Alert system and method

Abstract

An alert system comprises a pneumatic reservoir 302, 306 having an inlet for receiving compressed gas from a mains gas supply 304, a normally open control valve 310 fluidically coupled at a first inle

Description

TECHNICAL FIELD The present disclosure relates to a pneumatic lifting system. Aspects of the invention relate to a pneumatic lifting system and a method of operating a pneumatic lifting system. The present disclosure also relates to an alert system for a pneumatic lifting system. Aspects of the invention relate to an alert system, a method of operating an alert system and a pneumatic lifting system comprising an alert system. BACKGROUND It is known to provide a pneumatic lifting mechanism to enable machine operators to manipulate various types of components from the top surface of the component. The pneumatic lifting mechanism comprises one or more pneumatic suction cups operated via a mains compressed air supply. Venturi valves provided between the mains air supply source and the suction cups receive a constant supply of high pressure air from the mains air supply on one side of the valve, and use the high pressure air to create suction air on the other side of the valve. The suction air is used to create a suction force at the suction cups to enable the suction cups to hold the components. In addition, mechanical grippers are often used as a back up to hold the component in case of an air supply failure. However, this introduces a constraint on the design of the component and reduces the ease and efficiency of assembly operations by limiting the space available for manipulation and assembly of the component. This is particularly challenging with the emergence of electric vehicles, whose components are becoming increasingly compact and space efficient. Furthermore, it is known to inform an operator of the pneumatic lifting system when there is an air supply failure. This enables the operator to perform any necessary steps to minimise the risk of damage to components. Such alerts systems are often based on separate electronic warning systems. These electronic warning systems are themselves liable to failure. It is an aim of the present invention to address one or more of the disadvantages associated with the prior art. SUMMARY OF THE INVENTION Aspects and embodiments of the invention provide a pneumatic lifting system and a method of operating a pneumatic lifting system. According to an aspect of the invention there is provided a pneumatic lifting system. The pneumatic lifting system comprises a suction cup vacuum conduit for connection to a suction cup, the suction cup vacuum conduit comprising a first section and a second section. The pneumatic lifting system further comprises a nonreturn valve located in the suction cup vacuum conduit, between the first section and the second section. In use, the non-return valve prevents the flow of air along the suction cup vacuum conduit towards the suction cup. The pneumatic lifting system further comprises a venturi valve which is fluidically couplable to a compressed air supply and the first section. The venturi valve is configured to reduce the air pressure within the suction cup vacuum conduit when compressed air is supplied to the venturi valve. The pneumatic lifting system further comprises a control valve for selectively controlling the supply of compressed air to the venturi valve. The pneumatic lifting system further comprises a control means to, in dependence on an air pressure in the second section of the suction cup vacuum conduit, change a position of the control valve. In an embodiment, the control means is configured to change a position of the control valve to stop the supply of compressed air to the venturi valve when the air pressure within the second section of the suction cup vacuum conduit is less than a predetermined threshold pressure. Advantageously, stopping the supply of compressed air to the venturi valve when a sufficient vacuum is provided in the second section of the vacuum conduit for a suction cup to suction to a component, reduces an amount of compressed air used by the pneumatic lifting system compared to a pneumatic lifting system which continuously supplies compressed air to the venturi valve regardless of the air pressure within the second section of the suction cup vacuum conduit. The production of compressed air is a process which produces large amounts of carbon dioxide, CO2. Reducing the amount of compressed air used by a pneumatic lifting system thereby reduces CO2 emissions and improves environmental sustainability. In an embodiment, when the air pressure within the second section of the suction cup vacuum conduit is more than a second predetermined threshold pressure, the control means changes the position of the control valve to restart the supply of compressed air to the venturi valve. Advantageously, this helps to maintain a suitably low air pressure or vacuum in the second section of the suction cup vacuum conduit to enable the suction cup to retain its hold on the component. Changing the position of the control valve to restart the supply of compressed air to the venturi valve enables the venturi valve to restart the production of suction air and thereby reduce the air pressure within the suction cup vacuum conduit. Advantageously, this results in a pneumatic lifting system which uses pulses or bursts of compressed air to achieve and maintain a vacuum in the suction cup vacuum conduit and the connected suction cup. The pneumatic lifting system is therefore capable of holding and manipulating a component using much less compressed air than a conventional pneumatic lifting system. Tests have shown that a pneumatic lifting system with these features uses less than 1% of the compressed air required by the prior art technology. In an embodiment, the control means comprises a valve which, in use, controls a pneumatic signal pressure to the control valve to change its state in dependence on the air pressure within the second section. Advantageously, using a valve to control the state of the control valve means that it is not necessary to measure the air pressure within the second section of the suction cup vacuum conduit. The control valve can therefore be operated without the need for further complicated electronic or mechanical systems. In an embodiment, the control means is a normally closed valve and when the air pressure within the second section is less than the predetermined threshold pressure, the control means opens to cause pneumatic signal pressure to be applied to the control valve and cause the control valve to close so as to prevent compressed air from flowing to the venturi valve. In an embodiment, the pneumatic lifting system further comprises an air tank for storing the compressed air to be supplied to the control valve. Advantageously, the air tank ensures that the pneumatic lifting system is still safe and operable in the event of a mains compressed air supply failure. Tests have shown that such a pneumatic lifting system is capable of holding a component for two or more hours when a mains air supply is interrupted by using compressed air stored in the air tank to top up the vacuum inside the suction cup vacuum conduit. Further advantageously, the ability to keep safely operating the pneumatic lifting system during a mains supply failure means that mechanical grippers are not required as a back-up system to support the component. By not requiring mechanical grippers, the constraints on the design of the components to be lifted is reduced. Further advantageously, since mechanical grippers are no longer required, the component can be held and manipulated using suction cups couplable to just a single surface, such as a top surface, of the component. This improves the ease and efficiency of assembly operations because there are no mechanical grippers to limit an available space so there is an increased freedom of movement of the pneumatic lifting system and component. The ability to hold the component by just a single surface of the component is particularly useful when assembling components that are designed to fit tightly together. In an embodiment, the pneumatic lifting system further comprises an alert valve. The alert valve comprises a normally open valve fluidically couplable to a mains air supply and the air tank, the alert valve for selectively controlling an operation of an alert means in dependence on a position ofthe alert valve. In use, an airpressure provided by the mains air supply to the alert valve causes the alert valve to maintain a closed state. When the mains air supply stops supplying compressed air, the alert valve changes position to its normally open state, causing compressed air from the air tank to flow through the alert valve and pass to the alert means to operate the alert means. Advantageously, this provides a fail-safe alert mechanism in case that the mains air supply fails and compressed air is no longer provided from the mains air supply to the pneumatic lifting system. The alert means provides the system operators with a warning that the mains air supply has failed and the pneumatic lifting system is being operated solely by air from the air tank. Since the air tank allows the pneumatic lifting system to maintain and hold a component for several hours, the alert means ensures that the system operator has adequate time to finish their assembly operation and / or place the system in a safe state where the component can cause no damage if the pneumatic lifting system is no longer able to hold the component. In an embodiment, the pneumatic lifting system further comprises a pneumatic reservoir including an accumulator between the air supply and the air tank. Advantageously, the accumulator stores compressed air which can be used to help maintain a consistent air pressure from the air supply to the air tank. In an embodiment, the pneumatic lifting system further comprises a pressure regulator provided between the air tank and the control valve. Advantageously, the pressure regulator controls a pressure of the compressed air supplied from the air tank to the control valve so that a consistent air pressure is applied to the control valve. In an embodiment, the pneumatic lifting system further comprises a normally closed second control valve fluidically couplable between the second section of the suction cup vacuum conduit and an indicating means. The indicating means may indicate to a user when the air pressure within the second section is below a third predetermined threshold pressure. When the air pressure within the second section of the suction cup vacuum conduit is less than the third predetermined threshold pressure, the air pressure causes the second control valve to open to enable compressed air to flow to the indicating means to operate the indicating means. Advantageously, this provides a fail-safe system for informing a machine operator when it is safe to lift a component using the pneumatic lifting system. The second control valve is linked to the second section of the suction cup vacuum conduit so that the second control valve may be directly operable in dependence on a pressure within the second section of the vacuum conduit. When a third predetermined threshold pressure, indicating a minimum safe pressure for lifting a component, is reached, the second control valve operates to allow compressed air to flow to the indicating means to indicate to a user of the pneumatic lifting system that it is safe to lift the component. Conversely, when the pressure within the second section of the suction cup vacuum conduit is above the third predetermined threshold pressure, signifying that the pressure is not sufficiently low to enable safe handling of the component, the second control valve is closed to prevent compressed air from flowing to the indicating means. The indicating means is therefore not activated, and so the operator of the pneumatic lifting system is aware that the pneumatic lifting system is not in a state in which it is safe to lift the component. In an embodiment, there is provided a release means for applying a positive air pressure to the second section of the suction cup vacuum conduit. The positive air pressure may have a value greater than the maximum vacuum caused by the venturi valve in the second section in order to increase the air pressure within the second section. Advantageously, the release means provides a quick and simple way to release the component when it is no longer necessary for the pneumatic lifting system to hold or manipulate the component. In an embodiment, there are a plurality of venturi valves. Each venturi valve is fluidically couplable to a respective first section of a respective suction cup vacuum conduit. The control valve selectively controls the supply of compressed air to each of the venturi valves. Advantageously, a plurality of suction cups can be operated at the same time using the same pneumatic lifting system. This enables components which are large, heavy and / or awkwardly shaped to be held and manipulated. The safety of the system is also improved by using a plurality of suction cups because, in the event of a physical fault with one suction cup, there is still at least one suction cup available to hold the component. The risk of the component falling in the event of a sudden and unexpected breakage of a suction cup is therefore reduced. According to another aspect of the invention there is provided a method for operating a pneumatic lifting system. The pneumatic lifting system comprises a suction cup vacuum conduit for connection to a suction cup, the suction cup vacuum conduit comprising a first section and a second section. The pneumatic lifting system further comprises a non-return, NR, valve located in the suction cup vacuum conduit between the first section and the second section. The pneumatic lifting system additionally comprises a venturi valve fluidically coupled to a compressed air supply and the first section, a control valve for selectively controlling the supply of compressed air to the venturi valve, and a control means. The method according to the aspect of the invention comprises providing a flow of compressed air to the control valve. The method further comprises supplying, by the control valve, the compressed air to the venturi valve. The supply of compressed air to the venturi valve causes the venturi valve to reduce an air pressure within the suction cup vacuum conduit. The method also comprises preventing, by the NR valve, the flow of air along the suction cup conduit towards the suction cup. The method further comprises changing, by the control means, a position of the control valve to stop the supply of compressed air to the venturi valve when the air pressure within the second section of the suction cup vacuum conduit is less than a predetermined threshold pressure. Advantages for aspects of the invention relating to the method for operating a pneumatic lifting system may be the same as those set out in relation to the aspects of the invention relating to the pneumatic lifting system itself. For conciseness, the descriptions of these advantages are not repeated. In an embodiment, the method further comprises changing a position of the control valve to restart the supply of compressed air to the venturi valve when the air pressure within the second section of the suction cup vacuum conduit is more than a second predetermined threshold pressure. Changing the position of the control valve is performed by the control means. In an embodiment, the method further comprises opening the control means when the air pressure within the second section is less than the predetermined threshold pressure. The control means comprises a normally closed valve and opening the control means causes pneumatic signal pressure to be applied to the control valve. The applied pneumatic signal pressure causes the control valve to close so as to prevent compressed air from flowing to the venturi valve. In an embodiment, the method further comprises applying a positive air pressure to the second section. The positive air pressure is applied using a release means. The positive air pressure has a value greater than the maximum vacuum caused by the venturi valve in the second section so as to increase the air pressure within the second section. In an embodiment, the method further comprises controlling a pneumatic signal pressure to the control valve to change the state of the control valve in dependence on the air pressure within the second section. Controlling the pneumatic signal pressure is performed by the control means, which comprises a valve. In an embodiment, the method further comprises opening the control means when the air pressure within the second section is less than the predetermined threshold pressure. The control means is a normally closed valve and opening the control means causes pneumatic signal pressure to be applied to the control valve. The pneumatic signal pressure applied to the control valve causes the control valve to close so as to prevent compressed air from flowing to the venturi valve. In an embodiment, the method further comprises storing the compressed air to be supplied to the control valve in an air tank. In an embodiment, method further comprises selectively controlling an operation of an alert means in dependence on a position of the alert valve, wherein the alert valve comprises a normally open valve fluidically couplable to a mains air supply and the air tank. An air pressure provided by the mains air supply to the alert valve causes the alert valve to maintain a closed state. When the mains air supply stops supplying compressed air, the alert valve changes position to its normally open state, causing compressed air from the air tank to flow through the alert valve and pass to the alert means to operate the alert means. In an embodiment, the method further comprises accumulating compressed air using an accumulator provided between the air supply and the air tank. In an embodiment, the method further comprises regulating a pressure of the compressed air supplied from the air tank to the control valve using a pressure regulator provided therebetween. In an embodiment, the method further comprises indicating to a user when the air pressure within the second section is below a third predetermined threshold pressure. The indicating is performed by an indicating means. A normally closed second control valve is fluidically coupled between the second section and the indicating means and, when the air pressure within the second section of the suction cup vacuum conduit is less than the third predetermined threshold pressure, the air pressure causes the second control valve to open. The opening of the second control valve enables compressed air to flow to the indicating means to operate the indicating means. In an embodiment, the method further comprises selectively controlling the supply of compressed air to each of a plurality of venturi valves where each venturi valve is fluidically couplable to a respective first section of a respective suction cup vacuum conduit. Aspects of the invention also provide an alert system for a pneumatic lifting system and a method of operating an alert system for a pneumatic lifting system. According to an aspect of the invention, there is provided an alert system for a pneumatic lifting system. The alert system comprises a pneumatic reservoir, the reservoir having an inlet for receiving compressed gas from a mains gas supply. The alert system further comprises a normally open control valve. The normally open control valve is fluidically coupled at a first inlet of the normally open control valve to an outlet of the pneumatic reservoir. The alert system further comprises a pneumatic alert means fluidically coupled to an outlet of the normally open control valve. The normally open control valve has a control inlet for receiving pneumatic signal pressure from the mains gas supply. The normally open control valve controls a supply of compressed air to the pneumatic alert means in dependence on a pressure of gas received at the normally open control valve from the mains gas supply to control an operation of the alert means. Advantageously, this provides a fail-safe mechanism for informing an operator of a pneumatic lifting system that there has been a failure in the mains gas supply. There is no reliance on a separate warning system which may also be liable to failure. In particular, the mechanical system does not rely upon any electronic components that are liable to failure. Instead, the operation of the alert means is directly dependent on the failure of the mains gas supply. Further advantageously, the alert system can quickly respond to a mains gas supply failure. The time taken to respond may simply be the time required for the control valve to change state and the time required for gas to flow from the pneumatic reservoir to the pneumatic alert means. There is no reliance upon any processing or other means which may delay the output of the alert. Further advantageously, the alert system is a passive system. That is, the alert system does not interfere with the operation of the pneumatic lifting system. The incorporation of the alert system into a pneumatic lifting system therefore does not negatively affect or interrupt the performance of the pneumatic lifting system. In an embodiment, a pressure of the mains gas supply received at the normally open control valve above a threshold value closes the normally open control valve. A pressure of the mains gas supply received at the normally open control valve below the threshold value allows the normally open control valve to open. Opening the normally open control valve fluidically connects the pneumatic reservoir to the pneumatic alert means so that the pneumatic alert means outputs an alert. Advantageously, the compressed air within the pneumatic reservoir is simply redirected to the pneumatic alert means to enable the pneumatic alert means to output an alert when there is a failure with the mains gas supply. Further advantageously, a user may be readily informed when the mams gas supply has been restored to its normal function because the pneumatic alert means will no longer be outputting the alert. When the mains gas supply is restored, the pressure of the mains gas supply received at the normally open control valve will be above the threshold level. This pressure will cause the normally open control valve to close so the pneumatic reservoir will no longer be fluidically connected to the pneumatic signal means. Since the pneumatic alert means no longer receives a supply of gas from the pneumatic reservoir, the pneumatic alert means stops outputting the alert. Further advantageously, the alert system can quickly respond to the restoration of the mains gas supply. The time taken to respond may simply be the time required for the control valve to change state such that gas is no longer able to flow from the pneumatic reservoir to the pneumatic alert means. In an embodiment, the pneumatic alert means comprises an air horn. Advantageously, the air horn is easy to operate because it merely relies upon a supply of gas to the air horn. In an embodiment, the alert system further comprises a throttle valve provided between the outlet of the pneumatic reservoir and the first inlet of the normally open control valve. Advantageously, the throttle valve enables the flow of compressed gas from the pneumatic reservoir to the normally open control valve to be controlled. This prevents too much gas being received at the pneumatic alert means and so reduces a risk of damage to the pneumatic alert means. In an embodiment, the alert system further comprises a non-return valve between the pneumatic reservoir and the mains gas supply. Advantageously, the non-return valve prevents a flow of air from the pneumatic reservoir towards the mains gas supply. In an embodiment, the alert system further comprises a suction cup vacuum conduit for connecting to a suction cup, the suction cup vacuum conduit comprising a first section and a second section. The alert system further comprises a non-return valve located in the suction cup vacuum conduit, between the first section and the second section. In use, the NR valve prevents the flow of air along the suction cup vacuum conduit towards the suction cup. The alert system also comprises a venturi valve which is fluidically couplable to the pneumatic reservoir and the first section. The venturi valve is configured to reduce the air pressure within the suction cup vacuum conduit when compressed air is supplied to the venturi valve from the pneumatic reservoir. The alert system further comprises a control valve for selectively controlling the supply of compressed air from the pneumatic reservoir to the venturi valve. The alert system also comprises control means to change a position of the control valve to stop the supply of compressed air to the venturi valve when the air pressure within the second section of the suction cup vacuum conduit is less than a predetermined threshold pressure. Advantageously, the alert system is able to work in conjunction with a pneumatic lifting system that uses less compressed air than conventional pneumatic lifting systems. In another aspect of the invention, there is provided a pneumatic lifting system comprising an alert system. Advantageously, it is safer for a user to operate this type of pneumatic lifting system because there is a failsafe warning system to alert the userto a mains gas supply failure. Further advantageously, the risk of damage to the components being lifted is also reduced since, when the user receives an alert indicating that there is a mains supply failure, the user is able to respond accordingly to lower or otherwise safely release the lifted component. In another aspect of the invention, there is provided a method for operating an alert system for a pneumatic lifting system. The alert system comprises a pneumatic reservoir having an inlet for receiving compressed gas from a mains gas supply, a normally open control valve fluidically coupled at a first inlet to an outlet of the pneumatic reservoir, and a pneumatic alert means fluidically coupled to an outlet of the normally open control valve. The method comprises receiving pneumatic signal pressure from the mains gas supply at a control inlet of the normally open control valve. A pressure of the mains gas supply above a threshold value closes the normally open control valve. The method further comprises opening the normally open control valve so as to fluidically connect the pneumatic reservoir to the pneumatic alert means when a pressure of the mains gas supply falls below the threshold value. The method additionally comprises outputting, when the pneumatic reservoir is fluidically connected to the pneumatic alert means, an alert by the pneumatic alert means. Advantages for aspects of the invention relating to the method for operating an alert system for a pneumatic lifting system may be the same as those set out in relation to the aspects of the invention relating to the alert system itself. For conciseness, the descriptions of these advantages are not repeated. In an embodiment, the method also comprises controlling a flow of compressed gas from the pneumatic reservoir to the normally open control valve. The controlling is performed using a throttle provided between the outlet of the pneumatic reservoir and the first inlet of the normally open control valve. In an embodiment, the method further comprises preventing a flow of air from the pneumatic reservoir towards the mains gas supply using a non-return valve between the pneumatic reservoir and the mains gas supply. Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and / or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and / or features of any embodiment can be combined in any way and / or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and / or incorporate any feature of any other claim although not originally claimed in that manner. BRIEF DESCRIPTION OF THE DRAWINGS One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a full system diagram of a pneumatic lifting system comprising an alert system in accordance with embodiments of the invention. DETAILED DESCRIPTION In the following detailed description, reference is made to the accompanying figures that form a part hereof, and in which are shown by way of illustration specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that structural, logical, and electrical changes may be made without departing from the scope of the present invention. The sequence of operations is not limited to that set forth herein and may be changed as will be apparent to those skilled in the art, with the exception of operations necessarily occurring in a certain order. A pneumatic lifting system 100 in accordance with an embodiment of the present invention is described herein with reference to the accompanying Figure 1. The pneumatic lifting system 100 comprises a source 304 of mains pressure air supplied from a pump (not shown). The mains gas supply 304 supplies an air tank 302 with compressed air. Alternatively, the mains gas supply 304 may supply the air tank 302 with compressed air via an accumulator 306. The accumulator 306 may be a 20 bar accumulator. The accumulator 306 acts to smooth the compressed air pressure in the pneumatic lifting system 100. A non-return valve 802 is between the accumulator 306 and the mains gas supply 304 to prevent compressed air flowing back from the accumulator 306 to the mains gas supply 304 in the event of a failure thereof. The air tank 302 and accumulator 306 are also referred to as a pneumatic reservoir. A pressure regulator 308 may be provided after the air tank 302 to regulate the pressure of compressed air received in line 120 from the air tank 302. The pressure regulator 308 may allow compressed air to pass therethrough at a pressure of 5 bar so that the air pressure within the pneumatic lifting system 100 is 5 bar. The line 120, in a first branch 120a thereof, supplies a switch 202 which may be considered as a “vacuum on” switch. The switch 202 comprises a valve. Turning the switch on (for example, by pushing a button 202a on the switch 202) enables compressed air to flow through the switch 202, to an on / off valve 204. Turning the switch 202 off (for example, by providing a second push on the button or merely by releasing it) returns the valve to the position shown in Figure 1 in which it prevents compressed air flowing through the switch 202 to the on / off valve 204 in line 120d. Instead, any pressure in that line 120d is vented to atmosphere through the switch 202. The on / off valve 204 does not have a biased state. In its position shown in Figure 1, it prevents flow of gas in a second branch 120b of line 120 from progressing past the on / off valve 204. However, when operated by supply from the switch 202a, its spool moves to an open position in which it allows compressed air in the second branch 120b to pass into line 122. The open position of the valve 204 does not change until a further switch 206a is operated, which permits air in a third branch 120c of the line 120 to operate the on / off valve 204 in an opposite sense and move it to its closed position. It is to be noted that while switch 206a is in the position shown in Figure 1, line 130 is vented through the switch so that there is no resistance to movement of the spool when switch 202 is activated. When the on / off valve 204 is open, compressed air is received in the line 122 and supplies a supply valve 108 and, in dependence on a state of the supply valve 108, may pass therethrough to each of two venturi valves 106. (Only one venturi valve is present in some embodiments, and more than two in others. The two shown in Figure 1 is purely exemplary.) The venturi valves 106 operate in a known way to create a vacuum at their throats, in lines 124, also referred to herein as suction cup vacuum conduit 124. Each line 124 is protected by a check valve 128 which closes should the pressure in the lines 124 rise above a minimum threshold. However, while a vacuum persists in the lines 124, this vacuum is transmitted to a number of suction cups 102 for the purpose of grasping and lifting objects. That is, as known from the Venturi effect, when the compressed air flows through the constricted section of the venturi valve(s) 106, the velocity of the compressed air increases and a pressure within the valve consequently decreases. The low pressure causes the venturi valve 106 to draw air from a second side (the entrained fluid inlet) of the venturi valve 106 to create a (partial) vacuum. The suction effect draws air out from the conduit 124, so the air pressure within it is reduced to less than atmospheric pressure and a vacuum is formed. The air pressure within the conduit 124 may fall to at or below 0.5 bar, 0.4 bar or 0.3 bar when compressed air passes through the venturi valve 106. In use, one or more suction cups 142 are coupled to the suction cup vacuum conduit 124. The vacuum formed within the conduit 102 causes the suction cup to attach to a component in contact with the suction cup. The air pressure within the conduit 102 may fall to any level which enables a suction cup coupled to the conduit 102 to adhere by suction or otherwise attach to the component to be manipulated by the pneumatic lifting system 100. The non-return valve(s) 128 reduces or prevents the flow of air along line 124 towards the suction cup. This prevents a rapid loss of vacuum in line 124 should the vacuum produced by the venturi(s) 106 suddenly fail. In this way, a sudden release of any component held by the cups 142 can be avoided. Indeed, the non-return valve 128 divides the line 124 into first 124a and second 124b sections. The vacuum created in line(s) 124 is also transmitted in line 126, to a release valve arrangement 206, for enabling the suction cup(s) 142 to release a component to which they are attached. The release arrangement 206 comprises the release valve 206a, and an air providing valve 206b, which is biased to the closed position shown in Figure 1. In this position, the vacuum in line 126 is maintained. However, when the release valve 206a is activated, by pressing the button 206c on valve 206a, pneumatic signal pressure is applied from line 120c, along line 128, to the air providing valve 206b. The applied pneumatic signal pressure causes the valve 206b to change state whereby compressed air in yet further branch 120d of line 120 is able to pass through to line 126. This destroys the vacuum in line 126 and increases the pressure within the suction cups 102, resulting in release of any component previously held by the cup(s) 102. Pressing the release button 206c of the release valve 206a (which may be considered as a “vacuum off’ switch) not only connects line 128 to high pressure air in line 120c, releasing components held by the suction cups 102, but, via line 130, it also actuates on / off valve 204 to move it to its closed state. This isolates line 122 from the high pressure supply, so that further vacuum is not created by the venturi(s) 106. This is of course helpful in that there is no need for vacuum to be generated when components are not being held by the suction cups 102. Thus energy is saved. Valve 206a is like valve 202, in that, upon release of its button, it returns automatically (eg by a spring or similar bias) to its closed state. So, once a component has been released, for example, from the suction cups 102, valve 206a may be selectively released by an operator (which may be an automatic handling arrangement) and normally closed 5 / 2 valve 206b returns to its closed position, isolating lines 126 and 120d from each other. This does not immediately restore vacuum to the cups 102. That will only occur when the above process is repeated - that is, button 202a is pressed again. Returning to supply valve 108, this valve is a 5-way directional valve (5 / 2 valve) which is biased, for example by a spring disposed within the control valve 108, to be in a first state in which the supply valve is normally open allowing passage of air from line 122 to the venturi(s) 106 (as shown in this position in Figure 1). The spring controls a position of a moving element within the supply valve 108, such as a spool. The position of the spool controls the flow of air within the supply valve 108. In the first state, the spring applies a biasing force on the spool such that the spool is held in a first position in which compressed air in line 122 can flow through the supply valve to the venturi valve(s) 106. Such valves are known, as such, and do not require further elucidation here. However, when the supply valve 108 is closed, compressed air is prevented from flowing through the control valve to the venturi valve 106. The supply valve 108 may be closed as a result of a pneumatic signal pressure in line 160 received from a control valve 110. When pneumatic signal pressure from the control valve 110 acts on the supply valve 108, the pneumatic signal pressure overcomes a biasing force applied by the spring disposed within the supply valve 108. When the biasing force applied by the spring is overcome, the spool is no longer held in the first position by the spring. The spool consequently moves to a second position (not shown) in which compressed air from the mains air supply is no longer able to flow through the supply valve 108 to the venturi valve 106. The supply valve 108 can be said to be in a second state, wherein the second state the supply valve 108 is closed and compressed air in the line 122 does not escape. The control valve 110 is a normally closed valve (as shown in Figure 1). This isolates pressure in a branch 122a of the high pressure line 122 from reaching the supply valve 108 and moving it to its closed position. The valve 110 controls the state of the control valve 108 in dependence on the air pressure within the conduit 124, and, in particular, in dependence on the air pressure within the second section 124b by virtue of branch 162 from the line(s) 124. When the air pressure within the second section 124b reduces to reach a first predetermined threshold pressure, the vacuum causes the state of the control valve 110 to change. This, in turn, causes the state of the supply valve 108 to change. That is, when the vacuum in the second section 124b of the conduit 124 reaches the first predetermined threshold pressure, the low air pressure causes the biasing means disposed in the control valve 110 to move or change position of the valve spool. The movement of the spool causes the control means 110 to open. The first predetermined threshold pressure may be in the range of 0.3 bar to 0.5 bar. The first predetermined threshold pressure may be 0.5 bar, 0.4 bar, 0.3 bar or any suitable value at which a suction cup connected to the conduit 102 may suction and hold a component. When the control valve 110 is in its open state, compressed air flows through the control valve 110 through line 160 to the supply valve 108. The pressure of the compressed air flow causes the spool of the valve 108 to move against the biasing means causing the supply valve 108 to close and compressed air is no longer able to pass therethrough to the venturi valve 106, or indeed to escape from the valve 108. When the supply valve 108 is closed, compressed air is not supplied to the venturi valve 106 so the air pressure within the conduit 124 is no longer actively reduced by the venturi valve 106. Instead, the low air pressure within the second section 124b of the conduit 124 is substantially maintained by the non-return valve(s) 128. The effect, therefore, of the non-return valve(s) 128 and the supply valve 108 is twofold. Firstly, it locks in the vacuum in the second section 124b of the line 124, whereby further vacuum generation by the venturi(s) 106 is unnecessary. Secondly, by the control valve 110 closing the supply valve 108, the flow of compressed air through the system is reduced or halted, reducing the energy requirement of the pneumatic lifting system 100 and improving efficiency. However, due to natural air leakage at the suction cup(s) 142 and / or the non-return valve 128, the air pressure within the second section 124b gradually increases. When the air pressure within the second section 124b reaches a second predetermined threshold pressure, a force caused by the vacuum within the second section 124b is no longer sufficiently strong to hold its spool against the biasing means within the control valve 110 in its loaded state. This causes the control valve 110 to return to its normally closed state, which in turn means that compressed air no longer pressurises line 160 and the second inlet of the supply valve 108. The lack of pneumatic signal pressure from the control valve 110 to the supply valve 108 means that there is no longer adequate force applied to the biasing means within the supply valve 108 to retain the biasing means in its loaded state. The biasing means therefore returns to its normal state, and compressed air is able to flow from the control valve 108 to the venturi valve 106 once more. The renewed air flow to the venturi valve 106 allows the venturi valve 106 to recommence providing suction air to the suction cup vacuum conduit 124 in order to reduce the air pressure within it. Preferably, the second predetermined threshold pressure is higher than the first predetermined threshold pressure so that there is some hysteresis between the switching of the control valve 110. That is, it opens 13 when the pressure in line 124 drops to below the first level, but only closes again when the pressure has risen to a second, higher level. This difference in the first and second predetermined thresholds may in fact merely be a function of a delay in the response of supply valve 108 to a change of state of the control valve 110. That is, the control valve 110 may switch at a specific fixed threshold pressure, but when switched open, valve 108 responds slowly, so that the pressure in second section 124b reduces below the fixed threshold, and when that pressure rises through leakage etc to the fixed threshold, the delay in the response of supply valve 108 may be such that the pressure in the second section 124b rises above the fixed threshold before the vacuum provided by the venturi(s) 106 is sufficiently restored. Alternatively, the second predetermined threshold pressure may be a pressure in the range of 0.6 to 0.8 bar. The second predetermined threshold pressure may be 0.6 bar, 0.7 bar, 0.8 bar, or any suitable pressure at which a vacuum in the conduit 124 should be topped up so that the suction cup retains its suction on the component. Indeed, it is feasible that the control valve 110 be omitted and the signal line 162 from the second section 124b of the line 124 be directly connected to the supply valve 108, also omitting the lines 122a and 160. In this case, the vacuum in the line 162 below the first predetermined threshold holds the supply valve 108 in its closed position. It is preferred to use two valves, however, because the supply flow of air through the supply valve 108 at 5 bar pressure is more easily controlled by a signal line 160 operating at the same level of pressure, rather than a negative pressure. On the other hand, flow through the control valve 110, albeit controlling the same 5 bar pressure, has an insignificant flow requirement compared to valve 108 and can more reliably be controlled by a negative pressure (by which is meant a low pressure) in line 162. Providing a pneumatic lifting system 100 according to the present invention enables a component to be held by the pneumatic lifting system 100 without requiring a constant supply of compressed air over the venturi valve 106. The pneumatic lifting system 100 of the present invention therefore uses far less compressed air than a conventional constant-supply pneumatic lifting system. Tests have shown that the pneumatic lifting system 100 of the present invention may use only 0.8% of the compressed air compared to prior art pneumatic lifting systems. The effect of the arrangement is a periodic pulsing of air through the venturi(s) to “top up” the vacuum. Providing a pulsing pneumatic lifting system 100 advantageously allows components to be safely held for several hours at a time using minimal compressed air. Indeed, a further effect is that, should mains air pressure fail at the input 304, components can continue to be held for considerable time. This is a significant advantage as a mains air supply failure could otherwise cause the suction cups to quickly or immediately stop holding a component. The pneumatic lifting system 100 may further comprise a second control valve 208 and an indicating means 210. An inlet of the second control valve 208 may be couplable to the second section 124b of the vacuum conduit 124 via line 166. An outlet of the second control valve 208 may be couplable to the indicating means 210 by line 168. The second control valve 208 controls the operation of the indicating means 210 in dependence on the air pressure within the suction cup vacuum conduit 124b. The indicating means 210 indicates to an operator of the pneumatic lifting system 100 whether it is safe to lift a component using the pneumatic lifting system 100. The indicating means 210 may comprise one or more of a light, a speaker, or any other output means for providing an indication to the operator. When it is safe to lift a component using the pneumatic lifting system 200, the light may turn on and / or the speaker may output a sound. When it is not safe to lift a component, the light may turn off and / or or the speaker may not output a sound. Alternatively, the speaker may output a sound when it is not safe to lift the component, and may not output a sound when it is safe to lift the component. The indicating means 210 may be driven by compressed air fed via a branch 122b of the line 122 exiting on / off valve 204. When sufficient vacuum exists in conduit 124b, the valve spool of second control valve 208 moves from its normal biased position shown in Figure 1 to connect line 122b to line 168 and thereby signal to indicating means 210 to commence indicating safe operation. There may be a predetermined third threshold pressure at which the indicating means activates to indicate that there is sufficient vacuum so that it is safe to lift a component. The threshold pressure may be 0.5 bar, 0.4 bar, 0.3 bar, or any suitable pressure at which it is safe to operate the pneumatic lifting system 200 to lift a component using the pneumatic lifting system 100. The predetermined third threshold pressure may be the same as or different to the second threshold pressure. When air pressure within the second section 124b of the conduit 124 increases to reach a fourth predetermined threshold pressure, there may not be sufficient vacuum to keep the second control valve 208 in an open state. The second control valve 208 may then return to its normal closed state so compressed air is no longer able to pass therethrough to the indicating means 210 and the indicating means 210 turns off. When the indicating means 210 turns off, this indicates to an operator of the pneumatic lifting system 200 that it is no longer safe to lift a component using the pneumatic lifting system 200 because there is no longer a sufficient vacuum at the suction cup(s) 142 to reliably hold a component. The fourth predetermined threshold pressure may be a pressure in the range 0.6 to 0.8 bar, or any pressure at which it is no longer safe to operate the pneumatic lifting system 100 because there is too great a risk that a suction level at a suction cup is not sufficiently strong to safely lift, hold and manipulate the component. The fourth predetermined threshold pressure may be higher than the second predetermined threshold pressure. This means that, in use, the pneumatic lifting system 100 may keep the vacuum within the second section 124b of the suction cup vacuum conduit 124 topped up to a safe level for the operator to continuously operate the pneumatic lifting system 100. Advantageously, the operator therefore does not need to pause their work to wait for the air pressure within the second section 124b of the conduit 124 to reduce back down to a safe level. Referring to the mains supply 304, the pneumatic lifting system 100 further comprises an alert valve 310 fluidically coupled to an alert means 312. The alert means 312 outputs an alert when there is a mains gas supply 304 failure, whereby a user may be informed of a failure of the air supply and potential subsequent failure of the pneumatic lifting system 100. A mains gas supply 304 failure may constitute a reduction in the pressure of the compressed air supplied by the mains gas supply 304 to below a fifth predetermined threshold pressure. The alert means 312 may comprise a pneumatically controlled means such as an air horn. The alert valve 310 may be a normally open 5 / 2 valve that is coupled at a first inlet to a line 180 from the mains gas supply 304. When the mains gas supply 304 supplies compressed air at a pressure at or above the fifth predetermined threshold value, the pressure of the compressed air causes the alert valve 310 to be in a first closed state. A second inlet of the valve 310 is connected to a line 182 from a throttle 804 that is itself connected to a further branch 120f of the output 120 of the pressure regulator 308. When the valve is in an open state, as shown in Figure 1, the line 182 is connected to an outlet line 184 of the valve 310, which is connected to the air horn 312. Thus, should the mains pressure of air in line 180 drop below the fifth predetermined level, the valve 310 opens through operation of its biasing means and connects the air horn 310 with air under pressure from the accumulator 302 and regulator 308, and as a result, sounds an alert. The throttle 804 serves to regulate the pressure of gas sounding the air horn 312 and limit the escape of air from the system 100 and thereby extending the period of time over which the lifting system 100 remains operational. When the valve 310 is in a closed state, the air horn is isolated from the accumulator 302 and regulator 308 and so remains normally silent. Thus, should the alert operate, this indicates to the user that the system will not continue to enable lifting and holding of components, at least not after all the gas in the accumulator306 has been exhausted. However, this will not be immediately. It is to be noted that the system 100 uses multiple signal lines that shown in Figure 1 by cross-hatching the respective lines. These lines require pressure (or absence of pressure) to signal and actuate the valves to which they are connected. However, significant flow of air is not required. Indeed, actuation of the valves could be electrically controlled using solenoids to move actuate the valves. However, this would introduce an additional point of potential failure. Indeed, failure of the air supply 304 could be caused by an electrical failure. Use of an air horn for the alert 312 is therefore advantageous for the same reason, although it is not essential, particularly if an electrical alert means is backed up by a battery for instance. However, the use of an air horn is made possible, despite the failure of the air supply 304, by the isolation of the system from the ambient atmosphere (unless either of the buttons 202a, 206c are pressed) and the availability of pressurised air from the accumulator 306. It will be appreciated that various changes and modifications can be made to the present invention without departing from the scope of the present application.

Claims

1. An alert system for a pneumatic lifting system, the alert system comprising:a pneumatic reservoir having an inlet for receiving compressed gas from a mains gas supply;a normally open control valve fluidically coupled at a first inlet to an outlet of the pneumatic reservoir; anda pneumatic alert means fluidically coupled to an outlet of the normally open control valve;wherein the normally open control valve has a control inlet for receiving pneumatic signal pressure from the mains gas supply, such that a pressure of the mains gas supply above a threshold value closes the normally open control valve, and a pressure of the mains gas supply below the threshold value allows the normally open control valve to open so as to fluidically connect the pneumatic reservoir to the pneumatic alert means to output an alert.

2. The alert system of claim 1, wherein the pneumatic alert means comprises an air horn.

3. The alert system of claim 1 or claim 2, further comprising a throttle valve provided between the outletof the pneumatic reservoir and the first inlet of the normally open control valve to control a flow of compressed gas from the pneumatic reservoir to the normally open control valve.

4. The alert system of any of the preceding claims, further comprising a non-return valve between the pneumatic reservoir and the mains gas supply for preventing a flow of air from the pneumatic reservoir towards the mains gas supply.

5. The alert system of any of the preceding claims, further comprising:a suction cup vacuum conduit for connection to a suction cup, the suction cup vacuum conduit comprising a first section and a second section;a non-return valve located in the suction cup vacuum conduit, between the first section and the second section, for preventing the flow of air along the suction cup vacuum conduit, towards the suction cup, in use;a venturi valve which is fluidically couplable to the pneumatic reservoir and the first section, the venturi valve being configured to reduce the air pressure within the suction cup vacuum conduit when compressed air is supplied to the venturi valve from the pneumatic reservoir;a control valve for selectively controlling the supply of compressed air from the pneumatic reservoir to the venturi valve; andcontrol means to, when the air pressure within the second section of the suction cup vacuum conduit is less than a predetermined threshold pressure, change a position of the control valve to stop the supply of compressed air to the venturi valve.

6. A pneumatic lifting system comprising the alert system of any of the preceding claims.

7. A method for operating an alert system for a pneumatic lifting system, the alert system comprising a pneumatic reservoir having an inlet for receiving compressed gas from a mains gas supply, a normally open control valve fluidically coupled at a first inlet to an outlet of the pneumatic reservoir, and a pneumatic alert means fluidically coupled to an outlet of the normally open control valve; the method comprising: receiving, at a control inlet of the normally open control valve, pneumatic signal pressure from the mains gas supply such that a pressure of the mains gas supply above a threshold value closes the normally open control valve;opening, when a pressure of the mains gas supply falls below the threshold value, the normally open control valve so as to fluidically connect the pneumatic reservoir to the pneumatic alert means;outputting, by the pneumatic alert means, an alert when the pneumatic reservoir is fluidically connected to the pneumatic alert means.

8. The method of claim 7, further comprising controlling, by a throttle provided between the outlet of the pneumatic reservoir and the first inlet of the normally open control valve, a flow of compressed gas from the pneumatic reservoir to the normally open control valve.

9. The method of claim 7 or claim 8, further comprising preventing, by a non-return valve between the pneumatic reservoir and the mains gas supply, a flow of air from the pneumatic reservoir towards the mains gas supply.

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