GB2023392A - Lawn mower - Google Patents

Abstract

Lawn mowers for large scale use and for mounting frontwise on a tractor, comprises chassis 2 and at least two cutter units 10 mounted substantially in crosswise alignment relative to the normal moving direction and a further cutter unit 18 mounted offset so as to bridge the gap between the first two units and thus cut the grass stripe left therebetween. The cutter units are arranged in respective leading and rear rows with the cutter units in one row being fixed in respect of the chassis and the cutter unit in the other row being laterally displaceable in response to turning of the front wheels of the tractor so that complete coverage of the uncut grass stripes will be effected. <IMAGE>

Description

SPECIFICATION A lawn mower for large scale use The present invention relates to lawn mowers of the professional type and for mounting at the front end of a tractor, comprising a chassis and a number of cutter units held by said chassis and arranged in two consecutive rows in such a manner that a cutter unit in one row reigsters with the free space between two cutter units in the other row. While in agricultural cutting machines it is possible to use one continuous cutter unit covering the entire operational width it is considered necessary for large scale lawn mowers to make use of a number of juxtaposed, narrow cutter units which are each able to follow the local irregularities of the ground in order to obtain the desired quality of the grass cutting.Such separate units cannot be tightly juxtaposed in a single row, and for this reason there is placed, in another row, the necessary number of further cutter units registering with the spaces between the units of the first row such that no uncut grass stripes are left behind the mower.

It is normal practice to arrange for the mower to be pulled behind a tractor, whereby the cutter units may be held in a trailer-like manner ensuring that even when driven through horizontal curves the various units will still operate as required for not leaving uncut grass stripes behind the mower.

However, propelling a mower structure by pulling it behind a tractor involves the very important disadvantage that along the tractor wheel tracks the grass is cut immediately upon the wheels having rolled down the grass, i.e. the cutting is not as effective as desirable. For this reason it could be attractive to mount the mower structure at the front end of the tractor, but at this end the problems asto driving through curves are essentially different from what can be solved by way of the said trailer arrangement at the rear of the tractor.The reason is that a front mounted structure will be laterally displaced as a whole when the front wheels of the tractor are turned to curve drive, and immediately by the turning of the wheels the leading row of cutter units will carry out a combined forward and lateral movement causing the uncut gass stripes to be correspondingly oblique to the leading cutter unit row, in a manner not at all corresponding to the motion of an ordinarily trailer arrangement. Correspondingly the rear row of cuttter units, if trailer-like arranged, would have no chance to catch up with the changed moving direction and arrange themselves perpendicular to their own path of movement so as to make these paths coinciding with the uncut grass stripes.In orderto partially overcome the said problem it has been proposed to locate the rear row of cutter units underneath the tractor, between the front and rear wheels thereof, but constructionally this is an inconvenient solution, which will even only partially solve the said problem.

It is the purpose of the invention to provide a mower which is well suited to be mounted at the front end of a tractor without any of the cutter units having to be of particularly increased width in order to effect cutting of the said grass stripes even when the mower is driven through horizontal curves.

According to the invention there is provided a mower which is characterized by the features stated in the characterizing clause of claim 1. The invention is based on the cognition that the said oblique grass stripe is left between the neighbouring cutter units in one of said rows when the mower structure is subjected to said combined forward and lateral displacement will by necessity show an orthogonal width which is smaller than the stripe width by normal forward driving, and that, therefore, in order to effectively cover such a reduced stripe width by a following or even a preceding cutter unit it will not be necessary to arrange for this cutter unit to be able to immediately adopt a position and an orientation corresponding to orthogonal coverage of the stripe.

A lateral displacement will be sufficient when the concerned cutter unit is of a type which is able to work efficiently when during and after its displacement it is moved forwardly without being oriented orthogonally with respect to its direction of movement. However, lawn mowers of the large scale type are normally provided with cutter units which are motor driven such that they will be fully operative even when moved forward in a non-orthogonal position. Even units driven by ground follower wheels will be usable, though perhaps with modified wheels allowing for lateral displacement of the units.

Correspondingly, the said substantially fixed cutter units will be operative while they are laterally displaced by the turning of the tractor. The relatively displaceable cutter unit or units may be mounted rather closely behind or in front of the row of fixed cutter units such that the necessary relative displacement need not be very large for effective coverage of the said oblique grass stripes, and accordingly the displaceable unit or units will need no large transverse dimension.

The said displacement of the displaceable unit or units may be effected by means of a direct control connection with the steering system of the tractor or by means of a ground follower arrangement capable of detecting a change of the driving direction and of causing a corresponding displacement of the displaceable cutter unit or units.

In the following the invention is described in more detail with reference to the drawing, in which Fig. 1 is a perspective view of a tractor and a lawn mower according to the invention, Fig. 2 is a top view thereof, Fig. 3 is a schematic view illustrating straightforward driving, Fig. 4 is a corresponding view illustrating curved driving, Fig. 5 is a plan view of a modified detail, Fig. 6 is a schematic top view of a modified mower according to the invention, and Fig. 7 is a corresponding view illustrating curved The drawings originally filed were informal and the print here reproduced is taken from a later filed formal copy driving.

The mower structure shown in Fig. 1 comprises a chassis 2 which is releasably coupled to the front end of a tractor so as to be generally displaceable in the vertical direction, but rigidly held in the longitudinal direction of the tractor. At the front end of the chassis 2 is mounted, at both sides, a pair of holding brackets 6 pivotally holding between them one end of a stub frame 8 projecting laterally outwardly and at its outer end, at 12, being pivotally connected with a mower unit 10 in such a manner that this unit is allowed to carry out vertical movements, both generally and by pivoting about the longitudinal axis defined by the pivots 12, while it is otherwise rigidly guided or held in its generally transverse position.

The chassis 2 is supported by a pair of ground follower swivel wheels 14, and each of the opposed front units 10 is correspondingly supported by a pair of ground follower wheels 16 of the swivel type, adjusted to the desired cutting height The units shown are of the cylinder cutter type, and they may be operated by any convenient power source (not shown), e.g. by individual, hydraulic motors hose connected with the hydraulic power system of the tractor. The two units 10 leave between them a space a behind which the grass is left uncut However, behind this space is mounted a further cutter unit of a similar type, but designated 18.This unit is connected to the chassis by means of a pair of almost parallel traction levers 20 extending substantially horizontally between rear posts 22 on the unit 18 and respective pivot points 24 on a transverse holder member 26 mounted between the foremost brackets 6. The unit 18 is supported by swivel wheels 28, and it is an important feature that the holders 30 of the these wheels are mounted so as to be topwise leaned slightly forwardly to define a correspondingly inclined swivel axis of the wheels 28.

As more clearly shown in Fig. 2, due to its being held by the pivot levers 20 the rear cutter unit 18 will be movable from side to side by an almost parallel displacement However, due to a minor convergation between the levers 20the unit 18 will atthe same time tend to rotate about a point located well ahead of the entire arrangement.

By normal straightforward movement, of course, the rear unit 18 will cut the grass stripe left behind the space a, the unit being broader than this space.

When the front wheels 32 of the tractor are turned for initial curve driving the longitudinal axis of the tractor and therewith the chassis 2 and the front units 10 are swung correspondingly during the forward drive, and to the chassis 2 and the units 10 this will mean a pronounced lateral displacement combined with the forward movement. Hereby the chassis 2 will seek to pull the levers 20 and therewith the unit into the new direction, but because the rod connection 20 is not rigid the unit 18 will not immediately follow the displacement, and the consequence is that the rear unit 18 in a relative manner will be laterally displaced in the opposite direction as shown in Figs. 2 and 4.

By the said displacement of the chassis 2 and the front units 10 the uncut grass stripe from the space a will immediately be left or started as a stripe which is oblique relative to the axis of the tractor and has an orthogonal width b (Fig. 4) which depends of the actual turning radius of the tractor. However, this tripe will be effectively covered by the rear unit 18 due to the said relative displacement thereof, such that during the curve driving the grass cutting will be total even when the rear unit 18 is only slightly broader than the space a.

The said relative displacement of the rear unit 18 should be proportional with the curvature of the cutting path in order to condition a reasonably small width of the unit 18. However, this is achieved auto maticallybywayofthe pulling system used and due to the said inclined swivel axis of the castors or wheels 28; the weight of the unit 18 hereby tends to hold or center the castors in a normal position corresponding to straightforward drive, and this centering force on the castors 28 will be higher the more obliquely the unit 18 is pulled forward. It is possible hereby to adapt the system such that the rear unit 18 will assume a position covering the said grass stripe by any driving direction.

It is advantageous, of course, that the rear unit 18 is guided so as to additionally be rotated slightly towards an orthogonal position relative the uncut grass stripe, because this contributes to a small necessary width of the unit 18.

The operation conditions should be considered not only in connection with straightforward and curved driving, respectively, but also in connection with actual changes between different driving directions. It is essential that the fixed units 10 react immediately to a change of direction by causing the uncut grass stripe to change its relative direction at the same time, while the cutting of the stripe is not effected immediately, but not until the rear unit 18 arrives at the place where the change of direction was initiated. In practicethis meansthatthe rear unit 18 should ideally continue to follow its track according to the former direction, irrespective of the tractor being turned, until it reaches the place where the grass stripe changes its direction.A 100% ideal operation of the rear unit in this respect and under all circumstances will hardly be practically achievable, but fully satisfactory results have been obtained with the illustrated embodiment in which the inclined swivel axis of the castors 28 result in a sluggish displacement reaction when the change of the driving direction goes towards a sharper curvature of the driving path, while invertedlythe said centering action of the castors will condition a relatively fast inward displacement of the unit 18 when the change goes towards a smaller curvature, such that the unit 18, when arriving at the place of initial change of the grass stripe direction, will already be brought into itst new and thereafter correct position, while in the meantime it has cut the grass stripe along the former direction thereof.

The castors 28 futher serve the general purpose of stabilizing the normal position of the rear unit when the mower is driven along a laterally sloping filed.

The said centering action of the castors may be obtained even by way of a suitable spring bias.

In the embodiment shown in Fig. 1 the front units 10 may be swung up, for idel transportation, about the pivot connection between the chassis 2 and the sub frames 8, whereby the chassis will still be supported by the swivel wheels 14. Simple carrier means (not shown) may be used for holding the rear unit 18 off the ground and suspended in the chassis 2. Moreover, in the example shown, the chassis is so connected with the tractor via pivot couplings 3 and inclined connector levers 5 that by increased resistance to the operational movement of the mower system the pushing force will be partially transformed to a downwardly directed force on the nose of the tractor, whereby a firm ground engagement is secured for the front wheels.

The cutter units may be of the so-called rotor type, and they could even be of the type driven by ground follower wheels, since such wheels may be designed to allow the unit to be laterally displaced during the forward drive.

As a certain relation should exist between the turn angle of the tractor and the necessary displacement of the displaceable unit or units it will of course be possible to effect the displacement by means other than described in the foregoing, e.g. by means of a direct control connection to the steering system of the tractor or with the use of a ground following castor made as a detector for changes of the driving direction and as a control unit for controlling a servo mechanism for corresponding displacement of the cutter unit or units.

In Figs. 6 and 7 is shown an embodiment in which the displaceable unit, designated 50, is mounted in front of the fixed units 52 and is held by a parallel guiding rod system 54, of which an arm portion 56 is extended rearwardly and is linked to the steering system of the tractor through a link 58 and a fixed, rearwardly projecting arm 60 on the wheel holder means of one of the tractor front wheels. As apparent from both Fig. 6 and 7 the unit 50 will hereby be laterally displaced in immediate dependency of a turning of the front wheels, whereby the displacement may be adapted so as to correspond to the turning as required for correct operation.Even this system, in which the displaceable cutter unit 50 may alternatively be located behind the fixed units, will at least partially take into account the said problem as to the grass being cut by the two rows of cutters in a non-concurrent manner, as here the units coupled to the steering system will get displaced more directly than the fixed cutter units. In the system according to Figs. 6 and 7 the tractor forms part of the control system of the mower, such that the tractor will then, in such cases, belong to a complete mower according to the invention.

It should be noted that in Figs. lAthe front wheels of the tractor may be turned during stillstand, what will be difficult with the system according to Figs. 6 and 7. However, it will be possible to arrange for a spring connection in the control system enabling the wheels to be turned and a subsequent displacement of the unit 50 as soon as actual driving is started.

Also in Figs. 6 and 7 it may be advantageous to make the displaceable unit or row of units, if there are more of them, be guided such that they rotate slightly by the displacement. This is easily obtainable by a control rod system as in Figs. 14. In Fig. 5 is shown an alternative arrangement of this system, in which the displaceable unit is held by a single lever 62 which by means of a lever system 65 is guided to carry out a combined swinging and lateral displacement.

Claims (7)

1. A lawn mower for large scale use and for mounting at the front end of a tractor, comprising a chassis and a number of cutter units held by said chassis and arranged in two consecutive rows in such a manner that a cutter unit in one row registers with the free space between the two cutter units in the other row, characterized in that the cutter units of one row are mounted in substantially fixed working positions on the chassis, while the cutter unit or units in the other row are connected with the chassis so as to be generally laterally displaceable relative thereof and connected with control means responding to a change of the driving direction by cooperation with the ground or with the steering controls of the tractor so as to be operative to cause each displaceable unit to be displaced to still register with the said free space between the two cutter units in said one row, as seen in the changed, actual direction of the movement thereof.

2. A lawn mower according to claim 1, in which the displaceable unit or units are placed behind the substantially stationary cutter units in said one row, and the control means for displacing the unit or units comprise ground follower wheels of the swivel type which, by means of a spring bias or downwardly and rearwardly inclined swivel axis, tend to seek towards a normal position corresponding to straightforward drive.

3. A lawn mower according to claim 1 or 2, in which the displaceable unit or units are connected with the chassis by means of a pivot rod system operable to guide each unit substantially parallely along a transverse arched path.

4. A lawn mower according to claim 1,2 or 3, in which the displaceable unit or uhits are guided in such a manner that in addition to their lateral displacement they are rotated slightly up against the actual driving direction.

5. A lawn mower according to claim 1, in which the displaceable unit or units are connected with control means associated with the chassis and having a connector portion coupled or adapted to be coupled together with a steering control portion of the steering system of the tractor in such a manner that the said displacement is effected compulsorily by the turning of the steering wheels of the tractor.

6. A lawn mower according to claim 5 and comprising the tractor as provided with said steering control portion.

7. A lawn mower according to claim 5 or 6, in which the displaceable cutter unit or units are arranged in front of the substantially stationary cutter units in said one row.