PLANT CUTTING UNIT

Abstract: A unit for cutting grass or similar plants incorporates a tool (1) which can rotate in relation to the unit and which has a holder (4) and one or more devices (6) for processing the plants. These processing devices are flexible or elastically pliant and interact with a rigid or hard bed knife (2) for disintegrating, in the desired cutting range, plant parts which are conducted into an interface zone between the bed knife and the rotating, flexible processing devices. The holder consists of a cylindrical tube with a mainly smooth jacket surface from which the processing devices project.

Description: PLANT CUTTING UNIT BACKGROUND OF INVENTION The present invention refers to a unit for cutting plants, particularly those of a type similar to grass, incorporating a tool which can rotate in relation to the actual unit, the said unit having a holder on which are arranged one or more devices for processing the plants, these devices being flexible and interacting with at least one rigid counter-element of bed-knife type (hereinafter referred to as the bed knife) mounted on the unit so as to disintegrate, in the desired cutting range, individual plant parts which are conducted into a contact or interface zone between the bed knife and the above-mentioned, rotating processing devices. PREVIOUS TECHNOLOGY Units of this type are previously known through, for example, American patent letters Nos. 2 449 042, 2 212 873 and 1 8 99 439. Although these units have proved to be advantageous due to the fact that the flexible processing devices reduce the noise and also reduce, to a certain extent, the risk of accidents, a great deal still remains to be desired with regard to measures intended to prevent accidents. As a result of the manner in which the holders in the units in accordance with the American patent letters are designed, a hand or a foot can unintention¬ ally enter into the voids in the holder and, when the holder rotates, be subjected to powerful breaking and crushing forces. According to, for example, American patent letter 2 449 042 the holder consists of a comparatively slender central shaft, along which are mounted separate discs which carry strips which, in turn, carry the processing devices at a radial distance outside the central shaft, in addition to which these rigid strips are OiV.PI separated from each other in the circumferential direction of the holder so that each individual strip extends in a free span between two adjacent discs. According to American patent letters 2 212 873 and 1 899 439, the processing devices are located on blades which are cantilevered out from a slender central shaft. BRIEF DESCRIPTION OF THE INVENTION The purpose of the present invention is to further develop the unit initially described above so as to eliminate, as far as possible, risks of accidents and so as to achieve a simple and cheap design for the tool. This purpose is achieved as a result of the fact that the holder has a cylindrical shape with a mainly uniform jacket from which the processing devices project. As a result of this holder design, the surface of the holder jacket forms a non- injurious deflector which prevents hands or feet from getting caught in the holder. BRIEF DESCRIPTION OF DRAWINGS A description of a number of designs of the invention are presented, as examples below, with references to the appended drawings. On these drawings, Fig. 1 is a schematic side view illustrating a tool with a bed knife incorporated in the unit according to the invention, Fig. la is an enlarged detail from Fig. 1, Fig. 2 is a partly cut longitudinal view of a prelimin¬ ary design of a cylindrical tool according to the invention, Fig. 3 is an end view of the same tool, Fig. 4 is a cross-sec¬ tion through another design of the tool together with the associated bed knife, and Fig. 5 and Fig. 6 are longitudinal and end views respectively showing a further version of the tool. DETAILED DESCRIPTION OF PREFERRED DESIGNS The unit illustrated in Fig. 1 and Fig. la incorporates a tool designated in its entirety with the digit 1 and a bed knife . designated with the digit 2. The tool and the bed knife are mounted on a frame which constitutes an integrated part of the actual unit but which is not presented on the drawing. This frame can be wheel-mounted to advantage so that it can be driven on the base 3 on which the grass or plants grow. In the example presented, the tool 1 incorporates a holder in the form of a core-type cylinder 4 which can, to advantage, have the shape of a tube finished with, for example, nylon or the like. Numerous processing devices 6 in the form of bristles, which are flexible or elastically pliant in a direction at right angles to their length, are mounted on the cylinder or on the jacket surface of the tube. The bristles 6 thus project radially out from the cylinder jacket. The bed knife 2 has a contact edge or contact surface 7, the longitudinal axis of which is, in all essentials, parallel to the centre or axis of rotation 8 of the cylinder. In this example, the bed knife 2 has the shape of a long strip incor¬ porating not only the contact edge 7 along one of the longitu- dinal sides of the strip but also a second contact edge 7a at the opposite longitudinal side of the strip, the strip being mounted in a removable manner on the unit frame in such a way that either one or the other edge interacts with the bristles or processing devices 6. As a result, the strip can be turned and used once again after one of the contact edges has become worn out or destroyed. The actual unit is normally used in the forward direction as indicated by the arrow A in Fig. 1. The cylinder tube 4 can rotate in the direction of the arrow B. The bed knife strip 2 is placed in all essentials under the cylinder tube 4 or the actual tool 1. As a result, the relevant processing devices or bristles 6 in the immediate vicinity of the bed knife strip 2 or the strip's active contact edge 7 move in a tangential direction which is opposite to the normal direction of movement of the unit or the bed knife (the arrow A) . The contact edge 7 of the bed knife strip 2 is located somewhat behind the imaginary vertical plane C which runs through the cylinder's rotation axis 8, as can be seen from the angular difference between the plane C and the radial dash-dotted line D between the contact edge 7 and the rotation axis 8. This dis¬ placement of the contact edge in a direction backward from the vertical plane C causes the blades of grass to rise or stretch before they come in contact with the edge 7. The tool 1 and the bed knife strip are mobile in relation to each other and can be adjusted in different positions in rela- tion to each other so as to make it possible to compensate for the wear on the processing devices or the bristles. The length of the bristles 6 can be adjusted in such a way that the bristles are initially given a greater length than the distance between the contact edge 7 and the jacket surface 5 of the cylinder tube 4. The tool Is then caused to rotate. Depending on the materials selected in the bristles and in the bed knife strip respectively, the tips of the bristles are worn off after a certain period of rotation so that the length of the bristles agrees, in all essentials, with the shortest distance between the contact edge 7 and the jacket surface 5. Some suitable form of plastic is the most advantageous material to use in the bristles 6 although metallic material can also come in question. Combinations of metallic and plastic materials are also conceivable. The bed knife strip 2 should preferably be finished with metal, for example conventional steel. The bristles can be cast into the cylinder 4 which can consist of plastic material. Alternatively, the bristles can be attached to strips which are then fixed to the cylinder. What is impor¬ tant is that the cylinder must, with the exception of the flexible bristles, have a mainly uniform or smooth jacket. "Mainly uniform" in this case means a uniformity or lack of deep cavities such that the risk of causing injuries to hands or feet which unintentionally come in contact with the tool and its holder is negligible. The unit described operates as follows. The contact edge 7 of the bed knife strip 2 is arranged at a height, which is suitable for the purpose, above the base 3. Furthermore, the tool 1 and the bed knife are set in such a way that the tips of the bristles 6 are in the immediate vicinity of the edge 7 and that no noteworthy play occurs between them. The tool or the cylinder tube is set in rotation in the direction of the arrow B at the same time as the unit is moved in the direction of the arrow A. This causes the blades of grass which project vertically from the base 3 to be fed into the interface zone 9 between the tips of the bristles and the edge* of the bed knife strip 7, whereupon the blades of grass in the cutting range located at the height determined by the edge 7 above the base are subjected to a disintegrating operation which consists of a combination of beating, tearing, cutting and abrading the biomass of the blades of grass until they are ruptured. The disintegration operation becomes more efficient the higher the speed at which the tool rotates. Consequently, it is preferable to operate the tool at a high or very high speed, for example in the speed range 3 000-5 000 rev/min. It should be obvious from this description that no skeletal injuries but at worst grazes can occur on limbs which uninten¬ tionally come in contact with the bristle-type flexible and elastically pliant processing devices 6, even if the limbs in question should enter the interface zone between the processing devices and the bed knife. The bed knife strip 2 incorporates, in the design according to Fig. 1, contact edges or surfaces 7, 7a which are gently rounded so that the tips of the bristles are not abraded unnecessarily rapidly. Fig. 2 and Fig. 3 provide a better illustration of how the tool cylinder has bristles 6 along its entire jacket surface and how the cylinder itself consists of a tube 4. The motor which is required for rotating the tube in relation to the unit frame can be installed inside the tube. The motor can, to advantage, be of silent electric or hydraulic type. Fig. 4 illustrates a design form in which the jacket surface of the cylinder tube 4 is not completely covered with bristles but has six different groups of bristles 6' which extend like long narrow combs in the axial direction of the cylinder tube. In this case, the bristle devices collaborate with a bed knife 2' which has a U-shaped cross-section. This has comparatively sharp-edged contact surfaces 7' and 7a' which can be applied when the requirements for gentle action vis-a-vis the bristle devices are small. It is thus possible to use more or less sharply ground contact surfaces or edges. Fig. 5 and Fig. 6 Illustrate a design which also incorporates a number of longitudinal groups of bristle devices 6". In this example, the various groups extend in helical configurations around the jacket surface of the cylinder tube, suitably in such a way that at least some part of some group is always in contact with the bed knife strip or bed knife 2". This provides -BUR OM the tool with uniform and smooth running characteristics when it is in operation and interacting with the bed knife strip. In addition to the previously mentioned advantage of reducing the risks of injury to a minimum, the plant cutting unit accord¬ ing to the invention also offers the advantage of silent opera¬ tion, particularly if the tool cylinder is manufactured of nylon which is, in itself, a sound-absorbent material, at the same time as a silently operating electric motor installed inside the tube is used for operating the unit. Obviously the invention is not limited to the designs described and presented on the drawings. Although the invention has been described with bristles as the processing devices, more or less extensive rubber strips or plates, which are mounted on, for example, the jacket surface of a cylinder in the same way as the bristles presented here and which interact with a rigid bed knife unit in an analogous manner, can be used instead of the bristles. -BURE OMP

Claims: Patent claim 1. A unit for cutting plants, particularly those of a type similar to grass, incorporating a tool (1) which can rotate in relation to the actual unit, the said unit having a holder (4) on which are arranged one or more devices (6) for processing the plants, these devices being flexible and interacting with at least one rigid counter-element or bed knife (2) mounted on the unit so as to disintegrate, in the desired cutting range, individual plant parts which are conducted into a contact or interface zone (9) between the bed knife and the above-mentioned processing devices, c h a r a c t e r i z e d by the fact that the holder (4) is shaped as a cylinder with a mainly uniform jacket from which the processing devices (6) project. 2. A unit in accordance with Claim 1, c h a r a c t e r i z e d by the fact that the processing devices consist of bristles (6). 3. A unit In accordance with Claim 2, c h a r a c t e r i z e d by the fact that the cylinder has bristles (6) over its entire jacket surface (5). 4. A unit in accordance with Claims 1 or 2, c h a r a c t e r ¬ i z e d by the fact that the processing device or devices (6") are arranged in at least one helical configuration along the cylinder jacket. 5. A unit in accordance with Claim 1, c h a r a c t e r i z e d by the fact that the bed knife, which has the shape of a lengthy strip (2), has contact edges (7, 7a) which are suitable for interacting with the above-mentioned processing devices (6) along both its longitudinal sides, and by the fact that the strip is attached in a removable manner to the unit and in such "BUREA a way that either one edge or the other interacts with the processing devices. 6. A unit in accordance with Claim 1, c h a r a c t e r i z e d by the fact that the cylinder has the shape of a tube (4) . 7. A unit in accordance with Claim 6, c h a r a c t e r i z e d by the fact that a motor for rotating the tube in relation to the unit is installed inside the tube. BUREA OMPI "

Inventors: SUNDBERG STIG, SUNDBERG, STIG
Applicants: LAGERGREN BENGT AB, BENGT LAGERGREN AB
Application year: 1982
Main classification: A01D35
IPC codes: A01D34