Apparatus Providing Output Indication of Tobacco Rod Firmness

This invention relates to cigarette making machinery and more particularly to apparatus providing continuous output indication of the relative firmness of a tobacco rod during manufacture of cigarettes.

In monitoring the firmness of tobacco rods in cigarette manufacture, the industry has made extended use of compacimeters (compactness meters) whereby exacting "off-line" measurements can be made on manufactured cigarettes without intervention in the making process. In its further efforts to provide tobacco rod firmness information more contemporaneous with cigarette manufacture, thereby to enable adjustment or correction of the parameters of the making process concurrently with information gathering, the industry has looked further to various "on-line" systems and apparatus. Versions of pneumatic apparatus are shown in U.S. Pat. Nos. 3,411,513, 3,595,067, 3,633,590 and 3,850,029 and in British Pat. No. 1,372,056. These devices are (1) of type employing floating nozzles issuing pressurized air onto the cigarette wrapper and either measure deformation of the wrapper or displacement of the nozzle based on change in back pressure and (2) of type providing a pressurized on-line chamber arrangement and observing pressure changes caused by variation of firmness or dimensions of cigarettes passing therethrough.

Alternate, non-pneumatic approaches to firmness measurement are set forth in U.S. Pat. No. 2,667,172 and South African Patent Application No. 73/9394. The devices of the 2,667,172 patent and such patent application look toward the use of tobacco rod forming elements of existing maker machinery for the additional function of providing output indication of rod firmness. In the 2,667,172 patent, elongate short tongue 60 includes strain gages 116 and 116a positioned proximate its compression foot and distal from short tongue support clamp or beam 101. These gages are in spaced longitudinal alignment whereby longitudinal pressures exerted by tobacco against the tongue may be sensed. This sensing apparatus is separate in function and operation from the tobacco rod firmness sensing apparatus of the 2,667,172 patent. The latter apparatus comprises a single active strain gage 84, also disposed between the tongue support beam and foot and adapted to provide output indication of vertical strain placed on the short tongue, i.e., movements of its foot transverse to the direction of movement of tobacco engaged thereby. The South African patent application relates also to specially constructed short tongues, disclosing a first embodiment wherein the compression foot of a short tongue is split into two successive longitudinal sections, each having a separate support flange with one support flange having a strain gage thereon, and a further embodiment wherein the longitudinally forward of such compression foot sections is further split into three circumferential segments, each having an independent support flange with a strain gage thereon. Such support flanges are stems having one end terminating at the compression foot and an opposite end terminating at the tongue cantilever support beam.

It is an object of the present invention to provide simplified on-line tobacco rod firmness measuring apparatus.

In attaining the foregoing and other objects, the invention provides for the introduction of strain gage apparatus directly on the cantilever support beam of a short tongue, such apparatus preferably having plural strain gages respectively oppositely stressed upon movement of the short tongue foot radially of the tobacco rod engaged thereby to indicate change in firmness. The firmness indication provided in accordance with the invention may be further amplified by nominal modification of the support beam of existing short tongue of commercial equipment and still further by particular circuit interconnection of plural pairs of strain gages.

Pursuant to the invention, strain gages are located on the cantilever beam itself, an approach disparate from that of the referenced 2,667,172 patent and South African patent application which provide for strain gage placement beyond such beam, and necessitate specialized short tongue structure. In its attainment of firmness indication of accuracy commensurate with that of off-line apparatus, the invention detects change in the condition of flexure of such beam member responsive to compression foot movement.

The output stress change signals of the cantilever beam-supported strain gages may be employed to control a meter or like indicating instruments, may be recorded or may serve to control tobacco supply or like on-like apparatus.

The foregoing and other objects and features of the invention will be further understood from the following detailed description of preferred embodiments of the invention and from the drawings wherein like reference numerals identify like parts throughout.

FIG. 1 is a schematic illustration of cigarette making apparatus in present commercial use.

FIG. 2 is a perspective view of the short tongue of the FIG. 1 apparatus.

FIG. 3 is a further perspective view of the FIG. 2 short tongue adapted in accordance with the invention for tobacco rod firmness measuring.

FIG. 4 is a perspective view of the short tongue modified in accordance with the invention.

FIG. 5 is a partial plan view of the short tongue of FIG. 4 with plural strain gages employed in accordance with the invention.

FIG. 6 is a schematic side illustration of the FIG. 4 short tongue in its quiescent position.

FIG. 7 is an exaggerated illustration of the condition of flexure of the beam member of the FIG. 4 short tongue.

FIG. 8 shows a circuit for use in providing tobacco rod firmness indication.

FIG. 9 shows a further circuit arrangement wherein plural pairs of strain gages are employed.

Referring to FIG. 1, cigarette making apparatus, known as the MK8 Cigarette Maker and commercially-available from the Molins Company, is shown schematically to include tobacco chimney 10 from which tobacco is blown onto perforated vacuum belt 12 driven by rollers 14 and 16 to convey tobacco T supported by belt 12 to trimmer knife assembly 18 supported for movement toward or away from the conveyed tobacco to vary the amount of tobacco on belt 12 in accordance with a cigarette weight (density)-based control signal.

Leftwardly of roller 14, such Molins apparatus includes elongate garniture 20 defining an open channel extending longitudinally and of generally semi-cylindrical configuration. Endless garniture tape or belt 22 is fed to upstream tobacco input mouth 20a of the garniture and transported through the garniture by drive wheel 24 over idler rollers 24a-24e. Cigarette paper 26 is fed to mouth 20a atop tape 22 from supply roll or bobbin 28 over idler rollers 28a, 28b and 24d. Tobacco falls from belt 12 onto paper 26 as vacuum is removed from the belt. On entry of tape 22 in the garniture channel, the garniture imports generally semi-cylindrical shape thereto, like shape being thereby imparted to paper 26 and the tobacco deposited thereon from belt 12, the open semi-circular cross-section of the tape, paper and tobacco being shown in FIG. 6.

Short tongue 30 of such Molins apparatus (FIGS. 1 and 2), comprising compression foot 32 and cantilever beam member or arm 34, is located downstream of garniture mouth 20a. This unit is cooperative with the garniture to impart generally cylindrical form to the tobacco to form a tobacco rod. To this end, compression foot 32 defines an open channel extending longitudinally therein and also of generally semi-cylindrical configuration, the open semi-circular cross-section of such channel being shown in FIG. 6. One end of beam 34 is fixedly secured, as by bolt 36 to base 38 (FIG. 2) and the opposite end of beam 34 is integral, or otherwise in supporting relation, with stem 32a of compression foot 32.

As the formed tobacco rod leaves short tongue 30, a length of cigarette paper extends tangentially from the paper-wrapped rod. Paster wheel 40 applies an adhesive to such extending length of paper whereupon unit 42 folds such pasted length over and unit 44 heat seals the rod. The sealed continuous rod now passes through nuclear density gage 46 and is then cut by rod cut-off mechanism 48.

In FIG. 3, strain gages 50 and 52 are supported, in accordance with the invention, on opposed sides 34a and 34b of beam 34 at locations on the beam at which the beam exhibits flexure on movements upwardly from a quiescent position, i.e., a position wherein no upward stress is in the beam.

Strain gages 50 and 52 are preferably employed with a beam 34' (FIG. 4) which differs from beam 34 of FIG. 3 by inclusion of a longitudinal extent 34'a of reduced cross-sectional area with respect to portions 34'b and 34'c of beam 34' extending longitudinally adjacent such extent 34'a. In this construction, strain gage 50 is supported on land 34'f of beam extent 34'a and strain gage 52 is supported thereunder on land 34'g. Preferably, separate strain gages 50a and 50b are supported on land 34'f, as shown in FIG. 5. The underside opposed land supports strain gages 52a and 52b (not shown in FIG. 5).

In the aforesaid quiescent position for beam 34 or beam 34' compression foot 32 is thereby supported to engage a tobacco rod of substantially less diameter d than a predetermined desired diameter, as is shown schematically in FIG. 6, in such manner that the strain gages on opposed surfaces of the beam exhibit equal electrical resistance. Thus, in FIG. 6 tobacco rod R is of such predetermined diameter d and beam 34 is in such position that it is unflexed. FIG. 7 shows schematically and in exaggerated manner, a movement of beam 34' upwardly of its quiescent position, occasioned by foot 32 engaging a rod having diameter greater than diameter d, wherein flexure of beam 34' elongates land 34'g and contracts land 34'f. As a result, the strain gage(s) on land 34'g is subjected to tension while the strain gage(s) on land 34'f is subjected to compression. On movement of compression foot 32 and its support beam downwardly of its FIG. 7 position, as occurs when engaged tobacco rod firmness decreases from that applying in FIG. 7, compression in the strain gage(s) on land 34'g will increase while tension in the strain gage(s) on land 34'f will increase.

As will be appreciated, lands 34'f and 34'g experience greater surface extent change for a given flexure condition in beam 34' than longitudinally adjacent beam portions 34'b and 34'c. Accordingly, the beam construction shown in FIGS. 4-6 enables the strain gages to exhibit a change in resistance for a given beam flexure exceeding that resistance change which they would exhibit were they supported, as in the FIG. 3 embodiment, on surfaces of the beam not of reduced cross-sectional area.

Where used in the embodiment shown in FIG. 3 or the embodiments shown in FIGS. 4-6, a single pair of strain gages (50, 52) are connected in manner shown in FIG. 8, i.e., they are series-connected and supplied with voltage from a suitable power supply P.S. with an output signal being provided at terminals T1 and T2, indicative of the voltage across an exclusive one of the strain gages. By such connection of the single pair of strain gages, mounted in plural on the cantilever beam 34 or 34' and in manner exhibiting respectively opposite changes in stress condition for change in flexure condition of the beam, an amplified signal is obtained at terminals T1 and T2. Thus, if strain gage 50 is compressed, thereby decreasing its resistance, while strain gage 52 is subjected to tension at the same time, thereby increasing its resistance, the voltage across terminals T1 and T2 will increase in compound manner, i.e., increasing on one hand, by decrease in the resistance of strain gage 50 and, on the other hand, by increase in resistance of strain gage 52. As will be further seen, based on such signal amplification, less sensitivity to change is required in associated detector equipment, for example, rod firmness indicating meter M, and the signal-to-noise ratio may desirably be increased.

Where strain gages are employed in pairs on opposed sides of beam 34 or 34' as shown in FIG. 5, the gages are connected as in FIG. 9. A full bridge circuit includes one branch having gages 50a and 52a connected in series and another branch having gages 52b and 50b connected in series, the branches being connected in parallel between terminals T3 and T4. A power supply is connected across T3 and T4 and an output signal is provided by terminals T5 and T6, T5 being connected to the junction J1 of gages 50a and 52a and T6 to the junction J2 of gages 50b and 52b.

The reversed order of connection of strain gages in the FIG. 9 circuit provides signal amplification increased above that of FIG. 8. In such reversed order, one gage (50a) on the upper beam side is in the upper portion of the first branch and the remaining upper beam side gage (50b) is in the lower portion of the second branch. One gage (52b) on the lower beam side is in the upper portion of such second branch and the remaining lower beam side gage (52a) is in the lower portion of such first branch.

Assuming the change in flexure conditions in FIGS. 6 and 7 to be the tobacco rod firmness change under examination, the resistances of gages 50a and 50b will decrease and the resistances of gages 52a and 52b will increase. The voltage at junction J1 with respect to junction T4 will increase in magnitude and the voltage at junction J2 with respect to T4 will decrease in magnitude by that same amount. The voltage change between T5 and T6 will thus be twice that seen at either junction separately.

Considering beam 34' to be stable in its first flexure condition in FIG. 7 and tobacco rod firmness to then change such that the beam assumes a second flexure condition between its FIG. 7 and its FIG. 6 states, tension in the gage(s) on land 34'g decreases from that applying in the first flexure condition, i.e., relative compression thereof increases from that applying in the first flexure condition. Similarly, in the second flexure condition compression in the gage(s) on land 34'f decreases, i.e., relative tension increases therein. Otherwise stated, movement of foot 32 is accompanied by stress changes of opposite sense (compression vs. tension) in the respective top and bottom strain gage(s).

In practicing the invention, the strain gages are preferably foil strain gages, such as are commercially available as model number MA-06-062AA-120 (gage factor 2.075) from Micro-Measurements Division of Vishay Intertechnology, Inc., Box 306, Romulus, Michigan.

Various changes and modifications may be introduced in the foregoing particularly described embodiments without departing from the invention. Such embodiments are thus intended in a descriptive and not in a limiting sense. The true spirit and scope of the invention is set forth in the following claims.