GB2285423A

GB2285423A - Apparatus for processing workpieces

Info

Publication number: GB2285423A
Application number: GB9400139A
Authority: GB
Inventors: Clive Douglas Hatcher
Original assignee: WR Grace and Co Conn; WR Grace and Co
Current assignee: WR Grace and Co Conn; WR Grace and Co
Priority date: 1994-01-06
Filing date: 1994-01-06
Publication date: 1995-07-12
Also published as: GB9400139D0

Abstract

A processing apparatus comprising a conveyor (2) for carrying workpieces (8) from a processing device (1) through a heating process (5). The conveyor (2) has a drive independent of the processing device (1) such that, if the processing device stops operating the conveyor still continues to move the workpieces (8) through the heating process (5) thus preventing them from being damaged. <IMAGE>

Description

Apparatus for Processions Workpieces The invention concerns assembly line production processes which comprise a heating stage. In an assembly line process such as those involving heating of workpieces as they pass along the line, problems can arise if a fault occurs such that the supply of objects is reduced or stopped.

If a workpiece spends a prolonged period of time in the heating section, then the workpiece can overheat and be so damaged as to be unusable. It has been suggested that in such an event the heater should be turned off to prevent such damage. However for heating systems such as infra-red heating and convection heating there is a considerable delay between switching the heater or oven off and an acceptable drop in temperature.

In WO 92/09397 it is suggested that induction heating can be used in this situation because of its rapid response to a disconnection of the power supply. It goes on to describe the use of a closed-loop temperature control system which monitors the temperature of closures being heated and controls the current flowing though the heating coils. This serves as a means for controlling the temperature at a preset level but also acts as an emergency cut out if the assembly line stops, so that the temperature of the now stationary closures does not rise and damage them.

It is an object of the present invention to avoid the need for complicated control equipment ana temperature sensing means, and to avoid disconnecting the heating device in the event of the assembly line being shut down. This enables the passage of the workpiece through the heater to be maintained. By separating the carrying means (for carrying the object through the heater) from the rest of the production line, workpieces from the previous stage are passed onto the heater transfer means which runs independently of the previous stage. Therefore if that feed means stops, or if the previous stage fails, workpieces will stop being fed onto the transfer means but those already there will continue through the heater onto the next stage after normal heating.

Accordingly the invention provides an apparatus for processing workpieces comprising a processing means for processing workpieces, a conveyor for carrying said workpieces from the processing means through heating means downstream of the processing means, means for transferring workpieces from the processing means to the conveyor, and drive means to drive said conveyor and independent of the processing means to ensure that workpieces continue to pass through the heating means after the flow of workpieces in the processing means has stopped for any reason.

The apparatus in accordance with the present invention, and its method of operation will now be described, by way of example only, with reference to the accompanying drawings, in which: Fig. 1 is a perspective view of the preferred embodiment of the present invention showing a section of an assembly line for lining can ends then passing them onto a conveyor through a heater and onto a stacking and packing device; Fig. 2 is a sectioned perspective of the cooling and packing chute.

With reference to Figure 1, a description of an assembly line comprising a heater will now be described. In this example a part of an assembly line for producing ends for cans is described. Before can ends 8, which may for example be of aluminium or more preferably of steel, can be used they are lined with a sealant to provide an effective seal when the can end is crimped onto the can itself. This lining is applied in a lining machine 1 which passes the can ends to the heater 6 to dry and if necessary cure the lining compound. The can ends are then cooled and packaged ready for distribution.

The lining machine for use with the present invention may, for example, be a Darex 1000 machine or a Grace 686 machine available from the Closure Equipment Centre of W. R.

Grace Limited at St. Neots, Cambridgeshire, or a Grace Mark 70 machine available from the Dewey and Almy Division of W.

R. Grace & Co. at Lexington, Massachusetts. An alternative supplier of the machinery could be the Preferred Machinery Corporation USA, of Englewood, Colorado, USA whose Model HSL6 rotary compound end liner could be used.

The lining machine produces the lined can ends at a certain rate and passes them onto the independent outfeed belt conveyor 2 which, in this case advances at a higher rate to space out the can ends, and carries the can ends through the heater apparatus.

In this embodiment the heater system 5,6 & 7 is an induction heater comprising two main parts, a heater element 6 and a generator 7 for providing the high frequency power required to drive the element. The heater element is positioned along part of the length of the out feed conveyor belt 2 to heat the can ends 8 as they pass. The heater may, for example, be a model obtained from Cheltenham Induction Heating Limited, in Cheltenham, Gloucestershire, England or as part of an outfeed conveyor from Fleetwood Systems, of St.

Albans, Hertfordshire, England.

Alternatively, any other form of heater can be used with the arrangement in accordance with the present invention, and two particularly acceptable types would be on the one hand an air convection heater and on the other hand an infra-red radiant heater.

At the end of the conveyor the can ends pass onto a magnetic re-orientation device which rotates the ends through 90 degrees so that they stand vertically on a cooling and packing chute 4 where they are held in the vertical orientation and optionally spaced apart from each other to maximise the rate of cooling. The ends are advanced by contact with continuous side belts 9 engaging the ends 8 frictionally. At the end of the chute, the ends are packaged in bundles and removed from the assembly line.

In the event of the lining machine becoming jammed or breaking down it will stop feeding ends onto the outfeed conveyor 2. The conveyor will however continue to run allowing those can ends already on the conveyor to pass through the heater as normal and onto the magnetic reorientation device 3. This avoids the problems which occur if, during a failure of the lining machine 1, the outfeed conveyor is stopped as well. The can ends 8 undergoing the heating process on the conveyor would continue to be heated and to be at least 'overcooked' and at worst melted.

By continuing the conveyor belt during a failure of the lining machine 1 all the can ends that are on the conveyor are safely passed on to the magnetic reorientation device.

Once the conveyor 2 is clear there is no danger of any damage occurring as there are no can ends in the vicinity of the heater.

Once the lining machine is cleared or repaired production can continue immediately as there is no the need to clear any can ends remaining on the out feed conveyor or to allow the heating apparatus to warm up.

There may, for example, be a detector (not shown) to detect the presence of can ends being conveyed by the belt conveyor 2. This detector can be used to trigger switching of the induction heating system from its standby configuration to its running configuration only when can ends are present on the conveyor belt, thereby allowing the induction heating system to operate in the standby mode except when the higher heat output for can end drying is required.

The can end detector system may, furthermore, be associated with a timer to shut off the power altogether if, after a predetermined time interval (for example one minute) no can end has been detected, thereby suggesting that there is a long term shut down in progress.

Equally, there may be a jam detector (not shown) associated with the cooling chute 4 to detect any lack of can ends downstream of the stacker 3, indicative of a jam at the stacker. Preferably such a jam detector will then close down the lining machine 1, and the system in accordance with the present invention will allow any can ends on the conveyor 2 to clear the heating station 6 without overheating.

If desired, means may be provided in order to ensure that in the event of a jam at the stacker 3 any surplus can ends from the conveyor 2 can be ejected into an overflow receptacle such as a box (not shown) from which the correctly heated can ends can later be recovered to avoid the need for scrapping them.

Claims

1. An apparatus for processing workpieces comprising a processing means for processing workpieces, a conveyor for carrying said workpieces from the processing means through heating means downstream of the processing means, means for transferring workpieces from the processing means to the conveyor, and drive means to drive said conveyor and independent of the processing means to ensure that workpieces continue to pass through the heating means after the flow of workpieces in the processing means has stopped for any reason.

2. An apparatus according to claim 1 wherein the conveyer is a endless belt type.

3. An apparatus according to claims 1 or 2 wherein the heating means is a high frequency induction heating device.

4. An apparatus according to any one of claims 1 to 3 wherein the speed of the belt is adjustable independently of the processing means and of any subsequent apparatus.

5. An apparatus for processing workpieces, constructed and arranged as hereinbefore described with reference to and as illustrated in Figures 1 and 2 of the accompanying drawings.