MOWING DEVICE WITH ADJUSTABLE SPACING

Abstract: A mower comprising a frame (4) connectable to a propulsion unit for moving the mower is described. The mower includes at least one pair of rotary cutters (20) mounted to the frame and gear means for transmitting power from a drive unit to the rotary cutters. Means is provided for adjusting the relative spacing of the pair of cutters from a direction generally transverse to that in which the mower moves thereby to adjust the width of the cut produced by the pair of rotary cutters.

Description: MOWING DEVICE WITH ADJUSTABLE SPACING This invention relates to mowers and in particular but not exclusively to mowers for use in conjunction with a tractor. Known mowers generally comprise a frame securable to a tractor and carrying one or more rotary cutters. The cutters are powered from the tractor via a central gear box and a separate belt drive for each cutter. They are positioned that such that their cutting envelopes are closely adjacent in order that a strip of un own grass is not produced therebetween. Known mowers are in themselves capable of performing only a single width of cut. With certain known mowers the width can be increased by attachment of a separate cutter to the frame which swings out therefrom. Again this cutter is powered via a belt drive from the central gear box. This however increases the length of the mower as well of course as its expense. The need for a spare part ie the separate cutter and to attach and detach this and its drive as the width requirement changes is obviously undesirable. Furthermore, only increases in cutting width from the basic fixed width are possible. A further disadvantage of known mowers is that, as the cutters are all belt driven from a central gear box, they all rotate in the same direction which does not produce the best cutting action. It is an object of the invention to provide a mower which accommodates readily and easily different desired cutting widths. A mower, in accordance with the invention, comprises a frame connectable to a propulsion unit for moving the mower, at least one pair of rotary cutters mounted to the frame, gear means for transmitting power from a drive unit to the rotary cutters and means for adjusting the relative spacing of the pair of cutters in a direction generally transverse to that in which the mower moves thereby to adjust the width of the cut produced by the pair of rotary cutters. The advantage of this is that, by adjusting the relative position of the pair of cutters the width of cut produced by the mower can be changed, but this is achieved without lengthening of the mower, in contrast to known mowers. The cutters may be arrayed across the frame at one or more locations therealong. If an odd number of cutters is provided at any longitudinal location, then one cutter is suitably fixedly positioned with the others arranged either side thereof. The cutters in the or each pair of adjustable cutters are movable from a first position at a first relative spacing to a second position at a second relative spacing, greater than the first, and vice versa. The change in the width of cut is therefore double the distance moved by each cutter so that the possible variations in width of cut can be relatively large. Each cutter includes at least one blade. The cutting envelopes of the blades of adjacent pairs of cutters suitably overlap in the first position and are closely adjacent, touching or overlapping in the second position. The result of this is that in both positions no strip of unmown grass is produced between the cutters in the pair. Suitably in order to allow for overlap of the cutting envelopes, the blades and/or the carriers whereby they are mounted to the frame are cranked. Further the blades of one cutter of the or each pair are offset 90" from the blades of the second cutter. The frame may include a first fixed portion and a second movable portion to which the movable cutters are mounted, the adjustment means being operable to move the second portion relative to the first portion and thereby adjust the position of the cutters. Each frame portion may include a plurality of struts and suitably, for structural integrity and rigidity, some of the struts of the first portion are telescopically receivable in corresponding struts of the second portion and vice versa. In one particularly preferred embodiment the frame comprises a fixed central portion with four struts and two movable side portions each with four struts, the middle struts of the side portions telescopically receiving the middle struts of the central portion and the outer struts of the central portion telescopically receiving the outer struts of the side portions. The frame may further include a cover supported by the struts. The portion of the cover which is fixed to the telescopic sections of the struts suitably comprises, for constructional rigidity, triangulated plates, those plates which are caused to move on telescopic movement of the struts including flaps to enclose the resultant gaps. The gear means very preferably comprises a gear box for each cutter. Adjacent cutters can therefore be arranged to be counter-rotating with the result that they will pull up the grass to cut it which is a preferred and effective cutting action. Further the timing of the cutters can be set so that the blades thereof will intermesh thereby allowing the cutting envelopes to overlap. The gear means may further comprise a chain box connected to an output shaft of the drive unit, the chain box having an input shaft connected to each gear box. The gear boxes are preferably mounted on the second movable portion of the frame and to accommodate this the input shafts are telescopic and are secured to the gear boxes by universal joints. The extent of movement of the gear boxes must be set so that the joints will not be damaged and, for standard Hooks joints, it has been determined that the maximum arc through which each input shaft can move is about 26°. The adjustment means very suitably comprises a hydraulic cylinder for each movable cutter. When the mower is used with a tractor as the propulsion unit the hydraulic system of the tractor serves as a hydraulic supply for the hydraulic cylinders. Feed pipes to and from the tractor are connected to a proportional flow divider to supply twin double acting hydraulic cylinders for the cutters of the or each pair. The invention will now be further described by way of example with reference to the accompanying drawings in which: Figure 1 is a perspective view of a mower in accordance with the invention; Figure 2 is an exploded view of the parts of the mower of Figure 1; Figure 3 is a plan view of the frame of the mower of Figure l; Figure 4 is a section taken along the line A-A of the frame of Figure 3; Figure 5 is an end view of the frame of Figure 3; Figure 6 is an enlarged view of the encircled portions B and C of the frame of Figure 3; Figure 7 is a transverse section through the chain drive box of the mower of Figure 1, and, Figure 8 is a section taken along the line D-D of Figure 7. The mower 2 shown in Figures 1 and 2 comprises a frame 4 formed from a plurality of transverse struts 6 and cross-pieces 8. At one end of the frame 4 a tractor linkage mounting bracket 10 is secured to the transverse strut 6 via mounting plates 12. Further mounting plates 14 allow connection of a chain drive box 16. Each strut 6 consists of a central section 6a and a pair of outer sections 6b. The central sections 6a are fixed in position and the outer sections 6b are movable relative thereto. This is achieved by arranging the outer sections 6b at either end of the frame 4 to be telescopically receivable within the inner sections 6a whilst the outer sections 6b in the middle of the frame 4 telescopically receive the ends of the inner sections 6a. This alternation produces structural integrity and rigidity and further facilitates mounting of the components as will be appreciated from the further description below. The struts 6 preferably have a box section. As noted above the tractor linkage mounting bracket 10 and chain drive box 16 are located on a strut 6 at one end of the frame 4. They are therefore carried by the central section 6a of that strut 6. Two drive gear boxes 18 and two rotary cutters 20 are carried respectively on plates 22 secured above and below the middle struts 6 of the frame 4, that is, because of the reversed telescopic arrangement of the middle struts 6 on the outer strut sections 6b thereof. The gear boxes 18 are secured by bolts through holes 23. Movement of the outer strut sections 6b of these middle struts 6 will therefore cause movement of the drive gear boxes 18 and the cutters 20, the plates 22 being split to accommodate this. The cross-pieces 8 include two pairs of spaced plates 24 arranged respectively between each end strut 6 and the adjacent middle strut 6. These plates 24 are fixed in position. In addition side panels 26 are connected to the ends of the struts 6, specifically to the outer sections 6b of the struts 6 so that they will move with these outer sections 6b. A pair of fixed plates 28 are secured across the areas defined by the cross-plates 24 and struts 6. The area between the cross-plates 24, the side panels 26 and the plates 22 is covered by triangulated plates 30 and 32. The inner ones 32 of these plates, which are fixed by welding to the central sections 6a of the struts 6 at either end of the frame 4, are fixed in position. The outer triangular plates 30, which are welded to the outer section 6b of the middle struts 6, move as these outer struts 6b are moved. The plates 30 carry flaps to cover the gap created by such movement. The triangulated form of the plates 30 and 32 produces constructional rigidity. Movement of the outer strut sections 6b relative the inner strut sections 6a and thereby of the gear boxes 18, cutters 20 and side panels 26 is achieved by twin double acting hydraulic cylinders 34 mounted via brackets 36 and 38. The brackets 38 which are connected to the pistons of the twin double acting hydraulic cylinders 34 are secured to the split movable plate 22. If, as is common, the mower 2 is used with the tractor, the hydraulic fluid supply of the tractor may be used for the hydraulic cylinders 34. Hydraulic feedpipes 40 to and from the tractor extend to a proportional flow divider 42 and thence to the twin double acting hydraulic cylinders 34. Flow of fluid from or to the tractor will cause extension or retraction of the hydraulic cylinders 34, the minimum and maximum movement being indicated by the double headed arrow of Figure 1. The cutters 20 each comprise a pair of oppositely extending blades 44 secured to a carrier 46 which in turn is secured to the frame 4. The blades 44 of the pair of cutters 20 are set at 90° to each other allowing a 25% overlap of the blades 44 when the rams 34 are fully retracted. The carriers 46 and blades 44 are both cranked to allow the cutting tips of the blades 44 of each cutter 20 to pass below the centre of the carrier 46 of the other cutter 20. The double crank ensures adequate operational clearance between the two intermeshing blades 44 in the retracted position. The cutters 20 are sized so that the cutting envelopes overlap not only in the retracted position but also preferably in the fully extended position of the hydraulic cylinders 34. This ensures that no strip of unmown grass will be left between the pair of cutters 20. The chain box 16 takes its drive from the output shaft of the tractor employed to draw the mower along although it will be appreciated that a dedicated drive unit may be provided. Chains 48 transmit the drive from the chain box input shaft 49 to two output shafts 50. Each output shaft 50 is connected to one of the gear boxes 18. In order to accommodate movement of the gear boxes 18 as the hydraulic cylinders 34 expand and retract the output shafts 50 are telescopic and they are connected to the gear boxes 18 by universal joints 52. The connection is arranged such that the output shafts 50 are at a minimum length when the gear boxes 18 are midway between the extremities of their possible movement. It has been found that for the universal joints 52 to function correctly the maximum arc through which the shafts 50 travel around their connections to the chain drive box 16 should be about 26°. The drive line is protected at the chain box input shaft 40 by use of a multiplate slip clutch. This protects the drive line without loss of timing in the blades 44 of the cutters 20. In use the operator of the mower 2 simply has to set the hydraulic fluid flow along the lines 40 to an appropriate amount to give the desired positioning of the cutters 20. The arrangement of the parts with the hydraulic cylinders 34 fully retracted is shown in full outline in Figure 1 whilst their positions when the hydraulic cylinders 34 are fully extended is shown in dotted outline. The mower 2 can have any desired dimensions. An exemplary arrangement suitable for example for cutting grass in orchards or vineyards can have a length 54 of say 5 foot, a minimum, fully retracted, width 56 of 4 foot and a maximum, fully extended, width 58 of 6 foot. The parts may be formed of steel having a thickness of say 3 mm with the blade carriers 46 being formed from high tensile E N 8 steel to avoid distortion during operation. The mower 2 shown in the Figures has two cutters 20 both of which are movable. To extend the maximum width of cut, further movable cutters could be provided on the movable portions of the frame 4 and/or a fixed cutter could be provided on the central fixed section thereof. The cutters will be arranged so that the cutting envelopes of adjacent cutters will overlap no matter the position of the movable cutters. Moreover such an array of cutters could be arranged not just at a single location along the frame 4 as illustrated but rather at two or more points therealong. The mower 2 is robust and sturdy due to the structural integrity and rigidity provided by use of the box section male and female struts 6 and the triangulated plates 30 and 32. It permits simple quick and accurate setting of the width of cut. The intermeshing arrangement of the cutters 20 ensures that no uncut strip of grass is left even with the cutters 20 at their maximum separation. This intermeshing is made possible by firstly use of gear boxes to transmit the drive to the cutters 20 and secondly the cranked form of the cutter blades 44 and the cutter carriers 46. The provision of the gear boxes 18 in addition allows the cutters 20 to counter rotate thereby producing the most desirable cutting action. As noted above the mower 2 need not necessarily be used with a tractor although this will obviously be most common. A dedicated propulsion unit and/or hydraulic supply may be provided. In addition a plurality of cutters could be provided arranged in pairs spaced from each other in the direction of travel of the mower 2. Alternative gear arrangements for transmitting drive to the cutters 20 could be provided but that illustrated has been found to be particularly suitable in terms of relative simplicity, good drive transmission and accuracy of cutter timing.

Claims: CLAIMS 1. A mower comprising a frame connectable to a propulsion unit for moving the mower, at least one pair of rotary cutters mounted to the frame, gear means for transmitting power from a drive unit to the rotary cutters and means for adjusting the relative spacing of the pair of cutters in a direction generally transverse to that in which the mower moves thereby to adjust the width of the cut produced by the pair of rotary cutters. 2. A mower as claimed in Claim 1, wherein the adjustment means are operable to move the or each pair of cutters between a first position at a first relative spacing and a second position at a second relative spacing greater than the first and vice versa. 3. A mower as claimed in Claim 2, wherein the cutters include at least one blade, the cutting envelopes of the blades of adjacent cutters overlapping when the movable cutters are in the first position and being closely adjacent, touching or overlapping when the moveable cutters are in the second position. 4. A mower as claimed in Claim 3, wherein the blades and/or the carriers whereby they are mounted to the frame are cranked. 5. A mower as claimed in either Claim 3 or Claim 4, wherein the blade(s) of each cutter are offset 90° from the blade(s) of the or each adjacent cutter. 6. A mower as claimed in any preceding Claim, wherein the frame includes a first fixed portion and a second movable portion to which the cutters are mounted, the adjustment means being operable to move the second portion relative the first portion and thereby adjust the position of the cutters. 7. A mower as claimed in Claim 6, wherein the first and second frame portions include a plurality of struts and wherein at least some of the struts of the first portion and/or the second portion are telescopically receivable in corresponding struts of the respectively the second portion and/or the first portion. 8. A mower as claimed in Claim 7, wherein the frame includes a cover supported by the struts at least part of which comprises triangulated plates. 9. A mower as claimed in any preceding Claim, wherein the gear means comprises a gear box for each cutter. 10. A mower as claimed in Claim 9 when dependent on any one of Claims 6 to 8, wherein the gear boxes are mounted on the second movable portion of the frame. 11. A mower as claimed in either Claim 9 or Claim 10, wherein the gear means comprises a chain box connected to the output shaft of the propulsion unit, the chain box having an input shaft connected to each gear box. 12. A mower as claimed in Claim 11 when dependent on Claim 10, wherein the input shafts are telescopic and are secured to the gear boxes by universal joints. 13. A mower as claimed in any preceding Claim, wherein the adjustment means comprises a hydraulic ram for each cutter whose position can be adjusted. 14. A mower substantially as hereinbefore described and illustrated in the accompanying drawings.

Inventors: PORT COLIN, PORT, COLIN
Applicants: PORT AGRIC LTD, PORT COLIN, PORT AGRIC LIMITED, PORT, COLIN
Application year: 1995
Main classification: A01D34
IPC codes: A01D34