US1675897A - Safety electric control device - Google Patents

Description

July 3, 1928.

l. E. M CABE SAFETY ELECTRIC CONTROL DEVICE Fil 1 1925 5 Sheets-Sheet l INVENTOR I By ZEM CZBE A TTORNEY July 3, 1928. 1,675,897

I. E. M CABE SAFETY ELECTRIC CONTROL DEVICE Filed June 4, 1925 a Shets-Sheet 2 Fig.2

[N VENTOR 'A TTORNEY July'3, 1928. I 1,675,897

I. E. MGCABE SAFETY ELECTRIC CONTROL DEVICE Filed June 4,1925 I: Sheets-Sheet 3 15'. Means Efl m ATTORNEY ratented July 3, 1928. v

IRA E. HGCABE, OI CHICAGO, ILLINOIS.

SAFETY ELECTRIC CONTROL DEVICE.

Application filed June 4, 1925. Serial No. 34,794.

This invention relates to improvements in electric circuit controls and more particularly to an improved safety device for circuit controls.

It is an object of this invention to provide a device of this character for electric stack arising from the fire pot operates a.

thermostat to close the circuit to the motor operating the burner mechanism. lVhile this is one of the preferred uses of this safety device, the invention is not limited to this use alone. as the principle of this safety device may be applied to other forms of electric circuit controls. where a positive operating safety device is desired which does not depend upon elements that are subject to deterioration or loss of operating power.

In the drawings:

Figure 1 a top'plan view of an embodiment of this invention in a stack control. with parts broken away.

Figure 2 is a view in side elevation of Figure l. partly injsection and with parts broken away.

Figure 3 is a view in front elevation with the cover of the casing removed and the electric circuit shown in diagram.

In this particular embodiment of this invention. the control mechanism is contained within a circular casing 1 secured to one end of a sleeve 2 surrounding one form of a thermostatic stack control element 3 which projects'through the other end of the sleeve and is adapted to enter within the walls 4 of a stack leading from the fire pot of an electrically operated domestic oil burner heater or hot air duct. not shown. and to which the adjacent end of the sleeve 2. is secured, as illustrated in Figure 1. The thermostatic element 3, as illustrated, comprises a tube of resilient metal, preferably containing a thermal fluid, which enters the stack in the form of a loop with one end portion within the sleeve 2 formed into a coil 5 having the free end of the coil adjacent to the casing provided with a prowhich in turn will be jection 6 entering the interior of the casin through an aperture provided therefor. t is readily seen that when the stack is cool the coil 5 willb'e in its normal or contracted position with the projection 6 at one end of its movement and as the stack becomes filled with heated air and gases which pass about the loop of the thermostatic element 3 extending into their path the increase in temperature will be transmitted to the coil caused to expand or uncoil in the nature of a pressure or Bourdon tube thereby causing the projection 6 of the end of the coil to travel as the arc of a circle towards the other end of ,its movement. This movement operates the control switch, or any other type of thermostatic element having a moving part could be employed as well to operate the control switch.

The controlswitch is mounted on a plate 7 pivoted at one end upon a shaft secured thereto mounted to rotate in bearings on two plates 8 and 9 carried upon the rear wall of the casing below the aperture 10 therein through which the pro ection 6 of the thermostatic element enters. The control switch as illustrated comprises a mercury switch tube, 11, with both terminals entering the end adjacent the pivot, mounted upon a rectangular bracket extending from plate 7 and having a counter weight 12 under the end farthest from the pivot so that when acted upon by the counter weight the tube will be tilted so that the mercury will assemble in that end and break the circuit and when tilted beyond the horizontal in the other direction the mercury will assemble about the terminals entering therein and close the circuit. Movement of the projection 6 of thethermostatic element is transmitted to the tilting mercury tube switch 11 by means of a forked link 13 embracing the projection 6 and frictionally engaged to a. boss 14 upon the pivot shaft of plate 7. by splitting the link from the boss to the lower end and engaging the split portions by a set screw. The plate 7 preferably is provided with two spaced apart projections 15 arranged to en gage on either side of one of the studs 16 spacing apart plates 8 and 9 and limit the tilting of the plate 7 and mercury tube switch 11 in both directions. The tilting link 13 is provided with-a frictional engagement with the pivot shaft of plate 7 to allow further expansion or contraction of the coil 5 after the forked link has tilted the mere cury tube switch to the limit of its movement in either direction, the set screw regulating the friction clutch to allow of such movement.

The safety device for the thermostatic operated switch 11 comprises another mercury switch tube 17 carried on a. plate-18 pivotally mounted upon the back of the till casing 1 with the terminals entering the tube at the end adjacent the pivot. The free end of the plate 18 is adapted to engage over a projection 19 upon a pivoted member 20 rotatable about a pivot 21 thereabove and when so engaged will support the plate 18 with points of engagement of free end and pivot in a horizontal plane. The mercury switch tube 17 is mounted upon the plate 18 by clips so arranged that when the plate is horizontal and engaged by the pivoted member 20 the tube will be tilted so that the mercury will assemble at the end adjacent the plate pivot and close the contact between the terminals. It is preferable to provide a plate 22 secured to the rear of the casing which carries the pivots of the plate 18 and member 20 and extends below the plate 18 which will also act as an anchor for a spring therefrom to the underside of the plate 18 to cause the same to firmly engage the upper side of the projection 19 and also as an anchor for a spring therefrom to the rotatable member 20 to cause it to engage the end of the plate 18 and resist disengagement from vibration or jars. The pivot 21 of member 20 is so-arranged that when the member hangs normally the projection thereon will be in line to engage the end of the mercury tube plate 18 so that an outward movement of the pivoted member will release the plate whichwhen freed will drop that end and rotate upon its pivot tilting the mercury tube causingthemercury to assemble at that end and break the contact between the terminals.

In order to impart an outward movement of the pivoted member to free the tube plate 18 after a predetermined time, a bar of expansible metal 23, is mounted to slide in a bearing 24 upon plate 22 and in an adjustable anchor bearing 25 in the side wall of the casing 1. Three binding posts are arranged on the rear wall of the casing below the bar 23, as shown in Figure 3, one.

of which, 26, is connected exterior of the casing to the commercial line and on the interior of the casing to one terminal of the mercury switch tube 11- with the other terminal of this switch tube connected to the adjacent binding post 27 and this bindingpost in turn is connected to one termmal' of the mercury switch tube 17 with the other terminal of that tube connected to the third binding post 28 which binding post on the exterior of the casing is conin Figure 3, illustrating a room thermostat T and boiler control B, customary in oil burner heating systems, in circuit with the safety control switch and motor M. The adjustable anchor bearing of the expansible metal rod 23 is set so that under normal conditions the closing of the main commercial circuit by hand, and when so closed by thermostat T and boiler control B, will pass the current through the resistance coil 29 and switch tube 17 a sufficient time for the motor to operate the burner mechanism to ignite the flame and cause the stack control to operate the switch tube 11 to close the main circuit therethrough before the metal rod is expanded sufficiently to trip the safety switch. Should the burner fiamc fail to ignite or from any cause cease while the motor is operating, the stack control will cool and break the circuit through mercury tube 11 and then the metal rod will expand and disconnect the pivoted member from the safety switch plate allowing the same to tilt and break the circuit therethrough and to the motor. When the safety switch has once operated to break the motor circuit the burner mechanism cannot be started until it has been reset. To reset the safety switch a plunger 30 is mounted in the side wall of the casing 1 directly under the pivoted switch carrying plate 18 which not only limits {the downward swing of the of the casing can beadjusted to regulate the length of the expansible metal rod extending within the casing and thereby the time required, after the motor circuit has been closed while tube switch 11 is open, to expand sufficiently under the heat from coil 29 to trip the safety switch.

It is to be noted that this construction provides a safety device that may be operated innumerable times without showing wear or deterioration and may be depended upon to operate under all conditions. Furthermore the frictional engagement between the forked link 13 and the rotatable pivot secured to plate 7 carrying the mercury tween the forked link and shaft, thereby device for permitting greater movement than that just necessary to throw the switch without injuring any part of the mechanism and the counter weight 12 will always return the switch to open position as soon as the actuating member 6 moves in the opposite direction and then the frictional engagement will permit the member to resume its normal position. The, frictional engagement between these parts not only compensates for movement greater than that necessary to throw the switch in both directions but also in connection with the weight of the switch and counter weight provides an additional safety should at any time or for any reason or in any position of the switch the frictional engagement between these two parts become insufficient' to operate the switch,-the switchwill be at once tilted to the open position and break the circuit. This device therefore contains two safety elements, namely, the time controlled electrically operated lower switch mechanism and the frictional compensating and safety connection between the upper switch and its operating mechanism.

at I claim is:

1. A safety electrical control device including a thermostatically controlled electric switch, an additional switch normally in circuit between said first switch and the main circuit, and a time element between the poles of the first switch completing the main circuit to the second switch for breaking the circuit through the second switch, whereby the closing of the main circuit when the first switch is in V of thermostatlcally controlled switch to close 0 en position will, upon failure within a predetermined time, break the main circuit through the second switch.

2. Asafety electric control device comprising a thermostatically actuated switch and a gravity actuated switch in series therewith, means for detachably maintaining the second switch in circuit, and means operable upon closing the main circuit to release the gravity actuated switch to break the main circuit upon failure of the thermostatically actuated switch to close the main circuit therethrough.

3. A safety electric control device including a thermostatically actuated switch in the main circuit having an additional and gravity actuated switch in series therewith and the main circuit, a shunt circuit between the poles of the first switch, means for'detachably holding the gravity actuated switch in closed position and means actuated by the shunt circuit to release the second switch to be actuated by gravity to brealcthe main circuit upon failure of the first switch to maintain the main circuit closed therethrough.

4. A safety electric control device including thermostatically actuated and gravity actuated switches. in series with each other and the main circuit, a shunt circuit between the poles of the first switch, detachable means .for holding the second switch in closed position against the force of gravity. adjustable means actuated by the shunt circuit, upon failure of the first switch to close a predet-ermined time after the closing of the main circuit, to release the second switch and allow gravity to break the main circuit therethrough. y

5. A safety electric control device having a thermostatically actuated switch, normally open, and a gravity actuated switch, having means'for manually closing the same, connected in series with each other and the main circuit, means for detachably engaging the gravity switch when manually closed, and electrically actuated means in circuit with the first switch actuated by the closure of the main circuit, upon failure of the thermostatically actuated switch to close said circuit therethrough, to release the engagement of the second switch, whereupon gravity actuates the second switch tobreak the main circuit therethrough and through the electrically actuated means.

' 6. A safety electric control device including an automatically controlled switch with a safety switch connected in series therewith comprising a mercury switch tube having terminals adjacent one end and rotatable about a pivot adjacent that end. releasable means normally maintaining the tube in posit-ion to close the circuit through its terminals, and means operable upon closing the open positions, a second tilting mercury on the casing, detach-' tube switch mounted able means normally maintaining the second switch in closed position, one terminal of each switch connected to each other with the other terminals adapted to be connected with the main circuit, a shunt circuit between the poles of the first switch adapted to actuate means for releasing the second switch upon closlng the main clrcuit exterior of the casing upon failure of the first switch within a predetermined time thereafter to close the main circuit therethrough, and means to tilt the released second switch to break the main circuit therethrough.

8. A safety electric control device comprising a casing, two tilting mercury tube switches mounted therein in series with each other and adapted to be placed in series with the main circuit, means upon both switches for tilting them to the open position, means exterior of the casing for automatically tilting one switch to its closed position, means passing through the casing for manually tilting the other switch to closed position, mechanical means adapted to releasably engage and hold the manually tilted switch in closed position, electrically actuated means within the casing for releasing the manually tilted switch to break the circuit, means connecting said last named mean 'n a shunt circuit between the poles of the 0 her switch, whereby the closing of the mairr circuit without the casing causes said electrically actuated means to release he second switch upon failure of the automatic means to tilt the first switch to closed position.

9. In a device of the character described,

a casing, two mercury tube switches having terminals adjacent one end mounted upon brackets turning upon pivots adjacent their terminals upon the casing, whereby they both will assume'the open position, one terminal of each switch having a flexible connection to a terminal of the other and the other terminals of each switch having a flexible connection to atbinding post upon the casing adapted to connect said switches in series with an exterior main circuit, said wall of the casing having an aperture provided adjacentthe pivot of one switch for admitting the entrance of an automatically actuated member adapted to engage the bracket of that switch and when actuated to tilt that switch to closed position, a member pivoted upon the casing above the free end of the bracket of the other switchadapted to engage said bracket and releasal ly hold the same when its switch is tilted to closed position, an expansible rod mounted within the casing having one end anchored and the other end adjacent said pivoted member when holding said switch in closed position, a heat producing coil about said rod connected in shunt circuit between the poles of the automatically actuated switch, whereby upon closing the ma circuit exterior of the casing the shunt circuit will expand the rod to release the switch from the pivoted member to break the main circuit in a predetermined time thereafter upon failure of the automatically switch provided with an attachment to the switch permitting movement of said member beyond that necessary for throwing the switch in either direction, nonresilient means in connection with the switch to positively return the switch to open position upon failure of the attachment, and a gravity operated switch in series with the first switch normally detachably held in closed position and electrically actuated means operable upon closing the main circuit after a predetermined time to release the second switch permitting gravity to turn it to open position upon failure of theautomatically actuated means to close the first switch.

11. A safety electric control device comprising an automatically actuated tilting mercury tube switch, having an operating.

member for tilting said switch with a fric; tional engagement thereto adapted to be engaged by controlling the switch to tilt the switch to open and closed position and permit movement of the operating member therebeyond in relation to the switch, a counter weight connected to themercury switch tube adapted to normally maintain the tube in an open position and return the tube to that position upon failure of the frictional engagement with operating member, and a gravity actuated tilting mercury tube switch in series with the first switch having releasable means normally maintaining tsaid tube in the closed position, an expansible rod adapted to release the gravity switch and a heat producing coil about said rod in a shunt circuit between the poles of the first switch, whereby upon closing the main circuit the failure of'the automatically actuated means to close the first switch will cause the rod to expand and release the gravity switch to break the circuit.

IRA E. MQCABE.

the automatically actuated means I V

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