|Publication number||US3767022 A|
|Publication date||Oct 23, 1973|
|Filing date||Apr 24, 1970|
|Priority date||Apr 24, 1970|
|Publication number||US 3767022 A, US 3767022A, US-A-3767022, US3767022 A, US3767022A|
|Original Assignee||Singer Co|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (8), Referenced by (27), Classifications (19)|
|External Links: USPTO, USPTO Assignment, Espacenet|
EJ111100 States Patent 1 1 1111 3,767,022 015011 Oct. 23, 1973 ' RETURN SPRING KEY STEM BOOT 2,430,064 11/1947 Lawson 74/18 2 X 2,506,140 5 1950 Delan  Inventor: Cecil G. Olson, San Franclsco, Cal1f. 2,687,015 851954 Edwaryds t m N Y k, 2,749,757 6/1956 Adelt  Asslgnee g z pan)" W or 2,755,671 7/1956 Delany.....
2,755,672 7/1956 Delany.....
22 Filed: Apr. 24, 1970 2,896,987 7/1959 Meyer .II. 74/18.2 21 Appl. No.2 29,744
7 Related App 11 6311011 D515 Primary ExaminerEdgar S. Burr  Continuation Of $51. NO. 518,426, Jan 3, 1966. fltwmey-charles Lepchmsk Eiffilfilil 197/98, 74/l8.2, 178/17, 250/220, 250/229, 340/365, 235/145, 200/168  111%. CI B4lj 5/08 [57 ABSTRACT  Field 01 Search 197/98; 74/182,
'219; 235/145; ZOO/159 168 ual keys of a manually actuated keyboard.
 References Cited UNITED STATES PATENTS 8 Clalms, 9 Drawmg Flgures 2,265,496 12/1941 Shaw 74/l8.2 X
A stem boot for providing breakaway feel for individ- PAIENIEDBCI 23 Ian 3.767.022
" sum 1 UF 2 INVENTORS ATTORNEY pmmmomzs m SHEET 2 OF 2 3. 767,022
CONVENTIONAL D (DEFLECTION) RETURN SPRING KEY STEM BOOT STATEMENT OF RELATED CASES This application is a continuation of US. patent application Ser. No. 518,426, filed Jan. 3, I966, now abandoned.
This invention relates to keyboards that utilize unique energy path patterns to identify actuated keyboard key elements, and more particularly to inexpensive and reliable key mechanisms for such keyboards that can also provide a breakaway feel when such key mechanisms are manually actuated.
One object of this invention is to provide an improved keyboard device.
Another object of this invention is to provide a keyboard which is economical to fabricate and reliable in operation.
A still further object of this invention is a keyboard device having a plurality of key mechanisms, each of which provide a breakaway feel"- when they are manually actuated.
A keyboard device utilizing this invention includes a plurality of key mechanisms, each including a stem portion having a keyboard key element at one end thereof and a code card located a distance away from the key element. Each code card has a first portion including a plurality of channels or openings thereon with the channels on the first portion of each code card being juxtaposed the channels on the first portion of the other code cards so as to form a plurality of passageways or paths which extend through or along the plurality of code cards. Each code card also has a second portion adjacent the first portion with predetermined ones of said channels on said first portion also appearing on, or extending into, the second portion. Mounting means are provided for the plurality of key mechanisms that permit each code card to be displaced with respect to the plurality of passageways by depressing the associated keyboard key element so that the absence of at least one channel, or path, on the second portion of the associated code card interrupts at least one passageway to provide a pattern of passageway interruptions that identify the depressed keyboard key element.
In a variation of the above-noted keyboard, the plurality of key stems and code cards comprise a unitary structure which includes an elongated primary support member having a plurality of juxtaposed elongated secondary support members emanating from the length thereof, with each secondary support member having one of the plurality of juxtaposed code cards and one of the key stems as a part thereof. Each secondary support member has a portion of its length adjacent the primary support member reduced in cross-sectional area to permit the secondary support members to be partially rotatable around the primary support member.-
In accordance with the present invention, a unique stem boot surrounds each of the key stems and is located intermediate the keyboard key element and mounting means which supports the key stem. The stem boot includes a hollow elastic member having a portion of its length adjacent the mounting means being cylindrical and at least a portion of its remaining length being a conic section, with the smallest circumference portion of the conic section being adjacent the key element and the largest circumference portion of the conic section forming a junction with one end of the cylindrical section. The angle of the conic section with respect to the cylindrical poirtion is such that hoop stresses occur at the junction of the cylindrical and conic sections when the associated key element is depressed. Also, the thickness of the conic section increases along its length from the junction of the cylindrical section with the conic section to the smallest circumference portion of the conic section. This unique stem boot provides a breakaway feel when the keyboard key elements are manually actuated which enables high manual operating speeds to be obtained with the keyboard.
This invention, as well as other objects, features, aspects and advantages thereof, will be readily apparent from consideration of the following detailed description relating to the accompanying drawings in which:
FIG. 1 is a top plan view, partially in section, of a keyboard device, in accordance with the present invention;
FIG. 2 is a cross-sectional elevational view taken along the plane indicated by the line 2-2 of FIG. 1, which illustrates the code cards and key stems of the keyboard key mechanisms comprising the subject invention;
FIG. 2A is a partial cross-sectional elevational view similar to FIG. 2, but showing the relative positions of the code cards after one of the keyboard key elements has been depressed;
FIG. 3 is an exploded, perspective view which more clearly illustrates the keyboard key mechanisms of FIGS. 1 and 2;
FIGS. 4A, 4B and 4C are partial cross-sectional views for illustrating a unique key stem boot in accordance with the present invention, while the associated keyboard key element is being depressed;
FIG. 5 illustrates a force versus distance diagram for conventional spring-loaded keyboard key elements, as compared to the force required to actuate a keyboard key element which utilizes the unique key stem boot of this invention; and
FIG. 6 is a perspective view of a unitary molded structure which contains a plurality of keyboard key mechanisms.
Referring now to the drawings, wherein like reference characters designate like or corresponding parts throughout the several views, there is illustrated in FIGS. 1 and 2 a keyboard device according to this invention which comprises an elongated hollow housing or mounting means 11 for a plurality of keyboard key mechanisms. The housing 11 includes a base portion 12 to which an enclosure 13 is secured by any suitable means, such as screws 14. Each key mechanism contains a stem 15 which is slidably supported by the housing 11 and at least partially contained therein. One end of each stem protrudes through the enclosure portion 13 and is adapted to receive a keyboard key element, or key top, 16 at the end thereof. Surrounding each key stem intermediate the enclosure portion 13 and the key element 16 is a hollow elastic stem boot 17 which is described in detail hereinbelow. The other end of each stem passes through the base portion 12 of the housing 11. As illustrated by FIG. 1, each stem has a crosssection that prevents its rotation within the housing 11 and since each end of the stems 15 is slidably supported by the housing 11, each stem can be accurately positioned within the housing 11.
Each stem includes as a part thereof a flat rectangular portion or code card 18. Each code card contains a first, or bottom, portion which includes a plurality of channels, or openings, 19. The code cards of each stem are juxtaposed,or positioned, adjacent the code cards of the other stems, so that the plurality of openings 19 are juxtaposed to form a plurality of passageways, or paths, which are substantially normal to the plurality of code cards. As illustrated by FIG. 1, the lateral distance separating the plurality of juxtaposed code cards is not critical and, therefore, need not be uniform. In one embodiment of the present invention which was constructed, this spacing varied from three-sixteenths of an inch to three-eighths of an inch. Each stem and its associated code card can be a unitary structure which can be molded from any suitable material, such as a plastic. The unitary structure can also be stamped, pressed,
etc., and can also be fabricated from sheet metal. Lo-
cated above and adjacent the channels, or openings, 19, on the first portion of each code card, is a second portion into which selected ones of the openings, or channels, on the first portion may extend. These openings, or channels, in the second portion of the code card, or the absence thereof, identify the alphanumeric or other values given to the associated keyboard key elemenLThe channels, or openings, which extend into the second portion of each code card may be formed when each stem and associated code card is molded. Alternatively, the second portion of each code card may contain a plurality of knockout portions 21 adjacent the openings, or channels, 19, on the first portion of each code card which enables the coded second portion of each code card to be formed by removing the appropriate knockout portions 21. Although the openings on the lower portion of each code card are illustrated as being enclosed, it is to be understood that an enclosed opening is not necessary and that a plurality of ducts, channels or grooves along the bottom portion of the first portion of each code card will suffice to form the plurality of passageways, or paths, which extend through the plurality of juxtaposed code cards.
Located at one end of the plurality of juxtaposed code cards is an energy source, as illustrated in FIG. 1, which may comprise a light source 26 and reflecting means 27 for forming the light generated by the source 26 into a rectangular bar of light. This light source is located adjacent the first portion of the nearest code card such that the plurality of code cards have their first portion normal'to the rectangular bar of light formed by the light source 26 and reflecting means 27. Therefore, the plurality of passageways that extend along the plurality of code cards constitute a plurality of energy paths for the light produced by the source 26.
Located at the other end of the plurality of code cards and adjacent the openings on the nearest code card are a plurality of energy pickup devices, such as photo cells 25, each of which is associated with one of the energy passageways which extend'through the first portion of the plurality of code cards.
The plurality of energy paths, or passageways, extending through the plurality of juxtaposed coded cards are clearly illustrated by FIG. 3, which is an exploded perspective view of several of the keyboard key mechanisms illustrated in FIGS. 1 and 2. Reference to FIG. 3 shows that the rectangular bar of lightformed by the light source 27 and focusing, or reflecting, means 26, is directed to the first portion of each code card and that the plurality of openings or channels on the first portion of the juxtaposed code cards divide the light into a plurality of energy paths indicated by the reference character 20. These energy paths extend along and through the plurality of juxtaposed code cards and terminate at photo cells 25.
Each stem and associated code card is mounted within the keyboard housing 1 1 such that it can only be moved substantially normal to the plurality of energy or light paths 20 that extend through the plurality of code cards. Accordingly, when a keyboard key element is depressed, its associated stem moves downward, causing its code card to be moved normally, or substantially perpendicular to, the plurality of energy paths. This causes the second portion of the selected code card to be in the position formerly occupied by the first portion of the associated code card. This causes the absence of openings, or channels, on the second portion of the depressed code card to interrupt one or more of the energy paths which extend through the plurality of juxtaposed code cards, as is illustrated by FIG. 2A, wherein it is shown that only one energy path 20 remains, due to the single opening, or channel, 19' extending into the second portion of the selected code card. As described above, the number of openings, or channels, on the second portion of each code card identify the alphanumeric, or other value, given to the associated keyboard key element. Accordingly, depression of one of the keyboard key elements interrupts the plurality of energy, or light, paths 20 which extend through the plurality of juxtaposed code cards in such a manner that the pattern of interruptions identify the depressed keyboard key element, by causing predetermined ones of the pickup devices or photo cells 25 not to be energized. Generally, the output-of the pickup, or photo cells,25 is coupled to a matrix (not shown), or other suitable decoding device, whereby the patterns of energy interruptions are transformed into a code suitable for associated circuitry or equipment.
FIGS. 1 through 3 illustrate a typewriter keyboard device wherein the keyboard key elements 16 represent typewriter alphanumeric values or functional values, such as the space bar 22. The present invention, however, is not limited to thesevalues inasmuch as other functions, or values, may be coded on the code cards 18. For example, the irregular spacing of the code cards 18, as illustrated by FIG. 1, permits other code cards to be inserted therebetween, which other code cards may have other typewriter functional values, such as typewriter tab set, tab clear, etc., and other nontypewriter functions, such as program changing and modification, etc. Depression of two or more keyboard key elements simultaneously can be prevented by incorporating a mechanical interlock device (not shown) with the keyboard device of FIGS. 1 through 3, such mechanical interlocks being well-known in the art. The keyboard device may also includean electronic interlock, whereby the use of a sufficient number of openno indication or feel that the key is actuated until the point 31 is reached, at which time the key element is fully depressed, as illustrated by the diagram of FIG. 5. The curve 32, on the other hand, which shows the minimum force required to actuate the key mechanism of this invention, shows that the force required to actuate the key mechanism increases until the point 33 is reached, after which the force required to actuate the key mechanism decreases until the point 34 is reached, at which time the key element has been selected, or actuated.
After the point 33 is reached, the operator depressing the key element can feel the reduced force required to fully actuate the key mechanism, such that the reduced actuating force produces a breakaway feel which permits the keyboard to be manually operated at a higher rate of speed than a conventionally springloaded keyboard. This is so because the feel imparted to the actuating finger of the operator at the point 33 enables the operator to mentally commence the necessary physical motions required to select the next keyboard key element. This breakaway feel is present in electric typewriters and is highly desirable in other keyboard devices and has only been obtained heretofore in the prior art by relatively expensive and complex mechanisms associated with keyboard key mechanisms.
A breakaway feeliis obtained in accordance with the present invention by the hollow, elastic, cylindrical boot 17 illustrated in FIG. 2. This boot surrounds the key stem protruding from the enclosure 13 and is located intermediate the keyboard key element 16 and the enclosure, or mounting portion, 13. FIGS. 4A, 4B and 4C illustrate this unique stem boot in cross-section for various degrees of key element depression. FIG. 4A illustrates the stem boot when the key 16 is in its normal, or rest, position, and shows the stem boot as comprising a cylindrical section which is adjacent, or secured to, the enclosure 13 anda tapered or conic section, the smallest circumference portion of which is adjacent the keyboard key element 16. The largest circumference portion of the conic section forms a junction with the end of the cylindrical section remote from the enclosure 13. The thickness of the tapered or conic section increases along its length from the junction of the conic section with the cylindrical section to the end of the conic section adjacent the key element 16. In accordance with one embodiment of the boot which was constructed, the inside surface of the conic section was at a 30 angle with respect to the longitudinal axis of the cylindrical section or the key stem which the stem boot surrounds, the outside surface of the conic section was at a 35 angle with respect to the longitudinal axis of the cylindrical section of the boot and the longitudinal axis of the key stem and the key stem boot 17 was constructed from an elastic material, such as silicone rubber, which was molded into the above described shape.
When the key element 16 is initially depressed, the conic section causes hoop stresses to occur at the junction of the conic and cylindrical sections, such that the boot at this junction tends to bulge outwardly, as illustrated by FIG. 4B. These hoop stresses cause stresses to back up into the conic section. However, due to the increasing thickness of the conic section, the conic section does not bend or wrinkle at a point along its length adjacent to the key element 16. Rather, any bending of the conic section of the boot takes place adjacent the junction of the conic and cylindrical sections as illustrated in FIG. 4B. When the key element is fully actuated or depressed, corresponding to the point 34 in FIG. 5, the stem boot has a cross-section as illustrated in FIG. 4C. When in the position illustrated in FIG. 4C, the stem boot has an upward resilient force that causes the key mechanism to return to its normal, or rest, position when the operator releases the key element. If the stem boot were to be further depressed downwardly be- .yond that illustrated in FIG. 4C, the boot would pass an equilibrium point after which the boot would remain depressed after operator actuating force was released. In other words, the stem boot 17 has the characteristics of a toggle in that it has two stable states, one being illustrated by FIG. 4A and another being when it is more fully depressed downwardly than that illustrated in FIG. 4C. In order to prevent the equilibrium point from being reached, the key element 16 has a side portion 23 which limits, or stops, the downward movement of the key element to a position before the equilibrium point of the boot is reached or exceeded. As illustrated by FIGS. 4A, 4B and 4C, the boot itself may contain a raised portion 28 which limits the downward movement of the key element to prevent the equilibrium point of the boot toggle from being reached. The .minimum force required to actuate, or depress, the stem boot of FIGS. 4A, 4B and 4C is illustrated by the curve 32 of FIG. 5, which shows that the minimum force breaks away at the point 33 to provide the highly desirable breakaway feel" which enables a relatively high manual operating speed of the keyboard device.
The stem and associated code card of each of the keyboard key mechanisms may, as described hereinabove, be molded from a suitable material, such as plastic, and is, therefore, a very simple and economical structure to fabricate. FIG. 6 illustrates a partial perspective view of another embodiment of the,present invention, wherein the plurality of stems and code cards comprising a plurality of keyboard key mechanisms are a unitary molded structure which may be formed from any suitable material, such as a plastic. Reference to FIG. 6 shows that such a unitary structure includes an elongated primary support member 35 having a plurality of juxtaposed elongated secondary support members 36 emanating from the length thereof. Each secondary support member contains one of the abovedescribed stems 15 and code cards 18' such that the plurality of code cards are normally juxtaposed to form the plurality of energy passages, or paths, as described above. In order to permit each code card to be partially movable or rotatable around the primary support member 35, the cross-sectional area of each secondary support member 36 has a portion of its length adjacent the primary support member reduced in cross-sectional area. The amount of stress, or deflection, which takes place near the junction of the secondary support member with the primary support members can be varied by varying the distance of the code cards from the primary support member for a given displacement of the code cards. in this manner, it is relatively easy to ensure that constant and continuous partial deflection of the code cards around the primary support member will not cause a failure where the secondary support members join and become a part of the primary support member. As with the code card sections previously described, the openings, or channels, in the second portion of each code card can be molded at the time the entire unitary structure is molded, or knockout portions may be molded thereon to permit easy coding of the second portion of the code cards after molding the entire unitary structure.
What has been described is a simple and economical keyboard device which provides a plurality of energy paths, or passageways, and means for providing a pattern of passageway interruptions when a keyboard key element is depressed that identify the actuated key element. Simple and economical meansare also provided that give the keyboard key elements a break-away feel when actuated, that enablesa high manual operating speed of the-subject keyboard.
It should be understood, of course, that the foregoing detailed description relates only to preferred embodiments of the present invention, and that numerous modifications or alterations may be made therein without departing from the spirit and scope of the invention, as set forth in the appended claims.
What is claimed is:
l. A spring-like stem boot adapted to surround a reciprocable stem coupled to a key element for providing arestoring force urging said key element toward a rest position, said stem boot comprising a hollow, resilient member including: 1
a cylindrical base portion adapted to be secured to a mounting means,
a top portion having a central bore adapted to be coupled to said stem, the outer diameter of said top portion being smaller than theinner diameter of said cylindrical base portion,
- a frusto-conical intermediate portion forming a first integral junction at the largest diameter portion thereof with a first end of said cylindrical base portion and forming a second integral junction at the smallest diameter portion thereof with said top portion, the thickness of said frusto-conical portion increasing along the length thereof from said first junction to said second junction,
said recited characteristics of said cylindrical base and frusto-conical portions of said stem boot providing a nonlinear restoring force exhibiting increasing resistance with increased displacement of said key element up to a maximum and thereafter exhibiting decreasing resistance to increased displacement of said key element,
said recited structure of said stem boot enabling said stem boot to function as a toggle having two stable states, one of which is said rest position, and
stop means associated with said stern boot for preventing displacement of said key element past the equilibrium of said toggle.
2. The stem boot of claim 1 wherein said frustoconical portion and the axis of said cylindrical portion are formed at an angle enabling the formation of hoop stresses at said first junction when said key element is actuated.
3. The stem boot of claim 2 wherein said angle is in the range from 30 to 35.
4. The stem boot of claim 1 wherein the angle between the outer surface of said frusto-conical portion and the axis of said cylindrical portion is substantially 30 and the angle between the inner surface of said frusto-conical portion and said axis is substantially 35.
5. The stem boot of claim 1 wherein said stop means comprises an upturned annular flange arranged circumferentially of said cylindrical base portion and adapted to abut the advancing edge of said key element.
6. A return spring for biasing a pushbutton supporting plunger away from a guide base relative to which the plunger is movable along a line substantially normal to the base, the spring comprising a tubular element fabricated of a resilient elastomeric material, the element being arranged for disposition, coaxially of the plunger between the base and the pushbutton and normally configured to define first and second opposite coaxially aligned terminal cylindrical portions and a central frusto-conical portion integrally connected circumferentially of its opposite ends with the adjacent ends of the first and second cylindrical portions respectively, the first cylindrical portion having an inner diameter sized to mate with the plunger adjacent the pushbutton end thereof, the inner diameter of the second cylindrical portion being greater than the outer diameter of the first cylindrical portion, the second cylindrical portion being arranged for support by'the base circumferentially of the plunger and having sufficient length'that the end thereof connected to said frusto-conical portion is deformable radially outwardly to enable said frusto-conical portion to deform into a'planarstate between said first and second cylindrical portions inresponse to a compressive load applied axially of the tubular element of depression of said plunger, said frustoconical portion deforming past said planar state with a snap action in response to additional compressive loads. 1 I
7. Apparatus according to claim 6 in which the wall of the frusto-conical portion of the element decreases in thickness from the end thereof connected to the first cylindrical portion to the end thereof connected to the second cylindrical portion.
8. Apparatus according to claim 6 wherein the end of the second cylindrical portion opposite from the'frustoconical portion is joined to a flat sheet of the resilient material peripherally of an aperture in the sheet.
t w w I: v
|Cited Patent||Filing date||Publication date||Applicant||Title|
|US2265496 *||May 13, 1940||Dec 9, 1941||Penn Electric Switch Co||Pilot valve|
|US2430064 *||May 5, 1944||Nov 4, 1947||Gen Motors Corp||Dustproof and moistureproof switch casing|
|US2506140 *||Jul 26, 1946||May 2, 1950||Delany Reaity Corp||Seal unit for flush valve actuators|
|US2687015 *||Jan 18, 1949||Aug 24, 1954||Chrysler Corp||Boot for master cylinders|
|US2749757 *||Jul 14, 1954||Jun 12, 1956||United Parts Mfg Co||Sealing boot|
|US2755671 *||Sep 20, 1951||Jul 24, 1956||Delany Realty Corp||Resilient sealing units for flush valve actuators|
|US2755672 *||Feb 27, 1953||Jul 24, 1956||Delany Realty Corp||Sealing unit for flush valve actuator|
|US2896987 *||Dec 9, 1955||Jul 28, 1959||Equi Flex Products Inc||Pressure seal structure|
|Citing Patent||Filing date||Publication date||Applicant||Title|
|US3882295 *||Oct 4, 1973||May 6, 1975||Illinois Tool Works||Tactile feedback switch mechanism|
|US3964593 *||Apr 8, 1974||Jun 22, 1976||Alphameric Keyboards Limited||Keyboards|
|US3974905 *||Sep 23, 1974||Aug 17, 1976||Xerox Corporation||Key arm mechanism|
|US3976876 *||Jun 3, 1974||Aug 24, 1976||Brocker Dale C||Signal control apparatus|
|US4049964 *||Apr 1, 1976||Sep 20, 1977||Cavitron Corporation||Optical switching device|
|US4152699 *||Mar 14, 1977||May 1, 1979||Lothar Sachsse||Optical keyboard having a plurality of pivotal light obstructing code bars|
|US4159183 *||Nov 2, 1977||Jun 26, 1979||Olympia Werke Ag||Keyboard employing photoelectric key actuation sensing|
|US4161637 *||Feb 22, 1977||Jul 17, 1979||Priesemuth W||Pushbutton switch|
|US4230922 *||Apr 30, 1979||Oct 28, 1980||Cherry Electrical Products Corp.||Seal assembly for switch actuator|
|US4604509 *||Feb 1, 1985||Aug 5, 1986||Honeywell Inc.||Elastomeric push button return element for providing enhanced tactile feedback|
|US4673780 *||Feb 10, 1986||Jun 16, 1987||Eaton Corporation||Sealed rectangular pushbutton switch|
|US4806908 *||May 14, 1987||Feb 21, 1989||Astronics Corporation||Low profile backlighted keyboard|
|US4833446 *||Feb 12, 1987||May 23, 1989||Ergoplic Ltd.||Keyboard apparatus and method|
|US4860008 *||Apr 20, 1987||Aug 22, 1989||Claude Battarel||Radiation interruption keyboard|
|US5145058 *||Jul 16, 1991||Sep 8, 1992||Lee Sam San||Notebook computer key|
|US5319996 *||Aug 13, 1993||Jun 14, 1994||Kransco||Debris resistant foot pedal switch assembly|
|US5459446 *||Oct 21, 1994||Oct 17, 1995||Texas Instruments Incorporated||Fluid splash barrier apparatus for aircraft circuit breakers and the like|
|US6791480||Dec 4, 1998||Sep 14, 2004||Alan K. Uke||Method of preventing and/or alleviating repetitive use injury to electronic computer keyboard operator|
|US7252444 *||Apr 8, 2004||Aug 7, 2007||Research In Motion Limited||Switch configuration|
|US7485816||Feb 8, 2007||Feb 3, 2009||Research In Motion Limited||Switch configuration|
|US7777138||Jan 28, 2009||Aug 17, 2010||Research In Motion Limited||Switch configuration|
|US20050227632 *||Apr 8, 2004||Oct 13, 2005||Ladouceur Norman M||Switch configuration|
|US20070125630 *||Feb 8, 2007||Jun 7, 2007||Ladouceur Norman M||Switch configuration|
|US20090134000 *||Jan 28, 2009||May 28, 2009||Ladouceur Norman M||Switch configuration|
|US20100078301 *||Sep 9, 2009||Apr 1, 2010||Darfon Electronics Corp.||Keyboard structure|
|EP0054644A1 *||Oct 10, 1981||Jun 30, 1982||BURROUGHS CORPORATION (a Michigan corporation)||Photo-optical keyboard having light attenuating means|
|EP0085645A2 *||Feb 1, 1983||Aug 10, 1983||ERGOPLIC MAKASHOT (1981) Ltd.||Keyboard apparatus|
|U.S. Classification||400/481, 178/17.00C, 200/521, 200/302.2, 400/490, 400/477, 200/293, 235/145.00R, 250/229, 74/18.2|
|International Classification||B41J5/00, B41J5/26, H01H13/50|
|Cooperative Classification||B41J5/26, B41J5/08, H01H13/50|
|European Classification||B41J5/08, H01H13/50, B41J5/26|