WO1991004652A1

WO1991004652A1 - Ground roll and scraper for grass cutting unit

Info

Publication number: WO1991004652A1
Application number: PCT/GB1990/001533
Authority: WO
Inventors: John Mills
Original assignee: Ransomes Sims & Jefferies Limited
Priority date: 1989-10-06
Filing date: 1990-10-05
Publication date: 1991-04-18
Also published as: GB8922575D0

Abstract

A scraper (16) for cleaning debris from the ground roll (10) of a grass cutting unit is designed so that a scraper blade (20) is forced into contact with the roll in the presence of debris. The scraper (16), is also designed so that it can be easily separated from the edge of the roller (10) to enable debris to be cleared from the scraper.

Description

GROUND ROLL AND SCRAPER FOR GRASS CUTTING UNIT

This invention relates to grass cutting machines and in particular to scrapers which are provided to remove debris from ground rolls.

It will be understood that the ground roll or rolls of a helically bladed or other grass cutting unit usually serve to determine the height of the grass cutting blades above ground. Thus an accumulation of debris on a ground roll would cause an unwanted progressive increase in the height of cut.

There have been numerous cleaning devices that have been proposed for use with ground rolls in order to remove debris and to maintain a constant roll diameter. Typically, these devices comprise fixed bars which extend along the length of the roll, with a small clearance set between the bar and the roll periphery. Such devices suffer from the disadvantage that cut grass and other debris tends to be caught between the bar and the roll periphery with a progressive increase in the resistance to rotation of the roll, which can result in jamming. Also, the debris can at intervals release itself in untidy clumps spoiling the appearance of the cut grass area.

It is an object of the present invention to provide a ground roll and scraper assembly for a grass cutting unit which overcomes or alleviates the above problems.

Accordingly, the present invention consists in a ground roll and scraper unit for a grass cutting machine, comprising a frame; a ground roll mounted in the frame for rotation about the roll axis; a scraper mounted in the frame for pivotal movement about a pivot axis parallel to the roll axis and comprising a scraper edge, the scraper being pivotable about the pivot axis in a first sense to bring the scraper edge into scraping contact with the periphery of the roll and in a second sense to separate the edge from the roll periphery for clearance of debris, the arrangement being such that reaction on the scraper through scraping contact of said edge with the roll periphery applies a moment about the pivot axis tending to pivot the scraper in said first sense. Advantageously, the scraper further comprises a locating edge generally parallel with the scraper edge and positioned such that with the scraper edge in scraping contact with the roll periphery, the locating edge opposes the roll periphery at the opposite side of the plane containing said pivot axis and roll axis to provide a resistance to movement of the scraper in said second sense.

Preferably, the scraper further comprises adjustment means enabling parallelism to be assured between the scraper edge and the roll periphery.

Suitably, stop means are provided to limit movement of the scraper in said second sense to an end position in which gravity serves to pivot the scraper in said first sense.

A ground roll and scraper assembly according to the present invention can be arranged such that, with a clean ground roll, the scraping edge lays lightly against the roll periphery. As material is picked up on the roll periphery, the scraper is pivoted by the resistance exerted on the scraper edge to bring the scraper edge into tight scraping contact with the roll periphery. The close engagement between the scraping edge and the roll periphery reduces the likelihood of debris collecting under the scraper. If, for example during adverse conditions, there is an accumulation of debris under the scraper, it can be pivoted in the defined second sense to separate the scraping edge from the roll. This can be achieved, for example, by manual reverse rotation of the ground roll or by moving the cutting unit rearwards while still in contact with the ground.

The invention will now be described by way of example with reference to the accompanying drawings in which:-

Figure 1 is a perspective view of a ground roll and scraper assembly according to the present invention.;

Figure 2 is a somewhat diagrammatic section on the assembly of Figure 1 ; and

Figure 3 is a view similar to Figure 2 showing a different operating position. The ground roll 10 is mounted on stub shafts 12 for rotation relative to frame members 1 , only of one of which is seen in Figure 1 . The scraper shown generally at 16 comprises a scraping element 18 of angle section. This provides a scraping blade 20 terminating in scraping edge 22 and an integral location blade 24 terminating in locating edge 26.

At opposite ends of the location blade 24 are rigidly secured mounting studs 28 which, through lock nuts 30, provide for mounting of the scraper element 18 on opposing bearings 32. Each bearing 32 comprises a lug 34 receiving the mounting stub 28, a cam 36 and a stub shaft 38. Each stub shaft 38 is received in the corresponding frame member 14 to provide a pivotal mounting whilst the cams 36 cooperate, in a manner which will be described subsequently, with corresponding fixed pins 40 projecting from the frame members 14.

Referring now to Figure 2, there is shown in full lines what can be regarded as the scraping position of the assembly. It will be understood that the scraping edge 22, when engaging material adhered to the roll as shown at 50, will create a reaction F in a direction substantially tangential to the periphery of the roll 10. The line of action of F has a normal spacing R from the scraper pivot axis and will apply a moment causing anti-clockwise rotation of the scraper about the pivot axis. This, it will be recognised, will force the scraping edge 22 into closer scraping contact with the roll periphery.

Because it is assured that any accumulation of material on the roll periphery will lead to the scraping edge being driven into closer contact, the scraper can be designed so that, with a clean roll, there is relatively light contact with the roll and therefore minimal friction.

The location blade 24 serves to maintain the scraper in a position from which it can be driven, as described above, into close scraping contact with the roll periphery. As shown in Figure 2, the locating edge 26 engages the roll periphery at a relatively small distance T beyond the plane containing the roll axis and the scraper pivot axis. Accordingly, any tendency of the scraper to pivot in a clockwise direction will be resisted by the interference of the locating edge 26 with the roll periphery. The scraper element is therefore maintained in the correct operating position despite possible shock forces on the scraper element and the effects of gravity on inclined grass surfaces or at extreme limits of roil position. Large swinging movements of the scraper during transport are also avoided.

If it is desired to separate the scraper from the roll periphery, usually to clear debris which may accumulate under adverse weather conditions, the ground roll is rotated anti-clockwise as shown in Figure 3. This can be done manually or by moving the grass cutting unit rearwards. Friction acting on the scraper element will then cause it to be pivoted in a direction taking the scraper edge away from the roll periphery, as again shown in Figure 3. To limit this pivotal movement, the cam 36 is provided with a stop surface 60 which engages pin 40 on the frame member 14. It is arranged that, at this stop position, the center of gravity of the scraper has not passed over-center so that gravity will cause the scraper to return to the position shown in dotted outline in Figure 2. Reaction on the locating edge 26 will then cause the scraper to "toggle" into the operating position shown in full outline.

If through wear, maladjustment or an unusual ground contour, the scraping edge lays away from the roll periphery, any debris adhering to the roll and passing between the scraping edge 22 and the roll, will contact edge 24 thus causing the scraper to "toggle" on and bring scraping edge 22 into close contact with the roll.

The toggling feature by which the locating blade 24 enables the scraper to be toggled into and out of an operating position is regarded as advantageous. It would be possible without departing from the scope of this invention to use an alternative arrangement of a spring to maintain the scraper in the correct position; this would not, however, enable free movement of the scraper to the clearance position shown in Figure 3 and for this reason the use of a location blade is much preferred. The mounting studs 28 and nuts 30 enable the position of the scraper element to be adjusted relative to the roll periphery. This enables an efficient scraping action to be assured over the full length of the scraping edge 22 and also maintained during wear of the roll periphery or scraping edge.

This invention has been described by way of example only and it should be understood that a variety of modifications are possible without departing from the scope of the invention. The shape of the scraper element and the method by which it is pivoted about an axis parallel to the roll axis can be varied, although it must be ensured that the reaction of the scraper through scraping contact with the roll periphery tends to pivot the scraper in a sense bringing the scraper edge into contact with the roll periphery. With the preferred use of a locating edge, it must be assured that this makes contact with the roll periphery on the opposite side of the plane containing the pivot axis of the scraper and the axis of the ground roll. The described angle construction of the scraper element afords in a simple manner the required configuration of scraping and locating edges and also has the merit of resisting the build-up of debris during normal operation whilst freely releasing any accumulation of debris on movement of the scraper to the clearance position. Other scraper configurations will be possible, however.

Claims

CLA1MS:

1. A ground roll and scraper unit for a grass cutting machine, comprising a frame; a ground roll mounted in the frame for rotation about the roll axis; a scraper mounted in the frame for pivotal movement about a pivot axis parallel to the roll axis and comprising a scraper edge, the scraper being pivotable about the pivot axis in a first sense to bring the scraper edge into scraping contact with the periphery of the roll and in a second sense to separate the edge from the roll periphery for clearance of debris, the arrangement being such that reaction on the scraper through scraping contact of said edge with the roll periphery applies a moment about the pivot axis tending to pivot the scraper in said first sense.

2. A unit according to Claim 1 , wherein the tangental plane at the line of contact of the scraper edge with the roll periphery extends between the roll axis and said pivot axis.

3. A unit according to Claim 1 or Claim 2, wherein the scraper further comprises a locating edge generally parallel with the scraper edge and positioned such that with the scraper edge in scraping contact with the roll periphery, the locating edge opposes the roll periphery at the opposite side of the plane containing said pivot axis and roll axis to provide a resistance to movement of the scraper in said second sense.

4. A unit according to Claim 3, wherein the locating edge is positioned so as on initial movement of the scraper in said second sense to contact the roll periphery at a spacing from said plane small compared with the roll diameter so as to permit deliberate movement of the scraper in said second sense for clearing.

5. A unit according to any one of the preceding claims, further comprising adjustment means enabling parallelism to be assured between the scraper edge and the roll periphery.

6. A unit according to any one of the preceding claims, further comprising stop means provided to limit movement of the scraper in said second sense to an end position in which gravity serves to pivot the scraper in said first sense.

7. A ground roll and scraper unit for a grass cutting machine, comprising a frame; a ground roll mounted in the frame for rotation about a roll axis and a scraper mounted in the frame for pivotal movement about a pivot axis parallel to the roll axis, the scraper comprising a scraper edge and a locating edge parallel to the scraper edge, the scraper edge and locating edge being positioned so as to contact the roll periphery on opposite sides of a plane containing the roll axis and the pivot axis with a tangental plane at the contact of the scraper edge with the roll periphery passing between the roll axis and the pivot axis.

8. A unit according to Claim 7, wherein the contact between the locating edge and the roll periphery is sufficiently close to said plane, having regard to the roll diameter, to permit pivotal movement of the scraper in a direction separating the scraper edge from the roll periphery once a threshold torque has been exceeded.

9. A unit acording to Claim 3 or Claim 7, wherein the scraper is of L-shape section.

10. A grass cutting machine comprising a grass cutting element and a ground roll and scraper unit in accordance with any one of the preceding claims.