Abstract:
A key unit of a keyboard apparatus having at least one bumper extending from the key unit for cushioning the impact of the key unit against the enclosure of the keyboard apparatus when the key unit assumes a depressed position and/or when the key unit resumes a non-depressed position, thereby eliminating or reducing the feedback noise, while retaining the benefits of a pre-loaded feature for the key unit.

Description:
FIELD OF INVENTION 
     The present invention relates generally to a keyboard apparatus used for electronic equipment such as personal computers, typewriters, calculators, word processors and the like, and, more particularly, to a key unit in a keyboard apparatus, as well as the keyboard apparatus itself, wherein the key unit is adapted to reduce the noise which is typically generated when a key unit is pushed or returns from the depressed position and hits the top plate of a keyboard or other type of shell around the key unit. 
     BACKGROUND OF THE INVENTION 
     Keyboards are known as signal input devices that allow transmission of a relevant signal to a host device in response to the mechanical pressure being applied to a certain key unit out of a plurality of key units disposed in a predetermined positional relationship on a board in an electronic device or equipment. While keyboards are used in a variety of different electronic devices, the keyboards utilized in these devices usually perform the same function. Namely, an individual key unit of a plurality of key units of a keyboard usually consists of a key button that can be depressed by application of the mechanical pressure to the top of the key button, urging the key unit into movable contact with a contact point on a conductive membrane formed on a circuit substrate of the keyboard, which produces an electrical connection and causes a signal to be sent to the host device. Examples of various keyboard devices and their operation are well known in the art and disclosed in U.S. Pat. Nos. 4,677,600, 5,516,996 and 5,565,865. 
     Generally, there are many types of different key units that can be utilized in a keyboard. For example, U.S. Pat. No. 5,456,541 describes resilient rubber, spring and mechanical types of key units. Similarly, a resilient rubber key unit is described in U.S. Pat. No. 5,565,865. 
     In a conventional key unit, the key unit has a resilient pad, usually made of a resilient rubber or silicon rubber material, and a plastic keycap that is mounted on top of the resilient pad. The plastic keycap extends in the axial direction through the pre-determined opening in the top plate of the keyboard to accommodate the axial movement of the pad and keycap in response to the mechanical pressure in the axial direction that is applied by the keyboard operator to the top surface of the plastic keycap. The resilient pad is mounted over a conductive membrane sheet structure. 
     Electrical conductivity is provided in a conventional conductive membrane sheet structure below the resilient pad which is formed by stacking a lower sheet and an upper sheet, on which conduction layers are formed respectively. The bottom surface of the resilient pad has a stem portion that moves in unison with the pad in the axial direction and affects the contact between the fixed contact on the lower sheet of the conductive membrane sheet structure formed on a circuit substrate and the movable contact of the upper sheet. The upper and lower sheets of the conductive membrane sheet structure are separated from each other by a predetermined gap or an air pocket formed by the spacer inserted therebetween. When the stem portion of the resilient pad urges the movable contact of the upper sheet into physical contact with the fixed contact of the lower sheet an electrical circuit is established. Alternatively, electric conductivity is provided by a semi membrane or a PCB type of conductive membrane, which comprise a single conductive layer formed on a membrane sheet or circuit substrate. When the stem portion of the resilient pad is urged in the axial direction a conductive portion of the stem portion completes an electric circuit between a fixed row contact point and a fixed column contact point. 
     In addition, a conventional key unit may have a “pre-loaded” feature which is accomplished by using a flange on the keycap to limit the axial movement of the key unit. The flange contacts a pair of plastic ribs which are fixedly suspended from the inner surface of a top plate of the keyboard apparatus. These plastic ribs act as a stop and limit the axial movement of the key unit when it returns from a depressed position to its normal position. 
     The pre-loading is typically used to add stability and insure a constant height of the keycap. However, because the keycap is pre-loaded, each time a user depresses and thereafter releases the key unit, the flange of the keycap, strikes against the plastic ribs creating an undesirable impact and noise, often referred to as “feedback noise.” Therefore, there is a need for an improved keyboard apparatus, in which the key units of the keyboard apparatus have the “pre-loaded” feature and associated advantages, but do not produce the impact and noise associated with the operation of conventional key units. Reduction of the impact and noise associated with the operation of keyboards in personal computers is particularly desirable because these devices are often used in enclosed public places, such as schoolrooms, on airplanes, and in large open office spaces that are subdivided into individual work areas, where the noise can be distracting and degrade productivity. 
     SUMMARY OF THE INVENTION 
     It is an object of the current invention to provide a keyboard apparatus that either eliminates or reduces the “feedback noise” during its operation. 
     Another object of the current invention is to provide an improved key unit which may be one of a variety of different types that has “pre-loaded” functionality and eliminates the above-mentioned feedback noise and impact, thereby providing a cost-effective solution to keyboard manufacturers, without limiting them to only one type of key unit. 
     A further object of the present invention is to provide an improved key unit for various types of electronic devices that utilize a keyboard with one or a plurality of key units, where the improved key unit contains means for cushioning the impact of a key unit against the top enclosure of a keyboard, thereby eliminating the feedback noise, and at the same time retaining the benefits of a “pre-loaded” feature for a key unit. 
     These and other objects of the invention are accomplished by providing a key unit having at least one resilient bumper positioned on or extending from the key unit which cushions the impact of the key unit against the top plate of the keyboard when the key unit returns from a depressed position to a normal pre-loaded position. The resilient bumper may be incorporated in a variety of different types of key units such as a resilient rubber type, spring type, mechanical type or any other type of key unit that may or may not contain a plastic keycap that covers the movable portions or key pad of the key unit. 
     These and other objects of the invention are accomplished by providing a key unit that is able to assume a depressed position comprising in one embodiment a member movable in a defined direction in response to pressure, the member having at least one resilient bumper. The key unit is a component of an apparatus that has a stop that restricts the movement of the key unit when the key unit is returned from the depressed position. In addition, the bumper of the key unit is movable into contact with the stop of the apparatus when the key unit is pushed or returned from the depressed position. 
     These and other objects of the invention are accomplished by providing an apparatus comprising at least one such key unit. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other objects, features and advantages of the invention, its construction and operation will be best understood from the following detailed description of preferred embodiments of the present invention, taken in conjunction with the accompanying drawings, of which: 
     FIG. 1 is a disassembled view of a key unit according to the present invention; 
     FIG. 2 is a disassembled view of a first type of a key unit according to the present invention; 
     FIG. 3A is a disassembled view of a second type of a key unit according to the present invention; 
     FIG. 3B is a disassembled view of a third type of a key unit according to the present invention; 
     FIG. 4 is a disassembled view of a fourth type of key unit according to the invention; 
     FIG. 5 is a disassembled view of a fifth type of a key unit according to the present invention; and 
     FIG. 6 is a sectional view of a key unit according to the present invention similar to that shown in FIG.  5 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The key unit according to the present invention will now be discussed with reference to the drawings in FIGS. 1 through 6 in which like reference numerals denote corresponding parts. FIG. 1 illustrates a key unit  61  according to the present invention comprising a member  60  having bumpers  62   a  and  62   b . In operation, the member  60  is moveable in the directions shown by the arrow A. Member  60  is included in an apparatus having a stop  64  which impacts bumpers  62   a  and  62   b  when member  60  moves upwards in the direction shown by arrow A. Member  60  assumes a depressed position in response to a condition, such as pressure exerted by a keyboard operator on the key unit  61 , and in the absence of the condition, resumes a normal position. Member  60  is either a single restorative component, as shown, or includes at least one restorative component, which is capable of responding to the absence of a condition, such as pressure, by restoring attached or physically proximate components to their normal position. The restoration component of member  60  is resilient or otherwise acts against the condition (i.e., the pressure exerted by the keyboard operator). In the absence of the condition, member  60  resumes a non-depressed position, which restores other components of the key unit which are attached to member  60  or physically proximate to member  60  to their normal position. Member  60  may produce a counter force in response to pressure and may store energy which, in the absence of pressure, restores attached or physically proximate components to their normal position. 
     In the case of member  60  being a single restorative component, exemplary embodiments of member  60  include but are not limited to a pad made of resilient material, such as silicon rubber, or any other type of rubber, a spring, a coil, an elastic band, a mechanical device operating using for example, hydraulics or magnetic forces or any other component capable of assuming a depressed position in response to a condition and in the absence of the condition, resuming a non-depressed position. If member  60  comprises a single component, bumpers  62   a  and  62   b  are attached to member  60 , or alternatively, bumpers  62   a  and  62   b  and member  60  are made as a one-piece unit. 
     In the case of member  60  being more than one component comprising at least one restorative component, member  60  may be a combination of hard plastic key cap or key top or any other component or combination of components used with at least one restorative component such as a pad made of resilient material, such as silicon rubber, or any other type of rubber, a spring, a coil, an elastic band, a mechanical device operating using for example, hydraulics or magnetic forces or any other component capable of assuming a depressed position in response to a condition and in the absence of the condition resuming a non-depressed position. If member  60  comprises more than one component, bumpers  62   a  and  62   b  may be attached to or manufactured as a one-piece unit with any component of member  60  which allows bumpers  62   a  and  62   b  to extend from member  60  and impact stop  64 . Bumpers  62   a  and  62   b  may be attached to or manufactured as a one-piece unit with a restorative component of member  60  as long as bumpers  62   a  and  62   b  do not excessively impede the restoration capabilities of the restorative component. 
     As can be seen from FIG. 1, bumpers  62   a  and  62   b  extend from member  60  and cushion the impact of member  60  when member  60  returns to a normal position which reduces or eliminates feedback noise. Bumpers  62   a  and  62   b  are made of resilient or cushioning material, such as silicon rubber or any other rubber or resilient material, Styrofoam, or foam. Bumpers  62   a  and  62   b  may be ribs, ridges or extensions of member  60 . As shown, bumpers  62   a  and  62   b  cushion impact between member  60  and the stop  64  of the apparatus when member  60  resumes a normal, non-depressed position. Alternatively, or in addition, bumpers  62   a  and  62   b  may cushion impact between member  60  and the stop  64  of the apparatus when member  60  assumes a depressed position. Bumpers  62   a  and  62   b  may be used for a pre-loaded key unit. 
     FIG. 2 illustrates a first embodiment of the present invention, key unit  102 . The key unit  102  which is able to assume a depressed position comprises a member where the member is a resilient pad  70  movable in a defined direction (up and down in the axial direction) in response to pressure. The pressure is exerted by a keyboard operator pushing the top surface  75  of resilient pad  70 . The resilient pad  70  has resilient bumpers  125   a  and  125   b . The bumpers  125   a  and  125   b  are protrusions from the sides of the resilient pad  70 . The resilient pad  70  with bumpers  125   a  and  125   b  are movable in the axial direction into contact with stop  170  when the key unit  102  is returned from the depressed position. The stop  170  is the top plate of the keyboard having inner surface  172  and pre-determined opening  160 . The resilient pad  70  extends in the axial direction through the pre-determined opening  160  in the top plate  170 . The resilient pad  70  is preferably made of a rubber material, such as, for example, silicon rubber. A key cover  90  may be attached (directly or indirectly) to the top surface  75  of the resilient pad  70 . In that case, the keyboard operator pushes the key cover  90  to depress the key. Key cover  90  is made of plastic, or any other material which is resistant to wear due to pushing, and indicia of the key unit, such as an alphanumeric symbol or other indicia may be printed or engraved on the key cover  90 . 
     FIG. 3A illustrates a second embodiment of the present invention, key unit  104 . Key unit  104  comprises a member, where the member includes a base  94  which is movable in a defined direction (up and down in the axial direction) in response to pressure exerted by a keyboard operator pushing key cover  90  thereby allowing key unit  104  to assume a depressed position. Key cover  90  may be fixed to or rest directly on the top surface (not shown) of base  94  or key cover  90  and base  94  may be manufactured as a single piece. Base  94  has bumpers  96   a  and  96   b . Bumpers  96   a  and  96   b  protrude from the sides of base  94  and are movable in the axial direction into contact with stop  170  when the key unit  104  is returned from the depressed position. The member of key unit  104  also includes a restorative device  93  which is attached to the bottom surface of the base  94  when key unit  104  is assembled. When pressure is exerted by the keyboard operator, conductive layer  190  moves downward to cause contact which forms an electrical circuit and produces a signal to the keyboard apparatus. The restorative device acts against the pressure by the operator. When the keyboard operator ceases to apply pressure, the natural elasticity of conductive layer  190  breaks the electrical connection so that no further signal is produced to the keyboard. Restorative device  93  responds by restoring base  94  and bumpers  96   a  and  96   b  to their normal position. 
     The base  94  may extend in the axial direction through the predetermined opening  160  in the top plate  170  or alternatively, only the restorative device  93  may extend through the predetermined opening  160 . The base  94  need not be made of a resilient material but may be made of plastic, or any other non-resilient material. 
     In an alternative embodiment, as shown in FIG. 3B, the member is made of base  94  and restorative device  93 . The restorative device  93  of key unit  106  is a resilient spring  92  which is connected to the bottom surface of base  94 . 
     FIG. 4 illustrates a fourth embodiment of the present invention in which the key unit comprises resilient pad  120  having a thick lower portion  122  and a thin upper portion  123 . In this embodiment, the stop is provided by a pair of ribs  175   a  and  175   b  on the inner surface  172  of top plate  170 . The thinner portion  123  of resilient pad  120  extends in the axial direction through the pre-determined opening  160  in the top plate  170 . Since this embodiment does not include key cover  90 , the keyboard operator applies pressure directly to the top of thinner portion  123  thereby producing movement of the pad in the axial direction. In this embodiment, the indicia of the key unit, such as an alphanumeric symbol or other indicia is printed on the top surface  174  of top plate  170 . 
     FIG. 5 illustrates a fifth embodiment of the present invention. As shown in FIG. 4, key unit  110  has a plastic keycap  130  that is mounted on top of the resilient pad  120 . The plastic keycap  130  extends in the axial direction through the pre-determined opening  160  in the top plate  170  of the keyboard to accommodate the axial movement of the resilient pad  120  and keycap  130  in response to the mechanical pressure in the axial direction that is applied by the keyboard operator to the top surface  135  of the plastic keycap  130 . 
     Referring to FIGS. 4 and 5, impact and feedback noise are reduced or eliminated by a pair of resilient bumpers  125   a  and  125   b , preferably made of a rubber material such as silicon rubber material, that come into contact with the stop of the top plate  170 . These resilient bumpers may be ribs, ridges or extensions of the resilient pad  120  extending in the axial direction, as shown in FIGS. 3 and 4. The stop is preferably a pair of ribs  175   a  and  175   b  fixedly suspended from the inner surface  172  of the top plate  170  of the keyboard as shown in FIGS. 3 and 4. Alternatively, the stop may be provided by the top plate  170  of the keyboard itself as shown in FIG. 2A, or any other known means that would physically restrict the axial movement of the key unit by contact with the resilient bumpers  125   a  and  125   b  when the key unit returns from a depressed position to a normal position. 
     In the embodiment shown in FIG. 5, the plastic keycap  130  has a flange  132  that accommodates the resilient bumpers  125   a  and  125   b  through a pair of corresponding apertures  134   a  and  134   b  in the flange. This allows the resilient bumpers to come into physical contact with the stop provided by the pair of corresponding ribs  175   a  and  175   b , instead of delimiting the axial movement of a key unit through the contact of the flange  132  and the stop, as in conventional key units known in the prior art. The flange  132  rests upon shoulder  133  of the resilient pad  120 . 
     Referring to FIG. 5, the plastic keycap  130  preferably comprises a thicker button base as the upper part of the keycap. The upper surface  135  of the button base preferably contains the indicia of the key unit such as an alphanumeric symbol or other indicia. 
     As shown in FIG. 6, in the preferred embodiments of the current invention, the resilient pad  120  is mounted over a conductive membrane sheet structure  190  that is formed by two conductive layers and a gap in-between these layers. The conductive membrane sheet structure  190  produces an electrical signal in response to the mechanical pressure applied to the key unit. The conductive connection that produces the electrical signal of the key unit according to the present invention is accomplished in the same way as the conductive connection of a conventional key unit. The bottom surface  125  of the resilient pad  120  has a stem portion  128  that moves in unison with the pad  120  in the axial direction into contact with a surface contact point on upper sheet  192  of the conductive membrane sheet structure  190 , thereby affecting the contact between the fixed contact  195  formed on the lower sheet  194  of the conductive membrane sheet structure  190  which may be formed on a circuit substrate (not shown) and the movable contact  193  of the upper sheet  192 . The upper and lower sheets are separated from each other by a predetermined gap or air pocket  191 . Alternatively a semi membrane, a PCB type of conductive membrane may be used as the means for producing an electrical signal in response to mechanical pressure enabled in the key unit. Such structure forms the electric contact and produces the signal to the keyboard apparatus in response to the contact between the stem portion  128  of the resilient pad  120  and a pre-determined contact point on the conductive membrane which may be formed on a circuit substrate. FIG. 5 further shows the key cap  130  having a button base in the upper part of the key cap. The upper surface of the button base  135  may contain indicia of the key unit. The bottom base may be a thicker part of the key cap  120 . 
     Although the invention has been described with reference to the preferred embodiments, it will be apparent to one skilled in the art that variations and modifications are contemplated within the spirit and scope of the invention. The means for producing an electrical signal in response to mechanical pressure or movement may be any type of structure known such as a capacitive structure where the pressure changes the capacitance of circuit elements, a thermosensitive, inductive, photosensitive or piezoelectric structure. The drawings and description of the preferred embodiment are made by way of example rather than to limit the scope of the invention, and it is intended to cover withing the spirit and scope of the invention all such changes and modifications.