US1992939A - Piano action - Google Patents

Description

' March 5, 1935. Q H DASENBRQOK 1,992,939

PIANO ACTION Filed May 6, 195s 26 a., ful v Quim dl'romgg' Patented Mar. 5, 1935 UNITED STATES y 1,992,939 PIANO ACTION Charlesk H. Dasenbrook, Rockford, Ill.assgnor to Thayer Action Company, Rockford,` Ill., a.

corporation of Illinois Application May s, 1933, serial No. 669,643

l 7 Claims.

This invention relatesgenerally to improvements in piano actions and the general object is to simplify and reduce the cost of manufacture thereof through the use of a spring arranged in a novel manner to replace and perform the functions of a number of springs used in ordinary action constructions. i

The invention also resides in the particular location of the spring by which simplicity and compactness in construction are obtained as well as the proper degree and relation of the spring elects for controlling the repetition action and the recovery of the jack.

A further object is to provide a novelly arranged stop for cushioning the motion of the jack.

Other objects and advantages of the invention will become apparent from the following detailed description taken in connection with the accompanying drawing, in which Figure l is a fragmentary vertical sectional view through a grand piano action embodying the novel features of the present invention, the relation of the parts after back-checking of the hammer being shown in dotted outline.

Fig. 2 is a perspective view 'of thev repetition spring.v

Fig. 3 is a fragmentary perspective view of one end portion ofthe repetition lever.

Fig. 4 is a perspective under side view of the repetition lever illustrating the manner of applying the cushion pads thereto. p

Referring now to the drawing, 5 represents the conventional form of grand piano key lever carrying a capstan screw 6 which engages a whip 7 and throws the same upwardly upon depression of the key. The whipis pivoted at one end on a rail 8 and at its other end pivotally supports a bell-crank lever or jack comprising upwardly eX- tending arm 9 which engages at its upper end with a leather-surfaced butt knuckle 10 on a hammer 11 pivoted at l2. Another arm` 13 of the jack projects substantially at right angles to the arm 9 adjacent the jack pivot 14. In the upward movement of the whip, the arm 13 engages the usual regulating button 15 causing the jack to be withdrawn from engagement with the knuckle as the hammer approaches the piano string.

To yieldably sustain the weight of the hammer and assist in the recovery of the jack beneath the knuckle upon release of the key, the present invention contemplates the use of a wooden repetition lever 16 pivoted intermediate its ends on the upper end of a post 17 rigid with and upstanding from the intermediate portion of the whip '7. At

itslower end, the lever 16 carries the usual cush-.

ioned regulating button 18 adapted to engage the whip and limit the swing of the lever in one direction relative to the whip. The opposite end of the lever is substantially wider and adapted to bear upwardly against the butt knuckle 10 on opposite sides of the jack arm 9 which projects freely through a longitudinally extendingslot 19 cut in the lever. Upward movement of the repetition lever is limited by engagement of a cushion 20 with a regulating button 21 supported by the rail 22 on which the hammer 11 is pivoted.

Movement of the jack in opposite directions is limited by cushion pads 23 and 24 attached to the lever 16 and located adjacent opposite ends of the slot 19. To avoid the costly operation of squaring the ends of the slot and to simplify the attachment of the cushions, the invention contemplates a construction of the lever in a manner such as to permit the cushioning material to be appliedin the form of strips 25 to a plurality of the levers 16 laid side by side as shown in Fig. 4, the strips being later severed to form the two cushion pads 23 and 24 upon each lever. For this purpose, the slot 19 is of a length substantially greater than the spacing of the cushion stops and mayV have rounded ends. The lever 16 iscut out on its under side to form a transverse groove preferably, extendingcompletely across the lever and dened by opposed shoulders 26 to which the cushion strips 25 are secured by a suitable adhesive. Then the strips 25 are severed between the adjacent levers forming the individual cushions providing opposed stop surfaces disposed on opposite sides of the jack arm 9 and spaced apart a distance substantially less than the length of theslot 19.

The presentk invention contemplates the use of a single spring for exerting on the jack a force for swinging the same in beneath the knuckle 10 upon release of the key 5 and also for vexerting on the repetition lever a force of relatively greater magnitude for sustaining the weight of the hammer during such recovery of the jack. Rather critical values must be established for these forces in order to cause rapid recovery of the jack beneath theknuckle without danger of the knuckle being thrownV back against the string as an incident to such recovery or the touch of the key increased noticeably during withdrawal of the jack.

The proper values of the forces and the properratio between them is obtained in the present instance through the use of a. spring of the torsion type formed from a piece of resilient Wire having its intermediate portion wound to form a coil 27 of approximately two and one-half turns disposed in a vertical slot 28 cut in the lever 16. I-Ierein the coil 27 is supported by a pivot in the form of a brous cord 30 extending transversely through the lever and located adjacent the post between the pivot 29 and the adjacent end of the jack slot 19. One end 3l oi the wire projects from the coil 27 along the lever toward the jack and bears upwardly against the lower end of an adjustable screw 32 threading downwardly through a hole in the lever. In the present instance, the other end 33 oi the wire is substantially straight projecting downwardly and rearwardly from the coil to a point adjacent the jack pivot and making an angle of approximately thirty degrees with the horizontal.

The extreme end portion of the spring arm 33 is connected to the jack arm 9 in a manner such that a :torce of the proper critical magnitude will be exerted by the jack on the knuckle 10 without necessitating any provision for adjustment of this force, without danger of the connection interfering with the movement of the jack or causing the force to be varied to an objectionable degree in such movement, and without requiring any special or complicated construction of the jack. To form such a connec tion1 the arm 9 of the jack is made substantially straight and the end of the spring arm 33 is left substantially straight and projected over a shoulder formed on the jack arm in a position such that the downwardly directed force applied by the spring will act eccentrically or the jack pivot and tend to swing the jack in beneath the knuckle 10. Herein said shoulder is formed by cutting an inclined hole 34 in the jack arm 9 a short distance above the jack pivot so that the spring arm intersects the jack arm at an acute angle and above the jack pivot le. The hole is somewhat larger in diameter than the wire and preferably inclined relative to the horizontal at a slightly greater angle than the spring arm 33 so that the latter bears downwardly on the jack arm at the forward end or the hole in all positions of the jack. From a comparison of full and dotted positions of the parts as viewed in Fig. l, it will be seen that in the swinging movement of the jack, the extreme end of the arm 33 moves transversely of the hole 3a without shifting the point of application of the force. The spring arm is also free to slide longitudinally of the hole in the movement of the jack so that the spring does not in any way interfere with the freedom of movement of the jack. The extent of such sliding movement is reduced to a minimum in the present instance and in most instances eliminated by virtue of the location of the spring pivot 27 above the lever fulcrum 29. Thus, it will be observed that as the lever is swung downwardly relative to the post as it engages the stop 21, the pivot 27 will, due to its arcuate movement, be shifted toward the jack thereby compensating for the rearward movement of the point of contact between the jack and the spring as an incident to the withdrawal of the jack which occurs simultaneously with the lever movement. Any substantial movement between the jack and the spring and resulting in objectionable friction is thus reduced to a minimum. Variation in the force on the jack is accordingly reduced to a minimum.

With the spring arm positioned and joined to the jack in the manner above described, it will be apparent that the line of action of the force applied to the jack is disposed close to the jack pivot and that this relation does not change appreciably throughout the range of movement of the jack. In view of this short moment arm, the effectiveness of the force applied to the jack is reduced to the desired low value. The eiectiveness of the force applied to the repetition lever 1G is determined in a similar way by the spacing of the lever fulcrum 29 and the spring support 30. Thus, by establishing the proper arms for the forces applied by the spring to the lever and the jack, the spring is made to act upon the repetition lever and the jack with different mechanical advantages producing the desired ratio between the force acting on the harnmer and the torce applied to the butt knuckle by the jack. Moreover, the magnitudes or these forces may be varied as desired after assembly of the action snugly by adjusting the screw 32.

From the foregoing, it will be apparent that a high degree of compactness and a marked reduction in the number and complexity oi the parts results from the use of the single spring constructed and mounted as above described. An action has thus been produced which is inexpensive to construct yet reliable and durable in operation and capable of producing the desired quick keyboard touch.

This application is a continuation in part of my pending application Serial No. 627,693, iiled August 6, 1932.

I claim as my invention:

1, In a piano action, the combination of a vertically swingable hammer having a butt knuckle, a pivotally mounted whip adapted tov be swung in the plane of said hammer by depression of a key, a jack having an elongated straight arm pivoted on the free end oi' said whip and enga-geable at its free end with said knuckle, a post upstanding from said whip intermediate the ends thereof, a repetition lever pivoted intermediate its ends on the projecting end or said post and adapted at one end to engage said knuckle upon withdrawal of said jack, a piece of resilient wire having an intermediate portion wound into a coil pivoted on said lever between said post and said jack, one end portion of said wire being secured to said lever, the other end portion extending downwardly and intersecting said jack arm at a relatively sharp angle to the horizontal, an elongated hole drilled into said jack arm adjacent the pivot and in the plane of rotation thereof inclined at an angle equal to greater than said angle of intersection, said hole loosely receiving said last mentioned end and permitting pivoting of the latter end relative to the jack.

2. In a piano action, the combination of a vertically swingable hammer having a butt knuckle, a pivotally mounted whip adapted to be swung in the plane of said hammer by depression of a key, a jack having an elongated straight arm pivoted on the free end of said whip and engageable at its free end with said knuckle, a repetition lever pivotally mounted on said whip and adapted at one end to engage said knuckle and support said hammer upon withdrawal of said jack, a piece of resilient wire having its intermediate portion coiled about a pviot on said lever between the lever pivot and said knuckle, said wire having one end secured to said lever and another substantially straight uncoiled end portion extending downwardly at an angle to said jack arm, a shoulder On said arm against which the extreme end of said last mentioned end portion bears directly whereby to exert a force on the jack acting slightly eccentrically of the axis thereof.

3. In a piano action, the combination of a. pivotally mounted hammer having a butt knuckle, a pivotally mounted whip adapted to be actuated by depression of a key, a jack pivoted on the free end of said whip and engageable at its free end with said knuckle, a post upstanding from the central portion of said Whip, a repetition lever pivoted intermediate its ends on the projecting end of said post and adapted at one end to engage said knuckle upon withdrawal of said jack, a torsion spring supported by said lever between said post and said knuckle and having `an end portion disposed between said whip, said post, said lever and said jack, the extreme end of said portion being attached to the jack adjacent the pivot thereof and exerting thereon a force acting eccentrically of the pivot, and a cushioned shoulder on said lever acting to limit 'the movement of the jack toward said knuckle.

4. In a piano action, the combination of a pivotally mounted hammer. having a butt knuckle, a pivotally mounted Whip adapted to be actuated by depression of a key, a jack pivoted on the free end of said Whip and engageable at its freeend with said knuckle, a repetition lever pivotally supported by said Whip and adapted at one end to engage said knuckle upon withdrawal of said jack, said lever having a longitudinally extending slot through which the free end of said jack projects, a transverse shoulder projecting from said lever parallel to said jack and adjacent said slot, and a pad of cushioning material secured to said shoulder and extending completely across said lever, said pad forming a stop for said jack intermediate the ends of said slot.

5. In a piano action, the combination of a pivotally mounted repetition lever having a longitudinally extending opening in its free end disposed in the plane of movement of the lever, a jack pivotally mounted to swing in the plane of said lever and having its free end projecting through said opening, a pair of opposed parallel shoulders extending transversely of said lever and disposed on opposite sides of said jack, and pads of cushioning material secured to said shoulders and equal in length at least to the Width of said lever, said pads providing stops limiting the movement of said jack longitudinally of said opening.

6. In a piano action, the combination of a vertically swingable hammer having a butt knuckle near its pivoted end, a pivotally mounted Whip adapted to be actuated by depression of a key, a jack pivoted on the free end of said Whip and engageable at its free end with said knuckle, a post rigid with and upstanding from the central portion of said Whip, a repetition lever pivoted intermediate its ends on said post and adapted at one end to engage said knuckle upon withdrawal of said jack, a pivot on said lever between said post and said jack, and a piece of resilient wire having an intermediate portion wound into a coil around said pivot, one end portion of said wire being secured to said lever, and the other end portion extending downwardly to a point adjacent the fulcrum of the jack and exerting a force on the latter tending to swing the same in under said knuckle, said pivot being located on said repetition lever above the fulcrum thereof whereby the pivot will be shifted toward said jack in the swinging movement of the lever relative to said post.

7. In a piano action, the combination of a pivotally mounted hammer having a butt knuckle, a pivotally mounted whip adapted to be actuated by depression of a key, a jack pivoted on the free end of said whip and engageable at its free end with said knuckle, a repetition lever pivotally supported by said whip and adapted at one end to engage said knuckle upon withdrawal of said jack, said lever having a longitudinally extending slot through which the free end of said jack projects, and a pad of cushioning material secured to said lever and extending across the entire Width thereof, said pad forming a stop for said jack intermediate the ends of said slot.

CHARLES H. DASENBROOK.

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