Electro-mechanical stringed bass machine

A stringed bass machine is disclosed in which vertical bass guitar strings are struck by hammers and are not plucked or strummed. An electrically operated upright piano action receives power from an external control box having an on-off switch. A musician can operate the bass machine by means of a remote keyboard and/or pedalboard. A unique sound is derived from an acoustically insulated soundboard, which encloses the guitar strings and piano action.

BACKGROUND OF THE INVENTION 
U.S. Pat. No. 4,156,380 discloses an electrically operated guitar having a 
sound box within which guitar strings are fretted and strummed or plucked. 
By using a keyboard, a musician can create the sounds characteristic of 
the electric guitar. 
The present invention has for its main objective to provide an electrically 
operated bass machine in which the bass strings are struck by hammer 
elements and are not plucked or strummed. Cooperative string dampering 
heads eliminate string fretting and a uniquely different musical sound is 
produced by the instrument as a result of striking the strings within an 
acoustically insulated enclosure or "soundboard". The sound produced by 
the machine is derived from a combination of acoustical dampering, 
reverberation and resonance not achievable in any known prior art device. 
A further object of the invention is to provide an improved 
electro-mechanical bass machine of the above-noted type which a musician 
can operate by a remote keyboard and/or pedalboard, while simultaneously 
playing other instruments. 
Another object of the invention is to provide a musical instrument of the 
above-noted type which is comparatively simplified in its construction, 
entirely practical, convenient to operate and constructed largely from 
commercially available components. 
Other objects and advantages of the invention will become apparent during 
the course of the following detailed description.

DETAILED DESCRIPTION 
Referring to the drawings in detail wherein like numerals designate like 
parts, an electro-mechanical string bass machine according to the present 
invention comprises four main components, namely, an external control box 
20 having an on-off switch 21 mounted thereon, FIGS. 1 and 10; a sound 
producing enclosure or "soundboard" 22: a remote keyboard 23; and a remote 
pedalboard 24. 
The soundboard 22, FIG. 4, comprises a bottom exterior panel 25 having four 
casters 26 mounted thereon near the corners thereof to render the machine 
readily movable from place-to-place. A bottom interior panel 27 is spaced 
somewhat above the panel 25 with a layer of acoustical insulation 28 
disposed therebetween. A lower front vertical panel 29 rises from the two 
bottom panels 25 and 27 and is suitably fixed thereto. A layer 30 of 
acoustical insulation is fixed to the interior face of the panel 29. A 
lower horizontal panel 31 fixed to the top edge of the panel 29 extends 
rearwardly thereof and an underlying acoustical insulation layer 32 is 
disposed between the panel 31 and an interior cover 33 parallel to the 
panel 31. An upper vertical panel 34 rises from the panel 31 and carries 
on its interior face a layer of acoustical insulation 35. A top horizontal 
panel 36 has its bottom surface covered by a layer of acoustical 
insulation 37 and a top rear cover strip 38 completes the closing of the 
top of the soundboard 22. 
A standard piano double pin block 39 is vertically disposed within the 
soundboard 22 and extends from top-to-bottom thereof, FIG. 4. A vertical 
front interior panel 40 is spaced forwardly of the double pin block 39 in 
parallel relation thereto. The front interior panel 40 extends from the 
rear edge of horizontal interior cover 33 upwardly to a point just below 
the insulation layer 37. 
The soundboard or enclosure 22 further comprises exterior side walls 40', 
FIG. 3, having acoustical insulation 41' attached to their interior faces. 
Interior side walls 42' spaced from the exterior side walls have 
acoustical insulation 43' on their outer faces, FIG. 12. Side skirts 44' 
complete the closing of the soundboard at the lower corners on its 
opposite sides. Vertical cover strips 45' are similarly provided at the 
rear vertical corners of the soundboard. 
In essence, therefore, it should be apparent that the soundboard 22 of the 
machine is a double enclosure in which the spaced interior and exterior 
walls are acoustically insulated over substantially their entire areas. 
The rear vertical wall of the soundboard adjacent to the strings 47 is 
doubly insulated between the block 39 and a rear vertical panel 42. An 
acoustical insulation layer 41 covers the rear face of the block 39 from a 
point near its bottom to an elevation somewhat below the tuning pins 48. A 
thicker acoustical insulation layer 43 covers the forward face of back 
vertical panel 42, as shown in FIG. 4. The panel 42 is secured by screws 
44 to the block 39 in spaced parallel relationship thereto. A lower 
horizontal skirt strip 45 completes the closing of the soundboard 22 at 
its lower rear corner below the back panel 42. A front interior vertical 
panel 46 extends between the forward edge of horizontal interior cover 33 
and the bottom interior panel 27. 
The standard electric bass guitar strings 47 are held in a substantially 
vertical plane forwardly of the standard piano double pin block 39. The 
upper ends of the strings 47 are attached to piano tuning pins 48, held in 
the block 39 near and below its top edge. The lower ends of the guitar 
strings engage a standard bass guitar bridge 49 anchored to the forward 
face of the block 39 near its bottom. The lower ends of the strings 47 are 
conventionally anchored as indicated at 50 in FIG. 4. 
Somewhat below the tuning pins 48, the guitar strings 47 engage bass guitar 
nuts 51 at various elevations. Pressure bars 52 forwardly of the block 39 
are attached thereto by screws 53, as shown in FIG. 4. 
Within the lower forward chamber 54 of the soundboard 22 and forwardly of 
the guitar strings 47 is mounted a horizontal solenoid shelf 55, supported 
adjustably on screw-threaded shelf support rods 56. Electrical solenoids 
54 are mounted in two parallel transverse rows on the shelf 55, FIG. 3. 
Each solenoid 57 has a vertical axis plunger 58 connected with a 
horizontal drive link 59, FIG. 5, adjustably connected with a vertical 
screw-threaded rod 60, and being guided by a vertical guide rod 59' 
extending downwardly from the shelf 55. The lower end of each rod 60 is 
threadedly connected to an ell 61 forming a well-known part of a 
conventional upright piano action. The upright piano action may be 
substantially of the type shown in U.S. Pat. No. 356,109 issued to Ellis 
and in other patents. 
Briefly, the piano action comprises a transverse standard vertical action 
rail 65, FIG. 5, near and above the interior bottom panel 27 and somewhat 
forwardly of the bridge 49. The rail 65 is supported on a pair of 
transversely spaced action brackets 68 whose lower ends are attached to 
the interior bottom panel 27 by L-brackets 69. A hammer rail 70 having an 
inclined felt pad 71 on its forward face is attached to supports 72 
secured to the action brackets 68. 
The standard upright piano action includes hammer heads 73 carried by 
hammer shanks 74 rising from a hammer butt 75. A set of damper heads 76 
for each string and hammer is held adjustably on a damper rod 77 secured 
to an upright jack 78 pivotally attached at 79 to the ell 61. The usual 
backcheck means 80 and pad 85 is provided, along with a strap 86. A hammer 
spring rail 81 is secured to the rear of action brackets 68 by screws 82, 
FIG. 5. In this figure, the numeral 82' denotes the let-off rail and the 
numeral 83' denotes the let-off button. The tops of action brackets 68 are 
stabilized by horizontal threaded rods 83 which extend rearwardly and are 
adjustably connected with the block 39, as shown in FIG. 5. Other 
components of the piano action are well known in their construction and 
operation and the hammer action need not be further described for a full 
understanding of the invention. Suffice it to say that each solenoid 57 
controls the operation of one hammer 73 and two dampering heads 76 for 
each bass guitar string 47, and the solenoids, string striking hammers and 
dampering head pairs correspond in number to the strings 47. 
The solenoids 57 are remotely controlled by the musician who can operate 
the keyboard 23 or the pedalboard 24, or both, as need dictates, to 
provide the desired harmony. As shown in FIGS. 8 and 9, the keyboard 23 
consists of the customary black and white keys 87 and 88, each having an 
upwardly biasing spring 89 associated therewith, which spring can engage 
an upper electrical switch contact 90 when a particular key of the 
keyboard is depressed by the musician. A lower switch contact 91 is 
engaged by the upper contact 90 when the latter is depressed, closing an 
electrical circuit for each key and delivering 24 volts DC through a 
20-foot power cable 92, FIG. 11, having conductors leading to the coils of 
the solenoids 57. 
The spring 89 for each keyboard key is attached to a common fixed spring 
mounting strip 93. Each lower switch contact 91, FIG. 11, is serially 
connected to a capacitor 94 in each keyactivated circuit of the cable 92. 
Similarly, the pedalboard 24, FIGS. 6 and 7, comprises long and short 
pedals 96 and 97, each being supported on a leaf spring 98 secured to a 
pedal mount 99. Felt stops 100 and 101 for the long and short pedals 96 
and 97 are mounted below the pedals on side plates 102 connected with a 
pedalboard pan 103 secured to the pedal mount 99 by bolt means 104. 
Each long and short pedal operates a dual contact switch 105 held on a 
switchboard 106, each such switch being closed by an adjustable screw 
actuator 107 of each long and short pedal. Upward movement of each pedal 
is arrested by contact with a pedal tension board 108 having a bottom felt 
facing 109. The tension board 108 is connected by a bolt 110 with the 
underlying pan 103, FIG. 6. The pedalboard 24 includes at one end a 19 
point receptacle 111 mounted on one of the side plates 102. The pedalboard 
has a removable cover 112, FIG. 6. 
A lower contact 113 of each pedal switch 105 is connected with a capacitor 
114. The switches 105 for the long and short pedals 96 and 97, FIG. 11, 
are connected in parallel, as are the keyboard switches. The pedalboard 
switches have their conductors included in a preferably 20-foot cable 115 
leading through one side wall of the soundboard 22, FIG. 3. The keyboard 
cable 92 enters the soundboard or enclosure 22 at the same point. 
The external control box 20, FIG. 10, receives 120 volts AC from a power 
cable 116 through an adapter 117 on the control box. The on-off switch 21 
for the machine is connected between the 120 volt AC power supply and the 
primary of a stepdown transformer 118 having a 24 volt AC output through 
its secondary. A conventional rectifier circuit 119 in the control box 20 
connected with the secondary coil of transformer 118 delivers 24 volts DC 
through a 15 foot power cable 120 to the soundboard 22 and its solenoids 
57, as shown in FIGS. 3 and 11. The 24 volt DC power delivered by the 
cable 120 is selectively activated through each of the solenoids 57 by the 
described keyboard and/or pedalboard switches. As previously stated, the 
musician can operate the keyboard 23 or pedalboard 24 separately or can 
operate them simultaneously. He can also operate one or more keys or 
pedals and their associated electrical switches simultaneously to create 
certain desired harmonious tones which the machine is capable of 
producing. 
Further, with respect to the keyboard 23, FIG. 9, each key 87 and 88 
carries an upward motion stop element 121 which engages the bottom of the 
key bumper 123. The key bumper is anchored and supported by a screw 122, 
as shown. The keyboard also includes a pan 124 connected to sides 125. 
It should further be noted that the solenoids 57 on the shelf 55 are 
enclosed within an acoustically insulated rectangular enclosure 126 which 
suppresses sound generated by the solenoids during the operation of the 
machine. As shown in FIGS. 4 and 5, a third vertical panel 126' encloses 
the area beneath the solenoid shelf 55. 
Operation 
In the operation of the electro-mechanical stringed bass machine, in the 24 
volt DC power cable 120, the ground lead wire is commonly connected with a 
negative terminal of each solenoid 57. The positive lead wire of cable 120 
is connected to dual lead wires of the cables 92 and 115 for the keyboard 
23 and pedalboard 24, respectively. Should current flow require 
adjustment, an adjustment means 127, FIG. 10, is provided in the control 
box 20. 
At the keyboard 23 and pedalboard 24, current flows through the contacts of 
the individual key and pedal switches 90-91 and 105 when the various keys 
and pedals are depressed by the musician. The current then returns to the 
positive terminals of the corresponding solenoids 57 which directly 
control the piano action including the hammer heads 73 which strike the 
guitar strings 47 to produce musical sounds and the dampering heads 76. 
The musician, by operating the remote keyboard 23 and/or pedalboard 24 is 
able to produce a unique sound of tonal quality and effect by a method not 
known to exist in any other instrument. 
It is to be understood that the form of the invention herewith shown and 
described is to be taken as a preferred example of the same, and that 
various changes in the shape, size and arrangement of parts may be 
resorted to, without departing from the spirit of the invention or scope 
of the subjoined claims.