GB2277130A - Control circuit for glassware forming machine - Google Patents

Abstract

A safety circuit for control of pneumatic mechanism in a glassware forming machine comprises a source of compressed air, a control valve 6 actuated by a solenoid operated pilot valve 16 and, upstream of the valve 6, a manually or solenoid operated on-off valve 38 and an air restrictor 40 in parallel with the valve. When the valve 38 is switched off, air is supplied at a reduced flow rate to the mechanism via the valve 6. <IMAGE>

Description

Control Circuit for Glassware Formina Machine This invention is concerned with control circuits for glassware forming machines. Glassware forming machines of the Individual Section (I.S.) type normally comprise a number of sections mounted along side each other which are arranged to operate out of phase with each other to manufacture glass containers. Each section comprises a number of pneumatically operated mechanisms, and the machine comprises a supervisory computer which provides a series of signals to pneumatic circuits operating the mechanism to cause the mechanism to operate in timed sequence.

From time to time it is necessary to cause a section to cease operating so that the mechanisms can be adjusted, for example to make ware of a different size, or so that the mechanism can be repaired.

Conventionally, cessation of operation of a mechanism is effected, as will be described later, by the use of a manually operated lever which sets a pilot valve of each pneumatic circuit to be fixed in an open position, but this method of operation has certain disadvantages which will be discussed later.

It is an object of the present invention to provide an improved circuit for use in glass forming machinery.

The present invention provides a control circuit for the pneumatic operation of mechanisms in a glassware forming machine in which the mechanism is connected by a supply line to a supply of compressed air through a control valve, which control valve is operated by pilot air supplied by a pilot line from a source of pilot air, which supply is controlled by a solenoid operated pilot valve in the pilot line which valve is operated at the desired time in the operation of the machine by an electrical control system of the machine characterized in that a manually operable on-off valve is positioned in the supply line between the control valve and the supply, and an air restrictor bypasses said on-off valve, so that when the on-off valve is in its normal position air is supplied through the supply line to the mechanism to operate the mechanism normally, while when the valve is in its off position, air is supplied to the mechanism through the restrictor at a reduced flow rate.

Preferably in a circuit according to the invention the on-off valve is solenoid operated, the solenoid being connected to a supervisory computer of the forming machine.

There now follows a description of a known control circuit and of a control circuit embodying the invention.

Figure 1 shows, diagrammatically, part of an existing pneumatic control circuit for operating a mould opening and closing mechanism of a glassware forming machine.

Figure 2 shows, diagrammatically, a similar control circuit embodying the invention.

The mould opening and closing mechanism comprises a piston and cylinder device 2. High pressure air for effecting closing movement of the moulds is supplied above the piston of the device 2 through a supply line 4. A control valve 6 is positioned in the supply line, and also an exhaust speed control device 8 comprising a restrictor 10 and a one way valve 12. The control valve 6 is operated by pilot air supplied through a pilot line 14 from a source of pilot air.Supply of pilot air is controlled by a solenoid operated pilot valve 16 in the line 12, the valve 16 being operated by electrical signals passed through a line 18 to its solenoid from a supervisory computer of the machine: Low pressure air for effecting opening movement of the moulds is supplied through a similar arrangement comprising a supply line 24 connected to the supply of low pressure air, a control valve 26, an exhaust control device 28, and a pilot valve 36 in the pilot line 14 also connected to the line 18.

The operation of the circuit on the supply of appropriate electrical signals through the line 18 will be clear. When manual operation is desired, for example to replace the moulds in the mould opening and closing mechanism a mechanical cam (not shown) operated by a hand lever is set by the operator which holds the appropriate pilot valve in an open position: thus to ensure that the mould mechanism is in an open position the valve 36 would be so operated, while the valve 16 would be allowed to remain closed.

It will be understood that all the various pneumatically operated mechanisms of the glassware forming machine have a similar circuit, and to achieve a desired state of the machine to perform a particular operation, the operator will have to operate the mechanical cams of a number of the pilot valves in a predetermined sequence. It is not possible to support the control of the pilot valves from the supervisor computer of the machine.

Conventionally all the pilot air solenoid valves in a glassware forming machine are mounted in a valve block at one end of the machine, and consequently all the hand levers are positioned at the valve block, which is very inconvenient in a multi section machine if an operator wishes to deal with a mechanism remote from the valve block, e.g. at the blow side of the machine. A further disadvantage is that the possibility of an operator operating one of the hand levers during the automatic running of the machine cannot be avoided.

Figure 2 shows diagrammatically, part of a control circuit embodying the invention.

This circuit is exactly the same as the circuit of Figure 1 except that, in the high pressure supply line 4 is inserted an on/off control valve 38 in parallel with a restrictor 40, and in the low pressure supply line 24 is inserted an on/off control valve 42 in parallel with a restrictor 44. The two control valves 38 and 42 are solenoid operated and are connected by lines 46,48 to the supervisory computer.

In this circuit, no manual means is provided for overriding the pilot valves 16 and 36. If access to a particular mechanism is required, e.g. to the mould opening and closing mechanism to change the moulds, the supervisory computer is instructed that such access is required, and operates to send the necessary signals to the appropriate on/off control valves, similar to the valves 38 and 42.

When one of the valves is put into its off position, it does not eliminate the supply of compressed air but, as the air has to pass through the restrictor valves in parallel with the on-off valves, it reduces the flow of the air supplied to the various mechanisms, to obtain, as desired, slow movement of the mechanism to its desired end position. Of course, in the desired end position, the mechanism is held in position under full prssure, as the restrictor valves 40,44 only reduce the rate of flow of air, not the ultimate pressure. As the on-off control valves are biased by spring pressure into a closed position, the system is fail safe to any electrical failure of the supervisory computer, as even on such failure, air at reduced flow will be provided to the mechanisms which will therefore only move, if at all, slowly. Further, as putting the valves into a condition to prepare the machine for mechanical attention is effected through the supervisory computer, the arrangement avoids the possibility of the operator inadvertently disabling a pilot valve while the machine is in operation.

Claims (2)

1. A control circuit for the pneumatic operation of mechanisms in a glassware forming machine in which the mechanism is connected by a supply line to a supply of compressed air through a control valve, which control valve is operated by pilot air supplied by a pilot line from a source of pilot air, which supply is controlled by a solenoid operated pilot valve in the pilot line which valve is operated at the desired time in the operation of the machine by an electrical control system of the machine characterized in that a manually operable on-off valve is positioned in the supply line between the control valve and the supply, and an air restrictor bypasses said on-off valve, so that when the on-off valve is in its normal position air is supplied through the supply line to the mechanism to operate the mechanism normally, while when the valve is in its off position, air is supplied to the mechanism through the restrictor at a reduced flowrate.

2. A control circuit according to claim 1 wherein the on-off valve is solenoid operated, the solenoid being connected to a supervisory computer of the forming machine