Keyboard
O Umted States Patent 11 1 [m 3,879,602  
 Walker 5] Apr. 22, 1975 I5 KEYBOARD 2324mm 4/l96l Cuzan IOU/I59 A 3. 5. 3 5 3352 5 [75] Inventor Mexand&#34; 51:32:; 335/235 VIeW&#39; 0111i 3.443.043 5mm Schmid-Zellcr ct al. 335/205 Assignee: NJIimensions Inc. Mountain Vie, 3.736.397 5I|973 Pcderscn 200/5 R Calif.  
 [22] Filed: June 11 1973 Primary EA&#39;tlIHiIIt&#39;f-SQPhfl J. Tomsky [2&#39;] A I N 368 8 Atlanta Agent, or F/rm-R0bert G, Slick pp. 0.: ,9 l]  
 1521 u.s. c| 235/145 R: l97/98; 335/205 1571 ABSTRACT [5]] Int. Cl G06c 7/02 I I Y 5s 1 Field of Search 235/145 R; 340/365 R; f f P keys 5&#34; l97/98&#39; 115/ 09 10 R H9 A &#39;59 B ranged to engage and mo\e a member. both reslhently 6 5 6 6 6 i; 1 and magnetically restrained, from a non-operative to an operative position to introduce input data into an [56] inferences Cited glregzolrilli umt such as a pnnler, calculator. computer UNITED STATES PATENTS 2.802.204 8/l957 Kcnnclly cl :1]. ZOO/61.45 M 4 Claims. 7 Drawing Figures 4 4 2A \\\N\\\\ &#34;l 3 w 36 &#39;IIf&#39;IIA g PATENTEUAPRZZISYS 3.879.602  
 sum 2 pf z Jlllllllllllfillllllllllii :KEY DISPLACEMENT KEYBOARD FIELD OF THE INVENTION The present invention relates generally to keyboards and more particularly to a keyboard for selectively controlling the alphanumeric or other input data to electrical or electronic devices such as printers, calculators. computers. or the like.  
 BACKGROUND OF THE INVENTION Keyboards have been utilized for many years to pro vide the selective input data to typewriters. calculators, computers, and other instruments, whether the actual actuation be manual or electrical. More recently, a number of relatively small, battery-powered electronic calculators, printers, and similar units have been devised and although cost has been a prime consideration, the complexity in structural elements and their assembly has placed such units beyond the range of economic justification except in very specialized cases. By way of example, a calculator which will multiply, divide, add and subtract, whose cost approximates $400.00, cannot be reasonably utilized by school children for educational purposes where a large number of the units are required. Furthermore, in addition to the economic problem resultant from the relatively high initial cost of such units, their continued and frequent use for educational purposes has resulted in relatively high replacement and maintenance costs which have further aggravated the economic problem.  
 SUMMARY OF THE PRESENT INVENTION It is the general objective of the present invention to provide an effective, relatively simple, readily fabricated. and low cost keyboard for introducing operatorselected input data to electronic calculators, computers. printers, or analogous devices, which keyboard at the same time has an extended useful life and is also easy to maintain and/or repair when required.  
  To achieve such objective, a plurality of manuallydepressible keys are mounted for movement through appropriate apertures in the top plate of a housing for the entire device, whatever form it may take. In the interior of the housing, and more particularly below the surface of the top plate, each key is arranged to engage and depress a movable member from an upper nonoperative position to a lower operative position whereat electrical contact is established which will complete a circuit of any type appropriate to the particular device.  
  More particularly, the movable member is springurged to its upper non-operative position and preferably takes the form of a leaf spring whose inherent resilience normally urges it to its upper inoperative position and also maintains the contacting key against the top plate of the housing preparatory to manual actuation. Such leaf spring may be formed from phosphor bronze or other material which exhibits such inherent resilience and at the same time provides an electrical contactor between one end of each leaf spring which is secured to the under surface of the housing and is, for example, electrically connected to a common bus bar that is grounded and also serves as a support for a plurality of the leaf springs in substantially parallel relationship. To minimize construction and assembly costs a plurality of the leaf springs and the supporting bus bar can be fabricated from the same phosphor bronze material through utilization of a simple stamping operation.  
  The free projecting end of each of the leaf springs is, of course, held in its upward inoperative position by the inherent resilience of the material but in accordance with an additional aspect of the present invention, the free projecting end of each leaf spring is also provided with a separate or integrated ferromagnetic portion arranged to underlie a strip of magnetic material in the under surface of the top plate of the housing thus to provide supplemental magnetic restraining forces against depression of the leaf spring in response to manual actuation of the respective key. It will be immediately understood that the inherent resilience of the leaf spring and the supplemental restraining force of the magnet will prevent inadvertent depression of the key and a predetermined force by the operator is necessitated to initiate movement of the leaf spring from its upper non-operative position to its lower operative position. However, once the ferromagnetic portion at the free end of the leaf spring has been physically moved from its contact with the holding magnet, the manual force required for further motion of the leaf spring to its operative, electrical contacting position is substantially reduced. at least until such contacting position has been physically attained whereupon the manual force requisite for further motion of the key again increases.  
  After such operative contact has been made. further key depression will result in slight lateral motion of the contacting free end of the leaf spring since its other end position has been fixed in its contact with the top plate of the housing, and such lateral motion will, in accordance with a particularly important feature of the present invention, provide an automatic cleansing of the electrical contacts thus to preclude failure of successful electrical energization of the appropriate circuit over an extended period of time.  
  Preferably, in accordance with an additional aspect of the present invention, a grid member is supported below the leaf springs adjacent their supported positions for adjustment along the direction of leaf spring projection, thus to vary the point of support of the springs and accordingly their leverage, wherefore a simple variation in the force required to depress one of the actuated keys is readily achieved. Such grid is arranged to underlie the supported ends of all of the leaf springs so that a common variation in the requisite manual forces can be achieved to meet the precise needs of an individual operator. Preferbly, the entire grid is supported in tracks at the side of the top plate of the housing and to assure pressed contact against the supported end of the leaf springs, an additional magnetic strip is embedded in the under surface of the housing and the grid is in turn formed of ferromagnetic material thus to simplify not only its initial fabrication but also to simplify its mounting and assembly in the unit.  
 BRIEF DESCRIPTION OF THE DRAWINGS The stated objective of the invention and the manner in which it is achieved as summarized hereinabove will become more readily understood by a perusal of the following detailed description of the exemplary structure illustrated in the accompanying drawings wherein:  
  FIG. 1 is a top plan view of a keyboard embodying the present invention,  
 FIG. 2 is a veiw of the under surface thereof,  
  FIG. 3 is an enlarged transverse sectional view taken along line 3-3 of FIG. 1.  
  FIGS. 4. S and 6 are transverse sectional views corresponding to FIG. 3 but illustrating the apparatus in different operative dispositions, and  
  FIG. 7 is a graph illustrating the relationship between force and displacement of the keys in the operative functioning of the unit.  
 DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENT OF THE INVENTION With initial reference to FIGS. I and 2 the exemplary apparatus which may constitute acalculator, computer. printer or any other mechanism requiring the selected input of alphanumeric data and related func tional inputs such as for example addition, multiplication. etc.. in the case of a calculator includes a top plate I preferably formed of plastic or other insulating material with a plurality of apertures 12 arranged to movably receive a plurality of keys 14 that can be depressed manually by the operator in his selection of the requisite input data. More particularly, as shown in FlG. 3, the apertures 12 taper outwardly as do the adjoining surfaces of the individual keys. thus to restrict the upward disposition of the keys I4 to the positions illustrated.  
  The keys 14 are also preferably formed of plastic or other insulating material and each key includes a central projection or protuberance 16 in its under surface arranged to contact a movable member I8 whose upper position as illustrated in FIG. 3 constitutes its inoperative position but which is capable of motion downwardly through the positions shown in FIGS. 4 and in response to manual depression of the individual key 14 to its operative position which is illustrated in FIGS. 5 and 6.  
  More particularly, the movable member 18 preferably takes the form of a leaf spring that is centrally engaged by the projection 16 on the individual key 14, one end of the leaf spring being secured to abus bar 20. A plurality of the projecting leaf springs is arranged in parallel and each is secured to the bus bar 20 as best shown in FIG. 2 and adhesively or otherwise secured to the under surface of the top plate of the housing. The leaf springs I8 are preferably formed together with the bus bar in an integrated fashion from phosphor bronze or similar spring material which is both resilient so that the individual leaf springs 18 are held in their upper inoperative dispositions as shown best in FIG. 3 so as to retain the associated keys 14 in their inopera tive raised dispositions. and also is conductive to provide electrical continuity to the integral phosphor bronze bus bar 20 and a connected common electric circuit point (not shown) which in most cases will constitute an electrical ground. The remote free end of each of the leaf springs 18 beyond the point of contact with the projecting portion 16 of the associated key 14 is arranged to contact the under surface of the housing under the natural resilience of the phosphor bronze material but is also preferably provided with a portion 22 formed from ferromagnetic material which will be attracted upwardly to an insulating strip 24 of magnetic tape suitably embedded in the under surface of the top plate 10. Accordingly. a single strip 24 will function to hold the free ends of the leaf springs 18 toward their upper inoperative positions, thus in each case to supplement the restraining force against the depression rcsultant from the inherent resilience of the spring material itself. Accordingly. when an individual key 14 is initially depressed. its downward motion will be restrained both by the resilience of the leaf spring 18 and the holding force of the magnet strip 24 at its extremity. Conse quently the initial force requirement or touch of the operator will be relatively large. thus enabling inadvertent depression of an individual key 14 to be avoided.  
  During such initial depression, the leaf spring 18 will be centrally depressed as best shown in FIG. 4 against a total restraining force illustrated graphically at position A in FIG. 7. Once the magnetic restraining force has been overcome. the leaf spring will quickly move from the FIG. 4 to the FIG. 5 position. the manual force being required dropping considerably as indicated at position B on the graphical representation of FIG. 7. When the position of FIG. 5 has been attained. a gold contact 26 at the free end of the leaf spring 18 engages an underlying contact diagrammatically indicated at 28 and the electrical circuit with such contact 28 is completed thus to provide the operative disposition of the key [4 and associated leaf spring 18 whereat the de sired input is delivered to the apparatus. Once such contact has been established, further motion of the key 14 downwardly will cause an additional flexing of the leaf spring 18 as shown in FIG. 6 and because of the increased resistance resultant from the contact of the free end of the leaf spring 18, the amount of force required for such further depression of the key will increase as indicated at position C in FIG. 7, thus readily indicating to the operator that the requisite electrical contact has been made. As a result of the flexing of the leaf spring 18 as shown in FIG. 6, a departure from a straight line disposition between the point of support of the leaf spring 18 and its end contact 26 is experienced and as a consequence this contact 26 is constrained to move laterally across the contact 28, thus providing a rubbing and cleansing action automatically in response to each contacting operation. As a consequence. cleansing and other maintenance is reduced over extended periods of time and since it is known that the phosphor bronze material of which the leaf springs 18 are composed retains its resilience over extended periods, the entire keyboard operation can be continued over an extended useful life without significant maintenance or repair.  
  It being recognized that the touch&#34; requirements of various operators may. in and of themselves vary, an additional relatively simple mechanism is incorporated in the unit to facilitate adjustment of the force requisite motion achieve depression of an individual key 14 and more particularly to enable simultaneous adjustment of the requisite force for depression of any of the keys so that a consistency in the touch requirements for all keys is achieved. With particular attention to FIGS. 2 and 3, this touch variation is simply achieved by the mounting ofa grid 30 which is arranged to underlie the leaf springs 18 adjacent their points of contact with the supporting integral bus bar 20 and such grid is slidably mounted in tracks 32 adjacent the sides of the top plate 10 for sliding motion in a direction lengthwise of the leaf springs 18, thus to vary the point of support of the leaf springs 18 wherefore their leverage is varied and the force requisite for depression of an individual key 14 is varied as well. To provide such adjustment, a dependent flange at one edge of the grid 30 is provided with a threaded opening engaged by an adjustment screw 32 that projects through the downturned edge of plate for connection at its outer extremity with an adjustment nut 34 whose rotation will effect motion of the entire grid forwardly or rearwardly thus to effect a variation in the touch requirements for all of the keys l4. Since the grid 30 is slidably supported at its edges. in order to assure continuing contact with the leaf springs 18 in the central portion of the housing. the grid 30 is preferably formed from ferromagnetic material and is attracted to the under surface of the housing by additional magnetic strips 36, as best shown in FIG. 3, whose magnetic attraction pulls the adjoining section of the grid upwardly thereagainst accordingly to press the adjacent portion of the leaf spring 18 against the under surface of the housing.  
  It will be apparent that numerous modifications in the specific structure described hereinabove can be envisioned without departing from the spirit of the present invention, and the foregoing description of one embodiment accordingly is to be considered as purely exemplary and not in a limiting sense, and the actual scope of the invention is to be indicated only by a reference to the appended claims.  
 What is claimed is:  
 I. In a keyboard, the combination comprising:  
 a. a plate member,  
 b. a plurality of apertures in said plate member,  
 c. a plurality of elongated spring members,  
 (1. one of said spring members lying under each of said apertures,  
 e. a first end of each of said spring members being fastened to said plate,  
 f. the second end of each of said spring members and said plate having mutually attracting magnetic means thereon whereby said second end is at tracted to and held against said plate.  
 g. the resilience of said spring member biasing said second end toward said plate.  
 h. first contact means on said second end of each of said spring members,  
 i. second contact means located in operative relationship with said first contact means.  
 j. key means in each of said apertures, said key means being adapted to put pressure on said spring means between the ends thereof whereby initial pressure on said key means will flex said spring member and additional pressure will break away said magnetic means and cause said contacts to change their op erativc relationship.  
 2. The keyboard ol&#39;claim 1 wherein each of the elongated spring members is a leaf spring.  
  3. The keyboard of claim 1 wherein pressure on said key means causes said contact means to initially contact each other and whereby further pressure on said key means causes said contact means to wipe across each other.  
  4. The keyboard of claim 1 wherein a plurality of said elongated spring members are attached to and formed integral with a bus bar member.