US2377503A - Refrigeration control - Google Patents

Description

June 5, 1945. c. G. KRONMILLER 2,377,503

REFRIGERATION CONTROL I Filed Dec. 20, 1940 2 Sheets-Sheet 2 Fig.4:

. INVENTOR darl G. Kronmillzr ATTORNEY Patented June 5, 1945 REFRIGERATION CONTROL Carl G. Kronmiller, Minneapolis, Minn., assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application December 20, 1940, Serial No. 371,001

26 Claims.

This invention relates to a control mechanism for refrigerating apparatus, particularly apparatus of the type employing a motor'driven compressor.

In operating refrigerating apparatus of the compression type, a desirable sequence of operation is to start the compressor at a temperature of the evaporator high enough to indicate that the evaporator has defrosted and to stop it at a relatively low evaporator temperature, the evaporator thus being defrosted after each cycle of operation of the compressor, This type of operation is disclosed in a patent of Charles B. Spangenberg No. 2,191,966.

The object of my invention is to provide an improved and inexpensive switching device for producingthe type of operation of a refrigeration system as disclosed in the above referred to patent.

More specifically the object of my invention is to provide a compact, inexpensive controller for refrigerating compressors using a minimum of parts but still offering great freedom of adjustment and adaptability, the controller being responsive to both suction and head pressure of the compressor.

A further object of my invention is to provide a compressor controller for producing the type of ing it in open position of the switch. Further objects and advantages 'of my inven-- tion will become apparent from the following detailed description and annexed drawings wherein:

Figure l is a diagrammatic representation of a refrigerating system including a preferred form of the controller of my invention.

Figure 2 is a view of the interior of the controller of Figure 1, that is, with the cover removed,

Figure 3is a detail view taken along line 3-4 of Figure 2.

Figure 4 is a view of the controller of Figures 1 and 2 as seen from behind, this view being taken along line 4-4 of Figure 5.

Figure 5 is a view of the controller of Figure 4 taken along line 5-5.

Figure 6 is a view of a modified form of my invention.

Referring to Figure 1 of the drawings, numeral i0 designates a compressor of a conventional type refrigerating system.- The compressor is driven by an electric motor H by means of a. belt i2. The compressor discharges into a condenser l3 through a pipe l4 and the condenser is connected to an expansion valve l5 by a pipe Hi. The expansion valve l5 controls the admission of refrigerant to an evaporator l1 located within a chamber It, to be refrigerated. The outlet of the evaporator I1 is connected to the suction side of the compressor ill by a pipe IS, The expansion valve I5 is of a type well known in the art wherein the expansion of refrigerant into the evaporator is thermostatically controlled. Numeral 22 designatesa bulb filled with an expansible fluid which is located adjacent to the outlet line or conduit of the evaporator H, The bulb 22 is connected by a capillary tube 23 to the expansion valve IS. The manner of operation of expansion valves in refrigeration systems of the type disclosed is well known in the art and need not be described in detail.

The compressor motor I I is controlled by a controller 26, the details of which are more readily ascertainable from an inspection of Figure 2 wherein the interior of the controller 26 is shown. The controller 26 has a front cover 25 which may be suitably fastened to casing 21. In Figure 2 the controller is shown with the cover removed.

Referring to Figure 2, the controller 26 comprises a generally rectangular casing 21 within which is a horizontal plate 28 for supporting a snap-switch 29.. As will presently be described, the snap-switch 29 is operated in response to suction pressur and head pressure of the compressor. Numeral 32 designates a housing which encloses an expansible and contractible bellows, the interior of which is connected to the suction line IQ of the compressor by a tube 33 (see Figure 1). The housing 32 is flanged and the flange is secured to the lower part of the casing 21 by screws 34 and 35. Numeral 36 designates a similar housing within which is an expansible and contractible bellows, the interior of which is connected to the discharge conduit of the compressor by a tube 31 (see Figure 1). The housing 36 is flanged similarly to the housing 32 and the flange is attached to the lower part of the casing 21 by screws 39 and 40.

The screw 35 is relatively long and extends through a supporting standard 4| for the plate 28 as shown. A similar'screw 42 extends through another standard 43 lik the standard 4| which also serves to support the horizontal plate 28 as shown.

The snap-switch 29 is the same as the one disclosed in the application of Albert E. Baak Serial No. 307,991, filed on December 7, 1939. The snap-switch is enclosed within a Bakelite housing or casing 45 and has electrical terminals formed by screws 46 and 41. The snap-switch 29 has a Bakelite operating stem 48 extending below the casing of the switch. The snap-switch 29 is of a type wherein movement of the operating stem 48 in an upward direction closes the switch and movement of the operating stem 48 in a downward direction opens the switch. After the switch has been operated to open or closed positions it tends to remain in that position.

Numerals 50 and designate wires connected to the terminal screws 46 and 41 respectively. Wire 51 and another wire 52 are connected to a suitable source of power and wires 59 and 52 are connected to the compressor motor as shown in Figure 1. Wires 58 and 5| extend through an opening in casing 21 as shown.

The moveable end of the bellows within housing 32 is connected to an operating stem 55 which extends through a nut 54 as shown in Figure 2. The upper end of the stem 55 carries a ball member 56 which is disposed loosely within an opening in a floating operating lever 51. The left end of the operating lever 51 is disposed between two cams 58 and 59 and the opposite end of the operating lever 51. engages in a slot in the operating stem 48 of the snap-switch. Numeral 68 designates a flexible or resilient leaf attached to the upper side of the operating lever 51 by rivets or the like, the leaf 60 engaging the ball 56. Numeral 6| designates a similar resilient leaf riveted to the lower side of operating lever 51, the leaf 6! having an opening through which the operating stem extends and this leaf also engaging the ball 56. The ball 56 and the resilient leaves 60 and GI form a strain release connection between the operating stem 55 and the operating lever 51.

The cams 58 and 59 have. spiral contours as may best be seen on Figure 3. The cam 58 is mounted on a shaft which is journaled in a side wall of the casing 21 and which may be rotated by a manual knob 65 exteriorly of the casing 21.

Adjacent to manual knob is a dial 66 which may be graduated if desired. The cam 59 is mounted on a similar shaft journaled in the side wall of the casing 21 and rotatable by a manual knob 51 exteriorly of the casing 21. 61 is a dial 68 similar to the dial 66 which may also be graduated if desired. The cams 58 and 59 form stops between which the left end of the operating lever 51 is moveable.

From the immediately foregoing it can be seen that when the bellows within housing 32 expands in response to rising suction pressure in the suction conduit l9, the operating stem 55 is moved upwardly carrying the operating lever 51 with it until the left end of lever 51 engages cam 58. After the left end of lever 51 engages cam 58 further expansion of the bellows within housing 32 causes lever 51 to pivot about cam 58, that is, rotating in a counter-clockwise direction so that the right end of lever 51 moves operating stem 48 upwardly so as to close snap-switch 29, closure of snap-switch 29 completing a circuit for the compressor motor through wires 51, 59 and 52. If the suction pressure should continue to rise after lever 51 is incapable of further movement Adjacent to knob the stem may continue to move upward slightly, the ball 56 moving relatively to the lever 51 by flexing leaf away from the lever 51, and thus relieving the strain on the operating mechanism of switch 29.

Upon the suction pressure falling after the compressor motor is started, the bellows within housing 32 will contract drawing operating stem 55 downwardly and causing the left end of lever 51 to be moved downwardly until at a predetermined suction pressure it engages the cam '59. Upon further contraction of the bellows within housing 32, the lever 51 will pivot about cam 58, that is, moving in a clockwise direction so that its right end moves the operating stem 48 of switch 29 downwardly so as to open the switch 29 and thereby stop the compressor. Movement of the operating stem 55 downwardly after the lever 51 is incapable of further downward movement due to opening of the switch 29, the ball 56 will be moved downwardly relative to the lever 51, the ball 55 flexing the leaf 5| away from the lever 51. The resilient connections formed by the leaves 68 and SI thus prevent any strain from being placed upon the operating connection between the stem 48 and the snap-switch 29.

From the foregoing it can readily be seen that the operating differential of the snap-switch 29 in response to suction pressure is determined by the relative adjustment of the cams 58 and 59. If cam 58'is rotated in a direction which would tend to move lever 51 downwardly as seen on Figure 2, it is apparent that the pressure at which the switch is closed is lowered, because then the pressure will not have to rise to as high value before lever 51 engages cam 58 and begins to rotate in a counter-clockwise direction. If cam 59 is rotated in the opposite direction obviously the suction pressure at which switch 29 is closed will be raised. If cam 59 is rotated in a direction so as to decrease the space between the two cams the pressure at which switch 29 is opened will be raised because obviously then the pressure will not have to decrease to as low a value before lever 51 engages cam 59 and begins to 1'0- tate in a clockwise direction. Obviously therefore, the differential of operation of the switch 29 can be adjusted by varying the positions of cams 58 and 59 by their respective manual knobs. It is also apparent that the pressure at which the switch 29 is closed and the pressure at which it is opened can be independently adjusted.

The movable end of the bellows within the housing 36 is connected to an operating stem 19 which extends through a nut 1|. The operating stem 10 carries a screw member 12 which may be adjusted in a manner to adjust the length of the stem 10 for a purpose which will be presently pointed out. Numeral 13 designates a bracket which is attached to the back of the casing 21 by a rivet or the like and which is rotatable a small amount about its pivot. The bracket 13 carries a pivot 14 to which is pivoted an operating lever 15, the lever 15 having downwardly bent ears which engage the pivot 14. The right end of the operating lever 15 engages in a slot in the operating stem 48 of switch 29, this slot being similar to the one in which the right end of lever 51 engages. The left end of lever 15 is adjacent the upper end of operating stem 19, and when the discharge pressure of the compressor rises the operating stem 10 may engage the lever 15 rotating it in a clockwise direction so that its right end moves the operating stem 48 in a downward direction so as to open the snapswitch 29. When the last mentioned operation occurs the right end of the lever 51 moves downwardly, the lever 51 moving relatively to the ball 56 with the leaves 6! and 60 flexing if lever 51 is engaging cam 58 at the time. Thus the strain release connection between the operating stem 55 and the lever permits operation of the snapswitch 29 in response to the head pressure bellows within the housing 36. It should be noted that if the snap-switch 29 is opened in response to head pressure, the suction pressure must rise to a predetermined value to reclose the switch, this pressure value of course being the one at which the switch is normally closed by suction pressure. The switch cannot be closed by head pressure. The bracket 13 has two extending fingers, as shown, between which is a small eccentric 11. When the eccentric H is adjusted, the bracket 13 may be adjusted about the rivet which attaches it to the back of the casing 21. By adjusting the position of bracket 13, the position of pivot 14 relative to the operating stem 19 and the operating stem 48 is adjusted. Thus the 'movement of operating stem required for the operation of switch 29 may be adjusted. By adjusting the screw member 1 I, the discharge pressure at which lever 15 will be operated to open switch 29 may be adjusted.

Figure 4 is a back view of the controller of -F ig ures 1 and 2 with the cover in place. The-cover carries a manual operating means which is pivoted to the cover and which is seen on Figure 4. The manual operating means for the controller 26 comprises a manual lever 80, the left end of which is bent into a U shape and which is carried on a pivot 8| as may best be seen on Figure 5. The right end of the lever 80 has a bent over finger 82 (see Figure l) which extends through a slot 83 in the cover of the instrument. The lever 80 has a projecting portion 85 carrying a pin 86 as may be seen on Figures 4 and 5. Numeral 81 designates a pin extending inwardly from the cover of the controller and numeral 88 designates a similar but slightly larger pin. Numeral 89 designates a flexible spr'ng element which is wound about the pin 88 and the ends of which extend downwardly on opposite sides of the pins 86 and 81 adjacent thereto. Normally the lever 89 assumes an intermediate position in which it is in as seen on Figures 1 and 4. ever the lever 80 is moved out of this position the pin 86 flexes either one or the other of the downwardly extending ends of hte resilient element 89 which tends to return the lever 89 to its intermediate or normal position.

Numeral 90 designates a second shorter lever, the left end of which is bent into a U shape and which is carried on the pivot pin iii. The lever 90 has a small bent over projection 9| and a longer projection 92 which extends to a point adjacent to and above the operating lever 51. Numeral 93 designates a resilient bracket member attached to the lever 88 and having a portion which extends outwardly to a position engaging the operating stem 48 of the switch 29. Numeral 95 designates a small ear bent over from the material adjacent slot 83. The finger 82 is adapted to be latched in engagement with the car 95 as will presently be described.

As shown on Figure 1 the finger 82 of lever 88 may have three positions. The intermediate position in which the lever 80 normally is, is designated on Figure 1 as automatic. When it is desired to manually start the compressor the lever 88 may be manually moved upwardly by moving When i each cycle of operation.

the ear 82 upwardly'in slot 83 adjacent to the graduation marked start. When this is done the resilient bracket 93 by engaging the operating stem 48 of switch 29 moves the stem upwardly moving the switch 29 to closed position. As soon as the finger 82 is released the resilient spring element 89 returns the lever to the automatic position, that is, its intermediate position. If desired the snap-switch 29 may be manually latched in an off position so that the compressor cannot be automatically started. To do this the operating manual lever 88 is moved downwardly by moving the finger 82 downwardly in slot 83 to a position below ear adjacent to the graduation marked off on Figure 1. The car 82 may be latched or secured below the ear 95. When the manual lever 80 is thus moved downwardly the projection 92 engages the operating lever 51 and moves its left end in a downward direction so as to move the operating stem 48 of switch '39 downwardly to thus open the switch. The strain release mechanism associated with lever 51 as previously described permits downward movement of the left end if lever 57 is engaging cam 58 at the time. When the manual lever 86 is thus latched in its lowermost position, that is, in the off position, the compressor will remain out of operation until the manual latch is released. Whenever the finger 82 is disengaged from the ear 95 the manual lever 88 will be returned to its intermediate, that is, the automatic position in response to the resilient spring element 89.

From the foregoing description the complete operation of the system I have disclosed with the controller of my invention should be apparent. When the finger 82 is in the automatic position as shown on Figure 1 the compressor will be started whenever the suction pressure rises to the relatively high value at which the snap-switch 29 is closed in the manner already described. The suction pressure at which the snap-switch closes is normally set at a high enough value so that the evaporator will normally be defrosted after This operation corresponds to that disclosed in the patent referred to above. After having been started the compressor remains in operation until the suction pressure falls to a relatively low value determined by the setting of cam 59 as described above. When this pressure is reached the snap-switch 29 is opened and the compressor is stopped and thereafter the cycle will be repeated. Also as described above whenever the discharge pressure of the compressor should rise to a relatively high value the operating stem 19 will operate lever 75 to open the snapswitch 29 if it is closed at the time. If the snapswitch 29 is open the discharge pressure responsive device may prevent it from being closed by the suction pressure responsive device, the strain release arrangement permitting movement of the suction pressure below without movement of the switch.

As described above, the compressor may be manually started at any time by manipulation of the finger 82 or the controller may be latched in its off position, also by manipulation of the finger 82 as described above.

Referring to Figure 6 of the drawings I have shown a slightly modified form of my invention. In this form of the invention the operating lever I51 on which the suction pressure responsive device acts is not made as a floating lever but is pivoted on a pivot I01. The left end of the operating lever I5! is pivoted to a secondary lever I02, The left end of the lever I02 operates between the cams 58 and 59 which act as stops as in the previous embodiment and the right end of lever i02 engages the operating stem 38 of the snap-switch 29 as in the previous embodiment. The head pressure responsive device acts on a lever 75 which engages the operating stem 48 of the snap-switch 29 as in the previous embodiment.

In operation the device of Figure 6 operates very similarly to that of the previous embodiment. Upon a rise in suction pressure the operating lever I51 is rotated in a clockwise direction about the pin NH and the secondary lever I02 is rotated in a clockwise direction pivoting about the slot in the operating stem 48 until its left end engages the cam 58. After the left end of lever I02 engages cam 58 the lever then pivots about cam 58 and is rotated in a counter-clockwise direction so that its right end moves the operating stem 48 upwardly so as to close the snap-switch 29. After the compressor has been started and the suction pressure falls the suction pressure responsive device moves the lever i5! in'a counter-clockwise direction about pivot llii. This action moves lever I62 downwardly until its left end engages the cam 59. Further downward movement of the left end of lever I5? causes lever N12 to be rotated in a clockwise direction pivoting about the cam 59 with its right end moving the operating stem 48 downwardly so as to open the snapswitch 29. The head pressure responsive device may open switch 29 as in the previous embodiment.

From the foregoing it can be seen that the device of Figure 6 operates very similarly to that of the previous embodiment and that the adjustments of the closing and opening pressures of the snap-switch may be made in the same manner.

From the foregoing it should be appreciated b those skilled in the art that I have provided a very simple, inexpensive and useful device for controlling the compressor of a compression type refrigerating system so as to produce a sequence of operation whereby the evaporator is defrostedafter each cycle of operation of the compressor. The controller provides for independent adjustment of the closing and opening pressures of the switch and is entirely free from complex or delicate mechanism which might give rise to dimculties in use.

The embodiments of my invention which I have disclosed are illustrative of its preferred form. There are many modifications which may be made by those skilled in the art and there are many changes which readily fall within the realm and scope of my invention. The invention is not to be limited therefore by my disclosure but only by the scope of the claims appended hereto.

I claim as my invention:

1. In a device of the class described, in combination, a switch, switch actuating means comprising a floating lever for operating the switch to both of its positions, means forming stops between which the lever moves, means for moving the lever between said stops to actuate the switch, and a separate automatic means for directly actuating the switch independently of the lever.

2. In a device of the class described, in combination, switch means having on and off positions and being of a type adapted to stay in the position to which it is operated, actuating means for the switch means comprising a floating lever, means forming stops between which the lever operates, means for actuating the lever, an automatic device for operating said last means, and a manually operable member, said member having means whereby when the member is moved in one direction the switch is operated to one position and When the member is moved in another direction the switch is operated to another position.

3. In a device of the class described, in combination, switch means having on and oil positions and being of a type adapted to stay in the position to which it is operated, actuating means for the switch means comprising a floating lever, means forming stops between which the lever operates, means for actuating the lever, an automatic device for operating said last means, a manually operable member, said member having means whereby when the member is moved in one direction the switch is operated to one position and when the member is moved in another direction the switch is operated to another position, and means for latching said member so as to keep said switch in said other position.

4. In a device of the character described, in combination, a snap switch having open and closed positions and being of a type adapted to remain in the position to which it is operated, said switch having a reciprocatable operating stem, a floating operating lever associated with said stem, stops between which said lever moves, a pivoted lever associated with said floating lever and a device acting on said pivoted lever to move said floating lever between said stops for actuating said stem and thereby operating the switch.

5. In a device of the character described, in combination, a snap switch having open and closed positions and being of a type adapted to remain in the position to which it is operated, said switch having a reciprocatable operating stem, a floating operating lever associated with said stem, stops between which said lever moves and a device for moving said lever between said stops and actuating said stem so as to operate the switch and a separate device for moving said stem irrespective of the position of said floating lever.

6. In a device oi the character described, in combination, a snap switch having open and closed positions and being of a type adapted to remain in the position to which it is operated, said switch having a reciprocatable operating stem, a floating operating lever associated with said stem, stops between which said lever moves, a device for moving said lever between said stops and actuating said stem so as to operate the switch and a separate device for moving said stem irrespective of the position of said floating lever, said last device including a pivoted lever associated with said stem and means whereby the pivot of said last lever may be adjusted so as to vary the point at which said last device actuates the switch.

7. In a device of the class described, in combination, switch means having on and off positions and being of a type adapted to stay in the position to which it is operated, actuating means for the switch means comprising a floating lever, means forming stops between which the lever operates, automatic advanceable and retractable means for actuating the lever, a manually operable member, said member having means whereby when the member is moved in one direction the switch is operated to one position and when the member is moved in another direction the switch is operated to another position, means for latching said member so as to keep said switch in said other position, and means normally biasing said member toward an intermediate position.

8. In a device or the character described, in combination, a switch having open and closed positions and being of a type adapted to stay in the position to which it is operated, means including an operating lever for said switch, a manually operable lever having an intermediate position and means normally biasing said last lever so as to keep it in said intermediate position, and said manually operable lever having projections adapted to engage said first "means for operating said switch when the manually operable lever is moved in either direction about its pivot, said manually operable lever returning to its intermediate position when released.

9. In a device of the character described, in combination, a switch having open and closed positions and being of a type adapted to stay in the position to which it is operated, means including an operating lever for said switch, a manually operable lever having an intermediate position and means normally biasing said last lever so as to keep it in said intermediate position, said manually operable lever having proiections adapted to engage said first means for operating said switch when the manuallyoperable lever is moved in either direction about its pivot, said manually operable lever returning to its intermediate position when released, and means for latching said manually operable lever in a position wherein said switch is closed.

10. In a device of the class described, in combination, a switch, switch actuating means comprising a floating lever for operating the switch, means forming stops between which the lever moves, means for moving the lever" between said stops to actuate the switch, and a separate automatic means for actuating the switch independently of the lever, and means forming strain release connections between said lever and said lever moving means.

11. In a device of the character described, in combination, a snap switch having open and closed positions and being of a type adapted to remain in the position to which it is operated, said switch having a reciprocatable operating stem, a floating operating lever associated with said stem, stops between which said lever moves, a device for moving said lever between said stops and actuating said stem so as to operate the switch and a separate device for moving said stem irrespective of the position of said floating lever, and means forming strain release connections between said first device and said lever.

12. In a device of the class described, in combination, switch means having on and oil positions and being of a type adapted to stay in the position to which it is operated, actuating means for the switch means comprising a floating lever, means forming stops between which the lever operates, means for actuating the lever, a device for operating said last means, and a manually operable member, said member having means whereby when the member is moved in one direction the switch is operated to one position and when the member is moved in another direction the switch is operated to another position, and means forming strain release connections between the device and the lever actuating means.

13. In a device of the class described, in com bination. switch means having on and oii positions and being of a type adapted to stay in the position to which it is operated, actuating means for the switch means comprising a floating lever, means forming stops between which the lever operates, means for actuating the lever, a pressure responsive device for operating said last means at predetermined pressures, and a separate pressure actuated member for actuating said switch, said member being so constructed and arranged as to be eifective to operate the switch to one position and ineffective to operate it to the other position whereby if said member moves the switch to one position the pressure aifecting said pressure responsive device must attain a predetermined value to move the switch to the other position.

14. In a device of the character described, in combination, a two position switch of the type which tends to remain in either of its two positions to which it is operated, a floating lever associated at one end with said switch for causin operation thereof, a pair of stops for limiting movement of the opposite end of said lever, said lever having an opening at an intermediate portion thereof, a condition responsive device, a connecting rod associated at one end with said device and having an enlarged head at its opposite end fitting loosely within the opening in said lever, and resilient strain relief meanscarried by said lever and tending to maintain the head of said connecting rod within the opening in said lever, but permitting relative movement therebetween upon movement of said condition responsive device after further movement of said lever has been prevented.

15. In a device of the character described, in combination, a two position switch of the type which tends to remain in either of its two positions to which it is operated, a floating lever associated at one end with said switch for causing operation thereof, a pair of stops for limiting movement of the opposite end of said lever, said level-having an opening at an intermediate portion thereof, a condition responsive device, a connecting rod associated at one end with said device and having an enlarged head at its opposite end fitting loosely within the opening in said lever, resilient strain relief means carried by said lever and tending to maintain the head of said connecting rod within the opening in said lever,

' but permitting relative movement therebetween value'of said condition, such action being permitted by said strain relief means.

16. In a device of the character described, in combination, a two position switch of the type which tends to remain in either of its two positions to which it is operated, a floating lever associated at one end with said switch for causing operation thereof, a pair of stops for limiting movement of the opposite end of said lever, a first condition responsive device, means including a strain release connection between said device and lever whereby the latter may be operated by the former, a second condition responsive device, a lever having a pivot, one end 01' said lever being associated with said second condition responsive device. means connecting the other end of said lever to said switch for actuating the same, and means for adjusting the position of said pivot to vary the differential of operation of said switch by said second condition responsive device.

17. In a device of the character described comprising in combination, a snap action switch, an operator therefor, a condition responsive device, a pivotally mounted adjusting member, a lever, a

pivot for said lever carried by said member, one end of said lever being operatively associated with said condition responsive device, the other end of said lever being associated with the operator for said switch whereby said switch may be operated by said condition responsive device, and means for variably positioning said adjusting member and hence the pivot for said lever for varying the differential of operation of said switch.

18. in a control mechanism, in combination, a casing having an opening therein allowing access to the casing, a control device within said casing, automatic means attached to said casin for operating said control device, a cover for closin the opening in said casing, and manual operatin means for said control device comprising means carried by and located inside of said cover but manually operable from the outside thereof and which cooperates with said contro1 device when the cover is in place so that said control device is manually operable from outside said casing independently of said automatic means.

19. In a switching mechanism, in combination, a casing having an opening therein allowing access to the casing, switching ,means within said casing, a floating lever in said casing for actuating said switching means, automatic means carried by said casing for actuating said floating lever, an adjustable stop carried by said casing and having a portion within said casing engageable by said floating lever to cause actuation of said switching means upon actuation of said floating lever into engagement with said stop by said automatic means, said adjustable stop having a portion outside of said casing by which it may be adjusted, a cover for the opening in said casing, and manually operable means for said switching means comprising means carried by and located inside of said cover but operable from outside said cover for operating said switching means when said cover is in place.

20. In a switching mechanism, a two position switch of the type that remains in the position to which it is operated and including a reciprocable operating stem, a floating lever connected to said stem at one point on said lever, a condition responsive device acting upon said lever at a second point removed from said second first point, and stop means cooperating with said lever at a third point, to cause movement of said stem by said lever upon a predetermined movement of said lever by said condition responsive device.

21. In a control mechanism, in combination, a

casing having an opening therein allowing access to the casing, a control device within said casing, first automatic means attached to said casing for operating said control device, a second automatic means attached to the casing for actuating the control device to its inoperative position, a cover for closing the opening into the casing, and manual operating means for said control device including means carried by-and located inside of said cover but manually operable from the outside thereof and which cooperates with said control device when the cover is in place so that said control device is manually operable from outside the casing independently of said first and second automatic means, and means associated with the manual operating means inside the cover for holding the manual operating means in a predetermined position.

22. In a control mechanism, in combination,

a casing having an opening therein allowing access to the casing, a control device within said casing, automatic means attached to said casing for operating said control device, a cover for closing the opening in said casing, and additional means for controlling the operation of said control device including means mounted on and lo-' cated within said cover arranged to provid such additional operation when said cover is in place on said control mechanism.

23. In a control mechanism, in combination, a casing having an opening therein allowing access to the casing, a control device within said casing, automatic means attached to said casing for operating said control device, a cover for closing the opening in said casing, additional means for controlling the operation of said control device including means completely mounted on the inside of said cover arranged to provide such additional operation when said cover is in place on said control mechanism independently of the automatic means, and means on the cover for maintaining the additional means in a predetermined position.

24. In a control mechanism, in combination, a casing having an opening therein allowing access to the casing, a control device within said casing, automatic means attached to said casing for operating said control device, a cover for closing the opening in said casing, manual operating means for said control device comprising means carried by and located inside of said cover but manually operable from the outside thereof and which cooperates with said control device when the cover is in place so that said control device is manually operable from outside said casing independently of said automatic means, and means associated with the manual operating means for automatically returning the manual operating means to a predetermined position after the manual operating means has been moved to a position for operating said control device.

25 In a control mechanism, in combination, a casing having an opening therein allowing access to the casing, a control device within said casing, a cover for closing the opening in said casing, and means for controlling the operation of said control device including means completely carried by the inside of said cover and arranged to provide operation of the control device when said cover is in place on said control mechanism.

26. In a control mechanism, in combination, a casing having an opening therein allowing access to the casing, a control device within said casing, automatic means attached to said casing for operating said control device, a cover for closing the openings in said casing, manual operating means for said control device comprising means carried by and located inside of said cover, but manually operable from the outside thereof and which cooperates with the control device when the cover is in place so that said control device ismanually operable from outside of said casing independently of said automatic means, means for holding the manual operating means in ,a first predetermined position, and means for automatically returning the manual operating means to a second predetermined position after said manual means has been moved to a third predetermined position for operating said control device.

CARL G. KRONMILLER.

CERTIFICATE OF CORHECTLVION. 7 Patent no. 2,377,503. June 1915.

cums. KRONMILLER.

It is hereby certified that error appears in the printed specification of the above numbered patent reqfiiring' correction as follows: Page 6, first column, line 149, claim 20, strike out the word "second"; and that the said Letters Patent 'shoald be read with this correction therein that the same may confom to the record of the case in the Patent Office.

Signed and sealed this 2nd day of October, A. D. 1915.

Leslie Frazer (Seal) First Assistant Comriissioner of Patents.

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