Title:
Adjustable pressure worm press
United States Patent 3877365
Abstract:
A worm press suitable for squeezing liquid out of wood pulp has an axially movable worm operating in a strainer cylinder with a flaring outlet end for the solids. The worm shaft carries a freely rotatable frusto-conical end piece. The worm shaft is actually displaced by hydraulic pressure to vary the cross-sectional area of the outlet. A small reciprocating axial movement helps to prevent jamming of the press.


Inventors:
BERGGREN LENNART
Application Number:
05/377210
Publication Date:
04/15/1975
Filing Date:
07/09/1973
Assignee:
AB Krima Maskinfabrik (Nassjo, SW)
Primary Class:
Other Classes:
100/148, 415/72
International Classes:
B30B9/12; B30B9/18; D21C9/18; (IPC1-7): B30B9/12; B30B15/00
Field of Search:
100/117,126,145,146,147,148,149,150,37
View Patent Images:
US Patent References:
3394649Liquid extracting device1968-07-30Kemper et al.
3126818N/A1964-03-31Koelsch
2903960Press for dewatering slurries1959-09-15Zies
2817287Expressing apparatus1957-12-24Onarheim et al.
2697978Apparatus for extracting liquid from liquid-bearing material1954-12-28MacIlwaine
1152857N/A1915-09-07Stehlin
Primary Examiner:
Feldman, Peter
Attorney, Agent or Firm:
Flynn & Frishauf
Claims:
What we claim is

1. A worm press for the removal of liquid from a mixture of a solid and liquid, the press comprising a cylindrical strainer surrounding a rotatable worm, means for supplying the mixture to be pressed at the one end of the strainer and means for discharging the pressed solid at the other end of the strainer through an annular outlet opening surrounded by a wall which diverges in the direction of movement of the solid along the worm, wherein the worm has a core having portions of successively increasing diameter along a major part of its length so that the space between the core and the strainer decreases in the direction of movement of the solid along the worm, the worm is axially movable relative to the diverging outlet wall by hydraulic means during operation of the press and the inner periphery of the outlet opening is defined by a frusto-conical body which is freely rotatable relative to, but is axially movable with, the worm, said frusto-conical body having a smooth peripheral surface diverging from its axis at an angle not exceeding the angle of divergence of said outlet wall, which surface of said body is substantially flush with said worm core so as to substantially form an extension of said worm core.

2. A press as claimed in claim 1, in which the hydraulic means is arranged to cause the worm, in operation of the press, to carry out a continuous reciprocating movement.

Description:
The presently used types of presses for pressing liquid out of slurries, sediments or fibrous suspensions, e.g., wood pulps, are mainly mills, disc presses and worm presses. The first two types are very expensive and are accordingly only used in large plants because they are completely uneconomical in smaller installations. For smaller installations industry has therefore been limited to worm presses, but these have a number of drawbacks and limitations related both to their structure and their operation. Most of these disadvantages stem from the fact that the solid content of the material supplied to the press varies within comparatively wide limits and this results in corresponding variations in the finished product. It has not previously been practicable to control these conditions during the operation of the press. By providing in interchangeable components at the outlet end of the press to vary the restriction necessary to build up a back pressure in the material being pressed it has been feasible in the intervals while the press is not working to alter the operating characteristics of the press. However this does not make it possible to match the characteristics to variations in the constitution of the material supplied to the press, particularly the proportion of solid matter and the structure such as fibre dimensions, particle size and the like, which occur during a single continuous operation of the press. When the cross-sectional area of the press outlet is too large, the finished product has too high a liquid content and for this reason cannot be handled at all or only with great difficulty. On the other hand, if the cross-sectional area of is the cross-sectional area of a considerable risk of blocking of the press or of damaging the material. Such damage happens because the liquid content of the material becomes so low that frictional heating occurs in it. This happens especially with cellulose fibres.

The main object of the present invention is to provide a worm press in which the limitations and disadvantages described above are largely or completely eliminated so that the press can operate safely and can during operation be adjusted to match its characteristics to variations in the properties of the material supplied to it. The result of this is that the solid content of the finished pressed product can be maintained at a high and substantially constant value.

A further object of the invention is to provide a press which has the above advantages and which also has a high working capacity and a relatively low manufacturing price.

The invention is concerned with a worm press for the removal of liquid from a mixture of a solid and liquid, the press comprising a cylindrical strainer surrounding a rotatable worm, means for supplying the mixture to be pressed at the one end of the strainer and means for discharging the pressed solid at the other end of the strainer through an annular outlet opening surrounded by a wall which diverges in the direction of movement of the solid along the worm and, according to the invention, in such a press the worm has a core having portions of successively increasing diameter along a major part of its length so that the space between the core and the strainer decreases in the direction of movement of the solid along the worm, the worm is axially movable relative to the diverging outlet wall by hydraulic means during operation of the press and the inner periphery of the outlet opening is defined by a frusto-conical body which is freely rotatable relative to, but is axially movable with, the worm.

The surface of the frusto-conical body should form a smooth continuation of the surface of the worm core.

An example of a press in accordance with the invention will now be described in greater detail with reference to the accompanying drawing which is a longitudinal section through the press.

Reference numeral 1 refers to a frame of the press which supports two bearing housings 2 and 3 disposed at the two ends of a shaft 4 carrying a worm 7 which is horizontal. The worm shaft 4 may be driven by any suitable means such as a chain or a V-belt transmission which is not shown on the drawing. The bearing housing 2 carries an end shield 5 through which the shaft 4 passes into a press chamber, the outer wall of which is formed by a cylindrical strainer 6 and the inner wall of which is formed by a core 8 of the worm 7. As shown in the drawing, the core increases successively in diameter along the major portion, of approximately two thirds, of its length. Numeral 9 designates a blade of the worm 7 and 10 refers to perforations in the bottom portion of the strainer 6 through which liquid removed during a pressing operation is discharged, first to a trough-like space 11 and then to a liquid outlet 12. The material to be pressed is supplied to the press through an inlet 13, and its solid content is generally of the order of a few percent. The pressed material is discharged through an annular outlet opening between a frusto-conical body 15 mounted on the shaft 4 and a frusto-conical extension 16 of the strainer 6. The extension 16 has further perforations 19. After leaving the press the pressed material passes through an outlet 17 and is collected for the formation of briquettes or the like.

The frusto-conical body 15 is freely rotatably mounted on the shaft 4 by means of a pair of ball bearings 18. The result of this is that, in operation of the press, the body 15 remains substantially stationary while the shaft 4 rotates.

Inside the bearing housing 3 there is a double-spherical roller bearing 20 supporting the adjacent end of the shaft 4. The housing 2 surrounds an inner bearing housing 21 which contains two double roller bearings 22 and 23 carrying the shaft 4, and the housing 21 is itself axially displaceable inside the housing 2. The housing 21 has a radially outwardly projecting flange 24 in the sealing contact with the internal surface of the wall of the housing 2. The seal may be obtained by means of an O-ring. A sleeve 25 is disposed on one side of the flange 24 and on the other side there is a radially inwardly projecting flange 26. The sleeve 25 and the flange 26 are rigidly secured to the housing 2 and have seals between them and the housing 21. In the wall of the housing 2 there are apertures 27 and 28 communicating with the spaces at the two sides of the flange 24 for the supply and discharge of hydraulic fluid as indicated by two double arrows. The assembly just described forms a double-acting hydraulic ram the piston of which is formed by the flange 24. By means of this ram, the shaft 4, and hence the worm 7 and the body 15 may be displaced in its axial direction during operation of the press in order to vary the area of the opening 14 and alter the back pressure built up in the press chamber. In combination with the increasing cross-section of the worm core 8 this feature gives the press excellent operational characteristics. Practical tests have shown that the pressing operation in terms of solid content of the pressed material is much higher than in existing worm presses and also that the risk of friction heating of the material in the outlet zone is overcome. Solid contents of the order of 60% have been reached in wood pulp materials. In some applications it is satisfactory to cause the axial displacement of the shaft 4 with the worm 7 and the body 15 to be a continuous reciprocating movement. The amplitude of this movement may conveniently be about 5 mm.