Protective device of auger type ice making machine

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a protective device of an auger type ice making machine, and more particularly, to a protective device of an auger type ice making machine which transfers ice frozen on an inner wall surface of a refrigeration casing while being scraped by an auger screw driven by rotation by an auger motor.

2. Description of the Prior Art

In a kitchen of a coffee shop, a restaurant or the like, ice making machines for making ice blocks of a required shape have been preferably used in accordance with the use and purpose, among which an auger type ice making machine for making small pieces of ice such as ice chips or flake ice continuously is available. In the auger type ice making machine, when an ice making operation starts in a state that ice making water is retained at a prescribed level inside a cylindrical refrigeration casing, the casing is forcibly cooled by a coolant circulating through an evaporation pipe connected to a refrigerating system so that the ice making water starts freezing gradually from the inner wall surface of the casing, thereby forming thin ice in layers. An auger screw is inserted in the refrigeration casing; the auger screw is driven by rotation by an auger motor so that thin ice frozen on the inner wall surface of the refrigeration casing is transferred upward while being scraped by the auger screw. The flake ice transferred by the auger screw is compressed so as to remove moisture in the process of passing through the pressing head provided inside the upper part of the refrigeration casing, thereby making compressed ice. The obtained compressed ice is released into and retained in a stocker.

In the auger type ice making machine, due to various factors during the ice making operation, a situation sometimes appears where the flake ice to be transferred by the auger screw cannot pass through the pressing head easily. If the ice making operation continues in this state, there are risks that all the ice making water inside the refrigeration casing freezes and that an overload is imposed in order to continue the rotation of the auger motor, finally causing the burnout or breakage of the auger motor itself, or the breakage of the ice making mechanism.

For this reason, an ice making machine is available which copes with the above-mentioned problems by providing a protective device for detecting the overload current of the auger motor so as to control the motor to stop (for example, see Japanese Examined Patent Publication (Kokoku) No. Hei 04-24625).

When a motor starts, a much larger current (starting current) flows in general compared with a case after shifting to steady operation. It is unpractical, however, to stop operating the motor every time a starting current larger than the current at steady operation flows. Therefore, the above-mentioned Japanese Examined Patent Publication (Kokoku) No. Hei 04-24625 is configured so that an operation signal to the auger motor is continuously output to the starting current so as to control the motor to stop based on the overload current which occurs during the operation after starting the auger motor.

Specifically, in the above-mentioned Japanese Examined Patent Publication (Kokoku) No. Hei 04-24625, a circuit for distinguishing between the starting current of the auger motor and an overload current at steady operation has to be provided, so that the configuration of the protective device becomes more complex, thereby increasing the risk that the device might have a trouble. It is also disadvantageous in that more expense is required for the production.

BRIEF SUMMARY OF THE INVENTION

The present invention, in view of the above-mentioned problems inherent in the protective device of the auger type ice making machine according to the prior art described above, is proposed to solve them in a favorable manner, and it is an object of the present invention to provide a protective device of an auger type ice making machine which can cope with the occurrence of a problem, with a simple configuration.

In order to overcome the above-mentioned problems and achieve the desired objectives, a protective device of an auger type ice making machine according to the present invention comprises:

a refrigeration casing which has an evaporator connected to a refrigerating system having a compressor on an external surface thereof, for freezing ice making water supplied inside on an inner wall surface thereof; an auger screw rotatably provided inside the casing, for scraping and transferring ice frozen on the inner wall surface of the casing; and an auger motor for driving the auger screw by rotation, configured so that the compressor is started so as to start an ice making operation after the auger screw is driven by rotation by the auger motor, wherein

protective means which starts abnormality monitoring simultaneously with the start of the compressor, for control the motor to stop when detecting a problem occurring at steady operation of the auger motor is provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing an auger type ice making machine in which a protective device according to a preferred embodiment of the present invention is employed;

FIG. 2 is an electric circuit diagram of the protective device according to an embodiment;

FIG. 3 is a timing diagram of a case in which the auger type ice making machine according to the embodiment is operated; and

FIG. 4 is a flow chart of a case in which the auger type ice making machine according to the embodiment is operated.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENT

Next, a protective device of an auger type ice making machine according to the present invention is described by way of a preferred embodiment with reference to the accompanying drawings.

FIG. 1 is a schematic diagram showing an auger type ice making machine according to the embodiment, which is configured so that an evaporation pipe 12 communicating with a refrigerating system as an evaporator is tightly wound around the perimeter of a cylindrical refrigeration casing 10 so as to cool the refrigeration casing 10 forcibly by circulating a coolant through the evaporation pipe 12 when an ice making operation is performed. Furthermore, ice making water is supplied from an ice making water tank (not shown) to the refrigeration casing 10 at a prescribed level so that the ice making water starts freezing gradually from the inner wall surface of the casing by cooling the refrigeration casing 10 forcibly as the ice making operation is started, thereby forming thin ice in layers.

An auger screw 14 is inserted in the refrigeration casing 10 so that a lower shaft 14a thereof is rotatably supported by a lower bearing 16 provided in a lower portion of the refrigeration casing 10 and an upper shaft 14b is rotatably supported by a pressing head 18 provided inside an upper portion of the refrigeration casing 10 so as to drive the auger screw 14 by rotation by an auger motor AM provided in a lower part of the ice making machine. The auger screw 14, in which a cutting blade 14c whose external diameter is slightly smaller than the internal diameter of the refrigeration casing 10 is spirally formed, is configured so that thin ice frozen on the inner wall surface of the casing 10 is transferred upward while being scraped by the cutting blade 14c of the auger screw 14 rotated by the auger motor AM.

The flake ice transferred upward while being scraped by the auger screw 14 is compressed so as to remove moisture in the process of passing through the pressing head 18, thereby making compressed ice. The obtained compressed ice is released into and retained in a stocker (not shown) provided above the refrigeration casing 10.

As shown in FIG. 1, the refrigerating system, which comprises a compressor CM and a condenser 20, is configured so that a high-temperature vaporized coolant (hot gas) compressed in the compressor CM flows into the condenser 20 through a pipe line 22. The liquefied coolant condensed in the condenser 20 flows into the evaporation pipe 12 through a capillary tube (not shown) and takes heat away from the refrigeration casing 10 by its vaporization so as to cool the refrigeration casing 10 down to zero or below. The vaporized coolant which has cooled the refrigeration casing 10 returns to the compressor CM from the evaporation pipe 12 through a pipe line 24 and subsequently, the cycle is repeated.

The pipe line 22 connecting the compressor CM with the condenser 20, which comprises a bypass pipe 26 going around the condenser 20, directly communicating with the evaporation pipe 12, is configured so that the vaporized coolant (hot gas) from the compressor CM can be supplied through the evaporation pipe 12 by switching a hot gas valve HV. Specifically, for example, even when the ice which has grown excessively by super cooling of the refrigeration casing 10 locks the rotation of the auger screw 14, by switching the hot gas valve HV to supply hot gas through the evaporation pipe 12, the heat thereof can remove the lock.

The auger type ice making machine comprises a controller 28 responsible for the overall electric control thereof, the auger motor AM, and a protective device 30 for protecting the auger screw 14 driven by rotation thereby or the like. FIG. 2 shows a major part of a protection circuit in which the protective device 30 of the embodiment is employed. A main base 32 connected to a power source bus and a control base 34 driven at a low voltage are electrically separated from each other by a transformer TR. A main power switch SW is inserted between a power supply line R connected to a power source of the main base 32 and a node D, and the compressor CM and a normally open contact X2-a of a relay X2 are connected in series between the node D and a power supply line T. Also, between the auger motor AM connected to the node D and a power supply line T, a normally closed contact X4-b of a relay X4, a shock relay MS as protective means and a normally open contact X1-a of a relay X1 are connected in series. It should be noted that a relay X3 is inserted in parallel with the auger motor AM between the node D and the normally closed contact X4-b and the relay X4.

The shock relay MS contains a current-voltage converter 36 for generating an output voltage in response to a change in the current of the auger motor AM (see FIG. 3), and has a function to control the auger motor AM to stop based on an output voltage from the current-voltage converter 36. Specifically, when an overload equal to or larger than a preset threshold value is applied to the auger motor AM during the ice making operation, the overload current flowing through the motor AM is detected by the current-voltage converter 36 in the shock relay MS as an overload output voltage. When the duration of the overload output voltage exceeds a shock time preset in the shock relay MS, the shock relay MS is energized so as to turn on (close) its cooperating normally open contact MS-a thereby stopping energization to the auger motor AM. It should be noted that the shock relay MS is configured so as to reset to its initial state (off of the normally open contact MS-a (open)) automatically after operating with the overload output voltage when the overload output voltage (overload current) is interrupted.

Between the node D and the power supply line T, a normally open contact X4-a of a relay X4 and a lamp L are connected in series. Also, between the normally open contact X4-a of the relay X4 and the power supply line T, a reset timer TM and the relay X4 connected to a normally closed contact TM-b of the reset timer TM in series are connected in parallel. It should be noted that the normally open contact MS-a of the shock relay MS is inserted between the node D and the normally closed contact TM-b of the reset timer TM, in parallel with the normally open contact X4-a of the relay X4. The reset timer TM functions as restart means for restarting the ice making machine after abnormal stop of the ice making machine (to be described later), in which a prescribed restart time (for example, 30 minutes) is set.

On the control base 34, the relay X1 for controlling the operation of the auger motor AM and the relay X2 for controlling the operation of the compressor CM are provided so that the relay X1 is excited by energization after turning on the main power switch SW when a prescribed condition is met (for example, float switch FS is on state). To the control base 34, the normally open contact X3-a of the relay X3 is connected, being set to put into a state that the relay X2 can be energized by turning on (close) the normally open contact X3-a. It should be noted that a delay timer DTM is mounted on the control base 34, the delay timer DTM being configured so as to start to count simultaneously with the start of the auger motor AM and to close a contact (not shown) inserted between the normally open contact X3-a of the relay X3 and the relay X2 in a prescribed period of time (for example, in 60 seconds), thereby energizing the relay X2 (see FIG. 3). Specifically, the delay timer DTM, during the period from energizing the relay X1 through until energizing the relay X2, in other words, during the period from starting the auger motor AM through until activating the compressor CM, functions to set a prescribed delay time. The delay time set in the delay timer DTM is set to be long enough to shift to steady operation after the auger motor AM starts so that the starting current of the motor AM is not detected by the current-voltage converter 36.

In the auger type ice making machine, a feedwater valve WV (see FIG. 4) which is on-off controlled by the float switch FS contained in the ice making water tank is provided, being configured so that ice making water is retained in the ice making water tank at a prescribed level so as to be supplied to the inside of the refrigeration casing 10 constantly at a prescribed level.

Next, a description is given for the action of the protective device of the auger type ice making machine according to embodiment hereinafter with reference to FIG. 3 and FIG. 4.

Step S1 in FIG. 4 turns on (ON) the main power switch SW so as to start the auger type ice making machine, shifting to Step S2, and the feedwater valve WV is turned on so as to start feeding water to the ice making water tank. Step S3 determines whether or not the float switch FS is turned on by the water level in the ice making water tank reaching a prescribed level. If the float switch FS is turned on (Step S3 affirmed (YES)), Step S4 turns off the feedwater valve WV, then shifting to Step S5, and the auger motor AM is started (ON). Specifically, in embodiment, the float switch FS is turned on and the relay X1 on the control base 34 shown in FIG. 2 is energized at the same time, its cooperating normally open contact X1-a is turned on (closed) so as to start energization to the auger motor AM. Energization to the delay timer DTM on the control base 34 is also started simultaneously by energizing the relay X3 so as to turn on (close) its cooperating normally open contact X3-a, thereby starting counting delay time (for example, 60 seconds). It should be noted that the relay X2 on the control base 34 is not energized and the compressor CM remains stopped in this case.

After the energization to the auger motor AM is started, the delay timer DTM counts up in Step S6, shifting to Step S7, and the compressor CM is started (ON). Specifically, the count up of the delay timer DTM energizes the relay X2 provided on the control base 34 so as to turn on (close) its cooperating normally open contact X2-a. Energization to the compressor CM is then started thereby starting an ice making operation (Step S8). Simultaneously, energization is started to the shock relay MS, the current-voltage converter 36 contained therein detects a change in the current from the auger motor AM to be monitored, and converts the change into a voltage change followed by outputting (Step S9). In Step S10, if no overload is applied on the auger motor AM, and if whether the output voltage from the current-voltage converter 36 is an overload output voltage according to the overload current of the motor AM is denied (NO), a steady operation continues without change.

As the ice making operation start, the refrigeration casing 10 is forcibly cooled by exchanging heat with a coolant circulating through the evaporation pipe 12, and the ice making water supplied from the ice making water tank to the refrigeration casing 10 freezes gradually from the inner wall surface of the casing, thereby forming thin ice in layers. The thin ice, before starting the compressor CM, is scraped and transferred upward by the cutting blade 14c of the auger screw 14 driven by rotation by the auger motor AM at the same time. The flake ice transferred by the auger screw 14 is compressed when passing through the pressing head 18 provided inside the upper portion of the refrigeration casing 10, and the obtained compressed ice is released into and retained in the stocker.

Step S11 determines whether or not the float switch FS-is turned off by the decrease in ice making water in the ice making water tank as the ice making operation continues. If the Step S11 is affirmed (YES), shifting to Step S12, the feedwater valve WV is turned on so as to start feeding water again. Step S13 then affirms (YES) that the float switch FS has been turned on, shifting to Step S14 so as to turn off the feedwater valve WV.

If a large mechanical load is applied on the auger motor AM during operating the auger type ice making machine for such a reason that the flake ice does not pass through the pressing head 18 any more or that ice is caught, the current flowing through the motor AM becomes an overload current which has exceeded the allowable value. The overload current is converted into an overload voltage in the current-voltage converter 36, thereby affirming Step S10 (YES). In this case, the operation shifts to Step S15 so as to stop the machine completely. Specifically, if the duration of the output voltage converted into an overload voltage in the current-voltage converter 36 exceeds a prescribed shock time, the shock relay MS is excited. The normally open contact MS-a cooperating with the shock relay MS is then turned on (close) so as to excite the relay X4. Its cooperating normally closed contact X4-b is turned off (open) so as to interrupt the energization to the auger motor AM thereby stopping the operation. Furthermore, since the relay X3 is demagnetized by turning off the normally closed contact X4-b thereby also turning off its cooperating normally open contact X3-a, the energization to the relay X2 is interrupted thereby turning off its cooperating normally open contact X2-b and consequently, the operation of the compressor CM is stopped. Specifically, the freezing of all the ice making water in the refrigeration casing 10 and the breakage or burnout of the auger screw 14 or auger motor AM caused by the overload thereon can be prevented previously.

It should be noted that the excitation of the relay X4 turns on (close) its cooperating normally open contact X4-a, thereby turning on the-lamp L for giving a visual alarm indicating that a problem occurs. The relay X1 remains excited and its cooperating normally open contact X1-a remains on in this case.

As the shock relay MS turns on the normally open contact MS-a, the energization to the reset timer TM is started, thereby starting counting set time, for example, 30 minutes. When the reset timer TM counts up (30 minutes later), the normally closed contact TM-b is opened so as to demagnetize the relay X4, and its cooperating normally closed contact X4-b is turned on again. As described above, since the normally open contact X1-a cooperating with the relay X1 remains on even when the machine is completely stopped due to the occurrence of a problem, the energization to the auger motor AM is started again by turning on the normally closed contact X4-b so as to start the motor AM. Then, similarly to the above, the delay timer DTM starts counting so as to excite the relay X2 60 seconds later, thereby turning on the normally open contact X2-a. The compressor CM is then started so as to start the ice making operation again automatically. Specifically, if the problem cause is solved during the period until the reset timer TM counts up, the operation of the auger type ice making machine can be started again automatically. For example, such a situation can be prevented that an ice making machine remains abnormally stopped outside business hours in a restaurant or the like without making ice, thereby running short of ice when opening.

Since the protective device 30 of the above embodiment is configured so that the protective device 30 is operated simultaneously the start of the compressor CM starting after the start of the auger motor AM so as to watch out for (abnormality monitoring) an overload current (overload output voltage) of the auger motor AM, means for distinguishing between the starting current of the auger motor AM and an overload current at steady operation does not have to be employed, thereby reducing the risk of causing troubles by way of simplifying the device 30. Also the simpler configuration can reduce the manufacturing cost.

In this case, as described above, the causes of the problem that the auger motor AM is overloaded, mostly arise after starting the ice making operation by the start of the compressor CM: for example, the flake ice transferred by the auger screw 14 does not pass through the pressing head 18 any more; and the ice overgrown by super cooling by the refrigeration casing 10 locks the rotation of the auger screw 14. This embodiment watches out for an overload current (overload output voltage) of the auger motor AM only during a period when such problems might occur. No unnecessary monitoring is carried out before the ice making operation when the above problems do not occur, so that the device configuration can be simplified.

Modified Embodiment

Although embodiment has described the configuration in which the current-voltage converter is contained in the shock relay as protective means, a configuration in which the converter is provided independently is also available. Furthermore, the protective means is not limited to the shock relay in embodiment, and another type of protective means may be employed as long as it can control the auger motor to stop by detecting the overload output voltage output from the current-voltage converter. Also, the time set in the reset timer or delay timer, being not limited to the numerical value in embodiment, can be changed to an optimal value according to use conditions and the like. It should be noted that the evaporator is not limited to the evaporation pipe as in embodiment, but a tubular body covering the refrigeration casing between which a coolant is supplied and other various configurations can be employed.

The object to be monitored by the protective means is not limited to the output voltage from the current-voltage converter, and the detected value (rotation speed) from the rotation detector for detecting the rotation speed of the auger motor may be monitored. If the ambient temperature around the installed auger type ice making machine is high, when the temperature of the refrigeration casing decreases down to a predetermined value after starting the compressor, the protective means may start abnormality monitoring (watching out for the output voltage from the current-voltage converter or the like). Specifically, if the ambient temperature is high, since ice is not made immediately after starting the compressor, abnormality monitoring is started without problems even although later than the start of the compressor.

As has been described above, since the protective device of the auger type ice making machine according to claim 1 of the present invention is configured so as to carry out abnormality monitoring simultaneously with the start of the compressor, means for distinguishing between the variation in overload current, rotation speed or the like occurring when starting the auger motor and the variation in overload current, rotation speed or the like at steady operation, does not have to be provided. Therefore, the risk of causing troubles can be reduced by simplifying the device. Also the simpler configuration can reduce the manufacturing cost.

Since the protective device of the auger type ice making machine according to claim 2 of the present invention is configured so as to watch out for an overload current of the auger motor simultaneously with the start of the compressor starting after the auger motor starts, means for distinguishing between the starting current of the auger motor and an overload current at steady operation does not have to be provided. Therefore, the risk of causing troubles can be reduced by simplifying the device. Also the simpler configuration can reduce the manufacturing cost.

Protective device of auger type ice making machine

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CPC

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