US2476448A - Stoker timer - Google Patents

Description

E. B. MAIRE STOKER TIMER July 19, 19490 Filed Jan.

Patented July 19, 1949 STOKER TIMER Edward B. Maire, Glen Ellyn, Ill., assignor to Penn Electric Switch 00., Goshen, Ind., a corporation of Iowa Application January 23, 1945, Serial No. 574,189

2 Claims.

My present invention relates to a stoker timer and particularly to one that is designed for the purpose of turning the stoker on at will or off at will as when cleaning the fire, with assurance that the control circuit will again be rendered operative a short period of time after it is turned off" without attention of the operator.

One object of the invention is to provide a simple arrangement for turning a stoker 01f, combined with the usual stoker timer for energizing the stoker periodically for hold-fire purposes, the timing mechanism that drives the hold-fire timer also driving my timer to insure that it will be brought back into operation without the necessity of the operator throwing a switch or performing some other operation for this purpose.

In connection with automatically stoked furnaces wherein the stoker is controlled by a room thermostat, it is desirable to insure that the room thermostat does not cause the stoker to operate while removing clinkers from the fire, as stoker operation forces air into the furnace and the operator is likely to get his eyes full of fly ash when the stoker operation starts. To insure against this, it has been common practice to provide a switch that cuts off the circuit to the room thermostat but it is necesary that the operator close this switch after he cleans the fire, otherwise the stoker cannot operate. It is accordingly an important purpose of my invention to provide a stoker timer arrangement wherein the circuit can be cut off, but it will automatically come back on after a time period sufiicient for cleaning the fire, thus eliminating the possibility of forgetting to close a switch so that the stoker can continue to operate automatically.

A further object is to provide a stoker timer designed with a second timer switch in addition to the hold-fire timer switch, the second switch being operable to open the circuit to both the room thermostat and the hold-fire timer switch so that neither can cause operation of the stoker, the second timer switch, however, being operated by the timing mechanism so that it remains in the off position only a short period of time, thus insuring that the stoker will be brought back into automatic operation without further attention by the operator.

Still a further object is to provide the stoker timer arranged so that it can be manually set to an on position if the operator wants to observe the condition of the fire after he has cleaned it.

With these and other Objects in View, my invention consists in the construction, arrangement and combination of the various parts of my stoker timer whereby the objects contemplated are attained, as hereinafter more fully set forth, pointed out in my claims and illustrated in the accompanying drawings, wherein:

Figure 1 is an electro-diagrammatic view of a stoker timer embodying my invention.

Figures 2 and 3 are views similar to a portion of Figure 1 showing the timer in diiierent positions and Figure 4 is a sectional view as on the line 44 of Figure 1 showing mechanical details of the timer cam and its manual setting mechanism.

On the accompanying drawing I have used the reference numerals I0 and 12 to indicate current supply wires for a motor M of an automatic stoker or the like. The circuit of the motor M is controlled by the usual motor switch I4 and limit switch IS in series with each other. The motor switch I4 is adapted to be closed by energization of a relay coil l8, the mechanical connection being illustrated by the dotted line 20.

Current for the relay coil [8 may be supplied from the wires Ill and [2 either directly or through a step-clown transformer, the primary of which is indicated at 22, the core at 24 and the secondary at 26. A room thermostat RT is provided for controlling energization of the relay coil l8 and there is also provided a timer switch indicated at 28. This may be termed a holdfire timer switch as it is adapted to close the circuit periodically, for instance, once every half hour to thereby keep the stoker fire from going out, particularly when the weather is mild and there are but few calls for heat by the room thermostat.

The timer switch 28 has its terminals indicated at 3!! and 32 and the switch itself is open in Figure 1. The room thermostat, it will be noted, shunts the switch 28 or is connected to the terminals 30 and 32 so that either the room thermostat or the timer switch 23 can operate the stoker. One of the two operating positions is shown in Figure 2 wherein the switch 28 has been closed.

For closing the switch 28, a cam 34 is provided having depressions 36 and 38 for providing the hold-fire periods. These may be of suitable depth for hold-fire periods of desired length, for instance 3 or 4 minutes and of course may be adjustable whereas the cam 34 may be provided with one or three cam depressions if it is desired to have a hold-fire period once each hour or each quarter hour instead of each half hour as illustrated on the drawing. This however forms no part of my present invention.

The particular details of my invention reside in a means to open the circuit to both the room thermostat RT and the hold-fire switch 28 in such a manner that the circuit can be closed again automatically instead of the operator having to remember to set the circuit again for stoker operation. I accomplish this in a very simple manner by adding to the cam 34, a lobe 40 and I include a second timer switch 42 to be opened thereby. The switch 42 is connected between the terminal 30 and a third terminal 44, the terminal 44 being connected in series with the relay coil I8. When the lobe 46 therefore registers with the leaf spring 46 of the switches 28 and 42 as in Figure 3, it separatesthe contacts of the switch 42 so that no current can flow through the coil [8.

The cam 34, as shown in Figure 4, is mounted loosely on a shaft 48 which is rotated once per hour through step-down gearing mechanism 50 from a timer motor TM. The timer-motor TM is driven continuously and .accordingly rotates the shaft 48 continuously.

The cam 34 is normally clutched to the shaft 48 by friction means in the form of a friction element .52 of the cupped spring washer variety, yet the cam 34 can be rotated relative to the shaft v48 at will. This may be accomplished manually by means of a knob 54 mounted exterior of a housing 56 :for the timer motor and the cam, and in which a small window 58 is provided. The cam 34 may then have legends on it such as 'On and Off as illustrated on the drawings, so that when it is desirable to clean the fire the cam can be rotated to the Oil position of Figure 3 and the operator will then be assured that the control circuit of the stoker cannot be energized by closure of either the room thermostat RT or the timer .switch28.

The size of the lobe 4,0 is such that it will take about 3 or 4 minutes for the lobe to pass the leaf sprin 46 and again permit the timer switch 42 to reclose so that the operator has this period of time in which to clean his fire and such period of time is ordinarily sufficient for the purpose. At the same time the operator is assured that when he leaves the stoker, the circuit for it will be reestablished automatically and it is unnecessary for him to manipulate any :control for this purpose. If, however, he wishes to observe the way the fire burns after cleaning it, he can rotate the cam manually to the position of Figure 2 wherein On shows through the window 58 and the stoker will operate the same as usual in connection with a hold-fire period.

An arrangement of the character disclosed is very simple to provide, and where a stoker timer for hold-fire purposes is already provided, it is merely necessary ,to add the switch 42 and the lobe 40 for operating it, the wire from the relay coil 18 being connected to the terminal 44 instead of to the terminal 30. By then having the cam manually rotatable to any desired position on the shaft 48, yet automatically rotatable with the shaft as it rotates when the cam is released, as-

,surance is had that the stoker circuit will not be left in an open condition so that the stoker cannot operate after cleaning the fire.

An arrangement of this kind results in a 3 or 4 minute Off period in each hour during which the room thermostat cannot cause the stoker to operate. This, however, is not objectionable as 4 the stoker will operate as soon as the off period has passed and will continue to operate until the room thermostat is satisfied, thereby delaying the starting and stopping of the room thermostat control cycle without, however, preventing the cycle from being performed for substantially the same period that it would have operated if the room thermostat had closed at an otherthan-Off position of the stoker timer. The advantages obtained by my stoker timer far overbalance this slight disadvantage with a very simple arrangement for accomplishing the shutdown period for cleaning and the operating period for observing the fire thereafter if desired.

Some changes may be made in the construction and arrangement of the parts of my device without departing from the real spirit and purpose of my invention, and it is my intention to cover by my claims any modified forms of structure or use of mechanical equivalents which may be reasonably included within their scope.

I claim-as my invention:

1. In a stoker timer, a timer motor, a cam, a friction drive between said motor and said cam,

a stoker operating circuit, a room thermostat for energizing said circuit response to temperature changes, a first timer switch for energizing said circuit periodically, said first timer switch being operated by said cam,a second timer switch operated by the same :cam for preventing energization of said stoker operating circuit by either said room thermostat .or said first timer switch during a cleaning period, said cam being fmanually adjustable independent of said timer motor to open said second timer switch and thereafter operated by said timer motor to close the second timer switch after a time period, said cam being also manually adjustable independent of said timer motor to a position for the first timer switch to energize said circuit for the purpose of observing the condition of the fire and then operable by the timer motor through said friction drive.

'2. In a stoker timer, a stoker operating circuit, a switch having threeswitch blades, two of which are normally engaged with each other and the third one of which is normally disengaged from the first one, a cam for holding said first one in the normal position, a timer motor having a friction drive with said camfor rotating it. said cam having a depression to permit the first and third leaves to close a circuit and a lobe for causing the first and second leaves to open said stokeropcrating circuit, a room thermostat, the first and second leaves and said room thermostat bein connected in series in said stoker operating circuit, and the first and third leaves being connected with the terminals of said room thermostat to close a shunt circuit around said room thermostat when it isopen.

EDWARD .B.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS

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