U.S. patent number 3,586,888 [Application Number 04/866,802] was granted by the patent office on 1971-06-22 for impact transducer switch.
This patent grant is currently assigned to Sperry Rand Corporation. Invention is credited to Walter Dorfman.
United States Patent |
3,586,888 |
Dorfman |
June 22, 1971 |
IMPACT TRANSDUCER SWITCH
Abstract
An impact transducer switch includes a manually operable key, an
energy storage spring, and a piezoelectric element. Upon actuation
of the key, means is provided for moving said spring through a
first range of movement where energy is stored in said spring, and
for thereafter effecting release of said spring at a predetermined
point to cause release of said energy and impact of said
piezoelectric element to cause an electrical signal to be generated
by said piezoelectric element. In one form, an end of the energy
storage spring impacts the piezoelectric element, while in another
form, the spring transfers the energy to an impact means which in
turn causes the impact.
Inventors: |
Dorfman; Walter (Warminster,
PA) |
Assignee: |
Sperry Rand Corporation (New
York, NY)
|
Family
ID: |
25348445 |
Appl.
No.: |
04/866,802 |
Filed: |
October 16, 1969 |
Current U.S.
Class: |
310/339; 335/205;
200/181 |
Current CPC
Class: |
H03K
17/967 (20130101); G06C 7/02 (20130101); H03K
17/964 (20130101); F23Q 3/002 (20130101) |
Current International
Class: |
H03K
17/967 (20060101); H03K 17/94 (20060101); H03K
17/96 (20060101); G06C 7/02 (20060101); G06C
7/00 (20060101); H04r 017/00 () |
Field of
Search: |
;310/8.3--8.7
;317/81,79PE ;200/160,67F ;335/205 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Hirshfield; Milton O.
Assistant Examiner: Budd; Mark O.
Claims
What I claim as my invention and what I desire to secure by Letters
Patent is:
1. An impact transducer switch comprising: manually operable key
means; an upper housing having first and second vertical guide
walls; actuator means having an upper portion connected to said key
means, and including a first recessed cavity at the lower portion
thereof, and a lower portion separated from said upper portion and
having a second recessed cavity at the upper portion thereof; an
energy storage compression spring having a first end contained
within said first cavity and a second end contained within said
second cavity; a lower housing; a piezoelectric element mounted
within said lower housing, for generating an electrical signal upon
impact thereof; a permanent magnet secured to said upper housing;
and impact means, communicating with said lower portion of said
actuator means, and normally retained by said permanent magnet
during a first portion of movement of said actuator means, said
first portion of movement compressing said spring to store energy
therein, and being further operable to overcome the attractive
force of said magnet and impact said piezoelectric element after a
predetermined movement of said actuator means.
2. The invention defined in claim 1 wherein said impact means has a
shape adapted to define the amplitude and pulse width of said
electrical signal.
3. An impact transducer switch comprising: manually operable key
means; an energy storage flexure spring having first and second end
portions; a piezoelectric element spaced apart from said second
spring end portion, for generating an electrical signal upon impact
thereof; a permanent magnet for normally attracting and retaining
said second end portion of said spring; actuator means, movable by
said key means, for deflecting said first spring end portion to
store energy in said spring and for thereafter effecting release of
said second spring end portion to cause said impact, said first end
portion of said spring being in contact with said actuator means;
and a return spring having a first fixed end and a second end in
contact with said first end spring portion and said actuator means.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a switching device, and more
particularly to an impact transducer switching device adapted for
use in a keyboard.
The prior art discloses a variety of switching units adapted for
use as data entry devices. In one common form of use, these
switching devices are used as actuating elements for a keyboard.
The keyboard generally comprises a plurality of individual keys
coupled to a switching unit which upon actuation of the key causes
an electrical or other signal to be generated and encoded into a
group of discrete signals having a unique combination signifying
the designation of the actuated key. A typical and common use of
such a keyboard is as an input device in the data processing
system.
These prior art devices require an external electrical power
source. In many forms, the electrical power source is coupled to a
load through a plurality of normally open electrical contacts, and
actuation of the key effects a contact and closure, connecting the
power source to the load, thereby generating an output signal. In
these types of devices the moving electrical contacts incur an
attendant deterioration due to arcing, erosion and normally
occuring atmospheric contaminants. It is one object of the present
invention to eliminate the requirement of an external electrical
power source, and also to eliminate moving electrical contacts.
Another disadvantage of prior art devices is that the output from
the key actuated element is of a continuous rather than of a pulse
type nature and generally has a low voltage or current level. The
low signal level generally causes the keyboard to require
amplifying means to raise the signal strength to a level sufficient
to assure operation by and of the remainder of the data processing
system. Hence, it is another object of the present invention to
provide a data entry device having a pulse output rather than a
continuous type output, and a substantially high signal level which
is capable in itself of initiating a following action by the data
processing system.
Another disadvantage of prior art devices is the absence of true
overcenter action, and the ability of the key to be teased. True
overcenter action and the inability to be teased are important,
since the feel of the key should approach that of a high quality
typewriter, allowing the keyboard operator to have a true feel of
the actuation of the key and the concurrent generation of an
electrical signal. Hence it is another object of the invention to
provide a data entry device having true overcenter action and
inability to be teased.
STATEMENT OF THE INVENTION
According to a salient feature of the present invention, an impact
transducer switch comprises: manually operable key means; actuating
means movable by said key means; an energy storage spring movable
between first and second positions by said actuating means, and
operable to store energy during a first portion of said movement
and to release said stored energy during a second portion of said
movement; a piezoelectric element for generating an electrical
signal in response to impact thereof; impact means for transferring
said stored energy upon release thereof by impact with said
piezoelectric element; and holding means for maintaining said
impact means spaced apart from said piezoelectric element during
said first portion of said spring movement, and responsive to said
actuating means for releasing said impact means after a
predetermined movement of said actuating means.
DESCRIPTION OF THE DRAWINGS
Other objects and advantages of the invention will further become
apparent upon description of the various features and aspects of my
invention, in conjunction with the accompanying drawing, in which
like reference numerals identify like components, and in which:
FIG. 1 is a schematic drawing in perspective view showing an
assembled switch embodying the principles of the invention;
FIG. 2 is a schematic drawing showing another embodiment of the
invention.
FIGS. 3 and 4 are schematic drawings depicting another embodiment;
and
FIG. 5 depicts alternative impact means which may be used with the
switch shown in FIGS. 3 and 4.
DETAILED DESCRIPTION OF THE INVENTION
Referring to the drawings and in particular to FIG. 1, there is
shown a keyboard having a keyboard surface 10 and keyboard body or
panel 12 which may be an insulating or metallic but preferably
nonmagnetic material. The panel 12 has a plurality of slots 14, one
at each key position, each slot acting as a plunger guide for the
actuator. The actuator may include a keystem 18 which is
mechanically affixed to a key cap 16, and which is guided by the
body walls 13 and 15 of the keyboard panel 12. A return spring 20
is disposed about the reduced top portion 21 of plunger or keystem
18, and is interposed between the lower surface 17 of key cap 16
and the upper surface 10 of panel 12. It should be appreciated that
the body walls 13 and 15 may be variously dimensioned. For example,
in FIG. 1 body wall 15 is substantially longer than the body wall
13. In this form, the guide means may be effectively utilized for
restraining movement of the plunger stem in a vertical movement
along the path of travel depicted by the multidirectional arrows
28.
Affixed to the lower portion of the keystem 18 is a permanent
magnet 22. Disposed adjacent the left side of the keystem 18 is an
energy storage flexure spring 24, the upper portion of which may be
relatively fixed at a permanent location such as the block 25 by
securing means such as the screw 26. As the keystem 18 and top
portion 21 are moved in a downward direction by manual depression
of the key cap 16, the permanent magnet 22 is operative to attract
the flexure spring 24 to the right. As the energy storage flexure
spring is moved between its initial at rest or first position
toward the right side, energy is stored in the spring due to the
attraction by the magnet 22. The force of attraction between magnet
22 and flexure spring 24 is of a predetermined value, and at a
predetermined position during the downward path of travel of
keystem 18, the force of attraction between magnet 22 and flexure
spring 24 is exceeded by the energy stored in the flexure spring
24. The flexure spring 24, which travels along an arcuate path
depicted by the multidirection arrows 30, is operative to store
energy therein during the first portion of its movement between the
initial at rest or first position and the point to the right of the
at rest position at which the snap action of the spring, due to
energy stored therein, creates a force which exceeds the attractive
force between the magnet 22 and flexure spring 24. When the energy
stored in the spring exceeds this attractive force, the spring is
released from the attractive force and the energy stored in the
spring is effective to cause the flexure spring to snap toward the
left, whereupon the lower or impact portion 31 of the flexure
spring impacts a piezoelectric element 32 located at a second
position to the left of the lower portion 31 of flexure spring 24.
Piezoelectric element 32 is operable to generate an electrical
signal over connected conductors 34 and 36 in response to impact by
impact portion 31 of flexure spring 24. The electrical signal so
generated is coupled over output conductors 38 and 40 to an
encoding device (not depicted herein) and thus represents an
electrical signal generated in response to depression of the key
cap 16. Thus it can be seen that a relatively small amount of
slowly applied mechanical energy is gathered until a predetermined
level is reached, at which time the energy is temporarily stored in
the flexure spring 24, and there is provided a control means for
releasing the energy stored therein in a relatively short time so
that the power can be obtained in the form of a single high-level
mechanical impact upon a piezoelectric element exhibiting the
ability to convert energy from a mechanical to an electrical
form.
Piezoelectric element 32 may be a crystal, quartz, ceramic, or
other element having the property of being able to convert
mechanical energy to electrical energy. By way of example, one
relatively inexpensive but efficient element which was utilized was
a common crystal phonograph cartridge. A main advantage of such an
element lies in the ability to provide a relatively high signal
level output. By way of example, commonly used piezoelectric
elements can easily produce outputs of 100 volts amplitude, upon
impact by a device such as the impact portion 31 of the flexure
spring 24. By providing a substantially high output level, a
printed encoding matrix such as a capacitive type encoding matrix
can be utilized to provide the requisite encoding to encode the
signal generated at each key station into the required digital
output code which is to be utilized by the remainder of the data
processing system coupled to the data entry device.
FIG. 2 shows another embodiment of the invention. As shown therein,
the keyboard may have a keyboard surface 10 and keyboard body or
panel 52. Panel 52 has a slot at each key position, each slot
having guide walls 54 and 56 serving as a plunger guide for the
actuator. The actuator may include a keystem having an upper
portion 50 secured to the key cap 16 and guided by guide walls 54
and 56 for longitudinal movement, and a reduced lower portion 51. A
return spring 58 may be coupled at one end 44 to the body or panel
52 of the keyboard, and may be disposed to lie in a horizontal or
lateral plane so that the left hand portion of return spring 58
abuts but is not necessarily connected to the lower portion of the
upper keystem part 50. Key cap 16, and keystem portions 50 and 51
may be an integral unit. Lower keystem portion 51 is disposed to
move vertically or longitudinally at its lower end through a bore
in magnetic retentive means or permanent magnet 60, which magnet is
permanently affixed to the keyboard by conventional means (not
shown). There is no relative movement between magnet 60 and panel
52.
Also depicted in FIG. 2 is an energy storage flexure spring 48
having an upper portion 61 permanently in contact with the lower
portion of the return spring 58 which is in turn in contact with
the keystem portions 50 and 51. The lower portion 62 of the energy
storage flexure spring 48 has an impact member 63, and is not
permanently secured to any part of the actuating mechanism, but it
lies in a substantially horizontal plane so that it is in very
close proximity to the lower surface of permanent magnet 60. Hence,
the magnet 60 is operable to attract the lower portion 62 when the
actuating mechanism is at rest. Also shown in FIG. 2 is a
piezoelectric element 64 which lies in a horizontal plane, and is
disposed at a fixed second position. Output terminals 66 and 68 are
secured to opposed surfaces of the piezoelectric element, and are
coupled to output conductors 70 and 72 at the other end
thereof.
In operation, the embodiment of FIG. 2 utilizes the same general
principles as the embodiment of FIG. 1. Thus, prior to manual
depression of key cap 16, the magnet 60 is operative to attract the
lower portion 62 of energy storage flexure spring 48. Upon
depression of key cap 16, the attractive force still restricts
movement of portion 62, but the upper portion 61 is flexed
downward, and this flexure enables energy to be stored in energy
storage flexure spring 48 and in return spring 58 during a
predetermined path of travel of the actuating mechanism. Magnet 60
holds lower portion 62 of the spring as the keystem portions 50 and
51 are moved downward upon depression of the key cap. As the lower
keystem portion 51 contacts the lower portion 62 of the spring, it
applies a downward force thereto, and when this force in
cooperation with the energy stored in spring 48 exceeds the
attractive force between magnet 60 and spring portion 62, then the
stored energy is released, and the lower portion 62 of spring 48 is
operative to rapidly move downwardly and cause impact member 63 of
spring 48 to strike the upper part of piezoelectric element 64,
effecting generation of an electrical signal in response to the
impact.
With both of the FIG. 1 and FIG. 2 embodiments, the impact of an
impact portion of the flexure spring and piezoelectric element
causes respective springs 24 and 48 to exhibit damped oscillatory
movements, so that after the impact, movement of the spring is so
restricted that there is but a single impact with the piezoelectric
element. This is so because the impact absorbs a large part of the
energy stored in each spring. With respect to FIG. 1, flexure
spring 24 returns to its initial at rest position without the aid
of the actuating mechanism, while in the FIG. 2 arrangement,
removal of the downward manual force on key cap 16 causes return
spring 58 to urge flexure spring 48 upward to the initial at reset
position.
Referring now to FIGS. 3 and 4, and in particular to FIG. 3, there
is shown another form which the invention may take. The keyboard
may include a keyboard surface 10 and keyboard top panel 80 having
a slot of each key position, each slot having upper guide walls 82
and 84. The housing for each key or switch may also include side
plates 86 and 88 having respective guide walls 90 and 92 along the
interior portions thereof. The actuator assembly for the switch
includes an upper keystem 94, affixed to key cap 16 at one end
thereof, and guided vertically by guide walls 82 and 84, and also
includes a lower keystem 96, affixed to upper keystem 94. Lower
keystem 96 is guided vertically by guide walls 90 and 92, and 96
has a recessed cavity 98 at the lower portion thereof which
accommodates the upper end of energy storage compression spring
100. Spring 100 may, in a preferred form, be affixed to the top
wall 102 of cavity 98 by conventional means.
Also shown in FIGS. 3 and 4 is a lower actuator assembly which
includes a plunger 104 guided vertically by guide walls 90 and 92,
and having a recessed cavity 106 at the top portion thereof. Cavity
106 accommodates the lower end of energy storage compression spring
100 which in a preferred form need not be affixed to plunger 104.
The lower portion of plunger 104 has formed therein a recessed
cavity 108 which serves as a guide and pressure point for the stem
portion 110 of impact means 112. Cavity 108 is shown in FIG. 4
where the plunger 104 has been raised above its at rest position to
depict said cavity. A magnetically attractable member 114 is
securely fastened to stem 110 and is retained in the initial at
rest position shown in FIGS. 3 and 4 by a permanent magnet 116.
Magnet 116, which contains a bore through the center thereof
allowing for vertical movement of stem 110, is permanently fastened
to side plates 86 and 88.
The lower portion of the key assembly includes a bottom plate 120,
and lower plates 122 and 124, which are adhered to bottom plate
120, and which support and are fastened to side plates 86 and 88
respectively. Adhered to bottom plate 120 is an impact absorbing
means 126 which may be of a material such as rubber. Affixed to the
top of absorbing means 126 is a piezoelectric element 128 which has
a first output lead over conductors 130 and 132 connected through
terminal 134 and a second output lead (not shown) connected to
terminal 136.
In operation, the Impact or switch is shown in the initial or at
rest position of FIG. 3, with actuating members 96 and 104 spaced
apart. As the key cap 16 is manually depressed, upper and lower
keystems 94 and 96 move downward and energy is stored in
compression spring 100 as it is compressed. Impact means 112, stem
110 and plunger 104 are retained in the depicted initial position
due to the attractive force between magnet 116 and magnetically
attractable member 114. As keystem 96 contacts plunger 104 after a
predetermined movement of the upper keystem assembly, the energy
stored in compression spring 100 exerts a downward force that
approaches the attractive force between permanent magnet 116 and
magnetically attractable member 114. Upon a slight further downward
depression of key cap 16, plunger 104 is moved downward and member
114 is stripped from magnet 116. The energy stored in spring 100
forces plunger 104, stem 110 and impact means 112 downward and
impact means 112 impacts the top surface of piezoelectric element
128 causing generation of an electrical signal. The tip of impact
means 112, which may be of a resilient material will rapidly
rebound from piezoelectric element 128, and member 114 will be
attracted to and retained by magnet 116.
Spring 100 also acts as a return spring to return the upper
actuator assembly and key cap 16 to the initial at rest position.
While the rebounding impact means 112 and stem 110 force plunger
104 upward to the initial at rest position.
Another advantage of my invention may be shown by reference to FIG.
5. As depicted therein, the impact means may take one of several
shapes. When a wide and relatively flat impact means 140 is used,
the top surface of piezoelectric element 128 will be impacted over
a relatively wide area, and a relatively low amplitude but wide
pulse is generated. When a relatively narrow impact means 142 is
used, the top surface of piezoelectric element 128 is impacted over
a relatively small area and a large amplitude and relatively narrow
pulse is generated. This is so because the shape of the impact
member determines the area of deformation of element 128, and the
area and depth of deformation determine the output signal shape. A
small and sharp impact member causes a larger, deeper deformation
over a small area and a resultant high amplitude narrow pulse,
while a broad impact member causes a small but wide deformation
pattern and a lower amplitude wide pulse output pulse. Hence the
shape of impact means can be used to control the amplitude and
width of the electrical output signal produced by the switch.
While only certain features and advantages of my invention have
been fully described and illustrated, it should be obvious that
other modifications and alternations may be made therein.
* * * * *