A DEVICE FOR COMPRESSING FIBRE MATERIAL, IN PARTICULAR DRIED GREEN FODDER, INTO BALES

Abstract: A device for compressing dried green fodder or such like fibre material to form bales includes a pressing screw (4) rotatably mounted in a compression channel (2). The dis­ charge end of the screw blade of the pressing screw (4) ter­ minates in a circle sector shaped plane (17) extending per­ pendicular to the screw axis along an angle of at least 15° and being preceded by a blade portion (16) of gradually increasing thickness. This circle sector shaped plane (17) orients the fibres in planes perpendicular to the screw axis, so that the bales will have a high density while the coherence between the fibres is not increased too much. To keep the density constant along the entire length of the bales a back pressure means (5), movable in the compression channel (2), is controlled so that the back pressure exerted by said back pressure means (5) decreases when moving away from the screw end.

Description: A device for compressing fibre material, in particular dried green fodder, into bales. The invention relates to a device for compressing fibre material, in particular dried green fodder, into bales, including a material feed debouching into a compression channel in which a compression means may be operated, said compression means having the form of a rotatable compression screw conveyor. The main part of the dried green fodders intended to be fed to ruminants is ground, compressed and formed to rodlike pieces, cubes or chips. The high density and good manageability thereof are considered to be practical advantages. It is well known that the digestive organs, particularly the rumen of the ruminant will only function properly if at least part of the fodder ration consists of particles having a fibrous structure, i.e. having relatively large length and thickness dimensions. It will be clear that the above-mentioned pieces consisting of ground particles do not have such a structure. The ground and compressed rodlike pieces, cubes or chips entail the further drawback of requiring rather much energy for the production thereof. Although bales having the structure of particles may be obtained by using a known baler for compressing unground dried green fodder such bales have a relatively low density (for instance about 250 kg/m3) thus requiring much room when stored and transported. An increase of the density would however be conducive to the obtainment of a product compressed to such a degree that a ruminant will not be able to loosen. the material whereas there would also be created considerable problems in technical respect. An object of the invention is to provide a device of the type mentioned above by means of which bales having a considerably higher density (for instance about 500 kg/m3) may be compression formed while retaining the structure so that a ruminant will nvertheless be able to loosen the material from the bale in an easy manner. According to the invention the discharge end of the screw blade of the compression screw terminates in that effect into a plane perpendicular to the axis of the screw and having the shape of a sector of a circle, said plane extending ove an angle of 0 at least 15 and being preceded by a part of the blade having a gradually increasing thickness. The invention is based on the recognation that when imparting a planar surface to the end of the screw without changing the distance between the last turn of the screw and the last turn before last the fibres will be oriented in planes perpendicular to the axis of the screw and that consequently a much higher density may be imparted to the bales without increasing the coherence between the parts too much. Such an orientation of the fibres in parallel planes perpendicular to the direction of compression entails moreover that the expelling of air will be better. Furthermore it is important that the density will be constant over the entirelength of the bales. In case for obtaining the back pressure when compressing, only use would be made of the friction between the fodder material and the walls of the housing the density in that part of the bale that has been compressed first would be not as high as the density in the subsequently compressed part. This problem may be solved by providing within the compression chamber a back pressure means capable of being moved back and forth, said back pressure means being in alignment with the screw and cooperation with a control mechanism controlled by the back pressure on the screw in such a manner that the back pressure exerted by the back pressure means decreases in dependency upon the force exerted upon the screw. By means of such a device the sum total of the back pressure caused by the friction between the material to be compressed and the walls of the housing and the back pressure caused by the back pressure means may be kept rather closely constant so that the density over the length of the bale remains the same. An other possibility to keep the variations of the density¯ over the length of a bale not too large consists in that within the compression chamber there has provided a back pressure means ca pable of being moved back and forth, said back pressure means being in alignment with the screw and cooperating with a regulating means controlled in dependency upon the position -of said back pressure means in such a manner that the back pressure ex-erted by the back pressure means decreases upon displacement of the back pressure means in the direction opposite to the end of the screw. In both cases the density may be adapted in a certain degree to the nature of the material. The back pressure means comprises for instance a hydraulic piston cylinder assembly having an oil feed line in which a valve has been provided, said valve being controlled by a feeder for ascertaining the position of the piston within the cylinder. For an appropiate discharge of the formed bales there will be provided downstream of the end of the screw and adjoining the compression chamber an ejection means and a knive movable in a direction traversely to the axis of the screw. The invention will now further be described in detail with reference to the drawings representing an embodiment of the invention. Fig. 1 represents a perspective view of the device. Fig. 2 represents a longitudinal section. The shown device is intended for the compression of dried unground green fodder into bales having a relatively high density (about 500 kg/m3). The device includes a feed bin 1 the bottom part of which debouches into a compression channel 2. Within a portion 2a of this channel there has been provided a compression screw conveyor 4 driven by a hydromotor 3. Within this portion 2a the housing of the compression channel 2 constitutes a close encasement of the screw 4. On the inner surface of the portion 2a of the housing there have been mounted helical ribbons 18. These ribbons have a winding running opposite to the blade of the screw 4. At the location at which each ribbon intersects the compression screw 4 the angle between the side of the ribbon facing the discharge end of be 0 the compression channel and the screw 4 will least 900. The ribbons 18 assure that the fibre material to be compressed within the compression channel will not rotate. As a consequence of the 0 said angle of at least 90 the fibre material will not be cut or shredded. Approximately at the level of the end of the screw the cross sectional shape of the housing 2 changes from a circular shape (2a) to a rectangular shape (2b). Within the portion 2b of the housing there has been provided a back pressure plate 5 that may be moved back and forth along the axis of the screw 4 by means of a hydraulic cylinder 6. With said cylinder there has been connected an oil line 7 having mounted therein a valve 8. This valve is controlled by a feeler for as -certaining the position of the piston within the cylinder 6. The connection between the feeler and the valve 8 has been indicated by the reference numeral 9. Part of the vertical side wall of the rectangular portion 2b of the channel 2 is constituted by an ejection plate 11 which has been connected to an ejection cylinder 12. Adjoining the side wall opposite to the plate 11 there is a discharge channel 13. Next to said cylinder 12 at the side facing the screw there has been provided a knife 14 connected with a hydraulic cylinder 15 As will be apparent from fig. 2 in particular the end of the screw 4 tapers conically somewhat, whereas the last term of the blade possesses a gradually thickened end portion 16 (over about 1800) merging into a plane 17 perpendicular to the axis of the screw and having the shape of a sector of a circle. The latter planar surface 17 extends over about 300 (at least 150). The distance between the last turn provided with the thickened blade portion and the last but one turn is constant i.e. the thickened end portion becomes gradually thicker in the direction of the discharge end of the screw. In cooperation with the adapted form of the housing 2a the conical end portion of the screw assures a certain densification upon conveying the green fodder through this portion of the compression channel. As a consequence of the thickened end portion 16 and the planar end surface 17 the green fodder particles are oriented in planes perpendicular to the axis of the screw. The sheathlike stems are pressed out each other so that the air is expelled from the stems. The thus oriented material is pressed against the back pressure plate 5. Upon exceeding a force exerted by the cylinder 6 the plate 5 will gradually be pushed aside, The friction exerted by the walls of the rectangular part 2b of the compression channel on the green fodder causes likewise a back pressure with respect to the pressure exerted by the screw 2. This friction back pressure increases upon the increase of the amount of material in the rectangular portion of the compression channel. The aim is to maintain a constant sum total of the back pressure exerted on the one hand by the back pressure plate 5 and on the other hand by the walls of the rectangular compression channel 2b. Since the frictional forces are gradually increasing, the cylinder 6 will have to exert a gradually decreasing back pressure upon displacement of the back pressure plate 5. In the shown embodiment this is attained by controlling the valve 8 in the oil line 7 to the cylinder 6 in dependency upon the position of the piston in the cylinder 6. By way of example it has been indicated that in case of a compression channel portion 2b having a sectional dimension of 28 x 28 cm the back force exerted by the plate 5 decreases from 9000 N to 5000 N. Since the sum total of the back pressure is substantially constant over the entire displacement range of the back pressure cylinder the density of the material in the compressed bale will not vary either. In view of the orientation of the green fodder particles in planes perpendicular to the axis of the compression chamber the air may easily be discharged from the stems and the bales when compressing the same. The density may be extremely high (for instance about 500 kg/m7) without reaching too strong a choherence between the parts thereof. Likewise the uniformity of the density aids to the high value of the density that may be ch-osen without causing difficulties for a ruminant when loosening the material from a bale. At a density of about 500 kg/m3 a 20 kg bale may easily be handled in view of the small dimensions thereof (for instance 2.8 dm x 2.8 dm x 5 dm). The storage and transportation costs will be relatively low. The uniformity of the density moreover aids to the stability of a stack of bales. In a more acc#rt# ccrsWruction for maintaining a constant sum total of the back pressure the force exerted on the compression screw 4 is measured (for instance by means of strain gauges) while a control mechanism for the back pressure trans is controlled by a signal corresponding to said force in such a manner that the back pressure exerted by the back pressure means decreases and the sum total of the back pressure remains constant. When the back pressure plate 5 has reached its final position the screw 4 is stopped whereupon the knife 14 is pushed forth by the cylinder 15 and the bale thus cut off is pushed by the ejection plate 11 by means of the cylinder 12 into the discharge channel 13. After the return of the ejection plate 11, the back pressure plate 5 and the knife 14 to their original positions the screw 4 is again put into operation. Usually the bales will be wrapped in a plastic foil. The bale remains compressed in the channel 13 until completely enveloped by the wrapping: the wrapping thus keeps the material in a compressed condition. An additional advantage of the disclosed device resides in the fact that the compression density may be regulated continuously and may be adapted in a certain degreee to the nature of the product. The far most important effect of the invention is however that without grinding the green fodder a high density may be attained whereas the coherence of the material is nvertheless not too strong. (claims)

Claims: CLAIMS 1. A device for compressing fibre material, in particular dried green fodder, into bales, including a material feed debouching into a compression channel in which a compression means may be operated said compression means having the form of a rotatable compression screw conveyor characterized in that the discharge end of the screw blade of the compression screw (4) terminates in a plane (17) perpendicular to the axis of the screw and having the shape of a sector of a circle, said plane (17) extending over an angle of at least 150 and being preceded by a part (16) of the screw blade having a gradually increasing thickness. 2. The device of claim 1 characterized in that within the compression chamber (2) there has been provided a back pressure means (5) capable of being moved back and forth, said back pressure means being in alignment with the screw (4) and cooperating with a control mechanism controlled by the back pressure on the screw in sich a manner that the back pressure exerted by the back pressure means decreases in dependency upon the force exerted on the screw. 3. The device of claim 1 characterized in that within the compression chamber (2) there has been provided a back pressure means (5) capable of being moved back and forth, said back pressure means being in alignment with the screw (4) and cooperating with a regulating means controlled in dependency upon the position of said back pressure means in such a manner that the back pressure exerted by the back pressure means decreases upon displacement of the back pressure means in the direction opposite to the end of the screw. 4. The device of claim 3 characterized in that the back pressure means (5) comprises a hydraulic piston-cylinder assembly (6) having an oil feed line (7) in which a valve (8) has been provided, said valve being controlled by a feeler for ascertaining the position of the piston within the cylinder (6). 5. The device of anyone of the preceding claims characterized in that at downstream of the discharge end of the screw and adjoining the compression chamber (2) there have been provided an ejection means (11) and a knife (14) movable in a direction traversely to the axis of the screw (4).

Inventors: LEUTSCHER, HENDRIK JACOB, OGINK, JOHANNES JOSEPH MARIA, ROBBEN, JOHAN BERNARD HENDRIK
Applicants: INSTITUUT VOOR BEWARING EN VERWERKING VAN LANDBOUWPRODUKTEN
Application year: 1979
Main classification: B30B9
IPC codes: A01F15, B30B9