A DEVICE FOR MOWING GRASS OR SIMILAR

Abstract: A lawn mower comprises a frame (4) and a rotor (5) rotatably journalled to the frame about a horizontal axis and provided with cutting members (6) adapted to co-operate shearingly, on rotation of the rotor, with an edge member (7) arranged on the frame. The cutting members (6) are pivotably connected to the rotor.

Description: A device for mowing grass or similar FIELD OF THE INVENTION AND PRIOR ART This invention is related to a device for mowing grass or similar, comprising a frame and a rotor rotatably journalled in the frame and provided with cutting members adapted to co¬ operate shearingly with an edge member arranged on the frame on rotation of the rotor. The invention relates in particular to a mowing device suitable for mounting on a vehicle, i.e. for large areas and being of an advanced embodiment. Prior mowing devices of the kind presented by way of intro¬ duction are normally designated "cylinder mowers". These are known to give an excellent mowing result but suffer from the disadvantage that they are very exposed to damages. The cutting members are normally produced in the form of edges extending helically and being secured rigidly to the rotor, said edges co-operating with an edge rigidly secured to the frame of the device. If a hindrance, for instance a stone, gets into the cutting zone, damages occur on the edges. Damages on the helical edges on the rotor are particularly troublesome since the rotor often must be discarded entirely or sent to a work shop for a thorough repair comprising welding-on of new edges. Due to these problems cylinder mowers are not used to such a large degree which would be motivated solely by the mowing result. Instead numerous other mowing devices are used, which give a less excellent mowing result. SUMMARY OF THE INVENTION The object of the invention is to develop the mowing device initially defined so that it may combine excellent mowing result with a good resistance against damages. This object is according to the invention obtained in that the cutting members are pivotably connected to the rotor about pivot axes generally parallel to the axis of rotation of the rotor to impart the cutting members ability to pivot away in a direction opposite to the direction of rotation of the rotor when meeting hindering objects. Furthermore, the rotor is according to a preferred embodiment arranged moveable, against the action of a resilient force, transversely to its axis of rotation in a direction away from the edge member. Moreover, it is suitable that the edge member is moveable, against the action of a resilient force, in a direction generally opposite to the direction of displacement of the mowing device. Further preferable developments of the invention are defined in the dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS With reference to the appended drawings a more specific description of an embodiment example of the invention will follow hereinafter. In the drawings: Fig 1 is a top view of a vehicle provided with three mowing devices according to the invention; Fig 2 is partially cut sideview of the mowing device according to the invention; Fig 3 is a partially cut view illustrating the rotor of the mowing device, the journalling thereof and the cutting members; Fig 4 is an enlarged and cut detail view of the rotor axle end to the right in Fig 3; Fig 5 is a section along the line V-V in Fig 4; Fig 6 is an end view illustrating a carrying disc contained in the rotor, a cutting member and the stationary edge member; Fig 7 is an enlarged view illustrating the attachment of a cutting member to the rotor; Fig 8 is an end view of the mowing device from that side of the device which is opposite to the one illustrated in Fig 2; Fig 9 is a perspective view illustrating the principle for attachment of the edge member to the frame; Fig 10 is a view illustrating the edge member in a secured position; and Fig 11 is a view of the edge member from above and illustrating its co-operation with a cutting member. DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT In Fig 1 a vehicle is illustrated which carries three mowing devices designed according to the invention, namely two forward la and one rear lb. The normal direction of displacement of the vehicle is designated with the arrow A. The two forward mowing devices la are elevatable by means of carrying devices 2 comprising carrying arms and also displaceable sidewardly relative to the direction of displacement of the vehicle. The mowing width may thereby be varied. The rear mowing device l ~ - ~ is not moveable sidewardly but elevatable by means of an am device 3. The vehicle may be of any arbitrary kind with stee¬ ring at the middle or waist. As appears from Fig 2, each of the mowing devices comprises a frame 4 and a rotor 5 rotatably journalled in the frame about a generally horizontal axis and provided with cutting members 6 adapted to co-operate shearingly with an edge member 7 arranged at the frame on rotation of the rotor. Each cutting member 6 is pivotably connected to the rotor 5 about pivot axes 8 generally parallel to the axis of rotation of the rotor to impart the cutting member ability to pivot away in a direction S opposite to the direction of rotation of the rotor (arrow R) when meeting hindering objects. The rotor 5 including the cutting members 6 are against the action of a resilient force arranged moveable transversely to its axis of rotation in the direction away from the edge member 7, more specifically in a direction upwardly. The rotor 5 is supported relative to frame 4 by pivot arms 9 and 10 respec¬ tively. These are at one of their ends (at 11) hingedly con¬ nected to brackets on frame 4 and carry with their other ends the opposite ends of the rotor. The hinge connections 11 of arms 9, 10 are located, viewed in the normal direction A of displacement of the mowing device, behind the axis of the rotor 5 and at generally the same level as the same. At least one of the pivot arms, say the one denoted 9, may possibly have a variable length, which may be realized in arbitrary manner, e.g. by the pivot arm comprising two parts being adjustable relative to each other by means of a thread device. A locating arrangement is provided which adjustably delimits the movement of the rotor 5 towards the edge member 7 and allows the rotor to move away therefrom against spring force. The locating arrangement comprises in the embodiment two rods 13 coordinated with springs 12, one of said rods being at one of its ends hingedly connected to a bracket 14 on the pivot am 9 whereas the other rod is hingedly connected to the pivot arm 10. Each spring 12 has the character of screw spring extending about the respective rod 13 and abutting with one of its ends against an abutment on the rod and with the other end thereof against the frame. Since the springs normally are in compres¬ sion, they tend to displace the rotor downwardly towards the edge member 7 but this tendency is delimited in an end position by a stop member 14 arranged on the rod 13 and here having the character of nut co-operating with a thread on the rod. The nut 14 is arranged to support against a portion of the frame 4 of the device to thereby delimit the movement downwardly of the rotor, the rotor position being adjustable by screwing the nut on the respective rod 13. As appears from Figs 2 and 8 the frame 8 may comprise generally hexagonal gable pieces, which are obtained by beam sections and interconnected by means of transverse beam pieces (not illu¬ strated on the drawings) and cover plates 16. A connection device denoted 17 connects the frame 4 to the respective carrying device 2, 3. The altitude of frame 4 relative to the ground is determined by support members, e.g. support wheels 18, which may be arranged on pivot arms 19, the pivot position of which and thereby the altitude of the wheels 18 may be modified by means of adjustment members 20 variable in length and acting between the respective pivot arms 19 and frame 4. As appears from Fig 6 there are means 21 to restrict the pivoting movement of the cutting members 6 relative to the rotor in the direction R of rotation thereof. These means are formed by portions 21 of the cutting members, said portions supporting against the rotor on support surfaces 22 thereon. More specifically, these restriction means may be so designed that they prevent each individual cutting member 6 from reach¬ ing such a radially protruding position which the cutting member in question would assume only with regard to the centri¬ fugal force. The restriction means 21 act accordingly to stop the cutting members before they reach such a position caused solely by the centrifugal force. However, the restriction portions 21 do not prevent the cutting members to pivot away in the direction S opposite to the direction of rotation of the rotor. The restriction portions 21 will improve the operational conditions concerning co-operation between cutting members 6 and edge member 7, which is generally stationary during opera¬ tion. On normal rotation of the rotor for grass cutting pur¬ poses, the cutting member 6 will, by means of restriction portions 21, be held in normal working positions which are to be designated as stable. Thus, the centrifugal force on rota¬ tion of the rotor will tend to maintain the cutting members 6 in their positions defined by the restriction portions 21 so that the conditions for co-operation between each individual cutting member 6 and the edge member 7 will be in all essen¬ tials constant. It is only when a hindering object would get into the cutting zone between cutting member 6 and edge member 7 that the cutting member will turn away in the direction of arrow S. Such turning away may also occur if the device would be moved into such thick grass or such dense vegetation that the resistance exerted on the cutting members is larger than the force maintaining the cutting members in their positions defined by the restriction portions 21 on rotation of the rotor. As appears particularly clearly from Fig 6, the restriction portions 21 are arranged to restrict the pivoting movement of the cutting members 6 in the direction R of rotation of the rotor 5 to such a position that the entire edge 23 or at least an essential portion thereof for each cutting member 6 is present behind a plane P which is parallel to the rotor axis 5A and extends through the rotor axis 5A and through the pivoting axis 6A of the cutting member. This means in other words that the edge 23 of cutting member 6 will be located mostly spaced from the axis of rotation 5A of the rotor when the restriction portion 21 of the cutting member stops the cutting member in its end position. If the cutting member 6 would turn away in the direction of arrow S relative to the rotor, edge 23 will accordingly be located at a distance to the axis 5A of rotation of the rotor which successively decreases during the pivoting movement. On such pivoting away of cutting member 6 in the direction of arrow S, the edge 23 of the cutting member will accordingly pass by the edge 24 of the edge member 7 at a distance which becomes larger depending upon the pivoting movement. In other words, the rotor 5 should be adjusted relative to the edge member 7 so that the edges 23 of the cutting members move very closely adjacent to the edge 24 of the edge member when the cutting members are in their normal, stable working positions defined by abutment of the restriction portions 21 against the rotor. The stable working positions discussed hereinabove for the cutting members 6 are, expressed in other words, obtained in that the center of gravity G for each individual cutting member in said stable, normal working position is located, as viewed in the direction R of rotation of the rotor 5, behind the plane P extending through the axis 5A of rotation of the rotor and the pivoting axis 6A of the cutting member 6 in question. Accordingly, this location of the center of gravity generates such a torque about the pivoting axis 6A which is balanced by the abutment of the restriction portion 21 against the rotor. As appears from Figs 2 and 3, a plurality of cutting members 6 are distributed along the circumference of the rotor and along the longitudinal direction of the rotor. It is preferable that several sets of cutting members located circularly about the rotor are arranged displaced tangentially and axially relative to the rotor. As is most specifically apparent from Figs 6 and 11, the cutting members have edges 23 inclined relative to the axis of rotation of the rotor and accordingly also inclined in relation to the edge 24 of the edge member 7 active for cutting pur¬ poses, said edge 24 extending parallel to the axis of rotation of the rotor. This means that the edges 23 of the cutting members will move past the edge 24 whereas the shearing loca¬ tion is successively displaced along the edges 23, 24 as is clearly apparent from Fig 11. The edges 23 of the cutting members 6 are so arranged that they are located on the mantle of a cylinder, the center axis of which coincides with the axis of rotation of the rotor. The cutting members 6 are generally U-shaped with their bran¬ ches 25, 26 connected at their extreme ends to the rotor 5 and their bases 27 comprising the edges 23. Although this is not necessary, the cutting members may be formed by bent plate pieces or otherwise given the shape aimed at. The cutting members 6 are secured to the rotor in a way which is more closely illustrated in Figs 3 and 7. More specifically, the rotor comprises a shaft, which here has the shape of a tube 28. On the shaft 28 a plurality of ring and disc shaped holders 29 are secured and these are provided with an interior conical hole 30. Between the shaft 28 and this conical hole wall there are arranged sleeves 31 having interior cylindrical holes and an external conical surface 32 fitting to the conical surface 30. Furthermore, each ring 31 has a portion 33 having an exterior surface provided with a thread meshing with an inter¬ nal thread in a locking nut 34. On mounting, the ring 31 is arranged on the shaft 28 in the intended position and then the holder 29 is moved on to the ring 31, whereupon the nut 34 is put in place and tightened so that the holder 29 is wedged onto the ring 31 and this in turn by the wedge action is pressed in a stable manner against the shaft 28. To simplify this press securing operation, the ring 31 may be axially divided at least in the area of its conical portion 32. The holder disc 29 comprises a plurality of annularly arranged holes 35 for securing the cutting members 6. These holes recei¬ ve securing members 36 and in case these are formed by screws, the holes are interiorly threaded for co-operating with an external threading on the screws. The screws 36 or such other securing means which may come in question, comprise a cylind¬ rical portion 37 projecting through holes at the extreme ends of the branches 25, 26 of the cutting member 26, so that the cutting members become pivotable about these portions and are retained by widened heads of the securing members. The holder discs 29 comprise in one piece therewith a shoulder 22, which forms the support surface 22 previously discussed with the aid of Fig 6 and forming an abutment for the restric¬ tion portions 21 of the cutting members 6, said portions 21 having the character of a projection on a branch 26 of a cutting member, said projection being located on that side of the pivot axis 6A which is located opposite to the edge 23. As appears from Figs 2 and 8 only every second hole 35 in the two outermost disc holders 29 on shaft 28 are occupied by securing members 36. The disc holders 29 located therebetween, will however, with all their holes 35 act as attachments for cutting members, every second cutting member being located, as is apparent from Fig 3, with its branch in question on one side of the radially outermost portion of the disc holder 29 whereas every second cutting member is located on the other side. Accordingly, also a support surface 22 on the opposite side of the disc holder 29 is required for co-operation with the restricting projections on the cutting members 6 and this support surface is obtained by the cylindrical external surface of the nut 34. When the rotor is stopped, the cutting members would tend to pivot inwardly towards the rotor along a part of the circum¬ ference of the rotor if cutting members 6 were entirely freely pivotably journalled relative to the holder discs 29. This could, on subsequent starting of rotation, cause disturbing imbalance of the rotor and for this purpose means are provided which exert such resilient holding forces on the cutting members that they upon stop of rotation of the rotor retain the cutting members projecting outwardly from the rotor. In the embodiment these holding means are intended to be realized by means of spring members; it is indicated in Fig 7 that a spring washer 38 is laid onto the axle portion 37 between one branch of the cutting member 6 and the holder disc 29. This washer spring, which may have the character of a Belleville spring washer, actuates the branch of the cutting member in the direction towards the widened head of the securing member 36, so that friction forces will be exerted on the cutting member. These friction forces are dimensioned to be sufficient to maintain the cutting members projecting outwardly from the rotor when it is stopped. It appears from Fig 3 that an axle pin 39 is arranged in one end of the shaft tube 28, said axle pin 39 being rotatably supported in the pivot arm 9. In the other end of the shaft tube 28 there is in an analogous way secured an axle pin 40 (Fig 4). Between the latter and a sleeve 41 secured to the pivot arm 10 a bearing 42 is provided, for instance a spherical ball bearing, which allows a certain amount of inclination of the shaft tube 28 relative to the sleeve 41. A sealing diagrammatically indicated at 43 seals between sleeve 41 and shaft tube 28. Exteriorly of the pivot arm 10 (see also Fig 8) there is attached a motor 44 for rotating the shaft tube 28. This motor is preferably a hydraulic motor and comprises a flange 45, by means of which the motor is attached, for instance bolted, to the pivot arm 10, which comprises a hole, through which a drive shaft 46 protrudes. The axle pin 40 is provided with an internal axial cavity 47, into which the drive shaft 46 protrudes. The latter engages drivingly with the axle pin 40 and more specifically in such a way that the axle pin 40 and thereby the shaft tube 28 are allowed to become inclined to a certain degree relative to the drive shaft 46. More specifi¬ cally, the drive shaft 46 has a conical portion, on which a drive member 48 fits with a likewise conical, internal portion. The extreme end of the drive shaft 46 is threaded and co¬ operates with a nut 49, by means of which the drive member 48 is pressed onto the cone of the shaft 46. Moreover, the drive member 48 and drive shaft 46 are mutually secured against relative rotation by means of an axially orientated wedge 50. As appears from Fig 5 the internal cavity of the axle pin 40 has such an unround cross section fitting to the circumference of the drive member 48 so that driving connection is at hand therebetween. The cavity 47 and the drive member 48 are in the embodiment provided with fitting hexagonal or otherwise poly¬ gonal surfaces. It appears from Fig 4 that the polygonal periphery of the drive member 48 is somewhat arched in axial direction so that the discussed mutual inclination is allowed. In the embodiment, the pivot arm 10 cannot be changed as far as length is concerned. Thus, by varying the length of the pivot arm 9, an accurate parallelism can be established between the axis of rotation of the rotor and the longitudinal direction of the edge 24 of the edge member 7 and the necessary mutual inclination caused thereby in view of the fact that the drive shaft 46 of the motor 44 has a fixed position relative to the pivot arm 10 is permitted by the coupling 40/48. Independently of the pivot arm 9 having a variable length or not, the same should be connected to the rotor 5 and more specifically its axle pin 39 by a bearing, e.g. a spherical ball or roller bearing allowing the rotor 5 to assume other positions than entirely horizontal, i.e. to be inclined rela¬ tive to arm 9. It is, namely, preferred that the rotor is capable of swinging at least somewhat during operation of the mowing device about a generally horizontal middle position by the arms 9, 10 being somewhat mutually inclined. Also such freedom for movement is allowed by the described coupling 40/48. The edge member 7 (Figs 9 and 10) are against the action of resilient force moveable in a direction B generally opposite to the normal direction A of displacement of the mowing device. The edge member 7 comprises in the embodiment a carrier 51 for a turn over cutter 52 comprising two edges 24. The cutter 52 is secured to the carrier 51 by means of screws 53. The carrier 51 comprises an angle piece 54 and a plate 55 secured thereto, e.g. by welding, and designed so as to support, by means of a forward longitudinal edge, the forward portion of the cutter 52 which has the presently active edge 24. At the ends of the carrier 51 gable plates or the like 56 are secured, to which in their turn are secured engagement members 57, e.g. by welding or screwing. These engagement members or portions 57 are arranged at the opposite ends of the carrier and are engageable with holders 58 arranged at the gable sections of the frame, said holders being elastically resilient to allow releasing of engagement members 57 and thereby the entire edge member 7 fron the holders 58 when a sufficiently large force is exerted on the edge member 7. More specifically, each holder 58 comprises a plate like holder member 59 rigidly secured to the frame and having a forward, downwardly projecting tongue 60 restricting the movement forwardly of the engagement member 57 and a second holder member 61 resiliently arranged at the frame. The latter may for instance consist of a bandlike piece of resilient material, e.g. steel, which forwardly by means of e.g. bolting is clamped in a bracket 62 relative to the frame. The engagement member 57 and the resilient holder member 61 comprise mutually engaging formations 63, 64, e.g. a recess ir. the engagement member 57 and a projection on the holder member 61. When the edge member 7 is mounted with its engagement members 57 in the respective holder 58 the projection 64 of the holders are received in the recesses 63 as appears from Fig 10. Such a mutual engagement is relatively easy to obtain due tc the fact that the engagement member 57 comprises a ramp surface 65 which relatively easily passes over the projection 64. A considerably larger force must be exerted to get the engagement members 57 to pass over the projections 64 in the opposite direction and when such a force occurs, e.g. due■ to the pro¬ jection 7 hitting against an object, e.g. a tree stump, the resilient holder members 61 are pressed downwardly so that rhe engagement members 57 may move rearwardly out of engagement. Cut grass will be thrown obliquely upwardly/rearwardly to the area of two mutually engaging rolls 66, 67 (Fig 2). These rolls are designed to disintegrate the cut grass straws and engage accordingly in a cutting manner with each other. It is pre¬ ferred that one of the rolls, e.g. the one denoted 66, com¬ prises a pattern of edges, e.g. a square pattern, on its mantle surface whereas the second roll has a somewhat resilient mantle surface, e.g. by being covered by hard rubber. One of the rolls, e.g. the one denoted 66, is driven in an arbitrary way, e.g. by means of a hydraulic motor whereas the second roll preferably is intended to be driven indirectly by the first. It is preferable that the rolls are actuated towards each other by spring force. In the embodiment this is realized in that the supported end portions of the roll 67 by means of springs 68 are actuated towards the roll 66. The cut grass disintegrated by means of rolls 66 and 67 is suitably allowed to fall down on the ground. Further guide plates or the like may be arranged to guide cut grass coming towards the rolls to the engagement area between the rolls. The invention is not only limited to the embodiment described hereinabove but numerous modifications of the embodiment are possible within the scope of the invention.

Claims: Claims 1. A device for mowing grass or similar, comprising a frame (4) and a rotor (5) rotatably journalled to the frame about a generally horizontal axis and provided with cutting members (6) adapted to co-operate shearingly with an edge member (7) arranged at the frame on rotation of the rotor, c h a r a c ¬ t e r i z e d in that the cutting members (6) are pivotably connected to the rotor about pivot axes (8) generally parallel to the axis of rotation of the rotor to impart the cutting members ability to pivot away in a direction opposite to the direction of rotation of the rotor when meeting hindering objects. 2. A device according to claim 1, c h a r a c t e r i z e d in that the rotor (5) is arranged, against the action of a resi¬ lient force, moveable transversely to its axis of rotation in a direction away from the edge member (7) and upwardly from the ground. 3. A device according to claim 2, c h a r a t c t e r i z e α in that the rotor (5) is supported relative to the frame by pivot arms (9, 10) and that a locating arrangement (12, 13 adjustably delimits the movement of the rotor towards the edge member (7) and allows the rotor to move away from the edge member against the action of a spring force and/or gravity. 4. A device according to any of the claims 1-3, c h a r a c ¬ t e r i z e d in that means (21) are provided to restrict the pivoting movement of the cutting members (6) relative to the rotor in the direction of rotation (R) thereof. 5. A device according to claim 4, c h a r a c t e r i z e d ir. that said means are formed by portions (21) of the cutting members, said portions supporting against the rotor (5) . 6. A device according to any preceding claim, c h a r a c - t e r i z e d in that the cutting members comprise edges (23) inclined relative to the axis of rotation of the rotor. 7. A device according to any preceding claim, c h a r a c ¬ t e r i z e d in that the cutting members (6) are generally U-shaped with their branches connected to the rotor at their extreme ends and the bases comprising cutting edges (23). 8. A device according to any preceding claim, c h a r a c ¬ t e r i z e d in that means (38) are provided for exerting such resilient holding forces on the cutting members (6) that the cutting members are retained projecting outwardly from the rotor when the rotation of the rotor is stopped. 9. A device according to claim 3, c h a r a c t e r i z e d in that the pivot arms are connected to the rotor (5) by means of bearings allowing the rotor to assume varying positions of inclination about the generally horizontal position and the motor (44) arranged on one (10) of the pivot arms comprises a drive axle (46) engaging with an axle (40) of the rotor via a mail/female coupling allowing a certain mutual inclination between the drive axle and the rotor axle. 10. A device according to claim 1 or 2, c h a r a c t e ¬ r i z e d in that the edge member (7) is moveable, against the action of a resilient force, in a direction generally opposite to the normal direction of displacement of the mowing device. 11. A device according to claim 10, c h a r a c t e r i z e d in that the edge member (7) comprises portions (57) engageable with holders (58) arranged on the frame, said holders being resilient to allow releasing of the portions and thereby the edge member from the holders when a sufficiently large force is exerted on the edge member. 12. A device according to any preceding claim, c h a r a c - t e r i z e d in that grass cut by means of the cutting members (6) is intended to arrive in an engagement area between at least two rolls (66, 67) shearingly co-operating with each other.

Inventors: SUNDBERG STIG, SUNDBERG, STIG
Applicants: SUNDBERG STIG, SUNDBERG, STIG
Application year: 1989
Main classification: A01D34
IPC codes: A01D34, A01D43