GB2079730A - Tensioning web by clamping side face of wound web reel - Google Patents

Abstract

A pair of arms (27) are clamped against the side faces of a wound web reel with a variable clamping pressure so as to maintain this tension in the unwinding web constant. The web withdrawn from the wound reel passes over a movable roller (18) which operates a pneumatic valve controlling a cylinder forcing the arms (27) against the wound reel. The wound reel may be axially movable in response to clamping pressure from an arm (27), the other arm on the other side face of the reel being fixed. The arms (27) ensure correct tensioning and lateral tracking of the web as it passes to a packaging machine. <IMAGE>

Description

SPECIFICATION Improvements in web-feeding apparatus This invention relates to apparatus for feeding a web of wrapping material to a packaging machine from a reel. This is normally effected by feed rollers, grippers or other means, the web being led over a yieldably mounted jockey roller and successive lengths of the web being withdrawn from the reel at intervals and subsequently cut to form wrappers.

The web must be fed to a fixed delivery position on the packaging machine and it is important to ensure that the web should be maintained under constant tension notwithstanding variations in speed of operation of the packaging machine.

Difficulty also arises in maintaining the web in the required feed path having regard to irregularities in winding of the web, which may have a width of 12-14 inches, in a reel which may have a diameter of 4 feet.

Thus it is often found in practice that the sides of the reel are not truly planar or that the web is more tightly wound at one side of the reel than the other.

Such irregularities can lead to buckling of the web if it is sought, as has been the practice in the past, to mount the reel in a fixed axial position aligned with the delivery position.

The invention provides apparatus for feeding a web of wrapping material from a reel to a packaging machine, comprising tracking arms mounted for heightwise movement on opposite sides of the reel and carrying side members which bear against the sides of the reel, means for causing said members to apply a variable clamping pressure to the reel, sensing means for sensing variations in tension in the web drawn from the reel, and control mechanism operative by the sensing means to so vary the clamping pressure applied to the web as to maintain the tension in the web substantially constant.

In a preferred embodiment of the invention the reel is supported by a shaft capable of axial movement, the tracking arms carry followers which rest on the upper portion of the reel and the variable clamping pressure is applied to one only of the side members, the other being fixed to its respective tracking arm.

An example of a web-feeding apparatus constructed in accordance with the invention will now be described with reference to the accompanying drawings in which: Figure 1 is an elevation, Figure 2 is a view on a larger scale taken in the direction of the arrow A in Figure 1, Figure 3 is an enlarged view in elevation of a portion of the mechanism shown in Figure 1, and Figures 4 and 5 are diagrams illustrating the operation of mechanism for controlling the tension of the web.

Aweb 11 of wrapping material is shown in Figure 1 being fed from a reel 12 which is freely mounted on a shaft 13 by cones forced into the ends of a cardboard tube on which the web is wound. The shaft 13 is rotatably mounted on rollers 14 mounted on brackets 16 (one only shown) positioned at each side of the reel 12 and secured to a framework (not shown) of the apparatus. The web 11 passes over a driven guide roller 17, rotatably mounted on the framework, and then over a jockey roller 18 freely mounted on spring-loaded arms 19 pivoted at 21 in the framework. Measuring rollers (not shown) withdraw successive lengths of the web 11 from the reel 12, such lengths being subsequently cut to form wrapper blanks.

The web 11 is maintained in the desired feed path by a pair of tracking arms 22 and 23, disposed as shown in Figure 2 on opposite sides of the reel 12, and pivotally mounted on a shaft 24 disposed above the reel 12. Rollers 26, rotatably mounted on the ends of the arms 22 and 23, bear by gravity on the upper portion of the reel 12 near its opposite edges.

A plate 27 is secured to the arm 22 and extends downwardly therefrom to engage a portion of one side face of the reel 12. A similar plate 28 is mounted by a trunnion 28A on an arm 29 secured to a spindle 31 rotatably mounted in a bearing 32 formed in the arm 23. One end of a further arm 33 is also secured to the spindle 31, the other end of the arm 33 being connected by a link 34 to the piston 36 of a double-acting air cylinder 37 mounted at 38 on a plate 39 extending between and secured to the arms 22 and 23. Under normal running conditions of the apparatus, air under low pressure is supplied to the cylinder 37 which causes the plate 28 to lightly engage a portion of the opposite side face of the reel 12 to that engaged by the plate 27.

As successive lengths of wrapping material are withdrawn from the reel 12, with a consequential reduction in the diameter of the reel 12, the weight of the arms 22 and 23 maintains the rollers 26 in contact with the surface of the reel 12 and hence the plates 27 and 28 in engagement with portions of the side faces of the reel 12 to eliminate "tracking" of the web 11 and maintain it in the correct feed path at all times.

In use, the jockey roller 18 and its arms 19 fluctuate between upper and lower positions determined by the wrapper feed of the packaging machine and the tension in the web 11. The clamping force between the plates 27 and 28 is so regulated, as will now been exlained with reference to Figures 4 and 5, that the tension in the web is kept constant.

As shown in Figure 4, transducers 40 are disposed on opposite sides of one of the arms 19 and these transducers produce electrical signals representing the deflection of this arm upwardly or downwardly from a neutral position representing the desired tension in the web.

As shown in Figure 5, actuating pressure is supplied to the cylinder 37 through a valve 41 maintained in position to apply pressurised air to the left hand side of the cylinder by application to the valve through a line 42 of pilot air pressure at 70-80 p.s.i. The pressure supply to the cylinder 37 through the valve 41 is controlled to a lower pressure of the order of 30 p.s.i. by a low pressure regulator 43, which is adjusted under control of the transducers 40 so as to adjust the clamping force applied by plates 27,28 in response to rise or fall of the arm 19 in such a way as to cause return of the arm to its neutral position.

Under normal conditions the air pressure passing through the regulator 43 holds a ball valve 44 against a left hand seat 45A to close a line 46 leading from the source of air pressure through a high pressure regulator 47 and a valve 48 normally held closed by pilot high pressure. In the event of stoppage of the packaging machine, an emergency switch opens the valve 48 to cause the ball valve 44to move to its other seat 45B and admit high pressure air to the cylinder 37 to clamp the plates 27 and 28 tightly to the reel 12 and prevent further feed of the web.

The reel shaft of a web-feeding apparatus is normally incapable of axial movement except when manually adjusted. Since in the apparatus according to the invention the reel 12 and the shaft 13 are capable of limited axial movement, correct web tracking is brought about by the side plates 27 and 28. The yieldable mounting of the plate 28 creates a tensioning force on the edge of the reel to keep the unwinding loads constant. If two fixed plates were used some additional reel retarding means would be required to prevent over-run of the reel as the wrappers are withdrawn or when the wrapping machine stops and the inertia of the reel causes it to continue to unwind.

The invention thus not only maintains constant tension in the web but also ensures alignment of the web of wrapping material with the feed table of the wrapping machine and maintains the web in its correct paths despite irregularities in the reel due to the mode of winding ortensioning of the web.

Claims (6)

1. Apparatusforfeeding awebofwrapping material from a reel to a packaging machine, comprising tracking arms mounted for heightwise movement on opposite sides of the reel and carrying side members which bear against the sides of the reel, means for causing said members to apply a variable clamping pressure to the reel, sensing means for sensing variations in tension in the web drawn from the reel, and control mechanism operative by a sensing means to so vary the clamping pressure applied to the web as to maintain the tension in the web substantially constant.

2. Apparatus according to claim 1, in which the sensing means comprise a yieldably mounted jockey roller and transducers for sensing variations in level of the jockey roller.

3. Apparatus according to claim 1, wherein the reel is supported buy a shaft capable of axial move ment, the tracking arms carry followers which rest on the upper portion of the reel and the variable clamping pressure is applied to one only of the side members, the other being fixed to its respective tracking arm.

4. Apparatus according to claim 3, which includes a pneumatic cylinder for applying the variable clamping pressure to the side member and a pressure regulator controlled by a jockey roller responsive to the tension in the web to vary said clamping pressure.

5. Apparatus according to any one of the preced ing claims, which includes means responsive to stoppage of the packaging machine for applying sufficient clamping pressure to the reel to prevent feed of the web.

6. Apparatus according to claim 1, substantially as described herein with reference to the accompanying drawings.