Device for maintaining overpressure in a liquid-filled container

Abstract

 Device for maintaining overpressure in a liquid-filled container, in which the temperature of the liquid, so its volume, and the external pressure to which the container is subjected, can vary. The overpressure serves for keeping water out and should have a reasonably constant value in order to prevent overload of shaft sealings. The device comprises a foot portion (1) and an upper cover (2) its circumferential edges (6, 12) being spaced apart and connected to one another by a circumferentially extending membrane (8) made of a flexible material such as rubber, so that the distance between the foot portion (1) and the upper cover (2) can vary. The foot portion, the membrane and the upper cover define an expansion space which is connected to the container. At least one spring (19, 20) pushes the upper cover towards the foot portion so that the oil in the expansion space and the container is kept under a certain over-pressure.

Description

[0001] The invention relates to a device for maintaining overpressure in a liquid-filled container, in which the temperature of the liquid and the external pressure to which said container is subjected, can vary, said device comprising: a foot portion and an upper cover having its circumferential edges spaced apart and being connected to one another by a circumferentially extending membrane manufactured from a flexible material such as rubber, so that the distance between the foot portion and the upper cover can vary, and a closed expansion space that can be connected to said reservoir is situated between said foot portion, the membrane and the upper cover, at least one spring being present for pushing the upper cover towards the foot portion so that the oil in the expansion space and the container connected to it, are kept under a certain overpressure.

[0002] A device of the type described above is shown in NL-A-1012940. There, in particular a pump driven by an electric motor, said pump being mounted in the suction pipe of a trailing hopper dredge is contemplated.

[0003] The electric motor is completely filled with oil. During operation of the motor or by atmospheric condtions, the temperature of the oil can increase and thus the oil will expand.

[0004] Further, the suction pipe, and therefore the pump having the electric motor, can be located at various depths under water. Maintaining a certain overpressure of the oil in the electric motor is desirable for preventing water from penetrating into it, which would damage the motor. The overpressure should have a low, reasonably constant value in order to prevent the shaft sealings of said electric motor from getting overloaded.

[0005] The device described above is employed for accommodating the volume increase and keeping the overpressure almost constant.

[0006] Manufacturing such a device has proven to cause certain problems and is therefore relatively expensive. In order to be able to maintain a sufficiently uniform pressure on moving said foot portion and said upper cover towards and away from one another, one necessarily has to use a number of springs. These are incorporated in pairs in five guide bushes being connected to said upper cover and extending towards said foot portion and being closed at the side of the upper cover. A rod extends through each guide bush connected with the foot portion, and has its other end provided with a support plate engaged by the pair of springs. The other end of the pair of springs engages a flange ring connected to the guide bush being located near the foot portion.

[0007] In order to prevent one or more bushes from getting clamped onto the support plate on movement of the upper cover in relation to the foot portion, the bushes should be mounted very accurately on the appropriate position in the upper cover. Namely, the axis of the rod to which the support plate is connected, should coincide exactly with the axis of the bush concerned. However, the welding operations can easily cause deviations in the dimensioning.

[0008] Further, the bolt holes provided in the circumferential edge of the upper cover, for connecting the circumferentiale edge to one edge of the membrane, should be exactly aligned with the bolt holes in the foot portion to which the other edge of the membrane will be connected.

[0009] Now the object of the invention is to change the device in such a way, that manufacture thereof is substantially facilitated and the cost of the device can be reduced almost by half.

[0010] According to the invention, this object is achieved in that the foot portion comprises a base plate, centrally provided with a pin extending square to it, across which a bush is slidable, having its end nearest to the base plate connected with a support plate extending parallel to the base plate and being connected to the upper cover, for supporting springs mounted around the bush and having their other sides connecting a pressure plate being centrally supported by a sleeve screwed onto the pin and being provided with an internal threading.

[0011] This yields a simple structure, in that only one single support plate is present, being engaged by all springs and being supported only in the middle by said sleeve. The ends of the springs can be laterally supported by outwardly protruding edges provided on the support plate and the pressure plate.

[0012] Here, the upper cover can easily be rotated in relation to the foot portion, so that the connection with the edges of the membrane will never cause difficulties.

[0013] In order to enable easy rotation of the sleeve on the pin, the sleeve is provided with a bolt head and a bearing is located between the bolt head and the pressure plate.

[0014] In particular, it can be provided for, that the membrane manufactured from rubber or a like flexible material consists of two identical parts being connected to one another at their longitudinal edges. Manufacturing such a membrane in this way is much simpler, as a result of which the membrane is much cheaper.

[0015] The invention is further explained by way of an embodiment shown in the drawing, in which:

Fig. 1 illustrates schematically a vertical cross-section of a device according to the invention, taken along line I - I in Fig. 2; and

Fig. 2 illustrates schematically part of the plan view of the device according to Fig. 1.

[0016] The device shown in the drawing comprises two main portions, namely a foot portion and an upper cover 2. The foot portion 1 is constituted by the base plate 3 having the pin 4 centrally mounted therein and a raised edge 5 extending along the outer circumference thereof and being provided with the flange edge 6. The flange edge 6 is connected, in a way not further described, to the edge 7 of a membrane 8, which e.g. can be made of rubber or a like flexible material. The membrane 8 comprises two identical portions 9 being connected to one another at their longitudinal edges 10.

[0017] The other circumferential edge 11 of the membrane 8 is connected to a flange edge 12 of the upper cover 2, a flange edge 13 being located between the parts 11 and 12, being connected to a support plate 15 by a conical part 14. The conical part 14 contains openings 16.

[0018] The support plate 15 is provided with a bush 17 being supported by gussets 18 and being slidable on the pin 4 of the foot portion 1. Support plate 15 is provided with protruding edges, not further indicated, for laterally supporting the ends of a number of springs 19 and 20 located within one another. At the other side, the springs 19, 20 engage a pressure plate 21, likewise provided with protruding edges, which is centrally supported by a sleeve 22, provided with an internal thread, being screwed on the pin 4. The sleeve 22 is provided with a bolt head 23 for rotating it, and a bearing 24 is located between said bolt head 23 and the pressure plate 21.

[0019] For filling the device with oil and connecting it to the electric motor, not illustrated, a connecting piece 25 is provided, and the upper cover is provided with a venting plug 26 at its highest point.

[0020] For protecting the membrane 8, an annular plate 27 comprising two or more parts is mounted around the raised edge 5 of the foot portion 1, said plate being connected to the flange edge 6 of the foot portion 1. The circumferential edge of the plate 27 is connected to a standing plate 28. Plates 27 and 28 are provided with openings which are small to prevent solid parts contained in the water from damaging the membrane 8.

[0021] The upper cover is correspondingly provided with an annular plate 29 with a circumferential plate 30 fitting around plate 28. When moving the upper cover 2 away from the foot portion 1, the circumferential plate 30 will provide for, that the protection of the membrane 8 will remain guaranteed, in that the free circumferential edge of the circumferential plate 30 can not end up lying beyond the circumferential edge of the plate 28. This is indicated with dash lines in the left part of Fig. 1, which also illustrates the maximum distance across which the upper cover 2 of the foot portion 1 can be situated.

[0022] Depending on the temperature of the oil in the device and in the container, not illustrated in the drawing, in which the electric motor is located, a certain amount of oil will be under a certain pressure within the device. In case of an increase or decrease in temperature of the oil, the upper cover 2 will move away from and towards the foot portion 1, respectively, while the oil is kept under a certain overpressure by the influence of springs 19 and 20.

[0023] In order to achieve the desired oil pressure in the device at a certain temperature of the oil, the appropriate amount of oil will have to be brought into the device. To that end, a temperature scale 32 is mounted on an indicator 31 being arranged at the base plate 3 of the foot portion 1, said scale cooperating with an indicating strip 33 being mounted to the plate 29 connected to the upper cover 2. When the temperature indicated by the indicating strip 33 on the temperature scale 32 corresponds to the temperature of the oil in the device, the upper cover 2 will be located at the appropriate distance from the foot portion 1 and the appropriate amount of oil will be located within the device. At the same time, the temperature scale 32, together with the indicating strip 33, can serve to check if oil leakage has occurred.

[0024] Hoisting points 34 have been provided for being able to transport the device in a reliable way.

[0025] It will be obvious, that only one possible embodiment of a device according to the invention has been illustrated in the drawing and described above and that many changes can be made without departing from the scope of the invention as it has been indicated in the accompanying claims.

Claims

1. Device for maintaining overpressure in a liquid-filled container, in which the temperature of the liquid and the external pressure to which said container is subjected, can vary, said device comprising: a foot portion (1) and an upper cover (2) having its circumferential edges (6, 12) spaced apart and being connected to one another by a circumferentially extending membrane (8) manufactured from a flexible material such as rubber, so that the distance between the foot portion (1) and the upper cover (2) can vary, and a closed expansion space that can be connected to said reservoir is situated between said foot portion (1), the membrane (8) and the upper cover (2), at least one spring (19, 20) being present for pushing the upper cover (2) towards the foot portion so that the oil in the expansion space and the container connected to it, are kept under a certain overpressure, characterized in that the foot portion (1) comprises a base plate (3), centrally provided with a pin (4) extending square to it, across which a bush (17) is slidable, having its end nearest to the base plate (3) connected with a support plate (15) extending parallel to the base plate and being connected to the upper cover (2), for supporting springs (19, 20) mounted around the bush (17) and having their other sides connecting a pressure plate (21) being centrally supported by a sleeve (22) screwed onto the pin (4) and being provided with an internal thread.

2. Device according to claim 1, characterized in that the sleeve (22) is provided with a bolt head (23) for rotating it, while a bearing (24) is located between said bolt head (23) and the pressure plate (21).

3. Device according to claim 1 of 2, characterized in that the membrane (8) manufactured from rubber or a like flexible material comprises two identical parts (9) being connected to one another at their longitudinal edges (10).

Drawing