GB2198614A

GB2198614A - Emergency stop system

Info

Publication number: GB2198614A
Application number: GB08628570A
Authority: GB
Inventors: Ian Douglas Shepherd
Original assignee: Individual
Current assignee: Individual
Priority date: 1986-11-28
Filing date: 1986-11-28
Publication date: 1988-06-15
Also published as: GB8628570D0

Abstract

An emergency stop system comprises a remotely controllable primary actuator 18 operable, for example, to open a cut-off switch 17 in a power supply to a machine or to close a valve in response to a remotely transmitted radio, sonic or ultrasonic signal. A remote transmitter 20 is arranged to be carried about the person. Each individual person carries a respective portable transmitter 20 whereby each individual is always in reach of a means of cutting off power, or the supply of a fluid medium, for example, in the event of an accident or of a hazardous situation arising. <IMAGE>

Description

DESCRIPTION OF INVENTION Title: "Emergency stop system" THIS INVENTION relates to an emergency stop system for stopping a machine or group of machines in, for example, a factory or other industrial installation in an emergency, such as when a workman has been injured or is in danger of being injured by such a machine.

A conventional emergency stop system utilises a pushbutton switch provided at a strategic location and operable manually to terminate supply of power to the respective machine or group of machines. More elaborate, conventional, emergency stop systems, as used in factories and the like installations, comprise a plurality of push-button switches located in respective fixed strategic positions in the factory or manufacturing plant concerned, with a view to ensuring, so far as possible, that there is always an emergency stop button disposed relatively closely to the site of a potential accident and that, wherever an accident occurs or is seen to be about to occur, there will be a relatively high probability that someone working in the respective factory area will be reasonably close to an emergency stop button and will, hopefully, be able to operate the same in order to prevent or minimise the severity of any accident.

Such conventional emergency stop systems can be applied to electrically powered equipment, or to equipment powered in some other way, such as by compressed air. Similar systems are also used in installations where fluids are supplied through pipe lines, for example in chemical processing plants, with the emergency stop buttons controlling power-operated valves whereby supply of the respective fluids can be terminated immediately in the event of an emergency.

However, known emergency stop systems have various disadvantages.

Thus, it is difficult, if not impossible, to determine the best location for the emergency stop buttons before these are fixed in place and careful analysis of a long series of accidents and incidents may be necessary to reveal deficiencies in such location when the installation has been set up.

Wherever the emergency stop buttons are located, there is always the problem that an individual seeing a dangerous situation or finding himself in one must remember the location of the nearest emergency stop button and move to it before he can operate it so that there is inevitably some delay in operation of an emergency stop button.

Furthermore, it is frequently the case that a workman only becomes aware that he is in a dangerous situation when he, or his clothing, has become trapped in a machine and in this case the trapped individual may not himself be in a position to reach and operate the nearest emergency stop button and consequently the machine may not be stopped until some other person notices the situation and operates an emergency stop button.

It is an object of the present invention to provide an improved emergency stop system which avoids the above disadvantages.

According to one aspect of the invention there is provided an emergency stop system comprising a primary actuator which is operable to bring about a safe condition in manufacturing plant, or in other locations in which automatically driven machinery is utilised, or where means is used for supplying fluid or flowable material to desired locations, or in the like situations, the system comprising a receiver associated with the primary actuators and arranged to operate the primary actuator on receipt of a predetermined signal, and a remote, personnel-operable transmitter capable of transmitting such a predetermined signal to said receiver.

In the accompanying drawings: FIGURE 1 is a schematic diagram illustrating a conventional emergency stop system, and FIGURE 2 is a schematic diagram illustrating the operation of an emergency stop system embodying the present invention.

Referring to Figure 1, there is shown a factory installation in which a plurality of machines 10 are supplied with power, for example electrical power, from a common power distribution system 12. The machines 10 may be electrically driven machines and the power distribution system 12 may comprise an electrical distribution board or panel. However, the machines 10 may be, for instance, pneumatically operated machines powered by compressed air, with the power distribution system 12 incorporating a compressor and valve, manifold, reservoir etc., for supplying compressed air to the machines 10. Likewise, the machines 10- may be hydraulically operated, with the system 12 incorporating a fluid pump, pressure accumulator etc.The emergency stop system is illustrated as comprising an electrical circuit 14 connected with the power distribution system 12, the circuit 14 including a plurality of emergency stop switches 16 which are connected in series so that operation of any switch 16 will open the circuit 14 and will consequently terminate the supply of power to the machines 10. Typically, the opening of the circuit 14 operates a relay which de-energises the machines 10 or which cuts off the power supply to the compressor motor or pump motor, in the case of a compressed air or hydraulic system and/or operates electrically operated valves to terminate supply of compressed air or hydraulic medium to the machines 10.Whatever the details of the conventional system, the significant point, for purposes of the present description, is that the individual switches 15 are provided at fixed locations in the premises in which the machines 10 are installed.

Referring now to Figure 2, which illustrates an emergency stop system embodying the invention, the system may be, as illustrated, substantially identical with the known system illustrated in Figure 1 except in the respects noted below, the system incorporating machines 10, power distribution system 12, circuit 14 and fixed push-button emergency stop switches 16, as before.

The system of Figure 2 differs, however, from that of Figure 1 in that there is also incorporated in the circuit 14, in series with the switches 16, a switch, indicated schematically at 17, which is arranged to be opened by a receiver 18, adapted to receive a pre-determined signal from any of a plurality of transmitters 20, (only one of which is shown). The signal transmission system employed is preferably one requiring no physical connection between the transmitters 20 and the receiver 18, for example, relying upon transmission of radio waves or sonic or ultra-sonic signals. Thus, in one embodiment, each person involved in the factory installation carries a respective simple radio transmitter 20 adapted, when operated, to transmit to the receiver 18 a signal causing the latter to open the receiver switch 17 and break the circuit 14.The receiver 18 may be simply arranged to respond to a radio signal of a particular frequency, with all of the transmitters 20 being arranged to transmit signals of that frequency, but more discriminatory systems are preferably employed, wherein, for example, the respective radio signals are modulated in a predetermined manner, thereby to avoid or minimise the likelihood of accidental operation of the emergency stop system by radio frequency interference. As noted, the system may alternatively use, for example, sonic or ultra-sonic signals, but again, in order to avoid accidental operation of the emergency stop system by acoustic noise, it is desirable for the receiver to be receptive only to, for example, a predetermined sequence of sonic or ultra-sonic signals. Details of such systems will be evident to those skilled in the art and will not be elaborated upon here.The transmitters 20 may take various forms, depending upon the nature of the activity in the installation concerned, but it is believed that it will generally be appropriate for transmitter 20 to take the form of a unit small and light enough to be carried in the breast pocket of a shirt, overall or the like, the transmitter being actuable by a manually operable switch, such as a push-button switch or a slide switch (the latter may be preferable to prevent accidental operation). Alternatively, the transmitter, carried in a pocket by each individual, might be connected by flexible conductors with an operating switch disposed somewhere else on the individual's body for example incorporated in a wrist strap, in which case the switch may conveniently be a squeeze type pressure switch. In certain cases it may be preferable to have a respective such switch on either side of the wrist strap, simultaneous operation of both switches being necessary to operate the transmitter, thereby minimising the risk of accidental operation of the system.

Whilst the fixed emergency stop switches 16 may be rendered redundant to some extent by the portable transmitters 20, the fixed switches 16 are preferably retained to increase safety and to satisfy safety regulations.

Furthermore, while for simplicity, only one receiver 18 with corresponding switch 17 is illustrated, a plurality of receivers 18 with respective switches 17 incorporated in the circuit 14, and each responsive to the same predetermined signal, may be incorporated in the system, the receivers 18 being disposed at desired spaced-apart locations according to the area to be served by the system and the transmitting range of transmitters 20.

Each transmitter 20 could be multi-channel so that several separate emergency stop systems could be operated individually. The transmitters could be incorporated into a conventional paging or personal communications system.

The system described with reference to Figure 2 renders the siting of the conventional emergency stop incorporated in the system less critical than hitherto, and allows an individual to operate the emergency stop system sooner, once a dangerous situation is perceived, than hitherto. Furthermore, an individual trapped in a dangerous situation will in many cases be able to operate the emergency stop system himself, by means of the transmitter 20 carried on his person. Whilst a major application of the present invention is in manufacturing and industrial installations, it will be appreciated that a system embodying the invention may be used, for example to provide such a facility for machinery used in sporting or entertainment activities.

Claims

1. An emergency stop system comprising a primary actuator which is operable to bring about a safe condition in manufacturing plant, or in other locations in which automatically driven machinery is utilised, or where means is used for supplying fluid or flowable material to desired locations, or in the like situations, the system comprising a receiver associated with the primary actuators and arranged to operate the primary actuator on receipt of a predetermined signal, and a remote, personnel-operable transmitter capable of transmitting such a predetermined signal to said receiver.

2. An emergency stop system according to claim 1 wherein said remote, personnel operable transmitter is adapted to be carried about the person.

3. An emergency stop system according to claim 1 or claim 2, wherein said remote transmitter is adapted to transmit said predetermined signal in the form of a radio signal.

4. An emergency stop system according to any preceding claim wherein said remote transmitter is adapted to transmit said predetermined signal in the form of a sonic or ultrasonic signal.

5. An emergency stop system according to any preceding claim, including a plurality of such transmitters adapted to be carried by respective workpersons, and each operable to generate such a predetermined signal to said receiver.

6. An emergency stop system substantially as herein described with reference to, and as shown in, Figure 2 of the accompanying drawings.

7. Any novel feature or combination of features described herein.