Abstract:
Composite or plastic molded articles used in a grand piano piano action. The articles make up a piano action with less dynamic mass which is, thus, more responsive. In addition, the new action provides the extremely valuable collateral benefits of increased efficiency of manufacture and maintenance. The invention also provides the capability to achieve true half stroke design in both the sharp and white keys at the same time. Additionally, the application discloses a universal composite grand piano piano action that is capable of being installed into any brand of grand piano.

Description:
BACKGROUND OF INVENTION 
       [0001]    This invention relates to key operated percussion devices such as grand pianos and, more specifically, to the “actions” of such devices. A piano action transmits motion from the pianist&#39;s fingers to the piano strings. 
         [0002]    The grand piano is a mature product that has remained relatively unchanged for nearly 100 years. Pianists, in general, must spend many years playing a piano in order to develop their technique. As a result, pianists, generally, prefer traditional piano actions because they learned to play on traditional piano actions which have remained unchanged. Traditional piano actions are made of wood. Typically, hornbeam or maple is used. 
         [0003]    Relative to more modern materials, such as composites or plastics, wood is an inefficient raw material from which to manufacture piano action components. Wooden action pieces must be drilled to produce the holes required for pivotal connections and assembly with other action components. The hole-drilling process is a laborious and costly process as compared to the production of molded piano action pieces with holes accurately formed therein during the initial molding process. 
         [0004]    Wood is hydroscopic, i.e. wood swells or shrinks as its moisture content changes in response to the environmental. This can cause binding in the action. Additionally, after repeated occurrences, this causes compression of the wood leading to failure of the piano action component. For instance, wooden flanges often crack due to expansion from a rise in moisture content, as the screw crushes the wood in the flange where it is fastened to the rail. Moreover, wood has different strengths in different directions, complicating manufacturing processes, also resulting in reduced manufacturing efficiencies. Additionally, the production of any finished wooden piece necessarily involves relatively large quantities of wasted material in the form of saw dust, which is inherent in any wood-working process. Finally, the lifespan of wooden piano action components is limited as compared to that of other materials such as composites or plastics because wood eventually crumbles into dust after a certain amount of environmental cycles. On the other hand, composite piano action components would eliminated all the preceding drawbacks and result in more efficient manufacture and maintenance of a piano. 
         [0005]    Thus far, all but one attempt to use composite piano action components has met with less than satisfactory market acceptance. This is because composite material is heavier than wood. Thus far, manufacturers have simply replaced traditional wood components with similarly designed and shaped composite components. This has resulted in an increased moment of inertia of the piano action. An increase in overall moment of inertia of a piano action system is unacceptable to the pianist. 
         [0006]    Playing the piano requires a great deal of hand strength. This requirement is amplified when the pianist is playing difficult musical pieces that require the key to respond very quickly for both volume and repetition. It is probably true that virtuosic piano pieces require strength and agility at the very limit of the abilities of the human hand. A pianist who depends on a key to move with a certain amount of finger strength will reject a piano action that requires more strength to produce the same key motion. 
         [0007]    U.S. Pat. No. 6,740,801 (Yoshisue) has met with limited market acceptance. The object of Yoshisue is to increase the efficiency of manufacture and maintenance of a grand piano action mechanism. In every claim, Yoshisue is limited to piano actions with at least one part in the action to be made of “synthetic resin having electrical conductivity at least on the surface thereof”. (Claim 1, Yoshisue.) The goal of this limitation is to eliminate static charge, thereby reducing the tendency of foreign particles to adhere to the action members as the particles cause wear, thereby resulting in decreased maintenance of the action mechanism. Yoshisue did not include the object of reducing the moment of inertia of the piano action. Also note that Yoshisue taught away from the use of plastic with a non-conductive surface in a piano action. 
         [0008]    We do believe that eliminating static charge does increase the lifespan of a piano action, but also believe that the detrimental effects springing from static charge are dwarfed by those related to the unacceptable feel of prior art composite piano actions and the high costs involved with prior art wooden piano actions. 
       OBJECT OF INVENTION 
       [0009]    The invention is a piano action that has less dynamic mass, and is thus more responsive, along with the extremely valuable collateral benefits of increased efficiency of manufacture and maintenance. In order to do this, particular attention was paid to component mass as a function of distance from center of mass of the component to the center of rotation of the repetition or center of rotation of the key. As a result, the pianist evaluates the piano action as being quicker, lighter, and more responsive. This invention is first to tie collateral benefits of increased efficiency of manufacture and maintenance of a piano action made from composite material with the added novelty of significantly reducing dynamic mass of a grand piano piano action. Additionally the invention is a direct replacement for practically any grand piano piano action. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0010]      FIG. 1  is a front view of the composite piano action. 
           [0011]      FIG. 2  is a front view of the Repetition Assembly. 
           [0012]      FIG. 3  is a perspective view of the Repetition Base. 
           [0013]      FIG. 4  is a perspective view from a bottom angle of the Repetition Base. 
           [0014]      FIG. 5  is a side view of the Repetition Base. 
           [0015]      FIG. 6  is a side view of the Jack. 
           [0016]      FIG. 7  is a perspective view of the Jack. 
           [0017]      FIG. 8  provides multiple views of the Moveable Multiple Height Heel (MMHH). 
           [0018]      FIG. 9  is a side view of the Repetition Base with Moveable Multiple Height Heel. 
           [0019]      FIG. 10  is a perspective view of the Balancier. 
           [0020]      FIG. 11  is a top and side view of the Balancier. 
           [0021]      FIG. 12  provides multiple views of a Regulating Button. 
           [0022]      FIG. 13  is a perspective view of the Repetition Flange. 
           [0023]      FIG. 14  is a perspective view of the Shank Flange. 
           [0024]      FIG. 15  is a side view depiction of the Half Stroke Line of a key. 
           [0025]      FIG. 16  provides multiple views of the Back Check. 
       
    
    
     DEFINITION LIST 
       [0026]      
         [0000]    
       
         
               
               
             
               
               
             
           
               
                   
               
               
                 Term 
                 Definition 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 10 
                 Composite piano action 
               
               
                 20 
                 Capstan contact point 
               
               
                 30 
                 Repetition Assembly 
               
               
                 33 
                 Repetition Assembly center of mass 
               
               
                 36 
                 Repetition Assembly Effective Radius 
               
               
                 40 
                 Repetition center of rotation 
               
               
                 50 
                 Key 
               
               
                 52 
                 White key capstan contact point at half stroke 
               
               
                 54 
                 White key half stroke line 
               
               
                 56 
                 Sharp key capstan contact point at half stroke 
               
               
                 58 
                 Sharp key half stroke line 
               
               
                 60 
                 Key center of rotation 
               
               
                 64 
                 Sharp key center of rotation 
               
               
                 66 
                 Capstan 
               
               
                 70 
                 Repetition Base 
               
               
                 73 
                 Stop for the Jack Regulating Button (replaces metal spoon) 
               
               
                 75 
                 Hole for “Helper Springs” 
               
               
                 77 
                 Adjustment screw location for “Helper Springs” 
               
               
                 79 
                 Repetition Base Female Notch System 
               
               
                 80 
                 Repetition Base center of mass 
               
               
                 85 
                 Repetition Base Effective Radius 
               
               
                 88 
                 Jack Assembly 
               
               
                 90 
                 Jack 
               
               
                 91 
                 Driving end of Jack 
               
               
                 92 
                 Hole for Jack regulating screw 
               
               
                 93 
                 Hole for Jack Spring 
               
               
                 94 
                 Jack center of rotation 
               
               
                 96 
                 Jack center of mass 
               
               
                 98 
                 Jack Effective Radius 
               
               
                 100 
                 Moveable Multiple Height Heel (MMHH) 
               
               
                 102 
                 Male Notch with offset key location used to connect to 
               
               
                   
                 Repetition Base 
               
               
                 104 
                 Notch to show orientation 
               
               
                 106 
                 MMHH Central Force Transfer Pillar 
               
               
                 108 
                 Gluing surface for capstan contact cloth 
               
               
                 109 
                 Gluing surface for bushing cloth 
               
               
                 110 
                 Repetition Base with Moveable Multiple Height Heel (MMHH) 
               
               
                 112 
                 Repetition Base with MMHH center of mass 
               
               
                 113 
                 Repetition Base with MMHH Effective Radius 
               
               
                 115 
                 Repetition center of rotation (40) to capstan contact point 
               
               
                   
                 (20) distance 
               
               
                 117 
                 Height of MMHH 
               
               
                 120 
                 Balancier 
               
               
                 122 
                 No lubricant require here as with wooden actions 
               
               
                 123 
                 Hole for regulating screw 
               
               
                 124 
                 Balancier center of rotation 
               
               
                 125 
                 Balancier Assembly 
               
               
                 126 
                 Balancier thinned to reduce mass 
               
               
                 127 
                 Gluing surface for buckskin 
               
               
                 128 
                 Gluing surface for Jack stop felt 
               
               
                 150 
                 Repetition Flange 
               
               
                 152 
                 Repetition Flange bushed pivot holes 
               
               
                 154 
                 Repetition Flange clearance notch 
               
               
                 156 
                 Repetition Flange screw hole 
               
               
                 158 
                 Repetition Flange “Helper Spring” silk cord notches 
               
               
                 160 
                 Shank Flange 
               
               
                 162 
                 Shank Flange screw hole 
               
               
                 164 
                 Shank Flange drop screw 
               
               
                 166 
                 Shank Flange rail cut 
               
               
                 168 
                 Hammer shank center of rotation 
               
               
                 170 
                 Regulating Button 
               
               
                 173 
                 Balancier Regulating Button 
               
               
                 176 
                 Jack Regulating Button 
               
               
                 180 
                 Back Check 
               
               
                 181 
                 Back Check felt gluing surface 
               
               
                 182 
                 Back Check buckskin gluing surface 
               
               
                 184 
                 Back Check felt area length 
               
               
                 186 
                 Back Check length 
               
               
                 188 
                 Back Check mount for back check wire 
               
               
                 189 
                 Back Check hole for check wire 
               
               
                 190 
                 Strategically shaped reinforcement material 
               
               
                 200 
                 Material removed to reduce mass 
               
               
                   
               
             
          
         
       
     
       DETAILED DESCRIPTION OF EMBODIMENTS 
       [0027]    The primary factors affecting dynamic mass of a piano action are: 1) mass of the composite piano action  10  at the capstan contact point  20 , 2) moment of inertia of the Repetition Assembly  30  about the Repetition Assembly center of rotation  33 , 3) moment of inertia of the Key  50  about the Key center of rotation  60 , and 4) mass of the Key  50 . The Repetition Assembly  30  is the Repetition Base  70  and the following items assembled to it: Jack Assembly  88 , Balancier Assembly  125 , and heel  100 . 
         [0028]    The static weight of the Repetition Assembly  30  at the point where the capstan contacts the cushion on the heel, hereafter known as the capstan contact point  20 , is critical to dynamic mass. A mode of this invention has a weight at this point of 14.1 grams. The two prior art equivalents weigh 16.6 grams (Kawai R2) and 21.9 grams (Kawai R1). We have achieved a 15% reduction over prior art composite grand piano actions. 
         [0029]    The moment of inertia of a rigid body rotating about a fixed axis is ∫r 2 dm, where r is the distance from center of rotation to the differential mass point of the body dm. The moment of inertia of a piano action component can be approximated by: (the distance from center of rotation to the center of mass) 2 ×(mass). 
         [0030]    Thus, the moment of inertia of the Repetition Assembly  30  can be accurately approximated using the distance from Repetition center of rotation  40  to the Repetition Assembly center of mass center of mass  33 —hereafter know as Repetition Assembly Effective Radius  36 —and the mass of the Repetition Assembly  30 . A mode of this invention  7  has a moment of inertia of 45,599 gmm 2  from Repetition Assembly mass of 16.6 grams and Repetition Assembly Effective Radius of 52.4 mm. 
         [0031]    The moment of inertia of the key is hard to calculate because it changes throughout the piano. The main factor affecting moment of inertia of the key is the number of leads added to the front of the key to balance the weight on the back end of the key from the hammers that hit the piano strings. Hammers decrease in weight from the bass to the treble as the mass needed to actuate the strings decreases due to the length of the strings and the frequency of the note. So, there are more leads in the bass keys of a piano than the treble keys. Typically there are 2 to 7 leads of ½″ diameter in the bass going to 0 to 1 in the treble. The number of leads in the key is also the primary factor affecting the static weight of the key. 
         [0032]    Thus, reducing lead count in the key is the metric we use with this invention to gauge the moment of inertia of the key  50  as well as the static weight of the Key  50 . This invention on average lowers the lead count in keys by 2-4 leads. 
         [0033]    In order to help describe the invention further, the inventors have divided the components of this invention into three groups. Different goals were used with the development of the components in each group. 
       Group 1 
       [0034]    Group 1 components are largely irrelevant to the moment of inertia of the piano action  10 , comprising: Repetition Flange  150 , and Shank Flange  160 . These parts are fixed in space and do not rotate. The Repetition Flange  150  provides secures the Repetition Base center of rotation  40 . The Shank Flange  160  secures the hammer. A flange is attached, by a screw, to a rail and thus rendered unmovable. Mass and inertia is not relevant to the performance a flange, as with all of Group 1. 
         [0035]    The primary material requirements for these parts are strength, rigidity, stability, and lifespan. In this case, the traditional material of Maple or Hornbeam has been replaced by a composite material. 
         [0036]    The best mode composite material is Nylon because Nylon has the highest tensile strength among composites and is also more conducive to gluing. Felt and buckskin must be attached to some action components to function. Additionally, the best mode composite material has glass filler because the glass increases tensile strength of the material. Both glass filled and unfilled composite materials have a non-conductive surface. Combining these two modes, we have determined that the overall best mode material is Nylon 6/6 40% glass filled because of its superior tensile strength and conduciveness to gluing. Maple has a tensile strength of approximately 2500 lbs/in 2 . Nylon 6/6 40% glass filled has a tensile strength of approximately 18,000 lbs/in 2 . 
         [0037]    Additionally, Group 1 is a direct replacement for their wooden counterparts in practically any grand piano. 
       Group 2 
       [0038]    Group 2 components are substantially relevant to the moment of inertia of the Repetition Assembly  30 , comprising: Regulating Button  170 , Jack  90 , Balancier  120 , and Back Check  180 . The parts in Group 2 all rotate about the Repetition Base center of rotation  40  or the Key center of rotation  60 . The center of mass of these components is a significant distance from the relevant center of rotation. The mass of this group of parts is felt dynamically by the pianist as part of the touch weight of the piano. Less mass is better to the limit where the part is no longer structurally sufficient for the task of vigorous piano playing. Group 2 includes the same material qualities as Group 1. Group 2 is also fully interchangeable with traditional wooden counterparts. 
         [0039]    Structural design of each Group 2 component is quite different from that of their traditional wooden counterparts. A concerted effort was taken to remove volume/material from the part, at the proper balance with rigidity requirements, and specifically removing volume furthest from the relevant center of rotation. 
         [0040]    The Regulating Button  170  uses the increased strength of composite material to make a part that would not be possible with wood. With the increased tensile strength, we were able to produce a Regulating Button  170  with a T-shape cross section that provides material only where it is needed. Wherever substantial material was “removed by design” from the traditionally shaped grand piano action component, it is designated by 200 on the drawings. Material removed to reduce mass has resulted in substantial weight reduction of the Regulating Button  170 . 
         [0041]    A Regulating Button  170  of this invention weights 0.18 grams. Prior art composite regulating buttons range from 0.30 (Kawai R2) to 0.40 (Kawai R1) grams. In comparison, with our lightest competitor we have achieved a 40% reduction in mass over prior art composite regulating buttons. 
         [0042]    Regulating Buttons  170  are used in two locations: at the Balancier  173  and at the Jack  176 . The Regulating Button on the Jack  176  is more critical. Less mass on the Jack  90  is important because the Jack  90  is a relative large action component that is located far from the Repetition center of rotation  40 . Any mass reduction in the Jack Regulating Button  176  will yield an exponential reduction in the moment of inertia of the Repetition Assembly  30 . The Jack Regulating Button  176  and the Balancier Regulating Button  173  are the same design. The Jack Assembly  88  is defined as the Jack  90  with Jack Regulating Button  176  assembled to it. The Balancier Assembly  125  is defined as the Balancier  120  with Balancier Regulating Button  173  assembled to it. 
         [0043]    The Jack  90  of this invention could not be made from wood. A traditional wood jack is made from two pieces of wood with a glued joint to connect the two pieces in an L shape. This glue joint is a common point of failure as the parts age. Two piece jacks were required because of the limited properties of wood. A one-piece wooden jack that meets rigidity requirements would be too thick. The thick heavy jack would make the action too heavy and the pianist would reject the heavy “feel” of the action. 
         [0044]    Our new Jack  90  is a dramatic departure. It is a one-piece composite component. The shape follows the function of the Jack without compromise, meaning that the new shape optimally applies torque on the Balancier  120  in the most efficient right-angle direction, as the two components rotate about the Repetition center of rotation  40 . A similarly shaped wooden counterpart would be impractically expensive to produce and would fail anyway, for want of rigidity. Our design allows a substantial reduction of material at various points  200  in the Jack  90 , thus substantially lightening the component, while leaving strategically shaped material  190  to provide increased rigidity over traditional wooden jacks. The superior strength of the composite material along with the fact that it is strong in all directions allows a one-piece Jack design that is lighter and better. Note that even though the shape of the Jack  90  is drastically different from that of the traditional wooden grand piano jack, this component is a direct replacement with most grand pianos. 
         [0045]    The moment of inertia of the Jack  90  can be accurately approximated using the distance from Jack center of rotation  94  to the Jack center of mass center of mass  96 —hereafter know as Jack Effective Radius  98 —and the mass of the Jack  90 . This invention has a Jack moment of inertia of 361 gmm 2  from Jack mass of 1.3 grams and Jack Effective Radius of 17.0 mm. 
         [0046]    The Balancier  120  of this invention is somewhat similar in shape to its traditional wooden counterpart, but the Balancier  120  still has many advantages. It has been thinned substantially at various locations  126  to reduce mass even though the overall part is only minimally lighter. Also, composite material slides smoothly at  122  about the Knuckle without lubricants while traditional wooden balanciers require lubricant at that point. Lubricants inevitably wear off leaving the potential for excessive friction at the knuckle and poor functioning of the action which is perceived by the pianist as added touch weight. Additionally, the best mode material is conducive to gluing and is required at  127  and  128 . 
         [0047]    The Balancier is 2.4 grams. Prior art composite balanciers range from 2.5 grams (Kawai R1) to 4.4 grams (Kawai R2). In comparison, with our lightest competitor we have achieved a 4% reduction in mass over prior art composite balanciers. 
         [0048]    The Back Check  180  is mounted on the Key  50 . The mass of the Back Check  180  must be calibrated to balance the weight exactly on each side of the Key  50 . Any reduction in mass of the Back Check  180  will allow the removal of weight on the front of the Key  50 , thus producing a reduction in touch resistance of the piano action. 
         [0049]    Our new Back Check  180 , as designed, could not be made from wood. The traditional back check is a solid block of wood that is longer and wider than the Back Check  180  of this invention. Older back checks were designed for a wide range of “checking heights”. Our Back Check  180  has a more narrow checking range as we believe there is no reason to have capability for such long checking distances anymore. 
         [0050]    The Back Check  180  is 23 mm long at  186 . A traditional back check is about 29 mm long. Our Back Check  180  has a felt area  182  that is 12 mm long. A traditional back check has felt area about that is 17 mm long. 
         [0051]    A traditional back check uses a soft felt under buckskin to provide a cushioned catcher for the hammer after the blow to the string. This results in an unpredictable stopping point on the check. Our new Back Check  180  uses a felt that is considerably more dense under the buckskin. This felt compresses less during checking so it provides a straighter inclined plane for the hammer to catch upon. As a result, the hammer comes to a sliding wedging stop. The result is more precise checking, that is, the hammer is stopped at a more consistent height among repetitions. Additionally, the reduced amount of felt and buckskin significantly reduces overall mass of the Back Check with felt and buckskin. 
         [0052]    The Back Check  180  is 0.9 grams. Prior art composite back checks range from 1.2 (Kawai R2) grams to 1.5 grams (Kawai R1). In comparison, with our lightest competitor we have achieved a 25% reduction in mass over prior art back checks. 
       Group 3 
       [0053]    Group 3 components are critically relevant to the moment of inertia of the piano action  10 , comprising: Repetition Base  70  and Multiple Height Moveable Heel  100 . Group 3 components rotate about the Repetition center of rotation  40 . Much of the mass associated with this Group of parts is a significant distance from the Repetition center of rotation  40 . The mass of this group of parts is drastically felt by the pianist as the primary component of the touch weight of the piano key. Less mass is better as long as structural requirements are met. Group 3 includes the same material qualities as Group 1. Group 3 is also fully interchangeable with traditional wooden counterparts. 
         [0054]    The Repetition Base  70  is not lighter than its wooden counterparts, however, the Repetition Assembly&#39;s ( 30 ) moment of inertia is substantially less than that of its wooden counterparts. Much of the weight of this part is in the bumper block right above the center of rotation  40  and is thus largely irrelevant. Mass furthest away from the center of rotation  40 , however, has been substantially reduced. 
         [0055]    Material was removed at strategic locations  200  in the Repetition Base  70 , thus substantially lightening the component, while leaving strategically shaped material to provide increased rigidity over traditional wooden repetitions. 
         [0056]    We have integrated the Stop for the Jack Regulating Button  73  into the Repetition Base  70 . Traditionally, a repetition has a metal spoon that acts as a stop for the Jack Regulating Button  176 . This integration allows the Jack to be more strategically positioned below the Knuckle and Balancier center of rotation  124 . Because a metal spoon is much heavier than either plastic or wood, we have integrated this stop into the composite part. In absolute terms this saves weight but the location of the weight loss is also important as a spoon is located far from the Repetition center of rotation  40 . The integration saves weight, reduces parts count, and streamlines manufacturing. 
         [0057]    One mode of the invention includes “whippen helper springs”. This mode includes a spring that takes weight off the capstan. The spring is attached to the Repetition Base at  75 . The mode includes a screw adjustment for the spring tension at  77 . 
         [0058]    The moment of inertia of the Repetition Base  70  can be accurately approximated using the distance from Repetition center of rotation  40  to the Repetition Base center of mass center of mass  80 —hereafter know as Repetition Base Effective Radius  85 —and the mass of the Repetition Base  70 . A mode of this invention has a measure of 15,605 gmm 2  from a Repetition weight of 8.8 grams and Repetition Effective Radius of 42.1 mm. 
         [0059]    The bottom of the Repetition Base  70  is designed so that the Moveable Multiple Height Heel  100  can be installed in a variety of positions onto the Repetition Base  70 . The bottom of the Repetition Base  70  has female notches spaced at 3 mm located at  79 . The corresponding male notch  102  in the Multiple Height Moveable Heel  100  is offset from the center of the part by 1.5 mm thus allowing the MMHH  100  to be attached in a variety of positions in 1.5 mm increments (by turning the MMHH around) along the length of the Repetition Base  100 . This allows the Repetition Assembly  10  to be customized to fit in a variety of non standard pianos. 
         [0060]    The moment of inertia of the Repetition with MMHH  110  can be accurately approximated using the distance from Repetition center of rotation  40  to the Repetition with MMHH center of mass center of mass  112 —hereafter know as Repetition with MMHH Effective Radius  113 —and the mass of the Repetition with MMHH. A mode of this invention has a measure of 20,951 gmm 2  from a Repetition with MMHH weight of 10.4 grams and Repetition with MMHH Effective Radius of 44.9 mm. 
         [0061]    The Multiple Height Moveable Heel  100  allows an unprecedented high degree of control over the location of the capstan contact point  20  on the MMHH  100 . The best mode of the MMHH provides eight different length options—12 mm through 18 mm in 1 mm increments. There is also a 20 mm mode. 
         [0062]    The MMHH allows for keyboards to be “tuned” to proper “half stroke line”, i.e. allows the sharp and white keys to simultaneously attain proper “half stroke line”. This is not achievable with prior art piano actions. 
         [0063]    Because the key and the repetition both move in separate arcs, their movement must be analyzed as a system in order to view the overall motion of the piano action  10 . The key and the repetition could be thought of as one teeter totter on the end of another larger teeter totter. The larger teeter totter is the key. The dynamics of the system will yield the optimum “feel” for the pianist when friction forces are minimized. In this system, friction is minimized when the key is on “half stroke design”. Half stroke design results in a lighter, faster more responsive piano action. 
         [0064]    A “half stroke line” is a theoretical line drawn from the Repetition center of rotation  40  to the capstan contact point  20  when the Repetition Assembly  30  is at half stroke, i.e. “when the key lifts the Repetition Base  70  exactly half way through the cycle boundaries of the Repetition Base”. That line is then extended down beyond the Key center of rotation  60 . This line is the “half stroke line”. 
         [0065]    Ideally, the half stroke line of each key intersects the balance point of that particular key. This is ideal because the key and the repetition both move in arcs and the slide path at the capstan will be minimized when the key balance points are in line. A key design with its balance point on the half stroke line will have less friction between the capstan and the heel. A reduction of friction at the capstan results in a lighter, faster, more responsive action. 
         [0066]    However, simultaneous half stroke design on each key is not possible because the Repetition center of rotation ( 40 ), capstan contact point ( 20 ), and heel size are fixed. Keyboards are designed to half stroke line for the white key only. We ask the question why limit yourself here. In response, we have made a heel to allow variation of the repetition center of rotation ( 40 ) to capstan contact point ( 20 ) distance and height  117 . This allows varying the capstan contact point  20  location with respect to the position of the key. This is depicted in  FIG. 15  where one can see two half stroke lines. The sharp key half stroke line  58  runs through points  40  and  64 . The white key half stroke line  54  runs through points  40  and  60 . This is proper half stroke design. 
         [0067]    One invention disclosed in this application is the first to provide near complete control for a keyboard designer to conduct a full half stroke setup on any grand piano. As discussed, half stroke design minimizes the slide path between the capstan and the repetition cushion and thus lowers friction. Additionally, because the friction does not need to be counterbalanced, less lead is required in the key. Thus, half stroke design also reduces mass in the system. The net result for the pianist is a faster more responsive action.