Acoustic member mounting means for use in typewriters

An acoustic member mounting means for use in typewriters and similar machines wherein the mounting means includes first and second vibration insulating means which prevents undesired sound waves from being generated in the acoustic member.

CROSS-REFERENCE TO RELATED APPLICATIONS 
There are no presently pending related patent applications. 
BACKGROUND OF THE INVENTION 
(1) Field of the Invention 
This invention is used in a typewriter or similar machine in which an input 
signal generates sound waves in an acoustic member which are then 
converted into electrical pulses for controlling various typewriter 
functions. In order to make certain that sound waves are generated only by 
the input signals, means are provided for insulating the acoustic member 
from sound wave producing vibrations which would otherwise occur as a 
result of typewriter operation. 
(2) Description of the Prior Art 
Among the prior art patents which disclose a device for protecting an 
acoustic element from external vibration is the patent of R. E. Franklin 
et al, U.S. Pat. No. 2,542,651. This patent discloses a first insulating 
material 2 which holds a crystal plate-like vibrating element 1. The 
insulating material 2 is held in place by metal springs 7 which are 
carried by supporting yoke 6 preferably formed of insulating material. 
Another such prior art patent is the patent of D. M. Kitterman, U.S. Pat. 
No. 2,802,955, which discloses a first insulating element comprising 
plate-like members 84 and 86 secured to a base slab 88 for mounting 
crystal element 10. A second insulating element, base plate 16, is also 
provided. Among the prior art patents which disclose spring supports for 
objects such as machinery, is the patent of A. Franceschetti, U.S. Pat. 
No. 2,702,703. This patent discloses in FIG. 5, for example, a spring 
support formed of a number of metal plates 9 and rubber elements 8 
arranged in series. The patent of H. Krauss et al, U.S. Pat. No. 
3,548,964, discloses means for limiting movement of an elastically 
suspended engine unit comprising a first rubber cushion 28 on which a 
frame 30 is mounted, and a member 22 which connects first rubber cushion 
28 to a second rubber cushion 36, 37. 
None of the aforementioned patents, however, disclose a device similar to 
the invention disclosed herein for protecting an acoustic element from 
external vibrations. 
SUMMARY OF THE INVENTION 
The present invention is concerned in general with a typewriter or similar 
machine wherein input signals generate sound waves in an acoustic member 
which are then converted into electrical signals to control the typewriter 
functions. More particularly, the invention is concerned with a mounting 
means for such an acoustic member wherein the mounting means includes, 
among other things, a first insulating member in which the acoustic member 
means is affixed, a member which supports the first insulating member, and 
a second insulating member on which the support member is mounted.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
In FIG. 1 there is shown an acoustic member 2 in the shape of a rod having 
a number of teeth 4. In the illustrated embodiment the teeth 4 are of two 
different configurations, a first tooth configuration is shown at 6 and a 
second tooth configuration is shown at 8. Acoustic member 2 is located 
substantially perpendicular to and spaced from a series of strikers 10. 
Although only several strikers 10 are illustrated, there are separate 
strikers 10 for each tooth 4. Acoustic member 2 extends transverse to the 
typewriter keyboard (not shown) and the teeth 4 of acoustic member 2 are 
positioned with respect to strikers 10, so as to receive an impact blow 
from upward movement of strikers 10. A particular striker 10 will be moved 
upwardly into contact with teeth 4, as its corresponding keybutton 12 is 
depressed. When any striker 10 impacts its corresponding tooth 4, two 
sound waves are induced in acoustic member 2. One sound wave travels in 
the direction of transducer means 14, and the other sound wave travels in 
the direction of transducer means 15. Transducer means 14 and 15 are 
operatively connected to each end of acoustic member 2 and receive and 
convert the sound waves into corresponding electrical pulses. A time 
interval exists between the arrival time of the electrical pulses to a 
logic means (not shown), since the distance each divergent sound wave must 
travel toward the transducing means 14 and 15 is different. The logic 
means is provided with circuitry capable of sensing the arrival of each 
electrical pulse and measuring the difference in time of arrival of each 
pulse. Each striker 10 impacting its corresponding tooth 4 creates its own 
such time interval, and by measuring the time interval, the particular 
striker 10 which caused the generated pulses may be determined. 
The means for mounting acoustic member 2 include a number of supports 16. 
It has been found desirable to employ three such supports; one support 
being located at the center of the acoustic member 2, and the two other 
supports located at the ends of the acoustic member 2. As seen in FIG. 2, 
support 16 includes a support member 18 having an opening 19 therein which 
may be U-shaped. A first insulating member 20 which may also be U-shaped 
is secured in the opening 19 of support member 18. First insulating member 
20 may be a foam material such as the high density cellular polyurethane 
material sold under the trademark PORON by the Poron Division of the 
Rogers Corporation, East Woodstock, Connecticut. The durometer hardness of 
the first insulating member 20 is less than the durometer of a second 
insulating member 26, hereinafter described. 
The durometer hardness is the hardness of a material as measured by a 
durometer which is an instrument consisting of a small drill or blunt 
indentor point under pressure. 
The first insulating member 20 is secured in the opening of support member 
18 by a gummy or rubber adhesive. The first insulating member 20 should 
have a non-porous skin to prevent absorption of the adhesive. Absorption 
of the adhesive into the first insulating member 20 is undesirable because 
such absorption hardens the insulating member 20, and reduces its 
capability to absorb vibration. 
Acoustic member 2 is affixed in an opening 21, which may also be U-shaped, 
in first insulating member 20 by the same adhesive which secures first 
insulating member 20 in the opening 19 of support member 18. Acoustic 
member 2, first vibration insulating member 20, and support member 18 are 
located in a substantially vertical plane. It has been found desirable to 
completely surround acoustic member 2 with first insulating members 20, 
leaving only teeth 4 exposed. It has also been found desirable to provide 
insulating members 20 only at discrete positions along acoustic member 2, 
rather than to provide insulating material along the entire length of 
acoustic member 2. It is believed that providing insulating material along 
the entire length of acoustic member 2 would undesirably dampen the travel 
of the sound waves. 
Support member 18 has a tab portion 22 including an opening 24 therein. 
Second insulating member 26 which may be in the shape of a rubber grommet 
having an upper portion 28 and a lower portion 30 is inserted into opening 
24 of tab portion 22, so that upper portion 28 of second insulating member 
26 is above tab portion 22 and lower portion 30 of second insulating 
member 26 is below tab portion 22. The second insulating member 26 may be 
of a gum or rubber material of the type manufactured by the Lavelle Rubber 
Company of Chicago, Ill. 
A pin 32 extends through an opening in rubber grommet 26, and also extends 
through an opening 36 in typewriter frame member 38 which is shown in FIG. 
2 to be a typewriter keylever extrusion. 
A retainer 40 located in notches 42 of pin 32 retains pin 32 and thus the 
rubber grommet in typewriter frame member 38. It has been found desirable 
to provide a space 44 between a shoulder 46 of pin 32 and the bottom of 
the typewriter frame member 38 for the purpose of compressing the rubber 
grommet varying amounts during the assembly of the rubber grommet to the 
frame 38. 
It will be understood that various changes in the details, materials and 
arrangements of parts which have been herein described and illustrated in 
order to explain the nature of the invention may be made by those skilled 
in the art within the principle and scope of the invention as expressed in 
the appended claims.