WO1998039154A1

WO1998039154A1 - Compactor apparatus

Info

Publication number: WO1998039154A1
Application number: PCT/SE1998/000415
Authority: WO
Inventors: Mattias Hedren; Staffan Tiliander
Original assignee: Spirac Engineering AB
Current assignee: Spirac Engineering AB
Priority date: 1997-03-06
Filing date: 1998-03-06
Publication date: 1998-09-11
Anticipated expiration: 1999-09-06
Also published as: SE9700815L; SE9700815D0; AU6645098A

Abstract

The present invention relates to an apparatus and to a method for compacting compactible material. The apparatus has a shaftless spiral (3) disposed in a casing (2). A drive means (4) for rotating the spiral is disposed at the infeed section (20) of the apparatus. In the opposite section of the casing, the casing has an end region (23) in the extension of the spiral, where the casing does not surround the spiral. A mechanical counter pressure device (8) is provided for closing and opening the discharge opening (24) of the end region. The material is compacted in that the spiral, on its rotation, exercises a pressure on the material which is located in the end region (23). Between the infeed section (20) and the end region (23) there is provided, close to the end region, a support member (26) which restricts the movement of the spiral in the radial direction. As a result, the spiral may absorb greater axial pressure forces than without such a mechanical device, since permanent deformation of the spiral in the radial direction is prevented. According to the method of compacting the material, the end region (23) is dimensioned so that substantially all of the force which the spiral applies against the material in the end region is transmitted to the counter pressure device (8).

Description

COMPACTOR APPARATUS

The present invention relates to an apparatus for compacting material according to the preamble to the independent claim. Such an apparatus is known from patent specification EP 0 179842 Bl.

In many contexts, and particular within industry, it is necessary to compact material which includes solid or semi sol id components of different sizes, density, elasticity, etc. In addition to compaction, there is often a need for the possibility of a controlled reduction of the liquid content of the material. Such needs exist in, for example, the processing of semi sol id or solid bodies which have already been separated from a liquid, for example screenings in industrial operations or from purification plants for waste water.

The need for controlled reduction of liquid content in material exists, for example, so as to improve the degree of efficiency in the combus- tion of rejects or in processing stages of cellulose fibres where they are washed. Screenings from purification and treatment plants for waste water are also examples of material for which an increased TS is desirable. As a rule, increased TS implies reduced costs for handling, transport and storage of the material, inter alia because the material has become lighter or obtained sufficiently high TS in order to avoid the growth of fungus. Material of the above-described type is handled daily in huge quantities and it is a reality that such handling cannot be put into effect without many problems occurring.

In both industrial operations and in refuse management, material is handled which needs to be washed. This washing becomes efficient if the total solids of the material is raised between each washing stage.

In the employment of spirals which have no mechanical shaft for com- pacting material applying the technology described in patent specification EP 0 179842 Bl, the mechanical stability of the spiral determines the maximum possible compaction. In the axial direction of the spiral, it is as a rule possible to permit relatively large dimensional changes without the spiral being damaged, while forces which cause deformation transversely of the axial direction of the spiral often entail damage to the spiral or to the casing which surrounds the spiral.

There are, therefore, strong wishes in the art to permit the shaftless spiral to absorb greater axial forces than has hitherto been possible, with the same material properties of the shaftless spiral and unchanged dimensioning. As a result, it should be possible to achieve the sought- for increased compaction of the material and, for wet material the desired increased TS. Greater axial forces however lead to an increased risk of deformation transversely of the axial direction of the spiral, for which reason the permitted axial loading on the spiral has entailed that, according to known technology, it has proved necessary to employ higher quality material or heavier dimensions in the spiral in order to achieve the desired compaction or TS in the material.

The characterizing clauses of the independent claims disclose a technology which satisfies the above-outlined desiderata and obviates the above-outlined problems.

The present invention realizes a method and an apparatus which permit a controlled compaction of the material and, when necessary, a controlled reduction of the liquid content of the material. Since the material is surrounded by the casing, the effects on the surrounding environment are reduced to a minimum.

Counter pressure and compaction of the material are created by a counter pressure device which is movable in relation to the discharge opening of the casing. The counter pressure device is formed by at least one counter pressure plate which is movably journalled, for example, in the casing or in a retainer device in connection with the discharge opening of the casing. The counter pressure plate is moved to and from a position in which the discharge opening of the apparatus is closed. The counter pressure plate is movable to any optional position between fully opened position and fully closed position. According to prior art technology, intermittent operation of apparatuses according to the preamble to the independent claim involves a serious risk that a body of compacted material remaining in the discharge portion becomes, after a time, fixed or jammed in the discharge portion. Such plug-forming bodies must be removed before the apparatus is restarted, since they entail that the spiral is often broken and/or that the casing of the discharge portion is ruptured when "new" material is fed in towards a stationary plug-forming body. Since these apparatuses are often employed intermittently and occasionally with long time intervals, the above-described plug formation is a serious drawback.

According to prior art technology, the spiral -free section of the casing is so long that the material (the plug) in the compaction section of the apparatus is arrested to a not negligible extent by the friction which occurs between the plug and the casing. This entails that the compression force exercised by the spiral against the material which is moved by the spiral into the region between the end of the spiral and the counter pressure device is not only determined by the total force the counter pressure device is set to resist, but also by the friction between the casing and the compressed plug of supplied material. As a result, uncertainty occurs on adjusting the desired maximum compression force against the material which is moved into this region when the adjustment is based on the total force which the plug applies against the counter pressure device. Uncertainty in such supervision also entails that, in practical applications where the degree of compaction is employed to control the total solids of the material which is discharged out of the apparatus, an undesirable uncertainty occurs as regards the actual total solids of the material discharged from the apparatus.

In order to avoid the above-outlined problems as regards plugs of compacted material remaining in the discharge section of the apparatus, in certain embodiments of the present invention the discharge section of the apparatus is disposed to improve the control of the compression force of the spiral against the material which is fed into the region between the spiral end and the body of compacted material located between the spiral end and the counter pressure device. This is attained in one first embodiment of the present invention in that the distance between the hatch of the counter pressure device in a closed position and the free end of the spiral is extremely short (as a rule at most approx. 1/3 of the diameter of the spiral, and in one preferred embodi- ment, at most approx. 1/4 of the diameter of the spiral).

It has surprisingly proved possible, even in such short distances, to obtain the desired controlled compression of the material between the spiral end and the counter pressure device. As a result of this short distance, the size of the friction between the body of compacted material and the casing of the discharge section is so slight that the action of the friction on the force the spiral applies against the body of compacted material is negligible. The force the material needs to apply against the hatch in order to open it will, thereby, be determi- native of the force which the spiral, on its rotation, applies against the material. The short distance between the spiral end and the hatch also obviates the risk that compacted material remaining in the discharge section forms a stationary body which prevents the apparatus from functioning.

In a second embodiment of the present invention, the sought-for effect is attained in that the discharge section is provided with a cross-section which, from the region of the free end of the spiral, increases with reducing distance to the opening of the discharge section. This design entails the desired low friction between the body of compacted material and the casing of the discharge section on movement of the body in a direction from the spiral.

As a rule, the casing is provided with drainage openings which are lo- cated at least in the region of the casing where the packing and compacting of the material take place. In such instance, an orientation is occasionally selected of the casing which implies that the discharge section of the casing is located higher than its infeed section, whereby liquid pressed out on compression is displaced in a direction oppo- site to the direction of movement of the material, at the same time as the liquid is drained out from the casing through the above-disclosed drainage openings. In yet a further embodiment of the present invention, needs are satisfied for an apparatus which not only increases the total solids (TS) of the material but which also separates solid substances out of the liquid and thereafter increases the total solids of the material formed from the separated substances.

Further expedient embodiments of the present invention are disclosed in the appended subclaims.

The present invention and its properties will be more readily understood from the following description, with reference to the accompanying drawings, in which:

Fig. 1 is an axial section through one embodiment of the apparatus where this includes only one shaftless spiral;

Figs, la-c show the sections A-A, B-B and C-C in Fig. 1;

Fig. Id shows sections through two embodiments of support members;

Fig. 2 shows the material distribution in the longitudinal direction of the apparatus;

Fig. 3 shows one embodiment of the apparatus where this includes mutually interconnected, shaftless part spirals; and

Figs. 4a-b show embodiments of the discharge section of the apparatus.

Figs. 1, la-c and 2 show one embodiment of an apparatus 1 according to the invention. The apparatus includes an elongate, tube-like casing 2 in which is placed a shaftless spiral 3 which is disposed to rotate about its geometric centre axis 34. The casing 2 is, as a rule, com- posed of a plurality of sequentially disposed casing sections. The spiral is formed as a helical blade 33 which, as a rule, is upright. The expression "helical blade" also includes helical blades composed of a plurality of part helical blades which are, for example, disposed to abut radially edge to edge with one another or disposed to overlap one another. The spiral has a free central passage 32 which extends in a longitudinal direction, at least along a part of the length of the spi - ral. The one end portion of the casing forms the infeed section 15 of the apparatus and the other end portion of the casing forms the discharge section 29 of the apparatus.

The infeed section 15 has one or more infeed openings 14 which, in the embodiment shown in the figure, connect to an upwardly-directed drum 16. In the infeed section, the casing is terminated by an end wall 12 to which is connected a drive unit 6 (hereinafter generally designated drive means 6) for rotating the spiral 3. The drive means include a motor 4, a gear unit 30 and a drive plate 10 to which the one end 36 (the infeed end 36) of the spiral is fixed. Hereafter, the other end 31 of the spiral will also be designated discharge end 31 or free end 31. The drive plate is coupled to the gear unit by means of a drive shaft which is journalled in the end wall 12. The drive plate is located within the cavity formed by the casing, while the gear unit 30 is placed on the opposite side of the end wall.

Seen in the axial direction of the casing, the combination of spiral and casing (cf. Fig. 1) is divided into an infeed zone 20, a transport zone 21, a precompaction zone 22 and a compaction zone 23.

The length of precompaction zone 22 is generally selected so that it is at least approximately equal to the diameter of the spiral and, at most, approximately equal to 1.5 times the diameter of the spiral.

The compaction zone 23 begins in the area of the discharge end 31 of the spiral and terminates at a counter pressure device 8 which will be described below and will also hereafter be designated hatch 8 without any restrictive import. The compaction zone is very short and generally is of a length which at most corresponds to between approx. 1/3 and approx. 1/4 of the diameter of the spiral. Its minimum length corresponds to approx. 1/10 or to approx. 1/5 of the diameter of the spiral. The length of the compaction zone is adapted to the properties of the material which the apparatus is intended to handle. The values disclosed in this paragraph are related to one embodiment of the discharge section of the apparatus (described below), in which the cross-section throughout the entire length of the compaction zone is substantially conforming (cf. Figs. 1, lc and Fig. 3).

The transitions between the different zones are not distinct, but the zones merge progressively in one another.

The discharge section 29 of the apparatus is provided with a discharge opening 24. That end 31 of the spiral which is directed towards the discharge opening is completely free. The mechanical counter pressure device 8 (the hatch) is disposed to close and open the discharge opening 24. At least in conjunction with the precompaction zone 22 and the compaction zone 23, the casing 2 is generally provided with passages 25 for liquid, hereinafter generally referred to as drainage openings 25.

The transport zone 21 is not necessary to ensure reliable function of the apparatus, but constitutes merely an extension of the apparatus. Such extension of the apparatus is employed, for example, when an extension constitutes the most suitable solution for satisfying established requirements as regards the placing of the infeed opening 14 and discharge opening 24 of the apparatus.

When the material which is fed to the apparatus has total solids values exceeding 5-10 percent, adequate function in the apparatus will generally be achieved even if this only comprises the infeed zone 20, the precompaction zone 22 and the compaction zone 23. In lower TS values of the infed material, for example when the infed material consists of a slurry, the apparatus includes a predewatering zone 21a with a positioning corresponding to that disclosed for the transport zone 21. In the predewatering zone 21a, the casing is provided with drainage openings 25. In the predewatering zone, a sufficient quantity of liquid is removed for the sought-for function of precompaction and subsequent compaction of the material to be obtained. In one region between the infeed section 15 and the discharge end 31 of the spiral 3, there is disposed at least one mechanical device 26, hereafter generally designated support member 26 in which the size of the cross-section within which the spiral may be displaced in a radial direction is less than in the portions of the casing disposed immediately adjacent the support member. The length of the support member in the axial direction of the spiral is at least approximately half a spiral turn and as a rule less than approximately a full spiral turn. The support member consists, at least in those portions where the spiral is intended to support against it, of a durable material with a low coefficient of friction. Normally, the support member has no drainage openings.

Generally, the support member is placed such that it is adjacent the precompaction zone 22. It will obvious that, in very compact embodiments of the apparatus, the precompaction zone 22 is caused to include also the support member 26 or parts thereof. In these embodiments, the support member or at least parts thereof are generally also provided with drainage openings 25. In all practical applications, the distance between the discharge end 31 of the spiral and the support member 26 amounts to at least approximately half of the diameter of the spiral and generally to at least approximately the whole of the diameter of the spiral. As a rule, the distance is maximized to three times the diameter of the spiral, and normally to twice the diameter of the spiral.

In Fig. 1, the support member 26 is shown as a part of the casing 2. In certain embodiments, that part of the casing which forms the support member is provided with at least three guide rules 28 (cf. Fig. la) which are disposed in space apart relationship from one another in the ci cumferential direction of the casing. The rules are generally placed in substantially corresponding distance from one another. The guide rules form abutment means against which the spiral supports on its rotation, whereby the movement of the spiral in the radial direction thereof is limited.

The cross-section through the casing in each respective zone in the illustrated embodiment is shown in Figs. la-c. It will be apparent from these figures that the casing, in the compaction zone 23, surrounds the spiral with slight play. In the precompaction zone and in the compaction zone, the casing generally is of circular cross-section. In the transport zone 21, the casing often has polygonal cross-section.

Fig. Id shows two embodiments of the support member 26 in which the support member is formed from a part spiral 26a, b which is fixed to the spiral 3. The part spiral has an outer diameter (twice the distance between the geometric centre axis of the part spiral and the edge of the part spiral facing away from the centre axis) which is greater than the outer diameter of the spiral 3. On rotation of the spiral, the part spiral 26a, b abuts against the casing or a journal disposed in the casing. This measure avoids the risk that, on rotation of the spiral 3, those parts of the spiral 3 which are located ahead of or after the support member 26a, b come into contact with the casing.

To the left in Fig. Id is shown one embodiment where the part spiral 26a fixed to the spiral 3 abuts against one of the substantially radially directed surfaces of the spiral 3, while to the right in the fig- ure the part spiral 26b abuts with its edge facing towards the geometric centre axis 34 of the spiral against the edge of the spiral 3 facing away from the geometric centre axis 34 of the spiral.

The support length of the support member 26, 26a, 26b in the axial di- rection of the casing 3 amounts at least to half of the pitch and, as a rule, at least all of the pitch of the spiral 3. In embodiments where the spiral 3 is composed of a plurality of part spirals (as will be described below), the support length in the axial direction of the casing amounts to at least to half of the pitch and generally at least to all of the pitch of one of the part spirals.

Fig. 1 also shows the hatch 8 which is disposed to retain the material or arrest its displacement in the compaction zone 23 of the casing. The figure shows one embodiment where the counter pressure device consists of a counter pressure plate 8 disposed in conjunction with the discharge opening 24 and, for example, designed as a hatch 8 which is ro- tatably journalled in connection with the discharge opening and is mov- able in the direction of the double-headed arrow D. In other embodiments, the hatch is designed to be moved in the axial direction of the spiral on closing or opening of the discharge opening 24. Hereafter, the word hatch will generally be employed without any restrictive i - port.

Fig. 1 shows one embodiment of the apparatus in which a drive means 80 for switching the hatch 8 is provided in connection with the discharge section 29 of the apparatus. The drive means is provided with a drive arm 81, for example designed as a piston. The drive arm is displaceable in the longitudinal direction of the casing 2. The end of the drive arm is movably journalled in a transmission device 82 which is rotary about a shaft 83 adjacent the discharge opening 24. The hatch 8 is fixed to the transmission device 82. With the drive arm in its protracted state (the starting position of the drive arm), the transmission device is in a position in which it holds the hatch closed. With the drive arm in its retracted state, the hatch is fully open. The size of the opening which is formed between the hatch and the casing is determined by how far the drive arm has been moved from its starting position.

In one preferred embodiment of the present invention, the adjustment of the hatch is controlled by the size of the drive output or the current which is fed to the motor 4 of the drive unit 6. To this end, a measurement device is provided for measuring the drive output or the cur- rent. Based on the measured value of output or current, a signal is transmitted to a switching device which, controlled by the signal, displaces the drive arm 81 away from or towards its starting position. The size of the output or the current which is fed to the motor 4 is determined by the quantity of material which is accumulated in the compac- tion section. An increased quantity of material requires increasingly greater output or more current to be fed to the motor in order for it to be able to rotate the spiral. An increased quantity of material also increases the pressure which the spiral, via the accumulated material, exercises on the hatch.

When the size of the measured output or current falls below a predetermined value, the drive arm is held in its protracted position, i.e. the hatch is closed. The size of the predetermined value is adjustable on each occasion of use. As a result, the operator has the possibility of adapting the size of the maximum pressure the material is to exercise against the hatch before it opens. The size of the pressure is selected in view of the properties of the relevant material and the total solids level which is desired for the material passing through the discharge opening 24 of the apparatus. When the measured output or current exceeds the predetermined value, the drive arm is displaced from its starting position, whereupon the hatch opens. When the hatch opens and the pressure of the material against the hatch thereby is reduced, the size of the measured output or current is also reduced. When the size falls below a predetermined value (also adjustable), the displacement of the hatch ceases or the drive arm moves the hatch in order wholly or partly to close the discharge opening.

It will be obvious to a person skilled in the art that, in other embodiments, the hatch 8 is disposed to co-operate with, for example, a spring which holds the hatch in the closed position when the material in the compaction section exercises a pressure against the hatch which is less than a predetermined level. The spring is set to resist a predetermined maximum force. The size of the predetermined force is adjustable on each occasion of use. The operator thereby has (analogous with that which applies also to the embodiment described in the preceding paragraph) the possibility of adapting the size of the maximum pressure on the hatch in accordance with the properties of the relevant material and after the desired total solids level of the material which is to leave the apparatus. On increased pressure in the compaction section, the pressure against the inside of the hatch increases and, when the spring is loaded with a force exceeding the predetermined maximum force, the hatch opens the discharge opening. When the hatch opens and material is discharged, the pressure of the material against the hatch is reduced, the spring displacing the hatch towards the discharge opening in order wholly or partly to close it.

In those parts of the casing where this is provided with the drainage openings 25, the casing is surrounded by receptacle chambers 5a,b for liquid which has passed through the openings. Fig. 1 shows one embodi- ment in which the apparatus includes two receptacle chambers which are connected to a conduit 50 for transport of liquid between the chambers. One of the chambers is provided with an outlet 51 through which the liquid is removed from the chambers.

Fig. 2 illustrates an application of the present invention where the material flow 40 encompasses a relatively small part of the cross-section of the casing as long as the material is located in the transport zone 21, and how the material, on its passage of the precompaction zone 22, takes up an increasing part of the cross-section in order, in the compaction zone 23 substantially to fill the entire cross-section.

Fig. 3 shows one embodiment of the apparatus where the spiral 3 is composed of two part spirals 3a, 3b of equal length, each one lacking a mechanical shaft. The part spirals are displaced in relation to one another through 180° in the direction of rotation of the spiral and are disposed so that they have a substantial coinciding geometric centre axis 34. The part spirals are, as a rule, fixed in relation to one another only in that end where they are connected to the drive plate 10 of the drive unit 6. In embodiments where the spiral is subjected to large axial pressure, the ends 31a, 31b of the part spirals are often mechanically interconnected to one another by means of a transverse stay 35. In certain embodiments, a transverse mechanical stay is disposed between the part spirals in the region of the support member 26. The transverse mechanical stays increase the mechanical stability of the spiral 3.

The apparatus according to the invention also exists in embodiments where the spiral 3 is formed from three part spirals. In this embodi - ment, the part spirals are displaced in relation to one another through 120° in the direction of rotation of the part spirals, in addition to which they have a substantially coinciding geometric centre axis. Also in this embodiment, variations occur with transverse mechanical stays.

Figs. 4a,b show embodiments of the apparatus in which the discharge section 29 has a cross-section which, at least most proximal the discharge opening 24, increases with reducing distance to the opening. Fig. 4a shows one embodiment in which the increase of the cross-section commences a distance in to the spiral -free region and Fig. 4b shows one embodiment where the increase of the cross-section begins already before the spiral-free region. As a rule, the "start point" for the in- crease of the cross-section is placed at a portion of the discharge section 29 which starts before the end 31 of the spiral at a distance at most amounting to approximately 1/4 of the diameter of the spiral and terminates after the end of the spiral at a distance at most amounting to approx. 1/4 of the diameter of the spiral. In one pre- ferred embodiment, the casing is, in that portion where the cross-section changes, in the form of a cone which broadens towards the discharge opening 24 of the apparatus.

In certain embodiments, the hatch 8 is provided with a mechanical de- vice 84 facing towards the discharge end of the spiral. The device is substantially symmetrical about a geometric axis which, when the hatch is closed, substantially coincides with the geometric centre axis 34 of the spiral. In the figures, the device is shown in embodiments in which it is in the form of a bulge 84 on the hatch or a cone 84 whose apex 86 is di ected from the hatch. When the hatch is closed, the apex 86, when the device is in the embodiment shown in the form of a cone, reaches into the precompaction zone. The device reduces the quantity of material in the centre of the compacted body.

Material which is fed to the apparatus 1 through the infeed opening 14 is displaced by the rotation of the spiral 3 in a direction towards the discharge opening 24. As is apparent from Fig. 2, an accumulation of material in the precompaction zone 22 takes place because of a reaction from the compaction zone 23 where the hatch 8 prevents the material from passing through the discharge opening 24 or arrests the material on its passage through the discharge opening. In the compaction zone, the material generally substantially fills the entire cross-section of the casing. The short length of the thus formed body of compacted material and/or the increasing cross-section of the discharge section en- tail that the friction between the body and the casing has a negligible effect on the drive output which is required for rotating the spiral as compared with the drive output which is required for pressing incoming material towards the body of compacted material in the compaction zone 23.

On displacement of the material, a reduction takes place of the liquid content of the material on passage through the precompaction zone 22 and the part area of the compaction zone 23 most proximal the precompaction zone. In many practical examples, the apparatus 1 is disposed such that the material is displaced somewhat upwards when it passes in a direction towards the discharge opening 24. Hereby, drainage of the material is facilitated, since a part of the liquid passes in a direction opposite to the direction of movement of the material and substantially in the centre of the shaftless spiral before the liquid runs out through the drainage openings 25. The liquid will thereby have the possibility of reaching the drainage openings in a region where the mate- rial has not yet had time to be compacted to any appreciable extent.

When the hatch 8 is closed, the material accumulates against the hatch and substantially in the entire area from the end 31 of the spiral and to the hatch 8 is filled with material. On displacement of the material into the compaction zone 23, an increasing quantity of material is accumulated in the zone, whereby the pressure of the rotating spiral end against the accumulated material progressively increases. In the compaction zone, a body is thereby formed of compressed material. Because of the slight extent of the zone in the axial direction and/or its gen- erally outwardly conical design, the friction, as was disclosed above, which occurs between the body and the casing is negligible. The pressure which the spiral end exercises against the body is propagated substantially in the axial direction and absorbed by the hatch 8. Liquid which has been absorbed by or accompanies the material is pressed out of the material on the material becoming denser in the precompaction zone and when the spiral, at the beginning of the compaction zone 23, presses the material against the body existing in the compaction zone. The body which is tightly compressed in the axial direction permits liquid to pass only in the region immediately after the spiral end. The liquid leaves the casing through its drainage openings 25. The hatch 8 is adjusted to be opened at a predetermined pressure against the hatch. The size of the pressure is set in view of the material properties of the material fed into the apparatus and the desired total solids of the material which leaves the apparatus. When very wet material is fed into the apparatus, one embodiment is generally employed which includes a predewatering zone in which the requisite quantity of liquid is drained out of the material in order for the material, on its continued displacement, to be compacted in accordance with the operational cycle which has already been described.

When the apparatus is employed to achieve high total solids, as a rule total solids exceeding 30% in the material which leaves the apparatus, very high pressure is required in the compaction zone. The forces the spiral applies against the material in the compaction zone are so great that forces occur in the spiral which, in the absence of the support member 26, would lead to the rotating spiral being deformed in the radial direction in its free end portion 31, or in a region between the end of the spiral and the anchorage of the spiral against the drive unit 6. The spiral would then rotate under powerful pressure against the casing, which would entail severe wearing of both casing and spiral. Under certain circumstances, the disadvantage could also occur that the deformation of the spiral in the radial direction became permanent. A deformed spiral must be replaced by a straight spiral. The support member 26 makes it possible to allow the spiral to exercise a greater pressure against the material in the compaction zone than has previously been possible, at the same time as the risk of the above- described deformation and problems linked therewith is reduced.

The mechanical support device thus makes it possible to allow the spi- ral to exercise a greater pressure against the material in the compaction zone than that pressure which could be permitted in an apparatus lacking mechanical support members, at the same time as the tolerances in other parts of the apparatus only need to be adapted to those requirements which must be satisfied to achieve the desired interplay be- tween material and apparatus in each handling stage of the material. By using the support member 26, it has become possible to achieve very high total solids in the material leaving the apparatus. Thus, for example, in wet paper pulp (TS less than 5-10%) which was fed into the apparatus, the total solids level rose to more than 40%.

In certain applications of the present invention, the liquid which leaves the apparatus via the outlet 51 is the product which is taken care of and the material with reduced liquid content constitutes the reject, while in other applications of the present invention it is the liquid which forms the reject. In certain embodiments, the receptacle chambers 5a, 5b are provided with separate outlets in order to make it possible to adapt the subsequent handling of the liquids in response to the different properties they have.

In the embodiments with two part spirals which are mutually offset through 180° or of three part spirals which are mutually offset through 120°, the part spirals exercise a distributed pressure against the material which, in the compaction zone, is pressed against the body of compacted material. As a result, this reduces the tendency of the body to "capsize" since the asymmetric pressure which is applied on using only one spiral is avoided. In those embodiments where the intention is to employ extremely high pressures against the body, the ends of the part spirals are generally connected to one another by means of the stay 35. This achieves a balancing of the forces which are absorbed by the part spirals, depending upon the pressure which these apply against the material which is pressed against the body. The higher pressure entails increased compaction and thereby also increased dewatering and reduction of the liquid content.

The above described counter pressure device has, in certain embodiments, two or more counter pressure plates 8. Since the function of the apparatus is based on progressive increase of the material quantity in the compaction section of the apparatus and the effect the accumulation has on the drive output which is required to rotate the spiral, the present invention entails a large degree of freedom as regards the design of the discharge section. Embodiments in which the discharge section is provided with a cross-section which is greatest at the edge of the discharge opening are particularly well suited to be used in installations where the need for compacting the material occurs intermittently and occasionally with long time intervals.

In embodiments including the mechanical device 84 disposed on the hatch, the quantity of material is reduced in the centre of the body of compacted material formed in the compaction zone. This contributes in increasing the TS in the material in the body, since the residual liquid in the centre of the body of compacted material may find it diffi- cult to reach the drainage openings 25 through surrounding compacted material. With the mechanical device 84, the guiding of the material which the spiral end 31 feeds in towards the body of compacted material is also improved.

A wish throughout which the present invention satisfies is that a body of compressed material located in the discharge section of the apparatus must be able simply to be removed from the discharge section when the hatch 8 is fully open. The above described, extremely short distance between the discharge end 31 of the spiral and the hatch 8, which is employed particularly in a cylindrical cross-section of the discharge section satisfies this wish. In longer distances between the spiral end and the hatch, and thereby longer bodies of compacted material, use is primarily made of the conical design of the discharge section whereby the risk is eliminated that any possible remaining body of compacted material in the discharge section after some time becomes stuck. As a result of the present invention, it is possible to adapt the length of the body in the axial direction in accordance with the properties of the material which is fed into the apparatus in order therein to be compacted and/or to obtain reduced liquid content. The conical design also entails the advantage that it is possible to permit extremely high pressure in the compaction section without there being formed material bodies which fasten in the discharge section.

The above detailed description has referred to but a limited number of embodiments of the present invention, but a person skilled in the art will readily perceive that the present invention encompasses a large number of modifications and embodiments without departing from the scope of the appended claims.

Claims

1. An apparatus for compacting compactible material containing liquid, in which the apparatus includes an infeed section (15) and a dis- charge section (29) with a discharge opening (24), in which a rotary, shaftless spiral (3) is disposed in a casing (2) which, at least along a part of its length, surrounds the spiral, the spiral having a terminal end (31) and a free central passage (32) which extends in the longitudinal direction at least along a part of the length of the spiral, where a drive unit (6) for rotating the spiral is provided in connection with the infeed section for causing the spiral to displace the material towards the discharge opening, where one or more infeed openings (14) for the material are provided in said infeed section, where an end portion (22,23) of the casing (2) includes a portion having no spiral and located between the end (31) of the spiral and the discharge opening (24), where a mechanical counter pressure device (8) is disposed to be moved between a position where the discharge opening is closed and positions in which the discharge opening is wholly or partly open, and where the casing is provided with a plurality of drainage openings (25) which pass through the wall of the casing in that region where the compaction of the material takes place, c h a r a c t e r i z e d in that at least in a region between the infeed section (15) and the end (31) of the spiral (3), there is disposed a mecha- nical support member (26) which, for stabilizing the spiral, restricts the displacement of the spiral transversely of the axial direction of the spiral so as only to take place in a cross-section which prevents the spiral from reaching contact with the casing in portions of the casing which, in the axial direction of the spiral, are located adjacent the support member.

2. The apparatus as claimed in Claim 1, c h a r a c t e r i z e d in that the support member (26) is formed from a casing portion (27) with an inner cross-sectional surface which is less than the inner cross-sectional surface of the parts of the casing (2) disposed immediately adjacent the support member.

3. The apparatus as claimed in Claim 1, c h a r a c t e r i z e d in that the mechanical device (26) includes at least three guide rules (28) disposed in the axial direction of the casing a distance from each other, and limiting the displacement of the spiral (3) trans- versely of the axial direction of the spiral.

4. The apparatus as claimed in Claim 1, c h a r a c t e r i z e d in that the mechanical support member (26) is formed from a part spiral (26a,b) which is fixed to the spiral (3) and which has an outer diameter exceeding the outer diameter of the spiral.

5. The apparatus as claimed in any of the preceding Claims, c h a r a c t e i z e d in that two spirals are disposed in the casing and that the spirals are displaced through 180° in relation to one another in the direction of rotation of the spirals.

6. The apparatus as claimed in any of Claims 1-4, c h a r a c t e r i z e d in that three spirals are provided in the casing and that the spirals are offset through 120° in relation to one another in the direction of rotation of the spirals.

7. The apparatus as claimed in any of Claims 5 or 6, c h a r a c t e r i z e d in that the spirals are fixed in relation to one another only in that end where they are connected to the drive unit (6).

8. The apparatus as claimed in any of Claims 5 or 6, c h a r a c t e r i z e d in that the ends (31a,b) of the spirals are mechanically interconnected with one another by means of one or more stays (35) .

9. The apparatus as claimed in any of Claims 2-8, c h a r a c t e r i z e d in that the support length of the support member (26) in the axial direction of the casing (3) at least amounts to half of the pitch of the thread blade (33) and as a rule the whole of the pitch of one and the same spiral.

10. The apparatus as claimed in any of the preceding Claims, c h a r a c t e r i z e d in that the casing (2) in the discharge section (29) has a cross-section which, between the free end (31) of the spiral and the discharge opening (24), increases with reducing distance to the discharge opening at least in a region adjacent the discharge opening.

11. The apparatus as claimed in Claim 10, c h a ra c t e r i z e d in that the increase of the cross-section of the discharge opening (24) begins in a portion of the discharge section (29) which commences before the end (31) of the spiral a distance from the end corresponding to approx. 1/4 of the axial length of one spiral turn and terminates after the end (31) a distance therefrom corresponding to approx. 1/4 of the axial length of one spiral turn.

12. The apparatus as claimed in any of the preceding Claims, c h a r a c t e r i z e d in that the support member (26) is disposed in a region close to the end (31) of the spiral (3) and that said region is located a distance from the end of the spiral which ex- ceeds one half of a spiral turn.

13. A method of compacting compactible material which, in a tubular casing (2) is displaced by a shaftless spiral (3) rotating in the casing from infeed section (15) to a discharge opening (24) dis- posed in the axial direction of the casing, where the material for its compaction is displaced into a spiral -free region (23) located between the end (31) of the spiral and a counter pressure device (8) which is disposed to wholly or partly close the discharge opening (24) where, at a predetermined pressure force applied by the material against the counter pressure device, said counter pressure device opens the discharge opening (24), c h a r a c t e r !^* z e d in that substantially all of the force which the spiral (3) applies on the material which is located between the spiral end (31) and a body of compacted material formed between the spiral end and the counter pressure device (8) is transmitted to the counter pressure device (8).

14. The method as claimed in Claim 13, c h a r a c t e r i z e d in that the size of the force which the spiral (3) applies on the material between the spiral end (31) and the counter pressure device (8) is regulated by sensing the size of the current or output which is fed to a drive unit (6) for rotation of the spiral.

15. The method as claimed in Claim 13 or 14, c h a r a c t e r i z e d in that, for mechanical stabilization of the end portion (31) of the spiral (3), a mechanical support member (26) in a region proxi- mal the end (31) of the spiral, supports the spiral (3) against its edge facing away from the geometric centre axis (34) or that a part spiral (26a,b) fixed to the spiral and having greater outer diameter than the diameter of the spiral (3) abuts against the casing (2) with the edge of the part spiral facing away from the geometric centre axis (34) .