GB2138400A

GB2138400A - Braking reel during unwinding

Info

Publication number: GB2138400A
Application number: GB08406830A
Authority: GB
Inventors: Karl Grosse
Original assignee: Nagema VEB
Current assignee: Nagema VEB
Priority date: 1983-04-14
Filing date: 1984-03-15
Publication date: 1984-10-24
Also published as: IT8447980A1; IT1177643B; GB2138400B; DD214582A1; DE3403733C2; DE3403733A1; IT8447980A0; GB8406830D0

Abstract

Reel braking is controlled by tension changes in the unwound material. A reel (B) from which material (P) is unwound is braked by a shoe (19) applied by a spring- biased pivoting lever (14). Rollers on a spring-biased rocker arm (5) guide the material. Tension changes rock the arm, whose movement is limited by a stop (6). The arm rotates a hub within a rotatable housing (8), the hub engaging the housing via spring-urged friction discs. A pin-and-slot connection allows movement between the hub and discs. Housing rotation urges a housing roller (8b) against an adjustable torsion spring (17) on the lever (14) to apply the brake. A stop (12) limits housing movement. The arrangement allows even material feeding, with damped brake actuation. <IMAGE>

Description

SPECIFICATION Device for controlling the brake for packing material The invention relates to a device for controlling the brake for packing material and acting on the reel shaft and having a flexibly mounted brake lever arm arranged to be adjustable by means of the rocker arm which is actuated by the packing material and which is mounted to the side of the reel in such a way that by means of a hub on a fixed shaft it can be pivoted outwards as far as a stop and which is provided with guide rollers over which the strip of packing material, in conjuction with fixed deflector rollers adjacent thereto, is drawn off the reel by the take-off rollers of the packing machine.

An apparatus of the type mentioned at the beginning is already known. The rocker arm with the guide rollers in conjuction with the deflector rollers adjacent thereto serves to generate a storage effect for the packing material between the reel and the take-off rollers.

The rocker arm end mounted on a shaft has a control cam which actuates the brake lever arm in accordance with the angular position which the rocker arm is caused to assume by the take-off action, thus acting on the packing material brake acting on the reel shaft. Within a certain range of angular positions for the rocker arm the force-locked connection between the cam and the brake lever is the nullified, causing the packing material brake to be lifted clear (AT Pat. 217961).

This construction suffers from the drawback that in modern high-performance machines the rocker arm oscillates continuously and with a relatively ample angular deflection. As the peripheral speed of the reel in this type of control system continuously varies from 0 to twice the take-off speed, high braking forces are required which have a harmful effect on the strip of packing material. This latter is also liable to be deflected to one side. A further known apparatus serves to draw off the strip of packing material from a delivery roll, representing an attempt to provide a different solution to the problem of the strain suffered by the packing material when being drawn off the reel.This apparatus has a friction clutch connected with the drive of the wrapping machine and also a loop scanning device which follows the take-off roller and which actuates the friction clutch via intermediate mechanical elements. This invention is characterized by the fact that the friction clutch consists of belt pulleys adjustable in relation to one another and of a belt which passes round them (Ger. Unexamd. Spec. 27 07 958). Still further solutions on these lines are known but suffer from the drawback that the use of braking or retarding means between the reel and the take-off rollers necessitate additional expense.

The purpose of the invention is to enable the strip of packing material to be fed evenly into position at far lower cost.

The aim is to control the reel brake in accordance with the direction of motion of the rocker arm.

The invention achieves this object as a result of the fact that the hub of the rocker arm is provided with an external bearing ring surrounded by a housing part and supported by means of spring-loaded discs against both sides of the said housing part, the periphery of which has a limiting groove engaged by a fixed stop lever and at the bottom of which a radial projection is provided which bears a contact pressure roller resting on the brake lever arm. This offers the advantage that the braking forces acting on the strip of packing material are only slight, the detachment or release of the brake being damped by the frictional effect occurring at the bearing point of the rocker arm. The brake is also actuated less frequently, as the brake lever does not come into operation until the rocker assumes a greater angle for contact with the stop.

According to a further characteristic of the invention the bearing ring contains a pin which is coaxial with the shaft and which on both sides engages an appropriate slot in the discs. This means that in the zone of the slot the friction between the housing part and the discs is increased in steps as a result of a relative inhibiting action. Finally, the invention is also characterized by the fact that the radial projection on the housing part acts on the free end of the brake lever arm via a torsion spring. This measure provides a further contribution to damped operation of the packing material brake.

Example The drawing illustrates the invention by an example. The diagrams are as follows: Figure 1 A lateral view.

Figure 2 A transverse section through the bearing point of the rocker arm.

Figure 3 A longitudinal cross section through the bearing point of the rocker arm.

The apparatus for feeding a strip of packing material P into position forms part of a highperformance packing machine not shown in the drawing, particularly for sweets, Fig. 1 only showing the take-off rollers 1 and 2. The strip of packing material P, wound onto a reel B, is conveyed to the take-off rollers 1 and 2 by the mechanical parts described in detail farther on. The reel B is mounted on a reel shaft 3 having a brake drum 3b at the side. In the zone between the take-off rollers 1 and 2 is a fixed shaft 4 on which is mounted a rocker arm 5 by means of a hub 5a, being pivotable outwards as far as a stop 6. The rocker arm 5 is biased by a spring 6a and provided with guide rollers 5b, Sc and 5d via which a strip of packing material P is guided in conjunction with fixed deflector rollers 7 adjacent thereto.The hub 5a of the rocker arm 5 is provided with an external bearing ring 5e surrounded by a housing part 8. On both sides of the hub 5a discs 9 are provided inside the housing part 8 and are pressed against the inner wall of the said housing part 8 by pressure springs 10 inserted in the bearing ring 5e. On the periphery of the housing part 8 is a limiting groove 11 engaged by a fixed stop lever 12. The bottom of the housing part 8 is provided with a radial projection 8a on the front of which is mounted a radial contact pressure roller 8b. In the bearing ring 5e a pin 1 3 is mounted coaxially with a shaft 4 and engages on both sides, an appropriate slot 9a in the discs 9.

Underneath the parts which have just been described a horizontal brake lever arm 14 is mounted in a swivel shaft 15 secured at the other end by a tension spring 1 6 mounted in the housing not shown in the drawing. To the top of the brake lever 14 is affixed a torsion spring 1 7 which can be adjusted by an adjusting screw 1 8 until it comes to rest against the contact pressure roller 8b. On that end of the brake lever arm 14 which is mounted on the swivel shaft 1 5 is a brake shoe 1 9 which, in the operative position, rests against the brake drum 3b.

The method of operation of the apparatus described forms an integral part of the following description.

It will first be assumed that the reel B remains ideal at the beginning of the process.

In this idle position the brake shoe 1 9 rests against the brake drum 3b, as the rocker arm 5 is drawn by the tractive force of the spring 6a against the stop 2, so that the contact pressure roller 8b on the housing part 8 is resting on the brake lever arm 14, which actuates a brake shoe 1 9.

At the beginning of the operation, i.e. when the packing material starts to be transported by the take-off rollers 1 and 2, the rocker arm 5, overcoming the tractive force of the spring 6a, swings into the direction of transport, in which process that part of the strip of packing material which is stored in that position will first of all be used up. With the said oscillating movement of the rocker arm 5 the position of the housing part 8 is at the same time altered, so that the contact pressure roller 8b moves in the -direction of motion of the rocker arm 5 away from the torsion spring 1 7 and thus from the brake lever arm 14. The brake lever arm 14 is drawn upwards by the tension spring 16, so that the brake shoe 1 9 detaches itself from the brake drum 3b.The housing part 8, after the detachment of the brake shoe 1 9a, is held in this position by the stop lever 1 2. By the tractive force of the spring 6a largely constant tractive force occurs over the rocker 5 in the strip of packing material P, the reel B thus being evenly accelerated. The housing part 8 follows the movement of the rocker arm 5 until it is secured in its position by the stop lever 1 2. The rocker arm 5, however, continues to move in the same direction. If the reel B is accelerated by the tractive force acting in the strip of packing material P to such an extent that its peripheral speed is equal to the packing material speed generated by the take-off rollers 1 and 2, then the rocker arm movement comes to a stop.

Since, however, the spring 6a, via the strip of packing material P, continues to exert a force on the reel B, the peripheral speed of the said reel B continues to increase. The difference between the packing material delivered from the reel B and the material taken by the takeoff rollers 1 and 2 has to be stored by the reserve movement of the rocker arm 5. This reserve movement of the rocker arm takes the housing part 8 with it and detaches it from the stop lever 12. The contact pressure roller 8b on the housing part 8 begins to press on the torsion spring 1 7 of the brake lever arm 14, initiating the braking of the reel B via the brake shoe 1 9 and the brake drum 3b.The braking moment acting on the reel B is then proportional to the contact pressure between the contact pressure roller 8b and the torsion spring 17, the said contact pressure of the contact pressure roller 8b being determined by the frictional moment generated by the pressure springs 10 and the frictional moment of the pressure springs 10 and the disc 9 or the disc 9 of the housing part 8.The discs 9, by means of a slot 9a engaged by a pin 1 3 occupying a fixed position in the hub 5a, are only rotatable by a slight angle in relation to the hub 5a, so that according to the combination of two materials a slight frictional moment is first of all generated, followed by a greater frictional moment after the rocker arm 5 has reached a greater angle of rotation, this greater frictional moment taking effect on the contact pressure roller 8b as a contact pressure force of different magnitude. When the rocker arm 5 swings back, therefore, a slighter braking movement occurs, which once again reduces the peripheral speed of the reel B and, the material being taken off uniformly by the take-off rollers 1 and 2, ensures that a relative equilibrium very rapidly occurs between the acceleration and retardation forces acting on the reel B, the peripheral speed being relatively-close to the take-off speed of the take-off rollers 1 and 2 and the rocker arm 5 remaining practically motionless. This equilibrium is not disturbed until owing to irregularities, such as changes in the speed of rotation or stoppage of the packing material when there are no longer any articles to be packed, the take-off speed of the packing material undergoes a sudden major change.

The storage system of the rocker arm 5 can be adapted in a simple manner by the ar rangement of the torsion spring 1 7 on the brake lever arm 14.

Claims

1. Device for controlling the brake for packing material and acting on the reel shaft and having a flexibly mounted brake lever arm arranged to be adjustable by means of the rocker arm which is actuated by the packing material and which is mounted to the side of the reel in such a way that by means of a hub on a fixed shaft it can be pivoted outwards as far as a stop and which is provided with guide rollers over which the strip of packing material, in conjuction with fixed deflector rollers adjacent thereto, is drawn off the reel by the take-off rollers of the packing machine, characterized by the fact that the ub 5a of the rocker arm 5 is provided with an external bearing ring 5e surrounded by a housing part 8 and supported by means of spring-loaded discs 9 against both sides of the said housing part 8, the periphery of which has a limiting groove engaged by a fixed stop lever 1 2 and at the bottom of which a radial projection 8a is provieded which bears a contact pressure roller 8b resting on the brake lever arm 14.

2. Device in accordance with Claim 1, characterized by the fact that the bearing ring 5e contains a pin 1 3 which is coaxial with the shaft 4 and which on both sides engages an appropriate slot 9a in the discs 9.

3. Device in accordance with Claims 1 and 2, characterized by the fact that the radial projection 8a on the housing part 8 acts on the free end of the brake lever arm 14 via a torsion spring 1 7.

4. Device in accordance with Claim 1 substantially described with reference to the accompanying drawings.