Title of Invention	"AN AUTOMATIC STOP DEVICE FOR A LPG CYLINDER EMPTYING PUMP"
Abstract	The present invention provides an automatic stop device for stopping an LPG cylinder emptying pump when a persistent no-flow condition is detected. The said stopping action protects the pump from dry running and gives an operator a visible indication that the emptying operation has completed.

Full Text

The present invention relates to an automatic stop device for a LPG cylinder emptying pump. Background of the invention It is sometime necessary to empty LPG cylinders so that maintenance operations (eg. valve removal) can be conducted safely. One method of evacuating the cylinder is to invert and connect the valve to the suction of a pneumatically powered reciprocating pump so that the liquid in the cylinder is sucked out. One problem associated with this method is that the pump must be switched off when the cylinder is empty. This is necessary- to prevent extended dry running that will damage the seals in the pump and also cause it to over heat. The conventional method of achieving this is to incorporate a transparent sight glass in the inlet pipe of the pump. The operator monitors the sight glass and when he sees that liquid is no longer flowing he switches off the pump. This method requires continuous monitoring by the operator and is vulnerable to inexperience or inattention on his part. Object and summary of the invention The object of the present invention is to obviate the above drawbacks and provide invention provide a simple and automatic device to detect the no-flow condition and switch off the pump when required Another objective of the invention is to achieve this control using compressed air as the only source of power for the invention. To achieve the said objectives the present invention provides an automatic stop device for a LPG cylinder emptying pump comprising: - a flow sensor mounted in the outlet line of the LPG pump, - a conventional pneumatic proximity detector mounted on said flow sensor, - a pneumatic throttle valve, the input of said throttle valve being connected to an output of the proximity detector, - a pneumatic delay reservoir connected to output of the pneumatic throttle valve, - a pneumatic spool valve is connected to said reservoir and is switched on either by a lever or by a pneumatic piston powered by the air in said reservoir and to be switched off by a return spring within said spool valve, output of said spool valve is connected to the pump to control the starting and stopping of the pump, and - supply port in said spool valve is connected to compressed air and an exhaust port is open to the atmosphere. The said flow sensor contains a sliding nozzle and a spring. The said sliding nozzle has a flow constriction and an annular magnet. The said pneumatic throttle valve contains a throttle screw and a non-return valve for delaying the stopping of the pump. The said flow sensor is made of non-magnetic material for avoiding interference with the magnetic field of the magnet. The said pneumatic throttle valve is a one way throttle valve. Brief description of the drawings Figure 1 shows a sectional view of the automatic device in the off condition in which the LPG pump is disabled according to the present invention. Figure 2 shows a sectional view of the automatic device when liquid fuel is flowing through the pump according to the present invention. Detailed description of the accompanying drawings The device provided by the instant invention consists of a flow sensor (100) constructed of non-magnetic materials mounted in the outlet line (15) of the LPG pump (10) and containing a sliding nozzle (110) and a spring (120) inside it. The sliding nozzle contains a flow constriction (115) and an annular magnet (117) within it. A conventional pneumatic proximity detector (150) is mounted on the flow sensor (100) and a one way pneumatic throttle valve (160) containing a throttle screw (161) and a non return valve (163) is also provided. The input (162) of the throttle valve is connected by a tubing to the output (155) of the proximity detector. The device also contains a pneumatic delay reservoir (170) connected to the output (165) of the pneumatic throttle valve (160). Further it includes a pneumatic spool valve (200) designed to be switched on either by a lever (207) or by a pneumatic piston (180) powered by the air in the reservoir (170) and to be switched off by a spring (205). The output (206) of the spool valve is directed to the pump and is used to control the starting and stopping of the pump. The Port (208) in the valve is connected to a supply of compressed air and port (209) is open to the atmosphere. Figure 1 shows the device in its off condition. In this condition the spool (201) of valve (200) is kept in the off position by the action of spring (205). There is thus no output from the port (206) of the spool valve (200). And therefore the pump is off. In order to start the pump the operator shifts the lever (207) of spool valve (200) to the on position by applying manual force to overcome spring (205). This shifts the spool (201) to connect the supply port (208) to the output (206). This output starts the pump. The pumping action causes liquid to flow through the outlet line (15) of the pump and through the flow sensor (100). The flow passes through the flow constriction (115) within the sliding nozzle (110) in the flow sensor. Flow through this constriction causes a drag to develop across the sliding nozzle. This spring (120) is selected such that this drag is sufficient to overcome it and permit the nozzle to slide in the direction of the flow. An annular magnet (117) is mounted on the sliding nozzle & moves with it. A pneumatic proximity detector (150) of conventional design is mounted on the outside of the flow sensor. The position of the detector is such that the sliding of the nozzle (110) causes magnet (117) to move into the detection range of the pneumatic proximity detector (150). This causes the detector to give a pneumatic output at its port (155). To avoid interference with the magnetic field the flow sensor (100), sliding nozzle (110) and spring (120) are all constructed of non magnetic materials. The output (155) is connected to the input (162) of the one way throttle valve (160). This flow passes unobstructed through the non return valve (163) in the flow controller and into the reservoir (170) and causes pressure to build up in it. This pressure acts on the pneumatic piston (180) and causes it to apply force on the spool (201) of the pneumatic spool valve (200). The pneumatic piston (180) is sized such that this force is sufficient to overcome the spring (205) of the spool valve. The resulting ON condition is as shown in Figure 2. The operator after a few second can remove his hand from the lever (207). The pump will remain on because of the action of the pneumatic piston (180) on the pneumatic spool valve (200). After the cylinder (C) connected to the inlet of pump (10) becomes empty, liquid stops flowing through the pump, continued running in this dry inlet condition can damage the pump seals and also causes the pump to overheat. This automatic stop device prevents this from happening in the following way. When liquid stops flowing through the outlet (15) of pump, the drag on the nozzle (110) becomes zero and the spring (120) forces the nozzle to its normal no flow position. This causes the annular magnet (117) mounted on the nozzle to move out of the range of pneumatic proximity detector (150). The output (155) of the detector thus switches off. The air collected in reservoir (170) begins to leak out slowly around the throttle screw (161). The sizes of the reservoir and the adjustment of the throttle are selected such that if this leakage persists for a few seconds then the remaining pressure inside reservoir (170) is no longer sufficient to overcome the spring (205). The spring then forces the spool valve to the off position of figure 1 and switches off the output at port (206) of the spool valve. Absence of this signal causes the pump to switch off. It may be noted that the device will only switch off the pump after a no flow condition has persisted for a desired delay time which can be adjusted by the throttle screw (161) if needed. This prevents erroneous stoppages due to the flow pulsation naturally present at the outlet of a reciprocating pump. It may also be noted that the lever (207) of the spool valve (200) snaps to the off position at switch off. Thus providing a clearly visible indication of the completion of pumping. I Claim: An automatic stop device for a LPG cylinder emptying pump comprising: - a flow sensor mounted in the outlet line of the LPG pump, - a conventional pneumatic proximity detector mounted on said flow sensor, - a pneumatic throttle valve, the input of said throttle valve being connected to an output of the proximity detector, - a pneumatic delay reservoir connected to output of the pneumatic throttle valve, - a pneumatic spool valve is connected to said reservoir and is switched on either by a lever or by a pneumatic piston powered by the air in said reservoir and to be switched off by a return spring within said spool valve, - output of said spool valve is connected to the pump to control the starting and stopping of the pump, and - supply port in said spool valve is connected to compressed air and an exhaust port is open to the atmosphere. The automatic stop device as claimed in claim 1 wherein said flow sensor contains a sliding nozzle and a spring. The automatic stop device as claimed in claim 2 wherein said sliding nozzle has a flow constriction and an annular magnet. The automatic stop device as claimed in claim 1 wherein said pneumatic throttle valve contains a throttle screw and a non-return valve for delaying the stopping of the pump. The automatic stop device as claimed in claim 1 wherein said flow sensor is made of non-magnetic material for avoiding interference with the magnetic field of the magnet. 6. The automatic stop device as claimed in claim 1 wherein said pneumatic throttle valve is a one way throttle valve. 7. An automatic stop device for a LPG cylinder emptying pump substantially as herein described with reference to and as illustrated in the accompanying drawings.

Documents:

1081-del-2003-abstract.pdf

1081-del-2003-claims.pdf

1081-del-2003-complete specification (granted).pdf

1081-del-2003-correspondence-others.pdf

1081-del-2003-correspondence-po.pdf

1081-del-2003-description (complete).pdf

1081-del-2003-drawings.pdf

1081-del-2003-form-1.pdf

1081-del-2003-form-19.pdf

1081-del-2003-form-2.pdf

1081-del-2003-form-3.pdf

1081-del-2003-pa.pdf