Mechanically Actuated Electric Switch Assembly

Abstract

A highly reliable and readily serviceable electric switch is afforded by a simple and inexpensive magnetic reed switch capsule and a pair of tubular magnets slidably arranged over the capsule. Like magnetic poles on the annular faces adjacent each other hold the magnets apart until they are brought together by mechanical switch actuating means. When brought together by the actuating means, the change in the magnetic field about the reeds actuates the magnetic reed switch contact elements. A minimum of mechanical wear is encountered, and the magnetic reed switch capsules are quickly and conveniently replaceable. A plurality of such magnetic reed capsules may be actuated by a single pair of tubular magnets. All of the reed switch elements may be activated substantially simultaneously or the capsules may be offset with respect to one another for actuating the various reed contact elements sequentially. Push button arrangements are described for keyboard applications.

Description

The invention relates to mechanically actuated electric switch assemblies, and it particularly pertains to such assemblies using magnetic reed switch capsules.

Electric switch arrangements are, of course, quite old. Magnetic reed switches have been used in relays for some time. They are hermetically sealed to provide long life and have favorable bounce characteristics upon closing which make them ideal in operating electronic switching circuits directly. Commercially available magnetic reed switches will handle relatively large currents, enabling them to operate solenoids and other high current devices directly. These commercially available magnetic reed switch capsules are sufficiently identical in production that they are desirable for electrically operated switches in typewriter keyboards and the like.

Examples of magnetic reed switch assemblies and applications are reflected in the following U.S. patents:

3,204,059 8/1965 Saaty 200-87 3,233,061 2/1855 Jones 200-87 3,251,962 5/1966 Jones 200-87 3,260,821 7/1966 Yokoo 200-87 3,283,274 11/1966 De Falco 335-206 3,363,737 1/1968 Wada et al. 197-98 3,449,700 6/1969 Gillilan 335-188 3,457,368 7/1969 Houcke 178-17 3,458,839 7/1969 Heetman 355-152

and in the technical literature:

J. w. berkman, "Toggle Switch," IBM Technical Disclosure Bulletin Vol. 4, No. 11, Apr. 1962, p. 19.

J. w. berkman, "Magnetically Actuated Switch," IBM Technical Disclosure Bulletin Vol. 5, No. 5, Oct. 1962, p. 27.

P. s. bolan, R. W. Keim and C. R. Campbell "Multiconfiguration Pressure Switch" IBM TDB Vol. 8, No. 7 Dec. 1965, p. 954.

L. f. darius and F. O. Underwood, "Toggle and Momentary Reed Console Switch Assembly" IBM TDB Vol. 9, No. 12, May 1967, p. 1702-3.

R. j. redmond, "Pluggable Reed Relay" IBM TDB Vol. 11, No. 3, Aug. 1968, p. 243.

D. e. cuzner and C. N. Walls, "Mechanically Actuated Magnetic Switch" IBM TDB Vol. 11, No. 3, p. 346.

The disclosed arrangements have provided satisfactory electromagnetically operated reed switch assemblies and also some mechanically actuated assemblies as well. However, mechanically operated magnetic keyboard switches have been expensive to manufacture requiring precision control over the mechanical parts and careful selection of the parts and magnets within very close tolerances. Further in the manufacture of mechanically operated magnetic switches of the class described, more and more small parts have been added to the switch assemblies for providing the desired operations. Consequently, a high percentage of mechanical failure rendered these switches inoperable in relatively short service time although the electric components remained unimpaired. An especially difficult problem with all mechanically actuated keyboard switches, is the use of springs for insuring uniform contact pressure and/or release of the actuating mechanism and/or opening the switch contacts. The trend of development is for lighter and lighter touch factors which work against the trend for heavier contact pressures, or at least more uniform contact pressures which are difficult to obtain with light springs. In addition springs are one of the more expensive components making up a mechanically actuated switch assembly.

The objects hereinbefore indirectly referred to and others that will appear as the specification progresses are attained in a switch assembly using a pair of tubular magnets mechanically slidably arranged about one or more magnetic reed switch capsules. The electric lead elements of the magnetic reed capsules may be mounted in almost any conventional manner, such as between a pair of binding posts of non-magnetic material. With such a mounting arrangement, the tubular magnets are simply slipped over the capsule with the opposing faces of the tubular magnets of like polarity. In this manner the two magnets automatically assume the maximum spacing possible within the limitations imposed by the binding posts. In this initial position, the magnets are ineffective to actuate the magnetic reed elements. Simple actuating means, for example simple pins, spring fingers, and the like are used to move one or both of the magnets for bringing them closer together. In the closer position magnetic reed elements are actuated and the switch is closed, opened or transferred in accordance with the contact arrangement within the particular capsule. In the average installation, moving but one magnet is preferred in the interests of simplicity. Where a switch is to be actuated by two separate means, it is contemplated in the interest of simplicity again that these separate means will be coupled individually to the magnets.

Further, according to the invention, a plurality of magnetic reed switch capsules are clustered and a suitable pair of tubular magnets are arranged to slide over the entire cluster. In this manner the plurality of electric circuits are opened and/or closed simultaneously as desired. Such an arrangement is highly advantageous for keyboards and the like. Many keyboard installations require a plurality of switches to be opened and/or closed in sequence, and this is accomplished according to the invention, by offsetting the capsules one to another in such manner that the switch elements of one capsule are completely actuated before the switch elements of the second capsule are actuated and so on.

Key tops of simple construction are given configuration complementary to the configurations of the frame members as to simplify manufacture, reduce the total number of parts and improve the reliability of all of the components. Frame members may be especially designed for electric switches as separate components or as parts of machines in which switch elements according to the invention are installed multiple.

In order that full advantage of the invention may be obtained in practice, preferred embodiments thereof, given by way of example only, are described in detail hereinafter with reference to the accompanying drawing, forming a part of the specification, and in which:

FIG. 1 illustrates an electric switch according to the invention as used in a probe for a data processing system;

FIG. 2 is an illustration of the operation of an electric switch assembly according to the invention; and

FIGS. 3 and 4 illustrate a component keyboard switch assembly according to the invention.

A typical application of an electric switch assembly according to the invention is shown in FIG. 1. A probe 10 forms part of manually operated optical scanning apparatus, such as that shown and described in the copending U.S. Pat. application Ser. No. (not yet assigned--IBM docket SA9-70-040) of David Harwood McMurtry filed on the 30th day of June, 1971. In that system, as in many such systems, it is desirable that a switch be closed when the probe 10 is touched to a document to be scanned. Simple electric switches would seem to be adequate, however, the greatest single component failure with probes of this type to date have been in the probe operate switch. A switch assembly according to the invention as shown in the upper end of the probe 10 has obviated this nagging difficulty. The probe 10 comprises a nose piece 20 which is fitted into one end of a cylindrical barrel 24. At the other end of the barrel an upper end fitting 24 is affixed. Arranged about the barrel 22 is a tubular sleeve 26 which is grasped by the hand of the operator using the probe. A spring 28 arranged in the end fitting 24 has one end pressing between the barrel 22 and a switch actuating pin 30. The latter is fastened to a collar 32 which surrounds the barrel 22 and passes through a slot 34 in the barrel. The upper end of slot 34 determines the normal relationship of the barrel 22 and the sleeve 26. The pin 30 in the slot 34 also confines the rotational movement of the collar 32; while the sleeve 26 is allowed full freedom to rotate about the barrel 24. A circuit board 36 of conventional form is arranged in the barrel 22 to one side of the slot 34. An electric switch assembly 40 according to the invention is arranged in operating relationship to the pin 30. When the operator, using the probe 10, presses the nose piece 20 against the document to be scanned, the relative motion of the probe assembly forces the barrel 22 upward inside the sleeve 26 so that the switch actuating pin 30 moves relatively downward in the slot 34. This relative movement is used to actuate an electric switch assembly 40 according to the invention.

The electric switch assembly 40 comprises a magnetic reed switch capsule 42. The capsule 42 comprises an envelope 44 of non-magnetic material, conventionally glass, into the walls of which are sealed a pair of electric leads 46, 48. These electric leads 46, 48 are integral with a pair of magnetic reed elements 52, 54 supported in the envelope 44 in cantilever configuration. The reeds 52, 54 have electric contacts 56, 58 adjacent one another centrally of the envelope 44. A pair of tubular magnets 62, 64 are loosely arranged about the envelope 44. The magnets, which may be of barium ferrite, are polarized so that the annular faces at the ends thereof are the magnetic poles. Magnets are placed over the envelope 44 with like poles on the adjacent annular faces. This switch assembly 40 is then fastened to the circuit board 36 near the electric switch actuating pin 30 by passing the electric leads 46 and 48 through the board in conventional manner in prearranged apertures. A simple block stop 66 is fastened to the circuit board 36 near the magnet 64. The magnets 62 and 64 repel each other so that in the unactuated position the magnet 62, 64 are urged against the switch actuating pin 30 and the stop 66 respectively. When the pin 30 is moved relatively downward the magnet 62 travels to the center of the envelope 44 and the magnetic field thus moved downward causes the magnetic reeds 52, 54 to bring the contact 56, 58 together completing the electric circuit and indicating to the operator and the associated apparatus that the probe 10 is operative. The simplicity of construction is evident from the foregoing description.

The operation of the switch assembly 40 according to the invention may be more readily understood with reference to FIG. 2. A slightly different mounting arrangement is shown here. A pair of binding posts 68 are arranged on circuit board 36'. The binding posts 68 have slots cut partly through the posts so that leads 46' and 48' may be inserted and held in place by tightening screws 69. This simple structure permits changing capsules without the desoldering and resoldering process necessary with circuit boards or other soldered circuit connections. A bifurcated nonmagnetic finger 30' is also shown for moving one magnet 62. Obviously other simple actuators will be suggested to those skilled in the art. The support post 68 also acts as a stop for the magnet 64 as shown. When the magnet 62 is moved toward the magnet 64 the balance of the magnetic fields is changed. As the magnet 62 approaches the contacts 56 and 58, the reeds 52 and 54 are bent toward each other closing the contacts 56, 58. If the magnet 62 is moved farther toward the magnet 64, the contacts remain closed. This overtravel is of considerable advantage. The drawing is not to scale, hence the relative movement may be misleading as illustrated. In many switch assemblies, an actuator movement of 0.070 inches is sufficient. If both magnet 62 and 64 are moved together simultaneously, the balance of the fields remains unchanged and the switch will remain open.

FIGS. 3 and 4 illustrate a pushbutton switch assembly with a multiple of magnetic reed switch capsules. A base member 36" , which may be a printed circuit board, has a multiple of apertures therein for accepting electric leads 48'. Adjacent each aperture is a metal clip or contact spring for making electric contact with one electric lead of a capsule, and for making connections to other electric circuits as required. A multiple of capsules 81 through 87 have one electric lead 48' inserted in an aperture in the base member 36" . The other electric leads 46' pass through similar apertures in a header plate 88. This header plate 88 is conductive, but alternatively it is nonconducting for applications where separate connectors are necessary. In either case spring clips 92 hold the leads 46' firmly. A conductive post 94, which may be one of three such posts 94, 95 and 96 is arranged to connect electric leads 46' through clips 92 to a terminal 98 beneath the frame member 36" . Thus, if all of the leads 46' are connected in common, a single conductive post 95 is sufficient for bringing out the common connection. Alternatively, more such connections may be brought out as required. A ring or tubular magnet 64' is fastened to the bottom of the switch assembly; a holddown spring clip 99 on the post 98 is one suggested arrangement. A movable ring or magnet 62' is positioned above the magnet 64' in a molded key top 110. The key top 110 has a shoulder 112 which is arranged to butt upward against the top plate in a keyboard; for example, as illustrated by the plate 114 and alternatively against an upper lip of a wall structure 116, as illustrated on the other side of the top 110 on the plate 114. Such a wall structure may be one of four walls forming a key component package. The repelling force between the two magnets 62' and 64' forces the key top 110 upward until finger pressure is used to depress the key top 110 and the upper magnet 62'. An annular slot 118 is arranged in the key top 110 for accepting a split ring whereby the key top 110 and the magnet 62' form a unit assembly. Alternatively, the key top may be molded about the magnet 62' or the latter may be cemented in the key top. Much of the time key tops are circular in cross section so that if the top must be oriented as it would be if letters or figures were engraved in it, a slot 122 is arranged vertically in the shell of the key top 110 into which a guide lug 124 as shown in FIG. 4 is arranged for preventing the key top 110 from rotating about its longitudinal axis. This lug 124 may be held in place in any manner; the arrangement shown here with respect to a sidewall 116 is but one suggestion.

The electric switch capsules 81-87 are adjusted in the clips for making contact as desired when the push-button 110 is depressed. In many applications some or all of the capsules will be arranged for substantially simultaneous actuation. In other applications the capsules will be staggered as shown so that the opening or closing of the contacts occurs at differing intervals. An example of such an arrangement is a serial signal encoding scheme where seven contacts are closed one after the other. Different keys for different characters will have a differing number of capsules. Normally open capsules, normally closed capsules and transfer capsules are available and any combination of such capsules may be used according to the invention. An interlocking arrangement is readily obtained. One magnetic reed capsule is arranged for actuation last. As the pushbutton is depressed the earlier actuated switches set up the coding desired and as the strobe capsule is actuated a flip-flop circuit is activated for latching the keyboard out of operation until the pushbutton is released which will reset the flip-flop readying the keyboard for the next operation. A time delay circuit may be included for insuring complete release.

There are a considerable number of advantages of the switch assemblies as described. No springs are needed to operate the arrangement. Several switches can be arranged in a very small compact space. Very short key travel is required with very light pressure. Keys can be moved or replaced or interchanged readily. The switch assembly is inexpensive and easy to build.

While the invention has been shown and described particularly with reference to a preferred embodiment thereof, and various alternatives have been suggested, it should be understood that those skilled in the art may effect still further changes without departing from the spirit and the scope of the invention as defined hereinafter.

Claims

1. A mechanically actuated electric switch assembly in a probe arrangement having slight mechanical force exerted along said probe arrangement when said probe is actuated comprising,

a tubular shell member having at one end thereof a nose piece for contacting a workpiece,

a frame member rigidly mounted in said shell member,

an electric switching component including a tubular nonmagnetic envelope having at least a pair of magnetic reed elements having cooperating electric contact portions arranged therein and electric lead portions extending outwardly,

a pair of tubular magnets slidably arranged over and supported solely by said envelope with like magnetic poles at opposing annular faces adjacent said reed elements,

mounting members arranged on said frame member

said switching component with said tubular magnets thereabout being fastened by said electric lead portions into said mounting members, and

a sleeve member slidably arranged over said shell member, supported thereby on a resilient member fixed at one end to said shell member for deriving said force when the probe is actuated, and having means intruding into said shell member by way of an aperture therein and arranged in conjunction with at least one of said tubular magnets for moving the same

2. A mechanically actuated electric switch assembly in a probe arrangement as defined in claim 1 and wherein

3. A mechanically actuated electric switch assembly in a probe arrangement as defined in claim 1 and incorporating

further electric components arranged with said electric switching component

4. A mechanically actuated electric switch assembly in a probe arrangement as defined in claim 2 and wherein

said electric switching component is arranged with the tubular axis thereof

5. A mechanically actuated electric switch assembly in a probe arrangement as defined in claim 4 and wherein

said mounting members are comprised by portions of an electric circuit board arrangement.