US3336448A - Non-sparking switching apparatus - Google Patents

Description

Aug 15, 1967 w. R. AIKEN 3,336,448

NON-SPARKING SWITCHING APPARATUS Filed Sept. 2, 1965 5.448 f INVENTOR. dr WILLIAM ROSS AIKEN United States Patent 3,336,448 NON-SPARKING SWITCHING APPARATUS William R. Aiken, Los Altos Hills, Calif., assignor to Electronix Ten, Inc., San Francisco, Calif., a corporation of California Filed sept. 2, 196s, ser. No. 484,633 2 Claims. (Cl. 200--46) ABSTRACT F THE DISCLOSURE A switch arrangement wherein closure or separation of the switch contacts is determined by the position of an interposed movable perforated tape of insulating material. Sparking is prevented by connecting an auxiliary switch into whatever power circuit is controlled by the iirst mentioned switch, and by providing means for opening said auxiliary switch and thus withdrawing power from the iirst switch, whenever the means for effecting movement of the tape is activated. As a refinement the apparatus employs a third switch controlled by the position of the same perforated tape for properly timing the actuation of the auxiliary switch and the state of energization of the tape moving means. When the described apparatus is used in time indicating message signs, a fourth switch controlled by a continuously operating timing cam may be employed in series with said third switch.

The present invention relates to switching apparatus for electrical circuitry, especially circuitry designed to carry high voltage currents. When an electrical circuit is completed by the approach of switch contacts, and especially when a circuit is broken by the detachment of switch contacts, sparking occurs between the contacts. This may damage the contacts by pitting or eroding their contact surfaces, it may adversely effect the switching action itself and it may cause radio interference. To minimize these problems, it is necessary to employ large contact elements and provide for rapid opening and closing of the contacts and for relatively large interspaces between the contacts in open position. All this is costly and may be prohibitive in environments where the use of small contacts with small open gaps and slow speed of switch operation are unavoidable because of considerations of compactness; for instance in apparatus, where it is necessary to t a large number of switches within a conned space. A practical example of such a necessity is the case of the many switches required in the art of changeable message signs whose operation is controlled by a punched program tape of insulating material that is passed between the switch contacts. In such apparatus the operational position of many closely grouped switch contacts depends upon the position of the holes in the tape relative to the contacts; i.e. when there is a solid area of tape interposed between the contacts of a switch the switch is closed, and when one of the holes in the tape has moved between the contacts the switch is closed. In apparatus of this type the condition of the switches is changed in a predetermined manner by advance of the program tape which must necessarily be slow.

It is an object of my invention to provide a switching arrangement wherein sparking between the switch contacts is avoided when the contacts are opened or closed.

More particularly, it is an object of the invention to provide an arrangement for tape controlled switch banks, which avoids spark formation with its harmful consequences between the switch contacts, even though the switch contacts are small, even though they may have narrow -opens gaps, and even though they may have to be crowded into a limited space and movement of the switchcontrolling tape occurs at slow speed.

3,336,448 Patented Aug. 15, 1967 These and other objects of my invention will be apparent from the following description of the accompanying drawings which illustrate certain preferred embodiments thereof and wherein FIGURE 1 is a schematic, partially sectioned perspective of a battery of switches controlled by a punched tape, and shows the switch controlled circuitry and the circuit for the motor which moves the tape, arranged in accordance with my invention.

FIGURES 2A and 2B are schematic illustrations of a battery of switches, similar to FIGURE 1, showing a more elaborate control circuitry and illustrating different operational positions thereof.

In accordance with my invention I achieve the above stated objects by employing an auxiliary switch in an area of the switch-controlled circuitry where space is not critical. This auxiliary switch is timed to break the switchcontrolled circuits and turn off the power before the contacts of the performance control switches are suiciently separated or are sufiiciently approached to one another to make or break the circuits which they control. In this manner sparking between the contacts of the performance control switches, with its harmful consequences, such as pitting and erosion of the contacts, cross talk and radio interference is completely avoided, even though the contacts of the performance control switches may be small and may be placed closely together, and even though control of their operational positions may be effected by a slowly moving tape; and since the .auxiliary switch is located in an area where space is less of a consideration and since only a single such switch may be necessary for a multitude of control switches, the auxiliary switch may have a fast opening and closing action and may have large and widely spaced contacts made of costly erosion-resistant materials, without significantly increasing the cost of the apparatus.

Having first reference to FIGURE 1, the reference numeral 10 identifies an elongated table plate of insulating material. Countersunk in said plate, in a row extending transversely thereof, is a battery of several transversely spaced contact members 12. The upper ends of said contact members form circular contact surfaces that are lush with the upper surface of the table plate, and the lower ends of said contact members project downwardly below the table plate; and attached thereto are lead wires 14 that may lead to the control electrodes of a signalling device of the type illustrated an described in my co-pending U.S. patent application Ser. No. 371,637, now Patent No. 3,304,549, led June l, 1964, for a Composite Signalling Device. Held a limited distance -above the row of contact members 12 is a block 16 which may Ibe made of insulating material. Said block is provided with vertical bores 18 which are aligned with the contact members 12. Held within said bores at the bottom ends thereof are balls 20 of conductive material, such -as brass. Springs 22 of conductive material are inserted into the bores 18 and are compressed between theballs 20 and a plate 24 of conductive material arranged upon the top surface of the block 16, to urge the balls 20 yieldably into conductive engagement with the top surface of the contact members 12. A cover plate 26 of insulating material may be placed over the conductive contact plate 24 and may be suitably secured to the block 16. A lead wire 28 connects the contact plate 24 to a source of power.

Trained over and extending along the top surf-ace of the table plate is a perforated program tape 30 of insulating material that is threaded through the interstice between the block 16 and the table surface 10. One end of said tape is trained over a drive roller 32 which is driven from a suitable motor indicated diagrammatically at 34.

The tape 30 is provided with a multitude of apertures or perforations 36 that are arranged in predetermined patterns and which are intended to permit energization of selected ones of the lead wires 14 and hence of selected ones of the electrodes of the signalling device to which said leads wires are connected, depending upon the location of said perforations transversely of the tape and depending upon the position of the tape relative to the row of contacts 12. When a solid portion of the tape passes between a ball and its cooperating contact member 12, the switch established by said ball and contact member is open and no power is applied to the lead to which said member is connected. However, when advance of the tape moves a perforation 36 underneath a ball, its spring 22 urges the ball into conductive engagement with the top surface of the contact member 12 underneath and thus connects the source of power to its lead 14.

In accordance with my invention I interpose a master control switch 35 in the common power line 28 and I control the operational position of said switch 35 in such a manner that it is closed when the program tape is at rest and that it opens when the program tape moves. In the particular embodiment of the invention illustrated in FIGURE 1 the switch 35 is a normally closed switch and I provide means in the form of a relay 37 that may be operated to open said switch 35 and thus interrupt the common power line 28 whenever the motor 34 is energized to turn the drive roller 32 of the program tape. The coil of the relay 37 is connected in the power circuit of the motor in parallel with said motor. Hence, whenever the power circuit of the motor is closed to energize the motor, the coil of relay 37 is likewise energized and opens the switch 35. Therefore, whenever the program tape begins to movewhich may be effective to move a hole between one of the contacts 12 and its aligned ball 20 and thus close a switch 12/20 or which may be effective to move a solid portion of tape between a ball 20 and its contact member 12 that were formerly in conductive contact with each other, and thus open a switch 12/20 sparking cannot occur because the master control switch 35 is opened at the very moment the motor is energized, and by the time the resultant movement of the program tape is effective to open and/or close the switches 12/20, the balls 12 carry no current.

In the embodiment of the invention illustrated in FIG- URES 2A and 2B the common power line 40 of the performance control switches 42 includes a normally operi switch 44 that is held in closed position by energization of a relay 46 as long as the motor 48 which operates the drive reel 50 of the program tape 52, is at rest (FIGURE 2A). For this purpose said relay 46 is not only arranged to hold switch 44 closed when in energized condition, it is also arranged to hold open -a normally closed switch 54 in the power circuit of the motor 48. The state of ener gization of the relay 46 depends upon the poistion of two series-connected switches 56 and 48 in the power circuit of said relay. Switch 56 is a switch similar in construction to the performance control switches 42 and is controlled by the same program tape 52 as said performance control switches 42. Whenever said program tape is in a position wherein it presents a perforation 60 to one or more of the performance control switches 42, to permit current ow through one or more of said switches, it presents simultaneously an opening or perforation 62 to the rela; control switch 56, effecting closure of said switch.

The second relay control switch 58 is a normally closed switch with which is associated a continuously operating rotary timing cam 64. Said cam is provided with a solitary lobe 66 that acts to open the switch 5S briefly once during each full revolution of the cam 64. With the tape 52 in a position wherein it closes selected ones of the performance control switches 42 and at the same time closes the relay control switch 56, the master switch 44 in the power circuits of the performance control switches 42, is held in closed condition delivering power to said performance control switches and the motor 48 is at rest, because the same relay 46 that holds the master switch 44 in closed position is also effective to hold the motor control switch 54 in open position (FIGURE 2A). The tape 52, therefore, remains at rest. Depending upon the speed of rotation of the timing cam 64, however, the second relay control switch 58 will open briey after a selected time interval causing deenergization of the relay 46 (FIG. 2B). As a result thereof, the motor control switch 54 closes and the motor 4S commences to operate. At the same moment the master switch 44 opens so that power is withdrawn from the performance control switches 42. The tape begins to advance and breaks whichever of the performance control switches 42 were closed, without the occurrence of sparking. Advance of the tape 52 has the added effect of breaking the relay control switch 56 without the occurrence of sparking, because the seriescon nected second relay-control switch 58 was previously opened by the timing cam and is still open at this moment. Therefore, although the continued rotation of said timing cam permits said last mentioned switch 5S to close after a brief interval, the relay 46 remains deenergized because by the time the cam-controlled switch 58 closes, the advanee of the tape 52 has insulated the ball and the contact of the relay control switch 56 from each other. As a result thereof the motor 48 continues to operate and the power circuit to the performance control switches 42 remains interrupted. By providing another aperture 62 in the program tape 52 in longitudinal alignment with and a predetermined distance behind the leading aperture 62, operation of the motor 48 may be brought to a halt and the master switch 44 in the power circuits of the performance control switches 42 may be closed at precisely the time when the next row of performance-determining apertures in the program tape has moved into position underneath the balls in the performance control switches 42. Hence, the advance of the program tape comes to a halt with selected ones of the performance control switches 42 in closed condition, and power is reapplied to said performance control switches at a time when said selected switches have been fully closed by the advance of the program tape (FIGURE 2A). Hence, there will be no sparking across said selected switches; and power will now be applied to the control electrodes of a new set of signalling units of the message sign whose performance is controlled by said switches 42 setting up a new symbol in said sign; and this condition will last until the timing cam 64 has completed a revolution and the solitary lobe 66 of said cam acts again to open the second relay control switch 58 briefly whereupon a new cycle in the operation of the described system is initiated.

By operating the timing cam at speeds at which it completes a revolution within a second, a minute or an hour, the described system lends itself particularly well to the control of time indicating message signs which display numerically the passage of seconds, minutes and/or hours.

While I have described my invention with the aid of certain preferred embodiments thereof, it will be understood that the invention is not limited to the constructional details of the switches or the specific circuitry shown and described by way of example which may be departed from, without departing from the scope and spirit of my invention.

I claim:

1. A switch arrangement comprising a bank of rst switches each having a pair of relatively movable contacts, a tape of insulating material extending between said contacts and containing perforations at selected areas thereof, means for advancing said tape to move said perforations between the contacts of selected ones of said switches and thus close said selected switches, means for applying power to said first switches including a second switch, means for activating said tape advancing means and at the same time holding said second switch means open so as to withdraw power from said first switches when the tape advances, and means including a third switch having contacts at opposite sides of said tape for deactivating said tape advancing means and said switch opening means to arrest movement of said tape at a predetermined position thereof relative to said first switches and to reapply power to said first switches.

2. A switch arrangement especially for the control of time indicating message signs, comprising a bank of first switches each having a pair of relatively movable contacts, a tape of insulating material extending between said contacts and containing perforations at selected areas thereof, means for advancing said tape to move said perforations thereof between the contacts of selected ones of said switches, means for applying power to said switches including a second switch, means including a third switch and a timing cam controlling said third switch for activating said tape advancing means and at the same time holding said second switch open to withdraw power from said first switches when the tape advances, and means including a fourth switch having contacts at opposite sides of said tape for detecting said tape advancing means and said switch opening means so as to arrest movement of said tape at a predetermined position thereof relative to said first switches and to reapply power to said first switches.

References Cited UNITED STATES PATENTS 608,134 7/1898 Lundell 307-136 625,232 5/1899 Wurts 307-115 2,177,771 10/1939 Gravert 200-46 X 3,057,974 10/1962 Cohen 200-46 15 3,139,519 6/1964 Reinschmidt 200-46 BERNARD A. GILHEANY, Primary Examiner. H. E. SPRINGBORN, Assistant Examiner.

Claims (1)

1. A SWITCH ARRANGEMENT COMPRISING A BANK OF FIRST SWITCHES EACH HAVING A PAIR OF RELATIVELY MOVABLE CONTACTS, A TAPE OF INSULATING MATERIAL EXTENDING BETWEEN SAID CONTACTS AND CONTAINING PERFORATIONS AT SELECTED AREAS THEREOF, MEANS FOR ADVANCING SAID TAPE TO MOVE SAID PERFORATIONS BETWEEN THE CONTACTS OF SELECTED ONES OF SAID SWITCHES AND THUS CLOSE SAID SELECTED SWITCHES, MEANS FOR APPLYING POWER TO SAID FIRST SWITCHES INCLUDING A SECOND SWITCH, MEANS FOR ACTIVATING SAID TAPE ADVANCING MEANS AND AT THE SAME TIME HOLDING SAID SECOND SWITCH MEANS OPEN SO AS TO WITHDRAW POWER FROM SAID FIRST SWITCHES WHEN THE TAPE ADVANCES, AND MEANS INCLUDING A THIRD SWITCH HAVING CONTACTS AT OPPOSITE SIDES OF SAID TAPE FOR DEACTIVATING SAID TAPE ADVANCING MEANS AND SAID SWITCH OPENING MEANS TO ARREST MOVEMENT OF SAID TAPE AT A PREDETERMINED POSITION THEREOF RELATIVE TO SAID FIRST SWITCHES AND TO REAPPLY POWER TO SAID FIRST SWITCHES.

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