IE47084B1 - A sharpening machine for hedge cutters and other ciruclar saws - Google Patents

Abstract

A machine for sharpening a circular saw, such as a hedge cutter blade, in situ, comprises a stand (2) detachably fixable to a circular saw framework, a rotary grinding tool for sharpening a tooth of the saw, first means (5, 6a, 7) for pivotally mounting the grinding tool on the stand on an axis transverse to the axis of the grinding tool spindle, adjustable stop means (17) to limit the pivotal freedom of the grinding tool in one direction, and spring means (15) to hold the grinding tool in a resting attitude clear of the stop means (17), the strength of the spring means (15) being such that hand pressure can overcome it thus pivoting the grinding tool into an orientation determined by the stop means (17).

Description

This invention relates to sharpening machines. It relates in particular to a machine for sharpening the blade of a circular saw, more particularly still the blade of a hedge cutter.

A hedge cutter, in the sense used in this specification, is a tractor-mounted, usually articulated arm extending laterally of the tractor, bearing on its extremity remote from the tractor a large motor-driven circular saw, the arm being deployed and the motor energised by means of a hydraulic system powered by the tractor engine. In use the tractor is driven along the edge of a road parallel to a growing hedge, and the saw is deployed to intersect the hedge and trim it.

Hedge-cutter blades frequently encounter harder objects amid the hedge vegetation. They need sharpening often.

It is common practice to remove the blade for sharpening, but this is time -consuming. It is an object of this invention to provide a sharpener which can sharpen the blade in situ.

The invention therefore provides a machine for sharpening a circular saw which machine comprises a stand detachably fixable to a circular saw framework, a rotary grinding tool for sharpening a tooth of the saw, first means for pivotally mounting the grinding tool on the stand on an axis transverse to the axis of the grinding tool spindle, adjustable stop means to limit the pivotal freedom of the grinding tool in one direction, and spring means to hold the grinding tool in a resting attitude clear of the stop means, the strength of the spring means being such that 7 0 8 4 hand pressure can overcome it thus pivoting the grinding tool into an orientation determined by the stop means.

The invention provides, for preference, a machine for sharpening hedge cutter blades, the machine having the characteristics set out above.

To facilitate bringing the machine into sharpening relationship with a tooth of a circular saw, it is preferred that second means be provided for mounting the rotary grinding tool on a supplementary pivotal axis transverse to the axis of the grinding tool spindle, more preferably still second and third means for mounting the tool on two supplementary pivotal axis transverse to one another and to the grinding tool spindle, whereby flexibility of adjustment in three dimensions is imparted to the tool. It is preferred further to provide fourth means for displacing the grinding tool in non-pivotal fashion with respect to the stand.

All such second, third and fourth means,weather for pivotal mounting or for displacement, are lockable so that a given position and orientation of the grinding tool, once obtained, can be held.

In use the stop means is adjusted, relative to the spring means, so as to give the grinding tool, when forced by hand pressure into engagement with the stop means, a travelling path of such length that at one end of the path the tool, restrained by the spring means, is just clear of a tooth of the blade to be sharpened, and at the other end of the path the tool (if in rotation, has ground the tooth to a predetermined depth suitable for sharpening the same. The angle of cut is of course predetermined by the orientation of the machine in relation to the blade, and is fineadjusted by the setting of the second and/or third pivotal mounting means and/or the fourth means for displacing the tool, when such second, third and fourth means, or - 4 any of them, are present. The machine is normally, in use, secured to a convenient structural member of a hedge cutter. When a tooth has been sharpened the grinding tool is manually released, whereupon the spring means causes the tool to clear the tooth. The saw blade is then rotated to bring the next appropriate tooth into position for sharpening.

The invention will be understood in greater detail from the following description of a particular embodiment thereof, given by way of example only, with reference to the accompanying drawings, in which Fig. 1 is a perspective view of a sharpening machine for a hedge cutters; Fig. 2 is a side elevation of the machine of Fig. 1; Fig. 3 is a sectional front elevation of an enlarged 15 scale taken from Fig. 2 along the line IIX-III and viewed in the direction of the arrows; Fig. 4 is a perspective view of part of the sharpening machine of Fig. 1 having a base plate different in shape from the base plate shown in Figs. 1-3 of the drawings; · and Fig. 5 is a partial front elevation taken from Fig. 4 viewed in the direction of the arrows.

Referring now to the drawings in which like numerals of reference indicate corresponding parts in several of the figures, a hedge cutter blade sharpener 1 comprises a stand 2, a sleeve 3 having lugs 3a pivotally mounted on the stand 2 about an axis 3b, and a grinding unit having an arm 4 slidably and rotatably mounted in the sleeve 3 and lockable therein by means of a lock screw 8.

The stand 2 has a base plate 9 which is retained in use by locating members 10 on a convenient structural member 11 of a hedge cutter 12 with a circular saw cutting blade 13 shown in broken outline, the stand 2 being secured in use by a clamp 9a and a cooperating chain 9b.

The stand 2 has an extension 14 on which an adjustable clamp 16 is mounted by means of a screw 16a, the clamp having mounted between it jaws 16b and 16c (Fig. 2) one end of a stout coil spring 15. The screw 16a engages in a screwthreaded hole through the extension 14 and is lockable therein by conventional means. An adjustable stop 17 having a stop end 17a is slidably mounted on the extension 14 and limits the further possible pivotal travel of the grinding unit with its arm under hand pressure against the resistance of the screw 15, as shown by the dotted outlines d. in Fig. 2.

The stop 17 can be arrested by a lock unit 17b against further sliding motion.

The grinding unit comprises a hydraulically driven grinder motor 6 encased in a frame 6a which is pivotally mounted about an axis 7 in a grinder cradle 5 having the arm 4 and a similar arm 4a as extensions. In addition, an outrigger bearing (not shown) serves to protect the motor shaft against axial and/or radial loading, The arms 4, 4a are used as handles for manually tilting the grinding unit about the axis 3b to sharpen a tooth of the saw 13.

A pair of lock screws 18 serve to secure the motor 6 at a chosen angle of tilt within the cradle 5. A strut 19 pivoted to the cradle 5 is lockable by means of a sleeve and a lock screw 20 against an extension piece 21 of the cradle 5, this arrangement securing the motor 6 with greater efficiency than that of the lock screws 18, which latter may be omitted.

The motor 6 is driven by a supply of hydraulic fluid from a circuit including a feed conduit 22, a return conduit 23, a by-pass conduit 24, and a valve 25 operated by a manually controlled lever 26. The motor 6 is adapted to receive on the spindle thereof a saw grinding disc 27 which can be screened by a guard 28 shown only in Fig. 2.

In use, the sharpening machine is attached to a hedge cutter as shown, using the base 9 clamp 9a and cooperating chain 9b. The arm 4 is displaced and rotated within the sleeve 3 and the motor 6 pivoted within the cradle 5 until Λ70 84 - 6 the correct setting of the grinding disc 27 with respect to the blade 13 to be sharpened is found, whereupon the lock screws 8, 18 and 20 are tightened. A first tooth of the blade 13 is positioned beneath the grinding disc 27 (if necessary the blade 13 is temporarily arrested during the sharpening of each tooth). The operator grasps the arm 4 with one hand and the arm 4a with the other and gently but firmly pivots the grinding unit anticlockwise (as shown in the drawings) about the pivot 3b until this motion is brought to a halt by the stop end 17a of the stop screw 17 whereupon the arms 4, 4a are released by the operator and the spring 15 restores the grinding unit to its rest position. A second appropriate tooth of the blade 13 is positioned beneath the grinding disc and the above recited procedure repeated, and so for all the appropriate teeth, which may mean for example a set of alternate teeth. A second setting of the grinding unit, in the latter case, is then necessary before the second set of alternate teeth can be sharpened, because the cutting angle of the teeth of the second set is different from that of the teeth of the first set.

It will be appreciated that the machine specifically described is intended for use with hedge cutters having blades of one standard diameter. Should blades of differing diameters be presented for sharpening, it would be appropriate to redesign the machine so that the stand 2 is lockably extensible along its shaft.

Claims (7)

CLAIMS:

1. A machine for sharpening a circular saw which machine comprises a stand detachably fixable to a circular saw framework, a rotary grinding tool for sharpening a tooth of the saw, first means for pivotally mounting the grinding 5 tool on the stand on an axis transverse to the axis of the grinding tool spindle, adjustable stop means to limit the pivotal freedom of the grinding tool in one direction, and spring means to hold the grinding tool in a resting attitude clear of the stop means, the strength of the spring means being 10 such that hand pressure can overcome it thus pivoting the grinding tool into an orientation determined by the stop means.

2. A machine as claimed in claim 1 for sharpening hedge cutter blades.

3. A machine as claimed in claims 1 or 2 wherein second £2 means are provided for mounting the rotary grinding tool on a supplementary pivotal axis transverse to the axis of the grinding tool spindle.

4. A machine as claimed in claim 1 or 2 wherein second and third means are provided for mounting the tool on two 20 supplementary pivotal axes transverse to one another and to the grinding tool spindle, whereby flexibility of adjustment ' in three dimensions is imparted to the tool.

5. A machine as claimed in claims 1 or 2 wherein fourth means are provided for displacing the grinding tool in non25 pivotal fashion with respect to the stand. 4-70 8 4

6. A machipe as claimed in claims 3,4 or 5 wherein said second, third and fourth means when provided whether for pivotal mounting or for displacement are lockable so that a given position and orientation of the grinding tool, 5 once obtained, can be held.

7. A machine for sharpening a circular saw substantially as herein described with reference to or as illustrated by the accompanying drawings.