US3496315A - Intervalometer with slide transfer switch - Google Patents

Description

c.vc. GI'ESE JR ETAL v 3,496,315 INTERVALOMETEKMITH SLIDE TRANSFER SWITCH Filed March 25, 1968 INVENTORS CLIFFORD C. 6/555 DAVID B MOHLEE BY sE/Vi Y5 United States Patent C) U.S. Cl. 200-18 17 Claims ABSTRACT OF THE DISCLOSURE An electromagnetic actuator acting against a spring load is caused to oscillate by means of an interrupter switch which opens the actuator energizing circuit after the actuator acts against the load and closes the actuator energizing circuit after the actuator returns under the bias of the load. A one-way drive mechanism connected between the oscillating actuator and a driven switch progressively steps the driven switch through plural contact positions to energize plural load circuits. The load circuits are energized from the same electrical source that energizes the oscillating actuator. To isolate the load circuits from the oscillating actuator, the interrupter switch is a double throw switch which, when removing power from the actuator, applies power to a load circuit and, when applying power to the actuator, removes power from the load circuit.

The present application is a continuation-in-part of copending application Ser. No. 692,741, filed Dec. 22, 1967.

This invention relates to electrically operated stepping devices which step a load selector switch through plural load circuit operating positions, and more particularly to a control means for such stepping mechanism to isolate the load circuit from the energizing circuit for the stepping device.

It is a common practice to drive selector switches with an electromagnetic stepping mechanism which progressively steps the switch through plural load operating positions. Typically, the electromagnetic mechanism and the selected loads are operated from separate circuits so that a shorting condition in any selected load circuit will not disable the stepping mechanism.

This need for separate electromagnetic and load circuits is ordinarily no problem since the added cost of a separate load circuit is not greater and the larger package required to accommodate the load circuit is easily constructed. However, in critical applications such as those of the aircraft and space industries the additional package dimension and weight can be of decisive importance.

An object of the present invention is to provide a load circuit and a powered selector therefor which are both operable from a single voltage line.

Another object of the present invention is to provide a mechanism to electrically isolate selector switch load circuits from a selector switch operating mechanism energized from the same voltage source.

Another object of the present invention is to provide a load selector circuit having the capability of stepping past defective loads to reach an operative load.

Another object of this invention is to provide a load selector circuit which is well protected against spurious operation thereof by extraneous voltage sources.

A further object of the present invention is to provide a new and improved interrupter switch mechanism for electromagnetic actuators.

'ice

Other objects and advantages reside in the construction of parts, the combination thereof, the method of manufacture and the mode of operation, as will become more apparent from the following description.

In the drawing:

FIGURE 1 is a perspective view with wiring removed and with portions broken away illustrating a device em bodying the present invention.

FIGURE 2 is an enlarged fragmentary plan view illustrating two positions of a control switch employed in the device of FIGURE 1.

FIGURE 3 is a schematic diagram of an electrical circuit suitable for operating the device of FIGURE 1.

FIGURE 1 illustrates a selector switch for selectively energizing a plurality of loads in a predetermined sequence. The selector switch and an actuator therefor are assembled on a frame 10.

The actuator comprises an electromagnet 12 which, when energized, attracts an armature 14. Affixed to the armature 14 is an annular part or plate 16. The plane of the plate 16 is substantially perpendicular to the direction in which the armature 14 moves when attracted by the electromagnet 12.

Interposed between the plate 16 and the casing for the electromagnet 12 are three equally angularly spaced ball elements, not shown. The ball elements are caged between arcuate recesses coined in opposing faces of the plate 16 and the casing for the electromagnet 12. The coined recesses do not appear in the drawing; however, the coining operation raises bosses 18 from the outer face of the plate 16 which bosses are visible in the drawing. The bottom surfaces of the recesses are so inclined that when the armature 14 is attracted to the electromagnet 12, the plate 16 acting against the ball elements caged in said recesses receives a counterclockwise torque, as viewed in FIGURE 1. This torque producing mechanism is more fully disclosed in United States Patent No. 2,496,880, issued to George H. Leland, Feb. 7, 1967.

The torque imparted to the plate 16 as the result of energization of the electromagnet 12 causes a counterclockwise rotation of the plate 16, as viewed in FIGURE 1. The axis of this rotation is determined 'by the aforementioned arcuate recesses and is disposed substantially at the geometric center of the armature 14. The extent of rotation of the plate 16 is determined and limited by the circumferential extent of the aforementioned recesses.

In a typical design, the rotary stroke imparted to the plate 16 by energization of the electromagnet 12 is twentyfive degrees. At the end of the rotary stroke, the ball elements caged by the recesses block the plate 16 against further counterclockwise rotation, as viewed in FIGURE 1, and the plate 16 is held firmly in this position until the electromagnet 12. is de-energized.

Rotary actuators of the type described are converted to electromechanical oscillators by causing the plate 16 to act against a spring during the described rotary stroke and by further causing the plate 16 to operate a switch which interrupts the electromagnetic circuit as it approaches the end of said rotary stroke. With such arrangement, the electromagnet 12 remains energized only long enough to drive the plate 16 against the spring load for substantially its full travel, whereupon the electromagnet 12 is de-energized and the spring load returns the plate 16 to its starting position. By so arranging the interrupter switch that the return of the plate 16 also closes the interrupter switch, a continuous oscillating action is established in the plate 16.

In the device of FIGURE 1, the plate 16 is provided with a radial arm 20 for the purpose of operating an interrupter switch which will be more fully described in the following. The plate 16 is also caused to operate against a load spring by means of a link 22 pivoted at one end to a retaining pin 23 afiixed to the plate 16. Hooked to the opposite end of the link 22 is a coil spring 24 anchored to the frame by means of a pin 26. With this arrangement a counterclockwise rotation of the plate 16 causes the spring 24 to extend and when the electromagnet 12 is de-energized, as will be explained subsequently, the spring 24 returns the plate 16 in the opposite direction. The interrupter switch to be described, together with the spring 24, cause the plate 16 to repeatedly oscillate and cause the link 22 to reciprocate approximately along its own longitudinal axis.

The reciprocating action of the link 22 is used to drive a rotary selector switch in a stepwise unidirectional travel by means of a ratchet assembly illustrated in FIGURE 1, and more fully illustrated in co-pending application Ser. No. 534,463, filed by Clifford G. Giese, Jr., et al., Mar. 15, 1966, now Patent No. 3,405,376, for Rotary Stepping Mechanism. The ratchet assembly comprises a lower end facing ratchet member 28 mounted for rotation on a bearing post 13 fixed to the frame 10. The ratchet member 28 is pivotally connected to the link 22 by pin 30. The oscillation of the plate 16 is thus transmitted through the link 22 to the lower ratchet member 28. It will be understood that the angle through which the lower ratchet member 28 oscillates about the bearing post 13 may differ from the angle through which the plate 16 oscillates, depending upon the directness with which the motion of the plate 16 is transmitted to the ratchet member 28 as determined by the geometric arrangement of parts.

The ratchet member 28 has a one-way drive connection to an interfitting ratchet member 29 located above the ratchet member 28. The: two ratchet members 28 and 29 have axially projecting teeth 31 and 32 respectively, which drivingly engage in one direction of rotation of the ratchet member 28 and slip in the opposite direction of rotation of the rachet member 28. The driven ratchet member 29 thus has a stepwise unidirectional rotary movement.

In the particular embodiment illustrated, it is required that the ratchet member 29 be advanced thirty degrees each time the plate 16 is oscillated through one cycle by the electromagnet 12 in cooperation with the spring 24. To achieve this, it is also required that the ratchet member 28 be oscillated through an angle exceeding thirty degrees so that the teeth 31 of the ratchet member 28, when slipping under the ratchet member 29, will slip more than thirty degrees to permit the teeth 31 to engage new teeth 32 on the upper ratchet member 29. This assures that the upper ratchet member 29 will be driven through a new increment of rotation during each oscillating cycle of the lower ratchet member 28. To assure a driving condition, the lower ratchet member 28, which can slide axially on the bearing post 13, is biased upwardly against the upper ratchet member 29 by means of a spring 36 acting between the frame 10 and the lower face of the ratchet member 28.

The link 22, plate 16 and ratchet member 28 are so designed that the ratchet member 28 will execute approximately thirty-five degrees of rotation during each half cycle of its oscillation. As a result, the lower ratchet member 28, after driving the upper ratchet member 29 through one increment of thirty degrees rotation, will return through an over travel of five degrees and will have a lost driving travel of five degrees before again drivingly engaging the upper ratchet member 29.

To prevent over travel of the driven ratchet member 29 at the end of each power stroke from the driving ratchet member 28, the driven ratchet member is provided with a plurality of angularly spaced apertures 33. Diametrically opposite apertures 33 are engaged by rounded detent members 35 carried by a spring member 37 mounted above ratchet member 29. Spring member 37 acts against the spring 36 and is restrained against rotation by engagement with bushings 39 encircling struts 34 which threadedly engage nuts 11 fixed to the frame 10.

During each power stroke of the driving ratchet mem- Pressed concentrically into the driven ratchet member 29 is an upright vertically extending shaft 46 having a double D cross section at its upper end. The lower end of the shaft 46 has a small diameter extension, not shown, seating in a bore 27 in the upper end of the bearing post 13. An apertured strap 41 mounted on and extending between the struts 34 cooperates with the bearing post 13 to support the shaft 46 for rotation about a vertical axis, as viewed in FIGURE 1.

The struts 34 support an annular insulating wafer upon which is mounted a plurality of radially disposed electrical contacts, only two of which, identified by the reference numbers 47 and 48, are detailed in FIGURE 1. The wafer 40, together with the contacts mounted thereon, comprise a stationary section for a selector switch.

Rotatably received in the center of the wafer 40 is an insulating insert 42 drivingly connected to the aforementioned shaft 46 by means of a double D aperture therein which receives the upper end of the shaft 46. Secured to the insert 42 is an annular conductor ring 43 from which projects a radial outward tab or contact 44. The insert 42 with its attached conductor ring 43 comprise the rotary section for the selector switch.

As will be more fully described, the upper face of the wafer 40 supports a total of twelve radially disposed contacts, including the contacts 47 and 48 illustrated, the twelve contacts being spaced at approximately equal angular intervals of thirty degrees about the axis of the shaft 46. The contact 47, which is long enough to engage the conductor ring 43, is in continuous contact with the ring 43 at all rotary positions of the insert 42. Each of the other eleven contacts mounted on the upper surface of the wafer 40 has the same length as the contact 48 and accordingly is electrically connected to the ring 43 only when engaged by the tab 44.

The contact 47 functions as a feeder contact for feeding a voltage to the ring 43. By the previously described incremental rotation, the tab 44 is caused to successively engage each of the other eleven contacts on the upper surface of the Wafer 40 so as to successively apply the voltage fed to the ring 43 to each of said other contacts.

The circumferential extent of the tab 44 is such that one and only one of the contacts on the wafer 40 can be engaged at any given instant. Thus, as the tab 44 is driven from engagement with one of the stationary contacts to the next adjacent stationary contact, the tab 44 disengages the one contact before engaging the next contact. A tab of this dimension is referred to as a non-shorting tab or contact since it is not possible for the tab 44 to short across any pair of the contacts mounted on the wafer 40.

An interrupter or control switch suitable for controlling the drive assembly for the rotary insert 42 is designated generally in FIGURE 1 by the reference number 50 and illustrated in greater detail in FIGURE 2. The interrupter switch is basically a slide switch assembled upon a rectangular insulator 52 secured to the frame 10 by means of screws 54. The insulator 52 is spaced from the plane of the frame 10 by bushings 56.

The insulator 52 has a rather large window which slidably receives an insulating wafer 58 having a central, rectangular opening 60. Fixedly mounted to one face of the wafer 58 is a conductive frame 62 which is rectangular except for an outwardly projecting tongue or contact 66. A duplicate frame with outwardly projecting tongue is also fixed to the opposite face of the wafer 58.

The interior margins of these frames are spaced outwardly from the interior margin of the opening 60.

The wafer 58 has a width dimension slightly smaller than the width dimension of the window in the insulator 52 and a length dimension considerably less than the length dimension of the window so that the wafer 58 can slide freely from side to side, as viewed in FIGURE 2. The conductive frame 62 and its counterpart on the opposite side of the wafer 58 extend beyond the outer margins of the wafer 58 and cooperate to support the Wafer 58 in the plane of the insulator 52.

The opening 60 receives a cylindrical cam or operator 64 fixed to and depending from the arm 20 on the plate 16. The cam 64 transmits movements of the arm 20 to the wafer 58 by engaging the interior side margins of the opening 60. Since the cam 64 is much smaller in diameter than the overall length of the opening 60, not all of the motions of the arm 20 are transmitted to the Wafer 58. Also, since the frame 62 and its counterpart are spaced outwardly from the margins of the opening 60, the cam 64 does not electrically contact these frames.

The longer edges of the wafer 58 which slidably abut the window edges in the insulator 52 are preferably arranged parallel to an imaginary line extending between the extremes of the arcuate movement of the cam 64. Thus, the linear path along which the wafer 58 slides reciprocally is parallel to the chord defined by the extremes of the arcuate movement of the cam 64. Also, the side margins of the opening 60 in the wafer 58 are preferably perpendicular to said imaginary line.

The outwardly projecting tongue 66 on the frame 62 is adapted to wipe under contacts 68, 70 and 72 mounted on the insulator 52. In the solid line position illustrated in FIGURE 2, the tongue 66 underlies the contacts 68 and 70 and physically touches these contacts so as to establish a conductive path therebetween. The arm 20, when executing a counterclockwise stroke to the dotted line position illustrated in FIGURE 2, slides the tongue 66 to its dotted line position in which the tongue 66 establishes a conductive path between the conductors 70 and 72. The tongue 66 engages the contact 70 at all times.

The operation of the switch S is best described with reference to the schematic circuit diagram illustrated in FIGURE 3. Wherever possible, the reference numerals identifying circuit components pictorially illustrated in FIGURES 1 and 2 are also utilized to identify the schematic representation for such circuit elements employed in FIGURE 3.

The circuit includes a first terminal 84 adapted to be connected to the positive terminal of a voltage source and a second terminal 85 which is grounded. A resistance 86 and series push-button switch 88 connect the positive voltage terminal through a conductor 90 to contact 70 of the interrupter switch. Closure of the push-button switch 88 thus applies the positive voltage to the contact 70 which, as described, is engaged at all times with the tongue 66.

In the circuit as illustrated in FIGURE 3, the tongue 66 also engages contact 68 with the result that the positive voltage is applied through conductor 92 to an inductance coil 94 which represents the driving coil for the electromagnet 12. Accordingly, with the circuit condition illustrated in FIGURE 3, closure of the push-button switch 88 energizes the electromagnet 12 with the result that the armature 14 will be attracted to the electromagnet and cause the arm 20 to execute a counterclockwise stroke, as viewed in FIGURE 2. The initial portion of this stroke will have no effect on the switch 50 since the cam 64 will merely traverse the opening 60 in the wafer 58 without changing the position of the wafer.

As the arm 20 approaches the end of its counterclockwise stroke, the cam 64 will engage the left side margin of the opening 60 and, continuing its travel, will slide 6 the Wafer 58 to the left, as viewed in FIGURE 2. The initial portion of this sliding movement will have no effect upon the operation of the switch 50 since the tongue 66 will remain in engagement with the contact 68.

In the preferred construction, continued leftward movement of the wafer 58 will bring the tongue 66 into engagement with the contact 72 before the tongue 66 is disengaged with contact 68. Thus, at the instant the tongue 66 engages the contact 72, the electromagnet 12 remains energized. Also, when the tongue 66 engages the contact 72, the positive voltage is applied through conductor 96 to the previously described feeder contact 47 and accordingly, to the conductor ring 43.

At the same time these events are occurring, the counterclockwise rotation of the arm 20 is being relayed to the driving ratchet member 28 through the link 22 and, through the driven ratchet member 29, to the shaft 46. The movement of the shaft 46 is so synchronized with the movement of the arm 20 that the tab 44 on the rotary switch section has engaged a new contact on the wafer 40 at or before the instant that the tongue 66 engages the contact 72. When the new contact engaged by the tab 44 is a load contact, as will be described, the load receives energy before voltage has been removed from the coil 94. Since the arm 20 is moving during this shorting condition, the time duration of the shorting condition is exceedingly small.

Exactly when the electromagnet will be de-energized will depend upon the nature of the load circuitry. If the load is a low resistance element or if the load operates to a short circuit, the load may shunt the coil 94 before the tongue 66 can physically separate from the contact 68. For some operating requirements, this condition is desirable since arcing at the contact 68 is thereby retarded.

On the other hand, if the load constitutes a high resistance, the electromagnet will remain energized until physical separation has occurred between the tongue 66 and the contact 68. In this case particularly, there will be a tendency for arcing to occur at the break of circuitry between the tongue 66 and contact 68 upon discharge of the coil 94. This arcing tendency results from a very brief time delay required to allow the diode 98 to become conductive as the voltage bias thereon reverses. This tendency to arcing is substantially eliminated by placing capacitor 104 across the contacts 70 and 68. The presence of the capacitor 104 delays generation of a back E.M.F. in the coil 94, allowing the tongue 66 to contact 68 to separate without arcing during the time required to render the diode 98 conductive.

In any event, at some point during the counterclockwise stroke of the arm 20, the electromagnet will be deenergized and will discharge through diode 98 connected across the coil 94. This discharge ultimately collapses the magnetic field about the coil 94. However, current induced in the coil by the collapsing field has a path through the diode and the coil which prolongs the magnetic attraction of the electromagnet. This reduces the cycling speed and aids completion of the counterclockwise stroke of the arm 20 which continues by reason of the momentum built up in the rotating armature 14 and its attached plate 16. Preferably, the design of the electromagnet is such that this momentum alone will carry the arm 20 to the end of its permissible stroke, whereupon any remaining momentum associated with the armature 14 is absorbed by impact between the ends of the coined recesses in the plate 16 and the ball elements caged by such recesses. After this impact occurs, the energy accumulated in the spring 24 returns the arm 20 toward its solid line position illustrated in FIGURE 2.

Nothing happens to the electrical circuitry of FIGURE 3 during this clockwise return until the cam 64 on the arm 20 has crossed the opening 60. Of course, during this return, the rotary insert 42 is being held non-rotatably by the detent members 35 as the driving ratchet member 28 slips under the driven ratchet member 29. The time interval required for the cam 64 to return across the opening 60 provides a dwell period during which the application of voltage to the load circuitry is sustained to assure operation of the selected load.

After the cam 64 has traversed the opening 60, the continuing return of the arm 20 moves the wafer 58 to the right, as viewed in FIGURE 2, transferring the voltage from the contact 72 to the contact 68. As this transfer occurs, the tongue 66 will momentarily short across contacts 68 and 72 and again, depending upon the nature of the load, the application of a voltage suflicient to recreate the magnetic field about the coil 94 may be delayed until the return of the arm 20 has carried the tongue 66 through this shorting condition. In any event, the return of the arm 20 eventually results in reapplication of voltage to the coil 94 and results in initiation of a new counterclockwise stroke of the arm 20.

As previously described, the driving ratchet member 28 has an excess of travel with respect to the driven ratchet member 29 during the return stroke. This excess of travel in the ratchet member 28 assures that this ratchet member will have returned sufiiciently far to engage new teeth on the ratchet member 29 before the field surrounding the coil 94 becomes sufficient to re-initiate the counterclockwise movement of the arm 20.

In a typical embodiment, the time required for a complete counterclockwise stroke and clockwise return of the arm 20 is measured in thousandths of a second. The illustrated device has twelve selector switch positions and accordingly all twelve selector switch positions will be reached in a fraction of a second. The push-button switch 88 which initiates operation of the electromagnetic drive is preferably a manual switch and one intended mode of operation is one wherein the operator holds the switch 88 in its manually depressed condition until all twelve positions in the selector switch have been reached. It is ordinarily not possible for the operators reflexes to act in time to enable him to release the push-button switch 88 until all of the selector switch positions have been reached.

FIGURE 3 schematically illustrates ten load contacts numbered 73, 74, 75, 76, 77, 78, 79, 80, 81 and 82. A full operating cycle in which all of the load contacts are successively energized is commenced with the tab 44 engaging contact 48 on the stationary wafer. When the pushbutton switch 88 is depressed, positive voltage is applied to the coil 94 initiating a first stroke of the arm 20 which carries the tab 44 to engagement with the contact 73, energizing any load connected to the contact 73 through the feeder contact 47 and the conductor ring 43. The previously described operation of the interrupter switch 50 de-energizes the electromagnet coil 94 to permit the spring 24 to return the arm 20, thus restoring power to the coil 94 and initiating a new operating cycle during which the tab 44 is advanced to the load contact 74. In repetitive fashion and before the operator releases the push-button switch 88, the tab 44 advances successively through each of the load contacts. This sequentially energizes any and all loads connected to the contacts 73 through 82.

Should any given load be defective so as to produce either an open circuit, or, at the other extreme, a direct short to ground, that load cannot be fired. However, this condition does not otherwise adversely affect the operating cycle. The operating cycle will continue since the tongue 66 will always interrupt power to the coil 94 for a time sufficient to allow a return of the arm 20. Thus, the described circuit will fire all operative loads in the load circuit.

After the load connected to contact 82 has been fired, the electromagnet 12 continues its stepping action carrying the tab 44 under the feeder contact 47. In this position no additional load is fired, but the electromagnet 12 continues its stepping action to move the tab 44 into engagement with the contact 48.

When the tab 44 first engages the contact 48, the arm 20 will be traveling to the left, as viewed in FIG- URE 2, and advancing the tongue 66 toward engagement with the contact 72. When the tongue 66 engages the contact 72, a voltage supply to the coil 94 will be created through contact 72, conductor 96, feeder contact 47, conductor ring 43, stationary contact 48, conductor 99 and conductor 92. This new path sustains the application of voltage to the coil 94 even after the tongue 66 has separated from the contact 68. Accordingly, the electromagnet 12 will remain energized when the tab 44 reaches the contact 48 and will not de-energize as in all previous cycles. As a result, the coil 94 will hold itself in an energized state until such time as the push-button switch 88 has been released by the operator. Until the operator has released the push-button switch 88, the several loads connected to the contacts 73 through 82 cannot again be fired.

The mode of operation in which all loads are successively operated with one depression of the push-button switch 88 is called a ripple operating or firing mode. There exist applications however in which it is desired that one and only one load be operated with each depression of the push-button switch 88. To allow this type of operation, a manually operable switch 100 is placed between the conductor 92 and a conductor 102 leading to the push-button switch 88. In effect, this manual switch circuit is between the slide switch contacts 68 and 70. When the switch 100 is closed, a depression of the push-button switch 88 will supply the input voltage directly to the coil 94 initiating a counterclockwise stroke of the arm 20. Assuming a Starting position in which the tab 44 engages the contact 48 on the stationary selector switch wafer 40, manual depression of the push-button switch 88 with the switch 100 closed will energize the electromagnet 12 to advance the tab 44 to engagement with the selector switch contact 73. During this same motion the tongue 66 is shifted to the left, as viewed in FIGURE 2, to engage contact 72, thereby applying voltage to any load connected to load contact 73. However, disengagement of the tongue 66 from the contact 68 as it moves to the left will not be efiective to de-energize the electromagnet coil 94 since voltage remains on the coil by reason of the closed switch 100. The coil 94 thus remains energized until the pushbutton switch 88 has been released, whereupon the magnetic field about the coil 94 collapses, permitting the spring 24 to return the arm 20 so that a new operating cycle can be initiated. With the switch 100 closed, then, only one load can be fired with each depression of the push-button switch 88.

If, upon depression of the push-button switch 88 in this single fire mode, the selector should step to a defective load which leaks to ground, the defective load will not fire. Nevertheless, the next load in order will automatically fire since the defective load shunts the power to ground, allowing collapse of the magnetic field about the coil 94 and a return of the arm 20. This takes the selector tab 44 off the defective load circuit and initiates firing of the next load in order. Thus, the selector circuitry will automatically step past defective loads to fire an operative load.

Contacts 73a through 82a, appearing in FIGURE 3, are mounted on the backside of wafer 40 directly under the respective load contacts 73 through 82. At an intermediate position between the contacts 47 and 48, but underneath the wafer 40, is a feeder contact 108 connected to ground.

The feeder contact 108 slides upon an annular conductor ring 110 mounted on the underside of the insert 42. The conductor ring 110 is notched as shown at 112. The notch 112 is aligned with the tab 44 on the opposite face of the insert 42.

Each of the contacts 7311 through 82a has conductive connection with its overlying load contact through a common mounting rivet penetrating the wafer 40. Whenever the tab 44 engages one of the load contacts 73 through 82, all other load contacts are grounded by means of the conductor ring 110. Only the load contact being engaged by the tab 44 is ungrounded, this due to the notch 112 and the conductor ring 110. This grounds all loads at both ends, except the load to which voltage is being applied and prevents an accidental firing of a load as may otherwise occur on circuit exposure to extraneous power sources such as produced by radiant energy.

It will be noted by those skilled in the art that the present circuit is particularly safe against an accidental load firing by extraneous energy sources. Thus, when the intervalometer is not operating through closure of the push-button switch 88, extraneous power sources can fire a load only if sufficiently energetic to operate the electromagnet 12 and then only if sufficiently prolonged in time to fire a load thereby selected.

The tongue 66 has been described as a shorting contact. However, it will occur to those skilled in the art that the present device will operate with substantially equal efiectiveness, although on a time cycle differing in minor respects, if the tongue 66 is designed as a nonshorting contact.

Although the preferred embodiment of the device has been described, it will be understood that within the purview of this invention various changes may be made in the form, details, proportion and arrangement of parts, the combination thereof and mode of operation, which generally stated consist in a device capable of carrying out the objects set forth, as disclosed and defined in the appended claims.

Having thus described our invention, we claim:

1. A device of the class described comprising: a part having two positions, means biasing said part to one position thereof, motive means to move said part to the other position thereof, a load switch, means drivingly connecting said part to said load switch, a control switch having a first member supporting spaced first and second contacts and a second member supporting a third contact, terminals for connection to a source of power, a first circuit to connect said motive means in series with said terminals through said first and third contacts, a second circuit to connect said load switch in series with said terminals through said second and third contacts, said part having an operator member engageable with one of said first and second members to move said one member relative to the other member to engage said first contact with said third contact while disengaging said second and third contacts in said one position of said part whereby said motive means is series connected to said terminals in said one position, and to engage said second contact with said third contact while disengaging said first and third contacts in the other position of said part whereby said load switch is series connected to said terminals in said other position.

2. The device of claim 1 wherein said one member is said second member and said third contact is a shorting contact moved by said operator member through a third position spanning the space between said first and second contacts.

3. The device of claim 1 wherein said one member is said second member and said operator member has lost travel with respect to said second member during a portion of the movement of said part between said two positions thereof.

4. The device of claim 1 including a third circuit connecting said third contact and said second contact, said third circuit including a switch.

5. The device of claim 1 wherein said load switch comprises a stationary element and a movable element, one of said elements supporting a selector contact and the 10 other of said elements supporting a plurality of load contacts, said means drivingly connecting said part to said load switch comprising a one way drive means connected between said part and said movable element.

6; The device of claim 1 wherein said part is a rotary part and said two positions are two angularly spaced positions of said rotary part.

7. In combination, a slide switch and an actuator therefor, said actuator including a part rotatable about an axis and motive means to reciprocally rotate said part through a limited angle about said axis, an operator member disposed in spaced relation to said axis and fixed to said part whereby said part reciprocates said operator member through a circular arc concentric to said axis, said slideswitch including a stationary member carrying a first contact and a movable member carrying a third contact, means supporting said movable member for movement adjacent said stationary member along a linear path substantially parallel to an imaginary line connecting the extremes of the arcuate movement of said operator member, said movable member having margins spaced along said linear path and engageable with said operator member, said operator member engaging one of said margins in one direction of its arcuate motion and engaging the other of said margins in the opposite direction of its arcuate motion, said operator member moving said third contact to engage said first contact in one direction of its arcuate motion and separating said first and third contacts in the opposite direction of its arcuate motion.

8. A combination according to claim 7 wherein said actuator includes terminals for connection to a source of power to operate said motive means, said first and third contacts being disposed in a circuit connecting said terminals in series with said motive means.

9. The combination according to claim 8 wherein said stationary member carries a second contact spaced along said linear path from said first contact, said operator member moving said third contact to engage said second contact in said opposite direction of its arcuate motion, said second and third contacts being disposed in a circuit for connecting said terminals in series relation with a load.

10. A combination according to claim 7 wherein said operator member has lost arcuate travel in moving from engagement with one of said margins to engagement to the other of said margins.

11. The combination according to claim 9 wherein said third contact has an extent along said linear path which is at least equal to the space between said first and second contacts.

12. In combination, a slide switch and an actuator therefor, said slide switch including a stationary member having one contact fixed thereto and a movable member having an other contact fixed thereto, means supporting said movable member for movement adjacent said stationary member along a substantially linear path, said one contact engaging said other contact in one portion of said linear path and being separated from said other contact in another portion of said path, said movable member having margins spaced along said linear path, said actuator including a part and motive means to reciprocate said part along a limited path, said part having means to engage one of said margins in one direction of its reciprocating motion and to engage the other of said margins in the opposite direction of its reciprocating motion, said part moving said movable member to engage said other contact with said one contact in one direction of its reciprocating motion and moving said movable member to separate said other contact from said one contact in the opposite direction of its reciprocating motion.

13. The combination according to claim 12 wherein said part has lost travel with respect to said margins of said movable member during a portion of the reciprocating motion of said part.

14. A device of the class described comprising: a part having two positions, means biasing said part to one position thereof, motive means to move said part to the other position thereof, a load switch, means drivingly connecting said part to said load switch, terminals for connection to a source of power, a control switch having first and second positions, a first circuit closed by said control switch in said first position to connect said motive means in series with said terminals, and opened by said control switch in said second position, a second circuit closed by said control switch in said second position to connect said load switch in series with said terminals, and opened by said control switch in said first position, said part having an operator member to move said control switch to said first position on movement of said part to its one position and to move said control switch to said second position on movement of said part to its other position.

15. The device of claim 14 wherein said operator member has lost travel with respect to said control switch during a portion of the movement of said part between its two positions.

16. A device of the class described comprising a part having two positions, means biasing said part to one position thereof, motive means to move said part to the other position thereof, a load switch, means operatively connecting said part to said load switch, a control switch having a first member supporting spaced first and second contacts and a second member supporting a third contact, a terminal for connection to a source of power, a first circuit to connect said motive means in series with said terminal through said first and third contacts, a second circuit to connect said load switch in series with said terminal through said second and third contacts, said third contact being disengaged from said first contact and engaging said second contact when said part is in said one position, an operator member driven by said part upon movement of said part to said other position to move said one member relative to said other member in a direction to disengage said third contact from said second contact while moving said third contact to engagement wi'h said first contact.

17. The device of claim 16 wherein said load switch comprises a stationary element and a movable element, one of said elements supporting a selector contact and the other of said elements supporting a plurality of load contacts, said means operatively connecting said part to said load switch comprising a one-way drive means acting between said part and said movable element of said load switch.

References Cited UNITED STATES PATENTS 706,084 8/1902 Moskowitz 200-17 1,302,089 4/1919 Read 200-14 2,864,911 12/1958 Brumfield 335-69 2,737,548 3/1956 Mead 200-18 3,157,752 ll/ 1964 Eichacker 200-18 ROBERT K. SCHAEFER, Primary Examiner J. R. SCOTT, Assistant Examiner US. Cl. X.R.

Patent No.

Inventor(s) Clifford C. Giese, Jr. and David B. Mohler Dated Februarv 17, 1970 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Col. 1, Col. 2, Col. 6,

10, line 15,

12, line 2,

line 51, "greater" should be --great--. line 38, "1967" should be -1950--.

line +9, "to contact 68" should be --and contact 68 "slideswitch" should be --slide switch-.

change "first" to --second--; change "second" to --first--; change "said one member" to --one first and second members--; change "second" to --first--; change "first" to --second--.

line 3, line 6, of said line 7, line 9,

SIGNED AND SEALED AUG 4 -1970 mumedmlr.

Awning Officer mm: B- SGHUYLER, .13. Commissioner of Patents

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