Method for pressing bales and baler for using that method

Abstract: During the pressing of bales in a baler, a portion of a press channel (1) in front of a retracted press ram (2) is in each case completely filled with material to be compacted. During compacting, the pressure forces exerted on the press ram (2) have a resultant which intersects the side (3) of the press ram (2) directed in pressing direction (11) below the center (7) thereof or below the center of the press channel section at the location of that side (3) of the press ram (2). The press ram shows less tendency to tilt, as a consequence of which the press ram guide is less loaded and less friction occurs between the press ram and the press channel. As a result, the bale is compressed more properly and the press ram guide wears less.

Description: The invention relates to a method for pressing bales according to the preamble of claim 1 and to a baler according to the preamble of claim 6. Such a method and such a baler are known from US-A-4 594 942. In this known method and baler large pressing forces are exerted since the space in the pressing channel between the retracted pressing ram and previously pressed material is filled completely before the pressing ram is activated for pressing material in the pressing channel between the retracted pressing ram and previously pressed material. A particular problem is, that such large pressing forces entail a substantial amount of friction and wear between the pressing ram and guides parallel to the pressing channel. From US-A-3 541 949 and US-A-3 641 925, as well as from US-E-29 278, it is known to exert a pressure force in a waste press along a line of action which intersects the pressure surface of the press ram below the center thereof or of the press channel. According to these documents, a press stroke is made each time when a volume of waste has gathered in front of the filling opening of a baling chamber which volume is smaller than the free volume of the press channel when the press ram is in an extreme position retracted from the priorly pressed baling goods. Thus, in each case, prior to the compacting operation, exclusively a lower portion of the baling chamber is filled with material to be pressed. The bales produced in this manner exhibit a relatively poor integrity and, when a rectangular press channel is used, are generally trapezoidal. From US-A-3 368 478 it is also known to compact waste by exerting a force on a press ram which intersects the pressure surface of the press ram below the center thereof. However, in this case, no bales are formed in a press channel, but the waste is pressed into a container which is open at the top. The object of the invention is to provide a method and an apparatus in which less friction and wear occur, but without entailing the disadvantages of relatively poor integrity of the bales and, when a rectangular press channel is used, the formation of generally trapezoidal bales. According to the invention, this object is realized by carrying out a method according to the preamble of claim 1 in accordance with the characterizing part of claim 1. A baler according to the preamble of claim 6 can be adapted for use in a method according to claim 1 by designing it in accordance with the characterizing part of claim 6. The invention is based on the insight that when the press channel is being filled, baling goods, such as paper, synthetic materials or rags, fall tendentially faster according as the packing thereof is denser, as a result of which the baling goods in lower portions of the press channel generally have a denser packing than the baling goods in upper portions of the press channel, and that, consequently, the resistance exerted by the baling goods during compacting is greater in lower portions of the press channel than in upper portions of the press channel. Because the resultant of the pressure forces exerted on the press ram intersects the side of the press ram directed in pressing direction below the center thereof and/or below the center of the press channel section, the resultants of the pressure forces and the resistance produced by the material to be compacted lie closer together than with the known method, wherein the resultant of the pressure forces exerted on the press ram coincides with the center line of the press channel. As a result, when the method according to the invention is used, the press ram shows less tendency, if at all, to tilt forwards during compacting and work itself upwards against the material to be compacted. In turn, this has as a consequence that when the invention is used, the press ram guide is less loaded and less friction (and hence less pressure loss) occurs between press ram and press channel. As a result, the press ram guide wears less and more net pressure force remains, so that in particular lower parts of the bale to be formed are compressed more properly. The press channel can be horizontally directed or extend both horizontally and vertically, i.e. extend in an inclined manner. An inclined press channel, too, involves the phenomenon that the paper of a denser packing will gather at the bottom of the press channel. According as the press channel is directed more vertically, the distance between the vertical center line of the press channel and the line along which the resultant of the forces exerted on the press ram acts should be chosen to be smaller. The invention can be used in balers whose filling opening where the filling shaft opens into the press channel is closable by a pre-pressure valve or the like, as well as in balers whose filling shaft cannot be closed other than by the press ram and wherein for instance the press ram and cooperating cutting blades and counter-cutters provide a separation of baling goods to be compacted during a particular press stroke and pressing goods to be compacted later. Specific embodiments of the invention are described in the dependent claims 2-5 and 7-11. The invention will hereinafter be further explained on the basis of an exemplary embodiment which is most preferred at the moment, while reference is made to the accompanying drawing showing a cutaway side elevation of a baler according to the invention. The baler according to the example shown has a horizontally extending press channel 1 wherein a press ram 2 with a side 3 directed in the pressing direction is displaceable forwards and backwards. A filling shaft 4 opens into the press channel 1 from above at an angle. For displacing the press ram 2 with force in a pressing direction (arrow 11), the baler comprises a press cylinder 5. For pressurizing the press cylinder 5, the baler comprises a hydromotor, driven by an electromotor 8, in a housing 9. The press channel 1 has a downstream portion 10 with a pinch-off apparatus 11 for clamping the baling goods transversely to the pressing direction. Owing to the resistance experienced by the clamped baling goods, this also forms, during the conveyance through the downstream portion 10 of the press channel 1, the medium for generating the counterpressure which is required for the pressing operation. At the location where the filling shaft 4 opens into the press channel 1, the filling opening is closable by means of a pre-pressure valve 13 which has the shape of a segment of a circle and is pivotable about a pivot 14 and operable by a working cylinder 15. For controlling the operation of, inter alia, the press cylinder 5 and the working cylinder 15 which drives the pre-pressure valve 13, the baler comprises control means, schematically indicated at 17, adapted to activate the press cylinder 5 to perform a press stroke each time when the pre-pressure valve 13 is closed, i.e. when the press channel 1 in front of the retracted press ram 2 is completely filled with material to be pressed. The filling shaft 4 is preferably provided with sensors for detecting baling goods in the shaft, permitting the control means 17, in response to the baling goods in the shaft reaching a level sufficient to fill the press channel 1 completely, to close the pre-pressure valve 13 and then to activate the press cylinder 5. The pressure forces that are exerted on the press ram 2 by the press cylinder 5, in operation, have a resultant 6 which intersects the side 3 of the press ram 2 directed in the pressing direction below the center 7 thereof and also below the center 12 of the press channel section at the location of the pressure side 3 of the press ram 2. In operation, material to be compacted is dumped into the filling shaft 4, causing an amount of material to gather above the closed pre-pressure valve 13. When the press ram 2 is in its retracted position, as shown, the pre-pressure valve 13 is opened and material to be compacted falls into the press channel 2 in front of the press ram 2. The material to be compacted falls tendentially faster according as the packing thereof is denser, so that in general, the material to be compacted has a denser packing in lower portions of the press channel 1 than the baling goods in upper portions of the press channel 1. When the material to be compacted has partly fallen into the press channel 1 and is partly located in the filling shaft before the pre-pressure valve 13, the pre-pressure valve 13 is closed, while the material to be compacted is pre-pressed until a specific amount is entirely located in the press channel 1. At the same time, the material to be compacted during the pressing cycle in question is separated from the material to be compacted during a next pressing cycle. Because the material to be compacted generally has a denser packing in lower portions of the press channel 1 than the baling goods in upper portions of the press channel 1, the resistance in lower portions of the press channel 1 during compacting is greater than the resistance in upper portions of the press channel 1. Owing to the feature that the resultant 6 of the forces exerted by the press cylinder 5 intersects the side 3 of the press ram 2 directed in pressing direction below the center of the mass of material to be compacted, the resultant 6 of the pressure forces and the resultant of the resistance (not shown) produced by the material to be compacted lie closer together than with the known baler, wherein the resultant of the forces exerted by the press cylinder coincides with the center line of the press channel. In the baler shown, the press ram 2 shows less tendency, if at all, to tilt forwards in pressing direction during compacting, depending on the material to be compacted. As a result, the press ram guide along the upper side and the lower side of the press channel 1 and of the press ram 2 is less loaded and less friction (and hence less pressure loss) occurs between the press ram 2 and press channel 1. Consequently, in particular the lower parts of the bale to be formed are compressed more properly and the press ram guide wears less. The pressure forces exerted by the press cylinder 5, in operation, are directed parallel to the press channel 1, so that they are optimally utilized for obtaining a highest possible pressure force. Instead of the press cylinder 5 shown, other drive means can be used as well, such as a toggle system, optionally in combination with a screw spindle. In the baler shown, the above-described position of the resultant of the pressure forces exerted during operation is obtained in a simple manner by suspending the press cylinder 5 so that its center line intersects the side 3 of the press ram 2 directed in pressing direction below the center thereof and also below the center of the press channel section at the location of that pressure side 3. The distance a between on the one hand the intersection between the resultant 6 of the pressure forces exerted during operation on the ram 2 and the side 3 of the press ram 2 directed in pressing direction, and on the other hand the center 7 of the side 3 of the press ram 2 directed in pressing direction or of the press channel section at the location of that side 3 of the press ram 2, is preferably at least 3 % of the height of the press channel 1. Particularly satisfactory results are achieved when the above-described distance a is within a range of 4-13 % of the height of the press channel 1, depending on the material to be compacted. This distance a can better be chosen to be slightly greater than optimum than slightly smaller than optimum, because a tendency, if any, of the press ram 2 to tilt backwards in pressing direction 2 is largely compensated by wheels 16 provided at the lower side of the press ram 2.

Claims: A method for pressing bales, in each case comprising the steps of: filling a space in a press channel (1) in front of a retracted press ram (2) from above with material to be compacted until said space is completely filled; then, by exerting pressure force on the press ram (2), displacing the press ram (2) in longitudinal direction of the press channel (1), with the material to be compacted being compressed and advanced in the press channel and offering a friction-induced resistance to the pressure force; and moving the press ram (2) back into said retracted position, characterized in that the pressure forces exerted on the press ram have a resultant intersecting the side (3) of the press ram (2) directed in the pressing direction (11) below the center (7) thereof or below the center of the press channel section at the location of said side (3) of the press ram (2). A method according to claim 1, wherein the distance between on the one hand the intersection between the resultant (6) of the pressure forces exerted by the drive means (5) during operation on the press ram (2) and the side (3) of the press ram (2) directed in pressing direction (11), and on the other hand the center (7) of the side (3) of the press ram (2) directed in pressing direction (11) or of the press channel section at the location of said side (3) of the press ram (2) is at least 3.5 % of the height of the press channel (1). A method according to claim 1 or 2, wherein the distance between on the one hand the intersection between the resultant (6) of the pressure forces exerted by the drive means (5) during operation on the press ram (2) and the side (3) of the press ram (2) directed in pressing direction (11), and on the other hand the center (7) of the side (3) of the press ram (2) directed in pressing direction (11) or of the press channel section at the location of said side (3) of the press ram (2) is 4-13 % of the height of the press channel (1). A method according to any one of the preceding claims, wherein during each pressing cycle, baling goods to be compacted during said pressing cycle are separated from baling goods to be compacted later. A method according to any one of the preceding claims, wherein in each case prior to the compacting operation by the press ram (2), the baling goods are pre-pressed in the press channel (1) in a direction approximately transverse to said pressing direction (11). A baler having a horizontally extending press channel (1) wherein a press ram (2) with a side (3) directed in pressing direction (11) is displaceable forwards and backwards, a filling shaft (4) opening into the press channel (1) from above, drive means (5) for displacing the press ram (2) with force in a pressing direction (2), wherein the pressure forces exerted by the drive means (5) during operation on the press ram (2) have a resultant (6) intersecting a side (3) of the press ram (2) directed in pressing direction (11), and control means (17) adapted to activate the drive means to carry out a press stroke each time when at least the press channel in front of the retracted press ram is completely filled with material to be compacted, characterized in that the drive means (5) and the press ram (2) are designed so that said resultant (6) intersects the side (3) of the press ram (2) directed in pressing direction (11) below the center (7) thereof or below the center of the press channel section at the location of said side (3) of the press ram (2). A baler according to claim 6, wherein the drive means comprise at least one press cylinder (5) and wherein the or each press cylinder (5) has a center line which intersects the side (3) of the press ram (2) directed in pressing direction (11) below the center (7) thereof or below the center of the press channel section at the location of said side (3). A baler according to claim 6 or 7, wherein the distance between on the one hand the intersection between the resultant (6) of the pressure forces exerted by the drive means (5) during operation on the press ram (2) and the side (3) of the press ram (2) directed in pressing direction (11), and on the other hand the center (7) of the side (3) of the press ram (2) directed in pressing direction (11) or of the press channel section at the location of said side (3) of the press ram (2) is at least 3.5 % of the height of the press channel (1). A baler according to one of claims 6-8, wherein the distance between on the one hand the intersection between the resultant (6) of the pressure forces exerted by the drive means (5) during operation on the press ram (2) and the side (3) of the press ram (2) directed in pressing direction (11), and on the other hand the center (7) of the side (3) of the press ram (2) directed in pressing direction (11) or of the press channel section at the location of said side (3) of the press ram (2) is 4-13 % of the height of the press channel (1). A baler according to one of claims 6-8, comprising means (4) for separating baling goods in the press channel (1) to be compacted and baling goods in the filling shaft to be compacted later. A baler according to claim 10, wherein said means (4) for separating baling goods in the press channel (1) to be compacted and baling goods in the filling shaft to be compacted later are designed as a pre-pressure valve (13) which in a first position clears the filling shaft (4) and in a second position forms a boundary of the press channel (1) closing the filling shaft, and which, when displaced from the first into the second position, moves towards the press channel for pre-pressing baling goods in the press channel (1).

Inventors: BOLLEGRAAF HEIMAN SALLE, BOLLEGRAAF, HEIMAN SALLE
Applicants: BOLLEGRAAF APPINGEDAM MASCHF, MACHINEFABRIEK BOLLEGRAAF APPINGEDAM B.V.
Application year: 1995
Main classification: B30B9
IPC codes: B30B9