Impact transducer apparatus

[57] ABSTRACT

An impact transducer apparatus comprises a lever means supported within a housing adapted to pivot between first and second positions. A hammer is attached to the lever means and is adapted to strike a piezoelectric element when the lever means is moved from its first to its second position. A magnetic latch including a magnet member is associated with the lever means for restraining movement of the lever from its first to its second position, and a resilient bias means, having a bent portion, biases the lever means towards its second position. A key reciprocal along an axis is connected to the bias means to increase energy in the bias means so that when the energy in the bias means exceeds a design level associated with the magnetic coupling of the latching means, the latching means releases the lever means and the bias means urges the lever means from its first to its second position, thereby causing the hammer to strike the piezoelectric element.

Claims, 6 Drawing Figures

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PATENTED 121974

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IMPACT TRANSDUCER APPARATUS

This invention relates to keyboard apparatus and particularly to keyboard devices capable of generating electric signals upon actuation of a key mechanism.

Alphanumeric keyboard apparatus are useful in association with computer input devices, encoders, and the like. Ordinarily, each key of such keyboard apparatus is associated with a suitable code generating device for generating a unique code upon depression of each key of the keyboard apparatus.

Prior keyboard apparatus have utilized mechanical interconnections to overcome many problems associated with such apparatus. For example, the simultaneous operation of two or more keys by an operator trained for high speed encoding often caused an erroneous code to be established by the encoder. Consequently, mechanical interlocking of the keys was utilized, but this produced a rough, disagreeable touch to the operator. To overcome this problem, some keyboard apparatus utilized key-operable hammers adapted to strike signal generating crystals, such as piezoelectric elements, but these have not been altogether satisfactory because the hammer often “bounced” on the crystal, thereby generating an erratic, spurious electric signal. Further, such keyboard apparatus produced a soft touch, not particularly pleasing to the operator.

Further, refinement in the field of keyboard apparatus resulted in the use of “snap” action hammers operable to strike piezoelectric elements to overcome the problem of bouncing hammers as well as to provide a more pleasing touch to the operator. However, such devices have been cumbersome in that they require extensive mechanical apparatus and a considerable amount of space for each such key. A more thorough discussion of such apparatus may be found in copending application of Marcel Brisebarre and Xavier de Saint Sauveur, for “Impact Transducer Keyboard Apparatus”, Ser. No. 156,146 filed June 21, 1971 and assigned to the same assignee as the present application, now U.S. Pat. No. 3,725,908 granted Apr. 3, 1973.

It is an object of the present invention to provide a signal generating keyboard device which is easily assembled, requires minimal space, and whose operation is pleasing to an operator.

It is another object of the present invention to provide signal generating keyboard apparatus wherein a manually operable key is operable to increase energy stored in a spring, or the like, so that a hammer associated with the spring is biased toward a signal generating device. A magnetic latch restrains the hammer from movement toward the signal generating device until the energy within the spring exceeds a design level, at which point the latch releases permitting the spring to bias the hammer toward the signal generating device to generate a signal.

It is another object of the present invention to provide a key-operable signal generating apparatus having an actuator slidably reciprocal along an axis and which requires a minimal amount of space.

In accordance with the present invention, a keyoperable signal generating apparatus is provided having a manually operable actuator reciprocal along an axis. Bias means is provided so that movement of the actuator along the axis in one direction increases energy within the bias means. Hammer means, associated with the bias means, is magnetically coupled to a first position spaced from a signal generating device in such a manner that when the energy within the bias means ex5 ceeds a design level the magnetic coupling restraining the bias means releases and the bias means urges the hammer means to strike the signal generating means thereby generating an electric signal.

One feature of the present invention resides in the 10 provision of a mechanical coupling between the bias means and the actuator to provide snap action to the apparatus.

Another feature of the present invention resides in the provision of a depressable key apparatus which biases a hammer to strike a signal generating means with uniform force.

The above and other features of this invention will be more fully understood from the following detailed description and the accompanying drawings, in which:

FIG. 1 is a section view of a key-operable signal generating device in accordance with the presently preferred embodiment of the present invention;

FIG. 2 is a section view taken at line 2—2 in FIG. 1;

²⁵ FIG. 3 is a section view taken at line 3—3 in FIG. 1;

FIG. 4 is an orthogonal view of a portion of the apparatus illustrated in FIG. 1; and

FIGS. 5 and 6 are section views of the apparatus, as ³⁰ in FIG. 1, illustrating the manner of operation.

With reference to the drawings there is illustrated in impact transducer apparatus 10 in accordance with the presently preferred embodiment of the prevent invention. Apparatus 10 includes an outer housing 11 having ³⁵ an axis 12 and an inner chamber 13. Housing 14 is fitted within chamber 13 and is axially positioned within the chamber by suitable stops (not shown) on housings 11 and 14. Housing 14 preferably includes planar surface 15 disposed substantially parallel to axis 12 and an ⁰ inclined surface 16. Surfaces 15 and 16 join at junction 17 for purposes to be hereinafter explained. Inclined surface 18 protrudes from surface 15 at an angle different from the angle of inclination of surface 16, for purposes to be more fully understood hereinafter. Piezo⁵ electric crystal 19 is supported by housing 14 and preferably flush with surface 16 and is connected via leads 20 and 21 to end contacts 22 and 23, respectively. Magnet 24 is supported by housing 14 and preferably ₅θ is flush with surface 18. Preferably, and as shown particularly in FIG. 4, housing 14 includes, at each side thereof, a first recessed portion 25 and a second recessed portion 26.

Leaf spring 30 includes first and second arms 31 and ₅₅ 32, respectively, joined at the upper end thereof by a cross arm 33. Lever arm 34, integral with spring 30, extends from the lower end portion 35 of leaf spring 30. Arms 31 and 32 are bent in the region defined by axis 36 so that the upper portion of arms 31 and 32 extend ₆₀ substantially parallel to axis 12, and lever arm 34 extends substantially parallel to the lower portion of arms 31 and 32. The lower end portion 35 of leaf spring 30 is supported at the junction 17 between surfaces 15 and 16 so that the spring may pivot about the axis formed 65 by junction 17. The upper end of lever arm 34 includes a magnetic keeper 38 adapted to be magnetically coupled to magnet 24 and a hammer 37 adapted to strike piezoelectric crystal 19.

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Actuator 40 includes a substantial cylindrical portion 41 extending through bore 42 of housing 11. Shoulder 43 on actuator 40 defines an upper stop against upper surface 44 of housing 11. Actuator 40 includes a pair of downwardly depending arms 45 and 46. Guides 47 on housing 11 guide the travel of actuator 40 along axis 12. Actuator 40 further includes a slot 48 which snugly receives the upper end portion 33 of leaf spring 30. Preferably, each arm 45 and 46 includes a shoulder 49 adapted to bear against respective ones of arms 31 and 32 of leaf spring 30. Manually operable key 50 is attached to the upper end of actuator 40 at cylindrical portion 41.

In operation of the impact transducer apparatus in accordance with the present invention, and particularly with reference to FIGS. 1 and 4-6, manual depression of key 50 causes an axial movement of actuator 40 along axis 12. Axial movement of actuator 40 bends arms 31 and 32 of leaf spring 30 near axis 36, thereby increasing the energy stored within the leaf spring, as 20 shown in FIG. 5. When the energy in leaf spring 30 exceeds a design level, the magnetic coupling between keeper 38 and magnet 24 is overcome by the energy stored within the leaf spring, and the energy within __________ ________, spring 30 causes the spring to pivot about the axis de- 25 mounted to said housing in relationship to said hammer axis 36. By concentrating the bending action of spring 30 to a region between keeper 38 and pivot region 17, substantially all energy imparted to the spring by axial movement of actuator 40 is transferred to the lever arm 34 to overcome the magnetic coupling between keeper 38 and magnet 24 and to pivotally rotate arm 34 to cause hammer 37 to impact against element 19.

The present invention thus provides a transudcer impact apparatus which is reliable in operation, requires minimal space, is easily assembled and manufactured, and which provides a pleasing touch to the operator. The device is reliable in operation, and provides a uniform electric signal output upon each actuation of the key.

This invention is not to be limited by the embodiment shown in the drawings and described in the description, which is given by way of example and not of limitation, but only in accordance with the scope of the appended claims.