GB2334467A

GB2334467A - Circular saw grinding apparatus

Info

Publication number: GB2334467A
Application number: GB9903160A
Authority: GB
Inventors: John Podgorski
Original assignee: Spear and Jackson International Ltd
Current assignee: Spear and Jackson Holdings Ltd
Priority date: 1998-02-24
Filing date: 1999-02-12
Publication date: 1999-08-25
Anticipated expiration: 2019-02-12
Also published as: GB9803667D0; GB2334467B; GB9903160D0

Abstract

Apparatus for grinding circular saws (7, fig. 1) and the like comprises a grinding head 8 which executes a grinding stroke and pawl (31, fig. 3) which advances an indexing plate (18, fig. 3) mounted coaxially with the saw (7, fig. 1). Reciprocating movement of both the grinding head 8 and the pawl (31, fig. 3) is created by a common drive crank 24 attached to links 23 (and 39, fig.3) which cause respective connected links 22 (and 37, fig. 3) to reciprocate through arcs, the reciprocating movement of the grinding head 8 and the pawl (31, fig. 3) being imparted by respective cam followers 26 (and 36, fig. 3) which rest upon the connected links 22 (and 37, fig 3). The grinding and advancement stroke lengths may by adjusted by altering the point of contact between the respective cam follower 26 (and 36, fig. 3) and its abutting connected link 22 (and 37, fig. 3). Preferably the grinding head 8 is positioned at the start of its stroke by means of its cam follower 36 while during the stroke it moves under gravity.

Description

GRINDING APPARATUS This invention relates to grinding apparatus and, in particular, though not necessarily solely, to apparatus used to sharpen or re-grind circular saw blades.

Circular saw blades, of a type used in steel mills, need to be sharpened on a regular basis. In the past, many sharpening machines have typically carried a sharpening or grinding head on a vertical mast, the head being displaceable up and down the mast to accommodate blades of varying diameter. This has often necessitated the provision of a pit to ensure that, when blades of large diameter are being sharpened, the sharpening head is accessible to the machine operator.

The saw is conventionally mounted upon a spindle and the grinding head is displaced through a stroke so as to engage with the saw, grind the edge of a tooth, and then disengage from the saw. When the grinding head is no longer engaged with the saw, the saw is rotated in one direction by a amount corresponding to the angle subtended by a single tooth. The cycle is then repeated.

To ensure the teeth are all similarly cut, the rotation of the circular saw and the stroke of the grinding head must be synchronised. This often achieved by a hydraulic system, which, relative to mechanical systems, is complex and difficult to maintain.

A mechanical system is disclosed in GB 343 291 (Collet). A crank wheel has two connecting rods mounted upon it, offset from one another. The connecting rods are each attached to a respective pivoted link. One link causes a reciprocating movement in the grinding wheel carriage, whilst the other link rotates a wheel through an angle alternately clockwise and anticlockwise. This wheel applies alternating turning forces upon a clutch wheel, which are transmitted via a bevelled gear shaft to the cutter to be ground. A pawl catching upon teeth of the cutter limits the anticlockwise movement of the cutter, causing the clutch to slip. A stepwise advancement of the cutter, presenting each tooth in turn to the grinding wheel, is thus achieved.

The stroke of the grinding wheel is constrained linearly, whilst the link moving the grinding wheel sweeps an arc. A slide therefore is necessary to link the two, which requires manufacture to careful tolerances. The method of adjustment of the grinding stroke, by means of turning the spindle so as to move the nut under the trunnion, is difficult and inconvenient. The advancement of the cutter is also achieved by many moving parts which may wear and fail, in particular the clutch which transfers the movement of the connecting rod to the bevelled gears.

It is an object of the present invention to provide grinding apparatus which goes at least some way in improving on prior art systems or which will at least provide a useful choice.

Accordingly, the present invention provides grinding apparatus for effecting grinding operations on the peripheral edge of a circular saw or the like, said apparatus including; a spindle to rotatably support said circular saw about its centre, an advancement means, which rotate the circular saw through predetermined angle through successive operations, a grinding head which is displaced through a stroke so as to engage with the edge of the circular saw, grind a portion of the saw, and then disengage from the saw when said circular saw is mounted on said spindle, and a drive wheel upon which is connected a linkage means causing a reciprocating movement against one or more cam followers, so as to effect the advancement means and/or the grinding stroke.

Preferably, the grinding head is mounted upon a carriage, the carriage being adjustable along a horizontal axis towards and away from the edge of the circular saw so as to set the position of the grinding stroke.

Preferably, the advancement means comprises a pawl which is displaced through a stroke so as to engage with the edge of an index wheel, cause the saw to rotate, and then disengage from the index wheel. Preferably, the advancement stroke length is adjustable.

Preferably, at least one cam follower rests against a pivoted link which is reciprocated through an arc. Preferably, the point of contact between the cam follower and the associated link is adjustable so as to alter the length of the grinding stroke. Preferably, the point of contact between the one cam follower and the associated link is adjustable so as to alter the length of the advancement stroke.

Preferably, said linkage means is operable to position said grinding head at the start of said grinding stroke and, during said stroke, allow said grinding head to move under gravity to complete said grinding stroke.

Many variations in the way the invention may be performed will present themselves to those skilled in the art. The description which follows is intended as an illustration only of one manner of performing the invention and is not intended to be limiting. The scope of the present invention should be determined only by the appended claims.

One form of grinding machine embodying the various aspects of the invention will now be described, by way of example, with reference to the accompanying drawings in which; Figure 1 is a side view of the grinding machine, Figure 2 is a schematic side view (from the same side as that shown in Figure 1) of one linkage incorporated in the grinding machine, and Figure 3 is a schematic side view (from the opposite side to that depicted in Figure 2) of a further linkage incorporated in the grinding machine.

Referring to the drawings, the present invention provides grinding apparatus 5 having a spindle 6 on which a circular saw blade 7 and index plate 18 is rotatably mounted; and a grinding head 8, displaceable toward and away from the peripheral edge 9 of the blade, when the blade is mounted on the spindle, so as to effect a grinding operation on that part of the peripheral edge with which it comes into contact. The grinding head is displaceable toward and away from the edge 9 from a position to the side of the blade, so as to accommodate different blade diameters. In this way, the grinding head can be positioned for easy access and viewing by the operator without having to sink any part of the machine into a pit.

As can be seen in Figure 1, the grinding head 8 is mounted on a carriage 10, the carriage 10, in turn, being displaceable along a guide track 11..

Displacement of the carriage along the track 11 is effected by a screw (not shown) operated by rotating hand wheel 12. The guide track, in turn, may be displaced between a substantially horizontal position, and a position which is about 20 above the horizontal. Adjustment of the guide track position is effected by rotating adjustment screw thread 13 and reading off the position of the track on scale 14. The guide track and carriage assembly is pivoted about a dust extraction tube 45. The angle of the grinding head may in this way be altered so as to accommodate the grinding of teeth with positive and negative rakes.

Referring now to Figures 2 & 3, the apparatus includes advancement means 15 to advance the blade through a predetermined angle between unit grinding operations, and operating means 16 to permit and control movement of the grinding head through its operating stroke. Separate linkages, described in greater detail below, driven from a common drive motor 17, are provided to impart motion to the advancement means 15 and operating means 16, respectively.

In the embodiment shown, the advancement means comprises a pawl 31 which acts against teeth (not shown) formed in the periphery of an index plate 18 which, together with the blade 7, rotates with the spindle 6. The pawl 31 is mounted, in tum, on pawl base plate 19 which pivots on shaft 20. Adjustment wheel 21 is provided to allow adjustment of the angle of the pawl with respect to the pawi base plate 19.

Displacement is imparted to the pawl base plate, and thus to the pawl 31, by link arm 22. The lower end of the link arm 22 is connected to connecting rod 23, the connecting rod 23 being mounted on a crank pin of crank 24 which is rotated by drive motor 17. It will be appreciated that, as the crank 24 rotates, the link arm 22 is reciprocated through an arc, the centre of which is defined by pivot 25. As the link arm pivots so does the pawl base plate 19 and the pawl 31. The pawl base plate includes a cam follower, in the form of roller 26, to provide a smooth sliding action between the link arm 22 and the pawl base plate 19.

The upper pivot 25, on link arm 22, is included on adjustment elbow 27 which, itself, pivots about pivot point 28. The upper end of elbow 27 is connected to adjustment screw 29 rotated by hand wheel 30. It will be appreciated that when the screw 29 is withdrawn, the elbow 27 is rotated in a clockwise direction, thus raising the position of pivot 25 and moving the contact point of the roller 26 on the link arm 22, further down the link arm.

This has the affect of increasing the degree of displacement imparted to the pawl 31, thus increasing the size of the increment through which the index plate, and thus the blade, is rotated. In the position shown in Figure 2, the apparatus is configured to displace the pawl through its minimum stroke.

By means of screw 29, a continuous range of adjustment of pawl movement can be achieved between the upper and lower limits.

The operating means 16, configured and arranged to control the displacement of the grinding head 8 through its grinding stroke, is similar to the arrangement described above.

As can be seen from Figure 3, grinding head 8 is mounted on carriage 10 along with head drive motor 32.

The carriage 10 is mounted on grinding head actuating lever 34 for movement therewith. The lever 34 pivots about shaft 35 and includes a roller 36 at its lower extremity, which roller 36 bears on link arm 37. Link arm 37 is pivotally connected to adjustment elbow 38 at its upper end and pivotally connected to connecting rod 39 at its lower end. The opposite end of connecting rod 39 is mounted on a further crank pin on crank 24 so that the connecting rods 23 and 39 operate in spaced parallel planes positioned on opposite sides of drive motor 17.

Adjustment elbow 38 is pivoted about pivot point 40 by a screw 41 operated by hand wheel 42. In the position shown in Figure 3, the apparatus is configured to allow maximum displacement of the grinding head 8, and thus maximum depth of grinding stroke. By extending screw 41, the position of roller 36 will effectively move further up the link arm 37 thus reducing the degree of movement of the grinding head. It will be appreciated that, by operation of screw 41, a continuous range of adjustment of the grinding stroke can be provided between the upper and lower limits.

The grinding action operates as follows. As the crank 24 rotates, the grinding head is pivoted is a counter clockwise direction followed by a clockwise increment until the grinding tool contacts the blade. Upon the tool contacting the blade, the crank continues to rotate and, in so doing, displaces the link arm 37 out of contact with the roller 36. At this point the grinding head is further displaced solely by gravity, an action known as plunge grinding. The action of gravity is assisted by the provision of weights 43 on lever 34. The end of the grinding stroke is defined when the roller again contacts the link arm 37. the grinding head is mounted upon a carriage, the carriage being adjustable along a horizontal axis towards and away from the edge of the circular saw so as to set the position of the grinding stroke.

When the carriage 10, upon which the grinding head is mounted, is adjusted by being displaced along the horizontal guide track 11 in the manner described above, the position of the stroke is adjusted along the horizontal axis whilst the amplitude of the grinding stroke remains relatively unchanged. The spindle 6 can also be laterally displaced by means of a screw turned by a handle (not shown) in a similar fashion to the screw which displaces the grinding head carriage 10 along the guide track 11. By altering the separation between the spindle and the grinding head, different sizes of circular saws accommodated and operated upon.

It will be appreciated that the linkages 15 and 16, being spaced apart and mounted on a common crank, mean that advance and grinding mechanisms cannot collide and damage the apparatus. Obviously, the linkages are timed with respect to one another to ensure the blade is advanced as the grinding head 8 is withdrawn.

It will thus be appreciated that the present invention, at least in respect of the embodiment described above, provides a compact, versatile and effective form of grinding apparatus.

Claims

CLAIMS 1. Grinding apparatus for effecting grinding operations on the peripheral edge of a circular saw or the like, said apparatus including; a spindle to rotatably support said circular saw about its centre, an advancement means, which rotate the circular saw through predetermined angle through successive operations, a grinding head which is displaced through a stroke so as to engage with the edge of the circular saw, grind a portion of the saw, and then disengage from the saw when said circular saw is mounted on said spindle, and a drive wheel upon which is connected a linkage means causing a reciprocating movement against one or more cam followers, so as to effect the advancement means and/or the grinding stroke.
2. Grinding apparatus according to claim 1, wherein the grinding head is mounted upon a carriage, the carriage being adjustable along a horizontal axis towards and away from the edge of the circular saw so as to set the position of the grinding stroke.
3. Grinding apparatus according to either previous claim wherein the grinding stroke length is adjustable.
4. Grinding apparatus according to any previous claim, wherein the advancement means comprises a pawl which is displaced through a stroke so as to engage with the edge of an index wheel, cause the saw to rotate, and then disengage from the index wheel.
5. Grinding apparatus according to any previous claim, wherein the advancement stroke length is adjustable.
6. Grinding apparatus according to any previous claim, wherein at least one of the cam followers rests against a pivoted link which is reciprocated through an arc.
7. Grinding apparatus according to claim 6, wherein the point of contact between the cam follower and the associated link is adjustable so as to alter the length of the grinding stroke.
8. Grinding apparatus according to claim 6 wherein the point of contact between the cam follower and the associated link is adjustable so as to alter the length of the advancement stroke.
9. Grinding apparatus according to any previous claim, wherein said linkage means is operable to position said grinding head at the start of said grinding stroke and, during said stroke, allow said grinding head to move under gravity to complete said grinding stroke.
10. Grinding apparatus substantially as herein before described with reference to drawings.
11. A method of grinding the teeth of a circular saw blade by the use of the grinding apparatus claimed in any one of claims 1 to 10.