US3048346A - Tensioning apparatus for tenuous material - Google Patents

Description

2 Sheets-Sheet l m MN W III g o I II I I INVENTOR. ZEONARD A. KARBER BY Afibfifliy Aug 7, 1962 L. A. KARBER TENSIONING APPARATUS FOR TENUOUS MATERIAL Filed April 6, 1959 I I I I I I I I I 3,048,346 TENSIONING APPARATUS FOR TENUOUS MATERIAL Leonard A. Karber, Sharon, Pa., assignor to Herr Equipment Corporation Filed Apr. 6, 1959, Ser. No. 804,339 8 Claims. (Cl. 242-755) The present invention relates to tensioning apparatus, more particularly to apparatus for maintaining a predeter-mined tension on longitudinally moving tenuous material, and the principal object of the invention is to provide new and improved apparatus of the character described.

Apparatus for tensioning longitudinally moving tenuous material has long been used in the manufacture, handling and processing of metal strip and like materials. Heretofore, however, none of this apparatus has been sulficiently sensitive for certain operations. For example, one of such operations requires that a length of metal strip be fed horizontally through an oven, supported only at its ends, so that such strip portion forms a catenary. Sufiicient tension must be maintained on the strip to prevent excessive catenary depth; however, since in some instances the strip may be as thin as a thousandth of an inch and since its tensile strength may be lower than normal because of oven heat, the maximum tension to which the strip can be subjected without exceeding its yield point is apt to be quite limited. The net result of the foregoing circumstances is to require that the strip be accurately tensioned within very close limits.

Prior art tensioning apparatus, while suitable for less critical uses, has been unsuitable under conditions above described when a relatively heavy tension must be maintained within extremely close limits. In contrast, the present invention may apply any desired tension on moving strip, within the design limits of the device of course, which tension will be maintained With a variance of less than one pound. This is true even though the applied tension may amount to hundreds of pounds. Other advantages will readily become apparent from a study of the following description and from the drawings appended hereto.

In the drawings accompanying this specification and forming a part of this application there is shown, for purpose of illustration, an embodiment which the invention may assume, and in these drawings:

FIGURE 1 is a side elevational view of a preferred embodiment of the invention shown in combination with a portion of a continuous strip processing line,

FIGURE 2 is an enlarged side elevational view of the improved tensioning apparatus seen in- FIGURE 1,

FIGURE 3 isan end elevational view of the apparatus seen in FIGURE 2,

FIGURE 4 is a top plan view thereof, and

FIGURES 5 and 6 are diagrammatic views illustrating an operating principles of the apparatus.

With reference to FIGURE 1, there is shown tensioning apparatus 10 being used for tensioning strip material S as it passes in the direction of the arrows through an elongated oven or like device 11. At the left, or entrance end of the oven, there is positioned a pair of pinch rolls 12 between which the strip passes and which tightly grip the latter. Although not shown, these pinch rolls are adapted to be rotated by any suitable means to pass the strip to the oven at a predetermined rate.

Apparatus 10, forming the subject matter of the pres- 3,048,346 Patented Aug. 7, 1962 ent application for Letters Patent, is adapted to withdraw the strip from the oven at substantially the same rate at which the pinch rolls 12 feed the strip thereinto and to pass the strip to subsequent strip handling apparatus of any desirable type which is, however, not illustrated since it neither forms a part of the present invention nor is it necessary for an understanding thereof. As will appear, appear, apparatus 10 not only functions to draw the strip from the oven but also functions to place the strip portion within the oven under the desired tension. Briefly, the reason for tensioning the strip portion within the oven is as follows:

In many instances, of which the present case is an example, it is essential that the strip be freely suspended within the oven; that is, the strip cannot be supported interiorly of the oven by underlying rollers or the like but must be supported entirely by the strip portions projecting from respective oven ends. Obviously, since the strip extends horizontally through the oven, the weight of the strip causes it to sag. It is to prevent excessive sagging of the strip which necessitates the tensioning thereof.

It is to be understood that when relatively heavy strip is being handled, the tensioning thereof does not present a serious problem and many of the prior art tension devices may be satisfactorily employed. Indeed, when the processing line with which the present apparatus is associated is employed With strip more than about ten thousandths of an inch thick, the present device need not be used for tensioning at all since conventional tensioning devices at other parts of the processing line will function satisfactorily for tensioning the strip portion within the oven. This results because of the fact that when such relatively heavy strip is being processed, a tensioning force considerably in excess of that necessary to properly tension the strip may be readily exerted thereon without harmful results. When, however, strip having a thickness of, perhaps, one thousandth of an inch is being processed, the amount of force necessary to properly tension the strip may be very close to the maximum force which can be exerted on the strip, especially in its weakened condition as a result of its elevated temperature within the oven, without stretching, rupturing or otherwise damaging the strip. It is to maintain the above described delicate balance of tensioning force upon relatively thin strip which is a principal object of the present tensioning apparatus.

Still refer-ring to FIGURE 1 but as also seen in FIG- URE 2, apparatus 10 presently comprises a pair of rolls 13 and 14 rotatably supported in spaced-apart relation by respective roll stands 15 and 16. It is to he noted that rolls 13, 14 are herein shown to be of the same diameter and that their axes lie in a plane which is generally parallel tothe desired path of travel of the strip through the oven (it being understood, of course, that the strip will not assume within the oven the straight line illustrated but will sag downwardly therefrom at its central portions) so that the upper peripheries of such rolls will be tangent to a plane which is parallel to such desired path of strip travel.

As illustrated, the strip emerges from the oven and passes over the rolls 13, 14, being deflected to a loop formation between such rolls as will hereinafter be more particularly described, and over a roll 17 disposed beneath roll 14 and rotatably carried by the roll stand 16. From the roll 17, the strip passes to any desired strip handling devices. Although not shown, an additional roll may be provided to force the strip closely against the periphery of either of the rolls 14, 17 to insure against slippage between these rolls and the strip. For the same purpose, rolls 14, 17 may have their working faces coated with a suitable non-slip material such as rubber or the like.

As previously mentioned, apparatus is adapted to Withdraw from the oven, strip fed thereinto by the pinch rolls 12. Accordingly, means 18 is provided (see FIG- URE 3) for driving the rolls 14, 17. Such means may be of any suitable type capable of speed regulation for a purpose to appear. In the present embodiment, roll 13 carried by stand is not driven but is merely an idler roll.

Still referring to FIGURES l and 2, the strip S is adapted to be deflected into a loop formation intermediate the rolls 13, 14, as heretofore disclosed, by means of an idler roll 19 which is bodily shiftable vertically (in the position of parts shown) to increase and decrease the size of the strip loop. (Note that roll 19 is of a diameter to pass between the rolls 13, 14 so that it may be shifted from the full line position seen in FIG- URE 2 to the phantom line position indicated at B when its use is not required to tension the strip.)

It is an important feature of the present invention that roll 19 is movable in a rectilinear path which is perpendicular to a plane tangent to the upper peripheries of the rolls 13, 14 and is precisely centered between such rolls. This insures that both sides of the strip loop will increase and decrease in length at the same rate as the loop increases and decreases in size to preclude the application of a greater tension on one side of the loop than on the other during a change in loop size. It is also an important feature of the invention that roll 19 is supported for movement by pivoted link means to provide for minimum frictional resistance to such movement to thus increase the sensitivity of the present inventions strip tensioning function.

In order to provide the desirable features of constraining roll 19 to rectilinear movement while supporting it for minimum frictional resistance to such movement, roll 19 is supported by means known as the Watt Straight Line Movement. As best seen in FIGURES 2 and 4, such means presently comprises a first link means having one end pivoted to roll stand 15 and having its other end providing spaced leg portions for receiving the roll 19 therebetween and pivotally secured to such roll by means to be disclosed. Second link means 21 is pivoted to roll stand 16 at 22 and provides spaced leg portions for receiving roll 19 therebetween. The means for connecting roll 19 to the link means 20, 21 comprises short links 23 disposed at opposite ends of the roll 19 and having their intermediate portions rotatably connected to respective roll ends and having their end portions pivotally connected to respective adjoining ends of the link means 20, 21.

With the link mechanism thus far described, it will be understood that as the link means 20 and 21 simultaneously swing in respective arcs about their pivots thus bodily shifting roll 19, the latter will, nevertheless, move in a straight line because of the compensating effect of links 23 which tilt about the axis of roll 19 during such link means movement.

Since the weight of roll 19 and of the links 20, 21 and 22 may be so great that too much tension would be applied by such roll riding in the loop of material, means are provided to reduce the effective weight of the roll and the links. At the present time, this is done in the following manner. Second link means 21 extends beyond pivot 22 and provides in spaced relation with pivot 22 and on the opposite side thereof from roll 19, a strut 24 which extends between the spaced legs of this link means. Pivotally secured to the central portion of strut 24 is a depending rod 25 having a transversely extending flange 26 at its lower end (see also FIGURE 3). In order to reduce the effective weight of roll 19, it is only necessary to support on the rod flange 26a Weight 27 suflicient to counterbalance, to the requisite degree, the weight of roll 19. Similarly, if roll 19 does not have sutficient weight to provide the requisite tension in the strip, weight may be added to the roll by placing weights upon a rod (FIGURE 2) depending from and pivotable with respect to the axis of roll 19.

Still referring to FIGURES 2 and 3, one end of strut 24 has a chain 28 depending therefrom. The lower end of chain 28 is secured to a reactor 29 which. controls the speed of drive means 18 to which the reactor is connected by means of suitable electric wiring 129. Briefly, if the roll 19 moves downwardly from the full line position shown in FIGURE 2, chain 28 will cause elevation of a portion of the reactor to effect an increase in the speed of the drive means 18. Conversely, if the roll 19 moves upwardly from the full line position shown, chain 28 will permit the reactor portion to be lowered to reduce the speed of the drive means 13. With the speed of drive means 18 thus controlled, roll 19 will tend to remain positioned as seen in full lines during operation of the apparatus in tensioning the moving strip.

With the construction thus far described, operation will be as follows: Assuming that the strip is passed over the various rolls as seen in FIGURES 1 and 2 and is moving longitudinally in the direction of the arrows, assuming that the drive means 18 is rotating the rolls 14, 17 at a rate to withdraw the strip from the oven at the same rate at which it is fed into the oven by the pinch rolls 12, and further assuming that counterweight 27 is such that roll 19 applies the requisite tension to the loop in the strip, it will be understood that the present apparatus will maintain the strip portion within the oven under a predetermined tension. If now, the pinch rolls 12 should, for any reason, begin to feed strip to the oven at a slower rate, rolls 14, 17 which are still operating at the rate earlier mentioned, would tend to increase the tension on the strip portion intermediate the pinch rolls 12 and the rolls 14, 17. However, if this occurs, the loop in the strip will decrease in size as roll 19 moves upwardly to prevent an increase in tension in the strip until such roll assumes, for example, the phantom posi tion indicated at A. This elevation of the roll 19 will effect a reduction of speed of the drive means 18 to thus bring the operational rate of the rolls 14, 17 into balance with that of the pinch rolls 12.

Conversely, should the pinch rolls 12 begin to operate at a higher speed, the tension upon the strip would tend to decrease. This would cause the loop to increase in size as the roll 19 moves downwardly to prevent a decrease in the tension on the strip. As the roll 19 moves downwardly from its full line position, it will cause an increase in speed of the drive means 18 to thus once again bring the operational rate of the rolls 14, 17 into balance with that of the pinch rolls.

From the foregoing, it will be understood that the loop in the strip in which roll 19 rides will increase in size to prevent a decrease in strip tension and will decrease in size to prevent an increase in strip tension. Additionally, by virtue of the speed regulation of the drive means 18, in accordance with the position of the roll 19 and thus in accordance with the size of the loop, the operational rate of the rolls 14, 17 will be maintained in balance with that of the pinch rolls 12.

Referring to FIGURES 5 and 6 wherein the rolls 13, 14 and 19 are diagrammatically shown in engagement with the strip, FIGURE 5 illustrates the rolls in generally the same position in which they are seen in FIGURE 2 while FIGURE 6 illustrates the roll 19 in a position elevated from that seen in FIGURE 5. With a given effective weight of roll 19 and with the roll positioned as seen in FIGURE 5, the angularity which is indicated between the vertical path of movement of the roll 19 and a side of the loop in the strip will result in a given tension being applied by the roll to the strip. Now, however, if roll 19 is elevated to the position seen in FIGURE 6, the angularity above mentioned will be greatly increased, as illustrated, thus resulting in a greater tension being applied to the strip by the roll even though the effective weight of the latter has not been changed. Conversely, if roll 19 is lowered, the above mentioned angularity decreases and thus the strip will be tensioned a lesser amount even though the weight of the roll remains constant.

In order to eliminate, or at least reduce, the variation in tension in the strip caused by the above described change in angularity which results from vertical movement of roll 19, the following construction is employed: As seen in FIGURE 2 and with roll 19 positioned in its normal, full line position shown, it will be noted that strut 24, to which rod is secured, is positioned above a horizontal plane Z which passes through link means pivot 22. Accordingly, as roll 19 moves upwardly from the full line position shown, strut 24 will swing in an arcuate path downwardly toward plane Z. This arcuate movement of the strut causes a progressive increase in effective length of the lever arm supporting the counterweight 27 until such time as the axis of the strut coincides with the plane Z.

With the foregoing in mind, assume that the roll 19 has moved upwardly from the full line position seen in FIGURE 2 to the phantom position A. In so moving, the angularity disclosed with respect to FIGURES 5 and 6, will increase, thus tending to subject the strip to a greater tension; however, in moving upwardly, roll 19 has caused strut 24 to move downwardly toward the plane Z thus increasing the effective length of the lever arm supporting the counterweight 27 and therefore increasing the latters effectiveness in counteracting the Weight of the roll 19. With an increase in effectiveness of the counterweight, the effective weight of the roll 19 will be decreased thus tending to decrease the strip tension. It will be clear that in order to prevent an increase in tension on the strip When roll 19 moves upwardly, it is only necessary to so arrange the parts that the decrease in effective weight of roll 19 caused by an increase in the effective length of the lever arm supporting the counterweight will balance the tendency of the roll to increase strip tension as the roll moves upwardly. It will also be clear that as roll 19 moves downwardly from its full line position, the angularity mentioned in with respect to FIG- URES 5 and 6 will decrease, thus tending to decrease the tension on the strip. However, such movement of roll 19 will cause strut 24 to move upwardly to decrease the effective length of the lever arm supporting the counterweight and therefore increase the effective weight of the roll to counteract the tendency of the latter to tension the strip a lesser amount.

As hereinbefore mentioned, roll 1-9 need not be used when relatively heavy strip is being handled; accordingly, when such is the case, this roll may be elevated to the position seen in phantom lines at B in FIGURE 2 and supported in this position by any suitable latch or the like to thus eliminate the loop in the strip and permit the strip to pass directly from roll 13 to roll 14.

In view of the foregoing, it will be apparent to those skilled in the art that I have accomplished at least the principal object of my invention and it will also be apparent to those skilled in the art that the embodiment herein described may be variously changed and modified, without departing from the spirit of the invention, and that the invention is capable of uses and has advantages not herein specifically described, hence it will be appreciated that the herein disclosed embodiment is illustrative only, and that my invention is not limited thereto.

I claim:

1. Apparatus for maintaining a predetermined tension on longitudinally moving tenuous material, comprising a plurality of rotatably mounted rolls over which the material passes in the form of a loop and one of said rolls riding in said loop and being movable transversely of its axis in a rectilinear path as said loop changes in size and exerting a force tending to enlarge said loop and thus tension said material, and a plurality of pivotally interconnected link members connected to said one roll and constraining the latter to movement along said rectilinear path with minimum frictional resistance.

2.. Apparatus for maintaining a predetermined tension on longitudinally moving tenuous material, comprising a pair of rotatably mounted rolls in spaced-apart, side by side relation over which the material passes and between which such material assumes a loop formation, a third roll riding in the loop of said material and movable transversely of its axis in a rectilinear path toward and away from said roll pair as said loop changes in size and exerting a force tending to enlarge said loop and thus tension said material, and a plurality of pivotally interconnected link members connected to said third roll and constraining the latter to movement along said rectilinear path with minimum frictional resistance.

3. Apparatus for maintaining a predetermined tension on longitudinally moving tenuous material, comprising a pair of rotatably mounted rolls in spaced-apart side by side relation over which the material passes and between which such material assumes a loop formation, a third roll disposed in the loop of said material and movable transversely of its axis as said loop changes in size and exerting a force tending to enlarge said loop and thus tension said material, and a plurality of pivotally interconnected link members connected to said third roll and constraining the latter to movement with minimum frictional resistance in a rectilinear path perpendicular to a plane passing through the axes of said roll pair.

4. Apparatus for maintaining a predetermined tension on longitudinally moving tenuous material, comprising a pair of rotatably mounted rolls in spaced-apart side by side relation over which the material passes and between which such material assumes a loop formation, a third roll disposed in the loop of said material and movable transversely of its axis as said loop change in size and exerting a force tending to enlarge said loop and thus tension said material, and a plurality of pivotally interconnected link members connected to said third roll and constraining the latter to movement with minimum frictional resistance in a rectilinear path perpendicular to a plane tangent to the peripheries of the roll pair.

5. Apparatus for maintaining a predetermined tension on longitudinally moving tenuous material, comprising a pair of rotatably mounted rolls in spaced-apart, side by side relation over which the material passes and between which such material assumes a loop formation, a pair of link members adjacent said rolls swingable about respective transversely spaced pivots and each link member extending toward the pivot of the other to dispose portions of respective link members in spaced-apart adjoining relation intermediate said pivots, a third link member pivotally connecting said portions of respective link members of said pair, and a roll rotatably carried by said third link member intermediate its pivotal connections with respective link members of said pair, said roll riding in the loop of said material and exerting a force tending to enlarge said loop and thus tension said material and said roll being constrained by said link members to movement with minimum frictional resistance transversely of its axis in a rectilinear path toward and away from said roll pair as said loop changes in size.

6. Apparatus for maintaining a predetermined tension on longitudinally moving tenuous material, comprising a plurality of rotatably mounted rolls over which the material passes in the form of a loop and one of said rolls riding in said loop and being movable transversely of its axis in a rectilinear path as said loop changes in size, first and second means operable to respectively feed material to said loop and to withdraw material therefrom at predetermined rates, a plurality of pivotally interconnected link members connected to said one roll and constraining the latter to movement along said rectilinear path and with minimum frictional resistance, and means responsive to the position of said one roll along said rectilinear path for varying the relative operating rates of said first and second means in accordance with the position of said one roll.

7. The construction of claim 1 wherein said one roll is shiftable away from engagement with the material when tensioning of the latter is not required.

8. The construction of claim 5 wherein said link members are duplicated at respective ends of said roll.

References Cited in the file of this patent UNITED STATES PATENTS Robinson- Feb. 7, 1893 Gates Nov. 29, 1932 Bedell June 26, 1934 Cline July 2, 1935 Cohn et a1 Sept. 5, 1939 Stone et a1. Sept. 25, 1951

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