JPH0914753A - Thermostat apparatus for liquid tank - Google Patents

Abstract

PURPOSE: To detect no-water burning along with easy operation and lower cost. CONSTITUTION: A heater unit 4 is arranged to stick downward from a bottom plate part 3 of the body 2 of the apparatus being extended into a liquid tank M to control a liquid L in the liquid tank M to a constant temperature. Especially, a temperature switch 5 integral with a thermosensible part and a contact part is mounted near the heater unit 4 on the top surface of the bottom plate part 3 to be connected in series to the heater unit 4 and opens a circuit C connected thereto when preset working temperatures Tsa and Tsb are reached.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a constant temperature device for a liquid tank which controls the temperature of the liquid in the liquid tank.

[0002]

2. Description of the Related Art Conventionally, there is known a constant temperature device for a liquid tank, which is attached to a liquid tank containing a liquid for keeping a heat-retaining object such as a test tube and controls the temperature of the liquid in the liquid tank.

This type of thermostat for a liquid tank is provided with a heater unit which projects downward from the bottom plate portion of the apparatus main body located above the liquid tank and faces the liquid tank, and is based on the temperature of the liquid detected by the temperature sensor. The current flowing through the heater unit is variably controlled, and feedback control is performed so that the temperature of the liquid maintains a preset target temperature.

Further, in this type of liquid bath thermostat, in order to prevent the liquid from being boiled when the liquid evaporates during continuous operation for a long time, the liquid level is detected by a float switch, or the heat generating portion of the heater unit is operated. It was equipped with an air-cooking prevention function that directly detects the temperature and shuts off the power supply to the heater unit based on the detection of the liquid level drop and the abnormal temperature rise of the heat generating part.

[0005]

However, the above-mentioned float switch may become undetectable when water stains, dust, etc. adhere, and when the temperature of the heat generating portion is directly detected, the temperature sensing portion Since a separate electric circuit or the like is required due to the separation of the contact point and the contact portion, the conventional thermostatic device for liquid tank has a problem that it cannot reliably detect empty cooking.

The present invention has solved the problems existing in such conventional techniques, and an object of the present invention is to provide a constant temperature device for a liquid tank which can reliably detect empty cooking and can be implemented easily and at low cost. .

[0007]

The present invention comprises a heater unit 4 which projects downward from the bottom plate portion 3 of the apparatus main body 2 and faces the liquid tank M, so as to control the temperature of the liquid L in the liquid tank M at a constant temperature. When the bath thermostat 1 is constructed, it is connected to the heater unit 4 in series on the upper surface of the bottom plate 3 and in the vicinity of the heater unit 4, and has a preset operating temperature T.
When the temperature reaches sa or Tsb, a temperature switch 5 having an integrated temperature-sensing section for opening the connected circuit C and a contact section is mounted.

In this case, according to the optimum embodiment, the temperature switch 5 is attached to the bottom surface portion 3a of the casing 10 of the apparatus main body 2 or the support plate 3b for supporting the heater unit 4 arranged below the casing 10 with a space therebetween. it can. Further, the temperature switch 5 can use a manual reset type using a bimetal.

[0009]

According to the liquid bath thermostat 1 according to the present invention, the upper surface of the bottom plate portion 3 of the device body 2 at normal temperature is at room temperature or a temperature slightly higher than room temperature. When the water vaporizes and becomes an empty cooked state, the heater unit 4
Since the entire temperature rises abnormally, the temperature of the bottom plate 3 located near the heater unit 4, specifically, the support plate 3b supporting the heater unit 4 and the bottom face 3a of the casing 10 located above this also rises. .

At this time, since a temperature switch 5 having an integral temperature sensing portion and a contact portion is mounted on the upper surface of the bottom plate portion 3 and in the vicinity of the heater unit 4, the temperature of the bottom plate portion 3 is equal to that of the temperature switch 5. When the operating temperatures Tsa and Tsb are reached, the circuit C to which the temperature switch 5 is connected is opened and the heater unit 4 is de-energized.

Since the temperature switch 5 is mounted on the upper surface of the bottom plate 3 in the vicinity of the heater unit 4, it can be basically assembled integrally with the apparatus main body 2 and connected in series with the heater unit 4. This is sufficient, and retrofitting is possible.
Further, the temperature switch 5 is protected from the waterproof surface against the liquid L in the liquid tank M by the presence of the bottom plate portion 3. Moreover, since the temperature switch 5 in which the temperature sensing part and the contact part using bimetal are integrated can be used, the cost can be reduced.

[0012]

Next, preferred embodiments according to the present invention will be described in detail with reference to the drawings.

First, the structure of the liquid bath thermostat 1 according to this embodiment will be described with reference to FIGS.

The thermostatic device 1 has a device body 2. A clamp 21 is provided at the bottom of the apparatus main body 2, and the thermostat 1 can be attached to and detached from the upper edge of the liquid tank M by the clamp 21. In this case, if the handle 22 is turned in one direction, the clamp 21 can be fixed by sandwiching the upper edge of the liquid tank M, and
If the handle 22 is rotated in the other direction, the clamp 21 can be loosened and removed. A liquid (water, antifreeze liquid, silicone oil, etc.) L is stored in the liquid tank M.

Further, 10 is a casing 10 of the apparatus main body 2.
The electric circuit board 23 is disposed inside. The casing 10 has a bottom surface portion 3a (bottom plate portion 3), and the lower surface of the bottom surface portion 3a supports the support plate 3b via the separators 24. As a result, the support plates 3b are arranged below and in parallel to the bottom surface portion 3a. As the support plate 3b, a stainless plate or the like having high heat conductivity is used. The clamp 21 is attached to the lower surface of the support plate 3b. Therefore, the clamp 21
Is attached to the upper edge of the liquid tank M, the apparatus main body 2 is
Located above.

On the other hand, the heater unit 4 is attached to the support plate 3b. As shown in FIGS. 1 and 2, the heater unit 4 has a heating portion 4h (see FIG. 3) made of nichrome wire or the like inserted inside a heater cover 25 made of a stainless steel pipe having high thermal conductivity. Then, the bent one is used. The heater unit 4 has a pair of vertical portions 4p and 4q, and has a two-turn circular coil portion 4r extending from the lower end of one vertical portion 4p to the lower end of the other vertical portion 4q.
Having. The heating section 4h is inserted inside the coil section 4r.

A horizontal mounting plate portion 26 is integrally provided at an intermediate position in the vertical direction between the vertical portions 4p and 4q. Mounting plate 2
6 has mounting holes 26c, 26c shown in FIG. 2, and the mounting plate portion 26 utilizes the mounting holes 26c, 26c to support plate 3b.
Screw. As a result, the heater unit 4 projects downward from the support plate 3b, the coil portion 4r faces the liquid tank M, and the upper ends of the vertical portions 4p and 4q penetrate the bottom surface portion 3a and reach the inside of the casing 10. Then, the wirings connected to both ends of the heat generating portion 4h are led out from the upper ends of the vertical portions 4p and 4q. The reason for providing the support plate 3b is to prevent heat conduction from the heater unit 4 to the casing 10.

In FIG. 1, 27 is a temperature sensor for detecting the temperature of the liquid L. Although not shown, a stirring mechanism for stirring the liquid L and the like are provided.

On the other hand, according to the present invention, the temperature switch 5 is attached on the upper surface of the bottom surface portion 3a and near the heater unit 4. In this case, the mounting position of the temperature switch 5 is
Directly above the mounting plate portion 26 and between the vertical portions 4p and 4q (see FIGS. 1 and 2). As the temperature switch 5, a temperature switch using a bimetal that is small and inexpensive and capable of passing a large current is used. The temperature switch 5 has a temperature sensing part and a contact part which are integrated, and has a function of turning off (opening) when a preset operating temperature Tsa is reached, and a manual reset type, that is, once the operating temperature Tsa is reached. Once off (open), use the type that holds the off (open) state unless manually reset. Since the temperature on the upper surface of the bottom surface portion 3a under normal conditions is room temperature or slightly higher than room temperature, the operating temperature Tsa of the temperature switch 5 can be set to about 50 ° C.

Further, one connection end of the temperature switch 5 is connected to a wiring connected to one end of the heat generating portion 4h led out from the vertical portion 4p, and the other connection end of the temperature switch 5 and the vertical portion 4q. The wirings connected to the other end of the heat generating portion 4h derived from are connected to the electric circuit board 23, respectively (see FIG. 1).

Next, the circuit configuration of the electric system will be described with reference to FIG. In the figure, 30 indicates an electric circuit in the thermostatic device 1. Reference numeral 31 is a power supply plug having a ground pin, and one power supply line 33a is connected to one plug pin of the power supply plug 31 via the circuit protector 34, and the other power supply line 33b is connected to the other plug pin. Further, between the power supply lines 33a and 33b, a surge absorber 35, a drive motor 36 such as an agitator, etc.
And, the series circuit of the float switch 37 and the relay coil 38 is connected respectively. Furthermore, the power supply line 33a
A relay switch 39, an SSR (current control element) 40, the temperature switch 5 and a series circuit of the heat generating portion 4h are connected between the control unit 41 and the switch 33b. Then, the SSR 40 and the temperature sensor 27 are connected to the control unit 41.

Next, the operation and function of the thermostatic device 1 according to this embodiment will be described with reference to FIGS.

First, when power is supplied from the power plug 31 to the electric circuit 30, a current flows through the series circuit of the float switch 37 and the relay coil 38, and the relay switch 39.
Turns on. Thereby, the relay switch 39, the SSR
40, the temperature switch 5, and the heat generating portion 4h, a current flows, and the heat generating portion 4h generates heat, whereby the liquid L is heated.
On the other hand, the temperature of the liquid L is detected by the temperature sensor 27,
The control unit 41 controls the SSR 40 to perform feedback control of the temperature of the liquid L so that the temperature of the liquid L reaches a preset target temperature.

On the other hand, it is assumed that the float switch 37 becomes undetectable and the liquid L in the liquid tank M is evaporated to be in an empty state. In this case, since the heating portion 4h has an abnormal temperature rise, the temperature of the entire heater unit 4 also rises. As a result, the temperature of the mounting plate portion 26 of the heater unit 4, the support plate 3b, and the bottom surface portion 3a of the casing 10 facing the support plate 3b rises accordingly. Then, this temperature rise is detected by the temperature switch 5, and when the rise temperature reaches 50 ° C. which is the operating temperature of the temperature switch 5, the temperature switch 5 is turned off (open) and the connected circuit C is cut off. . That is, the power supply to the heater unit 4 is stopped. Since the temperature switch 5 is a manual reset type, it remains in the OFF (open) state even if the temperature of the bottom surface portion 3a falls again.

FIG. 4 shows the temperature change characteristics of each part with respect to the elapsed time in the case of the state of being boiled, where Ph is the heat generating part 4
The temperature change characteristic of h (coil portion 4r) and Pa are the temperature change characteristic of the bottom surface portion 3a detected by the temperature switch 5.
As is clear from the figure, the heat generating part 4
The temperature of h rises to about 850 ° C., and the temperature of the bottom surface portion 3a reaches 50 ° C. after about 10 minutes. In this way, even if the function of preventing the idle cooking is disabled due to an abnormality, it is possible to reliably prevent the idle cooking.

Next, a thermostatic device 1 according to a modified embodiment of the present invention will be described with reference to FIG.

In the modified embodiment, the temperature switch 5 is attached to the upper surface of the support plate 3b. Although the upper surface of the support plate 3b is more disadvantageous than the upper surface of the bottom surface portion 3a from the viewpoint of a waterproof surface, it can be realized by, for example, attaching a cover for covering the temperature switch 5. The modified embodiment can be implemented in the same manner as the basic embodiment except that the mounting location of the temperature switch 5 is different from the basic embodiment shown in FIGS. In addition, Pb in FIG. 4 shows a temperature change characteristic of the support plate 3b. In the case of the modified embodiment, since the temperature rise of the support plate 3b becomes faster than the temperature rise of the bottom surface portion 3a, for example, the temperature switch 5
Even if the operating temperature Tsb is set to 100 ° C., the power supply to the heater unit 4 can be stopped in about 5 minutes.

The embodiment has been described in detail above.
The present invention is not limited to such an embodiment.
For example, the constant temperature control includes not only the constant temperature of the liquid but also the concept of changing the temperature according to a preset pattern. Further, as the temperature switch, a temperature switch based on a principle other than the illustrated example can be used. Furthermore, in the embodiment, the thermostat and the liquid tank are separate types, but the thermostat and the liquid tank may be integrated. In addition, the detailed configuration, shape, method, and the like can be arbitrarily changed without departing from the scope of the present invention.

[0029]

As described above, according to the present invention, a constant temperature device for a liquid tank, which controls the temperature of the liquid in the liquid tank by providing a heater unit projecting downward from the bottom plate portion of the apparatus main body to face the liquid tank, Connect the temperature switch, which is connected to the heater unit in series on the upper surface of the bottom plate, in series with the heater unit, and opens the connected circuit when the preset operating temperature is reached, with the temperature sensing unit and contact unit integrated. Because I installed it,
It has a remarkable effect that it can surely detect the empty cooking and can be performed easily and at low cost.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing a main part of a thermostat for a liquid tank according to the present invention,

FIG. 2 is a partial cross-sectional plan view of a heater unit in the constant temperature device for the same liquid tank,

FIG. 3 is a circuit diagram of an electric system in the constant temperature device for the liquid tank,

FIG. 4 is a temperature change characteristic diagram of each part when an abnormality occurs in the constant temperature device for the liquid tank,

FIG. 5 is a side sectional view showing a main part of a constant temperature device for a liquid tank according to a modified embodiment of the present invention,

[Explanation of symbols]

 1 Liquid bath constant temperature device 2 Device body 3 Bottom plate part 3a Bottom part 3b Support plate 4 Heater unit 5 Temperature switch 10 Casing M Liquid tank L Liquid Tsa Operating temperature Tsb Operating temperature C circuit

Claims (5)

[Claims] 1. A constant temperature device for a liquid tank for controlling the temperature of a liquid in a liquid tank by providing a heater unit which projects downward from a bottom plate portion of an apparatus main body and faces the inside of the liquid tank. In the vicinity of the heater unit, a temperature switch that is connected in series to the heater unit and that opens a connected circuit when a preset operating temperature is reached is integrated with a temperature sensing unit and a contact unit. A constant temperature device for liquid tanks. 2. The constant temperature device for a liquid tank according to claim 1, wherein the bottom plate portion is a bottom surface portion of a casing of the apparatus main body. 3. The constant temperature device for a liquid tank according to claim 1, wherein the bottom plate portion is a support plate for supporting a heater unit which is arranged below the casing in the apparatus main body with a space therebetween. 4. The thermostat for a liquid tank according to claim 1, wherein the temperature switch uses a bimetal. 5. The constant temperature device for a liquid tank according to claim 1, wherein the temperature switch uses a manual reset type.