Screw pump

Abstract: In a worm pump for thick media and/or media containing lumps, e.g. meat in pieces, of the kind comprising a) a tubular housing (7) with an inlet (6) and an outlet (13), b) a worm rotor (8) rotatably supported in the housing (7), and c) a worm-gate assembly (14) comprising a number of gate members (15) adapted during the rotation of the worm rotor (8) to protrude into and follow the latter's convolutions (9) and thus prevent the medium being pumped from following the rotation of the worm rotor, the novel feature is d) that the worm-gate assembly (14) comprises a number of loose gate members (15) slidingly supported in an endless track (16,17), of which a substantially rectilinear portion (18) extends alongside and parallel to the worm rotor (8).

Description: TECHNICAL FIELD The present invention relates to a worm pump of the kind set forth in the preamble of claim 1. BACKGROUND ART Worm pumps of the kind referred to above are known from DE-A-3,408,967. As will be seen from Figure 2 of this document, the loose gate members 10 are guided in a track housing 5, the latter being capable of pivoting outwards about a pin 14 to allow maintenance work to be done. This arrangement makes the gate members 10 accessible for removal, cleaning and/or replacement, but this has to be done through the narrow gap, through which the track housing 5 normally communicates with the tubular worm housing 2. Likewise, internal cleaning of the track housing 5 has to be done through this narrow gap, not being made easier by the presence of a guide wheel 7 for the gate members 10 and its shaft 6. DISCLOSURE OF THE INVENTION It is the object of the present invention to provide a worm pump of the kind referred to initially, that does not suffer from the disadvantages referred to, and this object is achieved with a worm pump, according to the present invention also exhibiting the features set forth in the characterizing clause of claim 1. With this arrangement, the inside of the track housing including the loose gate members lying in the endless track are easily accessible upon opening of the lid or cover. Preferably the relevant parts of the pump are oriented in the manner set forth in claim 2, ensuring that the loose gate members will not fall out upon opening of the lid or cover. GB-A-824,798 describes a pump having many features in common with the pump according to the present invention. Thus, the features set forth in items a, b, parts of items c-c4 and parts of items d-d2 in claim 1 of the present invention may be found in this pump. There are, however, significant differences: A. The pump of GB-A-824,798 is intended for pumping hydraulic fluid, in contrast to both the pump of the present invention and that described in DE-A-3,408,967 mentioned above, the text in the first paragraph on page 10 clearly indicating its use for pumping thick media and/or media containing lumps. Thus, the need for frequent opening and cleaning is considerably less. B. In the pump of GB-A-824,798, that part 12 of the endless track, through which the loose gate members 11 pass while co-operating with the helical convolutions on the worm 6, is constituted by a channel on the inside of the pump housing. This makes it difficult to remove the loose gate members 11, such as for cleaning and/or replacement, for which reason such a pump is unsuitable for use with foodstuffs, normally requiring frequent and thorough cleaning. C. In the pump of GB-A-824,798, the endless track is limited inwardly not solely by the inner part of the guide member 19, but also by a part of the main section of the housing proper. D. In the pump of GB-A-824,798, the track housing 14 consists of two side plates 15 separated by the central plate 19, all assembled in a manner not facilitating dismantling by means of screws 18, further screws 17 securing the track housing 14 to the main section 1. It appears from the sectional view in Figure 2 of this document that the track housing 14 can only be opened by unscrewing at least the upper screws 17, and then unscrewing the five screws 18, leaving the central plate 19 and most of the gate members in the form of the discs 11 lying loose upon the lower side plate 15. BRIEF DESCRIPTION OF THE DRAWING In the following detailed portion of the present description, the present invention will be explained in more detail with reference to the stuffing machine for meat mass shown on the drawing, said machine comprising an exemplary embodiment of a worm pump according to the invention, whereas Figure 1 shows the machine in side elevation and partly in section, the track housing for the gate members being shown as viewed in the direction of the arrow í I in Figure 2, and Figure 2 shows the machine as viewed from the outlet end, i.e. corresponding to viewing the machine in the direction of the arrow II in Figure 1. The stuffing machine shown in the drawing, designed for processing meat mass (not shown) or the like, consists in a manner known in principle of two main parts, viz. a filling-in hopper 1, and a worm pump 2. In a manner known per se, the hopper 1 is provided with a movable cover 3, in the closed position shown fitting closely to the hopper 1, so that the latter may be evacuated by means of known equipment (not shown), e.g. a vacuum pump. A supply worm 4 is adapted to rotate about a vertical axis, being supported and driven by a motor assembly 5. The reason for using the term "supply worm" is that it is adapted to supply the meat mass (not shown) being present in the hopper 1 to the worm pump 2, viz. through the latter's inlet 6. The worm pump 2 a consists of stationary tubular housing 7, in which the pump's worm 8 is rotatably supported. As will be evident from Figure 1, the convolutions 9 of the worm 8 are shaped like a channel having a generally semi-circular shape as seen in a longitudinal sectional view through the worm 8. The worm 8 is adapted to be driven counter-clockwise as viewed in Figure 2 by means of a drive assembly 10 consisting of a motor 11 driving a gear box 12, e.g. a planetary gear box, preferably in such a manner that the worm 8 may be driven with different speeds from 0 to 100 rpm. This is based on the worm 8 having a diameter of the order of magnitude 20-30 cm. During the rotational movement of the worm 8, the meat mass having been introduced through the inlet 6 by means of the supply worm 4 will be conveyed to an outlet 13. This conveying will, of course, depend on the meat mass not rotating together with the worm 8, as if so, there would not occur any cooperation between the meat mass and the convolutions 9 in the manner known e.g. from small meat mincers, in which the part corresponding to the tubular housing 7 is shaped with longitudinal grooves on the inside. To make it quite certain that the meat mass does not rotate together with the worm 8, the worm pump 2 is additionally provided with a worm gate assembly 14 consisting of a number - in the example shown sixteen - gate members in the form of unconnected disks 15 being guided in an endless track in an elongated track housing 16, viz. between the latter's outer wall and an internal guide 17 situated at a substantially constant distance from the outer wall, with the exception of a rectilinear track portion 18, at which the track housing 16 is in open communication with the inside of the tubular housing 7, the internal guide 17 on this side extending parallel to the worm 8. As will be evident from Figure 2, the track housing 16 is in the form of a flat tray or pan, closed in a fluid-tight manner by a removable cover 19, so that the endless track, in which the disks 15 are guided, is also delimited by the bottom of the track housing 16 and by the cover 19. The inside of the tubular housing 7 and the inside of the track housing 16 communicate with each other through a slot 20, through which the disk 15 can protrude into the housing 7 and engage the convolutions 9 in the worm 8. Since the disks 15 are constrained by the housing 16 and the latter's cover 19 to move in a plane at least being parallel with the axis of the worm 8, these disks will, when the worm rotates, be moved towards the outlet 13, and in all parts of this movement between the point of initial engagement with the worm 8 and the point of disengagement, they provide a highly effective obstruction for meat mass, that could otherwise tend to follow the rotation of the worm 8 and hence not be moved towards the outlet 13. Thus, during the rotation of the worm 8, the disks 15 will be constrained by the endless track in the housing 16 to move as if they were parts of an endless chain, even though they are not connected to each other in any manner whatsoever. As will be evident from the present description and the drawing, the gate members in the worm gate assembly 14 are constituted by a number of flat, circular discs 15. It does, however, lie within the scope of the present invention to use gate members of a different shape, provided of course, that they engage in a fluid-tight manner with the convolutions 9 in the worm 8 and can move together with these in the manner described. Thus, it could be possible to use ball-shaped or double-cone-shaped gate members, the track housings corresponding to the track housing 16 then, of course, to be shaped in such a manner that they can guide such gate members in the same manner as the track housing 16 guides the disks 15. As will be evident from Figure 1, the end of the tubular housing 7 at the greatest distance from the outlet 13 is provided with evacuation means in the form of a vacuum connection 21, being connected to a vacuum pump (not shown) or the like through a "vacuum trap" 22 and a vacuum conduit 23. When the vacuum connection 21 in this manner is situated in a location, at which the convolutions 9 and the disks 15 have not yet engaged the meat mass being supplied through the inlet 6, the air may be evacuated from the convolutions 9 before the latter - relatively speaking - reach the meat mass, the latter for this reason filling the convolutions completely without forming air pockets. Since the worm pump 2, due to the effect of the disks 15, functions as a volumetric pump, and the formation of air pockets is prevented by means of the vacuum connection 21, the volume of meat mass being conveyed per revolution will be substantially constant, so that the number of revolutions of the worm 8 can be taken as a measure of the volume of the meat mass being ejected through the outlet 13. As will also be evident from Figure 1, the disks 15 are moved into full engagement with the convolutions 9 on the worm 8 at an appreciable distance from the location, viz. at the inlet 6, where the meat mass first comes into contact with the worm 8. This arrangement prevents lumps of meat from getting jammed between one or more of the disks 15 and the convolutions 19, before the disks hav been moved into full engagement with the convolutions 9, and thus, the risk of shearing of meat lumps at this location is avoided. At the transition between the inlet 6 and the part of the tubular housing 7 situated downstream from the inlet there is, however, a certain risk that lumps of meat can get jammed between the inside of the tubular housing 7 and the ridge of the convolutions 9 on the worm 8, and in order to minimize this risk an inclined wall 24 has been placed at this transition. Due to the inherent elastic properties of the lumps of meat, the majority of such lumps possibly getting jammed between the ridge of the convolutions 9 and the inclined wall 24 will slip forwards or backwards and hence avoid being sheared between the housing 7 and the ridge of the convolutions. The health authorities of most countries require machines for processing meat to be opened, cleaned and disinfected completely with short intervals, e.g., at least once a day. With regard to the worm gate assembly 14, this requirement can easily be met by opening the cover 19 and removing the disks 15, after which it is easy to clean both the inside of the housing 16 including the lower side of the cover 19, and the disks 15 proper. In addition to the advantage with regard to a long-lasting and efficient gating engagement with the worm 8, achieved by using loose gate members, e.g. the disks 15 as shown, a substantial economic advantage is achieved, partly because such loose gate members are considerably simpler and cheaper to produce than the previously used toothed disks, partly because the loose gate members can be replaced singly, if one of them were to have been damaged. As will be evident from figure 2, the track housing 16 is shaped and oriented in such a manner, that the disks 15 do not fall out upon removal of the cover 19. This is especially an advantage when the disks are to be put back in place after the cleaning, as it would otherwise be necessary to use special leans for holding them in place until the track housing had been closed. It is not shown or described herein, how the stuffing machine shown is provided with the requisite gaskets, bearings, fittings, etc. so as to be able to function as intended. Persons skilled in this art will, however, know how to design, shape, and place such means. LIST OF PARTS 1 hopper 2 worm pump 3 cover 4 supply worm 5 motor assembly 6 inlet 7 tubular housing 8 worm 9 convolutions 10 drive assembly 11 motor 12 gear box 13 outlet 14 worm gate assembly 15 disk/gate member 16 track housing 17 internal guide 18 rectilinear track portion 19 cover 20 slot 21 vacuum connection 22 "vacuum trap" 23 vacuum conduit 24 inclined wall

Claims: Worm pump for thick media and/or media containing lumps, e.g. meat in pieces, and of the kind comprising a) a generally rotationally symmetrical tubular housing (7) with an inlet (6) and an outlet (13), comprised in a worm-pump housing (2), b) a worm rotor (8) rotatably supported in the tubular housing (7), and c) convolution-blocking means comprising c1) a track housing (16) situated laterally of the tubular housing (7) and containing at least part of an endless track limited inwardly solely by a guide member (17) surrounded by the track and outwardly partly by the inside wall of the track housing (16), partly by said worm rotor (8), so as to keep the gate members (15) in the desired track configuration, and c2) a number of loose gate members (15) supported for movement along said endless track, said gate members (15) in the part (18) of said endless track not limited by the inside wall of the track housing (16) engaging sealingly with the convolutions (9) of the worm rotor (8), whereas c3) said part (18) of the endless track with at least part of its width, as measured parallel to the plane of said endless track and transversely of the rotational axis of said worm rotor (8), extends outside of the worm-pump housing (2), and whereas c4) the track housing (16) is adapted to be opened easily in such a manner, that the gate members (15) may be removed from and inserted in the endless track transversely of the operational direction of movement of said loose gate members (15), characterized in d) that the track housing (16) comprises d1) a tray-shaped or pan-shaped lower part, to or in which said guide member (17) is secured or shaped, as well as d2) a removable lid or cover (19) adapted to close said lower part sealingly against the surroundings. Pump according to claim 1, characterized in a) that the rotational axis of the worm (8) extends in a non-vertical manner, and b) that the track housing (16) is oriented in such a manner about said rotational axis, that the side of said tray-shaped or pan-shaped lower part normally closed by said removable lid or cover (19) faces obliquely upwardly.

Inventors: SIMONSEN KNUD, SIMONSEN, KNUD
Applicants: SIMO IND AS, SIMO INDUSTRIES A/S
Application year: 1993
Main classification: F04C13
IPC codes: F04C13, F04C3