US3378652A - Keyboard switch assembly with improved contact means - Google Patents

Description

April 16, 1968 c. A. DYLE 3,378,652

KEYBOARD SWITCH ASSEMBLY WITH IMPROVED CONTACT MEANS Filed June 20, 1966 f ih, L I "U|P TX 24 16 i 14 z; 15 "LIL H/ lnl 5/ 1 000000000000000 /5 y 75 oooooooo ooo'oo objg oooooooooooooo OOOOOOOQ/O/O/O fio f0 United States Patent 3,378,652 KEYBOARD SWITCH ASSEMBLY WITH IMPROVED CONTACT MEANS Charles A. Dyle, Chicago, 111., assignor to Hammond Corporation, a corporation of Delaware Filed June 20, 1966, Ser. No. 558,714 9 Claims. (Cl. 200-) ABSTRACT OF THE DISCLOSURE A playing key actuated switch assembly for organs in which playing any key brings a multiplicity of switch blades for that key into contact individually with a multiplicity of bus bars which are common to a group of the switch assemblies. One switch assembly is provided for each playing key. In each assembly the switch blades are parallel and self-spring biased against their bus bars and normally are held out of engagement therewith by a slide which engages the blades and is spring biased in the opposite direction by a force greater than the sum of the spring forces provided by all of the blades in the switch assembly. The switch assemblies are on cards which are mounted in aligned parallel relation in a row, one under each playing key, and the bus bars are wires which pass through aligned loose fitting holes in the row of cards.

The present invention may be considered as an improvement over the switch assemblies shown in Hammond Patent No. 1,956,350, FIGS. 3 and 13 to 17. Electrical organs, particularly of the type which synthesize complex tones from a group of signals supplying individually the fundamentals and various harmonics as desired, require a large number of key actuated contacts which cooperate individually with a number of bus bars. Additionally, there may be a necessity for other key actuated contacts which perform specific control functions. The switch organization of this invention is intended for such use and is particularly advantageous where the number of contacts needed is greater than has previously been believed to be practical. As an example, the particular embodiment shown has a capacity of twenty contacts or so, and more could be provided if necessary.

In general, an organ of the present invention uses a plurality of new and improved switch assemblies corresponding individually to each key of the manual. Specifically, each switch assembly includes a molded plastic switchboard having a molded plastic actuator mounted for movement thereon, and cooperating contacts located in proximity to bus bars passing through the switchboard.

It is therefore an object of the present invention to provide an electrical or electronic musical instrument of the keyboard type with a novel and improved keyboard switch assembly.

Another object is to provide a novel switch assembly which requires low actuating effort considering the number of individual contacts in the assembly.

It is a further object of the present invention to provide an electrical or electronic musical instrument with a compact, low cost keyboard switch assembly.

Other objects and advantages will become apparent from the following description taken in conjunction with the accompanying drawings wherein:

FIG. 1 is a side elevational view of a switch assembly of the invention;

FIG, 2 is an end elevational view of the switch assembly;

FIG. 3 is a view of the side opposite FIG. 1; and

FIG. 4 is an enlarged view of one of the switch contact blades.

Referring to the drawings, the switch assembly proper 3,378,652 Patented Apr. 16, 1968 10 is mounted on edge so that one of these assemblies lies beneath each of the organ playing keys 12. As shown, the playing key is hinged at its rearward end by a flexible spring strip 13. When a key is pressed, an intermediate portion thereof presses downwardly and upon the rounded nose 14 at the end of a lever 16 which is a portion of the contact actuating mechanism. This lever 16 and the contact organization associated therewith is attached to a switch card or board LS and is separately assembled so that each set of contacts, one for each playing key, can be put into place in organ already assembled, tested, and partially wired.

The switch board 18 is molded of suitable plastic material. It is generally rectangular with its edge profiled, as at 20 for instance, so as to enable it to be aligned and secured in place in the organ during final assembly. Just what arrangement is used to accomplish this is largely a matter of choice and needs no special description here.

Near the top and toward the right edge as seen in FIG. 1, the card has a horizontal guide slot 22 formed therethrongh, and a similar, but shorter, slot 24 is formed near the left hand edge. A contact actuator bar 26 has a flat tab 28 and guides the right end (FIG. 1) of the actuator for horizontal sliding movement. At its opposite end, the actuator is pivoted to a rivet 30 which extends through the slot 24 and through a lever 32 which lies against the opposite face of the card. This lever 32, molded of plastic material, has a downwardly extending portion 34, the end of which has a cylindrical peg 36 which extends through a hole in the board.

The pivot points at 36 and 30 fix the vertical position of the left end of the actuator as seen in FIG. 1, but permil; the actuator to shift slightly horizontally, this shifting movement being limited by the size of the rivet 3t) and the length of the slot 24. Since the rivet 30 holds both the lever 32 at one point and the actuator 26 at one point against opposite faces of the card 18, it is not necessary to head the portion of the peg 36 that extends through the card. The upper portion of the lever 16 is extended toward the center of the card, as at 38, and at the end of this extension it is turned upwardly to form the rounded nose 14 previously mentioned. Thus, pressing the key 12 pushes the nose 14 down, and this causes the actuator 26 to be slid toward the right as seen in FIG. 1. When the key is released, the actuator is returned toward the left in FIG. 1, and the lever 16 returned to its free position by a coil spring 40 which is hooked at one end through a hole in the tab 28, the other spring end being hooked through a hole in a tab 42 which projects away from the back surface of the board 18 and is molded integrally therewith.

At about the middle of the card 18 on the front side (the side shown in FIG. 1), three horizontal rows of vertically aligned bosses 44 project away from the surface of the board. These bosses, which are formed during the molding operation, are essentially cylindrical and serve to anchor the fixed ends of a plurality of spring metal contact blades .6. Each of these blades has a rather stiff lower portion 48 which is preformed so that, by slight additional springing of the metal during assembly, the blade will pass to the left of a boss 44 in the top row, to the right of the aligned boss in the middle row, and to the left of a boss in the bottom row. The spring action of the blade is sufficient to insure that it remains in place, although it is, of course, easily removed if this becomes necessary.

The lower end 50 of the blade is welded to a terminal wire 62 which inclines downwardly and is hooked trough one of a group of spaced slots 64 along the lower edge of the card. Circuit elements, such as resistors, may have one lead welded to the blade and the other hooked 3 through the slot 64 in place of the wire lead at 62 if desired. In either case, it is contemplated that the assembly operation will be promoted if the lead or other circuit element is secured to the blade before the blade is attached to the card.

The upper blade portion 66, the portion above the top boss 44, is slightly narrower than the lower portion so as to make this portin more flexible and to prevent it from rubbing against the card as it is moved from side to side. At its upper end, the blade is forked, as at 68, to straddle a narrow rib 70 provided along the lower edge of the actuator 26, and, at appropriate intervals, the rib 70 is interrupted by teeth 72 which act as abutments to engage the top end of the blade 46 and move it to the left under the influence of the spring 40.

Just below the actuator 26, a contact 74 is secured to the right side of the blade, and in the present instance this contact comprises a short length of small gauge gold wire welded to the blade. So as to promote overall flexibility of the blade while keeping the upper portion relatively stiff, the blade is slotted as at 76 for a suitable distance, beginning at a point just above the top boss 44. Most of the bending, therefore, takes place in this relatively restricted region.

The bus bars 78, one for each contact, Pass horizontally through fitted holes in the board in a direction normal to the plane thereof. These bus bars are so positioned that when the contact blades are sprung to the left by the actuaor 26 and spring 40, the contacts 74 do not touch the bus bars. When the key 12 is pushed down, the actuator 26 moves to the right and frees the contact blades to swing to the right and bring contacts 74 against their bus. bars 78. There is sufiicient lost motion or overtravel of the mechanism that when the actuator 26 moves to the right, it first releases the contact blades enough to permit them to move against the bus bars, and then overtravels sufiiciently to make sure that all of the blades are completely released from restraint, plus a reasonably safety factor.

The geometry of the system is preferably such that when the contact 74 engages its bus 78, the blade from the top boss 44 to the bus 78 is substantially straight. This insures a minimum sliding action of the contact over the bus, and thus there is a minimum possibility of grating transients being produced in the output signal.

Note that in this organization, each of the contact blades is spring loaded with an independent appropriate force toward its circuit closed position, and that the aggregate of all these forces may be quite high when twenty or so contacts are ganged together. However, whatever the t-otal force is, it is more than overcome by the coil spring 40. Thus, the force necessary to actuate the key -12 is only that necessary to overcome the differential existing between the two spring systems. The required playing key pressure, therefore, is much less than would be necessary if the individual switches were spring biased to open position and were simply pushed closed by move-' ment of the playing key.

Note also that when the spring blades move toward or away from contact closed position, the simultaneity of engagement and disengagement can be precisely controlled, since the teeth 72 are close to the bus bars 78, and the short port-ions of the spring blades between the contacts 74 and the teeth are relatively stiff. Differences in the amount of spring bias of the individual blades, therefore, have little effect upon the time of engagement; rather, such differences in bias affect only the contact engaging pressure. This is particularly true, since the contacts engage under their own bias pressure, being free of the teeth 72 at the instant of engagement and during any period of overtravel of the playing key after engagement.

An interesting variation of the basic switch so far described is apparent on the back face thereof (FIG. '3). Here the three vertical rows of bosses or pegs 45 toward 4 the right side :are the counterparts of the bosses 44 on the front face. These bosses 4'5 fix the positions of blades 47 which may be considered as like blades 48, except that the top portions above the row of holes for the bus bars 78 are cut off. Also, instead of a contact 74 being welded to the blade, .a short pin 81, which may be considered as a short piece of bus bar, is welded to the blades 47 so as to extend transversely thereof in a position to pass through the appropriate bus bar hole when the strip 47 is installed. These .pins 81 have a length sufficient to pass outwardly from the front face of the board enough to engage the contacts 74 of the appropriate switch blades 48. Although three vertical rows of bosses 45 have been shown, it will be appreciated that more or less can be supplied, depending upon need.

In any event, each individual strip 47 and contact pin 81, cooperating with its strip 48 and contact 74, acts as an independent single-pole single-throw switch which can be substituted in place of a bus bar type switch whenever this need arises. For example, a bus bar, together with a plurality of cooperating contacts, provides a system for establishing a plurality of circuits in parallel to, for example, a common output, whereas the strips 47 and contact pins 8:1, together with their contacts 74 and blades 48, can be wired into independent circuits which do not need to have one electrical side in common.

From the above description of the invention it will be appreciated that modifications may be made without departing from the scope or spirit thereof, and that therefore the scope of the invention is to be measured from the scope of the following claims.

Having described my invention, what I claim as new and useful and desire to secure by Letters Patent of the United States is:

1. A switch assembly comprising a switch board, a contact actuator mounted upon said board and guided upon said board for limited substantially longitudinal movement relative to said board, a spring member secured between said board and said actuator and biasing said actuator in one direction, said actuator having a plurality of spaced abutments thereon, a plurality of aligned bus bars passing through said board in a direction normal to the plane of said board, a plurality of parallel spaced spring contact blades secured to said board and all spring biased in the same direction to engage individual bus bars when free, said spring contact blades having elements engaging said abutments to move said contact blades away from said bus bars under the influence of movement of said actuator by the first said spring member, and means for moving said actuator in the direction against the first said spring bias to free said spring contact blades from said abutments and permit said spring contact blades to engage said bus bars under the influence of each contact blades own spring bias.

2. In a switch assembly, the combination called for in claim 1, wherein said actuator has an element at one end extending through a slot in said board to guide said one end for linear movement, the other end of said actuator lying on one side of said board and :being connected by a pivot passing through a slot in said board to a lever lying on the other side of said board which lever is pivoted at a spaced point to said board, the line established by said pivots being substantially normal to the direction of movement of said actuator.

3. In a switch assembly, the combination of claim 2 in which means including a playing key is provided for rocking said lever about its pivotal connection to said board.

4. In a switch assembly, the combination of claim 2 in which the sole means securing said actuator and said iever to each other and to said board is the pivot member connecting said lever to said actuator.

5. A switch assembly comprising a switch board, a spring loaded actuator mounted for longitudinal movement on said switch board and having a plurality of abutments formed thereon, a plurality of spring contact blades engaged at one end by said abutments, a plurality of contacts passing through said switch board adapted to engage individual spring contact blades on movement of said spring loaded actuator, said spring loaded actuator and spring contact blades being spring biased in opposite directions with said actuator spring loading overpowering said spring contact blades.

6. The switch assembly called for in claim 5 in which said board is formed on one side to provide a plurality of bosses and said spring contacts are located and secured to said board by spring clamping engagement with said bosses.

7. The switch assembly called for in claim 6 in which at least some of the contacts passing through the board are bus bars adapted to pass through several boards in a row in parallel alignment.

8. The switch assembly called for in claim 6 in which at least some of the contacts passing through the vboard are short pins attached to spring strips, said spring strips being secured by spring clamping action to bosses formed on the side of said board opposite said one side.

9. The switch assembly called for in claim 8 in which at least some of the contacts passing through the board are bus bars adapted to pass through several boards in a row in parallel alignment.

References Cited UNITED STATES PATENTS 3,106,618 10/1963 Campbell et a1 2'005 3,251,923 5/1966 Lund 2OO1 XR ROBERT K. SCHAEFER, Primary Examiner.

I. R. SCOTT, Assistant Examiner.

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