US2640121A - Time-pressure control - Google Patents

Description

May 26, 1953 H. 5. KING TIME-PRESSURE CONTROL 3 Sheets-Sheet 1 Filed July 29, 1950 y 26, 3 H. 5. KING 2,640,121

1 TIME-PRESSURE CONTROL Filed July 29, 1950 3 Sheets-Sheet 2 .Haroid TJ i/z (By 75% hm 9 W 17?:

May 26, 1953 H. 5. KING 2,640,121

TIME-PRESSURE CONTROL Filed July 29, 1950 3 sheets-She" Patented May 26, 1953 UNITED STATES ?ATENT OFFICE TIME-FREE S SURE CONTROL Indiana application July 29, 1950, Serial N 0. 176,649

8 Claims.

This invention relates to a control device operated by a combination of time and pressure.

One object of the invention is to provide a control of this general character particularly adapted as a defrost timer wherein refrigerat ing apparatus is shut down for defrosting at predetermined time intervals, the length of each defrosting cycle being dependent upon the amount of frost formed on an evaporator coil as reflected in the pressure of the low side line of the refrigeration system.

Another object of the invention is to provide a time-pressure control in which a timecloclr initiates an operation and pressure deteri'nines the length of the operation thus resulting in prodetermined periodic operations terminated in accordance with conditions other than time.

In many refrigeration systems such as those for self-service cases, reach-in boxes, meat storage coolers, dispensing equipment and the like, it is desirable to have predetermined defrosting intervals but it is undesirable to have these intervals of predetermined length as when the frost is light the length should be shortened for highest efficiency and when the frost is heavy it should be lengthened accordingly. Therefore, it is a further object of the present invention to operate a defroster control at predetermined intervals but with cycle lengths varying in accordance with frosting conditions.

A further and more specific object is to provide a control switch which is connected in the circuit with refrigerating mechanism to open the circuit and thus stop the operation of the refrigerant compressor to permit defrosting of the evaporator, and to provide defrost cycle terminating means responsive to completion of the defrosting as by a pressure responsive device responding to the back pressure in the low side of the refrigeration system corresponding to a frost melted condition of the evaporator.

More specifically, it is an additional object of my present invention to provide a switch such as one of the snap acting type having a relatively wide differential, and time and pressure operating mechanisms therefor wherein the pressure operating mechanism. when responding to any pressure below the cut-in pressure of the refrigeration system conditions the switch for the requirement of a minimum of energy to move it to the cut-out position, the time control mechanism being operable to finish the movement thereof to the cut-out position, and the increase in pressure of the low-side of the system (corresponding to a frost-melted condition of 2 the evaporator) returning the switch to the cut in position so that the refrigeration mech anism is thereafter under control of the usual automatic control switch provided therefor.

With these and other objects in view, my invention consists in the construction, arrange-- ment and combination of the various parts of my time-pressure control, whereby the objects contemplated are attained, as hereinafter more fully set forth, pointed out in my claims and i1- lustrated in the accompanying drawings, wherein:

Figure l is a front elevation of a time-pressure control embodying my present invention.

Figure 2 is a side elevation thereof with a bellow housing of the control shown in section.

Figure 3 is a sectional view on the lines 3--3 of Figure 1.

Figure 4 is an enlarged view similar to a portion of Figure l and showing a timing dial with portions thereof broken away to illustrate details of operation.

Figure 5 is a diagrammatic view of the essential operating parts of the control showing them in a position at the start of a timing operation of the control. Figure 6 is a similar diagrammatic view showing the position of the parts at the time they are about to operate for accomplishing completion of the timing operation.

Figure 7 is a similar diagrammatic view showing the completion of the timing operation such as the start of a defrost operation of a refrigeration system; and

Figure 8 is a similar diagrammatic view showing a resetting operation such as a defrost op- 'eration terminated by a build-up of pressure in the low side of the refrigeration system.

On the accompanying drawings I have used the reference numeral It to indicate a mounting plate, which plate has lower and upper walls l2 and [4. A vertical metal panel is is mounted between the walls l2 and I4 and a vertical panel 13 of insulation is spaced in front of it. The parts thus far described and the mechanism supported thereby are finally enclosed in a suitable cover which has been omitted from the drawings in order to show details.

A stationary shaft 2% is provided on which a timing gear rotates, preferably once each twentyfour hours. Through suitable step-down gearing shown by dot-and-dash lines in Figure 1, this shaft is rotated from an electric motor or time clock 22 and the rotation thereof is continuous. A knob 24 rotating once each hour is provided on the one-each-hour shaft of the motor 22 and is associated with the gearing for the purpose of setting the clock so that the hour shown on the timing dial 25 thereof may correspond to the time of day at the time the clock is set. An index 28 is provided for this purpose and in Figures 1 and 4 the timing dial is shown set at My control includes a switch consisting of a stationary contact 30 and a movable contact 32.

For actuating the movable contact, a spring expansible toggle 34 is provided interposed between the end of a toggle blade 35 for the switch blade on which the contact 32 is mounted and an actuating blade 36. The actuating blade 35 is bent as shown particularly in Figure 8 so that its normal tendency is to retain the switch closed as in this figure.

The switch 30-32 is preferably connected in series with the usual automatic control switch 38 of a refrigeration system as shown in Figure 5 and with a refrigerant compressor motor 40 which are shown diagrammatically in Figure 5. The motor 40 runs the refrigerant compressor 42 and the refrigerant circuit comprises suitable high side and low side piping 44 and 46, a condenser 48, and an evaporator 50. The switch 38 is of the pressure operated type having a pressure connection 52 with the low side 46 of the refrigerant system. pressure increase and opens it on pressure decrease so as to maintain the desired temperature in the refrigerated space as reflected in the pressure in the low side 46.

The current supply wires are indicated at 54 and 58 connected with the switch 38 and the motor 40. Other wires 58 and 60 connect the switch 30-32 with the switch 38 and the motor 43 so that a series circuit is provided whereby as long as the contacts 30 and 32 are closed, the g for keeping it shut down if the switch 38 is open until the termination of the defrosting period in response to pressure as will also hereinafter appear.

For actuating the switch 30-32, I provide two distinct mechanisms. The first one pressure operated and the second is time operated. The presure operated mechanism comprises a bellows housing 62 having a bellows 64 therein which is responsive to the low-side pressure through a conduit connection 66 with the low side line of the refrigeration system. An actuating link 58 is actuated by the bellows 64 and carries a combined pivot and stop pin I0.

Whenever the pressure in the line 46 is anywhere below the cut-in pressure of the switch 38, the stop pin I0 engages the edge of a stop opening I2 in a stationary bracket 14 as shown in Figure 5. Pivoted on the pin 10 is one arm of a bell crank it which bell crank is pivoted at E8 to the bracket I4. A range spring 80 is connected with the bell crank I6 and by means of an adjusting screw 82 may be adjusted to predetermine the pressure at which the stop pin I0 will engage the edge of the opening 12 as illustrated in Figures 2, 5, 6 and '7.

lhe bell crank 18 carries an insulating element 84 which, when the stop pin I0 is in the position of Figure 5 engages the actuating blade 36 of the switch 30-32 and propels it from its normal- It closes the circuit upon ly biased position of Figure 8 to the position of Figure 5 where the toggle 34 is moved nearly to its dead-center position, this being the same position as illustrated also in Figure 3. An adjustment screw TI is provided between the two arms of the bell crank I6 and is adjusted so that at no time can the bellows 64 respond to a low pressure and move the toggle 34 beyond dead-center. When the pin I0 engages the edge of the opening 12, the near-dead-center position of the toggle 34 is had by the proper adjustment of the screw I1.

When the switch 30-32 is in the position illustrated in Figure 5, it is obvious that very little energy is needed to move it to the open position of Figure 7. For completing the opening movement, I provide a second bell crank 85 pivoted at 88 to the bracket 80. The bell crank has a weight 92 thereon and carries an insulating element 84. At its opposite end it has a flange adapted to be engaged by a timing pin 98. Several of these timing pins are provided and the timing dial 20 is provided with openings 2? at one hour intervals to receive them selectively, the pins being passed through the opening 21 and through threaded openings 29 of the timing gear I00 which rotates on the shaft 20.

As shown in Figure 4, the left hand timing pin may rotate as to the position indicated at 98a for engaging the flange 93 of the bell crank 86 and swinging it about its pivot 88 with the upper end moving from the solid line position shown in Figure 4 to the dotted position indicated as 8611. The timing pin is then at the dotted position indicated at 98b wherein, due to the timing pins traveling in a circle and the flange 96 traveling in one plane, it disengages the flange 96 to permit the bell crank 86 to swing back to a third position indicated at 85b. Preferably the timing between the positions 980; and 98b is about two and one-half hours so that as many as eight periodic defrostings in twenty four hours can be had by spacing the timing pins 98 at three hour intervals, six hour intervals however being illustrated in Figure 4. Thus during the two and onehalf hour period, the comparatively weak energy of the clock motor 22 can be accumulated in a spring that eventually operates the bell crank 86 and which spring is shown at I02 in Figure 5.

The spring I02 is anchored as indicated at I04 to the panel I0 and in the normal position of Figure 5 lies fiat against the horizontal weighted arm of the bell crank 86. This position is illustrated by the timing pin 98a in Figure 4 which position is the same as shown in Figures 2 and 5. At the end of the two and one-half hour period just referred to, the parts are in the position shown in Figure 6 wherein the timing pin at position 98b in Figure 4 is just releasing the bell crank 85. The energy of the timer has been stored in the spring I02 and contact is had between the bell crank and the spring at the point indicated a in Figure 6 so that a relatively stiff minor portion of the spring I02 is in effect for returning the bell crank 80 from the Figure 6 position to the Figure 7 position.

After the timing pin at 88a in Figure 4 clears the flange 96, the spring I82 will throw the bell crank 86 to the position of Figure '7 which causes the insulating element 94 of the bell crank 86 to move the actuating blade 35 of the switch 30-32 to the position of Figure '7 which is the rest of the way to the cut-out position toward which it has partially been moved in Figure 5 by the low pressure acting on the bellows E4, or more specifically the expansion of a spring 65 in the bellows for propelling the link '58 toward the right when the pressure in the bellows housing 52 reduces.

The momentum of the weight 92 aids in the throwing of the switch 3932 to the oif position in Figure 7 and the final movement is accomplished with the end 22 of the spring M2 contacting the bell crank 85 so that since all the spring )2 is now interposed between the pol crank and the anchored end I04, it takes but I energy to move this hell crank back to the position oi Figure 5.

From the foregoing description it will be obvious that I have provided a control device in which a time clock initiates a defrost cycle by opening the switch to the position of Figure '7, thus opening the circuit for the refrigerating mechanism shown diagrammatically in Figure 5-. The timing mechanism is not utilized for reclosing the switch but rather the build up of pres sure in the low side 46 is utilized for this purpose by having the bellows G l responsive thereto.

When this pressure builds up to a value corresponding to slightly above freezing temperature at the evaporator 5d, the bellows will have been compressed from the position of Figure '7 to the position of Figure 8 so that the insulating lement 84 moves down far enough that. the actuating blade 36 of the switch 3ll32 will return as shown in Figure 8 to permit the switch it-32 to reclose. The switch its-eh" does not l'r e a great deal of energy but its energy is suhicient to move the bell crank 86 from the position of Figure 7 to the position of Figure 8 so as to permit reclosure of the switch in this manner in response to the build-up of pressure in the conduit to. Thus the defrosting cycle is initiated by time control mechanism and terminated by pressure constance, the spring I02 is able to overcome the return bias of the switch whereas in the other instance the return bias of the switch is able to overcome the tension of the spring to produce the desired operation.

This arrangement produces a balance between switch-on and switch-oil positions which permits the defrosting operation to end immediately if conditions are suitable. The suitable conditions just referred to are those in which the frost has accumulated but lightly in which case it would take but a few seconds for the pressure to rise sufficiently in the low side 46 to move the parts to the position of Figure 8 for terminating the defrost cycle.

Some changes may be made in the construction and arrangement of the parts of my timepressure control 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 be reasonably included within their scope.

I claim as my invention:

1. In a time-pressure control of the character disclosed, a control device having an operative position, pressure operated means operable upon pressure reduction to move said control device away from said operative position and toward but not to, inoperative position whereby to minimize the energy required to finish the movement thereof to inoperative position, stop means to render said pressure operated means incapable of finishing such movement, a timer controlled element operable to finish such movement by means of energy supplied by the timer, said pressure operated means being operable upon pressure increase to a predetermined value to effect movement oi the control device again to operative position.

In a time-pressure control of the character disclosed, a control device biased to an operative position, pressure operated means having limited movement for moving said control device toward but not completely to inoperative position whereby to minimize the energy required to finish the movement thereof to inoperative position at one limit of the movement of said pressure operated means, a timer controlled element operable to finish such movement by means of energy supplied by the timer, said pressure operated means being thereafter operable to move said control device again to operative position before said pressure operated means reaches its other limit of movement.

3. A time-pressure control device comprising a switch biased to closed position, pressureoperated means for moving said switch to adjacent open position only, a time actuated element ior moving said switch to open position, a spring for actuating said time actuated element in one direction, time-operated means for actuating said element in the opposite direction, said elemeni when operated in said opposite direction compressing said spring whereby upon release by the time operated mechanism said spring will throw said element to a position for opening said switch, said pressure-operated means being thereafter movable in response to pressure increase to a position permitting said switch to reclose.

i. A time-pressure control device comprising a switch biased to closed position, pressure-operated means for moving said switch to adjacent open position only, a time actuated element for moving said switch to open position, a spring for actuating said time actuated element in one direction, time-operated means for actuating said element in the opposite direction, said element when operated in said opposite direction compressing said spring wheroby upon release by the time operated mechanism said spring will throw said element to a position for opening said switch, a weight on said time actuated element to aid said spring in the switch opening operation, said pressure operated means being thereafter movable in response to pressure increase to a position permitting said switch to reclose.

5. In a time-pressure control device, a defrost switch biased to closed position, low side pressure-operated means for moving said switch to adjacent open position, a time actuated element for moving said switch to open position, a spring for actuating said time actuated element in one direction, and time-operated means for actuating said element slowly in the opposite direction to store energy in said spring whereby upon release by the time operated mechanism said spring will throw said element to a position for opening said switch, said pressure operated means being thereafter movable in response to defrost temperature to a position permitting said switch to reclose.

6. A time-pressure control device for a refrigeration system comprising a switch in the electric circuit for the refrigerant compressor and biased to closed position, pressure-operated means responding to pressure in the low side of the system for moving said switch to adjacent open position, a time-actuated element for moving said switch to open position, a spring for quickly actuatin said time actuated element in one direction, time-operated means for slowly actuating said element in the opposite direction, said element when operated in said opposite direction compressing a relatively short length of said spring whereby upon release by the timeoperated mechanism said spring will throw said element to a position for opening said switch,

said pressure operated means being thereafter movable in response to defrost temperature to a position permitting said switch to reclose, said switch in reclosing moving said element against the bias of substantially the full length of said spring for conditioning the parts for recycling I.

of the control.

7. In a time-pressure control device, a control element biased to an operative position, pressure operated means for moving said control element toward inoperative position but stopping short of said inoperative position whereby to minimize the energy required to finish the movement thereof to said inoperative position, said pressure operated means being incapable of finishing such movement, a timer controlled element operable with timer energy to finish such movement, said pressure operated means being thereafter operable to move the control element again to the operative position immediately if the pressure operated means is responding to the necessary pressure for moving said control element toward the said inoperative position.

8. In a time-pressure control device, a defrost switch biased to closed position, low side pressure-operated means for moving said switch to adjacent open position, a time actuated element for moving said switch to open position, a spring for actuating said time actuated element in one direction, and time operated means for actuating said element slowly in the opposite direction to store energy in said spring whereby upon release by said time operated means said spring will throw said element to a position for opening said switch, said pressure operated means being thereafter movable in response to defrost temperature to a position permitting said switch to be closed immediately if said low side pressure is high enough to move said switch to said adjacent open position.

HAROLD S. KING.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,114,766 Heitman Apr, 19, 1938 2,162,709 Gill, Jr June 20, 1939

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