Electric Keyboards For Office Machines

Abstract

An electric keyboard includes a plurality of depressible keys each key having at least one movable contact for bearing on a fixed contact. The movable contact of each key is acted by the pressure exerted on a corresponding key-shank. A layer of deformable material is shaped as to form a projection over each shank so as to seal hermetically the key and to define a cavity between the projection and a stationary guide plate in which the shank moves. Each movable electric contact comprises a thin flexible blade fixed at one end and having the opposite end bent to provide an arcuate contact surface. A tongue of the blade bears on a fixed stop located above the line joining the attached end of the blade and the fixed contact to snap between a closed and an open position.

Description

BACKGROUND OF THE INVENTION

The present invention relates to an electric keyboard of an office machine, comprising for each key at least one movable electric contact adapted to close a circuit by bearing on a fixed contact, in which the key is covered by a layer of deformable material suitable for transmitting the pressure exerted to the shank acting on the movable electric contact. Numerous keys employed in electric keyboards of the non-coded type are known. A non-coded electric keyboard merely signals which key has been depressed on a circuit individual to that key. These generally supply at their output terminals an electric pulse, used controlling electronic circuits, for example by means of electric contact.

To effect this electric contact there are normally used a certain number of springs and blades or tongues variously linked to the key and then communicating with the outside of the machine. The assembly of mechanical or electric elements of the key is therefore not hermetically sealed; therefore the key is not protected from penetrating dust or moisture, which with long use damage the same. Keyboards in which the keys are covered by a flexible cover having indicia which differ from the indicia of the keys for selectively adapting the keyboard for diverse operations are known in the art. These keyboards are not provided with electrical contacts, however; nor does the cover furnish a hermetic seal for the underlying keyboard for protecting the contacts from dust and humidity.

SUMMARY OF THE INVENTION

These technical problems are solved by an electric keyboard of an office machine according to the present invention, comprising at least one movable electric contact adapted to close a circuit by bearing on a fixed contact, wherein the layer of deformable material is shaped in such manner as to form a projection over the shank so as to seal hermetically the key and to define a cavity between the projection and a guide plate in which the shank moves the cavity containing a flange integral with the shank.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail, by way of example, with reference to the accompanying drawings, wherein:

FIG. 1 is a view, partly in section, of a keyboard incorporating keys embodying the invention;

FIG. 2 is a median section of a key embodying the invention, on a larger scale;

FIG. 3 is a section on the line III--III of FIG. 1;

FIG. 4 is a section on the line IV--IV of FIG. 1;

FIG. 5 is a view in section of a key according to a variation of the invention;

FIG. 6 is a perspective view of a circuit board with integrated circuits, as in the variation of FIG. 5.

DESCRIPTION OF A PREFERRED EMBODIMENT

The key according to the invention is employed in a numeral keyboard generally used in office electric calculating machines.

The keyboard in FIG. 1 is of the non-coded type and comprises two separate section of keys aligned in different rows. One of these sections is reserved for the keys corresponding to the decimal digits and to the decimal point, the other is reserved for the operative or function keys. The keyboard comprises a layer of deformable elastomeric material 10, for example rubber (FIG. 2), shaped in such manner as to form a projection 33 in the shape of a truncated cone at the location of each of the keys, as is indicated generally by the reference 11. The deformable layer 10 is cemented and therefore adheres, except for the cavities inside the key shapes 11, to a cover plate 12 of rigid plastics material. Below this cover plate, separated by means of spacers 13 (FIG. 3), there is rigidly fixed by means of the screws 14 a plate 15 of insulating material. This plate 15 is parallel to the plate 12 and serves as a support for a printed circuit 17 (FIG. 1).

This printed circuit comprises for each key 11 a fixed electric contact constituted by a conductive plate 18 connected to an encoding circuit not shown in the drawing. Each key 11 comprises a substantially rectangular, thin, flexible, blade 19 of conductive metal (FIG. 2), clamped at one end between the cover plate 12 and a rigid thin plate 20 by means of a screw 21. The blade 19 is bent at the free end in the form of an S-shaped portion 122 in such manner as to produce in its bottom part a small contact surface 22 (FIG. 1).

Tangent to the back of the portion 122 there departs upwardly a rectangular tongue 23 (FIG. 2) bent in a semi-circle, one end 123 of which is free and protrudes below the plane of the same plate 19. This tongue 23 is formed centrally on the width of the blade 19 as may be seen from FIG. 1. Thus, the width of the tongue 23 is less than the total width of the blade 19, the tongue being contained within a small window 24 formed in the blade 19 itself. In correspondence with the semi-circular bent portion 23 (FIG. 2) of the blade 19, the plate 12 is provided with a window 25 in which this bent portion 23 can be contained.

Finally, the free end 123 of the tongue 23 bears on a ledge 127 of a projection 27 integral with the plate 12 and jutting towards the window 25. The tongue 23 bearing in this way on the tooth 27 constitutes a compressed spring which tends to keep the blade 19 tensioned longitudinally. This blade 19 can be depressed by a shank 28 movable vertically within a hole 29 in the plate 12 located on the longitudinal axis of the subjacent blade 19. The shank 28 bears on the blade 19 on top of a resilient projection 30 (FIG. 1) into the window 24 of the blade 19. The shank 28 (FIG. 2) bears an integral flange 31 located above the cover plate 12. The flange forms a surface adapted to be operated with the finger through the head of the key 11.

The flange 31 is contained in an internal cavity 32 formed between the projection or raised portion 33 and the plate 12. The flange 31 is not, however, kept in contact with the surface of the projection 33, but is separated by a space, the utility of which will be examined hereinafter. The shaped projection 33 therefore constitutes the surface on which the pressure for actuating the key 11 is exerted.

The blade 19 can adopt two positions with respect to the projection 27: an upper position and a lower position. The blade 19 is normally located in the high position by the action of the tongue 23. The projection 27 is located above the line joining the point 36 at which the blade 19 is fixed to the plate 12 to the point of contact 22.

When the key 11 is not pressed, the blade 19 bears against the lower surface of the plate 12 in a zone 136. The shank 28 rests on the blade 19 by gravity, but the flange 31, although occupying the highest position in the cavity 32, is not in contact with the layer of rubber 10.

When pressure is exerted on the rubber projection 33 of a key 11, the projection 33 first bends until it touches the flange 31. The rubber of the projection 33, being then pressed further, is compressed and begins to move the flange 31 and the shank 28 downwardly. The rubber therefore causes a slight delay between the moment when the pressing action on the projection 33 begins and the moment when the pressing action on the blade 19 by the shank 28 begins. This delay is useful, since the short stroke necessary for actuating the blade 19 would otherwise cause contacts even with slight and involuntary pressures on the projections 33. The built-in delay, on the other hand, ensures that the contact will in every case be voluntary.

The pressing action of the shank 28 is exerted on the resilient projection 30 (FIG. 1) of the blade 19. In a first stage, this plate bends at the point of attachment of the projection 30 because of the small thickness of the two edges 34, 35, keeping its free end in contact with the plate 12 at the zone 136, however. When the projection 30 reaches and moves beyond the plane of the projection 27, there takes place a snap changeover in the positioning of the blade 19. In fact, the projection 27 is then above the plate 19 and the force of the tongue 23 therefore now suddenly causes the lowering of the free end 22 of the blade 19, which is brought into contact with the subjacent plate 18 of the printed circuit 17 (FIG. 1). The position of the plate 18 with respect to the blade 19 is such as to define a minimum shifting of the same below the ledge 127 to produce the change-over from the previously considered inoperative position.

Upon releasing pressure on the key 11, the blade 19, because of the elastic cantilever action at the point 36 generated on the actuation of the key 11, is suddenly returned towards its high, inoperative position.

The key 11 is so constructed that, even if it is operated by the finger in the peripheral portion of the projection 33, it nevertheless causes the closing of the contact 22, 18. Moreover, with a single blade 19 and without the aid of independent springs, the key is able to generate an electric pulse adapted to control, for example, an encoding circuit. Moreover, the operation of this key does not give rise to rebounds of the point of contact 22 because of the positioning action of the tongue 23.

To produce a keyboard for a calculating machine by means of a plurality of keys 11 as hereinbefore described, all the keys are covered by a common layer of rubber 10 (FIG. 1) in the form of an apron. The keyboard comprises two separate sections 40, 41, of projections 33 each of which corresponds to a key. The section 40 constitutes the usual ten-key numeral keyboard and is formed by 12 projections 33 arranged in four rows, each consisting of three projections 33, while the section 41 constitutes the function keyboard and is formed by eight projections 33 of different forms and dimensions.

The nine projections 33, 133 of the three upper rows of the section 40 are used for the digits from 1 to 9 and of the three projections of the bottom row one is used for the digit 0, another for the decimal point, while the centre one can be used for other purposes, for example the entry of two zeros, or can be left without any operative function.

The 12 contact blades 19 for the keys 11 of the numeral section 40 are formed in a single rectangular sheet 42. These blades 19 are arranged in two groups of six blades disposed side by side on two sides of the sheet 42. The two groups of blades 19 are separated by a central zone 43 which is more rigid than the zones of the blades 19.

The zone 43 is provided with a series of holes 44 which serve to receive screws 21 passing through corresponding holes in the cover plate 12 and which are screwed into a rigid transverse bar or plate 20 clamping the blades 19.

The six blades 19 of each group of the section 40 are actuated by two adjacent rows of three projections 33 indicated by dash lines in FIG. 1. The total width of the six blades 19 is about equal to the width of each row of projections 33. The arrangement of the blades 19 with respect to the projections 33 is such that only the projections 33 of the outer rows have directly thereunder the regions of the blades 19 adapted to be actuated directly by the shank 28 guided vertically as in the above-described key.

In the spaces present between adjacent projections 33 there are located another three blades 19 which are actuated by the projections 133 (FIG. 3) belonging to the inner rows of the section 40. Since these projections 133 are arranged in columns with the projections 33 of the outer rows, they are shifted with respect to the corresponding blades 19. The actuation of these blades 19 therefore cannot take place directly by means of the shank 28. To this end, the cover plate 12 has within the area of the numeral key section 40 six like openings 45 only one of which can be seen in FIG. 1. The openings 45 are substantially L-shaped and are in two parallel rows of three and inclined at the same angle as the line joining the centre of pressure 47 on the plate 19 with the centre 48 of the projection 133. The two centres in question are made to correspond to the two outer corners of the larger side of the "L" of the opening 45.

Inside each of the shaped openings 45 there is housed a plate 49 of the same plastics material of which the plate 12 is formed and having substantially the same form and size as the corresponding opening 45. The plate 49 carries integral therewith, within the respective projection 133, aa flange 131 (FIG. 3) similar to the flange 31. Moreover, in thee lower part of the corner 47 (FIG. 1), the plate 49 bears integral therewith a shank 128 adapted to press the blade 19 through a guide hole 29 in line with the other five holes having the same function. The plate 49, moreover, bears integral therewith and transversely of the end of the smaller side of the "L" a pin 50 which is inserted in a suitable groove 51' formed in a corresponding position in the plate 12 to allow the pivoting of the plate 49. The pin 50 has a longitudinal shape such as to be capable of being inserted in the groove only by holding the plate 49 in a vertical position. This prevents the said plate becoming disengaged from its seat during actuation.

When a pressure is exerted on one of the projections 133 of the inner rows of the matrix of keys 11, the flange 131 is shifted, therefore causing a slight pivoting of the plate 49 about the axis of the pin 50. This pivoting is sufficient to produce the necessary displacement of the shank or stem 128 for changing over the position of the blade 19 from its inoperative position to the contact position. The operative functioning of this type of key is therefore like that described above.

The function keys section 41 comprises a first row at the top composed of three circular projections 141 and a second row composed of another two projections 141 arranged in columns with the of the first three. The section 41, moreover, comprises another three rectangular projections with rounded ends arranged in columns with the projections of the upper rows, one of which projections 151 (FIG. 4) is of larger dimensions, while the other two projections 152 are of smaller dimensions. Thee circular projections 141 control the blades 19 in the manner seen in the case of the numeral section 40, i.e. directly through the shanks 28 (FIG. 3) for the first row and indirectly through the transmission plates 49 for the second. The remaining three rectangular keys comprise, for the actuation of the respective plates 19, plates 51 and 52 similar to the transmission plates 49. The plates 51 and 52 have the object of ensuring the actuation of the plate 19 whatever the point of the projection 33 on which a pressure is exerted. The plates 51 and 52 are inserted in corresponding openings 53 and 54 of the cover plate 12. These plates have a rectangular form similar to the form of the corresponding projections 151 and 152. Moreover, each plate 51 and 52 bears integral therewith a lateral extension 56 shaped so as to support an integral pin 55 (FIG. 4) parallel to the longitudinal larger side of the plates 51, 52. Each of the plates 51 and 52 moreover bears integral therewith, in a central position at the bottom thereof, a shank 129 which acts on the respective blade 19.

By pressing any point whatsoever of a projection 151, 152 of elongated form, a pivoting action about the pin 55 is imparted to the plates 51, 52. In this way, thee shank 129 exerts the due change-over pressure on the blade 19. The blades 19 of the key section 41 are formed from another sheet 142 fixed to the plate 12 in a similar manner to the sheet 42.

To each of the two meatl sheets 42, 142 there leads a connecting conductor 57, 58, respectively, which constitutes the common reference conductor for the contacts of each of the two sections.

Referring to FIG. 5 there is seen a metallic tongue 19, anchored in support members 12 and 20, and disposed below a key 31. Situated below tongue 19 is a circuit board 15, see also FIG. 6, having conductive emplacements 205 and 206. The circuit board can be constructed of alumina and the conductive regions may be of gold which is deposited on the board by conventional vacuum or thick film techniques. Curved projections 207 and 208 make contact with emplacements 205 and 206 when key 31 is depressed; since power emplacement 206 is connected to a voltage source V, the depression of key 31 causes current to pass through projection 208 to signal emplacement 205 through projection 207. This current is then conducted through metallization path 209 to integrated circuit chip 230. Circuit chip 230, which is of conventional construction, contains appropriate calculator logic and is connected to signal emplacements 205, 210-214; power emplacements 206 and 215-219 are all connected to a source of voltage V. It will be noted that chip 230 is mounted directly on the circuit board, no separate package is required. (Of course, a cap will be placed over the chip to hermetically seal it.) While only six sets of signal and power emplacements are shown, in actually, the circuit board will carry as many sets as needed for the desired parameters of the calculator; there will be a set for each number 0-9 and a set for each desired function (add, subtract, multiply etc.) as well as sets for decimal point and algebric sign.

Conductive paths 209 and 220 and power bus 221 are depicted in an extremely elementary fashion; in fact, the metallization artwork is more complex in that various paths cross over other paths (for example, power bus 221 would cross over paths 209 and 220 in order to connect with the bus on the opposite half of the circuit board). This is accomplished using well known deposition techniques: first a metallization pattern is deposited with gaps left where one path is to cross another; second, insulation pads are deposited over those points on the metallization pattern where cross overs are to occur; finally, conductive strips are deposited over the insulation pads completing the cross-over path.

There is an alternative construction which would partake in the advantages of the above described device; instead of voltage source V being connected to the power emplacements 206 and 215-219, the voltage source could be connected directly to each tongue 19 at point 22. The power bus, power emplacements and projection 208 could therefore be eliminated; when key 31 is depressed, current would pass from point 22 through tongue 19 to signal emplacement 205 and finally to integrated circuit 230.

This invention is not concerned with the particular integrated circuits used. Any well known integrated circuit logic techniques can be utilized in the design of the integrated circuit (for example, the matrix coding technique could be used).

By using the above described keyboard to make contact with a circuit board which has integrated logic mounted thereon, one obtains a particularly thin, low cost, and dependable calculator.

It is understood that various modifications may be made in the key and the keyboard described. For example, the shank 28 may be integral with or fixed to the projection 33.

Furthermore, the flange 31 (FIG. 2) can have integral on the edge of its lower part, an elastic projection parallel to the shank 28, which terminates with a projection tooth to form a latch. This latch can engage a corresponding notch of the cover plate 12, so as to prevent the shank 28 from accidentally going out from the relevant guiding hole 29.

Furthermore, the tongue 23 of each blade 19 rather than being integral with each blade 19, can be made of a different material and be secured to the portion 122 to carry out its positioning action. This action can be additionally facilitated by providing a U-shaped rigid plate, so as to compel the free end 22 of the plates 19 to maintain in the upper position shown in FIG. 2.

Finally, to prevent that the depression, voluntary effected on one of the keys of the external rows of sections 40, 41 to operate the corresponding plates 19, could be transmitted to the adjacent plates 19 by the rotation of the relevant plates 49, an additional plate located between the plate 12 and the deformable layer 10 may be used. This additional plate may be so shaped as to be crossed only by the shank 28 of the keys and should therefore cover the plates 49, thus preventing the simultaneous operation of more than one key.

Claims

What we claim is:

1. An electric keyboard having a plurality of depressible projecting keys, at least one movable electric contact for each of said keys and operable to close a circuit by bearing on a fixed contact, said movable contacts being together connected to form a comb collector, and a plurality of shanks connected to a corresponding of each one said keys for operating said movable contact, wherein:

each of said movable contacts comprises an extended thin flexible blade attached at one end to a stationary guide plate and the other end having shaped thereon a contact surface for contacting said fixed contact and being free for movement between an inoperative position and said fixed contact, said blade fixing one extremity of an actuating tongue projecting between the two ends of said blade, the other extremity of said tongue bearing on a fixed stop located above the line joining the attached end and said fixed contact, and said tongue being bent in arcuate form for pulling upwardly said contact surface, said shank pressing said flexible blade at a point located between said point of attachment and said fixed stop in order to cause said one extremity of said tongue to pass over the line joining said attached end and said fixed stop so that said contact surface is snap pulled downwardly for bearing said fixed contact, said flexible blade snapping back in the inoperative position when said depressed key is released.

2. Keyboard as in claim 1, wherein each of said shank is constantly urged upwardly by said blade in a corresponding rectilinear guide formed in said guide plate, said shank having on its upper part an integral flange protruding from said plate and further comprising

a layer of deformable material covering said guide plate and shaped in such manner as to form said projection key over each of said flanges so as to seal hermetically said plate and to define a cavity between said projection and said guide plate in which said flange is moved.

3. Keyboard as in claim 1, wherein said tongue has said one extremity fixed to said other end and extends said other extremity towards said attached end said tongue being centered between two laterals straight rails of said blade, said other end forming said contact surface by an arcuate bent which assumes a S-shaped profile with said tongue.

4. An electric keyboard comprising:

a plurality of keys obtained by projections of a layer of deformable material;

a guide plate supporting said layer as to be sealed hermetically by the layer and defining a cavity for each projection;

at least one movable electric contact for each of said keys, said movable contact including a thin flexible blade attached at one end to said guide plate and having the opposite end shaped as to form a contact surface for contacting a corresponding fixed contact;

said blade, in correspondence of said contact surface, having a portion extending toward said attached end, said portion being bent in arcuate form and having one extremity bearing on a fixed stop of said plate; and

a shank for each of said projections movable on said plate, each shank protruding in each cavity and having an integral flange normally spaced from the projection in the cavity, said shank having an extremity cooperating with said flexible blade at a point located between the said point of attachment and the said fixed stop as to cause, when depressed, said arcuate portion to produce snap contact between said contact surface and said fixed contact after the flexible blade has reached a predetermined position, the flexible blade snapping back said shank into the inoperative position when the projection is released.

5. In a keyboard for electronic calculating machine in which the external layout of set of keys forms at least one matrix of rows and columns of keys, wherein said key is obtained by a projection of a layer of deformable material, the combination including:

a comb collector of movable contacts comprising for each projection one corresponding extended thin flexible blades, said blades being parallel each other and with respect to the columns of said matrix of projection, said blades having a free contact end and a common opposite integral end, said integral end being fixed, a portion of said blade being bent in arcuate form and bearing on a fixed stop as to cause said free contact end to move between a stable inoperative position and an instable contact position to touch a corresponding conductive contact area with a snap action when a pressure is exerted on said blade at a pressure area located between said opposite integral end and said fixed stop, said blade snapping back in said stable position when said pressure is ceased, said pressure area, in a first group of said blades, corresponding to projections of a first of said rows, being aligned with the column of projections of said first rows and, in a second group of said blades, corresponding to projections of a second of said rows, being misaligned with the column of the projections of said second rows,

a stationary guide plate at which said integral end of said blade is fixed, said guide plate having openings in correspondence to each of said pressure areas, said openings for said first group of said blades comprise corresponding rectilinear guide holes perpendicular to said flexible blades and for said second group of said blades said openings comprise a shaped slits joining the projections of said second rows with the corresponding pressure areas,

a shank for each of said projections for operating said blades on said pressure areas, said shank of said first group of said blades being a pin housed in each of said rectilinear guide holes and located below said corresponding projection of said first rows, said shank for said second group of blades being a member pivotable in said plate, said member having a first part bearing on said pressure area and a second part cooperating with the projection of said second rows, said member being housed in said shaped slit for transmitting the finger pressure from said projection to said pressure area, said pins and members being constantly urged upwardly by said blades and said layer covering said guide plate so as to seal hermetically said openings.

6. Keyboard as in claim 5, wherein said portion of said blade is a tongue having one extremity fixed at said free end contact, projecting between the two ends and centered between two lateral straight rails of said blades, the other extremity of said tongue bearing on corresponding fixed stops integral with said guide plate, and said guide plate having furthermore windows housing said tongues.

7. Keyboard as in claim 5, wherein said comb collector has two opposite rows of blades connected together by a common central part.

8. Keyboard as in claim 7, wherein said comb collector is electrically energized by an additional common blade integral and parallel to said blades constantly contacting with a common conductive area.

9. Keyboard as in claim 5, wherein each of said pivotable member has said integral cylindrical member and flange shifted in the same side with respect to said axis of rotation.

10. In a digital calculating machine, designed for use as a hand held machine, the combination including:

at least one unpackaged integrated circuit comprising a chip having electronic circuits for performing arithmetic functions;

one piece conductive terminals directly connected to said electronic circuits;

a protective cap;

an insulative substrate fixing said chip and having a portion prepared for placing said protective cap over said chip;

a source of voltage;

a keyboard including flexible, electrically conductive, contact tongues which are disposed above said substrate and which have at least a single contact projection, said tongues being responsive to the activation of keys by bending toward said substrate;

means for connecting said tongues to said source of voltage; and

a first electrically conductive interconnection pattern, said first pattern being deposited on said substrate being directly connected to said conductive terminals and extending from said chip to contact portions of said pattern which are directly below said contact projections, the depression of a key causing a contact projection to bend until making contact with the corresponding one of said contact portions causing an electrically conductive path to be completed between said source of voltage and the circuit of said electronic circuits connected to said corresponding one of said contact portions.

11. The combination according to claim 10 wherein said connecting means include a second pattern also deposited on said substrate and a second contact projection included in said conductive tongues, said second contact projection of said tongues being positioned over said second pattern, the depression of a key causing said second projection to contact said second pattern so that electrical current is conducted from said second pattern, through said second projection, aid contact tongue, said first projection and said first pattern to said chip.