TECHNICAL FIELD

The present invention refers to an apparatus in connection to an automatic sharpening machine for saw blades, saw bands and rotating saw blades preferably of the type com¬ prising a main support on which a single or double-armed lever is rotatably arranged around a shaft, at one of the end portions of which lever an electrically powered grind¬ ing disc is arranged, for giving the grinding disc such a movement in relation to the separate tooth on the saw blade, the saw band or the rotating saw blade that the back side as well as the front side of the tooth will be grinded to a predefined form, the sharpening machine being arranged in such a way that the teeth of the saw blade, the saw band or the rotating saw blade stepwise is moving in a straight or circular grinding path to an adjusted grinding position for the blade, band or rotating blade in question, the grinding disc, movable in relation to the path, is arranged to grind the back side of the tooth by means of a recipro¬ cating movement during the feeding of the separate tooth to the grinding position and with the tooth in the grinding position to grind its front side.

BACKGROUND ART

Known automatic grinding machines for saw blades, saw bands and rotating saw blades usually comprise complicated and difficult to adjust arrangements for control and co¬ ordination of the movements of the saw and the grinding disc. It is especially complicated if there is a need to often change the adjustment for the form and pitch of the teeth. The adjustment for the form of the tooth is carried out by changing guiding disks or grinding masters and ere-

ates a certain disassembly and assembly work including checks and readjustments when needed. The adjustment of the feeding for another tooth pitch can also create certain problems as the feeding is usually carried out by means of a ratchet pawl which grips the tooth in turn to be grinded while the grinding disc is still positioned over the point on the preceding tooth and the grinding cycle is then started with the grinding of the front side of the tooth. An incorrect adjustment may cause the ratchet pawl to be grinded as well. It is also necessary for the grinder to be alert so that the adjustment is carried out on a portion of the blade which has not been damaged since a damaged tooth subjected to repeated grinding could cause a certain par¬ tial alteration of the tooth pitch.

In the directions for use of a known saw blade sharpening machine more than ten different types of saw teeth are shown with varying tooth pitch for each type.

This large number of variants makes general saw blade sharpening machines complicated and expensive at the same time as the directions for use become thick and obscure. For most people having a need of saw blade sharpening ma¬ chines it is sufficient if they can grind one or two dif- ferent blade types and the change from one type of blade to another should be simple and not requiring special knowl¬ edge.

BRIEF DESCRIPTION OF THE INVENTION

The object of the present invention is to provide an appa¬ ratus for more simple and stable co-ordination of the grinding and feeding movements in an automatic saw blade sharpening machine. Another object is to provide an appara- tus which offers fast interchange between a few of the com¬ mon combinations of the form of the teeth and the tooth

pitch. A further object is to provide an apparatus which eliminates the need for means for adjustment in view of the form of the teeth and the tooth pitch. These and other ob¬ jects will be attained by means of an apparatus the charac- teristics of which appear from the characterising features of the appended claims.

DESCRIPTION OF THE DRAWINGS

An embodiment of the invention will be described more in detail with reference to the appended drawing on which fig¬ ure 1 schematically and in a plane view shows a sharpening machine for sharpening of saw bands, figure 2 shows in a side view an arrangement for control of the grinding and feeding procedure and figure 3 shows a control member coor¬ dinating the grinding and feeding movements.

PREFERED EMBODIMENT

Figure 1 shows schematically and in a plane view a sharpen¬ ing machine for sharpening of saw band 2 of the type used in band saw machines. The sharpening machine 1 comprises a main support 3 on which a double-armed lever 4 is rotatably arranged around a shaft 5. At one of the end portions of the lever an electrical motor 6 is arranged having a grind¬ ing disc 7 mounted on its shaft in a position for machining the teeth 8 on the saw band 2 which for progressive forward feeding is positioned in a grinding path 9 and during the feeding is moving in a horisontal loop, not shown, around the sharpening machine. The grinding path 9 is composed of a channel between two parallel rigid rulers the width of which channel can be adjusted and the facing sides of which rulers are covered with a friction material which keeps the saw band in position when it is not fed forward.

At the other end portion of the lever a detector means in the form of a roller 10 is arranged on an adjustable car¬ rier 11 which roller bears against a cam disk 12 which to¬ gether with a shaft pivot 13 positioned eccentrically on the cam shaft 12 form the control means 14 which coordi¬ nates the specific grinding and feeding movements for the type of saw tooth which is grinded at the moment, the con¬ tour of the outer edge of the cam disk 12 which is detected by the roller 10 decides the grinding movements while the movement of the shaft pivot 13 transferred by the ratchet pawl 15 controls the feeding of the separate teeth 8 of the saw band to the grinding position defined by the end posi¬ tion of the ratchet pawl 15.

Figure 2 shows schematically and in a side view the ar¬ rangement for control of the grinding and feeding procedure as well as relevant end portions of the main support 3, the grinding path 9 and the lever 4. The control arrangement comprises a second support 16 arranged on the main support 3, in figure 2 hidden by the cover 17 which protects a gear unit, also hidden, by means of which the speed of the elec¬ trical motor 18 is reduced to a speed suitable for the out¬ put shaft 19. The control means 14 is mounted on the shaft 19 which control means comprises a cam disk 12 having an eccentrically positioned shaft pivot 13 from which the ratchet pawl 15 originates for progressive forward feeding of the teeth 8 of the saw band to the grinding position in the grinding path 9. The grinding position is defined by the end position of the ratchet pawl 15 in which the ratchet pawl after a complete feeding movement stops and reverses its movement and in which position the front side of the advanced tooth at the return motion of the ratchet pawl is grinded from the point of the tooth towards the root of the tooth due to the action of the cam disk 12 on the lever 4.

Figure 3 shows a control means 14 in which all data valid for the profile of the saw tooth 8 in question are stored in the form of the outer contour of the cam disk as well as the position of the shaft pivot 13 in relation to the curve of the cam disk. At the start of a grinding procedure there is a need to make adjustments in view of among other things the wear of the grinding disc. By means of the adjusting screw 21 on the ratchet pawl 15 the location in the grind¬ ing position of the saw teeth 8 and consequently the grind- ing of the front side of the respective tooth 8 could thus be adjusted and by means of the adjusting screw 20 the grinding depth and consequently the grinding of the back side of the respective tooth 8 could be adjusted.

At the sharpening of a saw band having another form of the teeth than the one corresponding to the control means 14 mounted in a sharpening machine this control means is eas¬ ily removed and replaced with a suitable control means by unscrewing the locking screw 22 in the center of the shaft 19. Additionally it is only required that the ratchet pawl is moved over to the newly mounted control means and that the adjustment for grinding position and grinding depth is carried out to get the sharpening machine ready for its new task.

When grinding saw blades for for instance frame saws an es¬ pecially adapted grinding path 9 is required and when sharpening rotating saw blades a taller support is required comprising a vertically adjustable shaft around which the saw blade is turned in the feeding movement.