GB1597655A - Extractor pump for fluids under vacuum - Google Patents

Description

(54) EXTRACTOR PUMP FOR FLUIDS UNDER VACUUM (71) I, VACLAV FERES, a citizen of the Federal Republic of Germany, of 14 Haidund Neu-Strasse, 7500 Karlsruhe 1, Federal Republic of Germany, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention is concerned with a pump for the extraction of fluids from a vacuum enclosure into an enclosure at a higher pressure, the pump having a housing, at least one pressure outlet pipe, a wheel or impeller disc which rotates in the housing, and to which the fluid is fed through a feed pipe in an axial direction, and means of propulsion situated on the wheel, extending between this latter and the wall of the housing.

Extraction of fluid from vacuum enclosures into enclosures which are at higher pressures plays a significant role especially in chemical processing industry. Many processes take place only in a vacuum. If these processes are carried out continuously, provision must also be made for continuous extraction of the fluid; in most cases extraction takes place against atmospheric pressure. Special difficulties arise if the fluid to be extracted is at boiling point, and therefore contains bubbles of vapour.

If the usual forms of fluid pump are used for such purposes, provision must be made for a feed height which will balance the pressure difference.

In order to reduce this large feed height, fluid ring pumps are used. In this case there is a ring of fluid round the wheel which provides a permanent seal between the enclosure at low pressure and the enclosure at high pressure. To the wheel which generates this fluid ring, there are attached one or more vanes, which provide the actual propulsion.

Since the fluid ring rotates with the wheel, the fluid becomes heated through friction, with the consequence that the rate of exhaustion increases, especially if the fluid is initially nearly at its boiling point. In addition, formation of bubbles of vapour and of gas leads to undesirable cavitation. The fluid removed must be replaced by fresh fluid and the fluid ring must be cooled by bringing in of the fluid being moved, with the consequence that these pumps always require a not inconsiderable minimum quantity of material. The pumps also require a definite feed height of more than 0.5 m. Finally, these pumps are not suitable for use in the high vacuum region (from a few Torr to about 10-2 Torr).

In addition, positive displacement pumps, are known to be used for the purpose indicated. In these cases also, a substantial minimum quantity of material is necessary for a fixed feed height, since otherwise air penetrates due to leaks at the joints. None of these pumps can be operated dry. For this reason these pumps also need a control drive or an adjustment of level for control of the quantity of material being moved, and in addition, reverse valves on the pressure side.

Nevertheless, these pumps have the advantage that they can also be used for high vacua, where their life is of course satisfactory only if the fluid being propelled has lubricating properties.

For viscous liquids and thick suspensions, locks are also provided, which do not however have any propulsive effect.

The aim of the invention is the production of an extraction pump for use on fluids under vacuum, in which the quantity of material moved is automatically and reliably adapted to the quantity arriving and which maintains the static pressure difference at zero feed quantity, and which propels boiling liquids and liquids containing gases continuously without any feed height and without cavitation.

This aim is fulfilled in a pump of the kind to which the invention relates by ensuring that each propulsion means includes a siphon connected in an airtight manner with the suction space of the impeller disc and having a transport channel in which the fluid is led outwardly and then inwardly of the disc to an exit opening, the suction space of the impeller disc being connected with the gas cushion of the vacuum enclosure and being in sealed relationship with respect to the non-rotating parts of the pump housing.

The siphon-like shape of each individual rotating transport channel ensures that the axially moving fluid is accumulated in the region of the guide tube in a similar manner to a U-tube with unequal arms, such that a definite height of fluid is set up in one section of the transport channelcomparable with the longer arm of the U-tube. From the end of the other section of the transport chan nel-comparable with the shorter arm of the U-tube-the fluid is discharged, so that the difference in height between the discharge edge and the accumulated liquid in the other section of the transport channel alters the pressure difference between the vacuum space on the one hand and the high pressure space to which the fluid passes on the other.

The quantity of material arriving can be minimal, and in particular transport is possible practically in the form of droplets. Since the fluid is placed under pressure by rotation outwards in a practically isolated transport channel which is only over the exit openings leading to the housing, there is a pressure increase in a radial direction, with the consequence that any vapour bubbles present in the fluid are condensed and gas bubbles are absorbed. This leads to avoidance of the cavitation which is to be feared.

In addition, the pump in accordance with the invention has the advantage that there is no encircling water ring, which could lead to heating and hence to higher rates of exhaustion and de-gassing. The pump is suitable for both low and high vacuum use. For starting up, the pump only needs to be half full, since then the transport channels fill up automatically from the suction side. The pump then adapts itself automatically to any subsequent desired quantity of flow.

In accordance with a preferred aspect each transport channel consists of a tubular component arranged approximately radially to the wheel, and a cup-shaped component over the opening of this tube. This form is particularly simple to manufacture and to use, and is therefore sure in operation. In comparison with positive displacement pumps, this pump has the substantial advantage that no problems of airtightness arise, and hence that the necessary close manufacturing tolerances for the positive displacement pump are not required.

When the pump is to be used for extraction of fluids which contain solid particles, the invention provides that the transport channels are provided with an opening with a small clearance, which can be closed when required, in the region of their vertices which encircle the wall of the pump housing and guide the fluid. Due to centrifugal force the solid particles in the fluid accumulate in the region of the reversal locations and can leave through the small openings into the housing space. The clearance is so chosen that the fluid located near to the reversal location does not escape. The openings can also be closable, so that they are only opened from time to time when the solid particles are small.

The invention will now be described further, by way of example only, with reference to the accompanying drawings in which: Fig. 1 is a diagram illustrating the working principle of the pump; Fig. 2 is an axial section on line II--II of Fig. 3 through a preferred form of pump; Fig. 3 is a section taken on line III--III of Fig. 2; Fig. 4 is an axial section taken on line IV-IV of Fig. 5 of another embodiment of the invention; Fig. 5 is a section taken on line V-V of Fig. 4; Fig. 6 is an axial section on line VI-VI of Fig. 7 through a third embodiment of the invention;; Fig. 7 is a radial section taken on a line corresponding to line VIl-VIl of Fig. 6, the upper and lower halves of the drawings showing different forms of the invention; Fig. 8 is an axial section through an embodiment having an openable peripheral closure; and Fig. 9 shows a modification of the arrangement shown in Fig. 8.

Referring now to the drawings, the structure has a vacuum enclosure 1 and an enclosure 2 at a higher, for example atmospheric, pressure. Enclosure 1 can, for example, be a vacuum evaporator or the like. The complete extractor pump, labelled 3, is arranged between the vacuum enclosure 1 and the enclosure 2. It has a housing 4 with a feed pipe 5 and a schematically represented pressure pipe 6. In addition, the pump has an impeller disc 7, which is rotated by a shaft 9 driven by a motor 8. The impeller disc 7, together with its suction space 11, is made airtight against the rotating parts of the housing 4 by means of a seal 20. The impeller wheel 7 has a number of transport channels 10 which extend to the periphery, the channels 10 each being, in principle, constructed in the form of a U-tube. The channels 10 have a section 12 extending outwardly from the suction space 11 of the impeller disc 7, a reversal location 13 at the periphery of the impeller disc, and finally an unwardly directed section 14, section 14 terminating in an exit opening 15.

On rotation of the impeller disc 7, fluid contained in the vacuum enclosure 1 moves through the feed pipe 5 to the suction space 11, and due to centrifugal acceleration such fluid is pressed into transport channels 10. A column of fluid is then built up in each transport channel 10 in accordance with the principle of communicating tubes, the fluid accumulation in section 14 of the transport channel being determined by the exit opening 15 at radius R, whilst the fluid accumulation in section 12 of the transport channel 10 is set to a different value; ie radius r, according to the pressure difference between enclosure 1 and enclosure 2. This difference in accumulation of fluid ie (R-r) is indicated by h on the drawing. It is ensured in all cases that there is always a fluid barrier in each transport channel 10, so that no air can enter.A particularly even and reliable continuous transport is attained when the suc tlon space 11 is connected with the gas cushion of vacuum enclosure 1 by means of a connector 16, so that the pressure is the same in both enclosures.

The reference numerals used in Fig. 1 for the essential parts of the pump are adopted in the following description of some practical embodiments of the invention and in related figures of the drawings. In the embodiment shown in Figs. 2 and 3, the housing 4 of pump 3 comprises two covers 41, 42, the drive shaft 9 passing into housing 4 through cover 41, and the impeller disc is fixed to the drive shaft 9 by means of a screw 17. The impeller wheel 7 also has a hub 18 which extends about the shaft 9, which by means of a seal 19 makes the pump space airtight at the driving side thereof. The impeller disc has an axial suction space 11, into which the feed pipe 5 extends, such pipe passing through the housing cover 42. The impeller wheel 7 of the pump is made airtight in relation to the other housing cover 42 by a seal 20.The suction space 11 is connected to the gas cushion of the vacuum closure, not shown in Fig. 2, by means of the connector 16.

In the example illustrated, the impeller wheel 7 has six regularly spaced transport channels 10 extending from the periphery thereof, there being two different forms of the invention shown in Fig. 3. In one form each transport channel 10 consists of a tubular section 101 connecting the exterior to the suction space 11, and a cup-shaped cap 102 screwed at 103 to a cylindrical extension 104 of the impeller. The cap 102 includes a plurality of exit openings 105 drilled in the wall thereof. If the pump is to be used for the transport of fluids containing solid particles, the cup-shaped part 102, the radial extremity 110 of which rotates near to the wall of the housing 4, is provided with an opening 111 of small clearance, so that the solid particles leave towards the exterior to be extracted from the outer side of the rotating transport channel 10 via the pressure tube 6.

An alternative form of transport channel 10 is shown in the right hand upper part of Fig. 3. The impeller disc 7 has a tubular part 106 leading to the exterior, but in this case the cap 107 is mounted on the end of the channel by means of individual distance pieces 108, so that an exit opening is produced in the form of an open ring 109.

In the arrangement shown in Figs. 4 and 5, the housing 4 is formed in like manner to that of the embodiment shown in Figs. 2 and 3. The pressure-balancing connector 16 is, however, taken through the feed pipe and has an axially extending tubular part 21 which extends to the suction space 11 of the impeller 7. In this embodiment the impeller 7 comprises two discs 71, 72, fixed together by means of screws 70. The discs 71 and 72 are held apart by spacers 112 located on at least one disc. In the example shown, the spacers 112 have a wave-shaped profile, consisting of two straight sections 113, 114, the radially inner ends of which are joined by a connecting piece 115 and a curved section 116 having an inwardly turned end 117. The transport channels are of rectangular crosssection, and are formed by and between the spacers and the opposed faces of the two discs 71, 72.The fluid can leave between the inwardly turned end 117 and the adjacent radial section 113. The wave-shaped spacers may either by provided between the two discs 71, 72 as profile sections, or may be cast as part of the front face of one of the discs.

Two similar embodiments are shown in Figs 6 and 7. In this case also the impeller consists of two discs 73, 74, the transport channels 10 being formed by spacers cast into the front surface 75 of one disc 74. In the upper part of Fig. 7 the spacers each comprise a curved section 118, extending from the suction space 11 to the outer periphery of the disc, and a shorter section 119 arranged in spaced parallel disposition relative thereto, there being a vertex 120 extending from curved section 118 to overlie the end of the channel in spaced disposition relative thereto and which extends peripherally and radially inwardly of the disc to a radius R. In the modification shown in the lower part of Fig.

7 part 120 is bent again to form an outwardly extending section 121 arranged in spaced parallel relationship with respect to the end of section 118 so that an exit channel is formed between the two curved sections 118 and 121. The two discs 73, 74 are again connected by means of screws 76.

Fig. 8 shows an embodiment of the invention in which the impeller 7 comprises three disc-shaped parts 77, 78, 79. The section of the transport channel leading from the feed space 11 to the exterior is formed between one of the discs 77 and the middle disc 78, as shown by 12 in Fig. 1, whilst the other section 14 is formed between the other outer disc 79 and the middle disc 78. The middle disc 78 is of smaller diameter than the two outer discs 77, 79, with the consequence that an overflow channel 80, separated from the pump enclosure by an adjustable ring 81 is formed at the periphery. This ring 81 can, as shown at the upper part of Fig. 8, be pushed onto the outer disc 79, so that the overflow channel is open to the outside and any solid matter collecting there can leave the system.

In this embodiment extraction of materials collecting in the disc 79 is carried out through a draw tube 82.

The embodiment of the invention shown in Fig. 9 also comprises an impeller 7 made up from three discs 83, 84, 85, which are, in general, constructed in a similar manner to those of the embodiment shown in Fig. 8. In this case a form of elastic O-ring 81 serves as a closure for the perimeter side of the overflow channel 80, which is positioned so as to form a seal on the rolling wheel discs at the appropriate place. The elasticity of this O-ring 81 can be so selected that at a determined pressure increase in the transport channel it lifts up, so that solid particles can leave, thus providing a self-cleaning effect.

WHAT I CLAIM IS: 1. A pump for extracting fluids from a vacuum enclosure into an enclosure at a higher pressure comprising a housing, at least one pressure outlet pipe, an impeller disc rotating in the housing, to which the fluid travels axially through a feed pipe, and with propulsion means on the impeller disc extending between the feed pipe and the walls of the housing, characterised in that each propulsion means includes a siphon connected in an airtight manner with the suction space of the impeller disc and having a transport channel in which the fluid is led outwardly and then inwardly of the disc to an exit opening and the suction space of the impeller disc being connected with the gas cushion of the vacuum enclosure and being in sealed relationship with respect to the nonrotating parts of the pump housing.

2. A pump as claimed in claim 1, characterised in that the impeller possesses an axially disposed volume which forms the suction space, in which the feed pipe of the pump is introduced axially.

3. A pump as claimed in claim 1 or 2, characterised in that each transport channel consists of a tubular component approximately radially disposed with respect of the impeller disc and a cup-shaped component overlying such component.

4. A pump as claimed in claim 1 or claim 2, characterised in that the transport channels are bent in the plane of rotation of the impeller disc.

5. A pump as claimed in claim 4, characterised in that the impeller disc comprises two coaxially arranged interconnected discs, almost filling the housing and having opposed faces at least one of which there is provided spacers of equal height and leading outwards and then being turned to lead inwards, adjacent spacers and the opposed faces of the discs forming a transport channel of substantially rectangular cross-section.

6. A pump as claimed in claim 5, characterised in that close to the outer periphery of the discs the spacers are bent in the shape of an arc to form a vertex which reverses the direction of flow of the fluid.

7. A pump as claimed in any one of the claims 1 to 6, characterised in that the transport channels are provided with an opening of small clearance in the region of a vertex which diverts the fluid close to the wall of the housing of the pump.

8. A pump as claimed in claim 1 or claim 2, characterised in that the impeller comprises three discs the middle one of which is of smaller diameter than the two outer discs so as to form an overflow channel which controls the direction of flow of the fluid, and that the discs are maintained in spaced relationship by spacers at opposing surfaces of the discs, the said spacers defining the transport channels therebetween.

9. A pump as claimed in claim 8, characterised in that the space between the two outer discs is made airtight by means of a detachable ring.

10. A pump as claimed in claim 9, characterised in that the ring comprises an elastic material automatically displaceable from an operative position when the pressure in the space between the two outer discs reaches a predetermined value.

11. A pump for extracting fluids from a vacuum chamber and delivering the same to a chamber at a higher pressure substantially as hereinbefore described with reference to and as illustrated in the various figures of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (11)

**WARNING** start of CLMS field may overlap end of DESC **. shown at the upper part of Fig. 8, be pushed onto the outer disc 79, so that the overflow channel is open to the outside and any solid matter collecting there can leave the system. In this embodiment extraction of materials collecting in the disc 79 is carried out through a draw tube 82. The embodiment of the invention shown in Fig. 9 also comprises an impeller 7 made up from three discs 83, 84, 85, which are, in general, constructed in a similar manner to those of the embodiment shown in Fig. 8. In this case a form of elastic O-ring 81 serves as a closure for the perimeter side of the overflow channel 80, which is positioned so as to form a seal on the rolling wheel discs at the appropriate place. The elasticity of this O-ring 81 can be so selected that at a determined pressure increase in the transport channel it lifts up, so that solid particles can leave, thus providing a self-cleaning effect. WHAT I CLAIM IS:

1. A pump for extracting fluids from a vacuum enclosure into an enclosure at a higher pressure comprising a housing, at least one pressure outlet pipe, an impeller disc rotating in the housing, to which the fluid travels axially through a feed pipe, and with propulsion means on the impeller disc extending between the feed pipe and the walls of the housing, characterised in that each propulsion means includes a siphon connected in an airtight manner with the suction space of the impeller disc and having a transport channel in which the fluid is led outwardly and then inwardly of the disc to an exit opening and the suction space of the impeller disc being connected with the gas cushion of the vacuum enclosure and being in sealed relationship with respect to the nonrotating parts of the pump housing.

2. A pump as claimed in claim 1, characterised in that the impeller possesses an axially disposed volume which forms the suction space, in which the feed pipe of the pump is introduced axially.

3. A pump as claimed in claim 1 or 2, characterised in that each transport channel consists of a tubular component approximately radially disposed with respect of the impeller disc and a cup-shaped component overlying such component.

4. A pump as claimed in claim 1 or claim 2, characterised in that the transport channels are bent in the plane of rotation of the impeller disc.

5. A pump as claimed in claim 4, characterised in that the impeller disc comprises two coaxially arranged interconnected discs, almost filling the housing and having opposed faces at least one of which there is provided spacers of equal height and leading outwards and then being turned to lead inwards, adjacent spacers and the opposed faces of the discs forming a transport channel of substantially rectangular cross-section.

6. A pump as claimed in claim 5, characterised in that close to the outer periphery of the discs the spacers are bent in the shape of an arc to form a vertex which reverses the direction of flow of the fluid.

7. A pump as claimed in any one of the claims 1 to 6, characterised in that the transport channels are provided with an opening of small clearance in the region of a vertex which diverts the fluid close to the wall of the housing of the pump.

8. A pump as claimed in claim 1 or claim 2, characterised in that the impeller comprises three discs the middle one of which is of smaller diameter than the two outer discs so as to form an overflow channel which controls the direction of flow of the fluid, and that the discs are maintained in spaced relationship by spacers at opposing surfaces of the discs, the said spacers defining the transport channels therebetween.

9. A pump as claimed in claim 8, characterised in that the space between the two outer discs is made airtight by means of a detachable ring.

10. A pump as claimed in claim 9, characterised in that the ring comprises an elastic material automatically displaceable from an operative position when the pressure in the space between the two outer discs reaches a predetermined value.

11. A pump for extracting fluids from a vacuum chamber and delivering the same to a chamber at a higher pressure substantially as hereinbefore described with reference to and as illustrated in the various figures of the accompanying drawings.