US3680426A

US3680426A - Piano keyboard with magnetic key control

Info

Publication number: US3680426A
Application number: US159369A
Authority: US
Inventors: Earl E Fry
Original assignee: Individual
Current assignee: Individual
Priority date: 1971-07-02
Filing date: 1971-07-02
Publication date: 1972-08-01
Anticipated expiration: 1989-08-01

Abstract

A magnetic piano keyboard assembly comprising a plurality of pivotally mounted piano keys each having a permanent magnet mounted on its bottom surface adjacent a corresponding stationary magnetic member which is adjustably fastened to the keyboard bed, each permanent magnet coacting with a corresponding stationary magnetic member to aid in the depression of the key, providing lighter touching pressure and faster repetitive action. One end of each key is biased in a downward direction by a leaf type balance spring or finger which is adjustable to increase or decrease the amount of tension to assure adequate key return forces and to balance the key, such that a desired amount of touch pressure may be set to meet the individual player''s desires. The adjustment of the leaf springs may be overridden by way of a sustained pedal connection which may be actuated by the player to increase the leaf spring forces affecting key balance during actual playing.

Description

United States Patent Fry [54] PIANO KEYBOARD WITH MAGNETIC KEY CONTROL [72] Inventor: Earl E. Fry, 400 1/2 S. 5th St., Oregon, 111. 61061 [22] Filed: July 2, 1971 [2]] App]. No.: 159,369

2,767,607 10/1956 Barone ..84/l.28

FOREIGN PATENTS OR APPLICATIONS 390,213 4/1933 Great Britain ..84/439 Primary Examiner-Richard B. Wilkinson Assistant Examiner-Lawrence R. Franklin 15] 3,680,426 [4 Aug. 1, 1972 [5 7] ABSTRACT A magnetic piano keyboard assembly comprising a plurality of pivotally mounted piano keys each having a permanent magnet mounted on its bottom surface adjacent a corresponding stationary magnetic member which is adjustably fastened to the keyboard bed, each permanent magnet coacting with a corresponding stationary magnetic member to aid in the depression of the key, providing lighter touching pressure and faster repetitive action. One end of each key is biased in a downward direction by a leaf type balance spring or finger which is adjustable to increase or decrease the amount of tension to assure adequate key return forces and to balance the key, such that a desired amount of touch pressure may be set to meet the individual players desires. The adjustment of the leaf springs may be overridden by way of a sustained pedal connection which may be actuated by the player to increase the leaf spring forces affecting key balance during actual playing.

14 Claims, 6 Drawing Figures PIANO KEYBOARD WITH MAGNETIC KEY CONTROL In the past, piano keyboard assemblies, for the most part, have included spring-biased pivotally mounted keys. The depression of each such key required contact between the players finger throughout nearly the entire distance of the depression movement in order to overcome the spring forces which increased with the depression. Such, often, prevented rapid repetitive playing since each finger was required to remain in contact with each key for a longer period of time than permitted for rapid playing. a

It is an object of the present invention to provide a versatile magnetic keyboard assembly having a plurality of magnetic keys which are adjustably biased toward the undepressed position such that they may be ad justed to achieve the minimum finger playing pressure, thus providing a means which permits rapid repetitive playing without loss of musical quality.

Another object of the present invention is to provide a unique magnetic keyboard assembly having a plurality of keys each of which carries a permanent magnet which overlies a stationary magnetic element mounted to the keyboard bed and adjustable relative to each permanent magnet, such that the magnetic forces may be set to achieve the desired key balance.

It is a further object of the present invention to provide an adjustable magnetic keyboard assembly wherein a conventional control pedal is connected to a balance adjustment assembly such that the key balance may be effected during playing to provide the most desirable key touch pressure for the type of music being played.

These together with other objects and advantages which will become subsequently apparent reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout, and in which:

FIG. 1 is an elevated view of a pair of magnetic keys of the present invention in the undepressed position;

FIG. 2 is an elevational view of the keys shown in FIG. 1 in the fully depressed position;

FIG. 3 is a sectional view taken along section 3-3 of FIG. 1;

FIG. 4 is a sectional view taken along section 4-4 of FIG. 2;

FIG. 5 is an elevation of a conventional hammer and damper assembly actuated by a magnetic key of the magnetic keyboard assembly of the present invention; and

FIG. 6 is a graph illustrating the work required to depress a conventional key and magnetic key of the present invention.

Referring now, more specifically to FIGS. 1 and 2 the magnetic keyboard assembly of the present invention is generally referred to by the numeral 10, and includes a plurality of keys 1i and 12 each of which is mounted about a pivot pin 14 which is attached to a fulcrum member 16 rigidly affixed to the piano keyboard bed 18. Each piano key is provided with a permanent magnet 20 mounted on its lower surface and overlying a stationary magnetic member 22 which is adjustably fastened to the keyboard bed 18. Each of the stationary magnetic members 22 is adjustably mounted for movement relative to a corresponding permanent magnet by way of screws 24 each with an enlarged head portion 26 engaging the upper surface of screw aperture 28 to provide a lost motion connection and to maintain the magnetic member in contact with a mounting spring 30. Preferably, each magnetic member is provided with a stop cushion 32 of felt, cork or similar material which is adapted to engage the lower surface of the corresponding key when it is fully depressed, as shown in FIG. 2. The stop cushions 32 also serve to maintain an air gap or space between the permanent magnet and the stationary magnetic member, which provides better control for return of each key to the undepressed position.

The bottom surface of each key is provided with an opening or aperture 34 through which a corresponding pivot pin 14 extends. Each aperture 34 is joined by an oval shaped hollow 36 of larger dimension, such that each key is free to pivot about the fulcrum 16, without interference with its corresponding pivot pin. The depression end, or actuating end, of each key is provided with a guide slot 38 which extends upwardly into the key from its-lower surface and is adapted to accommodate a corresponding guide pin 40 to prevent lateral movement of each key and possible engagement with the adjacent keys.

The end opposite the actuating end of each key is provided with an indentation or trough 42 which accommodates a leaf spring or finger 44, one end of which is rigidly affixed to a pivotally mounted balance rail 46. Leaf spring 44 is made of a resilient material, such as tempered steel, such that it provides a force in the downward direction against the end of the key. The tension of the leaf springs may be adjusted by way of a balance lever 48 extending outwardly from the balance rail 46 and rigidly affixed thereto and having a slotted or forked portion 50 which is received by a threaded stud 52 and held in position by way of a balance spring 54 and adjustment nut 56. Balance spring 54 is of the coil compression type, its upper end portion engaging the lower surfaces of the balance lever to bias it against adjustment nut 56. By turning the adjustment nut, it can be seen that the angular position of the balance rail is changed, thus effecting the tension of each leaf spring 44 pressing against the end of a corresponding key. Thus, it is appreciated that an adjustment means is provided by which the spring forces acting upon the piano keys may be set at a level to achieve the desired balance of the keys and touch pressures, as hereinafter explained.

It is appreciated that a pedal cable 58 is connected to the balance rail 46 for pivotal movement of the balance rail through actuation of a conventional piano sustaining pedal, not shown. The pedal forces exerted on balance rail 46 through cable 58 are sufficient to overcome the forces of the balance spring 54, such that depression of the pedal permits downward movement of the forked portion 50 of the balance lever 48 against spring 54 to increase the spring forces of leaf springs 44 against the key ends. Thus, the balance of the piano keys may be adjusted by the player during the playing process.

Referring now to FIGS. 3 and 4, it can be seen how a pair of keys of a typical piano keyboard of the present The shorter key 11 corresponds to the sharp, as with a conventional keyboard. It can be seen, that the elongated guide slots 38 and oval-shaped hollows 36 prevent transverse movement of each key to avoid rubbing against the adjacent keys. Since each key is pivoted about a point which is intermediate its permanent magnet and the end engaged by the cor responding leaf spring, it is apparent that the forces of the magnet and leaf spring tend to act against each other. The importance of this relationship is hereinafter explained.

FIG. 5 illustrates the use of the magnetic keyboard assembly of the present invention with a conventional hammer and damper assembly, generally indicated by the numeral 60. It includes a pivotally mounted hammer 62 and damper member 64, each of which is adapted to engage a piano string 66 to produce the desired sounds. Hammer 62 is actuated by a pawl member 68 which is pivotally mounted to a support bar 70, which in turn is mounted for pivoting motion about a point 72 when struck by the actuating member 74 associated with each piano key. Such a conventional hammer assembly may also be provided with a pawl or jack stop 76 which prevents hammer rebound interference from the pawl or jack.

The advantages and benefits of the magnetic keyboard assembly may be best explained by referring to conventional keyboard assemblies, and to the work curves illustrated in FIG. 6. Conventional keyboard assemblies were, most often, provided with a return spring, such as leaf spring 44, or combinations thereof, such that the depression of a key required suflicient force (finger pressure) against one end of the key to overcome the spring forces. As the force F was applied through the distance d which the key was moved, a certain amount of work Wwas done. The amount of work done in applying a force F through a distance d may be generally expressed by thebasic formula W F X d. Where the forces vary throughout the distance of movement the amount of work W is generally expressed by the formula Graphically this is illustrated by the area under the curve of Force versus Distance. Generally, the forces exerted by a spring in the state of compression may be expressed by the formula F k x x, where k equals the spring constant, and x corresponds to the distance of the. compression. If the spring is a tension type spring, the forces increase as the spring ends are separated from each other. When these springs are applied to a piano keyboard assembly it can be seen that as a key is depressed, it is necessary to exert more force in order to overcome the spring forces which increase throughout the depression movement. Depending upon the springs characteristics these forces in actuality vary somewhere between the linear function F rx and a square function.

Referring to FIG. 6, the curves of the spring and magnetic forces versus distance of a key depression is illustrated, where d 0 when the key is fully depressed. Curve 8,- is thetheoretical curve according to F 10:. Position d, corresponds to the fully undepressed position of the key with a relatively small stabilizing force f, of the spring biasing the key toward the undepressed position. At the half depressed position d,, a force f, is

exerted by the spring. Similarly, in the fully depressed position (d 0) the spring exerts a force f which is approximately double f The-work required to depress a conventional key is represented by the shaded area falling under curve S The forces of attraction between each permanent magnet 20 and the corresponding stationary magnetic member 22 is dependent upon the strength and configuration of the magnetic field generated by the permanent magnet, which is determined, at least in part, by the size and shape of the permanent magnet and stationary magnetic member. By using a relatively flat permanent magnet with north and south poles oriented as shown in FIG. 3, the forces of attraction are approximately inversely proportional to the distance separating the permanent magnet from the stationary magnetic member. While stationary magnetic member 22, need not be a permanent magnet itself, the magnetic forces between the stationary and movable members may be altered to conform to the desired curves. The maximum magnetic forces of attraction, of course, will be present when the magnets are engaging, or nearly engaging each other. The curve of magnetic force versus distance of depression is indicated by M. The force, indicated by m when d 0, corresponds to when the key is in a fully depressed position. As the key is released and the magnets separate from each other, the forces of attraction are reduced substantially, such that at the fully undepressed position corresponding to d the magnetic forces of attraction are slightly less than the return spring forces. Since the direction of the magnetic forces of attraction are opposite to the spring forces, it is apparent that the amount of work required to depress the key is substantially reduced. The amount of work reduction is represented graphically by the shaded area under the curve M. Since the spring and magnetic forces are acting against each other the total work required to depress a magnetic key corresponds to the area between the M and S curves. Also, it is apparent that by adjusting the spring and magnetic forces, a combination of the forces may be arrived at which requires a minimum amount of resultant force and work to move the key from the undepressed to the fully depressed position. By adjusting m, to be slightly less than f there will be sufficient spring forces to return the key to the undepressed position, yet the force required to maintain the key in a depressed position is greatly reduced, namely to an amount equal to f,, m Thus, not only is the amount of work required to depress the key greatly reduced, but also the resultant force required for depression is greatly diminished, by the magnetic forces of attraction.

The results achieved with the magnetic keyboard assembly of the present invention may be more fully appreciated by analyzing the dynamics involved in the depression of one of the magnetic keys. Since initially the key is at rest, it is necessary to accelerate the key to move it to the depressed position. The force required to accelerate a body of mass m may be expressed by the formula F ma, where F equals the resultant forces upon the body, m corresponds to the massof the body, and a is the acceleration. Referring again to the graph of FIG. 6, it can be seen, that in order to accelerate the key the resultant forces exerted thereon must exceed the difierence between the spring forces and the magnetic forces of attraction. If the increase in speed in the downward direction is referred to acceleration, the increase in speed in the upward direction may be referred to deceleration. Once the downward accelerating force of a players finger is released from the key the return spring forces tend to decelerate return of the key toward the undepressed position. It should be notedthat at any position of depression the forces of deceleration will'be greatly reduced by the magnetic forces of attraction. Referring to FIG. 6, it can be seen that the deceleration forces (S M) are greatest near the mid-point of depression, and least near the fully depressed and fully undepressed positions. Thus, it is appreciated that once the key has been sufi'iciently accelerated near the half way position, its deceleration will be very slight, such that it will continue in the downward directionto impart the desired motion to the hammer assembly. The importance of this movement cannot be overemphasized. It permits the player to use relatively light finger pressures upon the keys, yet at the same time provides rapid playing and movement from one key to the other and still achieve the desired musical quality. Such a key action was not possible with conventional keyboard assemblies.

The means of adjustment provided with the magnetic keyboard assembly of the present invention cannot be overlooked. The spring return forces may be easily adjusted by adjustment nut 56. Furthermore, the forces of magnetic attraction may be adjusted by way of screws 24 to set the spacing between the permanent magnet and corresponding magnetic member. Together, these two adjustments permit one to actually balance the keys to achieve the most desirable key movement. Graphically, this has the effect of moving the magnetic and spring curves relative to each other. It should also be noted that the shapes of the curves may be tailored to provide the most desirous key action by changing the spring constants and altering the. permanent magnets and magnetic members.

It will be appreciated that once the spring balance and magnetic adjustments have been made, the key balance may be further afiected by pedal actuation which increases the balance spring forces due to the overriding ability of the forked portion 50 which engages the adjustment spring 54. Thus, the key balance may be readily modified, at will, by the player to achieve the best results, for the type of music being played. It is apparent that such an arrangement was not possible with conventional keyboard assemblies.

It should also be noted that stop cushions 32 assure the maintenance of an air gap or space between each permanent magnet and the corresponding magnetic member. It has been found most advantageous to maintain such an air gap, since when the magnetic members physically engage each other, the forces required to separate them may vary from one time to the next. Also, it is apparent that when each of the stop cushions is engaged by a corresponding depressed key, the spring mountings of the magnetic member provide a further cushioning effect, such that depression of the key is not significantly affected by its engagement with the stop cushion of the magnetic member. In view of the foregoing, it will be appreciated that the magnetic keyboard assembly of the present invention provides a unique, yet relatively simple means of achieving piano key balance to permit faster repetitive playing than with conventional assemblies and with a lighter finger pressure. The balancing is achieved with a relatively small number of parts which are readily adjustable to achieve the desired balance, such balance not being available with conventional assemblies.

The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.

What is claimed as new is as follows: frame,

1. A magnetic keyboard assembly comprising a key frame, at least one elongated key member mounted for movement relative to said key frame between depressed and undepressed positions, adjustable spring means biasing said key member toward one of said positions, and adjustable magnetic means biasing said key toward the other of said positions such that said spring means and said magnetic means may be adjusted to place said key member in a nearly balanced condition to reduce the work required for its movement from said undepressed position to said depressed position.

2. The assembly set forth in claim 1 wherein said magnetic means includes a pair of magnetic members, one of which is mounted to said key member for movement therewith, the other of said magnetic members being mounted to said key frame adjacent to said one magnetic member for magnetic co-action therebetween.

3. The assembly set forth in claim 2 wherein said magnetic means includes means for adjusting the spacing between said pair of magnetic members to adjust the magnetic forces therebetween.

4. The assembly set forth in claim 3 wherein at least one of said pair of magnetic members includes a permanent magnet. I

5. The assembly set forth in claim 4 wherein said means for adjusting the spacing between said pair of magnetic members includes lost motion means permitting movement of one of said magnetic members when the key is moved toward the depressed position.

6. The assembly set forth in claim 5 wherein said magnetic adjustment means includes a screw extending through an aperture in said other magnetic member, the screw having a head of larger dimension than said aperture such that it engages the magnetic member on one side of the aperture, and a biasing spring engaging the magnetic member on the opposite side of said aperture to normally hold said magnetic member in engagement with said screw head.

7. The assembly set forth in claim 4 wherein one of said magnetic members includes stop cushion means for preventing engagement with the other magnetic member when said key member is in the depressed position.

8. The assembly set forth in claim 4 wherein said spring means includes means for adjusting the spring forces imparted to said key member to adjust the balance of the key member to provide minimum key pressure to enable rapid repetitive key member actuation.

9. The assembly set forth in claim 8 wherein said key member is pivoted at a point intermediate said spring means and said magnetic means.

10. The assembly set forth in claim 9 wherein said other magnetic member includes adjustment means and underlies said key member for adjustment relative thereto.

11. The assembly set forth in claim 10 wherein said spring means includes a leaf spring engaging one end portion of said key member to bias it in the downward direction.

12. The assembly set forth in claim 11 wherein said leaf spring is connected to a pivotally mounted balance rail, said spring adjustment means pivoting said rail for adjustment of the leaf spring tension.

13. The assembly set forth in claim 12 wherein said spring adjustment means includes a fixed threaded stud member with an adjustment nut thereon, a coil spring surrounding said threaded stud, and a'balance lever having a first end connected to said balance rail and an opposite end sandwiched between said adjustment nut and said coil spring such that the leaf spring tension is adjusted by movement of said adjustment nut.

14. The assembly set forth in claim 13 together with cable means connected to said balance rail for adjustment of said leaf spring tension independent of said adjustment nut.

Claims

4. The assembly set forth in claim 3 wherein at least one of said pair of magnetic members includes a permanent magnet.

13. The assembly set forth in claim 12 wherein said spring adjustment means includes a fixed threaded stud member with an adjustment nut thereon, a coil spring surrounding said threaded stud, and a balance lever having a first end connected to said balance rail and an opposite end sandwiched between said adjustment nut and said coil spring such that the leaf spring tension is adjusted by movement of said adjustment nut.