translation of platform  210  in response to user push-type inputs on wheel  202  (not shown) along the direction shown by direction arrow  238 . When push-type inputs are applied, platform  210  compresses biasing members  348 ,  350 , and  352  such that strain gauges  342 ,  344 , and  346  change in resistance. This change in resistance can be sensed and used to provide the signals associated with switch actuation of the button-wheel  300 . In an alternate embodiment, strain gauges  342 ,  344 , and  346  are embedded within biasing members  346 ,  350 , and  352 , respectively. In an alternate embodiment, only one or two of the strain gauges  342 ,  344 , and  346  and associated biasing member  348 ,  350 , and  352  respectively are used by button-wheel  300 . In an alternate embodiment, additional biasing members comprise button-wheel  300 . Although FIGS. 10,  11  and  12  depict only three potential alternatives to conventional switches that can be used for the second sensor, those skilled in the art will note that many other alternative technologies, such as load cells, are viable and are contemplated as part of this disclosure. 
     FIG. 13 is a cross-sectional view that depicts another embodiment of button-wheel  400  in which an aperture  402  in platform  210  enables a switch  404  to interact with shaft  204  instead of platform  210 . In embodiments when switch  404  utilizes a technology that can provide spring-like response to push-type inputs applied by the user along the direction shown by direction arrow  238 , then switch  404  may be a biasing member that interacts with shaft  204  that can be taken into account when selecting biasing members for button-wheel  400 . The required height of the button-wheel  400  is reduced, since the dimension of gap  406  between the platform  210  and base  218  now has to accommodate only the maximally compressed biasing members  408  and  410 , and not a maximally compressed switch  404 . Since biasing members  408  and  410  do not require the electronics associated with switches and do not have to adopt the tubular compression/extension spring configuration as shown in FIG. 13, it is possible to include biasing members that occupy smaller dimensions than maximally compressed switches. Similar to the alternative biasing member and second sensor embodiments shown in FIGS. 8 to  13 , although FIG. 13 shows one standard pushbutton switch  404  and the biasing members  408  and  410  as two standard extension/compression springs attached between platform  210  and base  218 , alternative sensors and biasing member types and biasing member locations are possible. 
     The total possible translation in the direction shown by direction arrow  238  for wheel  202  as shown in the embodiments of FIGS. 5 through 13 can be defined by the maximum button depression of the associated switches and the maximum compression of the associated springs, or hard stops formed by other associated button-wheel features (such as blocking piece  328 ). It is also contemplated that additional features or components can be included to further define the maximum translation possible for wheel  202 . 
     It is also within the scope of this preferred embodiment to utilize second sensors capable of indicating multiple levels (extent) of user push-type inputs. For example, the various pushbutton switches shown in FIGS. 5 through 9 can be pushbutton switches with at least two positions of switch actuation such that they can indicate at least three levels of compression, and thus at least three levels of translation of platform  210 . The additional information relating to the level of translation of platform  210  may be useful in some input devices by enabling one level of translation and associated position of switch actuation to trigger one action while additional levels of translation and associated positions of switch actuation trigger alternative actions. 
     Multiple levels of translation can also be provided by many of the alternative technologies possible for the second sensor. For example, for the breakbeam sensor  322  shown in FIG. 10, blocking piece  328  can be designed such that a pattern of passages instead of a single passage is present in blocking piece  328  such that different levels of platform  210  translation results in different levels of light blockage from emitter  324  to detector  326 . For the proximity sensor  336  shown in FIG. 11, standard proximity sensor technology, such as capacitive or hall effect sensors, produce an analog signal dependent on the separation between the first sensor member  338  and the second sensor member  340  and can sense a continuum of separation between the first sensor member  338  and the second sensor member  340 . The strain gauges  342 ,  344 , and  346  shown in FIG. 12 can also sense a continuum of deflection of the associated biasing members. These signals from the proximity sensor and the strain gauges can be used to estimate the displacement of platform  210  from some reference and the level of translation of platform  210 ; the resulting estimate of displacement or translation and can even be differentiated over time to estimate the velocity and acceleration of platform  210 . 
     The configuration of second sensors and biasing members shown in FIGS. 7 through 13 are preferably designed to ensure substantial translation of platform  210  in response to user push-type force along the direction shown by direction arrow  238  on wheel  202  regardless of the exact location of user push inputs on wheel  202 . In most cases of substantial translation, some limited tilting (deviation from the direction shown by direction arrow  238 ) of platform  210  may still occur even though translation is still the primary action associated with switch actuation. In the case that a set of second sensors is used, and the second sensors have very high sensitivity to the motion of platform  210 , then this limited tilting may be utilized to provide greater user control of the host device through the button-wheel ( 200 ,  300 ,  400 ). 
     For example, for the embodiment shown in FIG. 12, if the strain gauges  342 ,  344  and  346  are well characterized and the spring constants of the biasing members  348 ,  350  and  352  are known, then the signals from the strain gauges can be used to calculate the reaction forces provided by the different biasing members. If it is possible to further assume that the user force along the direction shown by direction arrow  238  dominates, and if the biasing members containing second sensors define a complete statically determinant situation associated with platform  210 , then force equilibrium considerations are sufficient for estimating the location of user force input and user force magnitude. Alternatively, if the biasing members containing second sensors define a complete statically indeterminate situation, then additional geometric and material considerations may be necessary to estimate the location of user force input and user force magnitude. 
     However, since this estimate of user force input location is more accurate when the biasing members deflect in different ways, when platform  210  tilts to some limited extent, and when platform  210  only applies forces that can be neglected in the above calculations on components of the button-wheel other than the biasing members that contain second sensors, careful selection and placement of button-wheel components is required to ensure substantial translation of platform  210  and wheel  202  in response to user push-type inputs on wheel  202  along the direction shown by direction arrow  238 , and to ensure that the magnitude of tilting is acceptable. Button-wheels that can estimate the effective magnitude and application point of the user input force enable finer user control, and are useful in some applications. Example applications include, and are not limited to, menu selection, horizontal or vertical scrolling, and game control. 
     The approach used with the strain gauges to estimate user force location can also be used when other switching technologies that can sense a continuum of translation levels are used. For example, load cells are ready alternatives. However, some second sensor technologies are not sufficiently sensitive to the motion of platform  210  and may require tilting of platform  210  of such a magnitude that substantial translation of platform  210  no longer occurs during switch actuation. Significant tilting is undesirable, and the use of second sensor technologies that require significant tilting of wheel  202  and platform  210  in estimating user input force locations are preferably avoided. One method of overcoming this limitation is to utilize second sensors of different technologies in the same button-wheel device; a type of second sensor can be used to generate switch actuation signals (which may be involve multiple levels of translation and positions of switch actuation) while another type of second sensor can be used to calculate reaction forces and estimate the location of user push inputs on wheel  202 . 
     Although FIGS. 5 and 6 depict button-wheel embodiments that use only one switch that combines a second sensor with a biasing member and FIGS. 7 through 13 depict embodiments that use a total of three components that function as biasing members and/or second sensors, many other alternative configurations with different numbers and arrangements of the second sensors and biasing members are viable in ensuring substantial translation of platform  210  in response to user push-type inputs on wheel  202  along the direction shown by direction arrow  238 , and in promoting a uniform tactile and displacement response to said user inputs. The actual number and placement of the second sensors and biasing members depend on whether or not combination second sensors and biasing members are used, and the size, shape, and material of platform  210 . For example, if the region of platform  210  that supports the button-wheel  200 ,  300 ,  400  has a relatively rectilinear shape, then a total of four biasing members placed near the corners of this region may be preferred; if none of the biasing members are part of a component that also functions as a second sensor, then some type of second sensor that produces reaction forces that are negligible when compared to the biasing members may be placed anywhere on platform  210  where it is possible to properly sense user push-type inputs. It is also possible to utilize greater numbers of biasing members to complement a rectilinear region of platform  210 . For example, five biasing members can be distributed with one at the center of the rectilinear region and the other four at the corners. 
     Additional biasing members incur extra cost, and are useful only when the relatively square region is sufficiently large to require the extra support points to reduce undesirable tilting of the shaft and ensure substantial translation during switch actuation. In the case that the region of platform  210  that supports the button-wheel  200 ,  300 , or  400  is elongated and is more oblong in shape, only a total of two biasing members may be necessary. For this more oblong shape, one biasing member can be located underneath the shaft on one side of the wheel while the other can be located underneath the shaft on the other side of the wheel. Similar to the rectilinear case described above, if none of the biasing members are part of components that also function as second sensors, then some type of second sensor that produces reaction forces that are negligible when compared to the biasing members may be placed anywhere on platform  210  where it is possible to properly sense user push-type inputs. 
     The button-wheel components can be located and oriented in alternative configurations to lower the cost and complexity of the final device. For example, if platform  210  is a circuit board with conductive traces to facilitate the acquisition and transmission of button-wheel signals, then the switch (or switches) of the button-wheel can be mounted on the side of platform  210  opposite from wheel  202  and placed in direct electrical communication with the circuit board traces (through standard surface mount technology, via technology, through-hole technology, or other means if necessary). With this configuration, when the user applies push-type force on wheel  202  along the direction shown by direction arrow  238 , platform  210  substantially translates toward support frame  216  and depresses the button(s) of the switch(es) against the support frame  216  and switch actuation occurs. The resulting switch actuation will be almost identical from the user&#39;s perspective to the embodiment where the switch(es) is(are) mounted on support frame  216 . 
     Additional variations of this embodiment are viable and still retain equivalence to the invention described within this document. Such variations include, but are not limited to, the following. The exact component technologies and types can change; for example, the wheel encoder can be optical or mechanical. The component sizes and shapes can also vary; for example, the wheel can be disc-like, cylindrical, spherical, have circular cross-section, have polygonal cross section, or have variable cross-sectional shape across the width of the wheel; or, the shaft may also vary in cross-section, and contain stepped or rounded features as necessary to achieve its functions and to simplify button-wheel construction. 
     Other button-wheel embodiment may also utilize components that perform the function of many parts of the button-wheel; examples of components that can easily combined into contiguous units include, but are not limited to: at least part of a first mount and at least part of a mount supporting wheel shaft  204 , at least part of wheel  202  and at least part of any rotary tactile feedback mechanisms, and at least part of wheel  202  and at least part of wheel shaft  204 . In fact, wheel  202  can be as simple as an elastomeric material covering directly molded onto wheel shaft  204 , or a region of wheel shaft  204  can be denoted wheel  202  such that wheel  202  is integral to wheel shaft  204 . The button-wheel may also utilize parts fashioned from many distinct components; for example, a first sensor can comprise of a breakbeam sensor formed from a photoemitter, an encoder disc that rotates in response to rotation of wheel  202 , and a photodetector. 
     The embodiments can also utilize component mounting methods and mounting locations different from those described in FIGS. 5 through 13; for example, the biasing members and second sensors (translation sensors) can be mounted on platform  210  or support frame  216  and can be oriented in a variety of ways as long as they still ensure substantial translation of platform  210  along the direction shown by direction arrow  238 , properly sense translation of platform  210  along the direction shown by direction arrow  238 , and provide uniform tactile force and displacement feedback parallel to the direction shown by direction arrow  238  in response to push-type forces on wheel  202  along the direction shown by direction arrow  238 . 
     FIGS. 14 through 17 and  21  through  34  depict another embodiment in which members support the shaft, in preferred embodiments biasing members bias the wheel shaft (either by direct physical contact or through bearings and other components that support the wheel shaft) to ensure substantial translation of the wheel shaft and wheel and uniform tactile feedback along the width of the wheel in response-to push-type force on the wheel along the direction shown by direction arrow  238 . In some embodiments, at least one mount that supports the shaft is composed of more than one distinct component or element, such as a slotted shape functioning in conjunction with a biasing member. As shown in FIG. 14 (an embodiment of button-wheel  500 ), the shaft  204  has a first end  502  that can translate independently from a second end  504  located opposite thereof. The first end  502  can move with a vector component along the direction shown by direction arrow  238  while second end  504  does not move or moves with a vector component opposite the direction shown by direction arrow  238 . However, shaft  204  is carefully biased toward the user by biasing members such that ends  502  and  504  largely translate together along the direction shown by direction arrow  238 . Thus, when the user applies push-type force on wheel  202 , wheel shaft  204  substantially translates independently from platform  210  and actuates at least one second sensor. To ensure substantial translation of shaft  204  along the direction shown by direction arrow  238  and improve the uniformity of tactile force and displacement feedback in response to push-type inputs along the direction shown by direction arrow  238 , additional features and components may be used to further guide and constrain shaft  204 . 
     FIGS. 14 through 17 illustrate embodiments in which shaft  204  is supported by two switches  506  and  508  that function as both biasing members and second sensors (translation sensors). Switches  506  and  508  are shown as pushbutton switches in FIGS. 14 through 17, but they can be of any type of translation sensor that can also provide spring-like reaction force in response to translation of shaft  204  along the direction shown by direction arrow  238 . FIG. 14 is a cross-sectional view depicting the situation in which switches  506  and  508  are not actuated, and FIG. 15 is the corresponding side view. FIG. 16 is a cross-sectional view depicting the situation in which the switches  506  and  508  are actuated, and FIG. 17 is the corresponding side view. FIGS. 14 through 17 do not explicitly show the first sensor that senses rotation of wheel  202  or, if included, the tactile feedback mechanism that provides tactile feedback in response to rotation of wheel  202 . Any first sensors or rotational tactile feedback mechanisms can be located anywhere within the button wheel  500  as long as they do not interfere with the rotation or substantial translation of the button wheel  500 , and properly sense rotation or provide feedback. These parts of the button-wheel can also utilize any of the designs disclosed in commercially available devices. 
     The two switches  506  and  508  are selected and located to bias wheel shaft  204  such that substantial translation of wheel shaft  204  results in response to push-type force on wheel  202  along the direction shown by direction arrow  238 . Two mounting members  510  and  512 , which are components with slot cutouts and are mountable to platform  210 , interact with and constrain shaft  204 . Two shaft collars (translation limiters)  514  and  516  interact with mounting members  510  and  512  to limit the amount of movement of shaft  204  along the directions indicated by the bi-directional arrow G  320 . In the embodiment shown in FIGS. 14 through 17, the mounting members  510  and  512 , shaft collars  514  and  516 , and switches  506  and  508  are preferably very similar in shape and spring response along the direction shown by direction arrow  238 ; by making the members of a component type similar to others within the component type means that a simple, symmetric distribution of these components about wheel  202  is a viable design for ensuring substantial translation and uniform tactile feedback along the direction shown by direction arrow  238 . If necessary, shaft collars  514  and  516  can also be increased in diameter such that they also function as tilt-limiting features that help reduce shaft tilt and ensure substantial translation of shaft  204 . Shaft collars  514  and  516  can be separate components attached to the shaft: shaft collars  514  and  516  can also be features manufactured onto the shaft, such as steps or grooves cut into the shaft of materials molded onto the shaft. 
     With the configuration shown in FIGS. 14 to  17 , when the user applies push-type force on the wheel  202  along direction F 238 , this force is transmitted through to shaft  204  and the buttons  518  and  520  of switches  506  and  508 . In response, shaft  204 , being guided by the spring-like reaction force of buttons  518  and  520 , mounting members  510  and  512 , and shaft collars  514  and  516 , substantially translates toward and depresses buttons  518  and  520  to actuate switches  506  and  508 . 
     Platform  210  can be any relatively rigid part that properly supports the button-wheel components. However, if platform  210  is constructed as a circuit board with conductive traces, then the sensors of the button-wheel  500  can be directly powered and their signals routed by platform  210 ; this eliminates the need for additional routing components. Those skilled in the art will also note that different designs of the components shown in FIGS. 14 through 17 are also within the scope of this embodiment. For example, shaft  204  can contain additional features such as collars and extensions to facilitate switch actuation and to limit the travel of wheel  202  or shaft  204  along the direction shown by direction arrow G  320 . The shaft can also replace shaft collars  514  and  516  with additional features such as grooves or steps to reduce cost or simplify manufacture. Alternate slot patterns in mounting members  510  and  512  are also possible, and some potential slot designs are shown in FIGS. 18 through 20; FIG. 18 shows an open, straight slot  522  that may facilitate assembly, FIG. 19 shows a closed slot that better retains shaft  204 , and FIG. 20 shows a partially open, straight slot with small extensions near the opening to help retain shaft  204  (not shown). 
     Similar to other embodiments, this embodiment also only needs one second sensor (translation sensor) to be powered and connected to the button-wheel electronics for ON/OFF switch actuation. This means that either switch  506  or switch  508  can be replaced by a simple biasing member that provides the proper spring-type reaction force in response to user push-type input along the direction shown by direction arrow  238 . For example, FIGS. 21 through 24 disclose embodiments of a button-wheel  700  that replaces switch  508  and mounting member  512  with a movable mount  702  mountable on a biasing member  704 . 
     FIG. 21 is a cross-sectional view of an embodiment that uses a standard extension/compression spring as a biasing member  704  mountable to the platform  210  to support movable mount  702 , and FIG. 22 is the corresponding side view. The use of a standard extension/compression spring means that movable mount  702  also has limited mobility in directions that are not along the direction shown by direction arrow  238 ; this mobility in directions that are not along the direction shown by direction arrow  238  may lead to undesirable motions of shaft  204 . However, proper design of biasing member  704  and other components that interact with shaft  204  can constrain this motion in directions that are not along the direction shown by direction arrow  238  to limit this motion to acceptable magnitudes and ensure substantial translation of shaft  204  along the direction shown by direction arrow  238  in response to push-type force on wheel  202  along the direction shown by direction arrow  238 . If necessary, additional features (not shown) and components such as linear guides for the shaft  204  or tilt-minimizing features as discussed later within this document, can also be incorporated into the button-wheel  700  to guide the translation of shaft  204  along the direction shown by direction arrow  238 . FIG. 23 is a cross-sectional view of another embodiment that uses a flat spring for the biasing member  704  mountable to the platform  210  to support movable mount  702 , and FIG. 24 is the corresponding side view. Depending on the construction of the button-wheel  700 , it may be easier and less costly to use flat springs instead of standard extension/compression springs; in addition, flat springs are usually more easily designed to reduce motion of shaft  204  in directions that are not along the direction shown by direction arrow  238 . 
     Movable mount  702  can be a component that functions as a bearing, a first sensor, and a rotary tactile feedback mechanism. However, movable mount  702  would preferably be designed to not allow shaft  204  to tilt to help ensure substantial translation of shaft  204 . 
     FIG. 25 depicts a variation of another embodiment of button-wheel  800  in which both ends of shaft  204  are supported by movable mounts  802  and  804  mountable on biasing member  806  and  808  and a switch  810 . The biasing members  806  and  808  and switch  810  are mountable to platform  210 . The switch  810  in the embodiment shown in FIG. 25 combines the function of a second sensor and a biasing member placed under wheel  202 . The biasing members  806  and  808  can be flat springs designed to bias and constrain shaft  204  to substantially translate along the direction shown by direction arrow  238  in response to push-type force on wheel  202  along the direction shown by direction arrow  238 . When the user applies push-type force on wheel  202  along the direction shown by direction arrow  238 , shaft  204  substantially translates along the direction shown by direction arrow  238  and movable mounts  802  and  804  compresses biasing members  806  and  808 . With sufficient translation of shaft  204 , wheel  202  contacts and depresses button  812  of switch  810  and actuates switch  810 . Although FIG. 25 discloses a standard pushbutton switch as a second sensor (translation sensor), alternative second sensor technologies are also viable and are within the scope of this invention. 
     FIG. 26 shows a variation of the embodiment depicted in FIG. 25 in which shaft  204  has been elongated and the translation sensor or simply sensor  814  has been moved away from under wheel  202  to the side of mount  804  distal from wheel  202  and proximate to an end  816  of shaft  204 . In addition, the sensor  814  can be a non-contact breakbeam-type sensor formed from photoemitter  818 , photodetector  820  mountable to platform  210 , and an extension  822  of shaft  204  proximate to end  816 . This variation shown in FIG. 26 can accommodate a larger wheel  202  or a lower overall button-wheel height by enabling the designer to include a gap  824  under wheel  202  (neither a larger wheel nor a shorter button-wheel height is shown in FIG.  26 ). Since the sensor  814  does not apply forces on shaft  204  in response to push-type force on wheel  202  along the direction shown by direction arrow  238 , biasing members  806  and  808  are designed to have similar spring response along the direction shown by direction arrow  238  and are arranged symmetrically about wheel  202  to help ensure substantial translation and uniform tactile feedback in response to push-type force along the direction shown by direction arrow  238 . However, those skilled in the art will recognize that a switch with spring-like response can also be used and can interact with shaft  204  if its spring reaction forces are negligible compared to that of biasing members  806  and  808 , or if its forces are taken into account while designing and locating biasing members  806  and  808 . Alternative translation sensor technologies besides the breakbeam-type sensor can also be used and are within the scope of this invention. Some example second sensor technologies are described earlier for other embodiments. 
     The use of biasing members  806  and  808  in the embodiment shown in FIGS. 25 and 26 means that movable mounts  802  and  804  have some limited mobility in the non-F directions. However, proper design of the biasing members  806  and  808  while keeping in mind functional characteristics such as size and spring constant, can limit this non-F motion to acceptable magnitudes. The interaction of shaft  204  with movable mounts  802  and  804  will also limit non-F motion. Additional features and components (not shown) such as linear guides for the shaft or tilt-minimizing features as discussed later within this document, can be incorporated into the button-wheel  800  to guide the translation of shaft  204  along the direction shown by direction arrow  238 . 
     FIGS. 27 through 34 depict another embodiment of button-wheel  900  in which platform  210  is a relatively rigid circuit board with a fixed region  901 . The circuit board includes a cutout  902  that creates a biasing member  904  formed by a flexible region (flat-spring region)  906  rimmed by the cutout  902 . Movable mount  908  is supportable by flexible region  906 . FIG. 27 is a top view of this embodiment. FIG. 28 is a cross sectional view of the embodiment in a state in which switch  910  is not actuated and FIGS. 29 and 32 are corresponding side views. FIG. 30 is a cross sectional view of the embodiment in a state in which switch  910  is actuated and FIGS. 31 and 33 are corresponding side views. The embodiment disclosed in FIGS. 27 through 34 has the advantage of utilizing platform  210  for multiple functions—platform  210  provides mechanical support to the button-wheel components, electrical support to the button-wheel components, and a spring bias to movable mount  908 . 
     When the user applies push-type force on wheel  202  along the direction shown by direction arrow  238 , shaft  204  substantially translates along the direction shown by direction arrow  238  as biasing member  904  deflects and shaft  204  depresses button  912  of switch  910  and actuates switch  910 . Shaft  204  has a first end  914  which can actually translate in a direction parallel to the direction shown by direction arrow  238  independently from a second end  916  wherein the second end  916  is located opposite the first end  914  of the shaft  204 . A mounting member  918 , switch  910 , and biasing member  904  can be configured to ensure that shaft  204  substantially translates along the direction shown by direction arrow  238  and provides uniform tactile feedback parallel to the direction shown by direction arrow  238  in response to push-type force on wheel  202  along the direction shown by direction arrow  238 . Cutout  902  also includes a void  920  formed in platform  210 , through which wheel  202  can move unabated; this allows the designer to include a larger wheel  202  or reduce the total height of the button-wheel  900 . 
     The embodiment depicted in FIGS. 27 through 34 requires careful biasing of biasing member  904 ; in addition, the embodiment uses biasing member  904  to facilitate the translation of movable mount  908  and switch  910  actuates through physical contact of button  912  with shaft  204 , not biasing member  904 . 
     Specific selection of the geometry of biasing member  904  and the material of platform  210  is necessary to achieve proper biasing and substantial translation of shaft  204  along the direction shown by direction arrow  238  in response to push-type force on wheel  202  along the direction shown by direction arrow  238 . The substantially planar and rectilinear shape of biasing member  904  shown in FIGS. 27 through 33 is chosen to minimize manufacturing costs and the amount of tilt and motion in directions that are not along the direction shown by direction arrow  238  in shaft  204  in response to push-type force along the direction shown by direction arrow  238 . Flexible region  906  includes a mount support region located proximate to the movable mount  908  and a cantilever base region  924  located distal from the movable mount  908  (See FIGS.  27  and  33 ). The cantilever base region  924  of flexible region  906  undergoes the greatest deformation while the mount support region  922  of flexible region  906  undergoes the greatest motion relative to the platform  210 . As shown in FIG. 33, the deflection of the biasing member  904  causes movable mount  908  to reorient in a manner that matches the rotational freedom of shaft  204 ; thus, shaft  204  can accommodate this change in orientation while experiencing negligible torsion simply by rotation in the direction indicated by direction arrow  1   926 . Some translation of shaft  204  in the direction indicated by direction arrow H  928  will also occur. However, translation along direction H  928  is the least negative of the three translational directions in 3D space on ensuring substantial translation of shaft  204 , and, with the small distance typically traveled by shaft  204 , this translation along direction H  928  is negligible. 
     Those skilled in the art will recognize that alternate geometries for biasing member  904  may be preferable to accommodate different space constraints, to accommodate manufacturing concerns, or to produce even purer translation of shaft  204  along the direction shown by direction arrow  238 . For example, elongating biasing member  904  enables movable mount  908  to approach a pure translational motion along the direction shown by direction arrow  238 . Alternatively, a biasing member  904  formed from the flexible region  906  having geometry such the spiral pattern shown in FIG. 34 enables movable mount  908  to approach a pure translation along the direction shown by direction arrow  238 . However, these alternatives usually require more space than the pattern shown in FIG. 27, and might not offer noticeable improvement in button-wheel performance above what is already achieved with the biasing member  904  shown in FIGS. 27 through 33. 
     Those skilled in the art will also note that biasing member  904  is not limited in material or in manufacture as a part of platform  210 . Biasing member  904  can be formed from other parts of the button-wheel  900  and the button-wheel host input device (not shown) as long as the biasing member  904  provides the necessary spring-like response to push-type force on wheel  202  along the direction shown by direction arrow  238 . For example, biasing member  904  can be formed as a separate component from standard spring metals such as steel or copper and incorporated into the button-wheel  900 . Biasing member  904  can also be an extension or cutout of platform  210 , an extension or cutout of a mounting bracket (not shown) for the button-wheel, or an extension or cutout of the support frame  216  manufactured from plastic, metal, composite, or other material capable of providing spring-like response. It is also contemplated that biasing member  904  can comprise of additional stiffening features or components that stiffen a highly flexible component or highly flexible region of a component that is too flexible to provide the necessary biasing force. The highly flexible component or region of a component can comprise of a flexible printed circuit or a flexible membrane with conductive traces on its surface. The additional stiffening features and additional members can comprise of extensions from a mounting bracket, extensions from the support frame  216 , or separate stiffeners that have been attached to the button-wheel specifically to stiffen the highly flexible component or highly flexible region of a component. 
     Although FIGS. 14 through 17 depict only two pushbuttons as second sensors and FIGS. 21 through 34 depict only one pushbutton as a second sensor, other numbers, types, and configurations of second sensors can also be used. These alternatives can act as backup sensors, help ensure substantial translation of shaft  204 , produce more uniform tactile feedback, or provide additional information on the translation of shaft  204 . For the embodiments shown in FIGS. 25 through 34, a simple way to add second sensors to the button wheel  800 ,  900  is to include strain gauges that produce signals in response to the deformation of biasing members  806 ,  808 , or  904 . Additional examples of alternative second sensor technologies are also disclosed in the above descriptions of embodiments. 
     Similar to the earlier discussed embodiments, this embodiment can also utilize second sensors and methods that enable the button-wheel to sense multiple levels of translation (extent of translation) and estimate the magnitude and location of the push-type force on wheel  202  along the direction shown by direction arrow  238 . In addition, the components of the earlier embodiments can also be mounted in different locations, on alternate surfaces, and in different orientations to accommodate different design constraints; the designer must only ensure these changes do not alter the functionality of the button-wheel  800 ,  900 . Different designs of shaft  204  are also viable, and shaft  204  can contain additional features such as collars and extensions to facilitate switch actuation and to limit the travel of shaft  204  along the direction shown by the direction arrow G  320 . Alternate mounting member designs are also viable, and FIGS. 18 through 20 depict some alternatives. 
     In this embodiment, shaft  204  will usually tilt to some extent; however, in most applications, a moderate amount of tilt is acceptable since the resulting motion is still substantially translational. FIGS. 35 through 41 disclose some methods to produce a smoother and more uniform translational motion for shaft  204  by reducing the undesirable tilt of shaft  204 . FIG. 35 shows a partial cross-section of an embodiment of button-wheel  1000  having a tilt reducer mechanism composed of a stop member  1002  with a cylindrical shape mountable on shaft  204 . Stop  1002  interacts with movable mount  1004 . Rotational motion of wheel  202  about its axis is impeded minimally by the interaction between stop member  1002  and movable mount  1004 . However, forces and moments which may lead to shaft  204  tilt causes stop member  1002  to contact movable mount  1004 ; these tilting forces are then absorbed by movable mount  1004  and transmitted to a base  1006  (which may be platform  210  or flexible region  906  in other embodiments) on which movable mount  1004  is mountable. Shaft  204  tilts only as much as allowed by stop member  1002 , movable mount  1004 , and base  1006 . Stop member  1002  can also be made at least a part of a rotational feedback detent mechanism or a first sensor encoder mechanism to simplify assembly, reduce costs, or reduce component count. 
     FIGS. 36 and 37 show an embodiment of a button-wheel  1100  in which a tilt reducer mechanism comprises of an additional mount  1102  working in conjunction with movable mount  1104  to reduce the undesirable tilting of shaft  204  during switch actuation. Additional mount  1102  is mountable to base  1106 . Additional mount  1102  limits the travel of second end  1108  of shaft  204  relative to movable mount  1104 , parallel to the direction shown by direction arrow  238 , and helps keep shaft  204  in line with cutout  1110  formed in additional mount  1102  and movable mount  1104 . Additional mount  1102  can contain any cutout shape that limits the travel of shaft  204  relative to movable mount  1104  parallel to the direction shown by direction arrow  238 . Some examples in addition to the circular cutout shown in FIGS. 36 and 37 are depicted in FIGS. 38 to  40 . FIG. 38 shows a horizontal cutout  1112  formed in additional mount  1102 , FIG. 39 shows a slanted cutout  1114  formed in additional mount  1102 , and FIG. 40 shows an L-shape cutout  1116  formed in additional mount  1102 . These alternatives may make button-wheel assembly easier than a pure circular cutout. The actual cutout shape will be determined by the geometry of the button-wheel. 
     FIG. 41 is a partial cross-sectional view of an embodiment having a tilt reducer mechanism comprising a hard stop  1118  (hard stop  1118  is not labeled in FIG. 41) mountable to the base  1106  under shaft  204 . The hard stop  1118  can be used in conjunction with movable mount  1104  to minimize the undesirable tilting of shaft  204  during switch actuation. Rotational motion of wheel  202  about its axis is impeded minimally by the interaction between shaft  204  and hard stop  1118 . However, forces and moments which may lead to shaft  204  tilt causes shaft  204  to impact hard stop  1118  and transmit these forces and moments into base  1106 . This limits the motion of shaft  204  relative to movable mount  1104  and thus the tilting of shaft  204 . 
     The additional features and components disclosed in FIGS. 35 through 41 can also be made at least a part of a rotational feedback detent mechanism or a first sensor encoder mechanism to simplify assembly, reduce costs, or reduce component count. 
     Those skilled in the art will note that even if the button-wheel design of the embodiments disclosed utilizes no tilt-limiting techniques, the substantially translational action is still a significant improvement on the substantially tilting action of prior art button-wheel devices. 
     For both the embodiments disclosed, those skilled in the art will note that many additional variations on these two preferred button-wheel embodiments are viable and still retain equivalence. Such variations include, but are not limited to, the following. The exact component technologies and types can change; for example, the wheel encoder can be optical or mechanical. The component sizes and shapes can also vary. For example, the wheel can be disc-like, cylindrical, spherical, have circular cross-section, have polygonal cross section, or have variable cross-sectional shape across the width of the wheel; the shaft may also vary in cross-section, and contain any stepped or rounded features as necessary to achieve its functions or to simplify button-wheel manufacture. The component mounting methods and mounting locations can differ. For example, the mounting member can be mountable on the bottom, top, or sides of the support frame, on ribs or extensions of the support frame, or on the circuit board supporting the button, encoder, and other electronics. The button-wheel may also utilize combination parts that perform the function of many components. For example, the mount and encoder can be combined into one part, the detent mechanism and the wheel can be combined into one part, or the wheel can be molded onto the shaft or a region of the shaft can function as the wheel. The button-wheel may also utilize components fashioned from many sub-parts. For example, the encoder can consist of a photoemitter, an encoder disc, and a photodetector and utilize breakbeam-type technology. 
     While the invention has been described with reference to an exemplary embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.