US1957517A - Electric switch mechanism - Google Patents

Description

May 8, 1934. w. w. WILLIAMS ELECTRIC SWITCH MECHANISM Q Original Filed Aug. 8, 1952 INVENTOR. MAL TER w. w/u I'm r5 BY M J A TTORNEYS.

Patented May 8, 1934 ELECTRIC SWITCH MECHANISM Walter W. Williams, Bloomington, Ill.

Original application August 8, 1932, Serial No. 627,861. Divided and this application August 14, 1933, Serial No. 685,023

2 Claim.

This invention relates to electric switches and more particularly to a thermally actuated switch mechanism particularly adapted as a control in an electrically operated fluid fuel heating system,

5 but may be employed wherever it is desirable to control an electric circuit or operate an electric switch by temperature changes.

It is an object of this invention to provide mechanism responsive to temperature changes for opening and closing an electric switch which is simple and positive in its operation. It is a further object of this invention to provide 'a reciprocating actuating element for throwing the switch from one extreme position to the other and thereafter allow further movement of the actuating element in the same direction without any undue strain upon the switch operating mechanism and immediately throw the switch to the other position upon movement of the actuating element in the opposite direction.

This application is a division of this applicants prior co-pending application Serial Number 627,861 filed August 8, 1932, Electric switch mechanism.

With these and other objects in view, reference is made to the accompanying sheets of drawing which illustrate a preferred form of this invention with the understanding that minor detail changes may be made without departing from the scope thereof, and that while an embodiment of this invention is illustrated as applied to a stack safety, it is not limited to this single use.

In the drawing;

Figure l is a view in front elevation of the insulated switch carrying plate, with cover removed, illustrating the positions assumed by the contacts when operated by the actuating arm at the end of its travel in one direction. I

Figure 2 is a similar view illustrating the positions assumed by the contacts when operated by the actuating arm in an intermediate position.

Figure 3 is a similar view illustrating the positions assumed by the contacts when operated by the actuating arm at the other end of its travel.

Figure 4 is a top plan view, with parts broken an embodiment is illustrated upon the accompanying drawing. As shown, the switch mechanism is mounted upon an insulated plate 1 carried within the casing 2 preferably provided with a removable front plate 3 and with a tubular ex- Q0 tension 4 extending from one side thereof adapted to be received within the tubular portion of a bracket adapted to be secured to the stack of a furnace, or adapted to be passed through and secured to an end wall of a casing 5 secured at one side of the draft pipe 6 of an oil burner, which casing extends within the combustion chamber 8 and at its rear end communicates by passageway 7 to the interior of the draft pipe 6, as shown in Figure 4.

An actuating rod 9 is mounted to reciprocate horizontally through the bore of the tubular portion 4. One end of the U-shaped bi-metallic thermal element 10 is secured to the and of the portion 4 extending within the stack, or mounted 7 within the casing 5 shown in Figures 4 and 5 to be subjected to theheat of the combustion chamber 8. The opposite end of the thermal element is attached to the inner end of the actuating rod 9 as by perforating or bifurcating the end of the thermal element to pass about the actuating rod 9 between horizontal pins 11 on the actuating rod so that upon expansion and contraction of the thermal element, a horizontal, longitudinal movement will be imparted to the actuating rod. 35 Commercial oil burners of the type illustrated in Figures 4 and 5 employ a fan blower, not shown, for forcing air under pressure through the draft pipe 6 to mix and form a combustible mixture with fluid fuel issuing from thenozzle and dis- 9o charging into the combustion chamber 8. The heat within the combustion chamber is excessive, and while iii-metallic thermal members, such as 10, have been developed to withstand excessive heat, yet it is preferable to divert a portion of the air when forced through the draft pipe by the blower to pass through the opening 7 and over the thermostatic member 10 to prevent the deterioration of the thermostatic material.

In some controls for fluid fuel burners, it is desirable to close one circuit before the other is open and this particular switch is designed to fulfill this heed. A contact carrying arm 12 in the form of a strip of resilient metal is secured at its upper end by brackets 13 centrally to the upper end of the panel 1. The end of the actuating rod 9 entering the casing 2 is provided with a plurality of teeth 14 upon its upper side and the contact carrying arm 12 is of such length that it will engage between the teeth of the rod 9 as the rod is a a bio actuated by the thermal element to reciprocate. The contact carrying arm 12 adjacent to its lower end supports the oppositely disposed contacts 15 and 16 which are adapted to engage corresponding contacts 1'? and 18 when the arm 12 is in vertical position as shown in Figure 2. The contact 1'1 is carried upon the lower end of a resilient contact carrying strip 19 secured at its upper end by the bracket 20 to the insulated plate id '1. The other contact 18 is carried upon a similar resilient contact carryi g strip 21 secured by the bracket 22 to the upper portion of the insulated plate 1. The contact carrying arm 12 may be connected by a flexible connection 23 to the bindpost 24 at the bottom of the panel 1. The brackets 26 and 22 are connected by wires 25 and 26 to the binding posts 27 and 28.

Figure 1 illustrates the actuating rod 9 as it approaches one end of its movement caused by the contracting oi the thermal member 10. The end of the contact carrying arm 12 in engagement the teeth 14 has been swung to the right so i maintain the engagement between contacts and 17 and has broken the engagement bet J33 contacts 15 and 18, thereby completing the circuit from binding post 24 to the binding Dost Upon further travel of the rod 9 in the same direction, the end of the contact carrying arm 12 wipe over the teeth as the arm is resilient and t e contact carrying strip 19 is also resilient. n thermal element 10 ceasing to contract beginning to expand, the rod 9 will be moved e opposite direction until it assumes the icai position as shown in Figure 2. Engaget W s maintained between the contacts 16 i? by the resilient strip 19 and the contacts 15 be brought into engagement. Furmovement in the same direction will sepacontacts 16 and 1'7, maintaining contacts 15 engagement as the contact carrying resilient, as shown in Figure 3. 1 onion, the thermal element has apltmit of expansion and the circuit will be closed between binding posts 24 and 28, while the circuit between binding posts 24 and 27 is broken.

. It is to be noted that the reciprocation oi the actuating rod 9 alternately opens and closes the circuits between the binding posts, and in so doing always maintains one circuit closed before the other is opened.

What I claim is:

1. An electric switch mechanism including a reciprocating actuating rod having a plurality of teeth forming a rack thereon, means for reciprocating said rack, three electric contacts, one of said contacts mounted upon a movable arm, yielding means adapted to be engaged between adjacent teeth of said rack whereby reciprocation I of the rod moves the contact upon the arm into and out of engagement with another contact to close one circuit before it opens the other and after said engagement and upon further movement of the rod in the same direction allows the teeth of the rack to travel under the engaging means, and yielding means to maintain the en gagement oi the contacts when made.

2. An electric switch mechanism including a reciprocating actuating rod having a plurality of teeth forming a rack thereon, means for reciproeating said rack including a temperature responsive device engaging said rod, a plurality of electric contacts, one of said contacts mounted upon a flexible movable arm normally engaged by two other contacts on each side thereof, said arm having a free end adapted to be engaged between adjacent teeth of said rack whereby reciprocation of the rod moves the contact upon the arm out oi engagement with one contact and thereafter upon further movement of the rod in the same direction allows the teeth of the rack to travel under the engaging means, and yielding means to maintain the engagement of the contacts first made including a flexible mounting for each :ngaged contact.

WALIER W. WILLIAMS.

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