Refrigeration System With Delay Timing Mechanism

Abstract

Protection against refrigeration compressor burnout by short cycling is provided by a delay timing mechanism having a motor and solenoid. The motor is constantly energized and the solenoid controlled by a thermostat stalls or releases the mechanism causing timer operation through its cycle. The timer runs through its delay period during the normal off period, allowing fast restart of the compressor. Also the timer provides a longer delay following a short cycle then following a normal cycle. This is accomplished by operating the timer for a period of time after the compressor is started.

Parent Case Text

CROSS-REFERENCE TO RELATED APPLICATION

This application is a division of my application Ser. No. 849,961 filed Aug. 14, 1969, now U.S. Pat. No. 3,598,214 dated Aug. 10, 1971.

Description

BRIEF SUMMARY OF INVENTION

This invention relates to automatic controls and more particularly to timing devices for controlling and protecting compressors in refrigeration systems.

The primary object of the invention is the provision of a compact and simplified control system which stops and starts the refrigeration compressor at the command of a condition responsive device and also interposes a delay in restarting the compressor for protecting against overload.

A further object of the invention is the provision of a simplified refrigeration control system and control device which provides a normal delay before restart for pressure equalization following a normal cycle, but which interposes a substantially longer delay if the compressor stoppage was due to operation of a safety control.

Another object of the invention is the provision of a device and system providing operation of the blower for the refrigeration system for longer periods than the compressor is operated.

A further object of the invention is to provide a simplified timing control system using an electric motor, and which operates in a predetermined cycle without requiring circuitry or switches for timer motor control.

Another object is to provide a timing device in which operation is controlled by selectively stalling or releasing the timer motor.

A further object is to provide a stalling mechanism in which a timing motor is selectively stalled or released and in which the actual stalling force is removed from the mechanism controlling the stalling or releasing.

Other objects will appear from the following description and appended claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic exploded view of a mechanism embodying the invention;

FIG. 1a is an enlarged view of the stalling wheel of FIG. 1;

FIG. 2 is a schematic wiring diagram of a complete refrigeration control system embodying the mechanism of the invention;

FIG. 3 is a chart showing the preferred operating sequence as occurs on a normal refrigeration cycle;

FIG. 4 is a chart showing a modified operating cycle;

FIG. 5 illustrates a modification of FIG. 1, and in which;

FIG. 6 is a chart showing the operating sequence provided by the arrangement of FIG. 5.

DETAILED DESCRIPTION OF INVENTION

Referring now to FIG. 1, reference character 1 indicates the timer motor shown schematically, this motor driving a pinion 2 meshing with gear 3 which is carried by and drives a shaft 4 which in turn drives a pinion 5. This pinion drives a final gear 6 which is carried by and drives a cam shaft 7 carrying a cam 8. The timer motor 1 drives the final gear 6 and the cam or controller 8 in a counterclockwise direction as indicated by the arrows.

The timing means above described, through cam 8 operates a compressor switch generally indicated as 9. This switch or control device comprises an upper switchblade 10 and a lower switchblade 11, each anchored at its left-hand end and both blades being biased downwardly toward the cam 8. The lower switchblade 11 is provided with an opening 12 allowing the blade to straddle the cam 8 and providing an internal cam follower surface 13. This blade 11 carries a contact 14 and is provided with an extended portion 15 cooperating with the latch 16. The upper switch blade 10 includes a cam follower bracket 17 which extends downwardly and rides the cam 8 at a point spaced counterclockwise from the cam follower surface 13. Switchblade 10 also carries contact 18 arranged for engaging contact 14 on switchblade 11. The cam or controller 8 consists of a main cam surface including a generally circular portion 20 and a rise portion 21. The cam also includes a dropoff section 22 which causes dropping of both switchblades with snap action.

The latch 16 is pivoted on a shaft diagrammatically shown as 24 and includes a latching surface 25 and a camming surface 26, these surfaces cooperating with extension 15 of lower switchblade 11 as will be described. The latch 16 also is provided with a biasing spring 27 which biases this latch toward the end 15 of the switchblade 11.

The shaft 24 which carries the latch 16 also carries a "run" stalling lever 30. The latch 16 and the run staller 30 are arranged to operate in unison. While these two parts are shown as separated and spaced apart for illustrative purposes, it will be apparent that these two parts may be molded into a single piece thus ensuring correct alignment of the working surfaces and lowering production cost.

The run-stalling member 30 is shown in disengaged position and is arranged to cooperate with the run-stalling lug 31 carried by the final gear 6 to provide a mechanical stopping means. When the run stalling member 30 is rotated counterclockwise, its stalling surface or movable abutment 32 will be brought into the path of the stalling lug 31 on the final gear. Thus the final gear will be stalled when it rotates to the point where lug 31 engages stalling surface 32. Clockwise rotation of the stalling member 30 takes the stalling surface 32 out of the path of the stalling lug 31 and thus the timer is free to proceed beyond this point.

Reference character 35 indicates a solenoid lever which is pivoted at 36. This lever 35 is biased in a counterclockwise direction by a spring 37 and is rotated clockwise against the force of spring 37 by the solenoid or electromagnet 38. The solenoid lever 35 includes an arm 39 carrying a stalling surface 40 adapted to be engaged by a stalling lug 41 on the final gear 6 providing a mechanical stopping means. The solenoid lever also carries a pin 42 which is arranged to engage the switchblade 43 of the blower switch generally indicated as 44. The switchblade 43 is anchored at its left-hand end and is biased upwardly. This switchblade includes a movable contact 45 adapted to engage a stationary contact 46. This switchblade is biased upwardly for causing the contacts to engage. The pin 42 on the solenoid lever pushes the switchblade 43 downwardly when the solenoid is deenergized for opening switch 44.

The solenoid lever 35 also carries a pin 50 which is adapted to engage the portion 51 of the run stall member 30. This pin serves to rotate the run stall member in a clockwise direction when the solenoid is deenergized. The solenoid lever is also formed with an opening 52 through which the supporting shaft 24 for the run stall member 30 and latch 16 passes. This serves as a stop for limiting outward travel of the solenoid lever 35 and also limits the inward travel of the stalling surface 40 on this lever.

The shaft 4 which carries the pinion 5 is journaled in a spring lever generally indicated as 55. This spring lever is pivotally supported on the same center as the cam shaft 7 and is biased in a counterclockwise direction by a spring 56. The amount of counterclockwise movement is limited by a fixed stop 57. This stop is located in a manner to cause the gear shaft 4 to be in alignment with the cam shaft 7 when the spring lever 55 engages stop 57. Spring lever 55 thus provides a movable bearing for pinion 5. The pinion 5 is rigidly attached to a stalling wheel 58 having ratchetlike teeth 59 adapted to come in contact with a stationary stalling lug 60. The stalling lug 60 may be struckout of the enclosure for the timing unit or mounted in any suitable manner. It is preferable that the angle of this lug at the point where engaged by the stalling wheel be tangent to a circle centered with the shaft 7. It is also preferable that the teeth of the stalling wheel be cut so that the stalling surfaces at the point of engagement with lug 60 are parallel with lug 63. The location of the stalling lug 60 relative to the fixed stop 57 must be such as to provide clearance between the stalling wheel 58 and the stalling lug 60 when the spring lever 55 is engaging the fixed stop 57.

FIG. 2 shows the preferred complete refrigeration control system embodying the mechanism of FIG. 1. This system includes a compressor motor 70 and a blower motor 71 which blows air across the evaporator and/or condenser of the refrigeration system. The compressor motor is controlled by the usual contactor having a contactor coil C and switches C-1 and C-2 operated thereby. The system also includes a low-voltage thermostat 72, a low-voltage transformer 73 and safety controls comprising a high-pressure cutout 74 and a low-pressure cutout 75. The latter controls and associated wiring comprise a means for energizing the motor 1. The operation of the mechanism and complete system will now be described.

OPERATION OF FIGS. 1 AND 2

With the parts in the positions shown, the system is in the "Standby" position. The timer solenoid is deenergized which has the "Standby" stalling surface 40 in the path of lug 41 on final gear 6. Even though the timer motor 1 is energized, no motion can take place as the timer is effectively stalled. The compressor switch 9 is open and thus the compressor motor contactor C is deenergized causing the compressor motor to be at rest. Also the blower switch 44 is open and the blower is at rest. Assuming that the pressures within the refrigeration system are satisfactory and that switches 74 and 75 are closed, the timer motor 1 is energized and is ready to drive the timer any time the timing mechanism is released by the stalling mechanism. When the thermostat 72 calls for cooling, it will energize the timer solenoid 38 which rotates the solenoid lever 35 about its pivot 36. This closes blower switch 44 and also removes the stalling surface 40 from the path of the stalling lug 41 on gear 6. This in turn allows the spring 56 to rotate the spring lever 55 downwardly releasing the stalling wheel 59 from the stationary stalling lug 60. This same clockwise rotation of solenoid lever 35 also moves the pin 50 on this lever away from the surface 51 of the stalling member 30. The stalling member 30 however does not move into stalling position at this time as it is being held in released position by latch 16.

As the "Standby" stall has been released, the timer motor now drives the gear 6 and cam 8 in a counterclockwise direction. In a short time the inclined section 21 of the cam engages the cam follower surfaces 13 and 17 of the switchblades 10 and 11 and starts raising the switchblades in unison with the contacts separated. As lower blade 11 is cammed upwardly, the end 15 rides up the camming surface 26 on the latch 16 allowing gradual counterclockwise rotation of the latch. When the end 15 of the blade rises above the latching surface 25 of the latch, the spring 27 is free to pull the latch into complete latching position. This same counterclockwise latching motion also causes the run-stalling member 30 to bring its stalling surface 32 into the path of the stalling lug 31 on gear 6. Inward travel of the latch 16 and stalling member 30 is now limited by the surface 51 on member 30 engaging the pin 50 on the solenoid lever 35.

As the cam 8 continues to rotate, the cam follower surface 13 on switchblade 11 will ride down the dropoff section 22 allowing the end 15 of the switchblade to rest on the latching surface 25 of latch 16 which is now in latching position. On continued rotation of the cam 8, the follower surface 17 on upper switchblade 10 drops off the dropoff section 22 of the cam. Switchblade 10 now drops abruptly bringing contact 18 into engagement with contact 14 and thus closing the load switch 9. This energizes the compressor contactor coil C which in turn closes its contacts C-1 and C-2 starting the compressor motor 70.

The timing mechanism will now continue to run for a predetermined time until the run stall lug 31 on gear 6 engages the stalling surface 32 on the run stall member 30 which is now in stalling position.

When the run stall member 31 engages the stalling surface 32, it stops further rotation of the drive gear 6. In reaction to this, the pinion 5 begins moving bodily in an upward direction, this motion being allowed by the spring lever 55 disengaging stop 57 and moving against the bias of the spring 56. When the teeth on the staller wheel 58 engage the stalling lug 60, the timer motor is effectively stalled.

Due to the reaction-type stalling mechanism provided by the invention, the pressure required for stalling at the stalling lugs 31 or 41 is only that required to compress the spring 56 sufficiently to bring the stalling wheel into engagement with the stalling surface 60. The stalling lugs 31 and 41 on the final gear are never required to stall the full torque of the motor through the reduction gears. Instead, the actual stalling force for the motor is applied ahead of the gear reduction where the torque and force required is considerably lower. This arrangement in which the stalling force is merely triggered by the solenoid operated surfaces makes it possible to design the timer mechanism with the light duty parts and with a relatively small solenoid. This special stalling mechanism could be omitted, using a direct drive between the timer motor and the gear 6. However, this would require the parts being designed sufficiently strong to carry the relatively high loads, and to use a solenoid sufficiently strong to engage or release the higher stalling forces.

On a normal operating cycle, the mechanism will remain in the run stall position with the switches 9 and 44 closed until the thermostat 72 is satisfied. When this occurs, it deenergizes the solenoid 38 causing counterclockwise rotation of the lever 35 by spring 37. This movement of the solenoid lever 35 causes the pin 50 to engage surface 51 on the stalling member 30 and to rotate this member clockwise. This simultaneously moves the stalling surface 32 out of the path of the lug 31 and also moves the latch 16 into released position allowing the switchblade 11 to drop against cam 8 thus opening the compressor switch 9. This same motion of the lever also causes pin 42 to engage switchblade 43 and thus open the blower switch 44. Summarizing, opening of the room thermostat switch 72 deenergizes solenoid 38. This action releases the run-stop 30 and the latch 16 opening load switch 9 and also opening the blower switch 44.

The timing mechanism is now free to proceed back to the standby position where lug 41 on gear 6 engages the standby stalling surface 40 on solenoid lever 35. It is important on this point of the cycle that the run lug 31 on the gear 6 be clear of the stalling surface 40 on the lever 35. This is accomplished by limiting the inward motion of the stalling surface by a stop as provided by the edge of hole 52 in lever 35 engaging the shaft 24. Any other stop arrangement may, of course, be used. The "Run" lug 31 on gear 6 is located inwardly sufficiently that it never engages the Standby stalling surface 40 even when this surface is in stalling position. When the lug 41 engages surface 40, the stalling wheel 58 again engages the stalling lug 60 and stalls the timer motor 1.

It should be noted that there is only one point in the complete revolution of the timer cam where the load switch 9 can be closed. That is the point at which the cam follower surface 17 on switch blade 10 drops off the dropoff section on the cam. In order to effect switch closure, the latch 16 must be in place. If the latch happens to be held released at this time, the load switch will remain open and it will be necessary for the cam 8 to complete another complete revolution before the load switch can be closed.

If during a cycle either the high-pressure switch 74 or low-pressure switch 75 opens, it will break the circuit to the transformer 73 thus deenergizing the solenoid 38. This will have the same effect as dropping out of the solenoid 38 by the thermostat 72 as described. In other words, it will open the compressor motor switch stopping the compressor and will also release the run-stop so that the timer mechanism can proceed back to the starting point. However, at this time the timer motor is deenergized as it is in circuit with the switches 74 and 75. Thus the duration of the unfavorable condition causing opening of the safety switches is added to the delay in restarting the compressor.

FIG. 3 shows one type of operating cycle that my control may be arranged to provide. Here the timer motor speed and gear reduction are selected to give an overall cycle of one revolution in 7 minutes. The standby lug 41 on gear 6 is located relative to the dropoff section 22 on cam 8 so as to provide a 20 second delay between energization of the solenoid 38 and closure of the switch 9. The run stall lug 31 on final gear 6 is located so as to allow a period of 2 minutes after switch closure before the run lug 31 engages the run-stalling surface on lever 30. This leaves a balance of 4 minutes 40 seconds that the timer must run before it returns to the standby position in which lug 41 engages standby stalling surface 40.

With the cycle as above described, the timer will run for a period of 2 minutes after the compressor is started. Thus if the compressor runs the full 2 minutes before stopping, there will be a delay of 5 minutes before the compressor can be restarted. This is the sum of the 4 minute 40 second pressure equalization period plus the 20 second initial delay period.

If the system malfunctions and one of the safety switches 74 or 75 opens, for example 10 seconds after start, the timer must now run an additional 1 minute 50 seconds before the compressor can be started. In other words, the timer must now run 6 minutes 50 seconds instead of 5 minutes. In addition, the timer motor is deenergized during the period that the safety switch remains open and this indeterminate time is added to the delay imposed by the timer itself. Thus this system provides substantially longer delays in event of malfunction than during normal cycle providing only time enough for pressure equalization.

The 2 minute short cycle adder of course, can be made substantially longer, even as long as the average on period of the compressor in the system.

FIG. 4 shows an optional cycle in which the gearing is selected to provide a 5 minute revolution on the cam shaft. The cam is arranged to give a 15 second delay in starting and the run lug 31 arranged to stall the timer immediately after switch 9 closes. This gives a 4 minute 45 second interval for the timer to run to return to the standby position.

It will be seen that the duration of the short cycle adder can be made whatever desired simply by selecting the proper gear reduction and by locating the run-stall lug 31 at the proper angle on gear 6.

FIGS. 5 AND 6

In the embodiment of the invention shown in FIG. 1, the blower switch 44 is opened and closed by the solenoid 38. If desired, the blower switch 44 can be held by the timer until a predetermined period after the compressor is stopped. This arrangement is shown in FIG. 5 and the operation charted in FIG. 6. Here the pin 42' for operating switch 44 is carried by a separate lever 80 which is pivoted on the same bearing 36' as the solenoid lever 35'. The latch 16 and run stall member 30 are identical with FIG. 1 and are omitted from FIG. 5 for reasons of clarity. The lever 80 is biased counterclockwise by a spring 81 and carries a standby-stalling surface 82 adapted to be engaged by a stalling surface 83 carried on a cam 84 located between the cam 8 and the final gear 6'. A pin 85 carried by the solenoid lever 35' is arranged to engage a surface 86 on the lever 80, this pin causing clockwise rotation of the lever 80 when the lever 35' is rotated in the same direction by energization of the solenoid.

In operation, energization of the solenoid rotates the lever 35' clockwise which lifts the lever 80 releasing the pin 42' from switch 44 and also releasing the stalling surface 82 from the corresponding surface 83 on cam 84. The cam 84 will now hold lever 80 in this position until the timer rotates to the point where the dropoff portion 87 on the cam clears the cam follower surface of lever 80. At this time, the spring 81 is free to rotate the lever 80 clockwise opening switch 44 and also bringing the stalling surface 82 into position for stalling cam 84.

The arrangement shown in FIG. 5 has the advantage of maintaining the blower in operation in the event that the compressor is shut down by either safety switch 74 or 75. Operation of the blower at this time helps to remove the condition causing the shut down.

From the foregoing, it will be apparent that the invention provides an extremely simple compressor control system. Only one switch is required to give response to the thermostat and to provide starting of the compressor or load. In addition, the invention provides for control of the blower giving blower operation both before and after the compressor running cycle. In addition, the invention provides for extra delay in the event of short cycle, thus giving additional protection to the compressor. It will also be apparent that substantial changes in the operating cycle may be made as desired, simply by selecting the necessary gear reduction and locating the stall lugs at the proper locations on the final gear.

While a preferred form of the invention has been shown and described, many changes may be made without departing from the spirit and scope of the invention as defined in the following claims.

Claims

I claim:

1. In a control system for a refrigeration system having an electric motor driven compressor, the combination of, a condition responsive device, timing means including an electric timing motor for driving the same and an electromagnet, a control circuit including the condition responsive device and electromagnet whereby the electromagnet is controlled by said condition responsive device, an energizing circuit for the electric timing motor, said energizing circuit being independent of said condition responsive device, a switch for controlling the compressor motor, means including the timing means and the electromagnet for closing said switch in response to a call for condition change by the condition responsive device, said timing means being arranged to delay closure of said switch for a predetermined minimum time, means for mechanically stopping said timing means at a point providing said minimum time, said mechanical stopping means effectively stopping the timing means even though the electric timing motor remains energized by said independent energizing circuit, and means controlled by the condition responsive device including said electromagnet for rendering the mechanical stopping means ineffective and opening said switch when the condition responsive device calls for stopping the compressor.

2. The combination set forth in claim 1 in which a second condition responsive means breaks the energizing circuit for the electric timing motor and also deenergizes the electromagnet in response to an unfavorable condition associated with the refrigeration system, the duration of the unfavorable condition thus being added to said predetermined minimum delay.

3. The combination set forth in claim 1 in which the timing means provides a first delay period sufficient to allow equalization of pressure in the refrigeration system and an additional delay period in the event of a short cycle, said mechanical stopping means being arranged to allow operation of the timing means following starting of the compressor through said additional delay period and then to stop said timing means.

4. The combination set forth in claim 3 in which a second condition responsive means breaks the energizing circuit for the electric timing motor and also deenergizes the electromagnet in response to an unfavorable condition associated with the refrigeration system, the duration of the unfavorable condition thus being added to the delay provided by the timing means.

5. The combination set forth in claim 1 in which the refrigeration system includes a blower having a blower motor therefore, and a switch for the blower motor closed by said electromagnet in response to call for condition change by the condition responsive device.

6. In a control system for a refrigeration system having a compressor and a blower, a compressor motor for driving the compressor, a blower motor for driving the blower, a condition responsive means, an electromagnet, a control circuit including the condition responsive means and electromagnet whereby the condition responsive means controls the electromagnet, means including a compressor motor switch for controlling the compressor motor, means including a blower motor switch for controlling the blower motor, timing means including electric motor means, means for energizing said electric motor means, means actuated by the electromagnet for closing the blower motor switch on call for operation of the compressor by the condition responsive means, means including the timing means for causing closure of the compressor motor switch on call for compressor operation by said condition responsive means, said timing means being arranged to provide a delay between successive energizations of the compressor motor, means for stopping the timing means at a point providing said delay, means operated by the electromagnet on call for stopping of the compressor by the condition responsive means for opening the compressor motor switch, and means also operated by the electromagnet for rendering said stopping means ineffective, allowing the timing means to proceed with a new cycle.

7. The combination recited in claim 6 in which the blower motor switch is maintained closed by the timing means for a predetermined time following stopping of the compressor motor by said electromagnet.

8. The combination recited in claim 6 in which the timing means is restarted immediately following opening of the compressor motor switch by the electromagnet, and runs to a predetermined point, thereby shortening the delay before restart of the compressor during the time the compressor is stopped by the condition responsive means.

9. The combination recited in claim 6 in which the blower motor switch is maintained closed by the timing means until it has run for a predetermined length of time, and in which the energization of the electric motor means for the timing means is interrupted in response to an unfavorable operating condition associated with the refrigeration system.