US 2499958 A
Description (OCR text may contain errors)
March 7, 1950 D. H. KNOWLTON INTERLOCK SWITCH Filed Dec. 18, 1947 INVENTOR. Dar/id h. lfnoa lton BY MM fliforney apparatus.
Patented Mar. 7, 1950 INTERLOCK swrrcn David H. Knowlton, Rockport, Mass, asslgnor to Sylvania Electric Products Inc., a corporation of Massachusetts Application December 18, 1947, Serial No. 792,388
The present invention relates to switches, more particularly to safety switches for high voltage For example, in radio transmitters having enclosing cabinets it is common to provide a door or removable panel with a safety switch closed by the panel to complete a power circuit only when the panel seals the cabinet against hazardous access. In servicing such equipment it is sometimes desired to knowingly deliberately connect the power. This entails varied degrees of difficulty, depending uponv the design of the safety switch used. When a conventional type of safety switch is deliberately closed with the door open the operator may inadvertently disable the safety switch permanently.
An object of the present invention is to provide a safety switch which is normally open whenever released, but which is optionally operable for sustained closure under special circumstances. a switch with the automatic feature that, whenever normally operated to complete the circuit (as where the cabinet door is closed) the switch will be conditioned to open the circuit when next released. By virtue of this latter feature assurance is provided that whenever the safety feature is by-passed during testing, the switch will automatically be restored to normal condition simply by closing the door or panel of the cabinet in which the switch is used.
The following is a detailed description of an illustrative embodiment of a switch for achieving the foregoing objects. In the accompanying drawings which show the illustrative switch,
Fig. 1 is an enlarged lateral view thereofwith a side cover-plate removed,
Fig. 2 is a similar view on a smaller scale of the switch in operative position to complete a power circuit when operated by a cabinet closure,
Fig. 3 illustrates the same switch as it is to be operatedfor completing the power circuit where v the cabinet closure is left open.
In Fig. l the switch is provided with a pair of contacts 10 and I2, mounted on leaf springs l4 and I6 and connected to terminals I8 and 20 respectively for completing an external circuit. A push button 22 is slidably mounted in the front wall 24 of the switch casing for pressing contact it against contact l2. The push button is spring-pressed toward the raised, open-circuit condition by strong leaf spring 26, interposed between the push button and leaf spring [4. When such a switch is mounted adjacent a cabinet A further object is to provide such 9 Claims. (Cl. 200 -159) 2 closure, the closure will depress button 22 for completing the external circuit.
It is sometimes desired to complete the power circuit of the enclosed equipment without being required to maintain pressure on button 22.
For test purposes it is often desired that the service man should be able to connect the power with the door open, yet have both his hands free. Forthis purpose the following additional mechanism is incorporated, the effect of which is to by-pass the safety feature of the'switch temporarily.
Auxiliary push button 28, also slidable in front wall 24 of the switch casing, contacts a stiffened extension 30 of leaf spring [4. When button 28 is depressed, contact I0 is pressed against con tact l2 whether push button 22 'is operated or not. A latch 32 has a laterally offset portion 34 whichllies in the path ofextension 30. Another offset portion 36 of latch 32 is interposed between button 22 and leaf spring 26. Latch 32 has a pivot 38 about which the latch swings in the same direction whether button 22 or button iii! 28 is depressed.
When button 22 is depressed the switch operates in the normal manner to close the contacts, and acts incidentally to pivot latch 32 clockwise. pressed latch 32 pivots clockwise until extension 30 passes beyond, portion 34 of the latch, and leaf spring 26 is thereafter effective to snap extension 34 behind extension 30, thus maintaining the contacts closed although button 28 may be released." When button 22 alone is depressed the contacts will remain closed only so long as pressure continues to beapplied; but when button 28 has once been depressed the contacts remain closed although pressure has been released. It is possible to break connection between contacts l0 and I2 after having depressed button 28 by operating button 22. This has the effect of removing portion 34 from the return sweep of extension 30. When button 22 is depressed and released the switch will be restored to its open condition. Push button 22 is effective to release the previously latched contacts even though button 28 is concurrently operated. Since both buttons are arranged to be depressed by a closure the s witch can always be depended on to be open when the closure is just opened. The service man can freely ignore his act of by-passing the safety feature of the switch after closing the cabinet. Button 22 can also be manually depressed during the testing operations to release latch 32 an restore the open-circuit condition.
Alternatively if button 28 is de- Certaindetailed modifications in the foregoing illustrative embodiment, as well as varied uses of the invention, will occur to those skilled in the art and I therefore desire the appended claims to be accorded broad interpretation consistent with the spirit of the invention.
What I claim is:
1. A electric switch of the class described comprising a pair of contacts mutually biased apart, a push button having a thrust-transmitting connection to one of said contacts, an auxiliary push button having a thrust-transmitting connection to one of said contacts, both push-buttons being effective when operated to move said contacts together, a latch for holding said contacts together when said auxiliary-push button has been depressed, and a spring acting on said latch to move it into the return path of the contact moved by said auxiliary push button.
2. An electric switch of the class described comprising apair of contacts mutually spring-pressed apart, a first push button for pressing said contacts together, an auxiliary push button for pressing said contacts together, and a latch for holding said contacts together when said auxiliary push button has been depressed, said latch having a portion in the line of action of said first push button for moving said latch into switch-releasing position.
3. An electric switch of the class described comprising a pair of contacts mutually spring-pressed apart, a first push button for pressing said contacts together, an auxiliary push button for pressing said contacts together, a latch for holding said contacts together when said auxiliary push button has been depressed, and a spring acting on said latch to move it into the return path of the contact moved by said auxiliary push button, said latch having a portion in the path of action of said first push button for releasing said contacts.
4. A safety switch comprising a pair of contacts one of which is carried by an arm and spring-separated from the other contact, a pair of actuators movable in the same direction for operating said arm and thereby pressing said contacts together, a latch having a portion spring-urged to lie in the path of said arm for holding said contacts together when so moved by one of said actuators, said latch having a portion operable by the other of said actuators for removing said latch from the return path of said arm.
5. A safety switch comprising a pair of contacts one of which is normally spaced from the other and carried by a leaf spring, a switch casing having a side wall, a pair of push buttons slidable in said side wall for moving said leaf spring to close the contacts, a spring-biased latch having a portion biased to lie in the return path of said leaf spring for maintaining said contacts closed when operated by one of said push buttons and having a portion in the path of the other of said push buttons for shifting said latch to releas said leaf spring.
6. An electric switch comprising a set of contacts biased toward unoperated condition, a pair of actuators, each actuator having a force-transmitting connection to said set of contacts and both actuators being effective individually when operated to establish the same operated condition of the contacts, and a latch biased to lock said contacts in operated condition upon operation of one of said actuators.
7. An electric switch comprising a set of contacts biased toward unoperated condition, a pair of actuators, each actuator having a forcetransmitting connection to said set of contacts and both actuators being effective individually when operated to establish the same operated condition of the contacts, a latch biased to lock said contacts in operated condition upon operation of one of said actuators, and a force-transmitting connection between said latch and the other of said actuators effective to unlock said contacts upon operation of said other of said actuators in the direction required to establish the operated condition of the contacts.
8. A switch comprising a set of contacts normally biased to open position, actuating means operable in two different motions to close said contacts, a latch coacting with said contacts and effective to hold them closed following one contact-closing motion of said actuating means, and a force-transmitting connection between said actuating means and said latch effective to operate said latch to contact-releasing position upon contact-closing operation of said actuating means by another motion.
9. A switch including a set of normally separated contacts, a first leaf spring carrying one of said contacts at an intermediate point, said spring being fixed at one end and having an extension beyond said contact, a second leaf spring fixed at one end to overlie said first leaf spring and having its free end near said contact, a first push button slidably mounted for travel toward the free end of said second leaf spring and in the direction to close said contacts, a second push button slidably mounted for travel toward said extension in the direction to close said contacts, and a pivoted latch having a portion extending between said second leaf spring and said first push button whereby said second leaf spring serves to bias both said latch and said first push button toward unoperated position and said latch is operable against that bias by said first push button, said latch having a further portion biased to lie in the path of said leaf spring extension, whereby said latch is operated by said leaf spring extension to swing out of the forward path of said extension and to snap into the return path of said extension during depression of said second push button, and to remain in this configuration until depression of said first push button.
DAVID H. KNOWLTON.
REFERENCES CITED The following references are of record in the file of this patent:
UNITED STATES PATENTS Number Name Date 1,214,920 Holland Feb. 6, 1917 1,234 922 Mattison July 31, 1917 1,912,109 Van Valkenburg et al. May 30, 1933