EP0906888B1 - Device for preventing dripping of liquid from a dispensing orifice - Google Patents

Description

The invention relates to an arrangement for preventing Leakage of liquids from line openings. Such Lines are used, for example, at the Manufacture of semiconductor wafers on this Apply treatment fluids. Such lines (Elution units) are e.g. in etching devices, such as they are described in EP 0 444 714 B.

Another application of lines in which the Dripping should be prevented, for example Filling systems in the beverage industry.

With suggestions to solve the problem of dripping to take into account that the measures the constant Volume flow and the constant flow rate of the Liquid from the line must not impair and that both turning on and turning off the Liquid flow without (substantial) time delay must be done. The aim is that the line escaping liquid column tears off without dripping if for example, a shut-off device is closed. Dripping is undesirable because in the field of semiconductor technology individual Drops on the surface of a semiconductor wafer (Silicon wafers) an irregular process result would have. For example, a drop of an etching acid can be added lead to an undesirable etching trace. In the beverage industry the dripping is disadvantageous because the containers in which one Beverage is filled on the outside by dripping drink are soiled that they become unsightly (mostly juices are sticky!)

Various proposals have so far been made to solve the problem described. Valves are often used which suck back a small amount of liquid when closing. With a ¼-inch hose (inside diameter approx. 5 mm, cross section approx. 0.2 cm ² ), these valves (so-called suck-back valves) suck the liquid column back approx. 10 cm, which is approx. 2 ml liquid. With a volume flow of 2.5 l / min, a ¼ inch hose results in a flow rate of approx. 2 m / sec. Since silicon wafers are getting bigger (currently diameters up to 300 mm), an ever increasing volume flow is necessary for the treatment. Volume flows of up to 6 l / min are currently required. With a ¼-inch hose, this requires a flow rate of approximately 5 m / sec, which creates additional problems (high pressure loss in the line, severe delays in the flow of the liquid column when switching off). To avoid this, go to larger hose diameters (3/8 inch hose). Due to the larger hose diameter, the flow speed drops back to the original 2 m / sec. With a 3/8-inch hose (inner diameter approx. 8 mm, cross-section approx. 0.5 cm ² ), the suction volume of the suck-back valves only corresponds to a suction height of 4 cm. As a result, undesirable dripping occurs again and again with larger pipe cross-sections, together with the low suction height, regardless of the use of suck-back valves. This is particularly so because the meniscus that forms at the lower end of the liquid column due to the surface tension tilts, an air bubble moves upwards and drips liquid.

Another problem arises when conveying gases containing liquids, where it is already at a low level Volume flow despite the use of suck-back valves due to the formation of bubbles in the line for dripping is coming.

A dosing device is known from EP 402 535 B1 a valve, an adjustable piston and on the Outlet opening has a porous insert.

In the known device, the piston moves after the Closing the valve away from the outlet opening, so that in the Area of the outlet opening creates negative pressure To prevent liquid from exiting drip out.

In the DD 250 846 A3 there is a chamber valve for drip-free Closing liquid containers described, the of of the liquid to be dosed through a chamber Cuff is formed. The cuff is open Valve compressed (small interior of the chamber) and stretched when the valve is closed (large interior of the Chamber). In the chamber is created by enlarging her Volume when closing the valve (stretching the cuff) a negative pressure, causing the liquid from the Outlet opening is withdrawn.

The liquid remains with the valve according to DD 250 846 A3 in the chamber of the valve and / or in the area between Outlet opening and valve. Gassing liquids would drip this facility anyway.

In US 3,792,724 a filling system is described in which directly at the outlet opening of the line Facility is provided, which is in the field of Liquid remaining from the outlet opening Exhaust opening removed by suction. To do this here The outlet opening is made possible with a sieve covered, through which the liquid must flow.

The object of the invention is to provide an arrangement with which the dripping, even with high volume flow and / or when conveying liquids containing gas, is reliably prevented.

This task is solved with an arrangement with the Features of independent claim 1.

Preferred and advantageous embodiments of the invention are the subject of the subclaims.

With the invention, the above object is reliable solved and dripping from line openings in particular even with high volume flow and in the case of gas containing Liquids reliably prevented because of liquid sucked away immediately in front of the outlet opening of the line is so that liquid does not come out of the opening of the line can leak more (drip).

In a simple embodiment, the chamber is closed vacuum is applied in due course, around the Outlet opening arranged.

It is advantageous here if in the area of Outlet opening in the wall of the pipe over the circumference of the Line distributed several holes are provided through which Liquid under the effect of in the around the Exhaust chamber provided prevailing negative pressure is suctioned off.

In order to remove unwanted liquid in the area of the End of the line through the pressurized To prevent chamber, negative pressure will end up in the chamber the line is generated only when the promotion of Liquid has been stopped by the line (or just before), e.g. by the chamber only when the Shut-off device in the line which blocks the liquid flow interrupted by the line, applied with negative pressure becomes.

Aspirated through the chamber charged with negative pressure Liquid, which makes dripping reliable can be disposed of or the liquid cycle be fed again.

Further details, features and advantages of the invention result from the following description of the in the Embodiments of the invention shown in the drawings 1 shows a section of an arrangement according to FIG Invention, along the line B-B in Fig. 2, Fig. 2 Section along the line A-A in Fig. 1 and Fig. 3 a example embodiment of the circuit of the arrangement according to the invention.

1 and 2 is the outlet end of a (pipe) line 2 shown. Liquid comes out of line 2 through an opening 6 at the end. To the To control liquid flow through line 2 is at least one shut-off device (see FIG. 3) provided that for example as a suck-back valve is trained.

With a (short) distance from its end 6, the line 2 is one Device 1 assigned, which is used to prevent dripping Liquid from the outlet opening 6 to the line 2 prevent.

In the exemplary embodiment shown there is device 1 for aspirating liquid (drops) from a for example cylindrical, around the line 2 arranged housing 4, the one around itself around the line 2 extending chamber 3 limited. To the case 4 a line 5 is connected via which in the chamber 3 Vacuum can be generated. To this end, line 5 is connected a vacuum source (see. Fig. 3) connected, in which 5 shut-off devices leading to the vacuum source can be provided. In the wall of line 2 are in Area of the chamber 3 several through openings 7 (in In principle, a single through opening 7) is sufficient. The through openings 7 can be designed as perforations be so have a very small diameter. The Distance of the area in which the through openings 7 in the pipeline 2 are provided, from the outlet opening 6 the line 2 can be chosen arbitrarily small.

If the chamber 3 in the housing 4 with negative pressure is left, liquid residues that after the Stopping the liquid flow in line 2 in the area of the through openings 7 remain through which Through openings 7 in the chamber 3 and further through the Line 5 suctioned off. This is how liquid drips prevented from the outlet opening 6 of the line 2.

To prevent liquid coming out of the Outlet opening 6 should exit at the end of line 2 if e.g. an etching liquid on a semiconductor wafer is applied through the through openings 7 and Chamber 3 is sucked into line 5, line 5 and thus the chamber 3 only when needed, that is interrupted liquid flow is subjected to negative pressure.

Alternatively, measures can be provided with which the Passages 7 closed in the wall of line 2 when liquid flows through line 2. Such Measures can be shut-off devices, e.g. in shape a sleeve rotatable relative to the end of the line 2, in the holes are provided. If the sleeve is twisted like this, that the holes in the sleeve with the passage opening 7th align, the negative pressure in chamber 3 acts for suction of liquid residues.

A possible circuit, like the device 1 only when needed made effective, so the chamber 3 with negative pressure can be applied is shown in Fig. 3.

The liquid flows through line 2. Line 8 is a compressed air line that divides into two branches. The simultaneous shutdown of the liquid flow 9 in the Line 2 and switching on the vacuum in chamber 3 can be ensured in the following way. Over a Venturi nozzle 12 with the compressed air flow 11 in one Branch of the compressed air line 8 generates a suction stream 10 which the chamber 3 is subjected to negative pressure. The moment in which the valve 13 in the line 2 for the liquid flow switches off, the valve 14 opens for the suction flow 10. This with compressed air controlled valves by switching the Control air from one valve to another with a three-way valve 15 reached. The valve 13 for the liquid flow can, but does not have to be designed as a return valve. The Separation of gas and liquid, in the medium flow that of the device 1 with the chamber 3 comes in itself known way, e.g. through a droplet separator 16. The Exhaust air is led into the fume cupboard 17. Liquid becomes either disposed of via a line 18 or via a line 19 fed back to the liquid circuit.

In another embodiment of the invention (not shown) the negative pressure can be generated by a vacuum pump become. In this case, the suction flow is via its own Valve switched. The simultaneous switching off of the Liquid flow and switching on of the suction flow takes place in this case e.g. electric.

For both embodiments, the same applies Switching liquid flow and suction flow also on a period of time, e.g. delayed by a few seconds can be done. It is preferred that the suction of Liquid through the chamber 3 shortly before switching off the Liquid flow through line 2 is activated.

By side suction in the invention of the meniscus of the liquid column pointing downwards again and again newly formed, even if the meniscus "tilts" so that none Air bubble can arise, which migrates upwards and Liquid can drip.

In summary, an embodiment of the invention can be represented as follows:

To prevent liquid from dripping out of the outlet opening 6 to prevent a line 2 is the end of line 2 assigned a droplet suction device 1. The Drop suction device 1 has a housing 4, which the End of the line 2 surrounds forming a chamber 3. The Chamber 3 protrudes with the inside of line 2 Through openings 7 in connection and can be used for suction in the area of the outlet opening 6 after switching off the Liquid flow remaining through line 2 Liquid residues via a line 5 with negative pressure be charged. A circuit is proposed which only operates the droplet suction device 1, e.g. the chamber 3 pressurized when the Liquid flow through line 2 through line 2 assigned shut-off device is interrupted.

Claims (12)

1. Arrangement for preventing liquid dripping from the discharge opening (6) of a pipe (2) when the liquid flow in the pipeline (2) has been interrupted, a device (1) being provided in the region of the discharge opening (6) of the pipe (2), which device removes any liquid remaining in the region of the discharge opening (6) from the discharge opening (6) by suction, characterised in that the device (1) has a chamber (3) which can be subjected to low pressure and surrounds the pipe, said chamber being connected to the interior of the pipe (2) via at least one through-opening (7), which is disposed at a spacing from the discharge opening (6) of the pipe (2).
2. Arrangement according to claim 1, characterised in that the chamber (3) is provided at a spacing in front of the discharge opening (6) of the pipe (2).
3. Arrangement according to claim 1 or 2, characterised in that the chamber (3) is delimited by a housing (4) which is disposed in the region of the discharge opening (6) of the pipe (2).
4. Arrangement according to claim 3, characterised in that a pipe (5), which leads to a device (12) producing a low pressure, is connected to the housing (4).
5. Arrangement according to claim 3 or 4, characterised in that the chamber (3) and housing (4) are disposed round about the pipe (2).
6. Arrangement according to one of the claims 1 to 5, characterised in that a plurality of through-openings (7) is provided distributed over the circumference of the pipe (2).
7. Arrangement according to one of the claims 1 to 6, characterised in that the shut-off device (13) in the pipe (2) is connected operationally to a shut-off device (14) in the pipeline (5), which leads to the low pressure device (12) in such a manner that the shut-off device (14) provided in the low pressure pipe (5) is opened when the shut-off device (13) in the pipe (2) is closed.
8. Arrangement according to one of the claims 4 to 7, characterised in that the device, which produces the low pressure, is a device which has a venturi tube (12).
9. Arrangement according to one of the claims 4 to 8, characterised in that a droplet separator (16) is provided in the pipe (5) which leads to the low pressure device (12).
10. Arrangement according to claim 9, characterised in that a pipe (18), via which liquid is disposed of, emerges from the droplet separator (16).
11. Arrangement according to claim 9, characterised in that a pipe (19), via which liquid is re-supplied to the liquid circulation, emerges from the droplet separator (16).
12. Arrangement according to one of the claims 7 to 11, characterised in that a time delay member is provided in operational connection between the shut-off device (13) in the pipe (2) and the shut-off device (14) in the pipe (5) which leads to the low pressure device (12).

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