JPH0310399Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field This invention relates to an oil diffusion pump used to obtain a relatively high degree of vacuum.

Conventional technology Conventionally, when obtaining a high vacuum of 10 ^-4 mmHg or less,
In an oil diffusion pump that uses an oil rotary pump as an auxiliary pump, it is known to provide a trap for storing liquefied gas such as liquid nitrogen or liquid oxygen on the intake passage side of the main body of the oil diffusion pump to increase the ultimate degree of vacuum.

That is, as shown in FIG. 2, a liquefied gas storage trap 22 is interposed on the intake passage 21 side of the pump main body 20 of the oil diffusion pump.

A liquefied gas such as liquid nitrogen or liquid oxygen is injected into the trap 22 from a liquefied gas supply passage 23 formed of a low temperature resistant steel pipe (for example, a stainless steel pipe).

The liquefied gas storage trap 22 consists of a practical capacity space into which liquefied gas is injected, and a surplus space formed above this practical capacity space.When the highest liquid level of the liquefied gas exceeds the level of the practical capacity space, The liquefied gas is configured to overflow from the overflow passage 24 into a container 25 made of expanded polystyrene.

A temperature sensor 26 made of, for example, a thermocouple is inserted into the container 25 made of styrofoam, and the temperature sensor 26 detects the liquefied gas that has overflowed into the container 25, so that the liquefied gas in the trap 22 reaches its maximum level. It is controlled to detect when the liquid level has been reached and stop the injection of liquefied gas.

Therefore, the trap 25 is activated by the temperature sensor 26.
The liquefied gas is constantly stored in the trap 22 by intermittently injecting the liquid up to the highest liquid level again after a predetermined period of time (for example, 30 minutes) has elapsed since the highest liquid level in the trap 22 was detected and injection was stopped. controlled to do so.

Problems to be Solved by the Invention In the conventional oil diffusion pump described above, the temperature sensor 26 is set at a position relatively far from the liquefied gas storage trap 22, that is, the Styrofoam container 25 is placed outside the overflow passage 24.
Since the temperature sensor 26 inside the trap is configured to detect the highest liquid level inside the trap 22,
Poor response and large amount of liquefied gas overflow.
In other words, there is a problem in that a lot of liquefied gas is wasted and there is a high risk of burns to workers.

This idea was made to solve the above-mentioned conventional problems.It improves the response when detecting the highest liquid level in the trap, suppresses the amount of liquefied gas overflow, and reduces unnecessary consumption and burns to workers. The purpose of the present invention is to provide an oil diffusion pump that can avoid such dangers.

Means for Solving the Problems The oil diffusion pump according to this invention has a temperature sensor installed in the overflow passage of a liquefied gas trap installed on the intake passage side of the pump body of the oil diffusion pump. .

Function: When the liquefied gas comes out into the overflow passage, the temperature sensor drops to the temperature of the liquefied gas, thereby detecting that the liquefied gas has overflowed.

Embodiment FIG. 1 is a sectional view schematically showing an embodiment of this invention, in which an oil diffusion pump 1 has a pump main body 1
A and an intake passage 1 leading to a vacuum container (not shown)
Diffusion pump oil 2 is housed in the bottom of the pump main body 1A.

An inner cylinder 3 with both upper and lower ends open is installed and erected in the pump main body 1A, a rectifying lid 4 is provided above the opening at the upper end of the inner cylinder 3, and the lower end is immersed in the diffusion pump oil 2.

Reference numeral 5 denotes a liquefied gas storage trap, which is interposed on the intake passage 1B side of the pump main body 1A in order to increase the degree of vacuum achieved. The liquefied gas storage trap 5 includes a liquefied gas supply passage 6 formed of a low temperature resistant steel pipe such as a stainless steel pipe, and an overflow made of the same material inserted into the liquefied gas supply passage 6 in a double pipe type. The passages 7 are connected to each other.

When liquefied gas such as liquid nitrogen or liquid oxygen is supplied from the liquefied gas supply passage 6 into the liquefied gas storage trap 5 and the highest liquid level of the injected liquefied gas exceeds the level of the practical capacity space of the trap 5. The overflowing liquefied gas is discharged from the overflow passage 7 into a container 8 made of Styrofoam.

Reference numeral 9 denotes a temperature sensor consisting of a thermocouple made of, for example, a platinum resistor, and is connected to the overflow passage 7.
It is installed by inserting it into the outlet section of the 10 in the diagram
11 is a communication path to an oil rotary pump (not shown), and 12 is a water jacket.

Next, the operation of the above configuration will be explained. Activate the oil rotary pump communicating with the communication path 11,
A low vacuum state is secured in advance, and the diffusion pump oil 2 in the pump body 1A is heated by the heat source 10.

As a result, the diffusion pump oil 2 is evaporated, and the vapor is ejected and diffused into the pump body 1A from the gap between the upper end opening of the inner cylinder 3 and the rectifying lid 4, thereby connecting the gas molecules remaining in the intake passage 1B. It is introduced into the passage 11 and exhausted.

On the other hand, liquefied gas such as liquid nitrogen or liquid oxygen is injected into the liquefied gas storage trap 5 from the liquefied gas supply passage 6, and the highest liquid level of the liquefied gas exceeds the level of the practical capacity space of the liquefied gas storage trap 5. At this point it is discharged through an overflow channel 7 into a Styrofoam container 8.

In this way, the state of liquefied gas and discharge from the overflow passage 7 is quickly detected by the temperature sensor 9 inserted at the outlet of the overflow passage 7, and the supply of liquefied gas to the liquefied gas storage trap 5 is stopped. let Therefore, the amount of overflow of liquefied gas can be suppressed to a small level.

Effects of the invention As explained above, according to this invention, the temperature sensor is installed in the overflow passage of the liquefied gas storage trap, and the distance between the temperature sensor and the liquefied gas storage trap is shortened, resulting in improved responsiveness. Since the supply of liquefied gas can be promptly stopped in the event of an overflow, it is possible to prevent wasteful consumption of liquefied gas and dangers such as burns to workers.

[Brief explanation of drawings]

FIG. 1 is a sectional view schematically showing an embodiment of this invention, and FIG. 2 is a sectional view of a conventional example. DESCRIPTION OF SYMBOLS 1... Oil diffusion pump, 5... Liquefied gas storage trap, 7... Overflow passage, 9... Temperature sensor.

Claims (1)

[Scope of utility model registration request] An oil diffusion pump characterized in that a temperature sensor is installed in an overflow passage of a liquefied gas storage trap interposed on the intake passage side of a pump main body of the oil diffusion pump.