US2757675A

US2757675A - Devices for guiding cigarette rods

Info

Publication number: US2757675A
Application number: US450940A
Authority: US
Inventors: Powell Gordon Franc Wellington
Original assignee: Molins Machine Co Ltd
Current assignee: Molins Machine Co Ltd
Priority date: 1953-08-19
Filing date: 1954-08-19
Publication date: 1956-08-07
Anticipated expiration: 1973-08-07

Description

Aug, 7, 1956 G. 'F. w. POWELL 2,757,675

DEVICES FORGUIDING CIGARETTE RODS Filed Aug. 19, 1954 2 Sheets-Sheet 1 Fig .1.

INVENTOR 1W 7' BY mZ 7 ATTORNE Y5 g 1956 v G. w. POWELL 2,757,675

DEVICES FOR GUIDING CIGARETTE RODS Filed Aug. 19, 1954 28heets-Sheet 2 INVENTOR BY WM ATTORN E Y5 nited States Patent DEVICES FOR GUIDING CIGARETTE RODS Gordon Francis Wellington Powell, Deptford, London,

England, assignor to Molins Machine Company Limited, London, England, a British company Application August 19, 1954, Serial No. 450,940

Claims priority, application Great Britain August 19, 1953 '11 Claims. (.Cl. 13180) This invention concerns improvements in devices for guiding cigarette rods while they are subjected to rays from a radio-active source for the purpose of measuring their mass.

In United States Patent No. 2,704,079, to Molins et al. issued March 15, 1955, there are described and illustrated guides for a cigarette rod which control the rod at a position where its mass is measured by a detector employing a radio-active source of penetrative radiation, in that case, a beta ray device.

For reasons set out in detail below it is essential, if the measurement is to be accurate, that the rod should be as nearly as possible of constant shape. That is, ideally the cross-section should not vary either in area or in actual shape. Otherwise the difference in presentation of the rod material to the detector will cause different results in measurement although, in fact, the same quantity of material is there. It Will of course be understood by those skilled in the art that a cigarette rod cannot be mathematicaly accurate and constant in either shape or size; the point is that every attempt must be made to secure the very best possible uniformity in these factors in order to eifect measurement under consistent conditions.

In order then to secure constant presentation of the rod there are a number of factors to be considered and difliculties to be overcome which will be explained before the nature of the invention is stated precisely.

For example, in a round, nominally cylindrical, cigarette rod, as produced by a continuous rod cigarette making machine, there are often found to be small variations in the diameter of the rod along its length. Also there are variations in the shape, that is, it is sometimes farther from a truly circular section than at others. Such variations are partly due to causes inherent in a cigaret machine, but they may be aggravated by imperfect adjustments of, for example, the garniture or the rod heater. In short, the cross-section is not uniform throughout, that is, the section is likely to change over a period of time. Variations in cross-section are also found at times in rods of other sections. The term oval is used later in respect of some sections, to mean, as is usual in the trade, substantially elliptical sections.

The purpose of the above-mentioned guides is to guide the rod, so far as is possible, in a fixed path so as to present a rod to a scanning unit, such as a beta ray device, in such manner that the presentation is constant, so far as is practicable. If then the rod itself suifers from random variations in shape and section it may well happen that a false reading is obtained from the scanning unit, even if the passing mass is correct, simply because the shape presented has changed.

It will be apparent that as the rod has to pass through the guides, being, in the specification referred to, thrust through them by the endless conveyor band which forms the rod on a cigarette making machine, the guides .cannot always be a really close fit on a rod suffering from Patented Aug. 7, 1956 such variations. Because of these difliculties, the response of the detecting device may be caused to change over a period of time, even though a constant mass of rod per unit length may be passing.

With the guiding arrangements described in the specification referred to the more central part or slice of the rod is scanned, this phrase being subject to limitations referred to at the end of the paragraph. The absorption of such part is much greater than that of the zones more remote from the central part and therefore the contribution to a change in the output from the detecting device consequent on a change in the mass per unit length of the rod will vary with any change in shape or section of the rod. In this instance also the term more central part or slice of the rod is scanned needs to be appreciated by one skilled in the art of these radio-active devices. In practice you cannot really consider individual slices because the beta particles do not travel in straight lines but pursue very tortuous paths through material and air, and therefore, what happens in the side or central slices is dependent on the adjacent materials. Further there are efiects due to back-scattering of particles which occurs at the surfaces of the guides and the extent of this phenomenon depends on the atomic weight of the materials used. These remarks must be borne in mind when the quoted phrase is considered and when reference is made to guides arranged to restrict the path of the rays to a particular slice of the rod.

The consideration of the relative absorption of the various parts of the rod will now be set out in more detail.

The rays are directed in a path nominally parallel to a diameter of the rod and with a ray source of low particle enegry scarcely any particles get through the central zone of the rod but penetration through the more remote parts from said diameter is very much higher since the effective mass per unit area is less and the penetration is by no means in direct proportion to the effective mass, for instance, a zone half the length of the full diameter may give as much as twenty times the ionization current that results from full diameter penetration.

Again an air gap of the same normal cross-section as the rod exposed by the guides would give a current twenty times that of the zone which is half the length of the diameter and four hundred times that of the central zone. It will therefore be appreciated that it is of great importance to avoid any air gap and it is further necessary to present a constant zone of the rod in the ray path. Thus it is highly desirable to avoid the need for any working clearance in the guides. Probably for the best results it is desirable to present the complete rod to the ray action, provided any air gap is avoided. For instance, suppose there is a change in the mass of the rod, which is not shielded from the rays, the difierence in the current generated will be largely due to penetration through parts beyond the central zone. It is of course desirable to have the greatest possible current change for mass variation in order to secure accurate regulation of the machine and thus by exposing the complete rod this result is secured.

Therefore if you wish to measure mass accurately it is first necessary to ensure that the rod presented to the scanning device is of proper shape and section, that the presentation is constant and that air gaps are avoided.

Shape and section may be controlled either by providing a close fitting guide, suitably arranged for the rod to pass through without damage, or by deliberately deforming the rod, as made, to a shape conforming to that defined by the guides. In both cases the guides are. a sufficiently close fit on the rod to avoid air gaps and in practice this means the guides exert a slight squeezing or deforming pressure on the rod. As there will naturally be considerable friction on the guides under such circumstances they may be made of hard materials such as chrome-steel, or ceramic material.

It will also be seen that for constant presentation the distances between source and rod, and rod and ray-responsive means must also be kept as constant as possible. The close fitting guide mentioned will of course be rigidly fixed to assist in keeping the distances correct.

From the foregoing explanation it will be seen that there are two main requirements to be satisfied. The rod shape must be as good and uniform as possible and the guides must fit the rod as snugly as possible so that it cannot wander. This latter requirement calls for some device for pulling the rod through the guides instead of pushing it, as in the case of the specification referred to.

According to the present invention there is provided in a continuous rod cigarette making machine, a scanning device comprising a radioactive source of penetrative radiation and a ray-responsive device, and a device for guiding the cigarette rod between the said source and rayresponsive device comprising guides which expose a part at least of the rod to the rays, and have cigarette rod engaging surfaces which engage the rod on opposite sides, the spacing between said surfaces as measured in planes containing the rod axis, being slightly less than the normal diameter of the rod, whereby the rod is subjected by said surfaces to a slight deforming pressure to minimize air gaps, and means for drawing the rod through said guides.

The guides may be arranged to restrict the path of the rays to a zone of the rod parallel to the longitudinal axis of the rod (for example, the rays are restricted to a central zone) and means may be provided for shaping the rod to a predetermined cross section at the entry to the guides and, if desired, means for shaping the rod to another predetermined cross-section at the exit from the guides.

For example the first said means may shape the rod to a circular cross-section of given diameter, in which case the second said means is not required.

The first said means may be arranged to deform a cylindrical rod to an oval cross-section in which case the second said means will be employed to reshape the deformed rod to a circular cross-section. Preferably, with such a device the parts will be arranged so that the major axis of the oval is at right angles to the ray path, that is, the axis is parallel to the face of the ray emitter.

The means for shaping and reshaping the rod may comprise rollers with grooved rims, for example, rims of concave cross-section. Although, as remarked above, the second rod-shaping means is not required for a cylindrical rod, which is only sized" by the first said means, it may be desirable to employ suitable rollers at the exit from the guides to assist in moving the rod through them.

The device may comprise rigid guides and moving means interposed between guides and rod to assist in the movement of the rod through the guides, The moving means may be provided by endless conveyors made, for example, as metal tapes.

The conveyors and the guides are so arranged as to squeeze the rod slightly to avoid any air gap, as far as possible, and they may move at the same linear speed as the rod.

Where curved guides, such as those in the patent referred to, are used the tapes may run in grooves formed in the curved guide surfaces.

Alternatively fiat guides with tapes in rubbing contact with their surfaces may be used in order that the full diameter of the cigarette is exposed to the rays so that resulting currents are more nearly a true measure of changes in the rod rnass. It will be observed that in this case the guides are really constituted by the cigarette engaging surfaces of the tapes.

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

Figure l is a side elevation of cigarette rod guides according to the invention and provided with conveyor tapes,

Figure 2 is a section of Figure l on the line 2-2,

Figure 3 is a section similar to Figure 3 showing a modified construction,

Figure 4 is a perspective view of the rod guides in combination with rod-shaping devices according to the invention,

Figure 5 is a section on the line 55 of Figure 4, also showing diagrammatically a ray source and ray-responsive means,

Figure 6 is a fragmentary section of Figure 4 on the line 66, and

Figure 7 is a fragmentary section of Figure 4 on the line 77.

Referring first to Figures 1 and 2, guides 1 and 2 are shown, generally similar to those illustrated in the specification referred to, but modified by shallow grooves 3 and 4 in their curved surfaces. The grooves are narrow and

steel tapes

5 and 6 are fitted in them, said tapes forming endless conveyors supported on

wheels

7 and 8 mounted at the ends of the guides. The conveyors are driven in the direction of the arrows so that the operative surfaces of the tapes travel through the guides at the linear speed of the rod. As the tapes are flat in cross-section and are arranged to compress the rod slightly to seal as far as possible any air gap it will be evident that the rod is slightly distorted from a truly circular section. As, how ever, this distortion is constant it will make no difference to the functioning of the Beta ray apparatus since this will still measure mass and the slight deformation will disappear as soon as the rod is free of the guides.

In Figure 3 the tapes run in shall grooves 3a and 4a in the guides 1a and 211, respectively, but in this case the guides themselves do not shroud the rod so that in this example the guides are really constituted by the tapes. So that the rod shall not wander laterally, suitable side control guides may be fitted to engage the rod at suitable positions outside of the part of the rod to be exposed to the detector. Such side control guides are shown diagrammatically at 14, Figure 3, by dotted rectangles. These guides are located outside of the part of the rod to be exposed to the detector. The particular shape of these guides forms no part of the present invention.

Referring now to Figures 4 to 7, at the entry to the guides, rod-shaping means is provided comprising at least one pair of rollers 10 whose rims are of concave crosssection. The rims are opposed to one another and the concavity is such as to present a through-way of substantially oval cross-section. The rollers are preferably positively driven and they squeeze or distort the rod to an oval cross-section, preferably with the major axis vertical. The major axis is preferably of such length that the rod will pass through the guides in rubbing contact therewith so as to avoid as far as possible, any air gaps. It will be appreciated that it is very difficult to shape a rod to exact shape and dimensions and the specification is to be read in the light of these known difficulties. However the more perfect the shaping, the more accurate the result of the measurements.

At the exit from the guides a further pair (at least) of grooved rollers 11 are provided whose axes are, for example, at right angles to those of the first pair. The rim of these rollers define a through-way substantially of the cross-section it is desired to give the finished rod, the rollers being arranged and adjusted to give, as near as may be, the correct section to the rod. Usually this cross-section will be the same as the initial cross-section though it could be slightly different in shape or size. These second rollers are positively driven and exert a tractive effect on the rod.

The

rollers

10 and 11 of Figure 4 may be used in combination with moving means such as the tapes shown in Figures 1 to 3, where it is found to be necessary to provide additional means to convey the rod through the guides.

With a vertical axis as illustrated, the section through which rays pass is fairly uniform and therefore the absorption is also fairly uniform and this may be desirable in the interests of sensitivity, see Figure 5 where 12 represents a ray source and 13 an ionization chamber.

What we claim as our invention and desire to secure by Letters Patent is:

1. In a continuous rod cigarette making machine, a scanning device comprising a radio-active source of penetrative radiation and a ray-responsive device, and a device for guiding the cigarette rod between the said source and ray-responsive device comprising guides which expose a part at least of the rod to the rays, and have cigarette rod engaging surfaces which engage the rod on opposite sides, the spacing between said surfaces as measured in planes containing the rod axis, being slightly less than the normal diameter of the rod, whereby the rod is subjected by said surfaces to a slight deforming pressure to minimize air gaps, and means for drawing the rod through said guides.

2. A device as claimed in claim 1 wherein the guides are arranged to restrict the path of the rays to a zone of the rod parallel to the longitudinal axis of the rod.

3. A device as claimed in claim 1 comprising means for shaping the rod to a predetermined cross-section at the entry to the guides.

4. A device as claimed in claim 1 comprising means for shaping the rod to a predetermined cross-section at the exit from the guides.

5. A device as claimed in claim 1 comprising means arranged at the entry to the guides to deform a cylindrical rod to an oval cross-section and means at the exit from the guides to reshape the deformed rod to a circular crosssection.

6. A device as claimed in claim 5 wherein the first said means is arranged so that the major axis of the resulting oval is at right angles to the path of rays from said radio-active source, that is, the axis is parallel to the face of the radio-active source.

7. A device as claimed in claim 5 wherein the means for deforming and reshaping the rod comprises rollers with rims, of concave cross-section.

8. In a continuous rod cigarette making machine, a scanning device comprising a radio-active source of penetrative radiation and a ray-responsive device, and a device for guiding the cigarette rod between the said source and ray-responsive device comprising guides which expose a part at least of the rod to the rays, and have cigarette rod engaging surfaces which engage the rod on opposite sides, the spacing between said surfaces as measured in planes containingthe rod axis, being slightly less than the normal diameter of the rod, whereby the rod is subjected by said surfaces to a slight deforming pressure to minimize air gaps, and means for drawing the rod through said guides comprising moving means interposed between said guides and said rod.

9. A device as claimed in claim 8 wherein the moving means consists of endless conveyors made, as metal tapes.

10. A device as claimed in claim 9 and having said guides curved to the shape of the contacting part of the rod and said guides having grooves therein in which the tapes are run.

11. A device as claimed in claim 9 comprising fiat guides with the tapes in rubbing contact with their surfaces.

References Cited in the file of this patent UNITED STATES PATENTS 472,101 Bohls Apr. 5, 1892 FOREIGN PATENTS 8,636 Great Britain 1899 587,210 Great Britain Apr. 17, 1947 670,422 Great Britain Apr. 16, 1952 684,503 Great Britain Dec. 17, 1952