US3328924A - Apparatus for sharpening rotary cutters - Google Patents

Description

July 4, 1967 H. WARD APPARATUS FOR SHARPENING, ROTARY CUTTERS 6 Sheets-Sheet 1 Filed June 12, 1964 lnvenlor fi flzz 40 :4

July 4, 1967 H. WARD APPARATUS FOR SHARFENING ROTARY CUTTERS 6 Sheets-Sheet 2 Filed June 12, 1964 I nvenlor H1919? ddmafi y M M gzz; A Barneys Jul 4, 1967 H, WARD 3,328,924

APPARATUS FOR SHARPENINGROTARY CUTTERS Filed June 12, 1964 6 Sheets-Sheet 5 I W FJ l lnver ztor /7 A ?R) (AJA RoL A ttorneys y 4, 1967 H. WARD 3,323,924

APPARATUS FOR SHARPENING ROTARY CUTTERS Filed June 12, 1964 6 Sheets-Sheet 4 A ttorneyg July 4, 1967 H. WARD APPARATUS FOR SHARPENING ROTARY CUTTERS 6 Sheets-Sheet 5 Filed June 12, 1964 Rah-.5?? k 9 5. x i 2 I iIEEEEEEi.

Invenlor HARR) Afl Attorneys July 4, 1967 H. WARD APPARATUS FOR SHARPENING ROTARY CUTTERS Filed June 12, 1964 6 Sheets-Sheet 6 9 ap-LEE a; H L

Inventor 644KB Q/A Rd.

. B Q 6%, Attorneys United States Patent 3,328,924 APPARATUS FOR SHARPENIN G ROTARY CUTTERS Harry Ward, London, England, assignor, by mesne assignments, to AME International Limited, London, England Filed June 12, 1964, Ser. No. 374,645 Claims priority, application Great Britain, June 13, 1963, 23,637/ 63 7 Claims. (Cl. 51-249) This invention relates to the sharpening by grinding of rotary cutters of the type having one or more knives whose cutting edges can be defined geometrically as lying in a cylindrical surface whose axis is the axis of rotation of the cutter. In many such cutters the cutting edges are parallel to the axis, but they may lie on helices or on any other lines lying in the cylindrical surface.

According to the invention, a machine having a rotary cutter rotating about an axis and having one or more knives with cutting edges lying in a cylindrical surface, further has means for sharpening the knives comprising a disc grinding wheel mounted for rotation about an axis substantially perpendicular to a plane containing the axis of the rotary cutter, the rim of the grinding wheel being hollowed to match the cylindrical surface, and a carriage on which the grinding wheel is mounted and which is arranged to reciprocate along the full length of the cutting edges parallel to the axis of the cutter and to dwell at one end of its reciprocating movement, and a dresser for maintaining the contour of the hollowed rim of the grinding wheel, mounted on an arm which is pivoted about an axis parallel to, adjacent to, and adjustable with respect to, the axis of the rotary cutter, at the end of the cutter at which the carriage dwells.

In the preferred arrangement, the dresser is a diamond, which is mounted on the end of an arm whose other end is pivotally mounted on an eccentric sleeve, which is itself mounted coaxially with the rotary cutter.

This invention is particularly applicable to machines of the rotary drum type used for cutting leaf tobacco. In these machines the cutter has a considerable number of knives slightly skew to the axis and equally spaced around its circumference. These machines present the advantage that if the knives are closely spaced around the circumference of the cutter, the cutting is practically continuous and so the output of cut tobacco is high. In order to make this output as high as possible, the knives must 'be kept constantly sharp by grinding them while the machine is working. At the same time the knives must move as fast as possible, consistent with good cutting, for the same reason. Accordingly the problem that arises in makingsuch a machine is to ensure that the grinding wheel will remove some metal from the cutting edges of the knives, without distorting or overheating them and without producing rapid Wear of the grinding wheel, in an extremely limited time. If the grinding action has to take place too quickly, both the cutting edges and the wheel suffer.

The grinding wheel is arranged on the opposite side of the cutter from the mouthpiece through which the tobacco is fed, and the cutter is rotated so that the knives pass down across the mouthpiece, and upwards across the rim of the grinding wheel. As the cutting edges of the knives are continuously sharpened, metal is worn away from them, and at the same time the rim of the grinding wheel is worn away. In order to compensate for this wear, the knives are fed progressively outwards from the cutter. A particular mechanism for carrying this out is described in British Patent No. 665,653, for example. The knives are moved outwards a small distance at each end of the reciprocating movement of the carriage, when the grinding wheel is just clear of the cutting edges.

To take account of the wear of the grinding wheel which slowly decreases its diameter, the wheel is fed in towards the cutter, each time the carriage reaches the end of the cutter at which the dresser is mounted.

The accompanying drawings show the relevant parts of one example of a tobacco cutting machine constructed in accordance with this invention. In these drawings:

FIGURE'l is a side view of the drum and grinder mechan-ism, with parts in section on the line I-I in FIGURE 2;

FIGURE 2 is a rear view, i.e., a view from the left in FIGURE 1, with most of the drum, and rear portions of the uprights, main beam, and grinder housing broken away;

FIGURE 3 is a fragmentary section on the line IIIIII in FIGURE 2;

FIGURE 4 is an enlarged fragmentary section on part of the line IV-IV in FIGURE 2;

FIGURES 5 and 6 are sections on the line VV in FIGURE 4, showing different operating positions; and

FIGURE 7 is an exaggerated diagram showing the action of the dresser.

As shown in FIGURE 1, the machine includes upper and lower conveyors 2 and 4 which deliver leaf tobacco through a mouthpiece 6. As the tobacco emerges from the mouthpiece, moving towards the right in FIGURE 1, it is sliced by knives 8 on the drum 10. This drum rotates at high speed on a shaft 12. It is supported by two uprights 14 which are pivoted to the main frame of the machine at 16, and which are very precisely adjusted in position in relation to the mouthpiece by means which are not shown as they do not directly concern the present invention.

The two uprights 14 are linked by a main 'beam 18 from the two ends of which there extend forward projections '20, which support two tubular rails 22. On these rails there slides a carriage 24 carrying a grinder. This grinder includes a disc grinding wheel, 26, a motor 28, and a belt drive 30. As shown in FIGURE 2, the grinding wheel 26 a is on a vertical shaft 32 mounted in an arm 34 which can swing about a vertical post 36 under the control of adjusting mechanism 38 which acts between a housing 40 fixed to the carriage 24 and two lugs 42 fixed to the arm 34. The grinding wheel is exposed towards the drum 10, but is otherwise enclosed within a housing 44 which is supported from the carriage 24 by pillars 46. The primary function of the mechanism 38 is to shift the grinding wheel gradually rearwards (i.e., to the left in FIGURE 1 to make up for the gradual wearing away of the grinding wheel.

The carriage 24 is reciprocated by mechanism shown in FIGURES 1, 2 and 3, housed within the main beam 18. This consists of a slot 47 in the carriage, engaged by a follower roller 48 projecting from a chain 50 which has two runs parallel to the path of the carriage and which passes round a large driving wheel 52 at one end and two small wheels 54 at the other end. It will be seen that, while the follower 48 is moving vertically between the two small wheels 54, there will be a dwell in the motion of the carriage. During this dwell the grinding wheel will lie in alignment with a dressing unit 56 at the right hand end in FIGURE 2.

This dressing unit, as shown in FIGURES 1, 2 and 7, consists of a diamond 58 mounted on an arm 60 which is pivoted around a sleeve 62. This sleeve 62 is eccentric, and is itself mounted coaxially with the rotary cutter 10, by being journalled on a fixed bush 64 surrounding the cutter shaft 12. The normal position of the diamond 58 is just below the level of the bottom of the grinding wheel 26. Each time the grinding wheel reaches the dwell point, the diamond is automatically swung upwards across the face of the grinding wheel by mechanism shown in FIG- URES 1 and 2.

As shown in FIGURE 2, two levers 68 and 70 are pivoted to the main beam, and connected by a link 72 which also carries a cam 74. As shown in FIGURE 3, the follower roller 48 is associated with a second follower roller 76, and, as this roller 76 moves downwards between the wheels 54, it strikes the cam 74 and displaces it to the right, as seen in FIGURE 2. This movement is transmitted by a rod 78, acting against a spring 80, to a bellcrank 82, and thence by a link 84 to the arm 60 carrying the diamond (see FIGURE 1). When the grinding wheel commences its next movement to the left, as seen in FIG- URE 2, the diamond returns to its normal position.

Just as the grinding wheel reaches the dwell point, it is moved slightly to the left, as seen in FIGURES 1 and 4, by the mechanism shown in FIGURES 4 and 5. As the carriage 24 reaches the dwell point, an abutment 86 on an arm 88 strikes a fixed abutment 90'. The arm 88 is fixed to a shaft 92, and is normally held in the position shown in chain lines in FIGURE by means of a torsion spring 93 (FIGURE 4). The shaft 92 carries two pawls 94 which cooperate with two ratchet wheels 96 and 98. The ratchet wheel 96 has one tooth less than the ratchet wheel 98. The wheel 96 is screw threaded on to an axle 100, and the wheel 98 is mounted integrally on a sleeve which is keyed to the axle at 102. The position of the ratchet wheel 96 is fixed axially, so that when both ratchet wheels are rotated through one tooth interval, by means of the pawls 94, the axle 100 is moved to the left in FIGURE 4 by a small amount which corresponds to the difference in angular pitch of the teeth of the ratchet wheels, and which also depends on the pitch of the screw.

At the end of each stroke of reciprocation of the carriage, the knives 8, which are flat, are each fed in the direction of their own plane, so as to project slightly further from the drum, and thus make up for wear, and also provide a small amount of material to be ground away during the next reciprocation of the grinding wheel, and thereby present a fresh sharp edge. For example, the feed mechanism may, as indicated in FIGURE 1, include a pneumatic cylinder 104 associated with each knife, the cylinders being supplied with a pulse of air through a central passage 106 each time the carriage 24 concludes a stroke.

Before the machine is put into continual use, the following initial adjustments are made. First the knives 8 are set so that they project from the cutter a desired amount, i.e. so that they sweep out a cylinder path having a desired small clearance from the front of the mouthpiece 6. The cutter and the grinding wheel are then set in rotation, and with the carriage stationary, the grinding wheel is fed forwards by hand towards the cutter until grinding commences, and is occurring throughout the depth of the rim of the wheel. This will mean that, as shown in FIGURE 7, the knives, which move upwards past the grinding wheel, will approach the grinding wheel with edges at a radius A from the cutter axis X, and will leave the grinding wheel with their edges at a slightly smaller radius B from the axis X. To achieve this action progressively, the profile of the grinding wheel should be an arc struck from a centre somewhat below the axis X. How this situation is maintained will be described below.

The feeding forward of the grinding wheel during this initial setting is carried out as shown in FIGURES 4 and 6. That is to say, the abutment 86 is swung downwards so that the arm 88 swings further to the left than its normal position. This carries the pawls 94 out of engagement with the ratchet wheels 96 and 98, and at the same time brings a locking pawl 108 into engagement with the ratchet wheel 96 only. The sleeve which is keyed to the shaft may then be rotated by a hand wheel 110, producing a relatively rapid feeding movement of the grinding wheel. At the conclusion of this, the arm 88 is pulled to the right in FIGURE 6, and the abutment 86 is restored to its normal position.

The carriage is then run to its dwell point, so that the grinding wheel is abreast of the dresser, and the arm of the dresser is swung manually upwards. Adjustments are made both by angular movement of the eccentric sleeve 62 and by radial adjustment of the diamond 58 relative to the arm 60, by means of a screw thread and locking nuts 112. Movement of the sleeve 62 (which can then be locked to the bush 64 by means not shown) causes the pivot axis Y of the diamond 58 to rotate around the cutter axis X. Adjustment at 112 changes the radius from the diamond 58 to the pivot axis Y. By a combination of these adjustments, the diamond is caused just to contact the grinding wheel throughout the depth of the face of the grinding wheel. That is to say the diamond travels through the are necessary to maintain the profile of the grinding wheel which gives the progressive knife sharpening action described above. No further adjustment of the eccentric sleeve 62 should then be required.

To provide a check on any wear of the diamond 58, the diamond is then swung by hand to an upright position indicated at 114, and an adjustable screw 116 in a bracket fixed to the upright 14 is turned until it just touches the diamond. This then provides a datum against which the diamond can be checked from time to time. If the diamond should become worn, then it may be brought back into contact with this datum by the adjustment 112.

The machine can then be put into continuous use.

It will be found that the optimum position of the axis Y about which the diamond pivots is slightly below and forward from the axis X of the cutter.

I claim:

1. In a machine having a rotary cutter rotating about an axis and having one or more knives with cutting edges lying in a cylindrical surface, means for sharpening said rotary cutter comprising a disc grinding wheel mounted for rotation about an axis substantially perpendicular to a plane containing the axis of the rotary cutter, the rim of the grinding wheel being hollowed to match the cylindrical surface, a carriage on which the grinding wheel is mounted and which is arranged to reciprocate along the full length of the cutting edges parallel to the axis of the cutter and to dwell at one end of its reciprocating movement, and a dresser for maintaining the contour of the hollowed rim of the grinding wheel, mounted on an arm which is pivoted about an axis parallel to, adjacent to, and adjustable with respect to, the axis of the rotary cutter at the end of the cutter at which the carriage dwells.

2. A machine according to claim 1, in which the dresser is a diamond, which is mounted on the end of an arm whose other end is pivotally mounted on an eccentric sleeve, which is itself mounted coaxially with the rotary cutter.

3. A machine according to claim 2 including means for adjusting the angular position of the sleeve, and means for adjusting the effective radius of the dresser tip.

4. A machine according to claim 1, further comprising means for automatically swinging said dresser across the face of the grinding wheel each time the grinding wheel reaches the dwell point.

5. A machine according to claim 1, in which the axis of the rotary cutter is horizontal, further comprising means for driving the rotary cutter in the sense that the cutting edges move upwards past the grinding wheel, the pivot axis of the dresser being slightly below the axis of the cutter, so that the grinding wheel has a progressive action on each knife as it passes.

6. A machine according to claim 1, in which the motion of reciprocation and dwell is imparted to the carriage by a slot on the carriage engaged by a follower projecting from a chain which has two runs parallel to the path of the carriage and which passes round one large wheel at one end of the runs and two small wheels at the other end.

7. A machine according to claim 1, further comprising difierential screw and ratchet means for automatically feeding said grinding wheel toward the cutter each time said grinding wheel reaches the dwell point.

References Cited UNITED STATES PATENTS 2,121,879 6/1938 Lorentz 5l249 2,327,272 8/1943 Jones 1 125-41 2,476,177 7/1949 Bloom 146l17 2,479,101 8/1949 Dahl 12511 2,738,629 3/1956 Schreiber 51249 2,830,634 4/1958 Pollrnan 51-249 X ROBERT C. RIORDON, Primary Examiner. LESTER M. SWINGLE, D. G. KELLY,

Assistant Examiners

Claims (1)

1. IN A MACHINE HAVING A ROTARY CUTTER ROTATING ABOUT AN AXIS AND HAVING ONE OR MORE KNIVES WITH CUTTING EDGES LYING IN CYLINDRICAL SURFACE, MEANS FOR SHARPENING SAID ROTARY CUTTER COMPRISING A DISC GRINDING WHEEL MOUNTED FOR ROTATION ABOUT AN AXIS SUBSTANTIALLY PERPENDICULAR TO A PLANE CONTAINING THE AXIS OF THE ROTARY CUTTER, THE RIM OF THE GRINDING WHEEL BEING HOLLOWED TO MATCH THE CYLINDRICAL SURFACE, A CARRIAGE ON WHICH THE GRINDING WHEEL IS MOUNTED AND WHICH IS ARRANGED TO RECIPROCATE ALONG THE FULL LENGTH OF THE CUTTING EDGES PARALLEL TO THE AXIS OF THE CUTTER AND TO DWELL AT ONE END OF ITS RECIPROCATING MOVEMENT, AND A DRESSER FOR MAINTAINING THE CONTOUR OF THE HOLLOWED RIM OF THE GRINDING WHEEL, MOUNTED ON AN ARM

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