US2881651A - Electronic piano - Google Patents

Description

A ril 14, 1959 c. w. ANDERSEN ELECTRONIC PIANO 3 Sheets-Sheet 1 Filed June '7, 1954 April 14, 1.959 c. w. ANDERSEN 2,831,651

ELECTRONIC PIANO Filed June 7, 1954 3 Sheets-Sheet 2 J66 J54 J53 J68 J96 v J55 J Kg J30 J10 J50 J5 J 63 @5 J50 j/ Z Z April 14, 1959 c. w. ANDERSEN ELECTRONIC PIANO 3 Sheets-Sheet 3 Filed June 7, 1954 United States Patent ELECTRONIC PIANO Clifford W. Andersen, De Kalb, Ill., assignor to The Rudolph Wurlitzer Company, North Tonawanda, N .Y., a corporation of Ohio Application June 7, 1954, Serial No. 434,845

Claims. (Cl. 84-1.14)

This invention is concerned generally with the production of music, and more particularly with an electronic piano.

It is an object of this invention to provide a new and improved electronic piano, specifically one using percussively vibrated reeds as tone generators.

A more particular object of this invention is to provide a single support bar or structure forming a single rigid massive support for the reeds and pick-ups for precluding damping of vibrations or the introduction of extraneous vibrations by said support.

A further object of this invention is to provide means for mechanically insulating the reed and associated pickup support means from the remaining parts of an electronic piano to prevent transmission of vibrations to the support.

A further object of this invention is to provide an electronic piano having vibratile reeds and associated pickup means as tone generators, wherein the pick-up means comprise a tapered bar or a series of stepped bars for proper cooperation with reeds of varying physical size.

Yet another object of this invention is to provide an electronic piano having vibratile reeds and cooperating pick-up means forming tone generators wherein only a single piece of shielding is needed for the tone generators.

Other and further objects and advantages of the present invention will be apparent from the following description when taken in connection with the accompanying drawings wherein:

Fig. 1 is a perspective view of a portable electronic piano constructed in accordance with the principles of my invention, a part thereof having been broken away;

Fig. 2 is an enlarged cross-sectional view through the piano taken substantially along the line 22 in Fig. 1;

Fig. 3 is an enlarged top view partially in section of a portion of the piano as taken substantially along the line 3-3 in Fig. 2;

Fig. 4 is an enlarged view partially in section of the piano tone generating mechanism as taken substantially along the line 44 in Fig. 3;

Figs. 5-7 are enlarged sectional views showing the cooperation of the pick-up means and reeds of different sizes as taken along the lines 55, 6-6, and 7-7 respectively in Fig. 8;

Fig. 8 is a top view of the reeds, pick-up means, and supporting means;

Fig. 9 is a perspective View of the reed and pick-up support means or bar;

Fig. 10 is a perspective view of a corner of the shield illustrating the attachment means thereof; and

Fig. 11 is a perspective view'of some the reeds and a portion of the pick-up means in accordance with a preferred embodiment of the invention.

Referring first to Figs. 1-3 for a general understanding of the invention, there will be seen an electronic piano designated generally by the numeral 20 including a case 22 of generally rectangular outline. By way of specific example, the case is on the order of two feet from front Patented Apr. 14, 1959 to rear, is of substantially less than a foot in height, and is on the order of three feet in length for a 61 note keyboard. The case includes a bottom 24, end walls 26, a rear wall 28, and a top 30 extending parallel to the bottom 24, but terminating short of the front edge thereof. A lid or keyboard cover 32 is hinged to the front of the top 30 as at 34 and is provided with an angularly disposed edge fiange 36. When the cover is in lowered position as shown in Fig. 1 and in full lines in Fig. 2, it extends downwardly at an angle across the keyboard 37, and the depending flange 36 closes on a shallow upstanding front wall 28. Toggle type fasteners 40 are provided on the flange 36 and front wall 38 for holding the cover in closed position, and a handle 42 is provided on the front wall 38 for carrying the piano. The keyboard cover 32 is adapted to tilt up generally to the position shown in Fig. 2, and in this position c0- operates with a shelf or tray 44 above the keyboard to form a music rack.

The piano is provided with an electronic amplifier 44 of suitable design, and this amplifier is connected to operate a loudspeaker 46 opening upwardly through an opening in the top of the cabinet, said opening being covered by a grille or plate 48 having a plurality of slots therein. The end walls 26 of the cabinet are provided with horizontal slots serving as finger grips for lifting the cabinet, and also serving as ports for relieving back pressure on the speaker.

In addition to being connected to the loudspeaker 46, the amplifier is connected to a pair of jacks 52 above the right end of the keyboard. Earphone plugs may be associated with these jacks, and the connections are such that when one of the jacks is used, sound will be produced only in the earphones, while when the other jack is used the sound will be reproduced both by the loudspeaker and by the earphones. Electric power for the piano is provided by a power line or cord 54, which preferably is detachably connected to the piano by any suitable plug 56 to render the piano more readily portable.

The piano case 22 is of such a size that it readily can be placed on a table or desk for playing, but it also is contemplated that in some instances, such as in semiportable installations, wrought iron legs 58 of the type popular for interior decorating may be secured to the bottom of the piano case by any suitable means such as screws.

The keyboard 37 of the piano comprises a plurality of keys 60, including white keys for playing the whole tones, and black keys for playing the half tones in accordance with conventional practice. On top of the case bottom 24 there is provided a base support 62, and the keys are pivotally supported on a rail 64 or the like extending across the support or base, the keys being positioned at the fulcrum by the usual balance key pins 66. Front key pine 68 likewise are provided in accordance with conventional practice, and a stop 70 in the form of a felt pad or the like is provided at the outer end of each key. The inner end of each key 60 is provided with an upstanding capstan screw 72 (Fig. 4), and further is formed with a projecting shelf 74 having a pad 76 of felt or the like thereon.

A pair of brackets 78 upstands from the base or support 62 adjacent the opposite edges thereof, and a main rail 80 extends transversely across the piano between these brackets and substantially at the inner ends of the keys 60. A plurality of butt flanges 82 is spaced along the upper edge of the main rail 80 in alignment with the keys 60, and hammers 84 are pivotally mounted on such flanges. Each hammer includes a butt 86 pivotally mounted on the corresponding butt flange 82, and having a padded tail 88 hearing against the corresponding capstan screw. A shank 90 extends forwardly and upwardly from each butt and supports a hammer head 92 and a padded striker 94.

A spring rail 96 extends between the brackets 78, being mounted thereon by means of blocks or auxiliary brackets 98. A plurality of springs 188 is spaced along the rail 96, and each spring is provided with a curled over end portion 182 bearing in a groove in a forwardly extending portion 104 of a corresponding one of the butts 86. The springs 100 hold the hammer shanks against a felt pad 104 on the bottom of a hammer rail 106 extending between upstanding portions of the brackets 78.

A plurality of damper lever flanges 106 is spaced along the front of a depending portion 1'88 of the main rail 80 in alignment with the butt flanges 82. A damper lever'110 is pivotally carried by each flange 115-6. A damper Wire 112 extends forwardly, and then upwardly from each damper lever flange to support a head 114 having a felt or other suitable pad 116. A spring (not shown) coiled around the pivot of each damper lever tends to rotate the same clockwise to hold the head pad 116 up against an associated vibratile reed 118 to damp vibrations thereof. A generally L-shaped hook 120 extends up from the free end of each damper lever 110 and overlies the felt pad shelf 76 on the forwardly projecting portion 74 of each key. Accordingly, when a key is depressed to play a note, the felt pad 76 engages beneath the hook 120 to release or retract the associated damper.

For forte playing it is necessary simultaneously to release or retract all of the dampers. This is effected by means of a damper rod 122 underlying the free ends of all of the damper levers 110, and journaled in a graphite impregnated felt bearing 124 in a generally semicircular groove 126 formed in a lateral recess 13% in the surface or base of the support 62. The darnper rod 122 has a bar 128 welded longitudinally along its side, and this bar extends beneath all of the damper levers 110. Spring means (not shown) normally hold the bar 128 resiliently against the under sides of the levers 110 as shown in Fig. 4. counterclockwise rotation of the rod 122 causes the bar 128 to cam against the damper levers 110 for simultaneously pivoting all of such levers in a counterclockwise direction to retract the damper levers. Means is provided in the form of a foot pedal 127 (Fig. 1) and a push-pull control 129 of the Bowden cable type to pivot the rod 122 in this manner. The foot pedal 127 thus comprises a loud pedal.

A support for the reeds 118, and also for associated pick-ups, is shown in Figs. 49 and comprises a generally rectangular frame 132. The frame 132 comprises a pair of parallel end rails or bars 134 and 136 spaced apart substantially the width of the piano. A rear bar or rail 138 of relatively fiat construction compared to the end pieces 134 and 136 extends between the rear ends of the end rails and is welded thereto. It will be seen in Figs. 4 and 9 that the rear bar or rail has its lower surface spaced above the bottoms of the end bars, and has its upper surface spaced below the tops of the end bars. A front bar or rail 140 extends between the front corners of the end rails and is welded thereto. The end bar 136, which corresponds to the treble end of the piano, is shorter than the end bar 134. Accordingly, the front bar 140 progressively approaches the rear bar 138 going from bass to the treble end of the keyboard in order to accommodate the reeds which decrease in length from the bass to treble end of the keyboard.

An upstanding portion on the front rail forms a reed mounting platform 142 spaced above a shelf 144. The shelf 144 becomes progressively narrower in moving from the bass end of the frame 132 to the treble end thereof, thus bringing the reed mounting platform 142 toward the back rail 138 at a more rapid rate than the front and back rails converge. The decrease of the width of the shelf 144 readily can be seen in Figs. -7 which are taken at spaced positions along the frame, and which also can be seen in Figs. 8 and 9. At the treble end of the frame the shelf 144 disappears completely. A rib 146 may be seen to lie between the front and rear rails and across the top of the shelf 144, being welded to the front and rear rails.

A plurality of the reeds 118 previously noted is spaced along the raised platform 142 of the front rail 140, being held thereon by cap screws 148 passing through wide mounting bases 150 on the reeds and threaded into tapped apertures 152 in the front rail 140.

Each reed preferably is made of spring steel and in addition to the base 150, each reed 118 comprises a vibratile tongue 154 extending from the base 150 toward the back rail 138. Each reed is ground to provide an undercut or shoulder 156 at the junction between its base 150 and its tongue 154 to insure vibration throughout the length of the tongue, but not in the base, therefore rendering precise positioning of the mounting means unnecessary. Pick-up means 158 are arranged oppositely of the reeds and in cooperative relation therewith for forming variable electric capacitors therewith. The pick-up means comprise, in the present instance, three pick-up bars 160, 162, and 164 as shown in Figs. 4-9. The pick-ups are made of conductive material, preferably aluminum. The pick-up bars are arranged end to end and the confronting ends preferably are joined by lugs 166 secured by means of screws to the pick-up bars.

The pick-up bars 160, 162, and 164 are mounted on top of an insulating strip 168 which is carried on top of the back rail 138 of the frame 132. Insulating grommets 174 (Fig. 4) of rubber or other suitable material extend through aligned openings in the three pick-up bars and through the insulating strip 168, the grommets being provided with circumferential flanges or heads 176. A cap screw 178 extends through each grommet and is threaded into a suitable tapped aperture 180 in the back rail 138.

The three pick-up bars all are provided with slots along I the edge confronting the cooperating reeds and the reeds vibrate in these slots. As may be seen in Figs. 4, 5, and 9 the bass pick-up 160 is provided with a forwardly projecting lower shelf 182, and the slots 184 extend through this shelf and back into the main portion of the pick-up bar 160. The ends of the confronting reeds 118 may be seen to be aligned with the slots and to lie in the same plane as the bottom of the pick-up bar. The bass reeds as shown in Figs. 4 and 5 are provided with lead weights 186 which produce a sufficiently low rate of vibration to achieve the bass tones without making the reeds unnecessarily long. The lead weights further damp the reeds to eliminate undesirable transients when the reeds are struck by the corresponding hammers, and help to effect a desirable decay characteristic.

As may be seen in Figs. 6 and 8, the front edge of the pick-up bar 162 does not extend as far out as the bass pick-up bar 160. The intermediate pick-up bar 162 is provided with a forwardly projecting shelf 188 similar to that on the bass pick-up bar, and the intermediate reeds 118 vibrate in slots 190 extending through the shelf 188 and back into the main portion of the intermediate pick-up bar 162. All of the reeds, including the intermediate reeds, are coplanar with the bottom of the corresponding pick-up bar when in quiescent condition and the thickness of the corresponding pick-up bar is correlated with the amplitude of the vibration of the reeds to keep the reeds from vibrating entirely through the pick up bars. The positioning of the reeds within the slots effects a high capacitance which changes materially when the reeds vibrate away from the pickup bars during each lower half cycle of vibration. During the upper half cycle of vibration, the capacitance between each reed and pick-up bar remains substantially constant. Vibration in this manner achieves the proper balance between lead weight 186 on the bass reeds does not affect the S capacitance inasmuch as it is farther away from the pickup bar than the reed is during the lower half of the vibration, and the capacitance remains constant during the upper half cycle ofvibration due to the substantially constant spacing from the pick-up bar to the reed and weight. Such weights may be used on some of the intermediate reeds, but are not necessarily used on all of them as may be seen in Fig. 6. It will be appreciated that the weighted reeds can be tuned readily by adding additional lead, or by filing off some of the lead already present.

The treble pick-up bar 164 as shown in Fig. 7 does not have a forwardly projecting shelf as the bass and intermediate pick-up bars do. However, the treble pickup bar 164 does have slots 192 cut into the front of it for receiving the treble reeds 118. The stepped arrangement of the three pick-up bars as best seen in Fig. 8 provides for proper convergence of the reeds with the pick-up means in accordance'with the varying physical dimensions of the reeds and the amplitudes of the vibrations thereof. It is contemplated that a single reed bar could be used and could be made of tapered configuration, but the three bars lead to easier machining and also make it possible to apply difierent potentials to the various reed bars if it be desired to do so in order to control the relative volumes of the different groups of reeds.

The frame 132 is supported at its opposite ends on rubber blocks 194 and 196 as indicated in Figs. 2, 9, and 4. The end bars 134 and 136 lie on top of the rubber blocks 194 and 196 respectively, and cap screws 198 or the like pass through suitable apertures 200 in the end bars, through aligned apertures in the rubber blocks 194 and 196, and are threaded into the base or support 62, the rubber blocks 194 and 196 resting on this base for support. The rubber blocks provide a firm yet resilient support which prevents the transmission of vibrations from the piano to the reeds and pick-ups. The substantial mass of the welded iron or steel frame 132 further prevents damping of the reeds.

The pick-up bars 160, 162, and 164 are connected together in the illustrative embodiment as heretofore set forth. An electric potential is applied to all of the pick-up bars from the amplifier, and the pick-up bars are connected in parallel to the input of the amplifier, the reeds being grounded through their mounting on the front rail 140 of the frame 132. A conductive shield 202 (Figs. 2-4 and 10) covers the pick-ups and the outer ends of the reeds. The shield 202 is preferably formed of sheet aluminum and includes a back wall 204, a top 206, the top being provided with a downwardly inclined flange or visor 208, and a pair of end pieces 209. Outwardly directed ears 210 on the end pieces rest on top of the end bars 134 and 136 of the frame 132 and are held thereto by screws 212 threaded into tapped apertures 214 in the end bars. The capacitance change between the reeds and pick-up means, due in large measure to the vibration of the reeds in the slots of the pick-up, is sufficiently large that perfect shielding is not necessary, and it has been found that the single shield disclosed is sufiieient to render background noises and hum inaudible in the output of the piano.

A modified form of pick-up means is shown in Fig. 11, this form being simpler and more economical to fabricate and to assemble than that previously shown. The pick-up means shown in Fig. 11 is indicated generally by the numeral 158a, and comprises a block 160a of insulating material such as plastic and formed of the same thickness as one of the pick-up bars, for instance 160, and the insulating bar 168. The insulating member 160a may be molded of plastic, and accordingly may encompass the entire width of the keyboard and may be molded to a suitable shape to obviate the necessity of providing three separate pick-up bars. The front projecting portion of the pick-up bar 160a is provided with slots 184a in which the vibratile tongues 154a of the reeds 118a may vibrate, the reeds having their bases a held to the front rail 140a by cap screws 148a. The upper and lower surfaces and the outer ends of the forwardly projection portion of the insulating bar w are coated with a conducting material 216 which preferably is a metal, silver being a preferred example, which may be painted, sputtered, chemically, or otherwise deposited on the insulating base. The metal coating is not on the side walls nor the end walls of the slots. The metal coating 216 cooperates with the vibratile tongues 154 of the reeds 118a to form cooperative tone generators. It will be noted in Fig. 11 that in the case of some of the bass reeds the slots 184a are sufiiciently wide to accommodate two reeds side by side. Fabrication and assembly is simplified in this manner without adversely affecting the total output of the bass reeds, and it also is contemplated that some or all of the reeds in addition to the'bass reeds might so cooperate with wide slots.

As previously indicated, the felt pad 116 of each damper normally bears against the corresponding reed 118. When a key 60 is depressed, the shelf 74 and felt pad 76 thereon engage beneath the hook 120 to retract the damper from the corresponding reed. At the same time the corresponding capstan screw engages beneath the butt pad 88 of the corresponding hammer to start the hammer into motion. The pad 70 at the outer end of the key stops the key before the hammer hits the reed, and inertia continues the hammer in motion until the head pad 94 engages the reed and causes it to vibrate. The butt pad then returns against the capstan screw and the hammer is held in partially depressed position until the key is released. Release of the key allows the hammer to return to its rest position as shown in Fig. 4, and allows the damper pad 116 to engage the reed to damp it. The variation in capacity between the vibrating reed and its associated pick-up causes a change in potential applied to the input of the amplifier 44 corresponding to a piano tone. This change in potential is amplified and is transduced as by the loudspeaker 46 into an audible piano tone.

The rigid and massive support frame 132 prevents damping of the reeds, and provides sufficient inertia to damp vibrations that might otherwise be transferred by other parts of the piano to the reeds. The rubber supports at the end of the frame mechanically insulate the frame from vibrations in other parts of the piano, and thus further prevent transmission of vibrations to the reeds. The offset or stepped pick-up bars afford proper cooperation with the vibrating reeds, while the large currents generated by the close coupling of the reeds and pick-up bars renders one shield sufficient.

The specific embodiments of the invention herein shown and described are for illustrative purposes only, and it is to be understood that the invention also encompasses all that which falls fairly within the spirit and scope of the appended claims.

I claim:

1. An electronic piano including a plurality of vibratile reeds, pick-up means cooperating with said reeds to form a plurality of electric tone generators, a single massive support carrying said reeds and pick-up means to prevent damping of vibrations of said reeds and to prevent transmission of extraneous vibrations to said reeds, said massive support including a generally rectangular frame having a pair of massive end bars, a front bar extending between said end bars, a rear bar extending between said end bars, said front bar and said rear bar extending generally longitudinally substantially across said piano and said front bar progressively approaching said rear bar, one of said front and rear bars being massive relative to the other and having a raised portion providing a shelf substantially confronting the other of said front and rear bars, said shelf becoming progressively narrower from the bass to the treble end of the piano and said raised portion thereby approaching the other of said front and rear bars more rapidly than the remainder of said one bar, said pick-up means being supported on the other of said front and rear bars and said reeds being supported on the raised portion of said one bar and projecting across into cooperation with said pick-up means, the reeds diminishing in size from bass to treble, and thus being properly positioned relative to the pick-up means.

2. An electronic piano as set forth in claim 1 wherein the reeds are mounted in electrical contact with said one bar of said support.

3. An electronic piano as set forth in claim 2 wherein the pick-up means are capacitively related to said reeds, and further including insulating means mounting said pickup means on the other of said front and rear bars.

4. An electronic piano as set forth inclaim 3 wherein the insulating means comprises a strip of insulating material interposed between the pick-up means and the other of said front and rear bars.

5. An electronic piano as set ,forth in claim 1 and 0 further including a rib on said support extending between the front and rear bars and substantially parallel to the end bars.

References Cited in the file of this patent UNITED STATES PATENTS 2,187,251 Severy Jan. 16, 1940 2,200,718 Miessner May 14, 1940 2,275,252 De Muth Mar. 3, 1942 2,414,886 Miessner Jan. 28, 1947 2,492,919 Hings Dec. 27, 1949 2,581,963 Langloys Jan. 8, 1952 2,656,755 Miessner Oct. 27, 1953 2,729,132 Kunz Jan. 3, 1956 FOREIGN PATENTS 401,537 Great Britain Nov. 16, 1933 434,421 Great Britain Aug. 27, 1935' 986,011 France Mar. 21, 1951

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