1. Field of the Invention
This invention relates to a feeding apparatus. More specifically, the invention relates to a feeding apparatus for feeding a material from a material supply to a further apparatus, particularly to a packaging apparatus.
2. Description of the Prior Art
Packaging apparatus is usually fed from a supply of packaging material, which supply comprises a core upon which the material is wound. Usually the material is in the form of a sheet.
Problems can arise when the material supply is exhausted. When this happens it is necessary to stop feeding the material to the packaging apparatus while the material supply is replenished. This procedure is inefficient because it causes the operation of the packaging apparatus to be interrupted at least for the time it takes to replenish the material supply.
The problem is even more acute with certain types of packaging apparatus, such as packaging apparatus for producing blister packs. In this apparatus the blisters are formed in the material by the application of heat and the amount of heat delivered to the material is carefully controlled. When the material supply is interrupted the material in the packaging apparatus stops moving and becomes overheated, which causes distortion of the material. It may take up to 20 minutes to re-synchronise the apparatus after the feed of the material has been restarted.
One way to solve this problem is to provide a feeding apparatus for the packaging apparatus which includes a storage buffer for the material. This enables the material to be fed to the packaging apparatus from the buffer when the material supply is changed.
A typical storage buffer is shown in U.K. Patent No. 1244066, owned by Industrie-Companie Kleinweffers Plasticmachinen GMbH & Co. K.G. In this specification the storage buffer comprises a plurality of fixed rollers disposed below a plurality of movable rollers. The sheet material is wound alternately between the fixed and movable rollers. The buffer has a sheet material inlet and a sheet material outlet.
When there is an interruption in the feed of material to the inlet, material can still be drawn from the outlet by moving the movable rollers towards the fixed rollers.
The movable rollers are mounted to a carriage which is driven towards and away from the fixed rollers by a hydraulic ram.
Another example of a storage buffer is shown in U.K. Patent Application early publication No. 2168038A, applied for by Harris Graphics Corporation.
In this specification the fixed rollers are arranged at the same level as the movable rollers, and the movable rollers are movable horizontally towards and away from the fixed rollers. The movable rollers are mounted to a carriage which is, movable by means of a drive motor.
In U.K. Patent Application early publication No. 2156319A, applied for by Focke & Co, a further example of storage buffer is shown. In this specification the movable rollers are movable in an arcuate path by a drive motor. This, arcuate path can lead to additional problems in controlling the tension in the material.
The movable rollers are mounted to a carriage in the form of a roller arm. The roller arm is provided with a toothed segment which engages a pinion on the drive motor thereby causing pivotal movement in the roller arm so that the movable rollers move towards the fixed rollers.
In all three of the above specifications careful control is required of the movement of the movable rollers by the hydraulic ram or by the drive motor. In particular it is necessary to synchronise the rate at which the movable rollers are moved with the rate at which material is required by the further apparatus.
In practice, complicated control arrangements are needed to achieve this.
The need for this synchronisation would not be necessary if the drive motor could be dispensed with. However, in all the above specifications, the motor could not be dispensed with because otherwise there would be no way to move the rollers away from one another.
If the fixed rollers are arranged above the movable rollers then it would theoretically be possible for the movable rollers to be drawn toward the feed rollers by the tension in the material. The movable rollers could then move away from the fixed rollers by gravity alone.
However, this arrangement is not found to be practicable because it causes non-uniform tensioning of the sheet material in the storage means. This can upset the uniform feed to the further apparatus and can even cause the material to stretch or break.
Other apparatus is described in U.K. Patent Nos. 1402079 and 1554696, European Patent No. 37752, U.K. Patent Application early publication Nos. 2142609A and 2056953A, and European Patent Application early publication No. 139088A.