US 3719902 A
An improved key switch of the type suitable for use with a keyboard wherein a pair of axially aligned coils adapted to be inductively coupled with each other are disposed adjacent to an actuator having means for effectively changing the circuit geometry of the coils. The actuator is moved axially of the coils to cause movement of the changing means so as to effectively vary the inductive coupling or mutual inductance between the coils. The actuator is biased in one direction and one of the coils can form a part of a tuned circuit of an oscillator. The changing means can comprise a metallic ring which forms a shorted turn of a coil or can be a shiftable core.
Description (OCR text may contain errors)
United States Patent 1191 Esterly 1 March 6, 1973  KEY SWITCH 2,913,688 11 1959 Slebodnik et a1. ..336/130X 1 Invent Henry 111899022321 Cuperflm 3133522 111323 22222;:31:?"""iijiiiiiiiiaiiffliii cupemm, Callf- 95014 3,239,782 3/1966 Henke ..336/75 x  Filed: Jan. 12, 1972 21 App1.No.: 217,250
Related US. Application Data  Continuation of Ser. No. 20,351, March 17, 1970,
 U.S.Cl ..331/117 R, 331/173, 331/181,
334/7, 336/73, 336/75, 336/118, 336/130  Int. Cl. ..H03b 5/12  Field 01 Search....336/73, 75, 77, 117,118,119, 336/130, 132, 136; 334/7; 331/117, 181, 173  References Cited UNITED STATES PATENTS 2,258,147 10/1941 Roberts ..336/75 2,388,295v 11/1945 Shea ..336/75 2,417,097 3/1947 Warsaw .336/136 X 2,435,630 2/1948 Ketcham ..336/136'X 2,656,520 10/1953 Roessler, Jr. ..336/l36 X 2,837,726 6/1958 Pearlman et al ..336/136 X 2,881,402 4/1959 Walker ..336/136 FOREIGN PATENTS OR APPLICATIONS 243,379 0/1926 Great Britain .....336/75 Primary Examiner-John Kominski Attorney-John L. McGannon  ABSTRACT An improved key switch of the type suitable for use with a keyboard wherein a pair of axially aligned coils adapted to be inductively coupled with each other are disposed adjacent to an actuator having means for effectively changing the circuit geometry of the coils.
The actuator is moved axially of the coils to cause movement of the changing means so as to effectively 12 Claims, 5 Drawing Figures PATENTEBMAR 61973 3.719802 I NVENTOR HENRY N. ESTERLY ATTORNEYS PATENTEUMAR ems 2 SHEETZUF 2 fle C 58 25 I 25 as 5| 29 32M Zj INVENTOR.
LHENR'Y'N. ESTERLY BY ATTORNEYS '1 KEY SWITCH This is a continuation of Ser. No. 20,351, filed Mar. 17, 1970 now abandoned.
This invention relates to improvements in key switches of the type used in electric typewriters, adding machines, electronic organ keyboards and the like.
The present invention is directed to an improved key switch which utilizes a shiftable actuator associated with a pair of adjacent coils wherein the actuator has means thereon which is capable of effectively changing the inductive coupling or mutual inductance between the coils so that, when one of the coils forms a part of the tuned circuit of an oscillator, movement of the actuator will cause changes in the circuit constants of the oscillator. Thus, the conditions necessary for oscillation can be created or removed depending upon the direction in which the actuator is moved. In this way, the oscillator can be made to operate or not operate to satisfy certain predetermined criteria.
The key switch of the invention can be used with semiconductor components or integrated circuit devices and even can contain circuitry within the confines of its structure. Thus, the key switch can be modular in form so as to facilitate assembly and disassembly when such is required. Moreover, because it can be used with solid state devices rather than mechanical contacts, the key switch is essentially bounce-free, corrosion-free, arc-free, vibration-free and wear-free. The key switch can be utilized in a-manner suchthat false triggering of the switch will not occur by noise originating either internally or externally of the switch. The switching effect of the key switch is dependent upon the geometry of the coils and the means for effectively changing the inductive coupling between the coils, such geometry being essentially fixed so that the key switch is more reliable and constant in operation than if it depended on a spring constant, upon permanent magnets which can lose their charge, or upon a light beam and threshold which could lost its brightness or be confused by stray light, dust, vibration or condensation of moisture.
The key switch of this invention is an active single channel device rather than a passive device. Because of this feature, it lends itself to being disabled in microseconds. Thus, a group of such key switches forming a keyboard, for instance, can be operated sequentially at'relatively high speeds without generation of errors. Also, since it is a single channel device, the operation of the key switch occurs at a discrete instant' in time so as to provide a substantially pulse type output as long as the key switch is actuated.
The primary object of this invention is to provide an improved, actuatable key switch which operates to effectively change the circuit geometry of a pair of adjacent coils so that, when one of the coils forms a part of the tuned circuit of an oscillator, the circuit constants of the oscillator can be changed to thereby permit the conditions for oscillation to be created or removed depending upon the way the key switch is actuated.
Another object of this invention is to provide a key switch of the type described wherein the coils are mounted in axial alignment with each other adjacent to an actuator which moves axially of the coils to shift a device capable of changing the circuit geometry of the coils so that, in one position of the actuator, the mutual inductance between the coils will be at a first value and, at a second positions of theactuator, the mutual inductance between the coils will be at a second value.
Other objects of this-invention will become apparent as the following specification progresses, reference being had to the accompanying drawings for an illustration of the invention.
In the drawings:
FIG. 1 is a perspective view of the key switch of this invention;
FIG. 2 is an enlarged, cross-sectional view taken along line 22 of FIG. 1;
FIG. 3 is an enlarged, cross-sectional view taken along line 3-3 of FIG. 1;
FIG. 4 is a schematic diagram of the circuitry for use with the key switch; and
FIG. 5 is a fragmentary cross-sectional view of another form of the key switch.
The key switch forming the subject matter of this invention is broadly denoted by the numeral and includes an outer, cylindrical housing 12 mounted on a circular base 14 in the manner shown in FIG. 2. Housing 12 has a circular opening 16 at one end thereof and a sleeve 18 which surrounds the opening, the opening and sleeve receiving cylindrical stem 20 of a cylindrical actuator 22 which is shiftably mounted within housing 12 and biased toward opening 16 by a coil spring 24. A key tab 26 is rigidly connected to the outer end of stem 20 whereby actuator 22 can be manually depressed so as to be caused to move toward base 14 against the bias force of spring 24. Release of the manual pressure permits'the actuator to return to the position shown in FIG. 2 under the influence of the bias force of spring 24.
A clip or retainer ring 30 is removably received within an annular groove 32 in the inner surface of housing 12 and provides the means whereby base 14 is coupled with housing 12. Ring 30 is put into place in groove 32 after actuator 22, spring 24, base 14 and a coil support, hereinafter described, have been put into housing 12.
The base has a number of terminals 34 projecting outwardly therefrom for making connection to a female socket or other component. Terminals 34 connect to circuitry within the housing as hereinafter described. 7
Base l4'has an annular, generally flat surface 36 against which one end of coil spring 24 abuts. Thus, the spring biases the base against ring 30. Base 14 also has an annular groove 38 for receiving one end of a cylindrical mount 40 as shown in FIG. 2. The mount is secured in any suitable manner to the base so that the mount is substantially concentric with actuator 22. A pair of inductance coils 42 and 44 are wound on mount 40 adjacent to the inner end thereof, the coils being axially spaced from each other and being so located so that they are inductively or magnetically coupled with each other when an electrical current flows through one of the coils. A core 46 of magnetically permeable material is carried by mount 40 adjacent to the upper end thereof. A suitable ferrite material can be used to form the core.
Actuator 22 has a first cylindrical section 48 which is concentric with mount 40 and defines a central recess 50 within which mount 40 and coils 42 and 44 are disposed. A metallic, circular ring 52 is carried on the inner surface of section 48 and has a transverse dimen sion greater than that of coils 42 and 44 whereby ring 52 can surround a coil in the manner shown in FIG. 2. The ring is preferably formed from a suitable material, such as steel or the like, which has an effect on the circuit constants of the coils, specifically the inductive or magnetic coupling or mutual inductance between the coils depending upon the location of the ring relative to the coils. In the initial position of FIG. 2, the ring surrounds coil 42. When actuator 22 is depressed, the ring is moved to the dashed line position spaced a distance from both coils. Thus, the inductive coupling or mutual inductance between the coils is effectively changed as the ring moves from the full line position to the dashed line position. Conversely, the change will be reversed as the ring returns to its initial position as actuator 22 I moves under the bias force of spring 24.
Actuator 22 has a second tubular section 54 which is 54 is cylindrical as is housing 12 so that the outer surface of actuator 22 and the inner surface of housing 12 are substantially 'complemental to each other. The housing thus serves to guide the actuator as it moves within the housing.
Spring 24 is disposed within the space between tubular sections 48 and 54 as shownin FIG. 2. The end of the spring nearest opening 16 abuts the inner end face 56 of this space. The spring, when in the position shown in FIG. 2, will be slightly compressed to exert a bias force on actuator 22 in the direction of opening 16.
Circuitry can be provided for key switch within mount 40, the circuitry being shown for purposes of i1- lustration in FIG. 2 in block form and denoted by the numeral 58. The circuitry can include an oscillator which utilizes coils 42 and 44, the oscillator being shown schematically in greater detail in FIG. 4. The circuitry includes a transistor 60 whose base is connected by a lead 62 to one end of coil 44. The opposite end of the coil is connected by a lead 64 to a lead 66 which is the high side .of a 2 volt power line.
The collector of transistor 60 is connected to one end of coil 42, the opposite end of. the coil being connected to a lead 68 which forms the high side of a 12 volt power line. The low side of each of the power lines can be denoted by lead 70. A capacitor 72 across coil 42 provides a tuned'circuit for the oscillator. The oscillator is. completed by connecting the emitter of transistor 60 to lead 70 through a resistance 74.
Ring 52 acts to provide a short circuiting turn for coil 42 when the ring is in the full line position of FIG. 2. Thus, the Q of the tuned circuit. is too low to permit oscillations to be sustained. When actuator '22 is depressed, the ring moves to the dashed line position or thereabouts to uncouple the ring from the magnetic circuit to thereby raise the Q of the circuit. When the Q of the circuit is sufficiently high, the oscillations commence and are maintained until the actuator returns to its initial position, whereby the Q of the tuned circuit is once again returned to a value which is too low for oscillations. When ring 52 is in the dashed line position of FIG. 2, the regenerative signal induced in coil 44 by coil 42 causes transistor 60 to oscillate.
While an oscillator has been shown and described with key switch 10, it is clear that other circuitry can be used with the key switch, if desired. Also, the oscillator of key switch 10 can be used with circuitry of the type shown in U. S. Pat. No. 3,413,623, issued to Henry N. Esterly on Nov. 26, 1968.
Ring 52 can be formed of any suitable metallic material which is a good electrical conductor. The material does not have to be magnetic but a magnetic material does make the ring more effective. Iron has been found to be suitable for this purpose.
In use, key switch 10 can be used with itself or with other identical key switches in a system such as in a typewriter, an adding machine or an electronic organ keyboard. The circuit denoted by the numeral 58 will be disposed within housing 12 and the circuit can be connected by pins 34 to other components of the system.
When tab 26 is depressed, actuator 22 is moved toward base 14 against the bias force of spring 24 to thereby carry ring 52 from the full line position of FIG. 2 to the dashed line position thereof. The ring, therefore, moves to a location at which it has little or no effect on the inductive coupling between coils 42 and 44 so that the conditions necessary for oscillation will be established so that a regenerative signal is induced in coil 44 by coil 42 to cause transistor 60 to oscillate. An output signal will then exist at the output terminal connected to the collector of transistor 60. Release of the actuator causes the latter to return to the full line position of FIG. 2, thereby removing the conditions for oscillation.
While the foregoing description has been made with respect to the movement of ring 52 to change the magnetic coupling between coils 42 and 44, it is clear that, in the absence of ring 52, core 46 can be made so that it is movable with actuator 22 in a manner to change the magnetic coupling between the coils. Thus, core 46 can be coupled to the inner end face 102 of actuator 22 by a link 103, as shown in FIG. 5, so that the core is moved downwardly and out of a location where the core has a major effect on the inductive coupling between the coils. Thus, movement of the core out of such a position will cause the condition necessary for oscillations to be established so that transistor 60 will be caused to oscillate and thereby assure the presence of the output voltage at the output terminal connected to the collector of transistor 60.
Key switch 10 can be of any size and stroke. A typical size for the key switch includes a maximum diame- 'tioned input voltages is 12 volts peak-to-peak at 2.5
megahertz. The rise time is approximately 0 to 60 percent of the output voltage in less than 200 microseconds. The life of the key switch is limited only by mechanical wear and can be made so that the switch can be actuated over one hundred million times without replacement.
The present invention is well-suited for the purpose of providing an improved key switch. When the invention is used as part of an oscillator, the short-circuited turn, namely, ring 52, is normally present in the sensing region" of the oscillator, the sensing region being about the coil forming a part of the tuned circuit of the oscillator. This shortcircuited turn induces so much loss in the oscillator circuit and reduces the inductance of the circuit coupled to it so that the oscillator circuit cannot sustain oscillations. In other words, the Q of the circuit, the ratio of the inductive reactance to the resistance of the tuned circuit, is low. When this shortcircuited turn is removed from the sensing region and when other conditions for oscillations are present, then oscillations will commence and be maintained until the short-circuited turn is returned to the sensing region.
Electrically, it would be feasible to open or close the turn so that it would be or would not be short-circuited but, by so designing it, one of the most important features of the present invention would be defeated, namely, that no electrical contacts need be made which would be 'subject to corrosion, wear and contact bounce.
In the present invention, the key switch provides a mechanism which by moving the relative positions of the inductive or resistive circuit elements of an oscillator, the oscillator can be caused to go into or out of oscillation without the necessity of making or breaking electrical contacts. The present form of the oscillator is a Hartley type oscillator which is inhibited from oscillating by the short-circuited turn closely coupled to the two coils. When the actuator of the key switch is depressed, the short-circuited turn is sufficiently far removed from the oscillators coils so that the oscillator can oscillate. Restoring the short-circuited turn to the proximity of the oscillator coils will again block the oscillations.
The foregoing is the preferred form of the oscillator because the blocked oscillator state is less sensitive to external influences or noise. It is also preferred because, if it is desired to block out all key switches of a keyboard, there is always the opportunity to bias the oscillators of the key switches to off positions.
Another advantage of the key switch of this invention is that the oscillator, when the conditions for oscillations have been established, can reach full oscillation rapidly and the oscillatory state of the oscillator produces a strong signal which can be easily recognized by conventional detection means and which will not normally require amplification to provide a useful signal to detectors or to logic elements coupled with the switch.
Actuator 22 may be provided with an extension 23 which depends from the lower annular edge 25 thereof desired to prevent switch 10 from being actuated when another switch is being actuated. This can be accomplished by causing a crank element 27 to move from a retracted position, shown in full lines in FIG. 2, to an operative position shown in dashed lined by the operation of a power device 29 such as a solenoid or the like. Device 29 has an arm 31 pivotally secured to element 27. In its operative position, crank 27 underlies extension 23 and prevents it from moving downwardly. Thus, actuator 22 will be prevented from being moved. Element 27 can be coupled in any suitable manner to structure adjacent to key switch 10 such as by a pin 33. Device 29 is also carried by the adjacent structure.
In the claims:
1. A key switch comprising: a support having a coil thereon, said coil adapted to define a part of a tuned circuit for use with an oscillator; an actuator shiftably mounted on the support for movement relative to the coil into and out of a predetermined operative position; means biasing said actuator in one direction; and a conductive ring carried by the actuator and movable therewith, said ring defining a short-circuit turn for said coil to thereby effect minimization of the Q of said tuned circuit when said actuator is in said operative position and as said coil forms a part of said tuned circuit, said ring being operable to effect an increase in the Q of said tuned circuit as the actuator moves out of and away from said operative position.
2. A key switch as set forth in claim 1, wherein said ring has a transverse dimension permitting it to surround said coil.
3. A key switch comprising: a base; a support carried by the base; a pair of coils wound on the support and capable of being magnetically coupled with each other; a conductive ring; means mounting said ring on said base for movement axially of the coils from a first location at which said ring defines a short-circuit turn for one of the coils to a second location at which the ring is sufficiently spaced from said one coil to avoid defining a short-circuit turn therefor; and means biasing said ring toward one of said locations.
4. A key switch as set forth in claim 3, wherein said ring is metallic and has a transverse dimension permitting it to surround the coils.
5. A key switch as set forth in claim 3, wherein said mounting means includes a tubular member having a central recess for surrounding the coils, said ring being within said recess, said biasing means including a coil spring externally of said central recess and abutting the base and the member.
6. A key switch as set forth in claim 5, wherein said member has a cylindrical recess spaced from and'surrounding said central recess, said coil spring being disposed in said cylindrical recess.
7. A key switch as set forth in claim 5, wherein said member has a cylindrical outer surface, and wherein is included a housing carried by said base in surrounding relationship to said member, said housing having an inner surface complemental to said outer surface and in proximity thereto to provide a guide therefor.
8. A key switch as set forth in claim 3, wherein is included a magnetic core within said coils.
9. A key switch as set forth in claim 3, wherein is included an amplifier carried by the base and coupled with said coils.
10. A key switch comprising: a base; a housing mounted on the base and extending upwardly therefrom, the housing having an opening in the upper end thereof; a shiftable member mounted within the housing for movement longitudinally thereof and having a stem extending through said opening; means biasing the member toward said opening; a pair of coils; means mounting the coils on the base and in proximity to each other to permit the coils to be inductively coupled with each other when an electrical current flows through one of the coils, said member having a central recess for receiving the coils and at least a portion of said coil mounting means, one of the coils adapted to define a part of a tuned circuit of an oscillator; and an electrically conductive ring carried by the member and movable therewith, the ring being disposed for movement into and out of a location at which it defines a short-circuit turn for said one coil when said member moves toward and away from said opening, said ring being operable to minimize the Q of said tuned circuit when said one coil forms a part of the same and as said member is adjacent to said opening and being operable to optimize the Q of said circuit as said member moves away from said opening.
11. A key switch comprising; a support; an electronic oscillator having a tuned circuit and a coil defining a part of said tuned circuit; an actuator shiftably mounted on the support for movement relative to the coil into and out of a predetermined operative position; means biasing said actuator in one direction; and a conductive ring carried by the actuator and movable therewith, said ring linking closely with the magnetic flux in said coil and approximating a short-circuited turn for said coil to thereby effect minimization of the Q of said tuned circuit when said actuator is in said operative position, said ring being operable to link a smaller amount of magnetic flux of the coil to thereby effect an increase in the Q of said tuned circuit as the actuator moves out of and away from said operative position.
12. A key switch comprising: a base; a support carried by the base; an electronic oscillator having a tuned circuit and employing a pair of coils wound on the support, said coils capable of being magnetically coupled with each other; a conductive ring; means mounting said ring on said base for movement axially of the coil from a first location at which said ring closely couples with the magnetic flux of at least one of the coils to approximate a short-circuited turn for said one coil to a second location at which the ring is sufficiently spaced from said one coil to avoid acting thereon as would a short-circuited turn therefor, said oscillator being switched to an off condition when said ring is in said first location and being switched to an on condition when said ring is in said second location; and means biasing said ring toward one of said locations.