US2656425A

US2656425A - Safety interlock switch

Info

Publication number: US2656425A
Application number: US226259A
Authority: US
Inventors: Satinoff David
Original assignee: Individual
Current assignee: Individual
Priority date: 1951-05-14
Filing date: 1951-05-14
Publication date: 1953-10-20
Anticipated expiration: 1970-10-20

Description

Oct. 20, 1953 D. sATlNoFF 2,656,425

SAFETY INTERLOCK SWITCH Filed may 14, 1951 INVENTOR.

BY Unep Nn AT ok/Y Patented Oct. 20, 1953 SAFETY INTERLOCK SWITCH David Satinoi, Utica, N. Y., assigner to the United States of America as represented by the Secretary of the United States Air Force Application May 14, 1951, Serial No. 226,259

(Granted Under Title 3'5, U. S. Code (1952),

Sec. 266) 6 Claims.

The invention described herein may be manufactured and used by or for the Government for governmental purposes without payment to me of any royalty thereon.

This invention relates to electrical switching devices and particularly to switches of the safety interlock type. In cabinets or other enclosures for electrical equipment operating at dangerously high voltages, such, for example, as radio transmitters, it is customary as a safety precaution to provide interlock switches on all doors for t'he purpose of automatically deenergizing the equipment when a door is opened. Frequently switches of this type employ spring pressure to open the switch. In such switches the contacts may freeze in their closed position, due to corrosion or moisture and cold, causing the switch to remain closed when the door is opened and thus fail as a safety device. It is an object of this invention to provide a two-piece interlock switch which can under no circumstances remain closed when the door is opened.

It is sometimes necessary to make tests or repairs on equipment when in an energized condition. In such cases the safety interlock is frequently nullified by wedging the switch in a closed position or installing a jumper across the switch. The danger in this is that such makeshift cheating devices may thoughtlessly be left 'in place thus defeating the purpose of the safety interlock. It is accordingly another object of this invention to provide a two-piece safety interlock switch having a built-in cheater which can only be operated intentionally and which, if operated, is automatically rendered inoperative the next time the door is closed.

The structural detail-s of an interlock switch incorporating the above features are shown in the accompanying drawings in which:

Fig. 1 shows a sectional plan view of the interlock switch in closed position;

Fig. 2 shows a sectional elevation of the switch with plug and receptacle parts of the switch separated;

Fig. 3 shows a sectional plan view of the receptacle part of the switch with the cheater in operative position; and f Fig. 4 is an isometric view of the assembled switch. n

Referring to the drawings, the switch is composed of mating plug and receptacle parts generally indicated by the numerals I and 2, respectively. The plug I has a body 3 of insulating material, and molded therein are two internally 2 connected contact prongs 5 and I. Ilhe insulating body of the plug is fastened to a metallic backing plate 1 by rivets 8 and 9.

The receptacle part 2 of the switch consists of a body of insulating material having upper and lower halves I0 and II fastened together and to a metallic angle plate I2 by rivets I3 and I4. The two halves I0 and II of the receptacle body may be, as in the embodiment shown, identical moldings having recesses therein to receive and position the conductors I5 and I6 and the spring contacts I1I8 and I9--20 which are fastened to the ends thereof by any suitable conductive fastenings such as spot welds, etc. Terminals 2| and 22 are provided at the outer ends of conductors I5 and I6 for connecting the switch into an electric circuit.

When the switch is in its closed position, as shown in Fig. 1, the contacts 5 and 6 bridge the gap between contacts I'I and I 9 and thereby complete a circuit between terminals 2I and 22. In the open position of the switch, shown in Fig. 2, the plug is removed from the receptacle and the circuit between terminals 2I and 22 is broken. The plates 1 and I2 provide means for mounting the switch. In a typical use of the switch the receptacle part 2 would be mounted on the chassis of a cabinet enclosing electrical equipment while the plug part I would be mounted on a door to the cabinet. Since opening the doorremoves the plug part from the receptacle part of the switch, failure of the switch to operate when the door isopened is impossible.

In order to permit intentional completion of the circuit between terminals I and 2 when the plug and receptacle parts of the switch are separated, the receptacle part has built into it what may be termed a cheaten This device consists of a plunger 23 having a plate 24 attached to its inner end and carrying connected

spring contacts

25 and 26. The plunger is positioned and guided at its outer end by a passageway 29 formed in the two halves of the receptacle body, and at its inner end by plate 24 which engages and slides in slots 21 and 28 in the upper and lower halves I0 and II, respectively, of the receptacle body. The length of the plunger is sucfh that in its innermost position its outer end protrudes a short way from the receptacle body as shown in Figs. 1 and 2. 'Ihe plug is provided with a recess 30 to receive the protruding end of the plunger when the switch is in its closed position. In order to latch the plunger 23 in its innermost position, which is the inoperative position of the cheaterf the plunger is provided with a notch 3| which engages the edge of the opening in plate l2 through which the plunger 23 passes. The spring finger 32 urges the plunger against this edge of the opening at all times causing the notch and edge to vbecome engaged when the two come into alignment.

When the switch is in the open position, the cheater may be operated by pressing the plunger against spring 32 to disengage the notch 3| and then pulling the plunger all the way out to engage contacts 25-26 with contacts Ill-2B, thus completing a circuit between terminals 2.1 and 22. The cheater may be manually V disengaged at any time by pushing the plunger all the way in so that the connection between vcontacts |8-20 and 25-26 is broken and the shoulder of notch 3l drops in behind plate l2 under the influence of spring 32. However, should `the "cheater be left in its operative position, it will be automatically forced to its latched inoperative 4position by the body 3 of plug .l the next .time the interlock switch is closed. It will then remain in its inoperative position until intentionally .operated in the manner above described. Reopening of the interlock switch will not operate the ch eater even if the plunger should stick to or become frozen to the plug body 3, since .the restraining action of the shoulder of notch 31 against the plate l2 would either cause the plunger to breakaway from the plug .or else cause the plunger itself to break.

l. ,A safety interlock switch having tivo separable mating parte, said switch being closed by joining said parts and opened .by separating said parts, -Ineans attached to one of said parts and manually operable when said switch is open to form an electrical by-pass around said switch, and means attached to the other part of said switch and .cooperating with said manually op erable means when `said switch is closed to remove said electrical by-pass.

.12. A safety interlock switch comprising separable mating plug and receptacle parts, said receptacle part having a pair .of contacts and -a pair of terminals connected to said contacts for connecting said .switch into an electric circuit, said plug part having a pair of contacts electri cally connected together and positioned so as to enga-ge the contacts of said receptacle part and t form an electrical connection Atherebeween when the switch is in its closed position with plug and receptacle parts joined, a second pair of contacts located in said receptacle part and connected to said terminals, a pair of electrically connected movable icontacts in said re ceptacle part, manual actuating means for moving said pair of movable contacts between an in, operative position and an operative position, said pair of movable contacts in said operative position engaging said second pair of contacts and forming an electrical Vconnection therehee tween, and means operated by closing said switch to force said movable contacts from said operative DOsition to said inoperative position.

3. A safety interlock switch comprising sepa-V rable mat-ing plug and receptacle parts, a pair of terminals .associated with said receptacle part for connecting said switch into an electrical circuit, said switch providing a .connection between said terminals in its closed position when said plug and receptacle parts are joined and an open circuit between said terminals in its open position when said plug and receptacle parts are separated, an auxiliary switch in said receptacle part for providing a connection between said terminals, a plunger coannect-exl to said auxiliary switch and protruding from said recep- `tacle part to permit manual operation of said auxiliary switch by pulling said plunger outward from said receptacle part, said plunger protruding from said receptacle part at a point normally covered 'by said plug when said plug and receptacle `par-ts are joined, whereby, if said auxiliary switch is in its operative position, the action ofv said .plug part against said plunger pushes .said auxiliary switch to an inoperative position during closure of said interlock switch.

A. A safety interlock switch for mounting on the door of a cabinet containing electrical equipment for the purpose of closing the energizing circuit of said equipment when .said -door is closed and opening the energizing circuit of said equipment when said door is opened. ,an auxiliary switch in said interlock switch and connected in parallel thereto, means accessible when said door is Iopen for .manually closing said auxiliary switch, and means on :said door cooperating with said manual closing means for opening said auxiliary switch when :said door is closed.

y5. A safety interlock switch ,comprising .separable mating plug and lreceptacle parts; said receptacle part having two pairs of .separated `contacts connected in parallel between two external terminals for connecting the switch into an electric circuit; said plug part having ta pair of contacts electrically connected together and posi toned so as to engage one pair of contacts of said receptacle lpart and to form an electrical connection therebetween when the switch is in its closed position with plug and receptacle parts joined; a pair of electrically connected movable contacts in said receptacle part; plunger means connected to said movable contacts and, when said movable contacts are in an inoperative position, protruding a short way from said receptacle part at a point normally covered by said plug part whensaid switch is closed, whereby. when said switch is open, said movable con tacts may be brought into an operative position References Cited in the le of this patent UNITED STATES PATENTS Number Name yDate 1,414,421 Kries May 2, 1922 2,231,737 Rutter -Feb. 1,1, 1941 2,348,197 Brongersma a May2, 1944 2,503,569 Verkuil Apr. 11,"1350 2,523,125 Ley Septr19, 1950