US3739454A - Push-button key assembly - Google Patents

Abstract

Push-button key structure, for use in adjustable radio tuning apparatus. The parts of the key structure are constructed and arranged to enable mechanized assembly of the push-button keys. Each key assembly comprises a pair of elongate slide members one of which carries an adjustable and lockable cam engageable with a treadle bar the angular position of which determines the tuning of associated radio apparatus. The keys are so designed that they may be completely assembled by interlocking engagement of the component parts thereof, using automatic machinery capable of only rectilinear movements. Provision is made for forcible ''''sizing'''' of parts of the key to maintain them in proper position and establish the tolerances required to insure proper operation of the cam.

Description

United States Patent 1 [111 3,739,454 Thompson June 19, 1973 PUSH-BUTTON-KEY ASSEMBLY [75] Inventor: Alvin E. Thompson, North Wales, Pmflary Exam" ler charles Lanham Pa Assistant ExammerE. M. Combs Attorney-Carl H. Synnestvedt [73] Assignee: Philco-Ford Corporation,

Philadelphia, Pa. ABSTRACT [22] Filed: 1971 Push-button key structure, for use in adjustable radio [21] Appl. No.: 210,506 tuning apparatus. The parts of the key structure are constructed and arranged to enable mechanized assem- Related Apphcatlon Data bly of the push-button keys. Each key assembly com- [62] n of 81,897? 1970 prises a pair of elongate slide members one of which 1680394 carries'an adjustable and lockable cam engageable with a treadle bar the angular position of which determines [52] US. Cl. 29/407, 29/445 the tuning of associated radio apparatus The keys are Cl so ig d y b pl y assembled [58] Field of Search 29/243.5, 407, 445, interlocking engagement of the Component parts 72/316 74/1033 thereof, using automatic machinery capable of only rectilinear movements. Provision is made for forcible [56] References cued sizing of parts of the key to maintain them in proper UNITED STATES PATENTS position and establish the tolerances required to insure 3,086,401 4/1963 Horton 74/1033 proper operation of the cam. 3,195,359 7/1965 Clark 74/1033 3,357,265 12/1967 Thompson 74/1033 3 Chums, 6 Drawmg Flgures A r. 1! l 2/ 7 J0 PUSH-BUTTON KEY ASSEMBLY This application is a division of application Ser. No. 81,897, filed Oct. I9, 1970, now US. Pat. No. 3,680,394, and the invention hereof. I

BACKGROUND OF THE INVENTION This invention is particularly useful in push-button operated radio equipment, for example radios adapted for use in automobiles. In tuners for such radios it is common to utilize push-button keys each of which comprises a main slide member carrying a pivotable cam lockable thereto, and a finger-operated extension slide member which is movable relative to the main slide member. In such known apparatus when the extension slide member is drawn outwardly toward the operator, moving relative to the main slide member, the cam carried by the latter is free to pivot to a new station-selecting position in response to manual adjustment of the frequency-determining device. Thus, setting of a push-button key is effected by withdrawing the extension slide member to free the cam, tuning the set to the desired station, and subsequent inward movement of the extension slide member, with respect to the main slide member, which brings the cam into engagement with the treadle bar and locks it in position. Thereafter depression of that key tunes the receiver to the selected station. Since locking of the cam is brought about by inward sliding movement of the extension slide member, such apparatus has frequently been designated as being of the push-to-lock type.

Push-button keys of this known kind have proven difficult to manufacture, and the large amount of handwork which has hitherto been required, during assembly of the component parts which comprise the key, has substantially increased the cost of the apparatus. When attempts were made to mechanize the assembly process, problems were encountered because of the complex, frequently twisting, motions which had to be applied to the parts to bring the same to interlocking position. Problems have also arisen from the fact that it has been difficult to manufacture the key assemblies with such precision that the clamping pressure applied to the cam is sufficient to insure consistent and reliable operation of the cam in driving the key bar, and yet is so controlled that the cam is reliably unclamped when the finger-operated extension slide is returned to its withdrawn position with respect to the main slide member.

SUMMARY AND OBJECTIVES OF THE INVENTION It is the general objective of my invention virtually to eliminate the need for twisting motions, and consequent handwork, in assembling such keys, and to reduce manufacturing costs, by providing key parts which are so constructed as to enable automatic assembly by relatively simple machines capable of only rectilinear motions. To this end I provide a main slide mem her having an aperture through which a T-bar or lug, struck from the metal of the extension slide member, can be inserted and in which apparatus only rectilinear movement is required for insertion and for relative movement of the slide members, to a position in which theyinterlock. My apparatus is featured by the use of a small lateral projection which is deformable after assembly, being movable a distance sufficient to prevent the T-bar from fully confronting the mentioned aperture. The T-bar, in cooperation with this projection, holds the slide members in assembled relation. Deformation and locking of the projection is readily accomplished by a simple rectilinear motion.

It is a particular objective of this invention to provide a novel method for sizing parts of the assembled key,

in a manner which does not rely on sensing the stacked thicknesses of various parts, as has been done in the past. Obviously variations in thickness can interfere with proper sizing.

Another feature which facilitates machine assembly of the keys involves a novel shape and function of the leaf spring which preloads the usual cam clamping lever toward the non-clamping condition.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 4 is a fragmentary sectional view similar to FIG.

3, and illustrating the extension slidie member in its forward position in which the cam is locked in position on the main slide member;

FIG. 5 is a view similar to FIGS. 1 and 2, and illustrating, on a larger scale, upper and lower fixtures which are used to size the assembly and insure proper release and clamping of the cam; and

FIG. 6 is a fragmentary perspective illustration of a portion of the upper sizing fixture.

DESCRIPTION OF THE PREFERRED EMBODIMENT First with general reference to the drawing, there is illustrated a push-button or key assembly which comprises a main slide member 10 and a finger-operated extension slide member 11, said slide members being relatively extensible to permit adjustments, and also being slidable as a unit to effect a tuning operation. A cam 12 is carried by the main slide member 10, being mounted on the latter through the agency of a cylindrical projection 13 which, conveniently, is raised from the metal of the main slide member 10 and provides a journal about which the cam 12 may pivot. As is well known in this art, depression of the key assembly as a unit, by pressure exerted against the finger button shown at 14 in FIG. 1., effects tuning of the receiver by positioning a pair of rods I5-15 which are coupled to form a treadle bar assembly, in accordance with known practice. The treadle bar is associated with frequency determining means which need not be illustrated herein. Setting of the push-button is brought about by withdrawing the extension slide member I], with respect to the main slide member 10, as is explained below.

The mechanism is designed to permit placement of the'parts of the key assembly on a holding fixture and subsequent assembly of the parts by machinery (not shown) which need be capable of only lateral and vertical motions. With the main slide member 10 held on a suitableflxtui'e, for example the lower fixture shown fragmentarily at 16 in FIG. 5, a bar or lug 17 which extends laterally from the body of the extension slide member 11, is fitted through a loading notch 18 formed in the main slide and which is ofa size to receive the lug 17, including its laterally extending T-shaped projections 19. This arrangement is clear from FIG. 2, which shows the assembly of FIG. 1 from the underside. By moving the extension slide member 11 rectilinearly along and toward the right-hand end of the main slide member 10, as the latter is viewed in the drawings, the T-bar or lug 17, 19 moves into a position in which it occupies a narrower restraining portion 18a of loading notch 18. In this position, which is illustrated in FIG. 2, the two slide members are held in assembled relation. A pair of flange projections 2020, formed as parts of extension slide member 11, cooperate with edge portions 21 of the main slide member 10, to prevent lateral cocking movements of one slide member with respect to the other.

The apparatus is featured by the use ofa small lateral projection 22 which is readily deformable after assembly of the slide members to a position (shown in dotted lines at 22a in FIG. 1, and in full lines in FIG. 2), in which position it is in interference relation with one of the projections 20 when the extension slide member is withdrawn to the left with respect to the main slide member 10. When the projection 22 has been deformed, which may readily be accomplished by the use of automatic machinery, it limits withdrawal movement of the extension slide member 11 to a distance such that the T-bar extensions 19 do not fully confront the loading notch 18 (FIG. 2). In summary as to this feature, the T-bar, in cooperation with projections 20 and 22, holds the slide members in assembled relation without the need for studs or rivets.

As is common in this art, and as has been briefly mentioned above, cam 12 is freed for pivotal movement to a new station-selecting position by withdrawing the extension slide member to the left, with respect to the main slide member 10, to a position in which the cam is unclamped. While such clamping and unclamping movements of the cam are not broadly new, the apparatus which effects the same will now be described briefly, in order that certain new features thereof may be understood.

A cam clamping lever of generally known type, is shown at 23. The right-hand end of this lever is provided with bifurcations 24-24 which fit beneath and bear against T-shaped extensions 25 formed as a part of a T-bar or lug 26 (see particularly FIGS. l-3) which extends from the main slide member 10. The construction and relative arrangement of the extensions 25 and clamping lever 23, and the way in which these parts are sized to provide proper operation of the cam, is explained later in this description.

The left-hand end of clamping lever 23 is provided with a curved portion which is shaped to cooperate with an inclined cam surface 27 formed as a part of the first mentioned T-lug 17. As will be clear from a comparison of FIGS. 3 and 4, when the extension slide 11 is in the withdrawn position (FIG. 3), cam surface 27 is disengaged from the curved end surface of locking lever 23, with result that the lever pivots downwardly, to the position shown in FIG. 3, under the urging of a generally flat leaf spring S one end of which makes contact with the underside of the right-hand end of the clamping lever 23, and the opposite end of which reacts against a locating stud 28, formed as a part of main slide member 10, and against a rivet 29 which stakes the spring to the main slide lever. For the sake of clarity in illustrating other parts, the left end of spring S is shown broken away in FIGS. 3 and 5.

When the clamping lever occupies the position shown in FIG. 3, its cam contacting projections 30 are withdrawn from the upper surface of the pivotable cam 12, leaving the latter free to rotate upon its journal 13. In accordance with usual practice, manual tuning of an associated receiver to a desired station, and subsequent reclamping of the cam 12, conditions the receiver to receive the selected station in response to subsequent actuations of that key. It should be appreciated that the spring S not only serves to preload the cam clamping lever 23 toward the non-clamping position, but also is effective to retain the cam 12 properly assembled with respect to the journal projection 13 since it prevents any substantial movement of the cam away from the supporting surface of main slide member 10.

It is important to note that assembly of the cam over the projection 13, and mounting of the spring S in position beneath the bifurcated ends 24 of lever 23, which ends underlie extensions 25 of T-bar 26; may all be brought about without the complex and frequently twisting motions which had to be applied to the lever, spring, and cam parts of the kind used heretofore. In prior constructions the spring body frequently was apertured intermediate its ends to accommodate the T- projections which cooperate with the lever in clamping the cam. This earlier type of construction required that the spring be turned with respect to the T-bar and twisted back to proper longitudinal position, after which the rearward part of the spring was snap-engaged with a cam-holding stud. These motions cannot readily be carried out by automatic machinery.

The cam is reclamped, during adjustment thereof, by moving the extension slide member 11 toward the right with respect to the main slide member 10 into position in which its cam surface 27 forces the left-hand end portion of the locking lever upwardly to the position shown in FIG. 4. In this elevated position, in which the locking lever is flexed very slightly, the studs 30 which are carried by the bifurcated ends 24 of the locking lever bear forceably against the upper surface of cam 12, forcing it against member 10 and preventing any pivoting movement of the cam with respect to the main slide member.

The manner in which the parts are configured to insure proper clamping pressure and the method of sizing certain parts in the achievement of consistent and reliable operation of the cam will now be described. First making reference to FIGS. 1 and 3, it will be observed that the bifurcations which form the right-hand end of the clamping lever 23 are depressed or coined" in a manner to provide shallow indentations 31 extending across each of the bifurcations 24. These indentations underlie the cross-head which forms the lateral projections 25 of the T-bar 26. The right-hand portion of each indentation 31, when viewed in elevation (FIG. 5), is recessed to a lesser degree than the left-hand portion. This results in inclining the surface of each indentation upwardly toward the cam-clamping end of lever 23. In accordance with my invention knife-edge interengagement between the lever and the T-projections 25 is insured by the mentioned inclination of the coined or indented area and by so shaping the lug 26 that the lower edge which lies most closely adjacent to the clamping end of lever 23 is oppositely inclined. The result is knife-edge contact of the projections 25 along the line shown at 32 where the projections bear against the up wardly inclined surface 31 of lever 23. This feature insures that the actual contact between the lever and the T-projections 25 occurs in a predetermined region which maximizes the force developed by the clamping moment arm measured from the knife edge to the center of the clamping projections 30.

Particularly characteristic of my invention is the way in which the T-bar 25-26 is sized downwardly to a position in which the parts are retained in proper relation and the tolerances are established which are required to insure proper operation of the cam. In accordance with this concept, a small aperture 33 (see FIGS. 3 and 5) is provided in the main slide member beneath the cam 12 and through which aperture may extend a reciprocable plunger associated with fixturing apparatus used during the sizing. A lower fixture part, for example part 16 to which reference has already been made, is used to support the key assembly, while an upper horizontally and vertically translatable fixture element, shown fragmentarily at 34, carries a ram 35 adapted to contact and move the T-lug 26. When the parts are ready for sizing, the switch operating plunger 36 is spring-urged upwardly against the lower surface of cam 12. This holds the cam in the elevated position shown in phantom lines in FIG. 5, since the extension slide member 11 has been withdrawn from beneath the left end of locking lever 23.

The illustrated fixturing apparatus is utilized in the practice of my new method of sizing the key assembly, which method produces assemblies which are more uniform in clamping pressure. In previous push-to-lock mechanisms there was a tolerance build-up due to the thicknesses of the cam, lever and slide parts, and resultant differences in the amount of deformation which occurred in the clamping lever when it was forced into its upper clamping position. In serial production of the keys, these difficulties resulted in undesirable variations in clamping pressure and consequent interference with subsequent reliable operation of the cam. All of these variables are compensated for by accomplishing sizing by bending the main T-projection 26 rearward (toward the right) and downward, until a desired predictable tolerance is established, as sensed by displacement of the plunger 36 which operates a switch device (not shown) adapted to control the supply of power to upper fixture 34 and ram 35. In this way precise sizing is accomplished which does not rely upon sensing the stacked thicknesses of the various parts.

When the apparatus is ready for sizing, the lug or projection 26 extends generally vertically, as is shown in broken lines at 26a in FIG. 5. As a first step in the sizing process relative translational movement between the lower fixture portion 16 and the upper fixture element 34 is effected, most conveniently by translating the upper element 34 in the direction indicated by the arrow A. An angled surface 35a of ram 35 (FIG. 6) makes contact with upper portion of the T-slug 26 forcing it to the right, a distance equal to about 0.020 inch measured from the original vertical position. This motion angles the T-lug to produce the above-mentioned knife-edge contact at 32 and a desired predictable clamping moment arm. The ram 35 is then translated downwardly, as shown by the arrow B, bending or deforming the T-lug 26 to a predetermined degree as sensed by a switch associated with the plunger 36. De sirably, the ram 35 should be capable of about 0.030 inch vertical displacement. Using key parts of the gen eral dimensions which have become accepted in the industry, the ram was translated downwardly about 0.016 to 0.019 inch, that is until it occupies the position shown in full lines in FIG. 5.

The cam, spring and slide parts are so dimensioned that, prior to the sizing operation, the plunger 36 holds the cam elevated above the surface of main slide 10 a distance equal to about 0.020 inch. Satisfactory and reliable clamping pressure can be insured by forcing the cam 12 downwardly to the position shown in full lines, that is, until it is spaced above the slide member 10 a distance between about 0.001 and 0.006 inch. When the plunger 36 senses that suclh position has been reached it cuts off power to the ram, with the result that the vertical distance between the knife edge 32 and the cam-contacting surface of main slide 10 can be held constant through series assembly of many push-button keys. This insures that, when the extension slide memeber 11 is moved to the right, and the cam clamp ing lever 23 is forced upwardly, the distance moved by the cam clamping projections 30 is constant and a relatively uniform locking force is applied in each cam assembly manufactured.

I claim:

1. In the manufacture of a push-button key assembly of the kind including relatively slidable, overlapping, main and auxiliary slide members, a cam element pivotally mounted on one of said slide members, a lever responsive to relative movement of said slide members to move to a position in which it clamps said cam against pivotal movement, and a T-lug upstanding from said one slide member, said T-lug having a cross-head with an undersurface against which said lever bears in clamping said cam,

the method of sizing said key assembly to insure proper clamping pressure between said lever and said cam, said method comprising:

moving said T-lug in the direction of the length of said one slide member to tilt said lug and provide line contact between an edge of the undersurface of said cross-head and said lever,

and also moving said T-lug downwardly toward the surface of the mentioned slide member to a position in which there is established a predetermined distance between that edge of said cross-head which is in line contact with said lever and the surface of the mentioned slide member.

2. A method in accordance with claim 1, and further characterized in that said predetermined distance is es tablished by effecting at least a portion of said downward movement of said T-lug after completion of said movement in the direction of the length of said one slide member.

3. A method in accordance with claim I, and further characterized by the steps of:

biasing said cam in an upward direction, away from said surface and into contact with said lever; utilizing said downward movement of said T-lug to force said lever and hence said cam downwardly toward said surface; and establishing said predetermined distance by sensing the distance between said cam and said surface, and terminating said downward movement when the latter distance reaches a predetermined value.

Claims (3)

1. In the manufacture of a push-button key assembly of the kind including relatively slidable, overlapping, main and auxiliary slide members, a cam element pivotally mounted on one of said slide members, a lever responsive to relative movement of said slide members to move to a position in which it clamps said cam against pivotal movement, and a T-lug upstanding from said one slide member, said T-lug having a cross-head with an undersurface against which said lever bears in clamping said cam, the method of sizing said key assembly to insure proper clamping pressure between said lever and said cam, said method comprising: moving said T-lug in the direction of the length of said one slide member to tilt said lug and provide line contact between an edge of the undersurface of said cross-head and said lever, and also moving said T-lug downwardly toward the surface of the mentioned slide member to a position in which there is established a predetermined distance between that edge of said cross-head which is in line contact with said lever and the surface of the mentioned slide member.

2. A method in accordance with claim 1, and further characterized in that said predetermined distance is established by effecting at least a portion of said downward movement of said T-lug after completion of said movement in the direction of the length of said one slide member.

3. A method in accordance with claim 1, and further characterized by the steps of: biasing said cam in an upward direction, away from said surface and into contact with said lever; utilizing said downward movement of said T-lug to force said lever and hence said cam downwardly toward said surface; and establishing said predetermined distance by sensing the distance between said cam and said surface, and terminating said downward movement when the latter distance reaches a predetermined value.

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