Abstract:
An electronic computer keyboard is constructed to provide the minimum keystroke resistance sufficient to prevent accidental switch closures otherwise resulting from the weight of the operator&#39;s fingers resting on the keys. This forces the operator to move his or her hands over the keyboard with locked wrists. It also eliminates the need of the operator to hold his or her hands up to prevent inadvertent key depressions thereby reducing stress and fatigue on the operator&#39;s shoulders, forearms, wrists and hands.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation-in-part of U.S. patent application Ser. No. 08/894,112 filed Aug. 12, 1997 (abandoned), which is a 35 U.S.C. §371 filing of PCT/US96/18835 filed Dec. 13, 1996, which in turn claims priority of U.S. patent application Ser. No. 08/572,091 filed Dec. 14, 1995 (now U.S. Pat. No. 5,676,476). 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates generally to keyboards for computers, electric typewriters and similar manual data input devices utilizing the standard QWERTY key format, and more particularly, to an electronic computer keyboard with enhanced ergonomic properties for preventing and/or alleviating injury to the forearms, wrists and hands of an operator normally associated with repetitive use. 
     Conventional keyboards for computers, typewriters, or similar machines typically have a set of keys arranged substantially in a single plane that may be flat or slightly tilted toward the operator. The standard key arrangement used by a majority of keyboard manufacturers throughout the world has at least three parallel rows of ten or more keys. The keys of one row are staggered relative to the keys of an adjacent row. The keys typically include the twenty-six letter keys arranged in the standard QWERTY format and four punctuation keys. In addition to the alphabetic keys, conventional keyboards specifically designed for use with computers also have numeric keys and function keys which are typically located above, below, or on one or both sides of the alphabetic keys. The function keys typically include, for example, the tab, shift, and return keys as well as the alt, control, and option keys. During typing, the operator&#39;s forearms are positioned at inwardly directed angles from the operator&#39;s sides toward the keyboard, with the palms down and the hands generally flat. The wrists are bent and the hands are angled outwardly relative to the forearms in order to align the operator&#39;s fingers in directions running from the front to the back of the keyboard. The operator repeatedly pivots his or her hands at the wrist joints side-to-side over the keyboard in order to select and actuate the individual keys. 
     Adverse physical conditions may arise in the operator&#39;s wrists, hands and fingers resulting from the kind of repetitive motions associated with typing on a conventional electronic computer keyboard, particularly for long periods on any given day or successive days. Such adverse conditions are compounded by the conventional design of conventional electronic keyboards which encourages the side-to-side flexing of the operator&#39;s wrists, hands and fingers into particularly awkward and unnatural angles for prolonged periods of time. Typing injuries may fall into one of a few overlapping categories: repetitive stress disorder, repetitive motion injury, cumulative trauma disorder, and carpal tunnel syndrome. These conditions often require medical attention and, in severe cases, the worker may be unable to perform normal work functions. The cost in human suffering, and on-going medical expenses may be severe. 
     Various wrist/arm supports, keyboard geometries and positionable desktop surfaces for preventing injury to keyboard operators have been patented in the United States. Some of these patented devices have met with limited commercial success. However, none of them has been completely successful in preventing injury to the forearms, wrists and hands of an electronic keyboard operator. 
     Before the advent of modern electronic computer keyboards, it was relatively rare for full time operators of manual (non-electric) typewriters to experience injury to their forearms, wrists or hands, even if they typed forty hours per week. With the advent of modern electronic computer keyboards, particularly those associated with personal computers, a common design objective has been to provide minimal keystroke length and minimal keystroke resistance. The apparent objective has been to make typing and data entry easier and faster. The primary constraint on minimizing both keystroke length and keyboard keystroke resistance has been the fact that both need to be significant enough to prevent spurious key switch closures. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is the object of the present invention to provide a method that uses an electronic computer keyboard with enhanced ergonomic properties to prevent and/or alleviate injury to the forearms, wrists and/or hands of an operator. 
     According to my invention an electronic computer keyboard is constructed to provide the minimum keystroke resistance sufficient to prevent accidental switch closures otherwise resulting from the weight of the operator&#39;s fingers resting on the keys. This forces the operator to move his or her hands over the keyboard with locked wrists. It also eliminates the need for the operator to hold his or her hands up to prevent inadvertent key depressions thereby reducing stress and fatigue on the operator&#39;s shoulders, forearms, wrists and hands. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is simplified plan view illustrating an operator&#39;s left forearm, wrist and hand actuating a conventional electronic computer keyboard. The hand is shown in two different positions in sold lines and phantom lines. 
     FIG. 2 is an enlarged diagrammatic vertical sectional view of a portion of an electronic computer keyboard that may be utilized to carry out the method of the present invention. 
     FIG. 3 is a simplified plan view similar to FIG. 1 illustrating an operator&#39;s left forearm, wrist and hand actuating an electronic computer keyboard that may be utilized to carry out the method of the present invention. The hand, wrist and forearm are shown in a first position in solid lines and in a second position in phantom lines. 
     FIG. 4 is an enlarged partially exploded and partially vertical sectional view through a portion of an electronic computer keyboard illustrating the manner in which its individual key support assemblies can be retrofitted with elastomeric booster springs to increase keystroke resistance. 
     FIG. 5 is a top plan view of the key support assembly illustrated in FIG.  4 . 
     FIG. 6 is a bottom plan view of the key illustrated in FIG.  4 . 
     FIG. 7 is a perspective view of the elastomeric booster spring illustrated in FIG. 4 showing its rib receiving slits. 
     FIG. 8 is side elevation view of the booster spring of FIG.  7 . 
     FIG. 9 is a vertical sectional view through the key and elastomeric booster spring of FIG. 4 showing, the manner in which they mate. The associated key support assembly is shown in phantom lines. 
     FIG. 10 is a plan view of an elastomeric template that may be used to simultaneously retrofit multiple keys of a conventional electronic computer keyboard. 
     FIG. 11 is an enlarged vertical sectional view of the elastomeric template taken along line  11 — 11  of FIG.  10 . 
     FIG. 12 is a fragmentary perspective view of a plurality of cylindrical booster springs made of an elastomeric material interconnected by an elastomeric tree structure. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Conventional electronic computer keyboards have keys that can be depressed with less than seventy grams of force and with less than five millimeters of keystroke length. The problem with this type of “light touch” design is that an operator tends to angle his or her wrists back and forth as much as thirty degrees in reaching for various keys. Furthermore, the weight of an operator&#39;s fingers combined with the natural downward flexing of the fingers is usually sufficient to depress a key. Therefore, the operator induces stress and fatigue in his or here wrists supporting the hands so that the fingers do not inadvertently depress the keys. If greater keystroke resistance and/or keystroke length were required in order to enter a particular letter, numeral, symbol or command, the operator would naturally tend to lock his or her wrists and move the hands over the keys, eliminating the severe wrist flexure. While this type of movement requires angling of the forearms by pivoting the shoulder, such angling is minimal, for example two to five degrees, and does not lead to injuries in the arms or shoulders. This may be due to the fact that the ball and socket construction of the shoulder joint is more conducive or natural to this type of side-to-side movement than the wrist joint. 
     Referring to FIG. 1, a conventional electronic computer keyboard KB is illustrated which includes a first plurality of keys, including keys K 1  and K 2 , arranged in the standard QWERTY key format, and a second plurality of keys K 3  arranged to the side normally including numeral keys and command keys. The conventional electronic computer keyboard KB also includes a space bar (not illustrated) adjacent the lower edge, function keys (not illustrated) adjacent the upper edge and other command keys (not illustrated). The conventional electronic computer keyboard KB is constructed in well known fashion and includes an outer frame, a plurality of keys each having guide posts received in corresponding guide mechanisms mounted in the frame. Springs normally surround the guide posts and bias the keys upwardly. The lower ends of the guide posts are located above corresponding switches which may have a laminated membrane-type construction, for example. Typically the springs are selected so that the keystroke resistance force is approximately seventy grams. This is the average approximate force required to be applied by the operator&#39;s fingers to depress a key sufficiently to cause the lower end of its associated guide post to actuate the corresponding switch and close electrical contacts therein. Electrical signals are generated and recognized by the mother board of the personal computer as indicating that the operator has depressed a particular key at a particular moment. Normally the guide post associated with each key and the guide mechanism associated with each guide post are configured so that the key travels less than five millimeters between its uppermost and lowermost positions. The keystroke is thus the distance a key travels from its raised at rest position to its fully depressed position in which the lower end of its guide post actuates the associated electrical switch. 
     Referring still to FIG. 1, the conventional electronic computer keyboard KB has such a light touch, i.e. requires so little force and/or so little keystroke travel to actuate the associated switch, that it is only necessary for the operator&#39;s hand H to shift angularly between the position P 1  shown in solid lines in FIG.  1  and the position P 2  shown in phantom lines in FIG.  1 . This causes the operator&#39;s wrist W to move through a substantial angle Θ which can be as much as thirty degrees. When the operator&#39;s hand H moves between the positions P 1  and P 2 , his or her forearm F remains more or less stationary. The type of hand and wrist movement illustrated in FIG. 1 can occur, for example, when the user first depresses one key of the set K 1  with his or her ring finger and then moves to depress one key of the set K 2  with the same finger. It is the back and forth repetitive movement of the operator&#39;s wrist W through the angle Θ that may lead to physical injury. If the operator rests his or her hands on the keys of the keyboard KB, the weight of his/her fingers will depress the keys and close the associated switches. 
     Referring to FIG. 2, in accordance with my invention, an electronic computer keyboard  10  includes a plurality of keys  14 . Each key  14  is connected to or formed with, such as by injection molding, a downwardly extending guide post  16 . Only the center key  14  is shown with its guide post  16  in FIG.  2 . The electronic computer keyboard  10  further includes one or more vertically spaced guide plates  18  having holes for slidably receiving the guide post  16  of each of the keys  14 . Only one hole is shown in the guide plate  18  for the sake of clarity. For simplicity, only the structure associated with the center key  14  will be described. It will be understood that all the other keys  14  have similar guide posts, guide mechanisms and associated switches. 
     The guide post  16  and guide plate  18  form a guide mechanism for permitting vertical reciprocal movement of the key  14 . Beneath the lower end of the guide post  16  is a laminated membrane-type switch assembly  20  including a plurality of electrical switches. Each of these switches is located directly beneath the curved lower end of a corresponding guide post  16 . A coil spring  22  surrounds the guide post  16  of the key  14 . The spring  22  is compressed between the key  14  and the guide plate  18 . A retainer  24  surrounds the lower end of the guide post  16  to prevent the key  14  from falling out of the keyboard  10 . The foregoing components are all mounted in, and supported by, a surrounding plastic frame illustrated diagrammatically by phantom line  26 . The key  14  is normally biased upwardly to its at rest position by the spring  22 . The key  14  can be pushed downwardly by an operator&#39;s finger through a predetermined keystroke length SL to cause the lower rounded end of the guide post  16  to engage and close the associated electrical switch in the laminated switch assembly  20 . 
     In accordance with the present invention, the compressive strength of the spring  22  is selected to provide the minimum keystroke resistance sufficient to prevent accidental switch closures from the weight of the operator&#39;s fingers resting on the alphanumeric keys. This keystroke resistence will typically be a minimum of about seventy grams. The keystroke resistance is the amount of force that must be applied by an operator&#39;s finger in a downward direction to cause the lower end of the guide post  16  to close the associated switch in the switch assembly  20 . Also, in accordance with the present invention, the keystroke length SL may also be selected to achieve therapeutic results in combination with the increase in keystroke resistance. A keystroke length SL of greater than about five millimeters, and more preferably, greater than about ten millimeters may be beneficial. The keystroke length SL is defined as the distance that the key  14  must travel from its uppermost, at rest position, to its lowermost position in which the lower end of the guide post  16  engages and closes the corresponding switch in the switch assembly  20 . 
     The effective upper limit for both the keystroke resistance and keystroke length would in all likelihood be those exhibited by conventional, non-electric typewriters, such as those sold for many years in the United States prior to 1960 under the Trademarks UNDERWOOD, SMITH CORONA and others. Most electronic computer keyboard operators would probably dislike a keystroke resistance higher than three hundred grams. A preferred range would be between seventy grams and two-hundred twenty grams, and more preferably, between about ninety grams and one hundred and twenty grams. Of course large keys, such as the space bar, preferably have a higher keystroke resistance than that of the alphanumeric keys since the weight of more than one finger will normally rest on the same. 
     FIG. 3 illustrates the movement of the operator&#39;s hand H, wrist W and forearm F when he or she uses the electronic computer keyboard apparatus  10  constructed in order to carry out the method of my invention. More particularly, when the operator wishes to depress the far right key of the set K 1  with his or her ring finger, and then depress one of the keys of the set K 2  with his or her middle finger, it is necessary for the operator to lock his or her wrist W. In FIG. 3, the initial position of the operator&#39;s hand H, wrist W and forearm F is shown in solid lines. When moving between the keys K 1  and the keys K 2 , the operator&#39;s hand, wrist and forearm move from the position P 1  shown in solid lines to the position P 3  shown in phantom lines. The important thing to note in this operation is that the operator&#39;s wrist is locked and no longer swings through the angle Θ. Instead, the operator&#39;s forearm F moves through a much smaller angle a typically less than ten degrees. Because the operator has locked his or her wrist, the tendency to develop an injury to the shoulders, forearms, wrists or hands from repetitive movements associated with the operation of the electronic computer keyboard  10  is greatly reduced when the keyboard is operated for an extended period to enter text and/or numbers into an application on a computer associated with the keyboard compared to a conventional electronic keyboard KB (FIG.  1 ). The extended period could be several hours in a given day over weeks or months. 
     FIGS. 4-9 illustrate another electronic computer keyboard construction which is particularly suited to retrofitting existing electronic computer keyboards to provide increased keystroke resistance. All of its keys, switches and guide mechanisms are similar so only one will be described. Each key  14  is made of injection molded plastic and includes a downwardly extending cylinder  28  (FIG. 6) having a centrally located crisscross shaped hole  30 . The upper end  16   a  (FIG. 4) of the guidepost  16  has a crisscross shape so that it can be snugly received into the hole  30  in the cylinder  28 . A PC board  34  (FIG. 4) supports an upwardly opening box-shaped receptacle  36 . The receptacle  36  has a downwardly extending projection  38  which is received in a locating aperture  40  in the PC board  34 . Inside the receptacle  36  is a centrally located vertical guide tube  42 . The lower half of the coil spring  22  surrounds the guide tube  42 . 
     The guide post  16  (FIG. 4) has a main body  16   b  from which projects a hook shaped actuator  16   c . The guide post  16  has a cylindrical, rounded lower segment  16   d  that slides upwardly and downwardly within the guide tube  42 . During this motion, the actuator  16   c  moves an inverted L-shaped Copper switch element  44  into and out of contact with U-shaped Copper switch element  46 . This makes and breaks a circuit connection. The switch elements  44  and  46  are connected through the receptacle  36  to circuit traces (not illustrated) on the upper surface of the PC board  34 . 
     A key support assembly  48  (FIGS. 4,  5  and  9 ) is mounted over the top of the receptacle  36  and held in place by four downwardly extending tabs  50 . The tabs  50  have projections  52  which seat in corresponding detents (not illustrated) formed in opposite vertical sidewalls of the receptacle  36 . The key support assembly  48  has an aperture  54  which extends vertically therethrough. The guide post  16  reciprocates upwardly and downwardly through the aperture  54  of the key support assembly  48 . A rectangular elastomeric booster spring  56  is seated between the upper generally horizontal surface  48   a  of the key support assembly  48  and the underside  14   a  (FIG. 6) of the key  14 . In this embodiment the coil spring  22  serves as a base spring and the elastomeric spring  56  serves as a booster spring. Together they provide the keystroke resistance. The elastomeric booster spring  56  is made of a material having a suitable durometer or hardness necessary to achieve the keystroke resistance in the ranges identified above. By way of example, suitable elastomeric materials include polyurethane, polypropylene, polyethylene, and various blends of these materials. Of course, synthetic and natural rubbers could also be utilized. The foregoing list of materials is meant to be exemplary, and not exclusive. The booster spring  56  has an overall rectangular configuration including four sidewalls  56   a ,  56   b ,  56   c , and  56   d . The sidewalls  56   a  and  56   d  have inclined upper edges to ensure proper engagement with the underside  14   a  of the key  14  which is typically angled relative to the upper surface  48   a  of the key support assembly  48 . Each of the sidewalls has an upwardly opening vertical slit  58 . The slits received corresponding downwardly extending ribs  60  (FIG. 6) formed on the underside  14   a  of the key  14 . In this manner, the booster spring  56  is centrally located in position between the spring  14  and the underlying key support assembly  48 . 
     The electronic computer keyboard construction of my invention illustrated in FIGS. 4-9 is particularly adapted to retrofitting existing electronic computer keyboards. Sets of elastomeric booster springs can be sold in packages at retail computer outlets. Individual computer owners can remove the keys from their electronic computer keyboards relatively easily, insert the booster springs in position, and replace the keys. Alternatively, this could be done as service by a retail computer outlet. The booster springs would be available in range of durometers so that a user could select a particular keystroke resistance fitting his or her particularized needs. Alternatively, the booster springs could be installed by original equipment manufacturers (OEMs) of electronic computer keyboards. 
     FIGS. 10 and 11 illustrate an alternate way to modify existing electronic computer keyboards in order to perform the method of the present invention. An elastomeric template  60  is injection molded, or otherwise formed as a single unitary piece of elastomeric material having a waffle-like configuration. More particularly, as best seen in FIG. 11, a plurality of individual booster spring elements  62  are connected to one another in spaced apart, uniform fashion. The upper portion  62   a  (FIG. 11) of each booster spring element  62  has the same configuration as the booster spring  56  (FIGS  7  and  8 ). The lower portion  62   b  of each booster spring element  62  is flared in order to fit around and enclose the corresponding key support assembly  48  (FIG.  9 ). It will thus be understood that the template  60  may be utilized by OEMs during the fabrication of electronic computer keyboards to rapidly provide the required keystroke resistance for each of the keys, without the necessity of installing a large number of individual booster springs. 
     FIG. 12 is a fragmentary perspective view of a still further way to modify existing electronic computer keyboards so that they can be used to perform my method. A lattice structure  64  includes a plurality of cylindrical booster springs  66  made of an elastomeric material interconnected by a tree structure in the form of a plurality of elastomeric ribs  68 . The lattice structure can be molded as one integral unit. The spacing of the cylindrical booster springs  66  is determined by the lengths of the row-oriented and column-oriented ribs  68 . The ribs  68  are connected to the cylindrical booster springs  66  via L-shaped elastomeric connectors  70 . This permits the booster springs  66  to sit on top of corresponding key support assemblies  48 . The connectors  70  extend downwardly around the sides of the key support assemblies  48 . The ribs  68  therefore extend generally horizontally at a lower level between the keys  14  adjacent and parallel to the guide plate  18  (FIGS.  4  and  5 ). The lattice structure  64  is particularly suited for OEM manufacturing. 
     The present invention may be modified in both arrangement and detail. For example, benefits may be achieved by either increasing the keystroke resistance as indicated, increasing keystroke length as indicated, or by increasing both. Multiple springs can be used to increase the keystroke resistance of the wide space bar. The coil springs in the keyboard could be completely replaced with elastomeric springs, or the increased keystroke resistance could come from a combination of the existing coil springs supplemented by elastomeric booster springs. The booster springs could also be coil or other metal type springs. A combination of base springs and booster springs, both made of suitable elastomeric material could also be used. The present invention can either be designed into the electronic keyboards themselves by OEMs or can be accomplished by using a retrofit kit consisting of individual booster springs, elastomeric templates or some other convenient way of increasing the keystroke resistance into the ranges identified, without impairing switch closure capability. Versions of the computer keyboard could be produced with higher keystroke resistance for male users and a somewhat lesser keystroke resistance for female users. Therefore, the protection afforded the present invention should only be limited in accordance with the following claims.