Spring system assembly for tension compensating control device

Abstract

A spring system assembly including a bracket having a threaded bore. A tube threaded on one end is screwed into the bore and has a flange on the other end. An overload compression spring is positioned between the bracket and a washer engaging the flange. A rod, attached to the brake band of a tension compensating control device, extends through the tube. An annular member is mounted on the rod at the end of the tube and has an axially extending flange engaging the washer. The end of the rod is threaded and a Prony brake spring is positioned on the rod between the member and a nut threaded on the end of the rod.

Description

BACKGROUND OF THE INVENTION

The present invention relates to tension compensating control devices for supplying web or strand materials at constant tension, and, more particularly, to such devices which include a brake arrangement controlling the rotation of a supply roll and a tension sensing mechanism which actuates the brake arrangement to maintain uniform tension.

A control device of this type is disclosed in U.S. Pat. No. 3,139,243. The tension sensing mechanism includes two spaced rollers mounted on a spring biased rotatable plate. The web or strand extends from the supply roll around the two rollers in a Z-like path and then to the utilizing agency. The tension in the web or strand acts against and balances the spring biasing the rotatable plate. Any variation in the tension in the web or strand causes the plate to rotate to a new position. The brake arrangement includes a brake band and a lever attached to one end of the brake band. A brake actuating cable extends from this lever to a pulley which is rigidly mounted to the rotatable plate of the tension sensing arrangement. As this plate rotates in response to a change in tension, the rotation of the pulley causes the brake band to be tightened or loosened to reestablish the desired tension. The end of the brake band is attached to a spring system which prevents sudden and excessive forces from being applied by the brake band to the drum.

In the aforementioned patent, the spring system includes a lever pivoted on a stationary frame member. A shock-absorbing coil spring is attached between one end of this lever and the end of the brake band. A stronger overload spring is attached between the other end of the lever and a pin on the frame member to oppose the action of the first spring. This spring system, while useful in tension control devices providing low tension values, it does not readily lend itself to use in tension control devices operating at higher tension levels.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide an improved spring system for tension compensating control devices operating at high tension values.

Another object is to provide such a spring system which is easily adjustable.

Another object is to provide such a spring system which is compact and simple in construction.

The foregoing objects are accomplished by providing an overload compression spring captive between a bracket and a washer slideably mounted on a tube, a rod extending through the tube and connected to a brake band, an annular member mounted onto the rod to engage the washer, a nut on the end of the rod, and a prony brake spring captive between the nut and the annular member.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred embodiment of the invention has been chosen for the purposes of illustration and description, and is shown in the accompanying drawings forming a part of the specification, wherein:

FIG. 1 is a schematic view of a tension compensating control device incorporating a spring system according to the present invention; and

FIG. 2 is a longitudinal sectional view of the spring system taken along the line 2--2 in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings in detail, and particularly to FIG. 1 thereof, there is shown a tension compensating control device including a brake section 10 and a control section 11 both mounted on a frame plate 12.

The brake section 10 includes a spindle 14 journalled to the frame plate by suitable bearings (not shown). A roll 15 of material 16 (such as web or strand) wound on a core 17 is mounted on the spindle 14 and rotates the spindle as the material is drawn from the roll. A brake drum 18 is mounted on the spindle 14 to rotate therewith and a brake band 19 engages the drum 17. One end of the brake band 19 is connected to a lever 20 which is mounted on a pulley 21. The pulley 21 is rotatably mounted on a shaft 22 extending from the frame plate 12. The other end of the brake band 19 is connected to a spring system assembly 24 according to the present invention.

The control section 11 includes a diamond-shaped plate 25 mounted on a shaft 26 which is journalled on the frame plate 12 by means of suitable bearings. A torsion spring 27 mounted within a casing 29 biases the plate 25 in a counter-clockwise direction. A pulley 30 is mounted on the end of the shaft 26 to rotate therewith as the plate 25 rotates. A cable 31 extends between the pulley 30 and the pulley 21. The ends of the cable are attached to the pulleys so that rotation of the pulley 30 in the counter-clockwise direction winds up the cable and causes a clockwise rotation of the pulley 21 and the lever 20 carried thereby. A pair of rollers 32 and 33 are journalled on the plate 25 and the material 16 is threaded around the rollers in a Z-shaped path so that the tension in the material 16 opposes the spring 27. A bumper 34 is mounted on the plate 12 to limit the motion of the plate 25.

The spring system assembly 24 includes an L-shaped bracket 35 bolted to the frame plate 12 and formed with a threaded bore 36. A tubular spring retainer 37 having threads on one end and an annular radial flange 38 on the other end is screwed into the bore 36. A rod 39 extends axially through the retainer 37. One end of the rod is connected to the brake band 19 and the other end extends past the retainer 37 and is threaded. A low-rate compression spring 40 surrounds the retainer 37. A spring compressor member 41 having a hub 42 and an outer cylindrical flange 43 is positioned on the rod at the end of the retainer with the flange 43 extending over the flange 36. A flat washer 44 is positioned on the retainer 37, adjacent the flange 38, between the end of the spring 40 and the flange 43 of the member 41. A high rate prony brake compression spring 45 surrounds the threaded end of the rod 39. One end of the spring 45 engages the member 41 and the other end engages a spring washer 46 held in position by a nut 47 threaded on the rod 39.

In operation, the tension in the material 16 tends to rotate the plate 25 in a clockwise direction while the spring 27 tends to rotate the plate in the counter-clockwise direction. The nut 47 is positioned on the rod 39 so that when the tension in the material 16 is at the desired value, the spring 27 rotates the plate 25 into a position which produces a braking action on the roll 15 to maintain the desired tension as the roll unwinds. If the tension in the material 16 begins to decrease, the plate 25 is rotated counter-clockwise causing the pulley 30 to wind up the cable 31 and rotate the lever 20 clockwise to tighten the brake band 19. Conversely, an increase in tension in the material causes the plate 25 to rotate clockwise unwinding the cable 31 to loosen the brake band and allow the roll 15 to rotate more easily so as to decrease the tension in the material.

As the lever 20 pulls against the end of the brake band 19, the rod 39 moves and compresses the prony brake spring 45. When the material 16 experiences a sudden change in tension (for example, due to an acceleration or deceleration of the machine to which the material is being supplied), a sudden force is applied to the brake band. The prony brake spring 45 compresses or extends in response to such sudden forces and thus allows the change in braking force to be applied to the brake drum smoothly thus decreasing any tendency for the control device to oscillate or hunt.

When the tension in the material 16 decreases excessively, the low-rate overload spring 40 prevents the brake band from suddenly locking up the brake drum. The spring 40 is preloaded to the desired overload setting by screwing the tube 37 into the bracket 35. The loading on the high-rate spring 45 increases rapidly as it is compressed by the motion of the rod 39. When the loading on the spring 45 reaches the overload setting value, further motion of the rod 39 compresses the overload spring 40. Since this spring has a low rate, the loading thereon increases slowly as it compresses. Therefore, additional force applied by the brake band to the rod 39 compresses the spring 40 and sudden lock up of the brake is prevented.

It will be seen from the foregoing that the present invention provides an improved spring system assembly for tension compensating control devices which is capable of handling heavy loads and is compactly and simply constructed.

Claims

What is claimed is:

1. A spring system assembly for a tension compensating control device having a brake band operated by a control unit connected to one end of the brake band to act against a brake drum carried by a spindle for a roll of material, said spring system assembly comprising a bracket secured to a frame member, a tube having one end secured to said bracket and having a radially extending flange on the other end, said tube being axially adjustable with respect to said bracket, a washer mounted on said tube, a low-rate overload compression spring on said tube acting against said bracket and normally urging said washer against said flange, a rod extending through said tube having a first end attached to the other end of the brake band and having a second end, a stop member adjustably positioned on said second end, a spring compressing member slidably mounted on said rod and having an axial element positioned to contact said washer, and a high-rate prony brake compression spring on said rod acting against said stop member and said spring compressing member.

2. A spring system assembly according to claim 1 wherein said bracket is provided with a threaded bore, said tube is threaded and screwed into said bore to adjustably preload said overload spring.

3. A spring system assembly according to claim 2 wherein said second end of said rod is threaded and said stop member includes a nut threaded on said rod.