US2737841A - Power assisted action mechanisms for keyboard operated instruments - Google Patents

Description

March 13, 1956 R. L. MCSHAN ET AL POWER ASSISTED ACTION MECHANISMS FOR KEYBOARD OPERATED INSTRUMENTS 4 Sheets-Sheet 1 Filed Dec. 28, 1951 FIGZ.

INVENTORS ROBERT L.. M SHAN CLARENCE H M SHAN BY( 0 QQQQ 8 "Mu. 3: W THEIR ATTORNEYS March 13, 1956 Filed Dec. 28 1951 R. L. M SHAN ET AL POWER ASSISTED ACTION MECHANISMS KEYBOARD OPERATED INSTRUMENTS FOR .4 Sheets-Sheet 2 INVENTORS ROBERT L. M SHAN CLARENCE H. M SHAN BY CAMM) SSW RAM. a- M THEIR ATTORNEYS March 13, 1956 Filed Dec. 28, 1951 R L. M SHAN ETAL POWER ASS ISTED ACTION MECHANISMS FOR KEYBOARD OPERATED INSTRUMENTS 4 Sheets-Sheet 3 INVENTORS ROBERT L. M SHAN CLARENCE H. M SHAN BYC M Q 90 E W s- QNMIQQH THEIR ATTORNEYS March 13, 1956 R. L. M SHAN ET AL POWER ASSISTED ACTION MECHANISMS FOR KEYBOARD OPERATED INSTRUMENTS 4 Sheets-Sheet 4 Filed Dec. 28, 1951 INVENTORS ROBERT L. M SHAN CLARENCE H M SHAN BY I 9 q/UL 3r W THEIR ATTORNEYS United States Patent Ofiice POWER ASSISTED ACTIUN MECHANISMS FUR KEYBQARD QPERATED INSTRUIWENTS Robert L. McS-han and Clarence H. P/l'cShan, Houston, Tex.

Application December 28, 1951, Serial No. 263,844 14 Claims. (Cl. 34-244) The present invention relates to keyboard operated instruments and more particularly to new and improved apparatus of this character which embodies simple yet highly efiec'tive power assisted action mechanisms.

It has been proposed, heretofore, to provide power assisted action mechanisms for keyboard instruments intended for manual operation. In one form designed for musical instruments such as pianos and the like, the striking hammer is provided with a curved surface which, upon manual depression of the key, is moved into frictional engagement with a rotating driving member. Apparatus of this character leaves much to be desired since the hammer motion does not follow the motion of the key so that little or no dynamic range is possible. Further, escapement mechanism must be provided for releasing the hammer from the driving member after the string has been struck, and checking mechanism is required for preventing the hammer from striking the string more than once for each depression of the key. Thus, the power assistance is obtained at the expense of dynamic range and it adds to the complexity of an already complicated instrument.

It is an object of the invention, accordingly to provide new and improved power assisted action mechanism for keyboard operated instruments which is free from the above noted disadvantages of the prior art.

Another object of the invention is to provide new and improved power assisted action mechanism for keyboard instruments in which the striking hammer tends to follow the motion of the actuating key, whereby a wide dynamic range may be achieved in the operation of the instrument.

A further object of the invention is to provide new and improved power assisted action mechanism for keyboard instruments which is capable of performing other functions now carried out by other apparatus, whereby the overall keyboard action may be materially simplified.

Still another object of the invention is to provide new and improved power assisted action mechanism for keyboard operated string instruments such as a piano, for example, in which a given force applied to a key results in a given volume of sound, regardless of whether the key is in the base or in the treble portion of the keyboard.

These and other objects of the invention are attained by interposing servomechanisms between each striking hammer and the key which actuates it such that the hammer motion tends to follow the motion of the key with some amplification of the force applied to the key. A suitable servomechanism may comprise, for example, a substantially non-elastic flexible link member connected for actuation of the hammer upon actuating of the key, which member is wrapped around a portion of the circumference of a rotating driving member. Normally, the link member slips relatively to the driving member. However, depressing a key applies tension to one end of the link memher and causes it to come into driving engagement with the driving member, so that the hammer is caused to move towards the part of the instrument to be struck.

With the foregoing construction, it will be understood 2,737,841 Patented Mar. 13, 1956 that any tendency for friction to accelerate the hammer at a rate faster than the key results in loosening the flexible link member on the driving member. Conversely, any failure of the hammer to accelerate at the same rate as the key results in tightening of the flexible link member on the driving member. This action is degenerative so that it is very stable and the hammer motion tends to follow the key motion enabling a wide dynamic range to be achieved. Further, it eliminates the necessity for the usual escapernent mechanism and reduces backcheck requirements to a minimum as will appear later.

The invention may be better understood from the following detailed description of several representative embodiments thereof, taken in conjunction with the accompanying drawings in which:

Fig. 1 is a side elevation of power assisted action mechanism for one key of a grand piano, constructed according to the present invention;

Fig. 2 is a side elevation of a modified form of power assisted action mechanism;

Fig. 3 is a view in side elevation of a preferred embodiment of the invention;

Fig. 4 is a view in side elevation showing power assisted action mechanism according to the invention applied to the key action of an upright piano; and

Fig. 5 is also a view in side elevation of another embodiment in which the power assisted action mechanism is applied to the action of a spinet.

While the power assisted action mechanism of the present invention may be applied to different forms of key operated apparatus, it will be illustrated herein as applied to actions of the type found in upright and grand pianos and spinets, for example.

in the form of the invention shown in Fig. l, a conventional piano key 19 is shown fulerumed rockably on a support member 11 which carries a post 12 extending through a bore 13 in the key 10. The key 10 is adapted to cause hammer l4 pivoted at 15 on a support member 16 to strike a piano string 1').

According to the invention, a servomechanism 1G is employed to couple the key 19 to the hammer 14. The servomechanisrn 18 may comprise, for example, a flexible, substantially non-elastic belt 19 secured at one end to an arm 21') mounted on the shank of the hammer 14 near the base thereof and at its other end to a support 21 carried by an upright post 22 secured to the key 10 between its support 11 and the rear end thereof. The belt 19 is wrapped around a cylindrical driving member 23 which may be driven at a selec ed rate or" speed by any suitable motive means as, for example,- a conventional direc cur rent motor 2.3a adjustable in speed in a conventional manner and coupled by a shaft (not shown) to the driving member 23.

The servomechanism i3 is so e 'gned that when the key it is in the normal raised posi on shown in l, the friction between the belt 19 and the driving member 23 is not suflicient to raise the hammer 14. 1* ever, as soon as the key 10 begins to be depressed, the belt 29 tightens suiiiciently to cause the hammer id to progressively follow the key motion, the phrase progressively follow being used in the sense to mean that as the key is moved in the direction of depression throughout a range, for each incremental displacement in this range, there is a corresponding incremental displacement of the hammer towards its string 17, over a major portion of its path each instantaneous position of the hammer being positively determined by the instantaneous position of the key. Purther, the design is such that a degree of force amplification is effected by the servomechanism 18. In the piano application, the force amplification may be relatively small and amplifications of from four to eight are suitable in practice.

Preferably, the belt 19 should be made of unborn calfskin reinforced against stretching with a suitable backing such as cloth, for example. The cloth backing may be provided with a coating of rubber, or other suitable material, as protection against moisture. The driving member 23 may be made of steel having a satin finish surface and approximately three-quarters of its circumference may be engaged by the belt 19. This combination of belt and driving member is very quiet in operation and has a stable coefiicient of friction which insures smooth and uniform operation. in a typical action, the driving member 23 may be polished steel, one inch in diameter and driven at 380 R. P. M., while the belt 19 may be three-eighths of an inch wide and may engage the driving member around three-quarters of its circumference, although none of these factors is critical.

To secure the greatest work function from a given belt of a given size with a given driving member speed, the belt travel must be made as large as possible. Therefore, provision should be made for a large leverage actuating the belt and a large leverage actuating the hammer. This is also desirable to insure that the effects of elasticity of the belt and its linkages upon the damping action of the servomechanism 18 will be reduced, as well as to enable the minimum size belt to be employed for a given work requirement.

It is highly desirable to reduce motor and shaft vibration to a negligible level and to this end the drive shaft for the driving member 23 should preferably be journaled in means such as olite bearings mounted in rubber or felt and the driving motor should preferably be mounted on conventional rubber vibration mounts. The axis or rotation of the driving member 23 must be accurate, otherwise the belt 19 will be thrown from its surface and will lose frictional engagement therewith. Since the belt 19 is loaded for only a short period of time, the use of a flywheel on the shaft driving thedriving member 23 is desirable and its use enables a smaller driving motor to be employed.

Instead of the rigid backcheck usually found in conventional piano actions, the mechanism shown in Fig. 1 utilizes a light spring backcheck 24 which is mounted on the key at 25.

In operation, the forward end of the key 1!} is depressed manually in the usual manner. This causes the post 22 to rotate counterclockwise about the point on which the key 10 is fulcrumed, thereby applying tension to the lower end of the belt 19. This tension is amplified in the servo mechanism 18 with the result that the hammer 14 moves upwardly towards the string 17. Preferably, the adjustment is such that when the key 10 is fully depressed, the hammer 14 will be in the position shown in dotted lines in Fig. 1, about one-eight inch below the string 17. Because of its momentum, however, the hammer 14 continues upwardly until it strikes the string 17, the belt 19 be coming loosened from the driving member 23 so as to permit this to happen.

Assuming that the key 10 is fully depressed when the hammer 14 rebounds from the string 17 and the belt 19 again tightens about the driving member 23, the servomechanism 18 now functions as a degenerative device to reduce the hammer motion to zero. This degenerative action tends to damp out any possible oscillatory movement of the hammer 14, a function now prevented in conventional actions by the usual wedging backcheck. Because there will be inevitably some elasticity in the belt 19 and the linkages attached thereto, the damping afforded by the servomechanism 18 will usually not be perfect and the purpose of the backcheck 24 is to provide a light wiping action against the back of the hammer which insure that critical damping will be achieved.

Another advantage of this degenerative action of the servomechanism 18 is that in damping the hammer rebound motion to zero it transmits but a fraction of the impact to the key 10 and to the finger of the player.

Because the servomechanism 18 allows the hammer 14 to continue to travel after the key 11? has been completely depressed, the need for the usual jack mechanism employed in present actions is entirely eliminated. The conventional jack mechanism constitutes a large part of the cost of the conventional piano action and it requires considerable attention for proper alignment. Its elimination, therefore, not only simplifies the action but reduces the initial cost and the expense of maintaining it in good working order.

Another advantage of the construction shown in Fig. l is that the key 10 needs to be released only a small amount to permit the note to be struck a second time. This is a considerable improvement over conventional mechanisms utilizing jack mechanism in which the key must rise a considerable distance before a note can be struck a second time. Hence, higher repetition rates of striking a note may be achieved.

Fig. 2 illustrates a further embodiment which is rigid and durable in construction and easily assembled and which provides easy access to all parts thereby facilitating adjustment of the mechanism. In this form of the invention, the lower end of the belt 19 is secured to an arm 26 carried by an elongated lever arm 27 pivotally mounted at 28 and a support 29. Threadedly mounted in the lever arm 27, intermediate the ends thereof, is a capstan screw 3t) having a bearing surface 31 at the lower end thereof which is adapted to engage a corresponding bearing surface 32 of graphited leather, for example, secured on the rear portion of the key 10. Otherwise, the construction is similar to that shown in Fig. l, and the manner of operation is essentially the same.

Fig. 3 illustrates a further modification in which the rebound of the hammer is entirely checked by the servomechanism so that there is no need whatsoever for any backcheck. In the embodiment shown in Fig. 3, the lower end of the belt 19 is secured to a lever arm 33 pivotally mounted at 34 on a support rail 35. A capstan screw 36 mounted on key 10 between pivot 12 and the rear portion of the key engages a graphited leather surface 37 formed on the lever 33. The upper end of the belt 19 is secured to an arm 38 which is pivotally mounted on the shank of the hammer arm 14 at the point 39 and which is normally urged in the clockwise direction by suitable means such as a leaf spring 40 mounted at 41 on arm 38.

Formed on the arm 38 is a pawl 42 adapted to be retained by a catch member 43 formed at one end of arm 44 which is pivotally mounted on the shank of the hammer arm 14 at 45. The arm 44 is normally urged in the counterclockwise direction by the leaf spring 40, one end of which may engage a depression 46 in arm 44. The hammer arm 14 in the rest position normally engages a hammer rest rail 47, at which time the pawl 42 is locked by the catch 43 so that when tension is applied to the arm 38 by the upper end of the belt 19, the hammer 14 is moved upwardly towards the string 17.

The hammer 14 is pivotally mounted at the point 48 on the support rail 35. Secured to the rail 35 is an adjustment screw rail 49 on which is mounted an adjustment screw 50 carrying a support 51 for a bearing surface 52 of felt or other suitable material against which the upper end of the arm 44 is adapted to be moved when the hammer 14 is raised, as will be described in detail below.

In operation, depressing the key 1% applies tension to the lower end of the belt 19, the upper end of which applies increased tension to the arm 38. This causes the hammer 14 to move upwardly to the string, this position being shown in Fig. 3. Prior to reaching the position shown, the arm 44 engages the bearing surface 52 and begins to disengage the catch 43 and the pawl 42, the two being shown at the point of disengagement in Fig. 3.

Further travel of the hammer 14 occurs as the string 17 is displaced and the hammer felt is compressed. The depression of the key for the position of the mechanism shown is approximately 80%. Further depression of the key It causes the arm 38, which is now free of the catch 43 to move in the counterclockwise direction.

Rebound of the hammer 14 from string 17 is checked when the hammer reaches the position '53 shown in dotted lines at which time the arm 38 tightens belt 19 with the key 10 fully depressed.

Compression spring 40 is designed so that it does not have sufficient compression to raise the hammer 14 above the position 53. The arm 44 is in engagement with the bearing surface 52 for all positions of the hammer 14 between the dotted line position 53 and its point of impingement with the string 17, so that a mild damping action results.

When the key 10 is released aproximately the spring 40 overcomes the force exerted by the belt 19, permitting the pawl 42 to be retained by the catch 43, the recess adjoining the latter being lined with felt '54 for quiet operation. To this end, the pivotal torque exerted by the spring 46 on the arm 44 is designed to be less than the torque applied to the arm 38.

Fig. 3 also illustrates optional means for altering the key pressure, if desired. This may comprise, for example, a shaft 55 which can be manually rotated. a few degrees in either direction and locked by any suitable means (not shown), and a leaf spring 56 attached to shaft at 7 and engaging key it} in recess Clockwise adjustment of the shaft lightens the required key pressure, while counterclockwise adjustment increases the key pressure. The eifect of the spring 56 must be very mild as the feel of a strong spring return on the fingers of the player is objectionable.

When present forms of action are modified to include action mechanism according to the invention, it may be necessary because of the lightness of the latter to weigh the keys by suitable means such as a lead weight plug 59, for example, in order to secure proper balance.

The key pressure should be determined primarily by proper balance or by the use of weights, if necessary. A i20% variation of key pressure may safely be secured by adjustment of a long slender spring 56 as shown.

The action shown in Figure 3 is the preferred form of the invention. it insures that no matter how lightly or slowly the key is struck in an effort to secure a very soft note the note will never miss.

The rate of repetition can be exceedingly rapid because of the early reset feature of the action. With this action, the note sounds at 80% depression of the key and key shock due to rebound check of the hammer is substantially reduced. The mechanism and adjustments are simple and reliable yet a very great dynamic volume range can be achieved as a result of the force amplification effected by the servomechanism. Because of this force amplification, the hammer felts may be softened to secure a fuller, richer tone, a feature impractical of accomplishment with prior art actions because of the additional manual effort required to secure increased volume.

As indicated, the mechanism shown in Fig. 6 completely checks the rebound of the hammer without the necessity for a backcheck of the conventional type.

Figs. 4 and 5 illustrate how the servomechanism action of the invention can be applied to a conventional upright piano and to a spinet, respectively. in Fig. 4-, the servomechanism is similar to that shown in Fig. 1, except that the post 22 and the backcheck 2 4 are mounted on the rocking arm 66 which is commonly used in conventional upright piano actions. Accordingly like reference characters have been used to designate like parts. This figure will be self-explanatory and a detailed description thereof will not be necessary.

in the modification shown in Fig. 5, the lower end of the belt 19 is secured to one arm of a bell crank 61 which is pivoted at a point 62 on the rocking arm 63 in a conventional spinet action, and the arm 64 of which is normally urged upwardly by a compression spring 65 disposed in a recess 66 formed in the arm 63, as shown. Also, a light spring backcheck 67 is provided on the arm 63 for insuring critical damping in combination with the degenerative action of the servomechanism 18 as described above. The spring backcheck 67 is so placed that when it is engaged by pad 68 on the hammer 14, it becomes wedged towards instead of away from the hammer. As in the embodiment shown in Fig. 1, when the hammer 14 returns to a position approximately oneeighth of an inch from the string 17, after the latter has been struck, the belt 19 tightens around the drum 23 and, in combination with the spring backcheck 67, dampens the movement of the hammer 14 to zero.

By decreasing the belt width and/or the angle of contact with the driving member towards the treble end of the action as the hammer weights diminish, it is possible to obtain a uniform key striking force for a given volume of sound from the base to the treble end of the instrument.

It is also possible to utilize the servomechanism to achieve soft pedal action. This may be accomplished by providing means either to vary the length of belt in contact with the driving member or to alter the speed of rotation of the latter, as, for example, by varying the speed of the motor 23a. A selective adjustment of the type described causes a change in the "alue of the amplification factor between the force imparted to a key and the force with which a hammer strikes its string.

If desired, weights may be slidably mounted on the rear portions of the keys to enable some adjustment of the pressure required to actuate the keys. By proper adjustment of these weights the action may be adjusted to suit the desires of the player.

From the foregoing description, it will be understood that the invention provides novel and highly effective power assisted action mechanism for keyboard operated instruments. By utilizing a servomechanism to couple the key to the hammer, force amplification can be achieved and the same functions of existing piano actions can be obtained more effectively without the necessity for the relatively complex mechanisms now employed for this purpose. The invention thus provides a keyboard operated action which is simple and highly etfective in operation and which enables higher repetition rates to be achieved than has been possible heretofore.

The several specific embodiments disclosed herein by way of illustration are obviously susceptible of modification within the spirit of the invention. For example, servomechanisms according to the invention may be employed to actuate both the hammers and the string dampers although this is not deemed desirable beacuse some weight is needed to secure a fast key return. Also in the case of player pianos, the servomechanism may be operated by miniature pneumatic devices, thus enabling a reduction in the size of the pump, player roll, and air system to be achieved. Other modifications will be apparent to those skilled in the art. The invention, therefore, is not to be thought of as restricted to the specific forms described but rather as broadly as the terms of the following claims will permit.

We claim:

'1. In a keyboard operated instrument, the combination of a hammer, an actuating key, means including a flexible link member continuously connecting the key to the hammer, and a driving member disposed to impart frictional force to said link member upon actuation of the key to cause the hammer to progressively fol ow the motion of the key during movement of the key in one direction.

2. In a keyboard operated instrument, the combination of a hammer, an actuating key, a rotatable driving member, and a flexible, substantially non-elastic belt continuously connecting the key to the hammer and wrapped around at least a portion of said driving member.

3. In a keyboard operated instrument, the combination of a hammer, an actuating key, a rotatable driving member, motive means for rotating said driving member, 21 flexible, substantially non-elastic belt wrapped around at least a portion of said driving member, leverage means coupling one end of said belt mechanically to said hammer, and leverage means coupling the other end of said belt mechanically to said key, whereby the hammer will progressively follow the motion of the key during movement of the key in one direction.

4. In a keyboard operated instrument, the combination of a hammer, an element to be struck by the hammer, an actuating key, and servomechanism continuously coupled to the hammer and the key for causing the hammer to progressively follow the motion of the key over at least a portion of the path travelled by said hammer during movement of the key in one direction.

5. In a keyboard operated instrument, the combination of an actuating key, an element to be struck in response to actuation of said key, a hammer mounted for pivotal movement over a path extending from a position of rest to said element to be struck, means including a flexible link member coupling the key to the hammer, and a driving member disposed to impart frictional force to said link member upon actuation of the key to cause the hammer to progressively follow the motion of the key over at least a substantial portion of said path While permitting travel of the hammer over the remainder of said path independently of the key.

6. In a keyboard operated instrument, the combination of an actuating key, an element to be struck in response to actuation of said key, a hammer mounted for forward pivotal movement towards said element to be struck and for return movement to a position of rest, means including a flexible link member coupling the key to the hammer, and a driving member disposed to impart frictional force to said link member during the return of said hammer to its position of rest after striking said element and while said key is still actuated, so as to check the movement of said hammer as it approaches its position of rest.

7. The combination defined in claim 6 together with yielding auxiliary means for further checking the movement of said hammer as it approaches its position of rest.

8. In a keyboard operated instrument, the combination of an actuating key, an element to be struck in response to actuation of said key, a hammer mounted for pivotal movement towards said element to be struck and for return movement to a position of rest, means including a flexible link member coupling the key to the hammer, and a driving member disposed to impart frictional force to said link member upon actuation of the key, to cause the hammer to progressively follow the motion of the key over a substantial portion of the path travelled by the hammer in moving from its position of rest to the element to be struck, while permitting travel of the hammer over the remainder of said path independently of the key, said driving member also being disposed to impart frictional force to said link member during the return of said hammer to its position of rest after striking said element and While said key is still actuated, so as to check the movement of said hammer as it approaches its position of rest.

9. In a keyboard operated instrument, the combination of a hammer, an actuating key, a rotatable driving member, a flexible, substantially non-elastic belt connecting the key to the hammer and wrapped around at least a portion of said driving member, said driving member upon rotation, by frictional engagement of said portion with said belt, causing said hammer to progressively follow the motion of said key with increase of force by an amplification factor and means for selectively adjusting the value of said amplification factor.

10. In a keyboard operated instrument, the combination of a hammer pivotally mounted on a support and having an arm on the shank thereof, a key, a lever arm mounted for turning movement about a pivot, means for moving said pivot in accordance with the movement of said key, spring means biasing said lever arm in one direction, a rotatable driving member, a flexible, substantially non-elastic belt connected to the arm on said hammer and to said lever arm and being Wrapped around at least a portion of said driving member, and yielding backcheck means adapted to be engaged by means on said hammer during the return stroke thereof.

11. In a keyboard operated instrument, the combination of a hammer pivotally mounted on a support and having an arm on the shank thereof, an actuating key, a lever arm pivotally mounted on a support, a rotatable driving member, a flexible, substantially non-elastic belt connected to the arm on said hammer and to said lever arm and being wrapped around at least a portion of said driving member, actuator means interposed between the key and said lever arm, and yielding backcheck means adapted to be engaged by a portion of said hammer during the return stroke thereof.

12. In a keyboard operated instrument, the combination of a hammer pivotally mounted on a support and having an arm pivotally mounted on the shank thereof, releasable means locking said arm to the hammer shank, an actuatable key, a lever arm pivotally mounted on a support adjacent said key, stop means for releasing said locking means when said hammer reaches a predetermined point in its travel, a rotatable driving member, a flexible, substantially non-elastic belt secured to the arm on said hammer and to said lever arm and being Wrapped around at least a portion of said driving member, and an actuator member carried by said key for actuating said lever arm.

13. In a keyboard operated instrument, the combination of a hammer pivotally mounted on a support and having an arm pivotally mounted on the shank thereof, latch means pivotally mounted on said hammer shank and engageable with a portion of said arm to lock the latter to said hammer shank, yielding means normally maintaining said latch means and said arm portion engaged, an actuatable key, a lever arm pivotally mounted on a support adjacent said key, a rotatable driving member, a flexible, substantially non-elastic belt secured to the arm on said hammer and to said lever arm and being Wrapped around at least a portion of said driving member, an actuator member pivotally mounted on said key for actuating said lever arm, and stop means adapted to engage said latch means when said hammer reaches a predetermined point in its travel for disengaging said latch means from said arm portion.

14. In a keyboard operated instrument, the combination of a hammer pivotally mounted on a support and having first and second arms pivotally mounted thereon, cooperating means on said first and second arms for locking the same together and to the hammer, spring means normally urging said arms into the locked position, a lever arm pivotally mounted on a support, a key having an actuator member thereon for actuating said lever arm, a rotatable driving member, a flexible, substantially non-elastic belt connected to one of said first and second arms and to said lever arm and being wrapped around at least a portion of said driving member, and stationary stop means adapted to engage the other of said first and second arms for unlocking said first and second arms at a predetermined point in the travel of said hammer.

References @ited in the file of this patent UNITED STATES PATENTS

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