US2913949A - Key action - Google Patents

Description

KEY ACTION Filed Nov. 15, 1957 2 Sheets-Sheet 1 3 I I v 2 FIG. 2 FIG-3 I INVENTOR.

I RICHARD LIDBLOM aria/aver United States Patent Ofiice 2,913,949 Patented Nov. 24, 1959 KEY ACTION Richard Lidblom, Brooklyn, N .Y. Application November 15, 1957, Serial No. 696,653 6 Claims. (Cl. 84-440) This invention relates to key actions suitable for keyboard musical instruments, such as accordions.

Key actions are of more than one kind. Keys usually have been returned to playing position by special return springs.

Key actions in pianos, on the other hand need to be operated by a blow of the finger to produce a percussive or hammer action, and through the hammer action eifect a desired touch. The hammer action is effective to return the key to playing position, thus doing away with the need for a special return.

Instruments that have hitherto required a special return spring have involved more or less faulty bearing structures, required special arrangements for limiting the sideways movement of keys to give proper results and caused sticking of keys in humid weather, produced accompanying noises, and produced an undesirable touch on the keys by increased spring pressure. To the skilled performer, a great increase in the spring pressure as the key goes down is undesirable.

In the accordion a full opening of the reed valve under all conditions is of importance because a partial opening of the valve adversely affects both the tone and the volume of the note of the reed.

Thus it comes about that the players finger, after overcoming the initial counter pressure of the key, should encounter a decreasing counter pressure as the key is further depressed.

According to the present invention, keys may be so mounted that no increase of counter pressure is needed, and, in fact, the counter pressure may diminish as the key is further depressed.

To this end a single spring serves the dual purpose of holding the key securely in its bearings, and of returning the key, thus giving it the desired touch.

To this end the key turns on a spring fulcrum so that counter pressure of the key lessens as the key approaches its bottom position, and the objectionable sideways movement of the keys is overcome by considerable spring pressure holding the keys by conical points or V-edges in conical cavities or grooves as the case may be.

The springs, or units holding them, are shown as assembled in depressions in a mounting bar so that the parts are readily assembled as units without special tools, and set in position.

The separate keys are readily inserted by being sprung into place. Thus all parts are made and put together at low cost and readily disassembled.

Other features and advantages will hereinafter appear.

In the accompanying drawings:

Fig. 1 shows in diagrammatic section one key action of the present invention.

Fig. 2 shows in full lines the spring and some adjacent parts on a much larger scale.

Fig. 3 shows a sectional view on the broken line 33 of Fig. 2.

Fig. 4 shows a side sectional view of a modified form of the device of Fig. 2.

Fig. 5 shows a sectional view on the broken line 5-5 of Fig. 4.

Fig. 6 shows the spring and adjacent parts of Fig. 5 as invented for convenience in assembling.

In the form shown in Fig. 1 the accordion right hand box 10 carries the usual keyboard frame 12 in which are mounted the usual black keys 13 and white keys 14.

Bracket 18, of which cross section is shown in Figs. 1 and 2, extends as such the full length of the keyboard, and is the main carrier of the key action, and common to all the keys.

For that purpose it has in its upper ledge 17 conical depressions 16, two for each key, and on its lower ledge bearing posts 27, one for each key.

In the form shown in Fig. 1, where U-shaped bar springs 20 are used, bracket 18 also carries on its lower ledge, and permanently fastened to itself, a thinner metal strip 29, Figs. 2 and 3.

The purpose of said strip, which is provided with square openings 30, one for each key, is to hold springs 20 in place after assembly, and after the keys are assembled and key action is completed to prevent springs 20 from swinging out of line, though otherwise allowing the springs free play.

In the modified form shown in Figs. 4, 5, and 6, where capped coil spring units 32 are used, bracket 40 corresponds to bracket 18, Figs. 1, 2, and 3, but has in its upper ledge and the entire length thereof a V-groove 49, in which lodge and rock V-shaped upper edges 48 of the modified part 55 of the keys 47.

Attachable to bracket 40 is a molding 42, of wood or other light material, extending the full length of the keyboard and corresponding to strip 29 in Fig. 1.

The purpose of said molding 42, which is provided with notches 41, one for each key, is to facilitate the assembling of the coil spring units, as shown in Fig. 6, and to hold said units 32, Figs. 4 and 5 in place after assembly, though allowing units 32 free play after keys are assembled, as can be seen in Figs. 4 and 5.

In the form shown in Fig. 1 each key, such as the white key 14, which may be made of wood or other light material, carries at its lower end and permanently fastened to itself a member 19, corresponding to member 55 fastened to key shank 47 in Figs. 4 and 5.

Said members 19 and 55, which carry the bearing points, are preferably made of hard material, such as steel.

The combination of member 19 and key body 14, or 55 and 47, each constitute a key unit, hereinafter called the key.

In the form shown in Fig. 1 each key, such as the white key 14, when depressed swings on two upper conical points 15, which are seated in depressions 16 on the overhanging ledge 17 of the bracket 18, more clearly shown in Figs. 2 and 3.

The depressions 16 also serve to locate the keys and hold them aligned and upright.

To hold the keys, such as 14 with its bearing points 15 in the depressions 16, each key is shown as pressed upwardly by a spring 20, shown as a flat strip bent into a pinched U-shape, so that a lower conical point 21, carried on the key, rests in a top conical depression 22 in the upper extremity 23 of the spring 20.

The spring 20, under these circumstances a great deal compressed, is held by an upwardly projecting conical point 24 that rests in a bottom conical depression 25 of the opposite extremity 26 of the spring 20.

The conical point 24 is shown as the upper end of the post 27 fixed in the bracket 18.

Assembling springs 20 is readily done by compressing them and inserting them through the openings 30 in the confining strip 29, until lower depressions 25 of springs 20 seat themselves on points 24 on posts 27, then letting the springs 20 expand until their upper arms 23 rest against upper edges of openings 30 in the confining strip 29.

Assembling of the keys, such as key 14, is readily done by placing point 21 on key 14 into upper depression 22 of spring 20, then pressing down and forward on lower end of the key 14 until its two points 15 slip into depressions 16 of elongated bracket 18.

The reverse procedure, disassembling, may be made with equal ease.

A modified spring structure 32, as shown in Figs. 4 and 5, consists of a coil of spring 33 confined between two caps 34 and 35 having conical depressions 36 and 37 to receive the conical point 38 of the key 47 and the fixed conical point 39 of upper end of a post fixed in the lower ledge of the bracket 40.

For assembling the spring structures 32 the detachable molding 42is inverted, see Fig. 6.

Caps 34 are then placed in notches 41, which are rounded at their inner ends.

. The coil springs are then dropped into caps 34.

Next the caps 35 are placed over the temporarily upper ends of the coil springs 33.

Next the bracket 4%) may be inverted and lowered to .bring its fixed points 39 against and into the conical depressions of caps 35.

Further lowering compresses all springs and brings side 51 of the bracket 40 to fit into the rabbeted face 563 of the molding 42.

Said members 40 and 42 may now be rigidly fastened one to the other by means of screws, one of which is shown as 54, Fig. 4, and the assembly arrived at may now be inverted and fastened in the instrument, as in keyboard frame 12 in Fig. 1.

The assembled spring units 32 are held in their positions by flanges 44, provided on the caps 34, which flanges catch on ledges 45 in the notches 41.

The modified keys shown in Figs. 4 and carry for upper bearing purpose V-edges 48 which rest in the V- groove 49 of the bracket 40.

For locating the keys lugs 56, one for each key and projecting from bracket 40, have been provided, and for each key a corresponding notch 57 in its upper edge 48.

Assembling of these keys is done exactly as in form shown in Fig. 1.

As shown in Figs. 4 and S the compression of spring units 32 takes place by assembling of the keys has set flanges 44 free from the ledges 45, and the notches 41, being sufficiently large,-allow the spring units free functioning.

For clarity an air valve 52, as part in an accordion, is shown in Fig. 1, as operated by a key 14.

In order to clarify further one, and the most important, advantage aimed at in the present invention, Fig. 2 may be chosen.

A line drawn in the plane of rotation of key 14 between point 24 and the axis of said rotation, which 15 represents, becomes the dead center line in respect to spring 26.

Since for clarity the features shown in the figures are somewhat distorted or exaggerated, it is seen that when key 14 is depressed and the point 21, lying in the plane of rotation, approaches dead center line, the spring is somewhat more compressed and consequently its force of expansion increased.

In practice the projection of the force line 24-21 of the spring may pass relatively closer to the axis 15 than Fig. 2 would suggest, and the arc described by point 21 is only about .3 degrees, so that the resulting final compression of the spring in depressing the key is trivial. Taking into account the comparatively great total length of the bar making up the spring, it is found that the increase in the upwardthrust of the spring is so trivial that Li -50.3.1 under thes ci cumstanc s e c s er onstant. In view of the considerable length of wire which makes up spring 33 in the form shown in Fig. 4 the same reasoning holds true for spring unit 32.

Thus it may be seen that the relative positions of points 15, 21, and 24 are such that, as key 14 is depressed and point 21 correspondingly approaches dead center line 1524, that part of the expanding force of spring 20 which tends to hold the key in raised position is caused to approach zero.

It has been found that the relative positions of points 15, 21, and 24, the relative dimensions of parts and the expanding force of the spring may be predetermined so, that for any given desired initial resistance of the key to the depressing finger and any given desired depth to which the key is depressed, any desired decreased resistance of the key at bottom position may be obtained.

Having thus described certain embodiments of the invention, what is claimed is:

1. In a non-percussion musical instrument, a frame, an openable valve controlling a musical note, a key connected to said valve and depressible to open it, a key lever carrying the key, an upper bar in said frame including depressions, an upper pivot carried by said key lever and turning in one of said depressions, an upwardly thrusting return spring, a second bar beneath said spring, an upwardly pointing pivot on said second bar against which said return spring thrusts, and a downwards pointing pivot on said key lever bearing against said spring in front of a line joining said upper pivot and said upwardly pointing pivot and swinging toward said line as the key lever is depressed.

2. In a device according to claim 1, a pair of separated .pivoting edges forming the pivot, and a projecting separating member between said pair.

3. A device according to claim 1, in which the spring is in the form of a fiat strip bent back to form two flat ends having each a conical depression adapted to receive a pivot .point.

4. In a non-percussion musical instrument, a frame, an openable valve controlling a musical note, a key connected to said valve and depressible to open it, a key lever carrying the key, an upper bar in said frame including depressions, a pair of upper pivots carried by said key lever and turning in said depressions, an upwardly thrusting return spring, a second bar beneath said spring, an upwardly pointing pivot on said second bar against which said return spring thrusts, and a downward pointing pivot on said key lever bearing against said spring in front of a line joining said upper pivots and said upwardly pointing pivot and swinging toward said line as the key lever is depressed.

5. In a non-percussion musical instrument, a frame, an openable valve controlling a musical note, a key connected to said valve and depressible to open it, a key lever carrying the key, an upper bar in said frame including depressions, an upper pivot carried by said key lever and turning in one of said depressions, an upwardly thrusting return coil spring, a second bar eneath the spring, an upwardly pointing pivot on said second bar against which said return spring thrusts, a downward ly pointing pivot on said key lever bearing against said spring in front of a line joining said upper pivot and said upwardly pointing pivot and swinging toward said line as the key lever is depressed, and end covers in the form of inverted cones on the ends of said-spring in which the said upwardly and downwardly pointing pivots rest.

6. In a non-percussion musical instrument, a frame, an openable valve controlling a musical note, a key connected to said valve and depressible to open it,. a key lever carrying the key, an upper bar in said frame including depressions, an upper pivot carried by said keylever and turning in one of said depressions, an upwardly thrusting r urn 1 sp ng, a ond. ba b neath the spring, an upwardly pointing pivot on said second. bar

flange on an end cover adapted to rest on the shelf in assembling the instrument.

References Cited in the file of this patent UNITED STATES PATENTS La Marche Aug. 19, 1930 Kostka Aug. 21, 1951 Rieschick Mar. 11, 1952 Link Oct. 2, 1956

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