GB2092473A - Apparatus for the recovery of protein from green vegetable matter - Google Patents

Abstract

The invention concerns apparatus for the opening-up of raw green vegetable matter. The apparatus comprises grinding chamber provided with a working surface, a rotor in the grinding chamber carrying oscillatably suspended breaking hammers 8 and a housing bounding the grinding chamber and provided with inlet and outlet ducts. The working surface is a liner 11 having mutually parallel guiding channels 12 Figure 4 diverging at an acute angle from either side of a vertical bisection line towards the right and left edge of the liner. The gap between the grinding surface of the liner and the envelope of the tips of the breaking hammers decreases from the inlet towards the outlet ducts. <IMAGE>

Description

SPECIFICATION Apparatus for the recovery of protein from green vegetable matter The invention concerns a process and apparatus for the recovery of protein from green vegetable matter; more particularly, the invention concerns a process and apparatus for the mechanical opening up (initial mechanical attack facilitating further processing) of green vegetable matter for maximally freeing the protein-containing components in the cells and tissues of plants.

In known processes aiming to recover protein from green vegetable matter the harvested raw green plant material e.g. lucerne, is either pressed immediately after harvesting or is ground and then pressed in two mutually independent machine units with the general aim of maximally exposing the cells to win the greatest possible yield of juice (liquor) and protein. Many experiments have been conducted for the opening up of green vegetable matter utilising hammer mills or hammer disintegrators. Such devices are normally used for the comminution into fine particle sizes of dry solid materials such as ores, coal, rock as well as hard, dry, granular agricultural products such as dried maize (corn).The known hammer mills operate with so-called hammers or striking rods which reolve about an axis at a high rate of revolution such as 600-2,800 r.p.m. the hammers being in general pivotally mounted on discs rotating with the driven shafts. Under the effect of the centrifugal force the hammers take up a generally radial position on rotation by pivotally moving about their pivots while causing the material to be comminuted to be flung with great force against a lining of suitable hardness, the so-called grinding surface disposed in a housing accommodating the rotary constructional parts. Alternatively, the collision or impact may be against rods or grids or drum baskets or screens arranged in the housing. In this way, the material to be comminuted is subjected to a variety of mechanical effects such as striking or impacts, pressure, tensile and cutting-shearing loads.As a consequence of the mechanical effects, the material to be comminuted receives a very large number of intensive impacts as a result of which it divides or disintegrates into very small parts. The comminuted material passes through a screen or openings in the drum, is collected in a collection space and removed from the grinding space via a discharge opening. Generally, the comminution ratio is 1:10-12.

Practice has proved that granular products may be comminuted in hammer mills only when in an air-dry condition or when dried to a moisture content of not more than 6-8%. Should the material to be comminuted have a higher moisture content, it smears and adheres to the hammers ortho the drum surfaces and clogs up the openings in the screen.

It is also known that attempts have been made to widen the usefulness of hammer mills for comminution of fibrous fodder plants such as hay and other fibrous materials. To this end toothed, ribbed, slatted and fine mesh grid lining elements or drums have been employed as abutment surfaces in the grinding chamber or space. Moreover, to prevent the smearing and clogging of the material to be comminuted pointed or sharpened striking arms have been interposed amongst the oscillating hammers, or, in certain other constructional variants, rotary or oscillating sweeping heads have been utilised. With certain known constructional solutions the previously comminuted, cut material is passed from the grinding chamber via a connecting duct to a separate drum having a screening chamber in which the comminuted material is handled by rotary blades for classification.

In general, the material to be comminuted is introduced tangentially into the hammer mills whereafter it is processed and discharged at the other end of the apparatus through a screen or sieve or rotary drum basket.

In the case of processing or opening up green vegetable matter for the extraction of protein it is dificult to regulate the degree of pulping, in other words the consistency of the resulting paste or pulp, with the known devices because the degree of comminution either cannot be regulated at all or can only be regulated with diffiulty. Although it is possible to influence the degree of pulping or paste consistency by a suitable selection of the shape of the hammer mills and/or by the insertion of teeth between the hammer mills, these constructional solutions are not suitable for all fibrous plant materials. Thus for each individual plant type, the degree of cominution has to be determined by separate experiments.

The greatest disadvantage of the use of hammer mills is that during comminution, the green vegetable matter is heated up as a consequence of which the protein contained therein is precipitated, resulting in a decrease of the protein recoverable from the pressing juice.

Experiments have been conducted with so-called disintegrators for breaking down fibrous materials. One well-known disintegrator is the Rietz disintegrator which unites or combines in itself the operation of mills that work by wearing, cutting, beating and screening. In a disintegrator of this type, the hammer mills rotate about a vertical axis within a fully cylindrical screen spaced by a small clearance from the tips of the hammers. In operation the hammers fully sweep the screen area to increase the comminution efficiency while at the same this sweeping movement inhibits clogging of the screen openings. The hammers may be fixedly or pivotally mounted on the vertical driven shaft. In such disintegrators the fed in material to be comminuted is passed into the grinding chamber either in a direction parallel with the axis of rotation or tangentially as in hammer mills.The comminuted product is generally removed tangentially through the screen fully surrounding the rotary parts.

An advantage of the Rietz disintegrator is that as a result of the constructional form of the hammers the screen may be kept clean or free at all times, whereby to render the grinding more uniform. However, when comminuting green vegetable matter of high moisture content, the hammers of the Rietz disintegrator are incapable of maintaining this screen surface clean, and the smeared wet disintegrated material clogs up the perforations in the screen. In such a case, the unground material passes out into the discharge section without being opened up. A further disadvantage is that the green vegetable matter passing through the perforated basket or screen of the disintegrator is frequently heated up sufficiently to cause the protein content thereof to be precipitated out.This phenomenon arises particularly when the unground material is recylced into the grinding chamber. Thus in such a case, in addition to the protein loss, the energy consumption is also significantly increased. Finally, it is a disadvantage in these disintegrators that there is no possibility of regulating the consistency of the pulp or paste of green matter.

For opening up green plant fibres, the so-called Owens disintegrator has also been used. This disintegrator has fixed hammer system rotating about a vertical axis and has four breaking ribs fixed to the housing. The housing does not have other components serving for opening up or comminution. The rapidly rotating fixed hammer system is suitable for removing the green matter in a tangential direction as a consequence of which the energy required for transporting air is increased. In certain cases, the Owens type disintegrator cannot be used at all because of its excessively high energy requirement which renders its operation uneconomic.

The fibre content of plants and the protein content in its fibres and tissues varies with the type of plant and moreover even with the same type of plant varies with the stage of ripening or maturity of the plant. Because of the variation in the fibre and protein content, it is a requirement of any mechanical opening-up process and apparatus that the degree of opening up and pulping should be regulatable in order that, for a given dry matter content of the plant, i.e. for a given fibre and protein content, the protein yield should be maximisable. It is known that the dry matter content, protein content and fibre content of the different plants varies in accordance with the vegetative stage of the plant, such as the green bud stage; the beginning of the flowering; full flowering and the post-flowering stage.For lucerne, the dry matter content varies between 20-24%, the protein content between 26.7 and 21.2% and the fibre content between 28.5 and 30.7% while in the case of Sudan grass, the dry matter content varies between 15.1 and 26.7%, the protein content between 19.2 and 13.1%, the fibre content between 26.8 and 31%. This means that the protein content is at its highest at the initial stage of the vegetative cycle and then significantly decreases after flowering while the variation of the fibre content is in the opposite direction, that is to say, it increases with the advance of the degree of maturity or ripening.

The protein yield from green vegetable matter also depends on the manner of further processing of the comminuted and pulped material. The pulped green vegetable matter is generally pressed by band presses at low pressures of 1 to 2 atmospheres to obtain a thin press cake. Frequently the band presses are provided with a ribbed surface. According to experience, because of the formation of a very thick filter layer the chloroplasts remain in the press cake which causes press losses and reduces the possible protein yield. In processing green vegetable matter it has also been attempted to combine the comminution and pressing, e.g. in the processing of sugar cane cylindrical grinding devices have been used, that is to say, cylindrical presses.By such processing, however, the major part of the protein remains in the fibrous matter and cannot be recovered from the pressing juice.

One principal aim of the invention is to develop a process for the production of a protein concentrate (usually referred to as LPC, leaf protein concentrate) from comminuted green matter and from the cell juices and tissues therein which concentrate is to be suitable for feeding monogastric animals as well as human beings. It is a further important aim that the available raw plant material and the main mass of the recoverable protein therein should be transformable into a liquid phase whereby to give rise to a significant energy saving in the drying of the firous product. A further important aim is the maximal recovery of the protein content from the opened-up cell liquid and the utilisation of the fibrous material separated from the protein in the presssing juice as fodder for ruminant animals.

Another principal aim of the invention is to provide apparatus for opening up green vegetable matter which eliminates or at least reduces the disadvantages of known apparatus of similar aim and which improves the efficiency of production of fibre4ree protein concentrate or protein concentrate of low fibre content from plant cell juices and tissus, such concentrate being suitable for feeding not only ruminant animals but also monogastric animals and human beings.

We have found that the achievement of these aims is decisively dependent on the manner of comminution and further processing of the green vegetable matter. This is because two fundamental conditions must be ensured during comminution. One of them is that in carrying out the comminution process, the temperature should be as low as possible while the efficiency of opening-up of the cells is maximised. The other condition is the production of opened-up material of suitable structural properties which makes it possible to increase the yield of the pressed-out juice and which makes it possible further to utilise the press cake containing the main mass of the fibrous material.

The comminution at gentle heat and the maximum exposure of the cells appear to be contradictory requirements which have nevertheless been reconciled in the process according to the invention.

The process according to the invention for opening-up green vegetable raw matter by mechanical means and using mechanical comminution and pressing of the comminuted product is characterised in that it utilises green vegetable matter of at most 35% dry matter content, expediently in a freshly harvested state, and cut to a stalk of fibre length of 40 to 50 mm and this is then passed in a single pass through a mechanical opening-up device, wherein its cells and tissues are sequentially subjected to tearing and pulping, shattering, wearing and pounding, rubbing and cutting and gentle pressing, while the vegetable matter is allowed to heat up to 350C whereby maximally freeing the cell juices, then the fibre fraction of the material is comminuted to a minimum length of 3 to 8 mm, but preferably calculated on the total weight of the fibre fraction, 35 to 40% thereof is cut to a length of 15 to 30 mm, and the thus pulped vegetable material is pressed at ambient temperatures, expediently on a planetary laminar press.

According to another aspect of the invention, the aparatus for opening up green vegetable matter by mechanical means may be characterised in that it has a grinding chamber or space provided with a grinding surface wherein is disposed a rotor carrying oscillatably suspended beating hammers, the grinding space being bounded by a casing provided with an inlet opening or hopper and a discharge opening or hopper; the essence of the invention residing in that on the grinding surface of the grinding liner of the grinding chamber guiding channels are formed these grinding channels being mutually parallel and including an acute angle with the vertical bisection line of the grinding surface and being directed towards the right-hand and left-hand edges of the grinding surface; furthermore, in that the gap between the grinding surface of the grinding liner provided with guide channels and the end surface of the breaking lines constituted by the breaking hammers freely ocillatably journalled on the rotor and arranged at a spacing from each other is formed so as to converge from the inlet to the outlet relative to the direction of rotation of the rotor.

Reverting to the process, a surface-active material is preferably added the green vegetable matter to be opened up before the start of the process, expediently in the form of an aqueous solution, which surface-active material (surfactant) hinders or prevents the separation of the protein fraction which would coagulate under the effect of heat. Calculated on the dry matter content of the green vegetable matter, the surface-active material employed is in the amount of 240-600 ppm (parts per million) and falls in the range of 8 to 18 HLB (for the determination of the HLB value see W.C.Griffin, J.Soc.Cosmetics Chemistry, 1, 31 1, 1949). in accordance with its characteristics, the surface-active material is foaming-inhibiting, thus one may use polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monostearate or propylene glycol monolaurate.

The apparatus according to the invention is different from all known apparatus serving the same aim in that the previously already-coarsely comminuted green fibrous materials are disintegrated and guided on the guiding surface of the liners by means of the guiding channels and under the effect of the displacement of the breaking hammers, and thereafter the fibrous material is sheared to the desired length at the edges of the flanks of the guiding channels, whereafter this vegetable matter is subjected to a gentle pressure in these guide channels and the completely opened-up green vegetable matter, or in other words the pulp or paste that contains protein is given off at the discharge outlet.

According to a further preferred characteristic of the invention the channels formed on the guiding surface of the grinding liners on the guiding surface of the grinding liners are of set relative to each other as regards the points of intersection with the vertical bisection line of the grinding surface. In other words, the channels are discontinuous at the bisection line. This configuration of the channels makes it possible for a gentle pressure effect to arise in the channels because their offset configuration inhibits the flow of the comminuted material from one channel to another.

According to the invention it is advantageous to arrange for the angle between the vertical bisection line and the guide channels to be about 80 . In this case the guiding of the material is optimal. The fibre length of the comminuted green vegetable matter after comminution is provided by the preferred characteristic of the invention whereby the guiding surface of the grinding liner and the breaking line formed form the oscillatably journalled breaking hammers has a gap therebetween which, regarding the direction of rotation of the rotor converges from the inlet along a 90" segment and thereafter remains constant to the outlet, the constant gap being dimensioned in dependence on the desired fibre length.

According to a further characteristic of the preferred embodiment of the invention, in the direction of rotation of the rotor after the inlet opening and before the outlet opening the gap ratio of grinding is advantageously adjusted to 10:1. This constructional solution influences, according to experience, the degree of pulping or pasting and that in turns means the quality of the opening-up.

For the best and most rapid opening-up of the green vegetable matter, in a preferred embodiment of the invention the length of the breaking lines formed from oscillatablyjournalled breaking hammers is greater than or at least equal to the dimeter of the rotor journalling the oscillating hammers.

Furthermore, the utilisability of the breaking hammers may be increased in accordance with the preferred constructional embodiment of the invention wherein the breaking hammers are formed with mutually oppositely arranged journalling openings. In such a constructional embodiment in the event of wear the breaking hammers can be turned over and further utilised.

It is a great advantage of the apparatus according to the invention that it utilises the breaking and striking and disintegrating effects of hammer mills whilst at the same time it breaks up and shears the fibres. The guiding channels not only guide and spread the material to be opened-up but at the same time by virtue of the edges of their side walls or flanks, they also exert a shearing effect. Still further, the guide channel also utilises the pressure energy of the rapidly rotating hammers in that the pulped or pasted material is subjected to a mild pressure effect in the guiding channels and in the course of this the protein-containing liquid is pressed out from the cell material. Finally, because of the increased contact surfaces of the guiding channels, the opening up process is accompanied by increased natural cooling of the material and thus the protein content thereof is not precipitated out.

As mentioned above, in an expedient embodiment in place of the above apparatus a planetary press is employed. As a planetary press, a screw press and especially a twin-screw press is most advantageously employed. It is a condition of the efficient operation of a twin-screw press that the comminuted opened vegetable pulp should have a suitable structure. According to experience, the efficient operation of the press with simultaneous maximal juice yield can only be ensured if the fibres are of suitable length to promote the pressing effect in the screw press.

The process according to the invention is extremely suitable for the uniform and fine distribution of the utilised additive material. The foam-inhibiting property of the surface-active materials is extremely advantageous because in the separation of the precipitate after coagulation of the protein, it inhibits or prevents the formation of air-containing flocculent precipitate the separation of which would be technologically extremely difficult to achieve. The foam-inhibiting property is the more efficient the more uniformly the surface-active material is distributed in the green vegetable matter without the use of extra energy consumption for stirring. The uniform distribution also makes it possible to reduce the amount of surface-active material employed.In addition to their foam-inhibiting properties, according to our experience, the surface-active materials also delay the separation of the heat-coagulatable protein and principally they inhibit the separation of the cytoplasm protein fraction, even in cases where in the course of the process a temperature rise takes place due to unforeseen circumstances.

The advantages of the process according to the invention may be briefly summarised below as follows: 1) Its use enables the uniform processing of the most difficult types of plants independently of the fibre and protein content whilst ensuring maximal protein yield.

2) The extent"degree of pulping of the green vegetable matter can be regulated in dependence upon the kind of press that is employed.

3) Because of its fibre or stalk length the fibrous fraction prepared from the pulped product is extremely suitable for use as fodder.

4) The drying of the fibrous fraction obtained in the course of opening up and pressing the green vegetable matter requires considerably lower heat energy investment than in the known processes.

5) The investment costs for carrying out the process are low and its operation costs are not significant, since the homogeneous condition of the processed material can be adjusted or regulated.

The higher efficiency of the process according to the invention compared with the Rietz and Owens disintegrators have been verified by experiment. In the experiments, starting from the given raw vegetable matter, the pressing juice yield or rather its coagulatable protein content has been chosen as the significant parameter. Freshly ground lucerne was comminuted according to the experiment in a Rietz and Owens disintegrator as well as in the apparatus acording to the invention and then the pulped vegetable matter was pressed on a Stord 30-24 type twin-screw press (Manufactured by Stord Barts, Bergen, Norway) then the obtained amounts of press juice and its dry matter content were measured.The results of the experiments are summarised in the Table below: Quantity of Dry matter Proteinaceous dry Pressing juice content of matter coagulatable kg/t pressing juice at 82"C in gil g/l Rietz 501 104 31 Owens 416 112 27 According to the invention 590 128 58 From the Table it can be seen that the greatest amount of press juice and correspondingly the greatest dry matter content of the press juice is achieved by the invention.According to our hypothesis an important role is played in this by the opening up of the cells and tissues of the green vegetable matter, by the degree of pulping and by the circumstance that in the course of mechanical opening-u p the material being processed is not significantly heated up or rather (in the preferred embodiment) the utilisation of the surface-active materials provides sufficient protection against local overheating.

An experiment similar to the above was performed with so-called Coastal Bermuda grass (Cynodon dactylon). The dry matter content of the raw vegetable material was approximately 30%. This raw material could not be processed at all with a Rietz disintegrator because right at the beginning of charging the apparatus, it became clogged and could not be operated.

Using an Owens disintegrator and pressing out the opened-up material through a Stord press at 3 r.p.m., the press output was 378 kglh, the press juice yield 47.1% and the moisture content of the press residue 62%.

The above mentioned raw vegetable matter was passed once through the apparatus according to the invention and was pressed out on a Stord press; the following data were obtained: Press output at 3 r.p.m. 486 kg/h Yield of press juice 52.2% Moisture content of the press residue 57.8% It is ascertainable from these data also that the improved output is accompanied by an improved press juice yield and correspondingly, the moisture content of the press residue is significantly reduced which enables a significant heat energy saving to be made in the drying of the fibrous fraction.

The aspect of the invention relating to the apparatus is illustrated by way of a preferred embodiment with reference to the accompanying drawings wherein: Figure 1 is a longitudinal part section, part elevation of the apparatus, Figure 2 is a vertical cross-section of the apparatus shown in Figure 1 taken at right angles thereto, Figure 3 is an enlarged detail view, partly in sectioned partly in elevation showing the breaking hammers and the oppositely located breaking surface, and Figure 4 is a developed plan view on an enlarged scale of the grinding liner.

Referring to the drawings, a preferred embodiment of apparatus according to the invention comprises a housing 1 provided with tangentially arranged inlet and outlet ducts 2 and 3, respectively, and a working or grinding chamber 4. In the casing 1 there is a main shaft 5 driven by means not shown to which shaft are keyed discs 6. Bearing shafts 7 passed through the disc 6 oscillatably journal breaking hammers 8 made from sheet material. Journalling openings 9 are formed opposite the breaking hammers 8, whereby in the event of wear of the hammers they can be readily removed and exchanged or turned over. The breaking hammers 8 are threaded on bearing shafts 7 alongside each other with the aid of spacer rings 10. The rotor of the apparatus is constituted by the discs secured on the main shaft 5, the bearing shafts 7 passed through the discs and the breaking hammers 8 themselves.When the main shaft 5 rotates the hammers 8 take up a radial position as a consequence of the centrifugal force and thus constitute a "breaking line" of the rotor.

The number per row or line of the breaking hammers 8 is selected so that the longitudinal dimension of the rotor should be greater than or at least equal to the diameter of the rotor.

Opposite the end face of the breaking rows or lines formed by the pivotally journalled hammers 8, grinding liners are disposed in the grinding space. The liners 11 extend, in relation to the direction of rotation of the rotor, from the inlet duct 2 to the outlet duct 3 along an arc of about 1800. The grinding liners 11 are fixedly secured to the interior of the housing 1. Guiding channels 12 are machined into the working surfaces of the grinding liners 11. The guiding channels 12 start from the vertical bisection line of the working surfaces of the grinding liners 11 and extend in opposite directions from there (to the right and to the left) towards the edges of the grinding liners.The grinding channels 12 extend at an acute angle, in the illustrated embodiment at 80 , with the vertical bisection line of the working surface of the grinding liners 11.

In the illustrated embodiment, the grinding liners 11 are so disposed that, in the direction of rotation of the rotor, along the first arcuate segment of 90" the apex of the acute angle made by the guiding channels with the vertical bisection line of the grinding surface opposes the direction of rotation of the rotor, but thereafter the apex of this included angle between the vertical bisection line and the guide channels point in the same direction as the direction of rotation of the rotor. As can been seen from Figure 4, the machined guide channels 12 have apices forming an acute angle with the bisection line which are offset from. each other to ensure that the individual channels are separated from each other. The flanks 13 of the guide channels 12 form a cutting edge with the grinding plane of the liners 11.

The driven main spindle 5 is sojournalled in the housing 1 that the gap between the end surface of the breaking line or row constituted by the oscillatably journalled hammers 8 of the rotor and the grinding surface of the liner 11 decreases from the inlet duct 2 to the outlet duct 3, viewed in the direction of rotation of the rotor. In other words, the main shaft 5 is journalled eccentrically and the gap is designated in the drawings by 14.

In the illustrated preferred embodiment, the eccentricity of the main shaft 5 is so chosen that the gap 14 should continuously decrease from the inlet opening or duct 2 along the first arc of 90 , taken in the direction of rotation of the rotor and thereafter should remain constant to the beginning of the outlet duct 3. The smallest dimension of the gap is a determinant of the fibre length of the opened-up material.

Although this is not shown in the drawings, the outlet duct 3 may also be provided with a regulating valve.

The direction of rotation of the rotor is indicated by an arrow.

In operation, the comminuted, expediently cut green vegetable matter is continuously passed into the inlet duct 2 from where the rapidly rotating (40-100 misec) breaking line or row formed from the oscillatably journalled breaking hammers 8 entrains the material and pulls it into the tapering or converging grinding space towards the grinding liners 11. The obliquely pressing rising guide channels 12 of the grinding liners 11 act to prevent that the breaking hammers 8 should entrain the green material compressed in the converging space along the grinding surface of the liners 11 and thus to pass by the shortest possible route to the outlet duct 3. The guiding channels 12 spread the arriving green material out in two directions along the upper grinding surface of the grinding liner 11 while at the same time, the cutting edges 13 of the flanks of the guiding channels 12 form a cutting angle with the rotary breaking hammers 8 effectively to cut the green material.

During processing the green material which is becoming pulpy, the path of advance of the green material is provided as a positively guided or forced path by the channels 12 which channels thus always guide the material into the path or line of action of the breaking hammers 8. The angle of inclination of the guiding channels 12 causes the green material, which is in a partly shredded and partly pulped state, to be braked by and delayed in the channels, whereby to create a kind of damming effect. In this way, the green vegetable matter tends to fill the channel, whereupon the impact force from the breaking hammers 8 is intensively exerted on it, as is the cutting effect of the cutting edges 13.The impact from the hammers in the guiding channels 12 on the congested green material causes an increases in pressure exerting a kind of stamping pressure on the pulpy material as a consequence of which the protein-containing liquor or juice is liberated from the plant cells. After the green material has progressed along in an arc-length of about 90" in the apparatus, the stalks and tissues of the green plants are broken up and the fibres become open.

In the lower part ofthe grinding liner 11, the guiding channels 12 run in a downwardly converging direction and the breaking hammers 8 guide the pulped material to the centre of the guiding surface of the grinding liner and towards the outlet duct 3. Naturally, as a consequence of the impact from the hammers 8 further pressure is exerted on the material advancing along the guiding channels 12 as a consequence of which the cells tissues and fibres are further opened up.

It is not possible for the guiding channels 12 to be clogged up because as a result of the impacts from the breaking hammers 8 the material cannot become stationary in the guiding channels 12; instead, it is forced to advance under pressure. At the same time, the guiding channels cool the pulpy material moving therein because their increased surface area provides a cooling and heat-removing effect. In this way, the proteins in the opened or pulped material advancing along the guiding channels 12 are prevented from precipitating out.

The fibre length or fibre dimensions which are important from the point of view of fodder cake, are ensured or regulated by the gap between the grinding surfaces of the liners 11 and the hammers 8.

Advantageously this can be so chosen that the ratio of the gap measured at the inlet duct 2 and at the outletduct3 respectively should be 10:1.

Claims (8)

1. Apparatus for opening up green vegetable matter by mechanical means, comprising a grinding chamber provided with a grinding surface and accommodating a rotor carrying oscillatably suspended breaking hammers, a housing defining the boundaries of the grinding chamber and provided with an inlet duct and outlet duct, wherein the working surface of the grinding chamber is constituted by a lining which is provided with mutually parallel guiding channels extending in two opposed directions from, and at an acute angle with, the vertical bisection line of the grinding surface towards the left-hand and right-hand edge respectively of the said lining; and between the said working surface of the said lining and the breaking line or row formed by the freely oscillatably journalled breaking hammers there is a grinding gap which, in the direction of the rotation of the rotor, decreases in size from the inlet duct towards the outlet duct.

2. Apparatus according to claim 1 wherein the points of intersection of said guiding channels with the said vertical bisection line of the working surface are offset with respect to each other on either side of said bisection line.

3. Apparatus according to claim 1 or claim 2 wherein the said vertical bisection line makes an acute angle of 80" with the guiding channels.

4. Apparatus according to any preceding claim wherein the said gap between the working surface of the said lining and the envelope of the tips of the oscillatably journalled breaking hammers converges, in the direction of rotation of the rotor, along an arc of 90" from the inlet duct towards the outlet duct and thereafter is of constant size to the outlet duct.

5. Apparatus according to any preceding claim wherein in the direction of rotation of the rotor, the ratio of the size of the gap after the inlet duct and before the outlet duct is 10:1.

6. Apparatus according to any preceding claim wherein the length of the breaking line or row formed from the oscillatably journalled breaking hammers, that is to say, the length of the rotor, is greater than or equal to its diameter.

7. Apparatus according to any preceding claim wherein the breaking hammers are formed with journalling openings arranged oppositely thereto.

8. Apparatus according to claim 1 substantially as herein described with reference to and/or as shown in the Examples and/or accompanying drawings.