WO2000069596A1

WO2000069596A1 - Sharpening device for disk blades

Info

Publication number: WO2000069596A1
Application number: PCT/IB2000/000598
Authority: WO
Inventors: Tristano Ciani
Original assignee: Julia Utensili S.R.L.
Priority date: 1999-05-12
Filing date: 2000-05-09
Publication date: 2000-11-23
Also published as: IT1310565B1; AU4138700A; ITUD990095A1; ITUD990095A0

Abstract

Device (10) to sharpen disk blades (36) equipped with a cutting edge defined by at least a chamfer made on one side of the disk, comprising a mandrel body (12) suitable to couple with at least a grinding wheel (20) and equipped with motor means (11) suitable to transmit to the grinding wheel (20) a movement of rotation around its own axis and with actuator means suitable to transmit to the grinding wheel (20) a movement of translation to selectively take it into an inactive position of non-interference with the cutting edge or into the sharpening position in contact with the cutting edge.

Description

"SHARPENING DEVICE FOR DISK BLADES" * * * * *

FIELD OF THE INVENTION This invention concerns a sharpening device for disk blades, as set forth in the main claim, for cutting machines employed in various technical fields, such as for example in the paper industry.

The invention may be used directly on the cutting machines to carry out an "in line" sharpening operation after a predetermined number of cutting cycles, or used to make autonomous sharpening machines suitable to sharpen the blades outside the cutting line.

BACKGROUND OF THE INVENTION The state of the art includes cutting machines used in the paper industry to divide reels of paper, such as toilet paper, kitchen roll paper or otherwise, into rolls of a defined length.

Such machines are usually equipped with one or more disk blades, keyed onto a supporting shaft by means of retaining flanges.

These machines are suitable to transmit to the supporting shafts of the disk blades both a movement of rotation around the relative axis, and also a movement of revolution in order to cut in sequence several reels of paper which are made to advance in a line in correspondence with the circumference of revolution of the blades.

Conventional disk blades have a transverse section defined by a first inner or central segment, substantially flat, suitable to couple with the retaining flanges, and a second peripheral segment, suitable to cut the reel transversely to make the rolls.

The peak of the peripheral segment has one or two chamfers, inclined by a defined angle and provided on one or both sides of the disk.

The disk blades used in cutting machines employed in the paper industry carry out a very large number of cuts every minute and therefore the sharpness is soon dulled. These blades therefore need sharpening frequently, and this is usually done by using a group of grinding wheels, equipped with idler movement, which are brought into contact with the edge of the disk blade which has to be sharpened. For example, the state of the art includes a sharpening device comprising two idler grinding wheels arranged in a "V" and mounted on a support driven by a pneumatic actuator.

The state of the art also includes a variant where the idler grinding wheels are coupled with the relative support by means of elastic elements, usually consisting of one or more half-elliptic springs, which allow the grinding wheels to follow the movements of the blade in order to carry out the sharpening operation even when there are possible oscillations or pivoting of the blade due to slight imperfections or wear. In both solutions, the grinding wheels have an idler movement and therefore their ability to restore the edge of the blade is very limited.

In designing sharpening devices, moreover, it must be taken into account that, if the grinding wheels are not perfectly positioned with respect to the blade or if they thrust too much against the edge thereof, they can make the disk slightly elliptic, thus compromising the accuracy of the cut, or notching the cutting edge, causing ruling in the cut section of the roll of paper. The American patent US-A-5, 090, 281 describes a machine to cut undulating cardboard, which uses a blade with a rotary disk and wherein there is a sharpening mechanism for the latter. The sharpening mechanism comprises a grinding wheel, which is mounted rotating at the end of an oscillating arm, pinned onto the frame of the machine, and is made to rotate by a pneumatic motor. The oscillating arm makes the grinding wheel follow a curved path as it approaches the blade to be sharpened. Therefore the angle of incidence between the grinding wheel and the blade is not constant, but varies continuously according to the arc of a circle described by the oscillating arm. This has the negative consequence that the blade is not sharpened in a rectilinear and uniform manner.

The present Applicant has devised and embodied this invention to overcome these shortcomings and to obtain further advantages .

SUMMARY OF THE INVENTION The invention is set forth and characterised in the main claim, while the dependent claims describe other characteristics of the invention.

The purpose of the invention is to provide a sharpening device for disk blades, which will be economical, simple to use and will give an accurate and speedy sharpening operation.

Another purpose of the invention is to provide a sharpening device which can be applied on any cutting machine whatsoever, to allow the blade to be sharpened "in line", that is, without needing to remove it from the machine .

A further purpose is to provide a sharpening device which, thanks to the high accuracy of the sharpening, allows to increase the working life of the disk blade and consequently the productivity of the cutting machines, at the same time reducing the management costs.

A further purpose is to reduce the overall times and costs of the sharpening operations, also reducing the amount of material removed with every restoration operation.

The device according to the invention comprises a mandrel driven by motor means and provided with coupling means for at least a grinding wheel . The grinding wheel may be of any size and conformation, chosen according to the type of blade to be sharpened and its cutting profile.

The mandrel of the device according to the invention, apart from making the grinding wheel rotate at a defined and pre-settable speed, is also suitable to move axially between a first position in which the grinding wheel supported by the mandrel is located in a position of non-interference with the edge to be sharpened and a second position in which the grinding wheel moves into contact, with a defined force of thrust, with the edge to be sharpened.

According to the invention, the mandrel allows to adjust both the first and second position, and also the force of thrust and the speed of rotation of the grinding wheel, in a completely autonomous manner with respect to each other and to the blade to be sharpened, thus allowing to adapt the sharpening operation to contingent requirements.

According to a variant, the device according to the invention is equipped with attachment means which allow to associate it in a removable manner both to a cutting machine so that in line sharpening operations can be carried out after a pre-determined number of cutting cycles, or to any bearing structure to achieve an autonomous sharpening machine .

According to a variant, the attachment means also comprise adaptation means which allow to associate the sharpening device according to the invention to any cutting machine whatsoever, even substituting the sharpening devices of a conventional type equipped with grinding wheels with idler movement .

By using a single device according to the invention it is possible to sharpen blades which need to be sharpened on a single side, while by using two devices according to the invention it is possible to sharpen disk blades which need to be sharpened on both sides.

BRIEF DESCRIPTION OF THE DRAWINGS These and other characteristics of the invention will become clear from the following description of two preferred forms of embodiment, given as a non-restrictive example, with reference to the attached drawings wherein: Fig. 1 is a three-dimensional view of a sharpening device according to the invention; Fig. 2 is a longitudinal section of the device shown in Fig. 1 in a first operating position;

Fig. 3 shows the device of Fig. 2 in a second operating position; Fig. 4 shows a section from A to A of Fig. 3; Fig. 5 shows a variant of Fig. 2 ; Fig. 6 shows a section from B to B of Fig. 5;

Fig. 7 shows the devices of Fig. 2 and Fig. 5 while a disk blade is being sharpened.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT With reference to the attached drawings, a sharpening device 10 according to the invention comprises in its essential parts an electric motor 11, a mandrel body 12 and a grinding wheel 20 of a conventional type.

The mandrel body 12 comprises a containing structure 13 defined by a central body 13a closed at the two ends respectively by a front flange 13b and a rear flange 13c.

The containing structure 13 is equipped inside with four bars 21 which function as a guide for a slider 14 defined by a central body 14a closed at the two ends respectively by a front flange 14b and a rear flange 14c.

The flanges 14a and 14b are equipped, in corresponding positions, with through holes 22 into which the bars 21 are inserted. As shown in Fig. 4, into every through hole 22 a ball bushing 23 is inserted, suitable to facilitate the sliding of the slider 14, to prevent wear on the bars 21 and to limit friction between the slider 14 and the containing structure 13. A shaft 15, free to rotate, is associated with the slider 14 and equipped at one end with a flange 16 to attach the grinding wheel 20 and, at the opposite end, a hollow, cylindrical element 17 suitable to couple coaxially with the shaft 18 of the motor 11. The shaft 18 is equipped with a key 18a suitable to be inserted into a corresponding longitudinal groove 17a made on the inner surface of the hollow cylindrical element 17.

In this way, the shaft 15 is angularly constrained to the shaft 18 but is able to move axially with respect to the latter to follow the movements imparted to the slider 14, as will be described in more detail hereafter.

The shaft 15 is associated with the slider 14 by means of five radial bearings; four bearings 19 couple it with the central body 14a and one bearing 24 couples it with the front flange 14b.

The shaft 15 is axially constrained to the slider 14 at the front part by means of a ring nut 25 coaxial thereto and at the rear part by means of the cylindrical element 17.

In this way, although the shaft 15 is free to rotate, it is constrained to the slider 14 in its axial movements.

With reference to Figs. 2 and 3, it can be seen how the slider 14 is suitable to move between an advanced position (Fig. 2) in which the grinding wheel 20 is arranged in a position of non-interference at a defined distance "d" from the disk blade 36 to be sharpened, shown in the Figure by a line of dashes, to a retracted position (Fig. 3) in which the grinding wheel 20 moves, with the force previously imparted, to a sharpening position abutting against the edge of the disk blade 36 which is to be sharpened.

According to the invention, the sharpening device 10 also comprises an adjustment organ 26 suitable to define the maximum travel of the slider 14 and to limit its movements between a position of maximum retraction and a position of maximum advance .

The adjustment organ 26 comprises a rod 27 equipped with a first end attached to the slider 14 and a second end suitable to emerge from the containing structure 13 through a slit 28.

The second end is fork-shaped and suitable to partly encircle the central segment 29a, with a reduced section and unthreaded, of a screw 29 arranged transverse with respect to the rod 27 and screwed into a box-like structure 30. The length of the central segment 29a defines, when the thickness of the rod 27 has been subtracted, the travel of the slider 14 while the position of the screw 29 with respect to the box-like structure 30 determines the aforementioned positions of maximum advance and maximum retraction of the grinding wheel 20 with respect to the disk blade 36.

During the sharpening operation, obviously, the grinding wheel 20 abuts against the edge of the disk blade 36 which is to be sharpened, with the force previously imparted, before it reaches the position of maximum retraction.

In the embodiment shown in Figs. 1-3, the slider 14 is normally kept in the advanced position shown in Fig. 2 by compression springs, not shown in the drawings, associated at a first end with the central body 14a of the slider 14 and at the opposite end with the rear flange 13c of the containing structure 13.

According to the invention, between the containing structure 13 and the slider 14 an annular chamber 31 is defined in the front part of the mandrel body 12; the annular chamber 31 communicates with the outside through a duct 32 connected by means of a tube 34 to a compressor which is not shown here. To be more exact, the annular chamber 31 is defined by the sealed-tight coupling, made possible by a pair of annular seals 33, of a protruding part 114b of the front flange 14b and a recessed part of the front flange 13b.

A pressure regulator 35 is connected to the tube 34 and allows to vary in a desired manner the pressure of the air supplied by the compressor to the annular chamber 31.

The air which passes through the regulator 35 fills the chamber 31 until it overcomes the force exerted by the springs and thus takes the grinding wheel 20 into contact with the edge of the blade 36 which is to be sharpened.

By acting on the pressure regulator 35 it is therefore possible to vary the force of thrust of the grinding wheel 20 against the edge to be sharpened to adapt it to the specific sharpening requirements. Apart from this advantage, by setting the pressure at a relatively low value, it is possible to obtain a softening effect of the thrust movement of the grinding wheel 20 against the blade 36, suitable to follow any possible imperfections of the edge to be sharpened. By acting on the adjustment means 26 it is possible to vary the position of maximum advance and/or maximum retraction of the slider 14 so as to be able to also grind disk blades 36 with a very damaged cutting edge. In the case of Figs. 2 and 3, the blade 36 is of the type which needs sharpening on one side only, the opposite side being covered by a layer of material of high strength and resistance. To be more exact, the side to be sharpened is the inner one with respect to the cutting machine and the blade 36 is located in a position between the grinding wheel 20 and the containing structure 13 so that the motor 11 is located in a position diametrically opposite, with respect to the blade 36, to the position of the drive means, not shown here, of the blade 36.

The device 10 according to the invention, therefore, can be installed on any cutting machine whatsoever, also to replace conventional sharpening devices. In this case, this replacement is made possible by a removable adapter plate 37 (Fig. 1) associated with the containing structure 13.

Figs. 5 and 6 show another embodiment of the device 10 according to the invention used to sharpen a blade 36 of the type described above, except that, in this case, the side to be sharpened is the outer one with respect to the cutting machine .

In this embodiment, the slider 14 is normally kept in the retracted position shown in Fig. 6, by compression springs 40 associated at a first end with the central body 14a of the slider 14 and at the opposite end with the front flange

13b of the containing structure 13.

Between the containing structure 13 and the slider 14 two chambers 39 are defined in the rear part of the mandrel body 12; the chambers 39 communicate with the outside through two ducts 32 connected, in the same way as in the embodiment shown in Figs. 1 and 2, to a compressor.

To be more exact, each chamber 39 is defined by the sealed-tight coupling, made possible by a seal 38, of a protruding part 113c of the rear flange 13c (Fig. 6) and a corresponding recess made on the rear flange 14c and on the central body 14a of the slider 14. In this case, by activating the pressure regulator 35 the air supplied by the compressor is able to enter the two chambers 39 until it overcomes the force exerted by the springs 40 and takes the grinding wheel 20 into contact with the edge of the blade 36 to be sharpened. In this embodiment, in the coupling zone between the front flanges 13b and 14b there is a scraper ring 41 suitable to prevent infiltrations of dirt and dust inside the containing structure 13.

Fig. 7 shows the case of a blade 136, which is equipped with a cutting edge defined by two opposite chamfers which both require sharpening.

In this case a first chamfer is sharpened by a device 10 of the type shown in Figs. 1 and 2, and the opposite chamfer is sharpened by a device 10 of the type shown in Figs. 5 and 6.

In this embodiment too, the mandrel bodies 12 and the motors 11 associated therewith are arranged in a position of non-interference with the drive means, which are not shown here, of the blade 136, with the advantages explained above. With the three embodiments proposed, therefore, it is possible to sharpen disk blades 36 which need sharpening only on the inner side with respect to the machine with which they are associated (Figs. 2-3), and also disk blades 36 which need sharpening only on the outer side with respect to the machine with which they are associated (Figs. 5-6), and also disk blades 136 which need sharpening on both sides (Fig. 7) .

It is obvious that modifications and additions may be made to the invention, but these shall remain within the field and scope thereof.

For example, the electric motor 11 may be replaced by a pneumatic or hydraulic motor, or the chambers 31 and 39 may be associated with a hydraulic plant, instead of a compressor.

Claims

1 - Device to sharpen disk blades equipped with a cutting edge defined by at least a chamfer made on one side of the disk, said device comprising a mandrel body (12) provided with a transmission shaft (15) on which a grinding wheel (20) is assembled, motor means able to make said transmission shaft (15) and said grinding wheel (20) rotate around their own axis of rotation and actuator means able to selectively displace said grinding wheel (20) between an inactive position of non-interference with the cutting edge and a sharpening position in contact with the cutting edge, the device being characterised in that said actuator means are able to axially translate said grinding wheel (20) along its own axis of rotation, in order to selectively take it into said inactive position or into said sharpening position, in such a manner that the angle of incidence between said grinding wheel (20) and the blade to be sharpened remains substantially constant.

2 - Device as in Claim 1, characterised in that the actuator means comprise first regulator means (35) suitable to allow variations in the force of thrust of the grinding wheel (20) against the cutting edge of the disk blade (36) to be sharpened.

3 - Device as in Claim 1, characterised in that the actuator means comprise second adjustment means (26) suitable to allow variations in the travel of the grinding wheel (20) .

4 - Device as in Claim 1, characterised in that the motor means comprise adjustment means suitable to allow variations in the speed of rotation of the grinding wheel (20) . 5 - Device as in Claim 1, characterised in that the mandrel body (12) comprises a stationary containing structure (13) on which a movable slider (14) is mounted, to which slider (14) a shaft (15) is rotatably constrained and is equipped with coupling means (16) to couple with the grinding wheel (20), the transmission shaft (15) being coupled with the motor means and the slider (14) being coupled with the actuator means . 6 - Device as in Claim 1, characterised in that the motor (11) means are of the electric type.

7 - Device as in Claim 1, characterised in that the motor means (11) are of the pneumatic type.

8 - Device as in Claim 5, characterised in that the motor means (11) comprise a drive shaft (18), coupling means being provided to angularly constrain the transmission shaft (15) to the drive shaft (18) and at the same time leave it free to move axially to follow the movements of the slider (14) .

9 - Device as in Claim 8, characterised in that the coupling means comprise a hollow cylindrical element (17) axially solid with the transmission shaft (15) and suitable to be keyed onto the drive shaft (18) , the drive shaft (18) or the hollow cylindrical element (17) being equipped with means (18a) suitable to be inserted into corresponding grooves (17a) provided on the hollow cylindrical element (17) or the drive shaft (18) .

10 - Device as in Claim 1, characterised in that the actuator means comprise pneumatic means functionally associated with the slider (14) and suitable to be fed with a fluid under pressure.

11 - Device as in Claim 10, characterised in that the pneumatic means comprise at least a chamber (31,39) suitable to define a hermetically closed volume and associated with means to produce a fluid under pressure, the chamber (31,39) being suitable to cooperate with the slider (14) to vary its axial position.

12 - Device as in Claim 11, characterised in that the chamber (31,39) is suitable to be defined by the sealed coupling of the slider (14) and the containing structure (13).

13 - Device as in Claim 11, characterised in that the pneumatic means comprise a pressure regulator (35) suitable to vary the pressure of the fluid introduced into the chamber (31,39) .

14 - Device as in Claim 10, characterised in that the pneumatic means cooperate with elastic means suitable to contrast the force of thrust exerted by the fluid on the slider (14) .

15 - Device as in Claim 4, characterised in that the containing structure (13) has a box-like closed conformation suitable to contain the slider (14) and internally equipped with guide means along which the slider (14) is suitable to slide axially.

16 - Device as in Claim 15, characterised in that the guide means comprise at least two longitudinal bars (21) each of which is suitable to be inserted into a respective through hole (22) made on the slider (14). 17 - Device as in Claim 16, characterised in that the through hole (22) is equipped with a ball bushing (23) .

18 - Device as in Claim 3, characterised in that the adjustment means (26) comprise an extension (27) of the slider (14) suitable to cooperate with end-of-travel elements suitable to define at least a position of maximum advance and a position of maximum retraction of the slider (14) .

19 - Device as in Claim 18, characterised in that the end- of-travel elements are defined by the two ends of a segment (29a) with a reduced, unthreaded section of a screw (29) inserted into an aperture made on the extension (27) so that its length substantially determines the maximum travel of the slider (14) while the position of the screw (29) determines the positions of maximum advance and maximum retraction of the said slider (14) .

20 - Device as in Claim 1, characterised in that it is equipped with adaptation means (37) suitable to allow it to be assembled on any type of cutting machine.