EP0308053A1

EP0308053A1 - Machine for grinding mowing machine cylinder blades

Info

Publication number: EP0308053A1
Application number: EP88307082A
Authority: EP
Inventors: Ralph Winstanley
Original assignee: MOWING MACHINE MAINTENANCE Ltd
Current assignee: MOWING MACHINE MAINTENANCE Ltd
Priority date: 1987-09-14
Filing date: 1988-08-01
Publication date: 1989-03-22
Also published as: GB8721556D0

Abstract

A machine for grinding mowing machine cylinder blades and having a finger guide (30) mounted beneath the grinding wheel (24) as a support for each blade of the blade cylinder (16) as grinding takes place.

So that each blade is maintained in contact with the finger guide (30) as a traverse movement of the grinding wheel head (18) takes place, rollers (50) are provided for acting downwards on the blade.

Description

The invention relates to a machine for grinding mowing machine cylinder blades.
Machines for grinding mowing machine cylinder blades are known and comprise means for mounting the blade cylinder for rotation about the axis of its mounting shaft; a grinding wheel mounted on a grinding wheel head carried on guides for traverse movements longitudinally of the blade cylinder; and a so-called finger guide which is mounted beneath the grinding wheel as a support for each blade of the blade cylinder in turn as grinding takes place, the arrangement being such that as a traverse movement of the grinding wheel head takes place, the abutment of the finger guide against the particular blade concerned causes the blade cylinder to rotate in timed relation to the traverse movement of the grinding wheel and in the appropriate direction according to the direction of traverse of the grinding wheel head. In this way there is ground a constant amount of back relief along the length of the blade concerned.
Such known grinding machines are frequently unable to "index" the work cylinder around automatically from one blade to another to enable a blade cylinder to be completely relief ground in one operation. In this case it has been necessary for the operative to manually index the work cylinder around to bring each blade in turn into abutment with the finger guide to enable it to be relief ground by the traversing of the grinding wheel head as previously described. However, a grinding machine is known in which provision is made for the blade cylinder to be indexed around from one blade to the next so that when it has been put into operation it can grind all the blades of a blade cylinder in turn without the intervention of the operative.
In all these known machines, but especially dangerous in those capable of automatic operation, i.e., capable of indexing a blade cylinder around from one blade to the next without the constant attendance of an operative, there is one particular drawback, this being that if the edge of a particular blade of a blade cylinder which is being ground is not already reasonably 'cylindrical', that is to say does not closely conform to the cylindrical shape of the blade cylinder, the depth of cut of an initial grinding traverse may locally run out at one or more places along the length of the blade. The result of this is an intermittent abrasive action of the grinding wheel against the blade so that instead of there being a smooth rotation of the blade cylinder in timed relation to the traverse movement of the grinding wheel head there is produced a bouncing of the blade concerned on the finger guide. This inevitably results in poorly ground blades and can also result in damage to the grinding wheel and/or to the blade cylinder.
The invention as claimed is intended to provide a remedy. It solves the problem of how to design a machine for grinding mowing machine cylinder blades in a most convenient manner.
The advantages offered by the invention are, mainly, that it provides a machine in which bouncing of a cylinder blade on the finger guide will not occur. The invention in addition safeguards both the blade cylinders and the grinding machine from damage which might be caused by bouncing of the cylinder blades on the finger guide.
One way of carrying out the invention is described in detail below with reference to drawings which illustrate, by way of example, one specific embodiment, in which:-

Figure 1 is a perspective view of a part of a grinding machine embodying the invention,
Figure 2 is a semi-diagrammatic plan view of a part of the machine,
Figure 3 is a semi-diagrammatic view of a so-called finger guide arrangement forming a part of the machine, and
Figure 4 is a perspective view of a slightly modified form of finger guide arrangement.

Referring now to Figure 1 of the drawings, the grinding machine there illustrated is mounted on a stout base 10 and includes quick release means, generally indicated 12 and 14, by means of which a blade cylinder 16 of a cylinder type mowing machine can be mounted for rotation about the axis of its mounting shaft. The machine also includes a grinding wheel head, generally indicated 18, mounted on precision guides 20 for traverse movements longitudinally of the blade cylinder. For protection of the guide surfaces these are encased by flexible gaiter members 22,22 on each side of the grinding wheel head. A grinding wheel 24, which is mounted for rotation on the grinding wheel head, is driven by an electric motor 26.
Means for traversing the grinding wheel head to and fro on its guides, that is to say longitudinally of the blade cylinder, are not shown but traverse limit stops 28,28 are adjustable along the guides 20 to determine the extent of traverse movement in each direction. Also provided are means for indexing the blade cylinder around from one blade to the next, between successive traverse and return movements of the grinding wheel head, so that when the machine has been put into operation to grind one of the blades of a blade cylinder it will automatically grind the remaining blades without further intervention on the part of the operative. These means do not form part of the present invention and will not be further described save to say that they include a geared down electric motor unit 40 and a clutch device 42 for effecting rotational movements of the blade cylinder and proximity switches 44 and 46 for triggering the rotational movements into being and for halting them after the appropriate movements. As shown, the proximity switch 44 is located near the headstock end of the machine and is caused to close by the close proximity of a triggering finger 48 carried by the grinding wheel head. The proximity switch 46 is adjustably located in position close to the path of movement traced by the left hand end portions of the individual blades of a blade cylinder as the latter rotates. The arrangement is such that after each indexing movement of the blade cylinder, the latter is brought to rest in the position shown in Figure 2, that is to say with the left hand end portion of a blade in close proximity to the switch 46. (The operation of these means is more fully described in co-pending British application for patent No.86.4914 of 1986).
Referring now in particular to Figure 3, a finger guide 30 is adjustably positioned beneath the grinding wheel. As shown, the finger guide is carried by an arm 32 which is clamped in position against the side of the grinding wheel head by means of a wing nut 34. The stud which the wing nut engages extends through a slot 36 in the arm so that the latter is adjustable towards or away from a blade cylinder mounted in the machine. The end of the arm remote from the finger guide is acted on by an adjusting screw 38 (see Figure 1) by means of which the vertical height of the finger guide can be adjusted. The purpose of the finger guide is to act as a support for each blade of the blade cylinder in turn as grinding takes place, the arrangement being such that as a traverse movement of the grinding wheel head takes place the abutment of the finger guide against the particular blade concerned and the abrasive action of the grinding wheel against the blade causes the blade cylinder to rotate in timed relation to the traverse movement of the grinding wheel head and in the appropriate direction according to the direction of traverse of the grinding wheel head.
Means are provided for acting downwards on each blade of the blade cylinder in turn as said blade rests on the finger guide. As shown, these means are constituted by a pair of spring loaded rollers 50 located on the opposite sides of the grinding wheel 24 and arranged to engage and ride along the top surface of each blade of the blade cylinder in turn as its lower surface bears against the finger guide. The rollers 50 are carried at the ends of respective pressure members or arms 52, said pressure members or arms being acted on by respective tension springs 54 so that each can act independently of the other.
The purpose of the spring loaded means just referred to is to ensure that each blade in turn is maintained in contact with the finger guide throughout the grinding operation on said blade. In this way, if a blade is not already reasonably cylindrical, that is to say does not closely conform to the cylindrical shape of the blade cylinder (which may well be the case if the blade cylinder concerned has never before been ground or has been damaged in use), and there is thus an intermittent abrasive action of the grinding wheel against the blade, the usual bouncing of the blade concerned on the finger guide is avoided. This in turn avoids possible damage to the machine and results in a consistently high standard of grinding.
Adjustable stop means, not shown in Figure 3, are provided to limit the downward movement of the rollers 50. In this way, as the rollers run off the opposite ends of the blades in turn, they drop only a short distance. Consequently, as the next traverse movement of the grinding head commences, the rollers can quite simply engage the top surface of the blade to be ground to hold it down on the finger guide.
Turning now to Figure 4, in the slightly modified form of finger guide assembly there illustrated, the finger guide 30 itself is of inverted 'V' shape so that the arrangement can be used when grinding cylinder blades with either left hand or right hand helix. The only effective part of the guide is the rounded apex.
The arms 52 which carry the rollers 50 are in this case shown to be pivotally connected to respective mounting members 51 upstanding behind the finger guide 30. Tension springs 54 act on the respective arms 52 as in the previously described embodiment, but it can be seen that in this case respective screws 53 which extend through the arms abut against surfaces 55. The effective lengths of the screws 53 can be adjusted according to whether the cutter blade to be ground is of right hand or left hand helix and according to the helix angle.
The arrangement is such that the rollers 50 remain in the positions in which they are shown in the drawing until the assembly is traversed laterally into engagement with a cutter blade when the blade will pass beneath the rollers, lifting them slightly so that the screws 52 are raised out of engagement with the surfaces 55.
Various other modifications may be made. For example, it is not essential for the pressure members acting downwards on each blade of a blade cylinder in turn to include respective rollers. They could simply rub along the top surfaces of the blades in the same way that the finger guide rubs along their lower surfaces.

Claims

1. A machine for grinding mowing machine cylinder blades, the machine including means (12,14) for mounting a blade cylinder for rotation about the axis of its mounting shaft; a grinding wheel (24) mounted on a grinding wheel head (18) carried on guides (20) for traverse movement longitudinally of the blade cylinder; and a finger guide (30) which is mounted beneath the grinding wheel (24) as a support for each blade of the blade cylinder in turn as grinding takes place; characterised in that means are provided for acting downwards on each blade of the blade cylinder in turn as said blade rests on the finger guide (30), the arrangement being such that as a traverse movement of the grinding wheel head (18) takes place, the abutment of the finger guide (30) against the particular blade concerned causes the blade cylinder to rotate in timed relation to the traverse movement of the grinding wheel head (18) and in the appropriate direction according to the direction of traverse of the grinding wheel head, the means for simultaneously acting downwards on the particular blade concerned ensuring that said blade is maintained in contact with the finger guide (30) throughout the grinding operation on said blade.

2. A machine according to claim 1, further characterised in that the means for acting downwards on each blade of the blade cylinder in turn as said blade rests on the finger guide (30) are constituted by a pair of spring loaded pressure members (52) located on the opposite sides of the grinding wheel.

3. A machine according to claim 2, further characterised in that the pair of spring loaded pressure members (52) act independently of each other.

4. A machine according to either one of claims 2 and 3, further characterised in that the spring loaded pressure members include respective rollers (50) arranged to engage and ride along the top surface of each blade of the blade cylinder in turn as its lower surface bears against the finger guide (30).