US2189663A - Refrigerating apparatus - Google Patents

Description

Feb. 6, 1940.

A. o. GROOMS 2,189,663

REFRIGERATING APPARATUS Filed Oct. 30, 1936 3 Sheets-Sheet 1 INVENTOR.

ATTORNEYS Feb. 6, 1940. A. 'o. GROOMS REFRIGERATING APPARATUS 5 Shets-Sheet 2 Filed Oct. 30, 1936 INVENTOR.

gadwo/ ATTORNEYS Feb. 6, 1940; O GROOMS v 2,189,663

REFRIGERATING APPARATUS Filed Oct. 50, 1936 3 Sheets-Sheet 3 QQZWITO BY I 10 20 50 40 z 5 2,4 44 4W -24 INVENTOR.

TEMPERATURE "F ATTORNEYS Patented Feb. 6, 1940 UNITED STATES PATENT OFFICE REFRIGERATING APPARATUS poration of Delaware Application October 30, 1936, Serial No. 108,377

12 Claims.

This invention relates to refrigerating apparatus and more particularly to control means therefor.

Heretofore, low differential switches for refrigerating systems and temperature controls mainly have had bimetal as the actuating element. Bimetal switches, because of their low contact pressures, can ordinarily carry only a small amount of current at a low voltage. This necessitates the use of a relay in order to control heavier currents.

In refrigerating systems and other temperature controls, it is often desirable to have a more simple arrangement wherein the relay is eliminated and it is usually desired to employ a switch operated by gas pressure. Considerable difficulties are encountered in attempting to make a low differential switch operated by gas pressure. In the first place, the metal bellows, which are ordinarily used in such switches, may in the present state of the art, operate only in a compressed condition to avoid bellows failure. When operating under such conditions the natural spring of the metal bellows tends: to increase the minimum differential. Also, because it is usually required that the switch be made small, the spring which opposes the expansion of the bellows must be made rather short and, therefore, have a very high rate. 'This high ratev also tends to considerably increase the minimum differential.

It is an object of my invention to provide a relatively small switch actuated by gas pressure which switch has a small differential and has a relatively high current carrying capacity.

It is another object of my invention to provide a control having means to counteract in whole or in part the tendency of the bellows and the springs to increase the differential of the control.

It is also an object to provide a control means with an additional means for reducing the minimum differential of'the switch.

It is a further object of my invention to provide a single means for snufling out the are at two sets of contacts in a switch.

It is still another object of my invention to provide .a refrigerator control switch having an improved structure and an improved mechanism panying drawings, wherein a preferred form of the present invention is clearly shown.

In the drawings:

Fig. 1 is a view partly in section of one form of a refrigerator control switch embodying my invention;

Fig. 2 is a section taken along the line 22 of Fig. 1;

Fig. 3 is a section taken along the line 3-3 of Fig. 1; and 10 Fig. 4 is a chart showing a diagram of forces in terms of the movement of the bellows lever as well as a temperature pressure scale therefor. Briefly, I have shown a switch provided with a bellows, a bellows follower lever and a double toggle snap acting mechanism operatively connecting the main switch contacts with the bellows follower lever. A rather short, stiff main spring opposes the expansion of the bellows and maintains the bellows under compression within the range of movement of the bellows and bellows follower lever. A set of manually controllable overload contacts are also provided and a combined electromagnetic blow-out coil and thermal overload heater are provided for snufilng out the are at both sets of contacts and for providing the thermal overload of the solder pot type. The thermal overload is of the trip-free type.

The spring effect of the bellows and the high rate of the main spring tend to make the differ-- ential of the switch rather high, for example, about 13 F. This is satisfactory for household refrigerating systems where the bellows is operated according to evaporator temperature. However, if the switch is to be controlled by air temperature, this temperature differential must be reduced. In order to reduce this temperature differential, I connect a tension spring to the bellows follower lever which extends diagonally slightly below the pivot point of the main lever so that it exerts its greatest force when the bellows is collapsed and a constantly decreasing force as the bellows expands. 'I'his, therefore, has the effect of a spring with a negative rate and operates to reduce the positive rate of the main spring and the spring efiect of the bellows. As shown in Fig. 4, this bellows cancel spring or extra toggle type spring can be so set that it is substantially equal and opposite to the inherent spring of the bellows,-but if desired, this angularity and characteristic of its spring may be changed so as to have a greater effect sufficient to reduce the effect of the high rate of the .main spring. Through this means the temperature differential of the switch may be reduced'without changing its size or the limits of movement of the bellows and bellows follower lever.

Referring now to the drawings and more particularly to Fig. 1, there is shown one form of refrigerator control switch embodying my invention. This switch is provided with a case 28 of a molded insulating material such as hard rubber or a phenolic condensation product. This case is provided with a slot 22 which receives the neck of a metal bellows 24. This neck is lodged within the slot 22 of the casing and fastened by a thin nut 28. The interior of the bellows 24 is connected by tubing 28 to the interior of a volatile liquid charged thermostat bulb not shown. A yoke 38 has an aperture which surrounds the neck of the bellows 24 and has a tongue 32 which is turned down in the slot 22 which receives the neck of the bellows. One side of the yoke 38, designated by the reference char acter 34, receives a pivot pin 38 to which" is connected one end of the bellows follower lever 38.

The upper end of the other side of the yoke 38 is notched as indicated by the reference character 48 so that it may be received by the sides of an opening 42 provided in the bellows follower lever 38. This aperture 42 is elongated in the direction transverse to the notched portion 48 so that the notched portion 48 may pass through the aperture 42 when the bellows follower lever 38 is in aposition transverse to its proper position. This, therefore, acts somewhat similarly .to a bayonet slot arrangement. The notched lower 38 and thereby limit the expansion of the bellows 24.

The free end of the bellows follower lever is provided with a pair of notches 44 which receive the chisel-shaped ends of a secondary snap acting lever 46. The secondary lever 48 is generally U-shaped and on its opposite end is provided with a slot which receives a T'-shaped member 41 having an aperture therein which receives one end of the tension coil spring 48. The opposite end of this tension coil spring is hooked over a turned up car 58 provided upon an L- shaped contact carrying lever 52 which is pivoted upon a pivot pin 54 which in turn is supported by a bracket fastened to and extending from the adjacent wall of the switch case 28. This contact lever 52 is provided with portions on either side of the secondary lever 48 which serve as stops to limit the movement of the secondary lever 48.

Part of the contact lever is formed of heavy sheet brass while a second part 58 which is riveted to the brass part is made up of a stiff molded insulating material which preferably contains fabric. The switch contacts 58 are located at the end of. the portion 58 and are riveted to H clip 88 which extends around the lower end of the portion 58 and has a tongue extending into an aperture provided in the portion 58 to retain the clip 88. The differential of the snap acting mechanism is determined by the angularity of the contact lever 52 in open and closed position. The angularity of the contact carrying lever 5.2 is limited by the fixed contact which is carried by the contact post 82 while the open position of the contact carrying lever 52 is limited by a differential screw 84 which is held within a threaded aperture in the casing and has a pin extending into contact with a portion of the contact carrying lever 52 to limit the opening movement of this lever. v

In order to place the bellows 24 under compression and in order to balance the gas pressure within the bellows, I provide a tension coil spring 88 which is connected at one end to the bellows follower lever 38 and its other end to a U-shaped nut I8 which is threaded upon an adjusting screw 12 rotatably mounted at both ends within opposite walls of the casing 28. The one end portion of this screw extends through the casing and is provided on the outside with a temperature regulating knob I4. This tempera- I ture regulating knob 14 may be turned to increase or decrease the tension upon the spring 88 and so will increase or decrease the gas pressure required within the bellows 24 to move the switch contacts to open and closed position.

This switch mechanism is also provided with a toggle snap acting single cycle loading device. This includes a finger manipulator I8 which is pivoted to the case 28 upon a pivot pin I8. This finger manipulator is provided with a notch 88 which receives a chisel-shaped end of a link 82 which has its other end received and slidable within a pair of apertures provided in a bracket 84 fastened to the case 28. This bracket is provided with a rounded protrusion against which rests the spring retainer of a small compression type coil spring 88 which is threaded upon a screw 88 having one reduced end portion passing through an aperture in the bracket 84 while the other end portion is provided with a nut 88 and a kerf on the end of the screw.

The link 82 is provided with a slot which receives the spring, the nut and the screw. The

kerf end of the screw engages the end of the slot to hold and to prevent the rotation of the screw. A link 92 is connected to a portion of the link 82 and extends downwardly therefrom. This downwardly extending link 82 has a shoulder and a narrow tongue extending downwardly through an aperture in the bellows follower lever 38. When the finger manipulator I8 is turned in a clockwise direction about its pivot 18, the link 82 is moved downwardly so that its shoulder comes into engagement with the flat portion of the bellows follower lever 38 and at the same time the link 82 is pushed across the center line between the pivot pin I8 and the hump on the bracket 84 so that the spring 88 will tend to place an additional force by the throwing of the toggle linkage and the link 82 upon the bellows follower lever. This places an additional load upon the bellows 24 and requires a higher pressure and temperature before the switch may be moved to closed circuit position. When this higher pressure and temperature is attained, the bellows follower lever 38 through the link 82 will push the link 82 across its dead center position to the position shown in Fig. 1 where it is inactive. This is employed in household refrigerators to provide a manually initiated automatically reset defrosting cycle for the purpose of providing a cycle which will remove any frost which may collect on the evaporator.

I have also provided a manual on and off snap acting switch which is actuated by the finger manipulator I82 pivoted upon the pin I84 embedded in the casing 28. This finger manipulator I82 has a metal extension I88 which holds one end of the compression toggle spring I88 provided-with pointed spring retainers at each end,

one of which engages one arm of a contact car-- rying lever IIO pivoted to the casing upon a pivot pin I I2. The other arm of this lever H0 has'an extension II4 of an insulating material containing fabric and hard rubber or a phenolic condensation product. The extreme end of this portion H4 is provided with a clip H6 having a tongue engaging an aperture in the portion II4 for retaining the clip. This clip surrounds the lower end of the member H4 and is provided with a switch contact II 8 which is adapted to cooperate with a stationary switch contact I20 mounted upon a stud I22 which is riveted to a movable insulating wall section I24.

This mechanism provides a snap acting manual switch. It is, however, also used as a thermal overload mechanism and. has a means for resetting the thermal overload mechanism. In order to do this the casing is provided with a hollow boss i265 extending from the bottom wall in Fig. l which receives the shaft H20 of the ratchet wheel it. This shaft I28 is received within a bushing Hi2 threaded into the hollow boss H20 and fastened to the shaft M8 by a low melting solder. Threaded onto this threaded bushing 632 is a soft iron core i341 upon which is mounted a coil of wire i230 which with the core serves as an electromagnet as well as a thermal overload heater for heating the solder which holds the shaft H28 or" the ratchet wheel. This coil I30 is connected by the conductors I30 and I40 in series with the switch contacts 62, 50, H8 and I20. This electromagnet coil is wound tightly with several layers of wire instead of very loosely as heretofore so that it will not be influenced to any great degree by the temperature of the place wherein the switch is located.

Recently, it has been customary to locate the switch upon the evaporator of a household refrigerator and under such conditions the tern perature of the switch may fluctuate considerably. The tight winding prevents this fluctuation of temperature from materially varying the operation of the thermal overload. In addition, this electromagnet sets up a magnetic field which embraces both sets of switch contacts and also furnishes a small supply of heat which maintains the switch at a temperature above the temperature of the atmosphere within the refrigerator so that there will be little or no condensation of moisture or deposit of frost upon the parts of the switch.

The ratchet wheel I30 holds a spring tongue I42 between a pair of teeth. This spring tongue is also fastened to a slidable plate I44 which slides with the arms I 46 and I48 of a U-shaped bracket which is fastened to the bottom wall of the case 20. This slide plate also has a hooked end portion I50 which is adapted to engage a portion of the arm I I4 when the slide I44 is released by the ratchet wheel. When this projection I50 engages the arm II4, it pivots the arm II4 as well as the arm IIO about their pivot II 2 to open the contacts II 8 and I20. At the same time it throws the toggle spring I08 across its dead center position so that the finger manipulator I02 is moved to its off position.

The slide plate I44 is provided with an arm I 54 which is pivoted by the pin I56 to the slide plate. This arm has a curved end portion with a notch that is adapted to be engaged by a depending tongue I58 extending from the metal arm I06 attached to the finger manipulator I02. The arm I54 is pulled to the left as shown in Fig. l by a tension coil spring I62 connected at the other end to the arm I48 while a second spring I84 connects the arm I54 to a remote portion of the arm I48. Thus, when the ratchet wheel I30 releases the slide plate, the slide plate I44 and the arm I54 move to the left in Fig. 1 under the motive power of the spring I62 which is thereby reduced in tension while the spring I64 has its tension increased and thereby raises the arm E54 sufliciently so that it will be engaged by the arm I58 upon the finger manipulator I02.

Thus, when the finger manipulator I02 is moved from off to "on position, in this circumstance, the arm I58 will engage the notched end of the arm I 5 3. This will move the arm I54 and the slidable plate 944 to the right as located in Fig. l and at the same time will cause a portion of the face of the arm l5fi to be held against the side of the adjacent portion of the contact carrying lever 52 so that the contacts 50 will be held in the open position while the contacts H0 and H0 are being closed and the spring tongue M2 is moved into engagement with the ratchet wheel. During this time the finger manipulator throws the toggle spring i 00 across the dead center position to move the overload contacts into closed position. The contacts 50, however, will remain in the open position until the finger manipulator is released, at which time the arm lt l will also be released by the arm 950 of the finger manipulator 002 so that it will be impossible to hold the contacts closed by the use of the finger manipulator i 02.

This will prevent the refrigerating system from being forcibly operated under overload conditions when the ratchet wheel has released the slide plate I44.

In Fig. 4 I have provided a chart or graph in which. the movement of the bellows follower lever at the bellows point is plotted along the horizontal scale and the effective pressure in pounds at the bellows point is plotted in the vertical direction. The bellows may be assumed as havingan effective area of about one square inch so that this vertical scale will also represent the gas pressure within the bellows 24. Under ordinary circumstances the main spring 08 and the diifenential screw 64 are set so that the switch will be closed when the bellows is compressed and the bellows follower lever is moved upwardly, with reference to Fig. 1, from its extreme lower position a distance of .046 inch. The switch will open when the bellows and bellows follower lever move downwardly about .025 of an inch to a position of .021 inch.

In Fig. 4, the line marked Bellows indicates the inherent spring force of the bellows which is plotted as being negative pressure since it tends to push the bellows follower lever 38 downwardly. The two lines marked Toggle indicate the force of the toggle spring during the movement of the bellows and bellows follower lever. This force changes from positive to negative when the switch cuts on or closes and changes from negative to positive when the switch cuts out or opens. Hie force provided by the main spring is plotted by the line which is designated as Main spring with cancel spring. This is a positive force which increases with the expansion of the bellows and movement of the bellows follower lever. This main spring is required to be strong enough to oppose the force of the bellows plus the force of the gas pressure within the bellows plus the force of the toggle spring. However, in order to do this, the main spring would have to be adjusted to the strength or pull indicated by the dotted line upon the chart and marked Main spring without cancel spring". As shown in the chart, it would require about 3.6 lbs. or 3.7 lbs. gas pressure within the bellows to open the switch.

In the lower left hand corner of the chart in Fig. 4 is a curved line which designates the pressure temperature curve of sulphur dioxide, which for the purposes of illustration, is the gas used in the bellows and thermostat bulb. However, other gases such as methyl or ethyl chloride or difluorodichloromethane may be used if desired. Beneath this curved line is a temperature scale. The point 3.6 or 3.7 upon the pressure temperature curve of sulphur dioxide represents upon the temperature scale about 23 F. When the switch moves to cut-on position, the main spring is stretched further and then has an effective pull of 12 lbs. Under ordinary circumstances, this plus the force of the toggle spring must be balanced by the force of the bellows plus the gas pressurewithin the bellows, in order to make the switch close. However, the force of the bellows decreases as shown by the chart so that a greatly increased gas pressure of lbs. is required to close the switch. This corresponds to a temperature of about 36 F. or 37 F. which makes a switch differential of about 13 or 14F.

The main spring necessarily has a high rate because of the small space provided. In order to provide an effective temperature adjustment by the knob 14, it is diflicult from the practical standpoint to materially reduce the rate of the main spring within a switch structure of such a small size. This switch is about four inches long, two inches wide and one and one-half inches deep. In Figs. 1, 2 and 3, each dimension is doubled in size. In order to reduce, the differential of the switch, it is, therefore, necessary to find some means for reducing the rate of either the bellows, the main spring or both. However, it is not possible to conveniently reduce the rate of the main spring or of the bellows.

I, however, have found a way to obtain the same effect. I do this by providing a tension spring I10 which extends into a slot I12 provided in the bellows follower lever 30 and is hooked to an aperture located at the closed end of the slot. The other end of this tension coil spring is hooked in the eye of a threaded pin I14 which is threaded within a nut I16 mounted upon the opposite side of an L-shaped bracket I18 which in turn is riveted to a projection of the arm 34. It should be noted that the center line of this spring extends above the pivot point of the main lever 38 and the spring extends from the main lever 38 at a slight angle thereto. Thus, when the bellows 24 are collapsed tothe cut-oft position, the spring 110 exerts its maximum force aiding the main spring 60. At this time, the bellows 24 also exerts its maximum inherent spring force. As the I bellows expands, the inherent spring force of the I bellows weakens, as shown in the chart, while at the same time the spring I10 provides an effective force substantially equal and opposite the inherent spring force of the bellows.

In Fig. l I have located the screw I14 and made a spring I10 of such a rate so that it is substantially equal and opposite to the inherent spring force of the bellows through its range of movement between the cut-off and cut-on points. In fact, it is substantially equal and opposite throughout the movement of the bellows. I, therefore, call this spring a bellows cancel spring because it cancels in effect the inherent spring force of the bellows. By adding this bellows cancel spring, it is possible to reduce the force of the main spring. It will be seen that when n cancel spring is used, it is necessary to provide a main spring which has eight pounds of force at the cut-off point and twelve pounds force at the cut-on point. By employing the bellows cancel spring I10 it is possible to reduce the force of the main spring 68 at the cut-off point to 4.6 lbs. while this same spring would have a force of only about 8.6 lbs. at the cut-on point.

The force of the bellows plus the force of the gas pressure must be suiiicient to equal the force of the toggle plus the force of the bellows cancel spring, plus the force of the main spring when a. cancel spring is used. When no cancel spring is used, the bellows force plus the gas pressure must equal the force of the toggle plus the main spring. However, since the bellows cancel spring has a negative rate; that is, its force is reduced as the bellows expands, it reduces the force normally required of the bellows and gas pressure to move the switch to cut-on position by the amount that the force of the bellows cancel spring is reduced. Since the bellows cancel spring has reduced the force about 1.2 or 1.3 lbs., a lesser gas pressure is required. Thus, the chart shows that at the cut-on point, the gas pressure required when a cancel spring is used is about 8.8 lbs. This corresponds to about 33 F. so that the differential of the switch by the use of this cancel spring has been reduced 3. v

However, since the main spring need not supply so great an amount of force, its rate may also be reduced slightly if desired. Furthermore, the bellows cancel spring may be located at other angles and may have a. greater force so that it would provide a more variable negative rate so as to not only cancel the inherent spring force of the bellow but also to cancel a portion of the force of the main spring so that in effect it would reduce the rate of the main spring. Thus, by employing this bellows cancel spring, I am able to considerably lower the diflferential of the switch without changing the relationship, sizeand force of any of the elements of the switch, but merely by the addition of the bellows cancel spring which may not only be used to cancel out the inherent spring force of the bellows, but also to reduce the effective rate of the main spring and thus to considerably reduce the difierential of the switch.

While'the form of embodiment of the invention as herein disclosed, constitutes. a preferred form, it is to be understood that other forms might be adopted, all coming within the "scope of the claims which follow.

What is claimed is as follows;

1. A control means including a pressure operated diaphragm means having an inherent natural resilient resistance to movement from a neutral position, a means to be operated by said diaphragm means, and cancelling means providing a force substantially equal and opposite to said inherent natural resilient resistance of diaphragm means, and spring means providing a force substantially equal and oppositeto said inherent natural resilient resistance of the diaphragm means for substantially cancelling said resilient resistance. I

3. A control means including a pressure op- 2,1s9,ees

erated diaphragm means having an inherent natural resilient resistance to movement from a neutral position, a means to be operated by said diaphragm means, and resilient over-center means providing a force substantially equal and opposite to said inherent natural resilient re sistance of the diaphragm means for substantially cancelling said resilient resistance.

4. A control means including a pressure operated diaphragm means having an inherent natural resilient resistance to movement from a neutral position, a means to be operated by said diaphragm means, a snap acting means connecting said means to be operated and said diaphragm means, and means acting upon said diaphragm means providing a force substantially equal and opposite to said inherent natural resistance of said diaphragm means for cancelling said natural resistance.

5. A control means including a pressure operated diaphragm means, a switch means operated by said diaphragm means, means for limiting the expansion of the diaphragm means, said diaphragm means having an inherent spring force decreasing with expansion of the diaphragm means in a direction aiding the expansion of the diaphragm means, and a spring means providing throughout the limited expansion of the diaphragm means a decreasing positive resistance with the expansion of the diaphragm means opposing theexpansion of the diaphragm means.

6. A control means including apressure operated diaphragm means, aswitch means operated by said diaphragm means, means for limiting the expansion of the diaphragm means, said diaphragm means having an inherent spring force decreasing with expansion of the diaphragm means in a direction aiding the expansion of the diaphragm means, a yielding means providing an increasing resistance with the expansion of the diaphragm means opposing the expansion of the diaphragm means, and a yielding means providing throughout the limited expansion of the diaphragm means a positive decreasing resistance with the expansion of the diaphragm means opposing the expansion of the iting the expansion of the diaphragm means,

and a yielding means providing throughout the limited movement of the diaphragm means a decreasing positive resistance with the expansion of the diaphragm means opposing the expansion of the diaphragm means.

8. A control means including a pressure operated diaphragm means, a switch means operated by said diaphragm means, means for limiting the expansion of the diaphragm means, and a yielding spring means providing a decreasing positive resistance to the expansion of the diaphragm means opposing the expansion of the diaphragm means throughout the limited expansion of the diaphragm means.

9. A control means including a pressure operated diaphragm means, a switch means opened and closed at certain positions of movement of the diaphragm means, and a yielding means providing a decreasing resistance with the expansion of said diaphragm means from one of said certain positions to another, said yielding means providing a positive resistance to the expansion of said diaphragm means between said positions.

10. A control means including a set of switch contacts, a diaphragm means for operating said contacts, a second set of switch contacts located adjacent said first set of contacts, and magnetic means located between said sets of contacts for creating a magnetic field enveloping both of said sets of contacts.

11. A control means including a set of switch contacts, a diaphragm means for operating said contacts, a second set of switch contacts located adjacent said first set of contacts, and electromagnetic means located between said sets of contacts and energized by electric energy fiowing through one of said sets of contacts for creating a magnetic field enveloping both of said sets of contacts.

e 12. A refrigerator control to be mounted within the compartment to be cooled of a refrigerator cabinet, said control including a casing containing a diaphragm means, a switch mechanism operated by the diaphragm means, an electric circuit controlled by said switch means, and means for preventing corrosion of the mechanism in said casing including an electric heater electrically connected to said electric circuit and controlled by said switch mechanism for heating the refrigerator control.

ALBERT O. -GROOMS.

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