US2535672A - Rotary tobacco cutting machine - Google Patents

Description

Dec. 26, 1950 E s 2,535,672

ROTARY TOBACCO CUTTING MACHINE Filed May 29, 1946 Patented Dec. 26, 1950 ROTARY TOBACCO CUTTING MACHINE George Dearsl'ey, London, England, assignor to Molins Machine Company Limited, London,

England Application May 29, 1946, Serial No. 672,959 In Great Britain June 4, 1945 1 Claim. 1

This invention concerns improvements in or relating to "rotary tobacco cutting machines.

United States Patent No. 1,933,181 discloses a rotary tobacco cutting machine in which the cutting blades are carried by a rotatable cutter head and are ground by a rotating grinding wheel over whose face they pass during their rotation, the blades being arranged to be fed forwardly to compensate for wear. Such a machine will for convenience be referred to as a tobacco cutting machine of the kind described. In machines made in accordance with the prior specification, the grinding wheel has hitherto been trimmed during operation of the machine by a diamond which is from time to time autom'atically reciprocated across the face of the grinding wheel, while the grinding wheel is arranged to be fed forwardly to compensate for wear. As is well known, the practice of trimming grindstones is to use the diamond as a cutting tool which "turns off a layer from the grinder surface. The speed of the diamond is very slow compared with the peripheral speed of the grindstone so that the stone is completely trimmed at one pass of the diamond. In tobacco cutting machines of the kind described, the method of trimming the grinder has followed standard practice, and the diamond is reciprocated across the annular face of the rotating grinding wheel at one side of the latter and at intervals of about i to 1 minutes in such a manner as to act in effect as a turning tool which turns a whole layer off the face of thewheel at one pass. 'Beforeeach such operation the grinding wheel is fed forwardly so that the diamond can turn down the annular grinding face so that when so trimmed the grinding face is in the desired plane.

Under these conditions it is found that the diamond becomes heated to a considerable degree, but owing to the relatively small surface area of the face of the grinding wheel used in this construction, the heating does not become excessive. In a madhifie Where a considerably larger grinding wheel is. used, however, there is.

a risk that heating of the dia ond may become xcessive. The a pli ation of a coolant to the iamond is undesirabie since it is difiicult to keep the resulting gritty liquid clear (if the tobacco.

According to the invention there is provided in a tobacco cutting machine or the kind described, means for trimming the race Of the grinding wheel comprising a diamond or the like mounted for rotation with the rotatable cutter head to. g. mounted on the cutter head) 2 and arranged to sweep across the face of the grinding wheel during rotation of the cutter head, the grinding wheel being arranged to be fed forwardly continuously to compensate for Wear.

A machine of the kind described, constructed in accordance with the invention, will be described by way of example with reference to the accompanying drawings in which-- Figure 1 is a front elevation of part of the machine showing the cutter head, mouth-pier3e and grinding wheel.

Figure 2 is a fragmentary view of Figure 1 looking in the direction of the arrow A, the grinding wheel being in section.

Figure 3 is a diagram showing a typical track of the diamond across the face of the wheel.

The drawings show such parts of the machine as are necessary for the understanding of the present invention and are drawn with particular reference to the trimming of the grinding wheel. The machine is generally similar to that disclosed in the complete specification of United States patent application Serial No. 644,- 133, and owing to the construction and arrangelnent of the knives, the grinding wheel employed is very much larger than that used in the construction shown in the prior Patent No.

1,933,181, the area of the grinding face in the present case being about five times as great as that of the grinding wheel previously used.

Referring to the drawings the cutter head I consists of a spider on which aremounted at equally spaced angles six blades 2 whose edges sweep across a mouth 3 (as shown in Figure 1).

.vide for cleaning of the stone by the trimming action, and at the same time to maintain the wheel always in the correct plane for grinding the cutting blades the desired amount.

The method of continuously feeding forwardly the grinding wheel 5 is the same as that disclosed in aforementioned United States Patent No. 1,933,181.

Thus in order to compensate for the wear of the grinding wheel due to the grinding of the blade and the truing of the wheel, the wheel is carried in a bearing mounted on a slide 3| which is automatically fed forward or toward the blade by a screw 32 rotated through gearing 33 shown in Figure 3 from the main drive of the machine.

A diamond l is mounted in a small bracket 6 fixed on the rotatable cutter head I, at such a distance from the axis of rotation 4 that on rotation of the head the diamond sweeps across the grinding face of the grinding wheel, once for each revolution of the head. As the wheel is tilted to the plane of the knives, contact between the diamond and the wheel occurs at the lower part of the wheel.

When the machine is in operation, with each revolution of the cutter head the diamond sweeps across the face of the grinding wheel and scores out a very shallow groove a typical track 8 being shown in Figure 3. The grinding wheel is itself rotating at a high speed, approximately 1,440 revolutions per minute. The cutter head and the grinding wheel are rotated by independent means, and the ratio between the speeds of their respective driving means is therefore unlikely to remain the same. This is particularly so, since the grinding wheel is driven by a pulley drive and slip is likely to occur during operation of the machine. Therefore there cannot be any exact predetermined relationship between the rates of revolution of the grinding wheel and of the cutter head. Because of this, the grooves are distributed quite at random around the face of the grinding Wheel. It is found that owing to this distribution and to the rapidity with which the cutter head rotates, namely about 150 revolutions per minute, and the very slow rate of forward movement of the grinder, the ultimate effect is that the face of the grinding wheel is kept constantly trimmed. The continuous forward feeding of the grinding wheel ensures that its grinding face is always in the correct plane.

In the arrangement described above, the cutter head and the grinding wheel are, as stated, rotated by independent means, and the relationship between their respective rates of revolution thus tends to vary. If, however, the machine is arranged so that the driving means for the grinding wheel and the cutter head are synchronised and so arranged as to provide a fixed relationship between their rates of revolution, this relationship should be so chosen as to ensure a thorough distribution and avoid a condition in which the diamond repeatedly sweeps across the face of the grinding wheel at a relatively small number of fixed positions so as eventually to cut out a number of deep grooves, due to the continuous forward feeding of the grinding wheel, while leaving the remainder of the face untouched.

The rate at which the grinding wheel is fed forward to compensate for wear is extremely low, approximately .0000? inch per minute. It will therefore be seen that if the cutter head rotates at 150 revolutions per minute, the diamond sweeps across the face of the grinding wheel 150 times while the latter is moving forward .0000'7 inch. Thus it will be seen that while the grinding wheel is travelling forward a minute distance, a very ,large number of shallow grooves are made on its surface, and this assists in providin a very wide distribution of the grooves and ensuring that the grooves are extremely shallow.

In machines made in accordance with prior Patent No. 1,933,181, the grinding wheel has been arranged to be fed forward towards the knives almost continuously, whilst the diamond makes a complete oscillation for trimming about once every minute. Thus, just before trimming, the grindstone in this prior arrangement is in a plane slightly in advanc of the theoretically correct position. This is corrected, in a relatively short time, by the diamond when it makes its oscillation and the face of the grindstone is cut back so that it lies in the desired plane, and thus a period of time elapses before the knives have been fed up to the newly trimmed face of the grinder. Thus the knives are not always in the same state of sharpness. Another varying factor in the prior arrangement is the state of the grindstone itself. After being trimmed, it is clean and sharp, so that when the knife is fed up to it, it is capable of grinding with maximum efficiency. Just before being trimmed, the cutting grains of the wheel are relatively worn and blunt, and generally the grindstone is also slightly loaded with tobacco juice, so that its grinding efficiency is impaired. Thus the conditions of grinding are not constant, both as regards position and efficiency of grinding.

In the arrangement accordin to the invention, the grinding wheel is fed forwardly continuously and the surface of the grinding wheel is also being scored by the diamond at a relatively fast rate; in fact the diamond crosses the stone as frequently as any one cutting blade. Thus, in contrast to the intermittent conditions described above, the arrangement accordin to the invention settles into a position of equilibrium, both as regards position and efficiency of grinding. It is believed that these constant conditions of knife grinding must produce more constant conditions in the cutting of the tobacco.

A further advantage afforded by the invention is that a considerable amount of mechanism is saved, and moreover it is possible to collect the product of the trimming of the grindin wheel in the same place as the product of the grinding of the cutting blades, thus making it unnecessary to provide two collecting points, as previously.

What I claim as my invention and desire to secure by Letters Patent is:

In a tobacco cutt ng machine, a rotatable cutterhead having a plurality of outwardly directed arms, a cutting blade mounted on each of said arms, each blade having a cutting edge extending substantially radially of the axis of the cutterhead, and being of substantial width, a mouthpiece for tobacco disposed in contiguous relation to the path of movement of sa d cutting blades, means operably connected to the cutterhead to rotate the cutterhead continuously so as to cause each cutting blade to sweep past the mouthpiece and cut tobacco once on each revolution of the cutterhead, a grinding wheel, means supporting said grinding wheel for rotation on a fixed axis substantially parallel to the axis of rotation of said cutterhead, and for axial displacement on said fixed axis, said grindin wheel having an annular grinding face defining a plane perpendicular to the axis of rotation of the grinding wheel and in contiguous relation to the path of movement of said cutting blades, whereby each blade is engaged and sharpened by said wheel once .on each revolution of the cutterhead durin operation of the machine to cut tobacco, and after each cutting operation, means operatively connected to said grinding wheel to rotate said grinding wheel on its axis of rotation, speed reduction gearing operatively connecting the supporting means for said grindin wheel with the means for rotating the cutterhead to slowly and continuously advance said wheel in timed relation with the rotation of said cutterhead toward the path swept out by the cutting edges of said cut-- ting blades, and a pointed trimming tool mounted on one of said arms and so positioned that the 5 point thereof engages with and sweeps across the grinding face of the grinding wheel on each rotation of the cutterhead and after each sharpening operation performed on the said cutting blades. GEORGE DEARSLEY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,781,674 Ashworth Nov. 18, 1930 1,933,181 Molins et al Oct. 31, 1933 2,109,600 Vanderbeck Mar. 1, 1938 2,222,580 Bergfeldt Nov. 19, 1940

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