US3258881A - Grinders for knives of cigarettemachine cut-offs - Google Patents

Description

y 5, 1956 J. A. MASON ETAL 3,258,881

GRINDERS FOR KNIVES OF CIGARETTE-MACHINE CUT-QFFS Filed Feb. 25, 1964 4 Sheets-Sheet 1 July 5, 1965 J. A. MASON ETAL GRINDERS FOR KNIVES OF CIGARETTE-MACHINE CUT-OFFS 4 Sheets-Sheet 2 Filed Feb. 25, 1964 July 5, 1966 J. A. MASON ETAL 3,258,831

GRINDERS FOR KNIVES OF CIGARETTE-MACHINE CUT-OFFS Filed Feb. 25, 1964' 4 Sheets-Shet 5 July 5, 1966 J. A. MASON ETAL 3,258,881

GRINDERS FOR KNIVES OF CIGARETTE-MACHINE CUT-OFFS 4 Sheets-Sheet 4 Filed Feb. 25, 1964 ,ZI/VEK/rfl5 United States Patent 3,258,881 GRINDERS FOR KNIVES 0F CIGARETTE- MACHINE CUT-OFF S James Arthur Mason and Barry George Applegate, both of Deptford, London, England, assiguors to The Molins Organisation Limited, a British company Filed Feb. 25, 1964, Ser. No. 347,264 Claims priority, application Great Britain, Mar. 14, 1963,

,157/63 1 Claim. (Cl. 51249) This invention concerns improvements in grinders for knives of cigarette machine cut-offs, and more particularly a grinding device for a knife whose cutting edge is eccentric to the axis of rotation of the cut-off and is also shaped to substantially helical form.

As is well known, the knife of a cut-off 'for a continuous-rod cigarette-making machine needs three-motions, or their equivalent, to cut through the rod. The knife must rotate to provide a cutting action, it must move into and through the rod, and it must also move at the same speed as the rod while cutting. A knife of the kind referred to provides for two of these motions by its shape and thus the cut-off can operate by simple rotation and there is no theoretical limit to its speed.

Knives of this kind have been known for a long time but have never come into such practical use because of the difficulty of sharpening them, as, for effective operation, a knife for cutting cigarette and like rods usually needs to contact a grinding device at every revolution of the cut-off. The grinding device about to be described satisfies this requirement.

According to the invention there is provided a grinding device fora cigarette machine cut-off of the kind having a knife whose cutting edge is eccentric to the axis of rotation of the cut-off and is also shaped to substantially helical form, comprising a grinding member rotatable about an axis located in the same plane as the cut-off axis, and having an abrasive surface which is eccentric to the axis of rotation of the member, said eccentric abrasive surface being shaped to engage a passing knife throughout the transit of the knife past the grinding member and grind a chamfer on the adjacent side of the knife, terminating in a sharp cutting edge, and means for rotating the member in timed relationship with the cut-off and in such direction that the member and knife move in opposite directions when in contact and the eccentric abrasive surface mates with the helical and eccentric edge of the knife during the transit of the knife past the grinding member.

The grinding member may be of plate-like form and the abrasive surface is conveniently formed on a lobe projecting from the member and having an edge which is eccentric to the axis of rotation of the member.

The lobe may have an abrasive surface which is inclined to the axis of rotation of the member, so as to grind the chamfer on the knife edge, and, in this case, the axis of rotation of the member is at right angles to the axis of rotation of the cut-off.

To spread the wear, due to grinding, over the abrasive face of a lobe, means may be provided for moving the grinding plate to and fro along its axis of rotation which, in this case, is at an angle of less than 90 to the axis of rotation of the cut-off and the abrasive face of the lobe is parallel to the axis of rotation of the plate. The axis is tilted with respect to the axis of rotation of the cut-off at an angle suitable to obtain the desired chamfer on the knife edge.

Normally two lobes, 180 apart, are provided for the sake of balancing the rotating plate. These can either be used at alternate revolutions, in which case the plate is geared to the cut-off by 1:2 gearing, or one lobe can be used with 1:1 gearing, until its abrasive face is worn out, after which the plate is turned through on its shaft to bring the other lobe into use.

The invention will be further described with reference to the accompanying drawings in which:

FIGURE 1 is a perspective view of a portion of a cigarette machine cut-off, showing its knife just beginning to contact a grinding device,

FIGURE 2 is a fragment of FIGURE 1, showing the knife and grinding device in a position the parts occupy after the knife has advanced somewhat in its movements from the position shown in FIGURE 1,

FIGURE 3 is .a view similar to FIGURE 2, but shows the knife and grinding device just as the heel of the knife is leaving the grinding device,

FIGURE 4 is a fragmentary view, looking substantially in the direction of the arrow A, FIGURE 1,

FIGURE 5 is a plan of detail,

FIGURE 6 is a sectional elevation of FIGURE 5,

FIGURE 7 is a diagrammatic plan of driving arrangements of a modified construction, partly in section,

FIGURE 8 is a front elevation of FIGURE 7.

Referring to FIGURES 1 to 4 of the drawings, a continuously rotating disc 1 has a knife clamp arrangement 2 fixed to it in which a knife 3 is fixed. The disc 1 is fixed on a shaft 9, driven in any suitable way from the cigarette-making machine. The shape of the knife can be seen from the drawings and it will be seen from FIG- URE 4 that its cutting edge is eccentric to the axis of revolution of the disc 1. Also, as can be best seen from FIGURE 3, the blade has a twist and it is substantially a helix. A rotatable grinding device 4 consists of a flat plate 5 with two opposed lobes 6. It is mounted on a shaft 10 and is driven from the shaft 9, at half the speed of the disc 1, by bevel gear wheels 29 and 30, so that each lobe in turn contacts withthe knife. The operative face of each lobe is at an angle to the plane of rotation of the device 4 so that the knife has a chamfer ground on it.

Across the operative face of each lobe is a band 7 of abrasive material, such as diamond dust, bonded to the surface, and this is shaped, as shown, in the interests of economy and is just wide enough to ensure that every point on the cutting edge of the knife contacts with the abrasive surface, see FIGURE 4.

The direction of rotation of the plate 5 is shown by an arrow in FIGURE 1 and it will be seen that, at the point of contact, a lobe 6 is travelling in the opposite direction to the knife 3.

Referring now to FIGURES 5 and 6, the lobes 6 are eccentric to the axis of rotation of the plate 5 and the operative surface of a lobe is at an angle to the plane of said plate. In FIGURE 6 the angle 8 is substantially 30. The eccentric shape of the lobes wa arrived at by making a plate substantially of the shape shown, by geometrical construction involving finding the contact points for knife and lobe at different angular positions, and then mounting the plate, and a knife of the desired eccentric shape, and rotating them and noting the contact. It was found that a slightly modified lobe shape could be obtained in which the eccentric edge of a lobe was a circular arc of radius R, with a centre at Z, FIGURE 5. Since it is easy to machine a circular are this shape was adopted, with an immaterial change in the eccentric edge of the knife, the ground edge being slightly flattened at one part.

In FIGURE 1, a piece of cigarette rod is shown at C, with the knife 3 shown in chain lines in the cutting position. The cigarette rod travels horizontally and the shaft 9 is tilted to such an angle that the portion of the knife in contact with the rod, at any instant during the cutting operation, is normal to the rod axis.

As is known, to those skilled in the art, a cut-off re quires three motions to cut a cigarette rod satisfactorily.

3 The knife must rotate about an axis, and must cut into and through the rod, and it must have a traversing movement substantially equal to the rod speed. The second two motions are achieved by the eccentricity of the knife edge, and the helical twist respectively.

If it is desired to use only one lobe 6 at a time, until its abrasive surface is worn out, the bevel gear wheels 29 and 30 are changed for a pair of even ratio.

In FIGURE 1, the axes of the shafts 9 and 10 are in the same plane and at right angles to one another and so the operative face of each lobe is at an angle to the plane of rotation of the plate 5, so as to grind the desired chamfer on the knife, but a different arrangement is shown in FIGURES 7 and 8. Moreover, in FIGURE 1 the knife always passes across the same area of the abrasive strip 7 and to distribute the wear, due to grinding, over the face of an abrasive strip, means are shown in FIGURES 7 and 8 for axially oscillating the grinding member. I

Referring now to FIGURES 7 and 8, a shaft 11, driven for example, by a gear wheel 12, which is itself driven by any suitable means, is geared to the cut-off by a gear wheel 13 fixed to the shaft, which gear wheel mates with an equal gear wheel 14 on a short shaft 15. A mitre gear wheel 16 on this shaft drives another mitre gear wheel 17 on a shaft 18 to which the disc 1 is fixed.

If the cigarette length is changed, the cut-off runs faster for a shorter length and slower for a longer length, the rod speed remaining constant. The traverse of the knife during the actual cutting time needs to be altered accordingly and, if the change in length is not very much, the tilt of the shaft 9 of FIGURE 1, or the shaft 18 of FIGURE 8 can be altered a little, and a satisfactory cut is possible. For this purpose, in FIGURE 8, the axis of the shaft 18 is arranged to be angularly movable about a line drawn through the mid-width of the knife, normal to the axis 18, and intersecting said axis. The axis of shaft 11 is arranged to coincide with this line. The gearing mentioned is enclosed in a housing 19 and, when it is desired to alter the inclination of shaft 18, the whole housing is rotated about the axis of the shaft 11.

The plate 5 can be oscillated axially to distribute wear over the abrasive strip. For this purpose the grinding faces of the lobes on the plate are parallel to the axis of rotation and therefore the plate in FIGURE 8 is marked 50. In this figure, a cam 20 on the shaft 18 engages a roller 21 on an arm 22 of a bell-crank lever pivoted at 23. The other arm 27 of the bell crank is forked and works in a groove 24 attached to the plate 50 so that bell-ErEnk movements move the plate up and down on a shaft 25 to which it is splined. The angle of inclination of the shaft 25, which is in the same plane as the shaft 18 of the cut-off, is such that as the surface on plate 50 moves up and down it always contacts with thechamfer on the knife edge. The shaft 25 has a bevel gear wheel 26 fixed to it which engages another bevel gear wheel 28, having half the number of teeth, and mounted on the shaft 15. The plate 50 makes one revolution while the cutter disc 1 makes two but as in the earlier construction, the plate and disc could rotate at the same speed.

The knife 3 may be automatically fed out in any known manner from the axis of disc 1 to compensate 'for wear due to grinding. An example of such an arrangement is shown in co-pending Serial No. 159,208 filed December 14, 1961.

It was explained earlier that the axes of shafts 9 or 18 were angularly movable to suit the cutting of cigarettes of slightly differing lengths. In order to increase the scope of utility of the cut-off, the disc 1 may be arranged to carry different interchangeable knife clamps. Each such clamp would hold a knife at a different helix angle. If a knife is very thin it may be made fiat and twisted to the helix by shaped clamps. A thicker knife needs to be made to helical shape. Accordingly the necessary change parts may be clamps or clamps and knives. For instance, change parts can be made to cater for cigarette lengths in ranges of, say, 50 to 55 mm.- 56 to 60 mm. 61 to 65 mm.-66 to 70 mm. and so on. The angular variation necessary for satisfactory cutting between these various limits is negligible and is easily accommodated by altering the angle of the cut-off shaft.

Where the disc 1 is modified in this manner, each set of interchangeable parts will also comprise a knife-feeding device as stated above as a matter of convenience.

- by Letters Patent is:

In a cigarette machine cut-ofl mechanism having a knife rotatable about a first axis, the knife being of substantially helical form about the first axis and having a cutting edge eccentric to the first axis, a grinding member of plate-like form rotatable about a second axis coplanar withthe first axis, the grinding member having at least one lobe projecting therefrom which has an abrasive end face parallel with the second axis, means for rotating the grinding member in timed relationship with the rotation of the knife and in the opposite direction to grind the knife, the second axis being at an angle of less than to the first axis in order to grind a chamfer on the cutting edge of the knife, and the abrasive end face being eccentric to the second axis and shaped to engage the cutting edge of the knife throughout the transit of the knife past the grinding member to grind the chamfer on the adjacent side of the knife and terminating in a sharp cutting edge eccentric to the first axis, and means for axially reciprocating the grinding member on the second axis to distribute the wear on the ztbrasive end face, due to grinding, over the abrasive end ace.

References Cited by the Examiner UNITED STATES PATENTS 1,573,616 2/1926 Koerner 51-247 2,022,569 11/1935 Molins 51-247 2,026,096 12/ 1935 Muhlbauer 51-247 I 2,028,681 l/ 1936 Molins 51-247 2,035,563 3/1936 Molins et al. 51247 X 2,297,468 9/1942 Graupner 83174 X FOREIGN PATENTS 459,128 12/1936 Great Britain.

ROBERT C. RIORDON, Primary Examiner.

I. A. MATHEWS, Assistant Examiner.

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