US2253782A - Keyboard for electrical musical instruments - Google Patents

Description

Aug. 26, 1941.

L. HAMMOND EI'AL KEYBOARD FOR ELECTRICAL MUSICAL INSTRUMENTS Filed lay 7, 1940 3 Sheets-Sheet l w ds Z. NHKHM., r n n :ray .M/ mmss, n m@ f m T 04.2 0 UaHW mgm/7 6 ,5. s e; r d, n.5. A. c., 1*. r. i u@ w//GM aG u IW i.. WE/ a //f .6 2 n Uw 5 l u 5 L l JWN/Ww d. i w w @MRT Aug. 26, 1941. L HAMMOND Erm.

KEY-BOARD FOR ELECTRICAL MUSICAL INSTRUMENTS Filed May 7, 1940 3 Sheets-Sheet 2 fnl/er? zor Laure/2s Hammond I Geo/"ge Hze/o/ens @JW Wfl/@1942 fg.

L. HAMMOND EI'AL Aug. 26, 1941.

' KEYBOARD Eon ELECTRICAL MusIcAL ms'rEUuEuTs Filed May 7, 1940 3 Sheets-Sheet 3 /8 6l 20 IE6 //6 fr? Ver; zor' La ure/2s .Hammond Ge rgeH ,oke/Es' Patented Aug. 26, 1941 KEYBOARD FOR ELECTRICAL MUSICAL INSTRUMENTS Laurens Hammond, Chicago, and George H. Stephens, Glencoe, Ill., assgnors to Hammond Instrument Company, Chicago, Ill., a corporation of Delaware Application May 1, 1940, sei-iai N0. 333,824

13 Claims.

Our invention relates generally to keyboards for electrical musical instruments, and more particularly to a keyboard of this type which is exceedingly small and compact.

In general, the keyboard comprises a plurality of octaves of keys which are preferably of the same width and spacing as keys of a standard piano, but whichl are considerably. shorter in length so that the keyboard as a whole may be attached to a piano keyboard without interfering with the normal use of the piano.

The general features of construction of this keyboard and its advantages and uses in their broader aspects are disclosed and claimed in the application of Laurens Hammond, Serial No. 322,903, filed March 8, 1940, the present application being directed to constructional features of the keyboard which are more or less independent of the external shape, appearance and uses of the keyboard.

It is thus an object of our invention to provide an improved simple and compact keyboard for an electrical musical instrument in which each of the keys may be utilized reliably to operate one or a plurality of switches, and in which tablet operated switches are incorporated asa structural part of the keyboard.

A further object is to provide a simple keyboard for electrical musical instruments which may be economically manufactured and which will be reliable and durable.

A further object is to provide a keyboard for electrical musical instruments in which the key stroke is very short, the key action rapid, and which may be conveniently used by the musician.

Other objects will appear from the following description, reference being had to the accompanying drawings in which:

Figure 1 is a perspective view of the keyboard of my invention showing it as attached to the front rail of a piano;

Figure 2 is an enlarged transverse sectional view of the keyboard taken on the line 2-2 of Fig. 1;

Figure 2a is an enlarged sectional view of the tablet switch mechanism and tablet 'mounting taken on the line 2a--2a of Fig. 4; and

Figures 3 to 8 inclusive are longitudinal sectional views taken on the lines 3-3 to 8--8 inclusive, respectively, of Fig. 2.

The keyboard comprises a frame or casing, the back and bottom of which are provided by an angle -sheet forming a rear wall having a rearwardly oiset upper portion 22, and a horizontal bottom portion 24. The offset in the rear wall portion of the sheet 26 is provided to make the keyboard more easily attachable to planos, the front railsof which are often of protruding conformation.

At intervals spaced approximately the space of three keys apart, are vertical frame plates 26 which have ears 30 projecting into complementary shaped slots formed in the bottom wall 24 of the sheet 20. 'I'he plates 26 are held in properly spaced relation not only by their ears l0, but also by an apertured bar 21, extending through slots 28 in the plates, and having notches 29 which engage the plates. The notched bar 21 is held in such interlocking engagement with the plates 26 by a wire 3| which is pushed through the slots 28 after the bar 21 has been inserted and moved laterally to cause the notches there.P in to engage the plates.

The plates 26 are held in assembled relation with the casing sheet 20 by clamping bars 32, 34 which extend through slots 36 and 38 respectively formed in the vertical frame plates 26, and are clamped against the edges of these slots by aplurality of screws 46 and 42 respectively, which are tapped in the bars 32 and 34 and extend through the rear and bottom portions 26 and 24 respectively, of the casing sheet 26.

A top frame plate 44 is secured to a front frame plate 46 by screws 48 as best shown in Fig. 2', the front plate 46 being secured to the bottom 24 of the angle sheet 26 by screws 49. The top plate 44 is staked to the vertical frame plates 26 by lugs 56, which project upwardly from the frame plates 26 through complementary shaped slots in the top plate 44. The upper ends of the frame plates are thus held in properly spaced relation.

'Ihe playing keys 52, 54 are preferably made of a molded plastic and of hollow boxlike construction, each having a downwardly projecting boss 56 which is tapped to receive a 'fastening screw 58. Each of the keys is supported by a pair of leaf springs 66, 6|. Several of the-leaf springs 68 may be made integral as shown in Fig. 8, and have their forward ends secured by rivets 62 to the top frame plate 44.

Leaf springs 6| may likewise be formed in lntegral groups of three or more, the groups being secured to a switch arm supporting plate 64 by screws 66, suitable dowels 68 partly punched from the plate 64 being provided accurately to locate the springs 6|. The springs 6| also serve as switch arms as will be more fully described hereinafter.

Switch actuators 1l are secured to the keys 62,

54 by screws 58, the actuators having aligning dowels 12 partly punched therefrom to engage in complementary recesses formed in the lower surfaces of the bosses 56. The dowels also project through suitable complementary openings in the leaf springs 60 so as to prevent rotation of the keys about the axis of the screws 50. The actuators 10 are provided with openings 14 through which extend resilient switch arms 16. In each instance, the arm 16 is insulated from its associated actuator 10, by a notched insulating member 18 which is riveted to the lower end of the actuator 10, being further fixed in position by a dowel B partially punched from the actuator 10.

A spring latch 82 is clamped between the insulating member 18 and the actuator 10, and has a tip 84 which is bent at an angle but otherwise conforms to the shape of a tip 86 formed at the lower end of the member 18. The tips 84 and 86 project through a suitable opening formed in the leaf spring 6|, and the tip 84 thus acts as a latch frictionally to hold the spring 6| in engagement with insulating member'18, in the position shown in Fig. 2.

The switch arms 16 are riveted to an insulating strip 88 and project through suitable openings 90 formed in switch supporting plate 64 so as not to make contact with the latter. Each of the switch arms 16 has a lug 32 formed integrally therewith to which a connecting wire 94 is soldered.

The plate 64 is suitably secured to the vertical frame plates 26 by screws 86 which are threaded in a clamping bar 98 which extends through suitable slots formed in the vertical frame plates 26. The plates 26 are also provided with forwardly extending ears or lugs |00 which engage in complementary slots formed in the frame plate 64 so as to aid in holding the latter in fixed position with respect to the frame plates. The switch arms 16 are suitably shielded by a guard |02 secured to the switch mounting plate 64 by screws |04.

Downward movement of the keys 52, 54 is limited by a down-stop |06 which may be made of felt or similar material, and rests upon the top plate 44. The upward movement of the keys is limited by an up-stop |08 which may be in the form of a strip of felt secured beneath the top plate 44 and adapted to be engaged by the leaf springs 60. The white keys 54 are prevented from being swung sidewardly beyond a predetermined permissible extent by lugs ||0 struck upwardly from the top plate 44, which project into suitable recesses ||2 which are formed in bosses ||3 projecting downwardly from the tops of the keys 54.

Bus bars ||4 are secured to insulating strips I |6 which are longitudinally slideable, being supported by the vertical frame plates 26. Each of the bus bars ||4 is provided with a contact wire ||8, which may be welded or soldered to the upper edge of the `bus bar, the wire preferably being made of a rare metal alloy of the platinum group. A similar contact wire |20 is welded to the ends of each of the switch arms 16 and is adapted to contact the bus bar contact wire ||8 whenever the key associated with the switch arm 16 is depressed, the switch arm being resiliently biased to move to the position to make such contact, that is, the switch arm 16 normally assumes the position in which it is shown in dotted lines in Fig. 2, being flexed to its full line position by the insulating member 10 as the actuator 'l0 moves upwardly upon the return stroke of the key.

A bus bar |22 having a contact wire |24 welded to its upper edge is supported by and secured to an insulating strip |26 which is mounted for limited longitudinal sliding movement through suitable openings formed in the vertical frame plates 26. The leaf springs 6| are provided with contact wires |28 which, when the associated keys are depressed, engage the contact wire |24, as indicated in dotted lines in Fig. 2. While the insulating strips ||6 and |26 extend the full length of the keyboard, there is preferably a separate bus bar such as I |4 and |22 for each octave of the keyboard, since in the preferred form of the insturment as shown in the co-pending application of Laurens Hammond and John M. Hanert, Serial No. 293,444, filed September 5, 1939, the electrical circuits to be made require separate bus bars for each octave. Any suitable means may be provided for longitudinally sliding the insulating strips ||6 and |26 which support the bus bars, for the purpose of changing the points on their contact wires which the contact wires |20 and |28 will engage. In this way, the portions of the contact wires which are brought into engagement may be changed, should the wires fail to make electrical contact due to the presence of a particle of dust or other foreign matter, or because of localized wear of the contact wires ||8, |24. Such shiftable bus bars, and the means for longitudinally shifting them are more fully disclosed in my Patent No. 2,099,204, granted November 16, 1937.

Arranged side by side so as to form the front face of the keyboard assembly are a plurality of tilting tablets |30 which are preferably made of a molded plastic material and of hollow construction, having bosses |32 formed on their inner side walls. The tablets are capable of tilting motion about a shaft |34 extending through the bosses |32, the shaft |34 being supported at intervals by brackets |36 which are peened to the front plate 46 as best shown in Fig. 2a. Each oi the tablets |30 has two or more inwardly extending projections |38, which form switch ac tuators. The tablets are frictionally held ix either of their two positions of adjustment, shown in full lines and dotted lines in Fig. 2, by leaf springs |40, a number of which may be formed integrally as a comb, the springs being secured to the lower inwardly turned flange of the front plate 46 by rivets |42.

A plurality of switch arms |44, |46 are secured to an insulating plate |48 which is secured to the front frame plate 46. The switch arms |44 and |46 are adapted to engage contact lugs |45 and |41 respectively, the lugs being suitably riveted to the insulating plate |48 as indicated in Fig. 2a. The switch contact arms |44 and |46 are likewise riveted to the insulating plate |48, as best shown in Fig. 6. Suitable openings are formed in the front plate 46 and insulating plate |48 to permit the actuator projections |30 to engage the switch arms |44 and |46. When the tablet |30 is tilted to the position in which it is shown in full lines in Fig. 2, the lower actuator projection |38 will engage the switch arms |44 and swing them away from the contact lugs |46, while when the tablet 30 isswung to its full line position, the upper actuator projection will engage the switch arm |46 and flex the latter away from its contact'lug |41. The switch arms |44, |46 and the contact lugs |45 and |41 are preferably provided with rare metal contact tact lugs |45 and |41 are provided with inwardly bent portions forming soldering lugs for the wires connected to these parts.

The tilting movement of the tablets |80 is limited `by stops |50, I| which may be in the form of felt strips extending the full length of lthe front plate 46, being secured thereto by cementing or in any other suitable manner. A name plate supporting bar |52 has lugs |54 thereon, the lugs being secured to the top plate 44 and front plate 46 by screws 48. A name plate |56 of generally inverted trough shape resiliently engages the edge of the supporting bar |52 so that it will normally be frictionally retained in position, but may be slid longitudinally from the supporting bar |52 should it become desirable or necessary to replace it. The name plate |56 preferably has tablet indentifying indicia stamped or marked thereon to enable ready identification of the control functions of the various tablets |30. l

The ends of the keyboard assembly are covered by end blocks |58 and |60 which are preferably made of a molded plastic and which prevent longitudlnal shifting movement of the name plate |56 on its supporting bar |52.

ture of the keyboard so that they may be readily detached therefrom.

The tablets |30 and switches operated thereby may be arranged in any suitable manner depending upon the functions to be performed upon shifting the tablet. For example; if three less be carelessly and roughly operated without in any way damaging the action.

The key action is very compact, having been practically constructed so, as to have an over-all 5 height of less than 31A" (i. e. from the top of The blocks |58 and |80 are suitably secured to the frame struccontacts are to be opened when the upper end of lthe tablet is pushed inwardly (swung counter-clockwise, Fig. 2), the tablet may be provided with three projecting actuators |38 above its pivot shaft |34 and three switch arms |46, with their contact lugs |41, in position to ybe operated thereby. On the other hand, should it be desired that the tablet should open three switches when it is tilted by pushing its lower end (swung clockwise, Fig. 2), the tablet may be provided with three actuator projections |38 below its pivot, and three switches |44 together with their contact lugs ,|45 provided for opera.- tion by these three actuators. Any other arrangement of the actuators and switches may be made, depending upon the manner in which the switches are to be operated.

inasmuch as each of the keys is supported by a spring and a spring 6|, the keys will have substantially translatory movement when depressed. Excessive tilting or excessive lateral swinging movement of the keys is prevented, due to the fact that their actuators 10 project through the openings formed in the notched bar 21. There is sufficient clearance between the actuator bars 10 and the walls of the openings in the notched rbar 21, that some tilting movement of the keys is possible, but such movement is limited to an extent which will not damage the leaf springs 60 and 6|. Similarly, the white keys 54 are prevented from being swung laterally to an injurious extent by the inter-engagement of the lugs ||0 and the sockets ||2 formed in the bosses ||3. Thus, While the key mounting is delicate in the sense that the force required to depress the keys is very small, and the key stroke is short, the key mounting is such that Athe keys may neverthethe black key 52 to the bottom plate 24), but despite the small size of the parts, the keyboard is sufficiently rugged to withstand the normal use'and abuseY to which it may be expected to be subjected. Despite the fact that each key operates two switches, and each tablet may operate one to three switches, sufficient space is provided within the confines of the main casing frame plates to provide for the numerous wires by which connection to the switches is made. The wires for the switch arms 16 may be formed in a cable in the space adjacent the lugs 92 of these switch ar'ms, while the wires for the tablet operated switches may be formed in the cable located between the shielding guard |02 and the tablet operated switches.

While we have shown and described a particular embodiment of our invention, it will be apparent to'those skilled in the art that nurnerousA modications and variations may be made without departing from the underlying principles of the invention, wetherefore desire by the following claims, to include within the scope of our invention all such modifications and variations by which substantially the results of our invention may be obtained through the use of substantially the same or equivalent means.

We claim:

l. In a keyboard for an electrically controlled musical instrument, the combination of a plurality of keys, an actuator secured to each of said keys, a pair of leaf springs extending in a direction perpendicular to the direction of movement of said keys, each of said leaf springs having one end which is rigidly held and the other end secured to said key and actuator respectively, whereby said key will be capable of substantially rectilinear translatory movement upon depression thereof and be restored by said springs, and contact switches operated by said actuator.

2. In a keyboard for electrically controlled musical instruments, the combination of a casing having an opening in the top thereof, a key having a boss projecting through said opening, a pair of key supporting leaf springs, each having one end rigidly secured with respect to said casing, said leaf springs extending substantially perpedicularly to the direction of movement of said key, a switch actuator, means for securing said switch actuatorand the free end of one of said leaf springs to said key boss, and an operating connection between the free end of the other of saidsprings and said actuator.

3. In a keyboard for an electrically controlled musical instrument, the combination of a plurality of switches, a vertically reciprocable actuator for said switches, a pair of leaf springs, each having one end attached to said actuator and its other end rigidly supported, said leaf springs being spaced from one another and extending in a generally horizontal direction, and a key rigidly secured to said actuator.

4. In a. keyboard for electrically controlled musical instruments, the combination of a. casing having a plurality of vertical frame plates secured therein, a switch arm supported by said vertical frame plates, a vertically reciprocable actuator for said switch arm, a pair of leaf springs each having one end secured to said actuator adjacent the ends thereof respectively, means for rigidly securing the other vends of said lead springs with respect to said casing, and a key having a part extending freely through said casing and rigidly secured to said actuator.

5. In a keyboard for an electrical switch controlled musical instrument, the combination of a casing having a front, rear, top and bottom wall, a plurality of tablets pivotally mounted on the front wall of said casing, an insulating sheet secured inside said front wall, a plurality of switch members secured to said insulating sheet, said front wall and said insulating sheet having registering apertures formed therein, and actuator projections on said tablets adapted to project through said registering apertures and to operate said switch members upon tilting movement of said tablet.

6. In a keyboard for an electrically controlled musical instrument, the combination of a frame, a plurality of vertically movable keys, an actuator secured to each of said keys, a pair of generally horizontally extending leaf springs for each of said keys, said leaf springs having one end rigidly secured to said frame and each having its other end secured to said actuator, whereby said keys will be capable of substantially translatory vertical movement upon depresslon thereof and will be restored by said springs, and a switch operated by said actuator.

7. In a keyboard for electrically controlled musical instruments, the combination of a frame, a vertically reciprocable key, a pair of key supporting leaf springs, each having'one end rigidly secured with respect to said frame, said leaf springs extending substantially horimntally, a switch actuator, means for securing said switch actuator and the free end' of one of said leaf springs to said key, and an operating connection between the free end of the other of said springs and said actuator.

8. In a keyboard for an electrically controlled musical instrument, the combination of a plurality of switches, a vertically reciprocable actuator .for said switches, a pair of leaf springs, each having one end attached to said actuator and its other end rigidly supported, said leaf springs being spaced from one another and extending in a generally horizontal direction, and a key rigidly secured to said actuator and supported solely thereby.

9. In a keyboard for an electrical switch controlled musical instrument, the combination of a casing having a front, rear, top and bottom Wall, a plurality of tablets pivotally mounted on the outside of the front wall of said casing, an insulating sheet secured inside said front wall, a. plurality of switch members secured to said insulating sheet, said front wall and said insulating sheet having registering apertures formed therein, actuator projections on said tablets adapted to project through said registering apertures and to operate said switch members upon tilting movement of said tablet, a plurality of keys having operating parts extending through the top wall of said casing. and switches mounted within said casing and operable by said key parts.

10. In a keyboard for electrical musical instruments, the combination of a frame, a depressible key, a leaf spring support for said key having one end rigidly secured to said frame and its other end rigidly secured to said key, a rigid stop element carried by said frame, and means on said key cooperable with said stop element only when said key is swung sidewardly an excessive extent, thereby to limit the extent of sideward movement of said key and prevent excessive deformation of said leaf spring support.

11. In a keyboard for electrical musical instruments, the combination of a frame, a depressible key of a molded plastic composition and having a boss and a downwardly facing socket, a leaf spring support for said key having one end secured to said boss and the other end thereof secured to said frame, and an upwardly projecting element rigid with said frame and extending partially into said socket, there being sufficient sideward clearance between said projection and the inner walls of said socket to prevent contact between said element and said socket when said key is operated normally, said element and socket cooperating to prevent said key from swinging in a horizontal plane a sufficient extent to cause damage to said leaf spring support.

12. In a keyboard for an electrical musical instrument, the combination of a depressible key, a keyboard frame, a leaf spring having one end secured to said frame and its other end secured to said key, said leaf spring extending in a generally horizontal direction, an actuator secured to said key and extending downwardly therefrom, and a member secured to said frame and having an opening therein receiving said actuator, said opening being slightly larger than said actuator in cross section, whereby said member serves as a means to prevent excessive lateral movement of the portion of said actuator extending therethrough without interfering with its normal vertical movement. V

13. In an electrically controlled musical instrument, the combination of a supporting plate having an aperture therein, a contact switch secured at one side of said plate and having a movable switch arm extending across said aperture, and an actuating tablet pivotally supported on the other side of said plate and having a projection of insulating material of suniciently small size freely to extend through said aperture and engage said switch arm to operate said switch upon pivotal movement of the tablet.

LAURENS HAM'MOND. GEORGE H. STEPHENS.

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