Abstract:
The present invention provides a musical instrument manual having keys that may be made of a material subject to warping and twisting, such as wood. A distal flexible suspension allows angular shifting of the distal end of each key of the manual to accomodate key warping. The flexible suspension enables angular displacement of the key lever about its distal end perpendicular to the plane of the playing surface of the key to allow the key to be played. The flexible suspension elastically opposes twisting of the key lever relative to the key bed.

Description:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     The present invention was not developed with the use of any Federal Funds, but was developed independently by the inventor. 
     BACKGROUND OF THE INVENTION 
     For centuries, keys for musical instruments such as organs, pianos, harpsichords, and the like have been made of wood. Wood has many desirable, but also some undesirable, properties. Responsive to temperature and humidity, wood can shrink or expand, warp, and twist. Long before the advent of modern precision machinery, musical instrument manuals required precise fitting of parts to avoid malfunctions. Ingenious traditional methods for building manuals have developed over centuries to address both the properties of wood and the lack of precision tools of times past. Traditional manual building is labor-intensive and requires superb craftsmanship. Since the 1930&#39;s, demand for mass-produced instruments has induced inventors to develop mass-producible manual designs. Most modern manuals largely comprise components made metal and plastic, both of which are more stable than wood, can be stamped or molded, and can be assembled using unskilled or semi-skilled labor. 
     Since pianos and harpsichords are generally mechanically operated, their key design is constrained by the interactions between keys and other mechanical parts. Though tracker (mechanically operated) organs are still built, the keys of most organs now operate electrically. For the last hundred years, despite many being fitted with electrical contacts, most organ keys have been mechanically long from their playing surfaces to the far (distal) ends of their key levers. Key lengths of eighteen inches or more have not been uncommon. Over the years, manuals for organs, and now for electronic keyboards, have been made more compact, with shorter keys. Today&#39;s keyboards typically comprise molded plastic key assemblies wherein the distance from the front of their playing surface to their integrally molded plastic spring is usually about six inches. Such manuals are economical, but their short effective-pivot radius tends to induce or aggravate carpal tunnel problems. Traditional manuals with long effective-pivot radii are easier on players&#39; wrists. This consideration, along with adherence to traditions, underlies the preference of many organists for traditional wooden manuals. 
     As will be shown below, much effort has been expended and great ingenuity applied in the last century to avoid making wooden keys for manuals. Comparatively little work has been done to use modern tools and materials to overcome, rather than to avoid, the difficulties of making wooden keys. The present invention departs from most modern work by improving the manufacturability of wooden manuals while preserving and even improving their traditional function. 
     DESCRIPTION OF THE PRIOR ART 
     Traditional manuals for organs have been built with keys much like those of pianos. Proximal to the musician are key heads, often made of wood with integral key levers that extend to the distal ends of the keys. The heads of “natural” keys for playing whole tones are usually about two inches long and about seven-eighths of an inch wide, covered with a playing surface, traditionally ivory, now usually plastic, bone, or other substitute material. The heads of the “sharp” keys for playing semitones are usually about three and one-half inches long and about seven-sixteenths of an inch wide. The playing surface of the “sharps” is elevated above that of the “naturals”, the elevated portion being traditionally made of ebony, but now usually made of plastic, or of wood dyed black. Both “natural” and “sharp” key levers traditionally move vertically on two pins. Proximally, each key is partially penetrated from below by a “front-rail pin” that permits vertical motion while keeping the key head in correct lateral position and preventing twisting thereof. Distally, each key lever is fully penetrated by a “balance rail pin” that acts as a pivot about which the key is free to rotate through a small angle in both a vertical plane and a horizontal plane. The fact that two pins mechanically constrain traditional wooden keys in the plane perpendicular to the key playing surface and parallel to the key lever longitudinal axis engenders difficulties in the manufacture of traditional wooden manuals, as will be explained in more detail below. Traditional manuals are labor intensive to manufacture and require highly skilled laborers. The cost of traditional methods motivated a modern movement toward metal and plastic keys. 
     U.S. Pat. No. 2,117,002 is an early example of the movement toward metal and plastic keys. Between column 1, line 55 and column 2, line 8, Hammond summarizes the problems cited above and, the motivation for his invention. Shortly thereafter, Stevens, assignor to the Hammond Organ Company, invented the key described in U.S. Pat. No. 2,260,412 which key design appears to have been the basis for the keys of the famous Hammond B3, and many other successful Hammond organ models built into the 1960&#39;s. Later Hammond organs, such as the Regent, Colonnade, and others, used a flat, digitated, leaf spring clamped to a frame, to each digit of which a thin steel key lever was riveted by two rivets. The key lever was perforated by two holes, into which were melted the ends of plastic bosses protruding from the bottoms of plastic key heads. These keys are not as durable as keys according to U.S. Pat. No. 2,260,412. Hammond keys, and those of many manufacturers of the same era, had metal key levers. Metal lever keys were provided with either pivots or springs to enable vertical motion, but not being subject to warping and twisting like wooden keys, did not need and were not provided with compliance in a horizontal plane. 
     Recently, plastic keys with integrally molded head, levers, plastic key springs, and distal mounts have become common. U.S. Pat. No. 6,051,768 exemplifies such key design. Due to the relative stability of plastic compared to wood and the short length of keys, such keys need no significant compliance in a horizontal plane. Such keys are inexpensive, but have proven prone to breakage of the integrally molded plastic spring. Also being short from playing surface to pivot, short keys can be injurious to players&#39; wrists. 
     Despite the widespread use of metal and plastic keys in consumer goods such as electronic keyboards, most professional organists prefer the touch of manuals with wooden keys, and wooden key manuals still command a premium price. 
     BRIEF DESCRIPTION OF THE INVENTION 
     The present invention provides a manual key fitted with a flexible distal suspension that provides angular compliance in the plane of the playing surface of the key to accommodate key lever warping, and permits vertical motion to allow the key to be played in the customary manner. The flexible suspension at the distal end of the key allows the key lever to twist about its longitudinal axis without transmitting to a front-rail pin forces sufficient to bind the key while opposing excessive twisting of the key lever. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a prior art wooden manual key with pins and key bed. 
         FIG. 1A  shows details of the connection between a prior art key and its balance-rail pin. 
         FIG. 2  shows a top view of a left-most octave of an organ manual according to the present invention. 
         FIG. 3  shows a side view of a manual key according to the present invention with a front rail pin and key bed. 
         FIG. 4  shows a top view of a length of flexible suspension for keys according to the present invention. 
         FIG. 5  shows a top view of a single-key flexible suspension according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIG. 1 , there is depicted a traditional manual key  100  connected to a key bed comprising a front rail  110  and a balance pin rail  101 . Key  100  is fully penetrated by a balance pin  102  and partially penetrated by a front rail pin  31 . Key  100  rotates in a vertical plane about balance pin  102 , which allows key  100  to be played in the customary manner. Key  100  also may rotate horizontally through a small angle about balance pin  102  to accommodate key warping. Key  100  is provided with a playing surface  21 , a return spring  33 , and a restricting rod  34  with a nut  35  to restrict and adjust vertical travel of playing surface  21 . Key is partially penetrated by a paddle shaped front rail pin  31 . A felt washer  104  prevents noisy operation of key  100 . Key  100  is partially penetrated by a milled slot  32  in which front rail pin  31  operates and another milled slot  103  in which balance rail pin  102  operates. If these two milled slots could always fit tightly, but move smoothly, over their respective pins, this traditional construction would be ideal. However, this ideal condition is difficult to attain. Firstly, were the slots of key  100  are precisely milled to fit pins  31  and  102  tightly, should the key twist it would become mechanically over-constrained and would bind. Were the slots milled to fit loosely, key  100  might not bind but would be noisy in operation and might rotate along its longitudinal axis allowing unsightly turning of the keys. Additionally, it is not practical to hold precise tolerances of slot widths in wood. 
       FIG. 1A  shows how traditional manual construction partially solves the problem cited for  FIG. 1 . Slot  103  in key  100  is lined with bushing cloth  106 , a woven fabric with a texture somewhat like felt and somewhat like velvet. Slot  32  is “bushed” in the same manner. The “bushings” thus formed restrict lateral head play and twisting of key  100 . Since both pins  102  and  31  restrict rotation of key  100  around its longitudinal axis, key  100  will bind if the bushings are too tight, or be loose if the bushings are too loose. The slots  103  and  32  in the key  100  must be precisely milled to avoid both looseness and lateral misalignment of keys. The gluing of bushing cloth  106  is a labor-intensive operation. Bushing cloth has a tendency to compress and take a set like felt, so if a key lever twists moderately, with sufficient use its bushings tend to conform to the twist. Though bushing cloth tends to conform by taking a set, it is not particularly elastic or resilient. For this reason, variety of thicknesses of bushing cloth are customarily supplied to accommodate imprecise milling of slots and, for repairs, worn slots. Occasionally, too thick a bushing cloth is applied, and “key easing pliers” must be used to compress the bushing to keep keys from sticking. Bushings tend to be tight initially, and loosen as they wear, requiring occasional re-bushing of a manual, an expensive operation. Moisture or corrosive environment tends to corrode pins. Corroded pins wear cloth bushings quickly. Despite these difficulties, traditional manual design has the best available solution for making manuals wooden keys that tend to warp and even to twist. Balance rail pin  102  is usually round in cross section. Thus, if a key  100  warps, it merely bends, and its distal portion merely rotates slightly on its balance rail pin  102 . If key  100  does not warp enough to interfere with an adjacent key, no harm is done. The slot for front rail pin  31  is less critical than balance rail slot  103 . Front rail pins are usually paddle shaped, and by turning them about their longitudinal axis they can be tightened or loosened in their bushings. The traditional construction of this figure is partial solution that attempts to address problem engendered by the mechanical over-constraint caused by two parallel rigid pins penetrating a single member that can twist. Key bushings provide little elasticity but do provide a modicum of compliance which allow this partial solution to work properly most of the time if sufficient craftsmanship is expended. The fundamental problem whereby mechanical over-constraint can bind twisted keys remains unsolved. 
       FIG. 2 . shows a top view of the left-most octave of a manual according an embodiment of the present invention. A rear rail  11  is shown at the distal ends of “natural” keys  20  and “sharp” keys  22 , both preferably made of basswood, pine, or paulownia wood. At the left is a cheek  10  that customarily connects a balance rail, or in this embodiment rear rail  11 , to a front rail not shown in this figure. Each natural key comprises a head portion  20 A at its proximal end and a lever portion  20 B. The head and lever portions may be made of a single piece of material or of separate pieces. For example, a key  20  might be cut from a single piece of wood or might have a plastic or wooden head  20 A and a wooden lever  20 B. The head of each “natural” key is often covered with a playing surface  21 , in modern times typically made of light colored plastic. Each “sharp” key also has a playing surface  23 , typically elevated above the playing surfaces of the natural keys and, in modern times typically made of black plastic. Each key,  20  or  22 , is penetrated by a screw  24 , the head of which is visible in this figure, and about which each such key is free to shift pivotally to accomodate warping of the key. In this embodiment each key,  20  or  22 , is slotted horizontally at its distal end, as indicated by dashed lines. Each screw  24  not only penetrates a key  20  or  22  but also penetrates a flexible suspension  14  which in this embodiment is digitated, partially cut into “fingers”, as will be shown below in  FIG. 4 . Flexible suspension  14  is attached by screws  15  to an angle section  12 , in this embodiment made of aluminum. Angle section  12  is attached to rear rail  11  by screws  13 . In this embodiment each key  20  or  22  is free to shift angularly about the pivot provided by its screw  24  while flexible suspension  14  remains fixed, save that flexure of the fingers thereof, shown below in  FIG. 4 , allow the keys  20  and  22  to rotate vertically through a small angle so that they may be played in the customary manner. Though flexible suspension  14  is shown in this figure engaging one octave of twelve keys  20  or  22 , it made be made in any desired length to engage any number of keys  20  or  22 . For example flexible suspension  14  might be made to engage all sixty-one keys of a typical organ manual, or even eighty-eight keys for an electronic piano manual. Flexible suspension  14  is preferably made of 3/32″ thick polypropylene. Flexible suspension  14  may also be made of metal to practice this invention, in which case protective washers might be needed in the slots of keys  20  and  22  to prevent them from being abraded. In the present embodiment flexible suspension  14 , being made of polypropylene, provides little return force for keys  20  and  22 . If metal, for example spring steel, is used for flexible suspension  14 , its thickness may be so chosen to provide the necessary return force for keys  20  or  22 , in which case return spring  33  of  FIG. 3  may be omitted. Common plastic hinges, so called “living hinges”, are customarily made by molding in a trench at their bend line at a specified temperature, followed by a prescribed flexure protocol while still warm. Most “living hinges” with trenches molded in are intended to flex between ninety and near three-hundred-sixty degrees. When digitated as is flexible suspension  14 , such hinges proved so flimsy as to provide far too little elastic resistance to twisting along the longitudinal axis of a key  20  or  22 . Angular movement a key  20  or  22 , when played, between one and two degrees, requires flexible suspension  14  to flex but very little. Providing sufficient torsional resistance to keep a key  20  or  22  straight requires far more torsional resistance than is provided by a typical “living hinge”. Since no data on the use of polypropylene without a molded in trench was available, a polypropylene flexible suspension  14 , was made without the usual and prescribed molded in trench. That flexible suspension  14 , tested in this application, endured ten-million cycles of flexure without detectable degradation, a figure that exceeds the durability of the traditional balance pin and bushing arrangement of  FIGS. 1 and 1A . Inasmuch as the polypropylene is also inexpensive, lightweight, and easy to work, it is preferred for the flexible suspension  14 , though other plastics, or metal, may be used to practice this invention. An unlikely material, steel boning, used in the manufacture of corsets, has also been found to work as a flexible suspension to practice this invention. Steel boning has flexibility and elasticity in two planes, is relatively incompressible along its longitudinal axis, and is elastic in torsion about the same axis. A flexible suspension of steel boning needs no pivot screw like screw  24 , but is not preferred because attaching it to keys  20  or  22  and to a back rail  11  is inconvenient. 
     Unlike the traditional key of  FIG. 1 , each key  20  or  22  of  FIGS. 2 and 3  is rigidly constrained by only its front rail pin  31 , of  FIG. 3  below. Whether flexible suspension  14  is made of plastic or metal, it provides sufficient resistance to twisting to prevent looseness or unsightly positioning of keys, but is sufficiently elastic to allow keys  20  or  21  to move vertically on their front rail pins  31  without binding. Unlike prior art keys of metal or plastic which, being made of relatively stable materials, require little or no angular compliance along the plane of the key playing surface, keys  20  or  22  are angularly free to shift around either screw  24 , or screw  15  for the flexible suspension of  FIG. 5  below, to accomodate key lever warping. 
       FIG. 3  shows, in side view, a “natural” key  20  having a playing surface  21 . In this figure front rail  30  is made of wood with a separate aluminum z-section  36  arranged with restraining rod  34 , nut  35 , and return spring  33 . This difference from the prior art  FIG. 1  is simply a matter of convenience, and the embodiment of the front rail assembly of this figure could have been made just as in  FIG. 1  without any effect on the present invention. Front rail pin  31  and slot  32  correspond identically with the like-named parts of  FIG. 1 . Cheek  10  is here seen from a different angle than in  FIG. 2 . Now let us examine the distal end of key  20 . Here we see that screw  24  penetrates key  20 . We see a slot  19  in which lies a finger of flexible suspension  14 . Screw  24  lightly clamps flexible suspension  14  in slot  19 . Though lightly clamped, key  20  or  22  is free to shift angularly about screw  24  to accomodate warping of the key lever. Here we see angle section  12  and screws  15  and  13  in profile connecting key  20  to rear rail  11 . It is equally possible to practice this invention without angle section  12  by forming a step on or in rear rail  12  into which screws  15  may be driven. As z-section  36  shows, there are many equivalent ways to make a key bed. Front rail  30  and rear rail  11  can be made of metal, in which case front rail pins  31  can be replaced by such guides as are common in metal and plastic manuals, all while practicing the present invention. 
       FIG. 4  shows flexible suspension  14  in top view. Holes  16  are provided for screws  15  of  FIG. 3 . Holes  17  are provided for screws  24  of  FIGS. 2 and 3 . Slots  25  separate fingers  26  to allow each keys  20  or  22  of  FIG. 2  to move independently of adjacent keys. Flexible suspension  14  may be made of length to engage a single octave of twelve keys as shown in  FIG. 2 , as a single piece engaging all the keys of the manual, or as a piece or pieces engaging other numbers of keys  20  and  22  as desired. 
       FIG. 5  shows an alternative flexible suspension  18  made to serve a single key  20  or  22  of  FIG. 2 . Flexible suspension  18  is penetrated by two holes  17  for two screws  24  for attachment to a key  20  or  22  of  FIG. 2 . Flexible suspension  18  is also penetrated by a hole  16  for a screw  15  for attachment to angle section  12 . In  FIG. 2 , each key  20  or  22  could angularly shift about screw  24 . When flexible suspension  18  is used, each key  20  or  22  and flexible suspension  18  can angularly shift about screw  15 . For a conventional organ manual of sixty-one keys, sixty-one flexible suspensions  18  may be used to practice this invention. Alternatively a typical organ manual of sixty-one keys might use five octave-length flexible suspensions  14  as shown in  FIG. 2  with flexible suspension  18  engaging the sixty-first key.