Patent Publication Number: US-8525007-B2

Title: Action of upright piano

Description:
This application is a national stage application of International Patent Application No. PCT/JP2010/004709 (WO 2011/013334 A1), filed Jul. 23, 2010, which is herein incorporated by reference in its entirety. 
     TECHNICAL FIELD 
     The present invention relates to a method of operating an action of an upright piano, and to an action of an upright piano. 
     BACKGROUND ART 
     An action of a typical grand piano is described (see, Non-Patent Document 1). In the following description, the front side seen from the piano player is referred to as “front”, the far side is referred to as “back”, the left side is referred to as “left”, and the right side is referred to as “right”. In addition, the expression “key is in its rest position” means that the front of a key is located at the highest point of its travel while the tail of the key is located at the lowest point of its travel. 
     A piano player depresses a key that is in its rest position. The tail of the key pushes up a wippen. A repetition lever and a jack raise a hammer roller, and a hammer pivots towards a string located above. Almost at the same time, a damper head rises and is released from its contact with the string. 
     The piano player further depresses the key. Immediately before the hammer reaches the string, a jack tail comes into contact with a regulating button. The jack pivots and a protruding end of the jack slips out from under the hammer roller. 
     Then, the hammer hits the string. It vibrates and produces a note. After hitting the string, the hammer rebounds and falls. At this point, the protruding end of the jack is no longer under the hammer roller. The hammer roller pushes down the repetition lever. The hammer falls back while receiving a force applied by a repetition spring. A back check catches the hammer. 
     Next, the piano player releases the key. The wippen falls and the hammer escapes from the back check. The repetition spring pushes up on the repetition lever and raises the hammer roller. As the wippen is at its lower position, the hammer rises slightly. Thus, the jack pivots by the force received from the jack spring. The protruding end of the jack moves back under the hammer roller. Accordingly, the piano player can depress the same key again and make the string vibrate to produce a note. The repetition lever comes into contact with a drop screw and stops the upward motion of the hammer. Subsequently, the hammer falls along with the wippen. 
     Because of the construction of grand pianos, the front of the key rises by approximately one third of the key dip distance from the lowest point of its travel to its rest position when the protruding end of the jack moves back under the hammer roller. In a grand piano, when the key rises by approximately one third of the key dip distance from the lowest point of its travel to its rest position, the piano player can depress the same key again and make the string vibrate to produce a note. According to a certain experiment that the present inventor knows, the piano player can play 14 repeated notes per second on the same key within a given period of time. 
     The unique key touch of the grand piano is provided with the following first to third forces. The first force is a force that is transmitted from a repetition spring to the key. The second force is a force that is transmitted to the key when the protruding end of the jack moves back under the hammer roller. The third force is a force that is transmitted to the key when the repetition lever comes into contact with the drop screw. 
     An action of a typical upright piano is described (see, Non-Patent Document 1). 
     A piano player depresses a key that is in its rest position. The tail of the key pushes up a wippen, and the wippen rotates. A protruding end of a pushing-up portion of a jack pushes up a pushed-up portion of a hammer butt. The hammer butt and a hammer pivot towards a string on a hammer butt flange. As the wippen rotates, a damper head is released from its contact with the string. 
     The piano player further depresses the key. The jack tail strikes a regulating button, and the jack pivots. Then, the protruding end of the pushing-up portion of the jack slips out from under the pushed-up portion of the hammer butt. The hammer is disengaged from the motion of the key. This disengagement is so-called “let-off”. 
     The hammer continues to move towards the string on its own inertia and hits the string, allowing it to vibrate. After hitting the string, the hammer rebounds from the string. A back check catches a catcher, which stops the motion of the hammer. 
     Next, the piano player releases the key. The wippen falls and the catcher escapes from the back check. In addition, the jack tail escapes from the regulating button. When the wippen completely falls, a gap is formed under the pushed-up portion of the hammer butt into which the protruding end of the pushing-up portion of the jack can be inserted. Then, the jack pivots by the force received from the jack spring. The protruding end of the pushing-up portion of the jack slips under the pushed-up portion of the hammer butt and they engage with each other. 
     Next, the gap required to engage the jack and the hammer butt in the upright piano is described. 
     The piano player depresses the key to the lowest point of its travel. Because of the construction of actions of the upright piano, the front of the key falls by approximately 10 mm, the tail of the key pushes up the heel of the wippen by approximately 5 mm, and the jack flange rises by approximately 5 mm. When compared with the key in its rest position, the protruding end of the pushing-up portion of the jack rises by approximately 5 mm after escaping from under the hammer butt. On the other hand, the hammer butt is pushed up by the jack and pivots on the hammer butt flange. The distance between the hammer butt flange and the pushed-up portion of the hammer butt is short. Thus, as the back check catches the catcher, the pushed-up portion of the hammer butt is raised only by approximately 1 mm from its rest position. The values given herein are merely examples. In the upright piano, the amount that the protruding end of the pushing-up portion of the jack is raised is significantly larger than the amount that the pushed-up portion of the hammer butt is raised. As a result, when the wippen falls completely and the key returns to its rest position, a gap is formed under the pushed-up portion of the hammer butt into which the protruding end of the pushing-up portion of the jack can be inserted. Until the key returns to its rest position, there is no such a gap under the pushed-up portion of the hammer butt. 
     If the protruding end of the pushing-up portion of the jack moves towards under the pushed-up portion of the hammer butt before the key returns to its rest position, the protruding end of the pushing-up portion of the jack hits a surface located in front of and above the pushed-up portion of the hammer butt. The protruding end of the pushing-up portion of the jack cannot be slipped under the pushed-up portion of the hammer butt. Thus, it is impossible to engage the jack and the hammer butt with each other. 
     When the jack and the hammer butt engage with each other, the piano player can depress the same key again and make the string vibrate to produce a note. According to the aforementioned experiment, the piano player can play 7 repeated notes per second on the same key within a given period of time. This means that the upright piano is inferior to the grand piano from the viewpoint to permit playing of repeated notes. 
     In addition, the action of the upright piano does not have the repetition lever, the repetition spring, the hammer roller and the drop screw. Thus, the touch of the keys of the upright piano is significantly different from the touch of the keys of the grand piano. 
     In upright pianos, improved actions have been suggested in order to permit more rapid playing of repeated notes on a single key. 
     One improvement of the action of the upright piano is, for example, as described below (see, Patent Document 1). This technique is referred to as a related art 1. 
     The action according to the related art 1 has a spring member provided on the pushing-up portion of the jack. When the pushing-up portion of the jack slips out under the pushed-up portion of the hammer butt, the spring member comes into contact with the regulating rail and forces the jack against the hammer butt. 
     When the piano player releases the key, the wippen and the jack move down. The jack pivots by the force received from the jack spring and the spring member. Then, the jack and the hammer butt engage with each other. 
     In addition, another improvement of the action of the upright piano is as described below (see, Patent Document 2). This technique is referred to as a related art 2. 
     In the action according to the related art 2, a compression coil is provided as a jack/repetition spring between the protruding end of the pushing-up portion of the jack and the catcher. When the pushing-up portion of the jack slips out under the pushed-up portion of the hammer butt, the jack/repetition spring forces the jack against the hammer butt. In addition, a hammer return spring is engaged with the hammer butt. The hammer return spring aids the motion of the hammer rebounding from the string after hitting it. 
     When the piano player releases the key, the wippen and the jack move down and the jack tail escapes from the regulating button. The jack pivots by the force received from the jack/repetition spring. Then, the jack and the hammer butt engage with each other. 
     RELATED ART DOCUMENT(S) 
     Patent Document(s) 
     
         
         Patent Document 1: Japanese Patent Laid-open No. 2006-91516 
         Patent Document 2: Japanese Patent No. 2656323 
       
    
     Non-Patent Document(s) 
     
         
         Non-patent Document 1: Isoharu Nishiguchi and Taro Mori, “Motto shiritai piano no shikumi”, 1st edition, Ongaku No Tomosha, Apr. 30, 2005, pp. 65-77 
       
    
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     The action of the upright piano according to the related art 1 has a following problem. 
     In the action according to the related art 1, the role of the spring member is to reinforce the jack spring. Timing at which the jack engages with the hammer butt after the piano player releases the key is when the gap is formed under the pushed-up portion of the hammer butt into which the protruding end of the pushing-up portion of the jack can be inserted. Thus, as the typical upright pianos, the piano player should wait until the key returns to its rest position in order to make the string vibrate to produce a note on the same key. 
     It is assumed that the elastic modulus of the spring member and the torque applied from the spring member to the jack are increased to forcefully insert the pushing-up portion of the jack under the pushed-up portion of the hammer butt. However, this way is unpractical because of the following trouble. When the pushing-up portion of the jack is inserted under the pushed-up portion of the hammer butt, a force is transmitted from the jack to the hammer butt. This force is smaller than the force that the jack pushes up the hammer butt when the piano player depresses the key. However, this force is enough to push up the hammer butt and pivot the hammer. Accordingly, the hammer butt pivots, and its hammer head hits the vibrating string to stop the vibration of the string. This is a significant problem in playing notes. 
     In addition, the action according to the related art 1 does not have the repetition lever, the repetition spring, the hammer roller, and the drop screw. The aforementioned first to third forces in the grand piano will not be generated. Thus, the touch of the keys is significantly different from that of the grand piano. 
     The action of the upright piano according to the related art 2 has a following problem. 
     In the action according to the related art 2, the role of the jack/repetition spring is to substitute for the jack spring. Timing at which the jack engages with the hammer butt after the piano player releases the key is when the gap is formed under the pushed-up portion of the hammer butt into which the protruding end of the pushing-up portion of the jack can be inserted. Thus, as the typical upright pianos, the piano player should wait until the key returns to its rest position in order to make the string vibrate to produce a note on the same key. 
     The Patent Document 2 describes that “the jack and the hammer butt engage with each other when the key rises by approximately half of the key dip distance from the lowest point of its travel to its rest position after the piano player releases the key”. However, this results in a similar problem to the one in the related art 1. More specifically, inserting the pushing-up portion of the jack under the pushed-up portion of the hammer butt pushes up the hammer butt. The hammer pivots, and the hammer head hits the vibrating string to stop the vibration of the string. Accordingly, the construction described as “the jack and the hammer butt engage with each other when the key rises by approximately half of the key dip distance from the lowest point of its travel to its rest position after the piano player releases the key” is accompanied by a practical problem. 
     In addition, the hammer return spring merely returns the hammer toward a hammer rest rail after hitting the string. It is assumed that the elastic modulus of the hammer return spring and the torque applied from the hammer return spring to the hammer butt are increased to prevent the pivot motion of the hammer which otherwise occurs when the pushing-up portion of the jack is inserted under the pushed-up portion of the hammer butt. However, this results in transmittance of a force from the hammer return spring to the key, producing significantly heavy touch of the key. 
     It may be tolerated to stop the vibration of the string with the hammer head and to produce the significantly heavy touch of the key. However, it is impossible to play repeated notes as rapid as in the grand piano. This is because the piano player should wait until the key rises by approximately half of the key dip distance from the lowest point of its travel to its rest position in order to make the string vibrate to produce a note on the same key. 
     Furthermore, the jack/repetition spring is a compression coil. The direction of the force applied from the jack/repetition spring to the pushing-up portion of the jack tends to be varied and it is impossible to ensure uniformity of touch of the key. 
     In addition, the action according to the related art 2 does not have the repetition lever, the repetition spring, the hammer roller, and the drop screw. The first to third forces in the grand piano will not be generated. Thus, the touch of the keys is significantly different from that of the grand piano. 
     The present invention is provided to solve the aforementioned problems, and an object thereof is to provide a method of operating an action of an upright piano, as well as an action of an upright piano with which it is possible to play repeated notes on a single key as in the grand piano, the hammer is prevented from hitting the vibrating string even when the jack and the hammer butt engage with each other to permit playing of repeated notes on a single key, and the touch of the keys replicates a grand piano. 
     Means to Solve the Problem 
     The present invention has a following construction in order to solve the problems. In a method of operating an action of an upright piano having strings according to the invention as claimed in Claim  1 , the action comprises a regulating rail, a jack stop rail, a main action rail, a damper stop rail, a wippen, a jack, a hammer butt, and a hammer, the action further comprising a jack spring between the wippen and a jack tail of the jack, the action being adapted to operate, when a piano player depresses a key, in such a manner that the wippen moves up with rotating, a protruding end of a pushing-up portion of the jack pushes up a pushed-up portion of the hammer butt from below, the hammer pivots and hits a corresponding string, the jack tail of the jack strikes a regulating button, and that a protruding end of the pushing-up portion slips out from under the pushed-up portion, wherein either one member of said regulating rail and said jack stop rail serves as a first rail; either one member of said first rail and said pushing-up portion has a first spring; the other member of said first rail and said pushing-up portion that does not have said first spring has a first spring rest adapted to come into contact with said first spring; either one member of said main action rail and said damper stop rail serves as a second rail; one member of said second rail, a hammer core of said hammer, a hammer shank of said hammer, and said hammer butt has a second spring; if one member of said hammer core, said hammer shank, and said hammer butt has said second spring, then said second rail has a second spring rest adapted to come into contact with said second spring, and if said second rail has said second spring, then one member of said hammer core, said hammer shank, and said hammer butt has the second spring rest adapted to come into contact with said second spring; when the piano player depresses said key and the protruding end of said pushing-up portion slips out from under said pushed-up portion, said first spring is bent between the member having said first spring and said first spring rest, and when the piano player releases said key, said wippen moves down with rotating, and said jack tail escapes from said regulating button, said first spring that has been bent between the member having said first spring and said first spring rest pushes the protruding end of said pushing-up portion against a surface that is located in front of and above said pushed-up portion of said hammer butt, and said pushing-up portion is inserted under said pushed-up portion; when said first spring forces said pushing-up portion under said pushed-up portion, said hammer pivots towards said string by a force applied from said pushing-up portion to said pushed-up portion, said second spring is bent between the member having said second spring and said second spring rest before the rotation hammer hits said string, said second spring that has been bent applies a force to said hammer, the force applied from said second spring that has been bent to said hammer stops the pivot motion of said hammer before pivoting hammer hits said string. 
     When the piano player depresses a key, the protruding end of the pushing-up portion of the jack slips out from under the pushed-up portion of the hammer butt. The first spring is bent between the member having the first spring and the first spring rest. The bent first spring applies a force to the pushing-up portion of the jack. 
     Next, when the piano player releases the key, the wippen moves down with rotating. As the jack tail escapes from the regulating button, the jack receives a force from the first spring and pivots towards the hammer butt. When the jack pivots towards the hammer butt, the protruding end of the pushing-up portion of the jack is pushed against the surface that is located in front of and above the pushed-up portion of the hammer butt. The force produced by the first spring is applied to the hammer butt through the jack. The force produced by the first spring pushes up the hammer butt. The hammer butt then pivots on a hammer butt flange. The first spring forcefully pushes the protruding end of the pushing-up portion of the jack under the pushed-up portion of the hammer butt. Thus, the jack engages with the hammer butt. 
     When the jack engages with the hammer butt, the hammer butt pivots by receiving the force produced by the first spring, and the hammer also pivots towards the string. Then, the second spring is bent between the member having the second spring and the second spring rest. The bent second spring applies a force to the pivoting hammer. The force produced by the second spring stops the pivot motion of the hammer before the hammer hits the string. It should be noted that the force applied from the second spring to the hammer has a component opposite to the string, that is, a component of the force directing forward. 
     Because of the construction of upright pianos, when the jack tail escapes from the regulating button, the key rises by approximately one third of the key dip distance from the lowest point of its travel to its rest position. This means that, when the key rises by approximately one third of the key dip distance from the lowest point of its travel to its rest position, the force produced by the first spring forcefully engages the jack with the hammer butt. As a result, the piano player can depress the same key again and make the string vibrate to produce a note. 
     When either one member of the hammer core, the hammer shank, and the hammer butt has the second spring rest, the second spring rest rotates along with the hammer. The closer the second spring rest is located to the hammer butt flange, the slower the second spring rest rotates. Accordingly, the closer the second spring rest is located to the hammer butt flange, the smaller the sound produced as the second spring strikes the second spring rest. 
     When the second rail has the second spring rest, the second spring rotates along with the hammer. The closer the position of the second spring abutted against the second spring rest is located to the hammer butt flange, the slower that position rotates. Accordingly, the closer the position of the second spring abutted against the second spring rest is located to the hammer butt flange, the smaller the sound produced as the second spring strikes the second spring rest. 
     A portion of the second spring that is to be abutted against the second spring rest may be covered with a flexible material. In addition, a portion of the second spring rest that is to be abutted against the second spring may be covered with a flexible material. The flexible material may be, for example, a fabric such as felt, a resin, or leather. This reduces the sound produced as the second spring strikes the second spring rest. 
     From the viewpoint of the magnitude of the torque that the second spring applies to the hammer, the second spring requires smaller elastic modulus as the point of application of the force applied from the second spring to the hammer leaves away from the rotation center of the hammer. The rotation center of the hammer is on the hammer butt flange. By adjusting the elastic modulus of the second spring and the location of the point of application of the force applied from the second spring to the hammer, the influence of the second spring on the touch of the key can be adjusted. 
     The piano player feels the following fourth to sixth forces. The fourth force is transmitted from the first spring to the key. The fifth force is transmitted to the key when the jack engages with the hammer butt. The sixth force is transmitted to the key when the pivot motion of the hammer is stopped by the force produced by the second spring. These three forces are responsible for determining the touch of the key. That touch replicates a grand piano. This is because the fourth force corresponds to the first force in the grand piano. In addition, the fifth force corresponds to the second force in the grand piano. Furthermore, the sixth force corresponds to the third force in the grand piano. 
     It should be noted that a jack stop rail or a regulating rail used in a conventional upright piano may serve, for example, as the first rail. Alternatively, the first rail may be an additional rail provided between the action brackets. On the other hand, a main action rail or a damper stop rail used in a conventional upright piano may serve, for example, as the second rail. Alternatively, the second rail may be an additional rail provided between the action brackets. 
     A part of the member having the first spring rest may form the first spring rest. In addition, the member having the first spring rest may have a component forming the first spring rest. 
     A part of the member having the second spring rest may form the second spring rest. In addition, the member having the second spring rest may have a component forming the second spring rest. 
     According to the finding of the present inventor, it is not preferable that the first spring also doubles as the jack spring. If the first spring doubles as the jack spring, the keys will have a very heavy touch of the key when the piano player depresses the keys in their rest positions. This is because the force applied from the first spring to the jack is larger than the force applied from the jack spring to the jack. 
     In an action of an upright piano having strings according to the invention as claimed in Claim  2 , the action comprises a regulating rail, a jack stop rail, a main action rail, a damper stop rail, a wippen, a jack, a hammer butt, and a hammer, the action further comprising a jack spring between the wippen and a jack tail of the jack, the action being adapted to operate, when a piano player depresses a key, in such a manner that the wippen moves up with rotating, a protruding end of a pushing-up portion of the jack pushes up a pushed-up portion of the hammer butt from below, the hammer pivots and hits a corresponding string, the jack tail of the jack strikes a regulating button, and that a protruding end of the pushing-up portion slips out from under the pushed-up portion, wherein either one member of said regulating rail and said jack stop rail serves as a first rail; either one member of said first rail and said pushing-up portion has a first spring; the other member of said first rail and said pushing-up portion that does not have said first spring has a first spring rest adapted to come into contact with said first spring; either one member of said main action rail and said damper stop rail serves as a second rail; one member of said second rail, a hammer core of said hammer, a hammer shank of said hammer, and said hammer butt has a second spring; if one member of said hammer core, said hammer shank, and said hammer butt has said second spring, then said second rail has a second spring rest adapted to come into contact with said second spring, and if said second rail has said second spring, then one member of said hammer core, said hammer shank, and said hammer butt has the second spring rest adapted to come into contact with said second spring; said action being adapted to produce a first force and a second force, the first force being applied by said first spring that has been bent between the member having said first spring and said first spring rest to said pushing-up portion when the piano player releases said key, said wippen moves down with rotating, and said jack tail escapes from said regulating button, the second force being applied by said second spring that has been bent between the member having said second spring and said second spring rest to said hammer when said first spring forces said pushing-up portion under said pushed-up portion and said hammer pivots towards said string by the force applied from said pushing-up portion to said pushed-up portion, the first force having magnitude and direction that press the protruding end of said pushing-up portion to a surface located in front of and above said pushed-up portion of said hammer butt and the force having magnitude and direction that force said pushing-up portion under said pushed-up portion, the second force having magnitude and direction that stop the pivot motion of said hammer before said hammer hits said string. 
     The invention as claimed in Claim  1  is implemented by the invention as claimed in Claim  2 . 
     The action of an upright piano according to the invention as claimed in Claim  3  is the action of an upright piano as claimed in Claim  2 , wherein said first spring is a leaf spring or a torsion coil spring, said first spring having a leg adapted to be abutted against said first spring rest. 
     The leg of the first spring comes into contact with the first spring rest, which results in the application of a force from the first spring to the pushing-up portion of the jack. By changing the shape of the leg abutted against the first spring rest, the magnitude of the force or the torque applied from the first spring to the pushing-up portion of the jack can be adjusted easily. To change the shape of the leg of the first spring, the degree of flexure or bent of the leg may be changed, for example. 
     According to the examinations made by the present inventor, when the first spring is a leaf spring or a torsion coil spring, the direction and the magnitude of the force applied from the first spring to the first spring rest is less fluctuated. This ensures uniformity of touch of the keys. 
     It is more preferable that the first spring is a torsion coil spring. The elastic modulus of the first spring can be adjusted easily by changing the number of windings in a coil or a diameter of the coil. 
     The action of an upright piano according to the invention as claimed in Claim  4  is the action of an upright piano as claimed in Claim  2  or  3 , wherein said second spring is a leaf spring or a torsion coil spring, said second spring having a leg adapted to be abutted against said second spring rest. 
     The leg of the second spring comes into contact with the second spring rest, which results in the application of a force from the second spring to the hammer. By changing the shape of the leg abutted against the second spring rest, the magnitude of the force or the torque applied from the second spring to the hammer can be adjusted easily. To change the shape of the leg of the second spring, the degree of flexure or bent of the leg may be changed, for example. 
     It is more preferable that the second spring is a torsion coil spring. The elastic modulus of the second spring can be adjusted easily by changing the number of windings in a coil or a diameter of the coil. 
     According to the examinations made by the present inventor, when the second spring is a leaf spring or a torsion coil spring, the direction and the magnitude of the force applied from the second spring to the second spring rest is less fluctuated. This ensures uniformity of touch of the keys. 
     The action of an upright piano according to the invention as claimed in Claim  5  is the action of an upright piano as claimed in any one of Claims  2  to  4 , wherein a first bolt is threaded with and passes through one member of said first rail and said pushing-up portion that has said first spring rest, a tip of a threaded portion of the first bolt supporting said first spring rest. 
     The tip of the threaded portion of the first bolt is projected out of a bolted member. Changing the length of the projection facilitates adjustment of the contact between the first spring and the first spring rest. By adjusting this contact, the magnitudes of the force and torque that the first spring applies to the pushing-up portion of the jack can be adjusted easily. 
     The action of an upright piano according to the invention as claimed in Claim  6  is the action of an upright piano as claimed in any one of Claims  2  to  5 , wherein a second bolt is threaded with and passes through one member of said second rail, said hammer core, said hammer shank, and said hammer butt that has said second spring rest, a tip of a threaded portion of the second bolt supporting said second spring rest. 
     The tip of the threaded portion of the second bolt is projected out of a bolted member. Changing the length of the projection facilitates adjustment of the contact between the second spring and the second spring rest. By adjusting this contact, the magnitudes of the force and torque that the second spring applies to the hammer can be adjusted easily. 
     Effect of the Invention 
     The method of operating the action of the upright piano as well as the action of the upright piano as described above permits playing of repeated notes on the single key, which is comparable to grand pianos. Even when the jack engages with the hammer butt to repeat a note, the hammer is prevented from hitting the vibrating string. The resulting touch of the key is equivalent to that offered by a grand piano. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  A construction view showing an action of an upright piano when a key is in its rest position. 
         FIG. 2  A construction view showing the action of an upright piano immediately after the key is fully depressed and the hammer hits a string. 
         FIG. 3  A construction view showing the action of an upright piano at a time when the key is returned by one third of a key dip distance from the lowest point of its travel to its rest position. 
         FIG. 4  A construction view showing a first spring and a second spring, in which (i) represents a front view of the first spring and the second spring, while (ii) represents a left side view of the first spring and the second spring. 
         FIG. 5  A partially enlarged view of  FIG. 1 . 
         FIG. 6  A construction view showing an action of an upright piano according to a first modified version, immediately after the key is fully depressed and the hammer hits a string. 
         FIG. 7  A construction view showing an action of an upright piano according to a second modified version. 
         FIG. 8  A partially enlarged view of  FIG. 7 . 
         FIG. 9  A construction view showing a first spring and a second spring according to a second modified version, in which (i) represents a front view of the first spring and the second spring, while (ii) represents a left side view of the first spring and the second spring. 
         FIG. 10  A front view showing an upper part of a pushing-up portion of a jack according to the second modified version. 
     
    
    
     EMBODIMENTS FOR CARRYING OUT THE INVENTION 
     Embodiments for carrying out the present invention are described with reference to  FIGS. 1 to 5 . In the following description, expressions “clockwise” or “counter-clockwise” refer to a clockwise or counter-clockwise direction, respectively, from the perspective of  FIGS. 1 to 3 . 
     As shown in  FIGS. 1 to 3 , an upright piano according to this embodiment has a set of keys  1  (only one of which is shown) aligned horizontally and strings  90  that correspond to the respective keys  1 . Balance rail pins (not shown) are provided on a key frame  3 . Each key  1  is supported by a balance rail pin in the center of the key  1  so that the key  1  can rock on a fulcrum. Action brackets (not shown) are provided on each end of the key frame  3 . The action brackets hold a main action rail  4  between them. 
     An action  7  extends back and upward from the key  1 . The action  7  comprises a wippen  8 , a jack  18 , a hammer butt  25 , a hammer  32 , and a damper  39 .  FIGS. 1 to 3  show the action  7  in a perspective from the left side. 
     A spoon  9  extends upward from the back end of the wippen  8 . A wippen flange  10  is attached to a lower part of the main action rail  4 . The wippen  8  is hinged with the wippen flange  10  at a position slightly ahead of the spoon  9 . The wippen  8  has a heel  11  on the lower side thereof and has a jack flange  12  on the upper side thereof. The heel  11  and the jack flange  12  are located ahead of the wippen flange  10 . The heel  11  rests on a capstan  2  inserted into the tail of the key  1 . A back check wire  14  extends upward from the front end of the wippen  8 . The back check wire  14  supports a back check  15  at the end thereof. 
     The jack  18  has a jack tail  19  and a pushing-up portion  20 . The jack tail  19  projects upward and the pushing-up portion  20  extends vertically. The jack tail  19  and the pushing-up portion  20  form an “L” shape. At the corner of the “L” shape, the jack  18  is hinged with the jack flange  12 . A jack spring  13  is provided between the jack tail  19  and the wippen  8  to force the jack tail  19  upward. A torsion coil spring forming a first spring  59  is attached to a lower end of the front surface of the pushing-up portion  20 . The jack  18  is the member that has the first spring  59 . 
     As shown in  FIG. 4 , the first spring  59  has a coil member  60  and two legs  62 ,  63 . One end of the coil member  60  is connected to the leg  62  and the other end of the coil member  60  is connected to the leg  63 . The leg  62  is embedded in the pushing-up portion  20 . The leg  63  extends vertically and the upper end of the leg  63  is a free end. A regulating button  47  is provided above the jack tail  19 . The regulating button  47  is supported at one end of a regulating screw  49 . The regulating screw  49  is threaded with a regulating rail  48  extending horizontally. The regulating rail  48  is attached to the main action rail  4  with a fork screw  50 . 
     A jack stop rail  53  is provided in front of the pushing-up portion  20 . The jack stop rail  53  extends horizontally and serves as a first rail. The jack stop rail  53  is attached to the main action rail  4  with a regulating screw for the jack stop rail  54 . A first bolt  81  is threaded with and passes through the jack stop rail  53 . The tip of the threaded portion of the first bolt  81  projects from the back of the jack stop rail  53 . A first spring rest  71  is supported at the end of the threaded portion of the first bolt  81 . The jack stop rail  53  is the member that has the first spring rest  71 . 
     The first spring rest  71  has a base  73  and a felt  77 . The tip of the threaded portion of the first bolt  81  supports the base  73  from the front. The back surface of the base  73  has the felt  77  glued thereto. The felt  77  faces to the front surface of the pushing-up portion  20 . The felt  77  has a width that is equal to or larger than the width (i.e., the right-and-left direction) of the pushing-up portion  20 . 
     The elastic modulus of the first spring  59  and the torque that the first spring  59  applies to the jack  18  are adjusted as follows. The torque that the first spring  59  applies to the jack  18  is produced when the first spring  59  strikes the first spring rest  71  and is bent. The magnitudes of the elastic modulus and the torque are determined in order not to interfere with the let-off of the jack  18  when a piano player depresses the key  1 . In addition, the magnitudes of the elastic modulus and the torque are determined so that the protruding end of the pushing-up portion  20  is forcefully inserted under a pushed-up portion  27  when the piano player releases the key  1 . 
     A hammer butt flange  26  is attached to the upper front portion of the main action rail  4 . The lower back surface of the hammer butt  25  is connected to the hammer butt flange  26  so that hammer butt  25  can pivot on the hammer butt flange  26 . The upper front surface of the hammer butt  25  is connected to a catcher  29  through a catcher shank  28 . The hammer butt  25  has the pushed-up portion  27  on the lower surface thereof. The pushed-up portion  27  has a leather skin  75  adhered to it. The front surface of the hammer butt  25  has a leather skin  76  at a position lower than the root of the catcher shank  28 . In other words, the hammer butt  25  has the skin  76  adhered thereto at a position that is ahead of and above the pushed-up portion  27 . The front-facing end of the skin  75  and the lower end of the skin  76  is integrally connected to each other. 
     The hammer  32  has a hammer shank  33  and a hammer head  34 . The hammer shank  33  extends up from the upper surface of the hammer butt  25 . The hammer head  34  is attached to the upper end of the hammer shank  33 . The hammerhead  34  has a hammer core  35  and a hammer felt  36 . The hammer core  35  extends back from the upper end of the hammer shank  33 . The hammer felt  36  is glued to the back end of the hammer core  35 . 
     A second bolt  82  is threaded with the hammer shank  33  near its upper end and passes through the hammer shank  33  in a front-to-back direction. The tip of the threaded portion of the second bolt  82  projects into the back of the hammer shank  33 . A second spring rest  72  is supported at the end of the threaded portion of the second bolt  82 . The hammer shank  33  is the member that has the second spring rest  72 . 
     The second spring rest  72  has a base  74  and a felt  78 . The tip of the threaded portion of the second bolt  82  supports the base  74  from the front. The back surface of the base  74  has the felt  78  glued thereto. The felt  78  faces back. The felt  78  has a width that is equal to or larger than the thickness of the hammer shank  33 . 
     A damper  39  has a damper lever  40 , a damper wire  43 , and a damper head  44 . 
     A damper flange  41  is attached to the upper back portion of the main action rail  4 . The damper lever  40  is hinged with the damper flange  41  in the center of the damper lever  40 . The lower front end of the damper lever  40  faces to one end of the spoon  9 . The damper head  44  is connected to the upper end of the damper lever  40  through the damper wire  43 . A damper spring  42  connected to the damper lever  40 . The damper head  44  is pressed against the string  90  while being spring-loaded or biased with the damper spring  42 . 
     A hammer stop rail  55  is provided in front of the hammer shank  33 . A damper stop rail  56  is provided in front of the damper wire  43 . The hammer stop rail  55  and the damper stop rail  56  are held between the action brackets. The damper stop rail  56  serves as a second rail. 
     A torsion coil spring forming a second spring  66  is attached to a front surface of the damper stop rail  56 . The damper stop rail  56  is the member that has the second spring  66 . 
     As shown in  FIG. 4 , the second spring  66  has a coil member  61  and two legs  67 ,  68 . One end of the coil member  61  is connected to the leg  67  and the other end of the coil member  61  is connected to the leg  68 . The leg  67  is embedded in the damper stop rail  56 . The leg  68  has an angled “7” shaped end. The angled “7” shaped end of the leg  68  has a width (i.e., a length in the right-and-left direction) that is equal to or larger than the width (i.e., the length in the right-and-left direction) of the felt  78 . The leg  68  extends diagonally upward and forward and the upper end thereof is a free end. The leg  68  has a length so that the leg  68  does not interfere with the hammer head  34  swinging about the hammer butt flange  26 . In addition, the length of the leg  68  is determined so that the angled “U” shaped end of the leg  68  is abutted against the second spring rest  72  when the hammer shank  33  swings about the hammer butt flange  26 . 
     The elastic modulus of the second spring  66  and the torque that the second spring  66  applies to the hammer  32  are adjusted as follows. The torque that the second spring  66  applies to the hammer  32  is produced when the second spring  66  is bent between the damper stop rail  56  and the second spring rest  72 . The magnitudes of the elastic modulus and the torque are determined in order not to interfere with the hammer  32  hitting the string  90  when the piano player depresses the key  1 . In addition, the magnitudes of the elastic modulus and the torque are determined so that the hammer  32  stops its motion before the hammer  32  hits the string  90  when the piano player releases the key  1 . 
     The strings  90  are stretched behind the action  7 . 
     The upright piano according to this embodiment is similar in construction to conventional upright pianos except that the action  7  has the first spring  59 , the second spring  66 , the first spring rest  71 , and the second spring rest  72 . 
     Next, an operation is described. First, a case is described where the key  1  is in its rest position (see  FIGS. 1 and 5 ). When the key  1  is in its rest position, the front of the key  1  is located at the highest point of its travel while the tail of the key  1  is located at the lowest point of its travel. The wippen  8  is located at the lowest point of its travel. 
     The protruding end of the pushing-up portion  20  of the jack  18  is caught under the pushed-up portion  27  of the hammer butt  25 . The pushing-up portion  20  is engaged with the pushed-up portion  27 . The jack tail  19  is away from the regulating button  47 . There is a gap between the pushing-up portion  20  and the first spring rest  71 . There is also a gap between the end of the leg  63  of the first spring  59  and the front surface of the pushing-up portion  20 . The leg  63  is abutted against the felt  77  of the first spring rest  71 . It is preferable that the force that the leg  63  applies to the first spring rest  71  is as small as possible. It is most preferable that the force applied by the leg  63  to the first spring rest  71  is equal to zero. 
     The hammer butt  25  is located at the lowest point of its travel and the catcher  29  is also located at the lowest point of its travel. The catcher  29  is away from the back check  15 . The hammer shank  33  is abutted against the hammer stop rail  55 . The hammer head  34  is in its farthest position from the string  90 . The leg  68  of the second spring  66  is away from the felt  78  of the second spring rest  72 . The damper head  44  is pressed against the string  90  by a force from the damper spring  42 . 
     Next, a case is described where a piano player depresses the key  1  in its rest position (see  FIG. 2 ). 
     The piano player depresses the key  1  in its rest position. The key  1  pivots in the clockwise direction and the tail of the key  1  rises. The tail of the key  1  lifts the heel  11 . The wippen  8  moves up with rotating on the wippen flange  10  in the counter-clockwise direction. 
     The rotation of the wippen  8  throws the spoon  9 , pushing the lower end of the damper lever  40  backward. The damper lever  40  pivots on the damper flange  41  in the clockwise direction, moving the damper head  44  off the string  90 . 
     When the wippen  8  moves up and rotates, the jack  18  moves up with the wippen  8 . In the upward motion of the jack  18 , the protruding end of the pushing-up portion  20  pushes up the pushed-up portion  27  of the hammer butt  25 . 
     After the protruding end of the pushing-up portion  20  pushes the pushed-up portion  27 , the front end of the wippen  8  keeps going up. The jack tail  19  strikes the regulating button  47 , and the regulating button  47  pushes against the jack tail  19  from the above. The jack  18  pivots on the jack flange  12  in the clockwise direction. Then, the protruding end of the pushing-up portion  20  slips out or escapes from under the pushed-up portion  27 . This disengagement is known as “let-off”. The pushing-up portion  20  that has slipped out from under the pushed-up portion  27  approaches the first spring rest  71 . The first spring  59  is bent between the pushing-up portion  20  and the first spring rest  71 . The bent first spring  59  applies torque to the jack  18 . 
     The magnitudes of the elastic modulus of the first spring  59  and the torque that the first spring  59  applies to the jack  18  are determined in order not to interfere with the let-off of the jack  18 . 
     The hammer butt  25  pivots on the hammer butt flange  26  in the counter-clockwise direction as the jack  18  pushes the pushed-up portion  27 . The hammer  32  pivots in the counter-clockwise direction along with the hammer butt  25 . When the hammer  32  pivots, the leg  68  of the second spring  66  comes into contact with the second spring rest  72  and is bent. The bent second spring  66  applies torque to the hammer  32 . The magnitudes of the elastic modulus of the second spring  66  and the torque that the second spring  66  applies to the hammer  32  are determined in order not to interfere with the hammer  32  hitting the string  90  when the piano player depresses the key  1 . Thus, the hammer  32  hits the string  90  without being interfered with the second spring  66 . This makes the string  90  vibrate and produce a note. 
     After hitting the string  90 , the hammer  32  rebounds and pivots in the clockwise direction. Then, the catcher  29  is caught by the back check  15  and the hammer  32  is stopped. At this point, the front of the key  1  has already moved to the lowest point of its travel and the tail of the key  1  has already moved to the highest point of its travel. In addition, the protruding end of the pushing-up portion  20  is located above the pushed-up portion  27  and in front of the skin  76 . 
     Next, a case is described where the piano player releases the key  1  and the front of the key  1  rises from the lowest point of its travel (see  FIG. 3 ). 
     When the piano player releases the key  1 , it pivots in the counter-clockwise direction and the tail of the key  1  starts to move down. As the tail of the key  1  moves down, the wippen  8  moves down with rotating in the clockwise direction. When the wippen  8  starts to move down, the catcher  29  disengages from the back check  15 . This allows the hammer  32  to pivot. 
     Because of the construction of the upright piano, when the front of the key  1  rises by approximately one third of the key dip distance from the lowest point of its travel to its rest position (i.e., the tail of the key  1  falls by approximately one third of the key dip distance from the highest point of its travel to its rest position), the jack tail  19  simply rests against the regulating button  47 . Thus, the force that the regulating button  47  applies to the jack tail  19  from above is equal to zero. At this time, the first spring  59  is bent between the pushing-up portion  26  and the first spring rest  71 . The bent first spring  59  applies a force to the pushing-up portion  20 . This force causes the jack  18  to pivot on the jack flange  12  in the counter-clockwise direction. As a result, the jack tail  19  is released from its contact with the regulating button  47 , and the protruding end of the pushing-up portion  20  is pressed against the hammer butt  25 . The position where the protruding end of the pushing-up portion  20  is pressed against is on the front surface of the hammer butt  25 . More specifically, this position is located above the pushed-up portion  27  in the area where the skin  76  is attached. The protruding end of the pushing-up portion  20  is forcefully pushed under the pushed-up portion  27  by the force imparted by the first spring  59 . 
     When the protruding end of the pushing-up portion is forcefully pushed under the pushed-up portion  27 , the protruding end of the pushing-up portion  20  applies a force to the hammer butt  25 . This force pushes up the hammer butt  25  and the hammer butt  25  thus pivots on the hammer butt flange  26  in the counter-clockwise direction. When the hammer butt pivots, the hammer  32  also pivots in the counter-clockwise direction. When the hammer  32  pivots, the leg  68  of the second spring  66  strikes the second spring rest  72 . Then, the second spring  66  is bent between the damper stop rail  56  and the second spring rest  72 . The bent second spring  66  applies torque to the hammer  32  through the second spring rest  72 . The magnitudes of the elastic modulus of the second spring  66  and the torque that the second spring  66  applies to the hammer  32  are determined so that the hammer  32  stops its motion before the hammer  32  hits the string  90  when the piano player releases the key  1 . In this way, the second spring  66  serves to stop the pivot motion of the hammer  32  before the hammer  32  hits the string  90 . This prevents the hammer  32  from hitting the vibrating string  90  and from muting the vibration of the string  90 . 
     When the protruding end of the pushing-up portion  20  is forcefully pushed under the pushed-up portion  27 , the jack  18  engages with the hammer butt  25 . When the piano player again depresses the released key  1 , the pushing-up portion  20  pushes up the pushed-up portion  27 . 
     In other words, the piano player can depress the same key  1  again and make the hammer  32  hit the vibrating string  90  after the front of the key  1  rises by approximately one third of the key dip distance from the lowest point of its travel to its rest position. This feature permits playing of repeated notes on the single key  1 , which is comparable to grand pianos. 
     The piano player feels the fourth to sixth forces. Thus, the piano player has touch that replicates a grand piano. 
     The tip of the threaded portion of the first bolt  81  is projected out of the back of the jack stop rail  53 . The length of the projection can be changed easily. This change facilitates adjustment of the contact between the first spring  59  and the first spring rest  71 . The magnitudes of the force and torque that the first spring  59  applies to the jack  18  can also be adjusted easily. 
     The tip of the threaded portion of the second bolt  82  is projected out of the back of the hammer shank  33 . The length of the projection can be changed easily. This change facilitates adjustment of the contact between the second spring  66  and the second spring rest  72 . The magnitudes of the force and torque that the second spring  66  applies to the hammer  32  can also be adjusted easily. 
     In this embodiment, the leg  68  of the second spring  66  extends diagonally upward and forward. Instead of this, a construction shown in a first modified version in  FIG. 6  may be used. It should be noted that  FIG. 6  shows the action  7  in a perspective from the left side. In the first modified version, the leg  68  extends diagonally downward and forward. The second spring rest  72  is formed near the bottom of the hammer butt  25  of the hammer shank  33 . The second spring rest  72  rotates along with the hammer  32 . 
     The closer the second spring rest  72  is located to the rotation center (i.e., the hammer butt flange  26 ) of the hammer  32 , the slower the second spring rest  72  rotates. When the hammer  32  pivots and the leg  68  strikes the second spring rest  72 , noise is produced. As the rotation speed of the second spring rest  72  decreases, the noise becomes weaker. 
     In this embodiment, the first spring rest  71  is supported by the first bolt  81 . Instead of this, the felt  78  may be glued on the back of the jack stop rail  53 . This felt  78  serves as the first spring rest  71 . 
     In this embodiment, the second spring rest  72  is supported by the second bolt  82 . Instead of this, the felt  77  may be wrapped around the hammer shank  33 . This felt  77  serves as the second spring rest  72 . 
     In this embodiment, the first spring rest  71  consists of the base  73  and the felt  77 . Instead of this, the first spring rest  71  may have the following construction. The felt  77  is fixed to the back of the jack stop rail  53  at two points. The tip of the threaded portion of the first bolt  81  is abutted against the back of the area between the two points where the felt  77  is fixed. This felt  77  serves as the first spring rest  71 . 
     The second spring rest  72  may have the following construction. The felt  78  is fixed to the back of the hammer shank  33  at two points. The tip of the threaded portion of the second bolt  82  is abutted against the back of the area between the two points where the felt  78  is fixed. This felt  78  serves as the second spring rest  72 . 
     In this embodiment, each of the first spring  59  and the second spring  66  may be implemented with a leaf spring. In such a case, the longitudinal extremities of the leaf spring serve as the respective legs. One leg of the leaf spring corresponds to the leg  62  of the first spring  59  of the leg  67  of the second spring  66 . The other leg of the leaf spring corresponds to the leg  63  of the first spring  59  or the leg  68  of the second spring  66 . The part of the leaf spring near the leg corresponding to the leg  62  or the leg  67  is curved to a greater degree than other part of it. This large curve corresponds to the coil member  60  of the first spring  59  or the coil member  61  of the second spring  66 . 
     In this embodiment, the leg  62  of the first spring  59  may be embedded in an additional rail provided between the action brackets, the jack stop rail  53 , or the regulating rail  48 . In such a case, the first spring rest  71  is provided in front of the pushing-up portion  20 . 
     In this embodiment, the leg  67  of the second spring  66  may be embedded in the main action rail  4 . This facilitates change in length of the leg  68 , which in turn facilitates adjustment of the second spring  66 . In addition, the leg  67  may be embedded in an additional rail provided between the action brackets. 
     In this embodiment, the leg  67  of the second spring  66  may be embedded in the hammer core  35 , the hammer shank  33 , or the hammer butt  25 . In such a case, the second spring rest  72  is provided on an additional rail provided between the action brackets, the front surface of the damper stop rail  56 , or the main action rail  4 . 
     In this embodiment, the skins  75 ,  76  may be made of a woven fabric such as a wool fabric, a non-woven fabric, or a flexible resin. In addition, the felt  77 ,  78  may be replaced with leather, a woven fabric such as a wool fabric, a non-woven fabric or a flexible resin. 
     An action  7 A according to a second modified version is shown in  FIG. 7 .  FIG. 7  shows the action  7 A in a perspective from the left side. 
     The action  7 A is different from the aforementioned action  7  in the following points. 
     As shown in  FIG. 7 , the action  7 A does not have a jack stop rail and a regulating screw for the jack stop rail. 
     As shown in  FIGS. 8 and 10 , a groove  21  is formed in the front surface of the pushing-up portion  20  of the jack  18  at the upper end thereof. The groove  21  is continuous in the longitudinal direction of the pushing-up portion  20 . The groove  21  serves as the first spring rest  71 . The pushing-up portion  20  is the member that has the first spring rest  71 . 
     As shown in  FIG. 9 , the first spring  59  has the coil member  60  and two legs  62 ,  63 . One end of the coil member  60  is connected to the leg  62  and the other end of the coil member  60  is connected to the leg  63 . The leg  62  is embedded in the upper surface of the regulating rail  48 . The regulating rail  48  is the member that has the first spring  59 . The end of the leg  63  is a free end. The end  63 T of the leg  63  is curved as an arc. The thickness of the leg  63  is slightly smaller than the width (i.e., the length in the right-and-left direction) of the groove  21 . A part of the end  63 T is abutted against the bottom of the groove  21 . 
     When the key  1  is in its rest position, the leg  63  extends diagonally upward and backward from the coil member  60 . 
     A felt  78 A is wrapped around the upper end of the hammer shank  33 . The felt  78 A serves as the second spring rest  72 . The hammer shank  33  is the member that has the second spring rest  72 . 
     As shown in  FIG. 9 , the second spring  66  has the coil member  61  and two legs  67 ,  68 . One end of the coil member  61  is connected to the leg  67  and the other end of the coil member  61  is connected to the leg  68 . The leg  67  is embedded in the damper stop rail  56 . The leg  68  has an angled “7” shaped end. The angled “7” shaped end of the leg  68  has a width (i.e., a length in the right-and-left direction) that is equal to or larger than the thickness of the hammer shank  33 . 
     When the hammer shank  33  is in contact with the hammer stop rail  55 , the leg  68  extends diagonally upward and forward from the coil member  61 . 
     Other components of the action  7 A are same as those in the action  7 . 
     A part of the end  63 T of the leg  63  of the first spring  59  is housed in the groove  21  in the pushing-up portion  20 . When the first spring  59  is bent, the end  63 T slips in the groove  21  in the longitudinal direction of the pushing-up portion  20 . When the first spring  59  is bent, the end  63 T is not deviated from the first spring rest  71 . 
     Other operations and effects of the action  7 A are similar to those achieved by using the action  7 . 
     INDUSTRIAL APPLICABILITY 
     The method of operating the action of an upright piano according to the present invention is useful as a method by which the performance of an upright piano is improved. In addition, the action of an upright piano according to the present invention is useful as a construction by with the performance of an upright piano is improved. 
     DENOTATION OF SYMBOLS AND REFERENCE NUMERALS 
     
         
           1  keys 
           4  main action rail 
           7 ,  7 A action 
           8  wippen 
           10  wippen flange 
           12  jack flange 
           15  back check 
           18  jack 
           19  jack tail 
           20  pushing-up portion 
           21  groove 
           25  hammer butt 
           26  hammer butt flange 
           27  pushed-up portion 
           29  catcher 
           32  hammer 
           33  hammer shank 
           34  hammer head 
           35  hammer core 
           39  damper 
           47  regulating button 
           53  jack stop rail 
           56  damper stop rail 
           59  first spring 
           62 ,  63  leg of first spring 
           66  second spring 
           67 ,  68  leg of second spring 
           71  first spring rest 
           72  second spring rest 
           81  first bolt 
           82  second bolt 
           90  strings