US2988099A

US2988099A - Fluid-operated control device

Info

Publication number: US2988099A
Application number: US710559A
Authority: US
Inventors: Langhans Ulrich
Original assignee: Leuna Werke GmbH
Current assignee: Leuna Werke GmbH; Leuna Werke Walter Ulbright Germany VEB
Priority date: 1957-08-08
Filing date: 1958-01-22
Publication date: 1961-06-13
Anticipated expiration: 1978-06-13

Description

June 13, 1961 u LANGHANS FLUID-OPERATED CONTROL DEVICE 2 Sheets-Sheet 1 Filed Jan. 22, 1958 June 13, 1961 LANGHANS 2,988,099

FLUID-OPERATED CONTROL DEVICE Filed Jan. 22, 1958 2 Sheets-Sheet 2 Tlql- INVENTOR (/1. /?/C// 1 mv /M/vs United States Patent "'ce FLUID-OPERATED CONTROL DEVICE Ulrich Langhans, Wansleben, Germany, assignor to VEB Leuna-Werke Walter Ulbricht, Merseburg, Germany Filed Jan. 22, 1958, Ser. No. 710,559 Claimsprioritnapplication Austria Aug. 8, 1957 4 Claims. '(Cl. 13782) The invention relates to a fluid-operated control device and more specifically to a pressure-sensitive control device actuated by a fluid under pressure.

A wide variety of electrical sensing devices and relays are available for process control. Their installation, however, is sometimes costly where explosive or corrosiveatmospheres are encountered in the chemical industry so that the electrical devices need special enclosures. Electrical instruments under such conditions require special maintenance and care, thus increasing the cost of operation. Pneumatic or hydraulic controls avoid many of these shortcomings.

It is the primary object of the invention to provide a control device which releases sudden changes in fluid pressure in a container when the pressure in another container gradually reaches predetermined maximum and minimum values respectively.

It is further an object of the invention to provide a device adapted to actuate a mechanical element when the pressure in a container reaches a predetermined value.

It is another object of the invention to provide such a device which will act instantaneously when a predetermined pressure is attained.

Other features and advantages of the present invention will be apparent from the following detailed descrip' tion thereof when considered in conjunction with the attached drawing in which like reference numerals in the several figures refer to the same or equivalent elements and in which FIG. 1 is a schematic vertical section of an embodiment of the invention, and

FIGQZ is a schematic vertical section of the same embodiment as shown in FIG. 1, as applied to a different purpose.

Referring now to the drawings, FIG. 1 shows an embodiment of a device of the invention as applied to the control of the liquid level in a storage tank. A flexible airtight membrane 2 is rigidly mounted in a container 1 which is thereby divided into two compartments. A baffie plate 3 is rigidly connected with membrane 2. A spring 23 theupper end of which is connected to frame 20 and thelower part of which is adaptedto abut against baflie plate 3 protects membrane 2 against excessive deflection by the upward movement of baffle plate 3. Pressure-sensitive resilient metallic bellows 4are fastened at their lower end to the frame 20 of the device whereas the upper end forms a stem which is equipped with a discharge nozzle 5 and is slidably mounted in a transverse member 21 of the frame 20. Two adjustable stops 6 mounted on the upper stem of bellows 4 and cooperating with transverse member 21 limit the axial upward and downward movements respectively of the bellows. A pressure-reducing device shown here as valve 8 supplies compressed air at constant pressure from a feed pipe 22 simultaneously to bellows 4 and to a pressure-actuated device, in this case to a pneumatically operated valve 7 biased by a spring towards the open position. A capil lary tube 9 restricts the rate at which air may flow from pressure-reducing device 8 to bellows 4. A tank 10 whose level is to be controlled by the device of the invention is equipped with a bubbling pipe 11 the outlet orifice of which is arranged below the minimum level to which the liquid in tank 10 is permitted to drop. Bubbling Patented June 13, 1961 pipe-11 is supplied with compressed air from feed line 22 through reducing valve 8 and through a capillary tube and needle valve 12, or communicates with the upper airtight compartment of container 1.

In operation of the aforedescribed device, liquid is admit-ted in the direction of the arrow through valve 7 into tank 10. As' the liquid level in the tank rises, the pressure increases in pipe 11 and therefore also in the upper compartment of container -1. The membrane 2 yields and is displaced downward, thereby moving baflle plate 3 towards nozzle 5. A At a predetermined hydrostatic pressure in tanicltl the gap between baflie plate 3 and nozzle 5 becomes sufiiciently small to interfere with the discharge of air from nozzle 5, the air pressure in bellows 4 increases and causes axialexpansion of the bellows. A tight seal is formed between nozzle 5 and baffle plate 3 and the full pressure for which reducing valve 8 is set is almost instantaneously brought to bear on bellows 4 and also on pneumatic valve 7, thereby shutting off the flow of liquid to tank 10.

When the level of liquid in tank 10 drops, the pressure in pipe 11 and therefore in the upper compartment of container 1 decreases. The membrane 2; moves upward and takes baflie'plate. 3 along. However, the nozzle 5 is not at once released from plate 3 and pressure remains high. Only when the lower stop 6 abuts against transverse member 21, will pressure in bellows 4 decrease, since agap will be formed between nozzle 5 and bafiie plate 3, which permits air to escape from bellows 4 leading to a drop in pressure therein and to their elastic contraction. The return spring in valve 7 then is able to open the valve against the suddenly reduced pneumatic pressure and a new cycle is started.

It can readily be appreciated that the maximum and minimum liquid levels in tank 10 can be set by suitably adjusting the two stops 6.

FIG. 2 illustrates on embodiment of the device of the invention as used for a pneumatic timing mechanism. A container 1 is divided by a flexible membrane 2 into two compartments. The upper compartment communicates with an airtight storage vessel 13 and through a capillary tube or needle valve 15 with a pneumatically operated pressure-release valve 16 which is spring-biased towards the closed position. Membrane 2 carries a baflie plate 3 which cooperates with a nozzle 5 connected to bellows 4 whose movements are limited by stops 6 abutting against transverse member 21 of frame 20. Membrane 2 is secured against excessive upward pressure of bafiie plate 3 by spring 23, the upper end of which is connected to frame 20 while the free lower end is adapted to abut againstplate 3. Bellows 4 andpneumaticvalves 7 and 16 are all supplied with compressed air through a capillary tube 9 from a pressure reducing valves connected to feed pipe 22. Storage vessel 13 is charged with compressed air from the 'valve 8 through a capillary tube or needle valve 14.

Vessel 13 is gradually charged with compressed air and the pressure from above on membrane 2 rises accordingly. When the pressure reaches a predetermined value, the membrane 2 pushes the bafiie plate 3 against nozzle 5 so as to interfere with the discharge of air from bellows 4 in the same manner as described in connection with the device of FIG. 1. The bellows expand suddenly and nozzle 5 is tightly sealed off. The resulting pressure increase in the line supplying air to bellows 4 causes valve 7 to close and valve 16 to open. Air then bleeds from vessel 13 through valve 16 at a rate determined by needle valve 15 until the pressure in vessel 13 drops to a predetermined minimum value. At this time, the lower stop '6 will abut against transverse member 21 and cause a gap to be formed between nozzle 5 and baflie plate 3, which permits air to escape from bellows 4 leading to a drop in pressure therein and to their elastic contraction. The pressure acting upon valves 7 and 16 drops, thus permitting valve 7 to open and valve 16 to close. A new cycle begins with the charging of vessel 13.

The time required for charging vessel 13 depends on the setting of needle valve 14. The time required for discharge of air from vessel 13 is controlled by needle valve 15. It is furthermore possible to adjust stops 6 for the maximum and minimum pressures at which the device of the invention will actuate valve 7. It is apparent that the timing cycle of the device can be varied readily with wide limits.

While the timing device of the invention is illustrated in FIG. 2 in connection with the opening and closing of a pressure-operated valve 7, it will be obvious to those skilled in the art that other pressure-sensitive devices of any kind may be actuated at predetermined intervals by the device of the invention.

While air pressure was shown in the illustrative examples to act upon the pressure-responsive membrane 2 and the pressure-responsive bellows 4 of the embodiment of the invention, it is within the scope of the invention to utilize the variations in pressure exerted by fluids of any kind to trigger the action of the control device. The pressure exerted by fluids other than air may be suddenly changed by the device of the invention and such change may be utilized to actuate devices of any kind such as electrical pressure switches, hydraulic motors, or the like.

Because of its simplicity and ruggedness, the control device of the invention permits maintenance-free operation over long periods of time. The moving parts do not require lubrication and are not impaired in their function by unfavorable environmental conditions.

It should be understood, of course, that the foregoing disclosure relates only to preferred embodiments of the invention and that it is intended to cover all changes and modifications of the examples of the invention herein chosen for the purposes of the disclosure, which do not constitute departures from the spirit and scope of the invention.

What is claimed is:

l. A pilot control device adapted to be connected by conduit means to a source of fluid operating pressure and to an apparatus similarly connected to said source, said pilot control device serving to control the pressure of said apparatus and comprising a housing, a flexible airtight membrane dividing said housing, said housing having an inlet opening at one side of said membrane, a baffie plate connected to said membrane on the side opposite from'said inlet opening and movable with said membrane in proportion to pressure in said inlet opening, a dividing wall extending across said housing in the region of said baffle plate and having an opening therein, a pressure sensitive expansible bellows on the side of said wall opposite said bafiie plate, said bellows having an inlet formed in one end to direct actuating fluid into said bellows and including on the other end an elongated tubular portion, said tubular portion being slidable in said opening and terminating in a nozzle opening directed towards said bafile plate, said actuating fluid being discharged through said nozzle opening against said bafile plate, the movement of said baffle plate being directed towards said nozzle opening upon an increase in pressure, thereby throttling the discharge through said nozzle opening to elfect expansion of said bellows, and stop members on said tubular portion located on each side of said dividing wall and being of greater size than said opening in said wall, whereby to control the amount of movement of said bellows in directions towards and away from said baflle plate, the expansion of said bellows causing said tubular portion to move in a direction towards said bafile plate and to completely seal otf said nozzle opening.

2. A pilot control device according to claim 1 including means to bias said baflie plate in a direction towards said nozzle opening.

3. A pilot control device according to claim 1 wherein said bellows is made of a metallic material immediately expansible upon restriction of flow from said nozzle opening to elfect sudden movement of said tubular portion in the direction of said baffle plate.

4. A pilot control device adapted to control pressure from a source by a pressure operated control means, the operation of an apparatus within predetermined pressure limits, said pilot control device comprising a housing having a partition wall with an aperture therein, reciprocable bafile plate means exposed to fluid pressure and reciprocable in response thereto, a pressure sensitive expansible bellows including a tubular portion at one end slidable in said aperture and'terminating in an opening directed toward said baflie plate means, means for directing actuating fluid into the opposite end of said bellows for discharge through said opening against said baflle plate means, said baflle plate means being movable toward said opening to restrict flow of said fluid therethrough upon increase in pressure, said bellows being thereupon expansible due to said increase in pressure, causing said tubular portion to move against said baffle plate means and to close off said discharge, and stop means on said tubular portion adapted to contact said wall and to limit movement of said bellows.

References Cited in the file of this patent UNITED STATES PATENTS 2,339,469 Emanuel Jan. 18, 1944 2,568,506 Mercer Sept. 18, 1951 2,695,030 Rice Nov. 23, 1954 2,760,511 Greeff Aug. 28, 1956 2,803,258 Dyson Aug. 20, 1957 2,833,411 Bosman et al May 6, 1958 FOREIGN PATENTS 888,226 France Dec. 7, 1943