GB2204267A

GB2204267A - Controlling article demoulding

Info

Publication number: GB2204267A
Application number: GB08714678A
Authority: GB
Inventors: Gerard Kennedy
Original assignee: CHAVILLE Ltd
Current assignee: CHAVILLE Ltd
Priority date: 1987-05-05
Filing date: 1987-06-23
Publication date: 1988-11-09
Anticipated expiration: 2007-06-23
Also published as: BE1000029A6; GB8714678D0; IE871126L; GB2204267B

Abstract

Plastics in a granular or powder form is introduced into a mould at a moulding station 2 to 5 or 9 to 11 from which a moulded plastics article is delivered by a respective transfer device 7 onto a conveyor 1 or 1a. The delivery of plastics articles onto the conveyors is controlled by photoelectric units 15, 16, 17 and optical proximity switches 20 to prevent a plastics article from one station colliding with an article from another station. When a plastics article passes between one of the transmitters 15a, 16a, 17a and its associated receiver 15b, 16b, 17b an output signal is sent to the control system which prevents the transfer mechanism 7 from dropping an article onto the conveyor until a preset time, which is typically 10 seconds, has elapsed to allow the plastics article already on the conveyor to clear the station. <IMAGE>

Description

A MOULDING METHOD AND APPARATUS The invention relates to a method of moulding plastics articles, to plastics articles moulded by the method and to apparatus for carrying out the method.

According to the invention there is provided a method of moulding plastics articles comprising the steps of: introducing plastics in a granular or powder form into a mould at a moulding station, forming the plastics into a desired shape of article in the mould, opening the mould, unloading the moulded plastics article from the mould, lifting the plastics article up above the level of a conveyor, moving the article across until it is positioned over the conveyor onto which plastics articles from a number of moulding stations are delivered, and delivering the plastics article onto the conveyor, the method including the steps of preventing the delivery of a plastics article onto the conveyor for a preset time when a plastics article from a preceding moulding station in the line passes a preset point on the conveyor to prevent the article colliding with another plastics article on the conveyor, and disabling the cut-out after the preset time has elapsed to allow the article to be delivered onto the conveyor.

In one embodiment of the invention the preset position is a distance X metres from the conveyor, the conveyor is driven at Y metres per second and the preset time is greater than X/Y by a safety margin of at least one second, and preferably at least two seconds. The belt may, for example, be driven at a half metre per second, the preset position may be four metres upstream of the unload station and the preset time may be approximately ten seconds.

In one embodiment of the invention the method includes the step of preventing the release of the article onto the conveyor until the article has reached a preset level above, but adjacent to the conveyor.

In another aspect the invention provides an apparatus for carrying out the method according to the invention including means for unloading and delivering a plastics article from a moulding station onto a conveyor, product sensing means provided at a preset position on the conveyor in advance of the moulding station, and control means for controlled unloading and delivery of the article onto the conveyor, the control means comprising a time delay means set by a product passing the product sensing means to disable operation of the product delivery means and prevent delivery of the plastics article onto the conveyor until the preset period has elapsed to prevent the plastics article being dropped onto the conveyor until a product from an upstream moulding station has passed.

In one embodiment of this aspect of the invention the sensing means comprises a photoelectric transmitter and receiver arranged on opposed sides of the conveyor at a preset position upstream of the moulding station.

In a preferred embodiment of this aspect of the invention the control means includes a product proximity sensing means to prevent the product being dropped onto the conveyor until it has reached a preset level above, but adjacent to the conveyor.

The invention will be more clearly understood from the following description thereof given by way of example only with reference to the accompanying drawings in which: Fig. 1 is a schematic perspective view of a typical moulding apparatus for carrying out the method of the invention, Fig. la is a side view of portion of the apparatus of Fig. 1, Fig. 2 is a flow chart illustrating part of the method of moulding according to the invention; Fig. 3 is a block diagram of a control system for carrying out the method of the invention; Fig. 4 is a circuit diagram of a sequence controller forming part of the system of Fig. 2, Fig. 5 is a circuit diagram of an auxiliary power supply and product detection and delay timer forming portion of the system of Fig. 2; and Fig. 6 is a circuit diagram of an input output display portion of the system of Fig. 2.

Referring to the drawings the method of moulding according to the invention is described with reference to a multistation moulding apparatus which is diagrammatically illustrated in Figs. 1 and la. The apparatus in this case comprises two conveyors, 1, la, one of which 1, is associated with four sequentially arranged moulding stations 2,3,4,5. There are three sequentially arranged moulding stations 9,10t,11 associated with the second conveyor la. Moulded plastics articles are removed from a mould and delivered onto the conveyor 1 by transfer devices 7 travelling on rails 8.

The method according to the invention comprises the steps of introducing plastics in a granular or powder form into a mould at one of the moulding stations, forming the plastics into a desired shape of article in the mould, opening the mould and transferring the moulded article from the mould onto the respective conveyor 1, la using the transfer mechanism 7. To transfer the moulded article from a mould onto a conveyor the mould is first opened and then the article is unloaded from the mould and lifted up above the level of the conveyor 1 by the transfer mechanism 7. The transfer mechanism 7 is then moved across the rail 8 in the direction of the arrow A in Fig. 6 until the plastics article is positioned over the conveyor 1.It will be appreciated however that as plastics articles are delivered onto the conveyor 1 from a number of different moulding stations there is substantial risk that a plastics article from one of the moulding stations could be delivered onto the conveyor 1 in such a way as to interfere or collide with a plastics article delivered onto the conveyor by another moulding station. Thus, the method includes the step of preventing the delivery of a plastics article onto the conveyor for a preset time when a plastics article from a preceding moulding station in the line passes a preset point on the conveyor to prevent the article colliding with another plastics article on the conveyor. The cut-out is disabled after the preset time has elapsed to allow the article to be delivered onto the conveyor.

In the method of the invention the presence of a plastics article on the conveyor 1 is sensed by a number of photoelectric units 15,16,17 arranged at preset locations along the conveyor 1. Each of the photoelectric units comprises a transmitter respectively 15a, 16a, 17a, and an associated receiver 15b, 16b, 17b on opposed sides of the conveyor, a plastics article passing between a transmitter and receiver causing an output signal to be sent to a control system which prevents the transfer mechanism 7 from dropping the finished plastics article onto the conveyor 1 until a preset time has elapsed.The preset position in which the photoelectric units are positioned is in this case approximately 4 metres upstream of the respective unloading stations of the moulding stations so that if the conveyor belt 1 is driven at a half metre per second at least 8 seconds is required to ensure that the article clears the unload station before the next article is delivered onto the conveyor. In this case a safety factor of 2 seconds is incorporated so that the transfer mechanism at the moulding station downstream of the photoelectric unit is disabled from delivering the plastics article onto the belt until a period of ten seconds has elapsed from the time at which the previous article has passed the photoelectric sensors upstream of the unloading station.

To prevent damage to articles when they are delivered from the unloading station onto the conveyor 1 the moulding method of the invention includes the step of preventing the release of the article onto the conveyor until the article has reached a preset level above, but adjacent to the conveyor 1. Optical proximity switches 20 are therefore provided at each unloading station to sense when the plastics article is at the desired level above the conveyor 1, release of the plastics article from the transfer mechanism 7 onto the conveyor 1 being prevented until the proximity switch has been set.

Referring now to Fig. 2 the method of moulding according to the invention will be readily appreciated. The method includes the step of moulding the plastics article, removing the plastics article from the mould and transferring it up and along the rail 8 using the transfer mechanism 7, this step is generally indicated by the reference numeral 25 in Fig. 2. When the transfer mechanism 7 has travelled to a position above the conveyor 1 the control system is interrogated to see if the photoelectric receiver upstream of the unloading station has been set indicating that a product has passed through the downstream photoelectric unit and if so, delivery is delayed for ten seconds until the plastics article from the downstream moulding station has cleared the present moulding station.When the ten seconds have elapsed or the photoelectric sensor has not been set the transfer mechanism 7 drops the plastics article down towards the conveyor 1 as indicated generally by 26 in Fig. 1. The control system then checks to see if the optical proximity switch 20 associated with the unload station has been set.

This is only set when the plastics article has travelled downwardly sufficient distance to allow the article to be transferred onto the conveyor 1 without damage. When the optical proximity switch 20 is set the transfer mechanism 7 is stopped as indicated by the reference numeral 27 and the chuck holding the plastics article in the transfer mechanism 7 is released to allow the plastics article to drop onto the conveyor 1. The transfer mechanism 7 is then retracted as indicated by the reference numeral 29 and the procedure is repeated.

The block diagram of the control system to effect the method and steps described with reference to Fig. 1 is illustrated in Fig. 3. The control system comprises a system sequence controller 30 of conventional construction which will not be described in detail, a transfer mechanism control 31, a product detection and delay timing circuit 32 and an input/output display unit 33 which is driven by the product detection and delay timing unit 32 and the transfer mechanism control circuit 31. The product detection and delay timing circuit 32 is powered by an auxiliary power supply 33.

The transfer mechanism control circuit is illustrated in more detail in Fig. 4 and includes the optical proximity switch 20. The product detection and delay timing circuit 32 is illustrated on the right hand side of Fig. 5 and includes a coil timer 35 and a photoelectric transmitter 36 and photoelectric receiver 37 associated with the respective photoelectric sensors 15,16,17. The auxiliary power supply circuit 33 is illustrated in more detail on the left hand side of Fig. 5. Input and output display is provided by four LED'S as illustrated in Fig. 6, one, 38 associated with the unloading of a mould, another, 39, associated with the lifting of a plastics article up above the level of the conveyor, a third 40 to indicate when the transfer mechanism is travelling down to deliver the plastics article onto the conveyor and a fourth, 41 to indicate when the transfer mechanism has reached the level at which the product may be dropped onto the conveyor.

Claims

1. A method of moulding plastics articles comprising the steps of: introducing plastics in a granular or powder form into a mould at a moulding station, forming the plastics into a desired shape of article in the mould, opening the mould, unloading the moulded plastics article from the mould, lifting the plastics article up above the level of a conveyor, moving the article across until it is positioned over the conveyor onto which plastics articles from a number of moulding stations are delivered, and delivering the plastics article onto the conveyor, the method including the steps of preventing the delivery of a plastics article onto the conveyor for a preset time when a plastics article from a preceding moulding station in the line passes a preset point on the conveyor to prevent the article colliding with another plastics article on the conveyor, and disabling the cut-out after the preset time has elapsed to allow the article to be delivered onto the conveyor.

2. A method as claimed in claim 1 wherein the preset position is a distance X metres from the conveyor, the conveyor is driven at Y metres per second and the preset time is greater than X/Y by a safety margin of at least one second, and preferably at least two seconds.

3. A method as claimed in claim 2 wherein the belt is driven at a half metre per second, the preset position may be four metres upstream of the unload station and the preset time may be approximately ten seconds.

4. A method as claimed in any preceding claim wherein the method includes the step of preventing the release of the article onto the conveyor until the article has reached a preset level above, but adjacent to the conveyor.

5. A plastics article whenever made by the method of any preceding claim.

6. An apparatus for carrying out the method of any of claims 1 to 4 including means for unloading and delivering a plastics article from a moulding station onto a conveyor, product sensing means provided at a preset position on the conveyor in advance of the moulding station, and control means for controlled unloading and delivery of the article onto the conveyor, the control means comprising a time delay means set by a product passing the product sensing means to disable operation of the product delivery means and prevent delivery of the plastics article onto the conveyor until the preset period has elapsed to prevent the plastics article being dropped onto the conveyor until a product from an upstream moulding station has passed.

7. Apparatus as claimed in claim 6 wherein the sensing means comprises a photoelectric tran#mitter and receiver arranged on opposed sides of the conveyor at a preset position upstream of the moulding station.

8. Apparatus as claimed in claim 6 or 7 wherein the control means includes a product proximity sensing means to prevent the product being dropped onto the conveyor until it has reached a preset level above, but adjacent to the conveyor.

9. A method for moulding substantially as hereinbefore described, with reference to the accompanying drawings.

10. An apparatus substantially as hereinbefore described, with reference to the accompanying drawings.'