US 3083887 A
Description (OCR text may contain errors)
April 2, 1963 w. F. HucK 3,083,887
WEB TENSION CONTROL MEcHANIsM Filed Jan. 12, 1961 BY )VM ATTORNEY United States Patent C) 3,083,887 WEB TENSION CONTRGL MECHANISM William F. Huck, 81 Greenway Terrace, Forest Hills, N.Y. Filed Jan. 12, 1961, Ser. No. 82,329 4 Claims. (Cl. 226-41) This invention relates to a device for controlling the tension of a moving web of paper, cloth, foil or other suitable material which is being processed in machines performing operations on the moving material.
The present invention is useful in many different types of machines through which a web may be fed in order to have a variety of different operations performed thereon, and has particular utility where it is necessary to positively drive the web at variable speeds while maintaining the web tension constant regardless of various disruptive iniluences, such as variations in press operating speed, variations in the absolute or specified numerical value of web tension, and changes in web temperature, web moisture content, humidity of the atmosphere surrounding the web, et cetera.
Prior to the present invention, it was the usual practice to control web tension, in Vsuch machines, by means of driving rollers which fed the web at a pre-selected ,surface speed slightly in excess of the linear web speed so as to provide the proper web tension, or `by means of lvariable speed driving rollers which were manually adjusted at frequent intervals in an attempt to maintain .constant web tension.
,the problem of maintaining correct web tension is an increasingly diflicult and important one.
Accordingly it is a primary object of the invention to Vprovide ,a unique mechanism for controlling, regulating fand maintaining the tension of a moving web substantially automatically, regardless of any variations in the speed of the moving web, or of the numerical value of the predetermined tension applied to the web, which value may readily be changed by the operator of the machine from time to time in a very simple and eflicient manner.
Another object of this invention is to improve the tensioning mechanisms of prior art devices, such as for example, those disclosed in my Patents No. 2,759,728, issued August 21, 1956; No. 2,787,463, issued April 2, 1957; and No. 2,949,295, issued August 16, 1960, by utilizing automatic web tension control means in which the automatic control of web tension is accomplished simply and economically with a minimum number of mechanical parts.
A further object of the present invention is to use a single floating roller of relatively little -mass to detect web tension variations, which results in a device which is much more sensitive to web tension variations and is much simpler and less expensive to construct than the devices heretofore used for this purpose.
An additional object of the invention is the provision of a unique adjustable piston and cylinder arrangement, with an associated dashpot, for precisely and instantaneously regulating the tension of the moving web.
Still another object is to provide a device of the aforesaid type which incorporates unique means for controlling tension in accordance with sensed web tension variations,
4comprising a fluid pressure piston and cylinder arrangement lhaving sensitive resilient operating characteristics provided by the use of a large fluid volume in the cylinder, which is quickly compressible and expandable under the sensed variations in web tension.
3,083,887 Patented Apr'. 2, 1963 ICC Still another object is to provide substantially frictionless motion between the piston and cylinder by virtue of a lubricating fluid film therein.
Another object of the invention is to provide means to select a predetermined pressure to be applied against the piston and to maintain this pressure, and the web tension dependent thereon, constant.
Yet another object of the invention is to provide, in combination with the above, a damping device comprising a double-acting piston sliding in a substantially frictionless fashion within a closed cylinder, and surrounded by a viscouse damping material, for effectively preventing over-correction of previously sensed web tension variation.
The way in which the new arrangement accomplishes these and other objects of the invention will become apparent upon consideration of the following detailed description of an exemplary embodiment of the invention, taken in conjunction with the `accompanying drawings illustrating such embodiment, and wherein:
FIGURE 1 is a partially diagrammatic side elevation view of the preferred form of the invention.
FIGURE 2 is a top plan view of the device illustrated in FIGURE 1.
Briefly stated, the device of the invention, as applied to a printing press of the type referred to above, maintains constant the tension of the web as the web is fed to and from the driving rollers about which the web is wrapped in an S curve.
Referring to the drawings, the web tension control device of the present invention, which may be positioned at any point in the machine Where accurate web tension control is desired, is shown as located on the machine, which may be a conventional printing press, for example, between the front frame 3 and the rear frame 4.
In FlGURE 1, the web W passes to the right under the idler rollers 11 and 12, travels upwardly around drive rollers 13 and 14 in a serpentine manner in the form of an S loop, then around idler roller 1S and lioating sensing roller 16, downwardly under idler roller 17 and over idler roller 18 from whence it continues on to another portion of the machine.
Shaft 21, driven by the drive means for the printing machine, has a bevel gear 22 thereon which meshes with a bevel gear 23 mounted on cross-shaft 24 supported in the front and rear frames 3 and 4, respectively, of the machine. One end 24a of cross-shaft 24 carries a pulley 25 with a groove therein for engaging a V belt 26 which drives a variable diameter pulley 27 mounted on the overhung extension 14h of the drive roller 14 (see FIG- URE 2).
The variable diameter pulley may be of the conventional type comprising a pair of conical disks that are spring biased toward each other into engagement with the belt 26, which may be of the conventional trapezoidal cross-section type. Any tendency toward an increase in belt tension will result in a decrease in pulley diameter, and vice versa. The variable diameter pulley is preferably of the type disclosed in my U.S. Patent No. 2,812,666, of November 12, 19'57, in which changes in the V-belt contacting radius are instantaneously responsive to variations in V-belt tension, with a minimum of attendant friction and energy loss. Drive roller 13 is driven by drive roller 14 by means of the meshing gears 13a and 14a respectively, mounted on drive rollers `13 and 14 as shown in FIGURE 2.
Arms 31 and 31a are securely fastened at one of their ends to pivot shaft 32 mounted in the frames 3 and 4 `and carry the floating sensing roller 16 between them is securely fastened an arm 33 supporting idler roller 34 which contacts the V belt 26 along its upper pass between Y the pulleys 25 and 27.
Belt 26 is shown passing beneath roller 34 (in full lines) as arranged for the web feed direction indicated by the solid .arrow heads on web W. If the machine is to be run in the reverse direction, proper web tension control can still be obtained, merely by passing belt 26 above roller 34, as indicated by the dash lines in FIGURE 1. The web direction in this case is indicated by the dash arrows alongside web W.
Arm 31 has a forward extension 35 to which a piston 36 supported in cylinder 37 and a dashpot 38 are pivotally connected. The piston 36 has a long narrow cylindrical cavity 36a for holding within cylinder 37 a large volume of fluid which is quickly compressible and expandable under the inuence of the sensed variations in web tension. This provides a piston and cylinder arrangement having desirable sensitive resilient operating characteristics. The dashpot 33 consists of a double-acting piston sliding within a closed .cylinder and is surrounded by a viscous damping material to damp out vibrations in the arms 31 and 31a and yfloating roller 16 carried thereby, and thus effectively prevent over-correction of previously sensed web tension variations. The cylinder 37 may have a lubricating fluid iilm. of any desired material between its piston and the cylinder wall, in order to provide substantially frictionless motion between the piston and the cylinder.
Idler pulley `41 lengages the lower surface of V belt 26 along its lower pass between pulleys 25 and 27 and provides `a means Vfor applying a variable tension to belt 26 in order to compensate for wear on the belt 2G and pulleys 25 and 27, as well as to provide a means for manually controlling the quantitative value of the tension applied to the web.
Arm 44 is pivoted on `frame 3 about stub shaft 45 and carries idler pulley `41 at one end and a threaded rod 43 at its opposite end. The threaded rod A43 passes through an opening in abutment 5, projecting from frame 3, and has a nut V42 thereon whereby upon adjusting nut 42 the position of idler roller 41 relative to belt 26 can be varied and thus select the desired quantitative value of tension applied to the web, or compensation made for any wear on the belt 26 and pulleys 25 and 27.
The action of floating sensing roller 16 in conjunction with the previously described variable speed drive constantly maintains the desired weby tension during operation of the device as more fully set forth hereinafter. Roller 16 is urged downwardly by its own weight and that of arms 31, 31a, 33 and roller 34, as well `as by the tension of web W. yRoller 16 is urged upwardly by V belt 26 (when in its yfull-line position, FIGURE 1) acting on idler pulley 34 through arm 33, pivot 32 and arms 31 and 31a, and by the adjustable force of cylinder 37 acting on piston 36 connected to the extension 35 of arm 31. Hand valve 52 regulates the -uid pressure transmitted Ito cylinder 37, acting against piston 36, from the pressure conduit 51, and the amount of fluid pressure so transmitted is indicated by pressure gauge 53, which if desired, may be calibrated in units of web tension. The forces exerted by web W andthe weights of arms 31, 31a and 33 and rollers 16 and 314, and the forces exerted by piston 36 and V belt 26 are normally in balance and thus maintain a constant tension in web W. Valve 52 is preferably of the automatic (e. g., diaphragm valve) type to maintain the pressure in cylinder 37 closely at the value selected by the operator.
yIn normal operation, a slight decrease in web tension causes an immediate unbalance of the above mentioned forces and results in an upward movement of arms 31, 31a and 33 about pivot shaft 32. As a result of this movement, idler pulley 34 moves upwardly and loosens belt 26 which permits variable diameter pulley 27 to compress and thereby increase its belt pitch radius so that pulley 27 is driven Iby V belt 26 at a slightly slower speed. Due to the slower speed of pulley 27 and the drive rollers 13 and 1-4 driven thereby, a smaller length of web (per unit of time) is pulled around drive rollers 13 and 14, which results in correspondingly increasing web tension until the original position of iioating sensing roller 16 is restored. Similarly, a slight increase in web tension causes the variable speed drive to :feed a greater length of web (per unit of time) through drive rollers 13 and 14, so as to restore the original web tension condition. As is readily apparent from the explanation given above, my variable drive means responds instantaneously and proportionally to any deviartions in web tension so as to automatically counteract and eliminate these deviations at all times during the operation of the device.
The drive rollers 13 and 114, about which the web W Wraps in S fashion may, if desired, be arranged to perform such oper-ations on webI W as heating and cooling by virtue of the circulation of any suitable material of the appropriate temperature level through -said cylindrical rollers by means of the coaxial inlet and outlet pipes 61 and 62, respectively, as shown in FIGURE 2.
The pressure fluid supplied by conduit 51 to cylinder 37 (and hollow piston 36) will normally `be compressed air, to provide adequate operating power coupled with cushioned resilient sensitivity to the motions of the sensing roller; however, other suitable pressure fluids of equivalent compression characteristics may be substituted.
Dashpot 3S, which is used to dampen the vertical motion of floating sensing roller 16, is required only where this vertical vibratory motion may become excessive, that is, such that the floating roller 16 begins to hunt Without permanently correcting web tension deviations. Obviously where the above conditions do not prevail the dashpot is not essential to the operation of the tension control mechanism, and may be eliminated therefrom rwithout altering the usefulness of the' device.
Propeller rollers 101 may be employed to maintain continuous firm contact between the web W and the web `drive rollers 13 and 14. As shown in FGURE 1, each roller 101 is rotatably supported at the outer end of a respective arm 102 secured to pivot shafts `103 rotatably mounted between the machine side frames 3 and 4. Torsion springs, indica-ted schematically at 104, are provided to urge `the respective arms 102 in the direction necessary to maintain rollers 101 in rm pressure against the web, and hence to maintain the web in rm driving contact with the rollers 13 and 14.
While a certain preferred form of the invention has been shown and described, it will be apparent to those skilled in the art that changes may be made in the pre- -ferred 4form shown, without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims. Accordingly, the'foregoing embodiment is to be taken as illustrative, rather than restrictive of the invention, and those modifications which come within lthe meaning and range of equivalency of the claims are to be included in the invention.
What is claimed is:
1. A web tension control mechanism comprising a framework, a web drive roller positively propelling the web, a variable speed belt drive connected to said drive roller for adjustment of the web drive speed by variations in the tension of the belt, a single pair of parallel lever arms coaxially mounted for rotation on said framework, a single floating Web-tension sensing roller mounted between said arms remote from their rotation axis lfor movement relative to said framework and bodily urged in one direction by the tension of the web passing over it and in the other direction by the operation of a sensitive-acting, resilient, essentially constant-force biasing means, and means responsive to bodily movements of said sensing roller induced by changes in the web tension for controlling the tension of the drive belt to alter the speed of said drive roller in the direction required to restore the original value of web tension; said biasing means comprising a cylinder and hollow-cavity piston connected -between said framework and `one of said lever arms and together defining a fluid-pressure chamber which is long relative to its diameter and to the normal travel movement of said sensing roller, and a pressure-regulated fluid pressure supply line communicating with said cavity.
2. A web tension control mechanism in accordance with claim 1, including means for adjusting the controlled value of iluid pressure in said supply line.
3. A web tension control mechanism in accordance with claim 1, including a closed-cylinder dashpot containing a double-acting piston surrounded by `a body of viscous damping materia-l; said vdashpot being connected 6 between -said framework and the bodily support mount of said sensing roller.
4. A web tension control mechanism in accordance with claim 1, including a manually-adjustable drive belt engaging roller -for establishing a desired nominal or reference value of web tension.
References Cited in the le of this patent UNITED STATES PATENTS 2,168,071 Perry Aug. 1, 1939 2,661,773 Kretzschmar Dec. 8, 1953 2,949,295 Huck Aug. 16, 1960 2,979,280 Ralph Apr. 11, 1961 2,995,944 `Ciaccio Aug. 15, 1961