|Title of Invention||
"A SAFETY DEVICE FOR COMPRESSED AIR SUPPLY DRIVEN EQUIPMENT"
|Abstract||This invention provides a pneumatic latching valve for isolating the air output to equipment on a loss of supply pressure. The valve prevents air output even after the reapphcation of supply pressure unless manually reset. Also capable of being operated manually to turn off air output even if supply is present. The improvements comprise the integration of the above features in one unit. Convenient mounting in the air line, simple construction to enhance reliability, ease of manufacture and ruggedness.|
|Full Text||This invention relates to a safety device for compressed air supply driven equipment on the loss of supply pressure
Equipment that operates on compressed air is very commonly used in industry. All such equipment has to be connected to a source of compressed air. Conventionally, this connection is through a normal manually operated on/off isolation valve located on the equipment.
The source of compressed air is usually a compressor connected to a piping network. Connections for individual equipment are taken off the network.
There are a variety of causes that can cause a loss of air supply in the network or to individual equipment. Examples of these are compressor shutoff or breakdown. Hose blowout or other substantial leaks somewhere in the network, section of the network being shut off for maintenance etc.
In such cases the reestablishment of the supply can cause sudden startup of the connected equipment. Most such equipment is of such a nature that unattended startup can be hazardous to the equipment, to the personnel near it or to the integrity of the process in which the equipment functions. This is often the case even in equipment that normally operates without human intervention.
To prevent this occurrence it is necessary to provide some means of ensuring that the equipment remains off even after the reestablishment of the air supply. It is also necessary that any such means be independent of human oversight.
Conventionally, this function is implemented by incorporation of interlocks in the design of the pneumatic circuit that controls the equipment.
This solution serves the purpose but suffers from certain drawbacks. It is implemented using combinations of conventional general purpose pneumatic components. This makes it moderately complex and therefore expensive. It also makes high reliability more difficult to achieve. Also it is implemented in a variety of ways depending on the designer of the specific equipment in question, and its function is hidden away in the functioning of the rest of the circuit. This makes its integrity difficult to verify without careful analysis of individual designs.
The objects of the invention are to provide a device for isolating the air output to connected equipment if supply pressure is lost. And to require human
intervention to turn on the output even after the supply is restored, primarily in the interest of safety.
To achieve the said objectives the present invention provides a safety device for compressed air supply driven equipment comprising:
a cylindrical stem having an axial inlet and outlet passage, the outer surface of the stem is stepped down to first cylindrical sliding and sealing surface having a first radial passage connected to said inlet, and a second radial passage axially displaced from said first radial passage to connect to the outlet passage, the stem is further stepped down to form a second sliding and sealing surface containing a third radial passage connecting to the outlet, the upper most end of the stem forms a flange around the said inlet passage,
a sleeve is fitted on the said stem with O-rings around the first sliding surface of the stem,
a spring means provided against an external step on the said sleeve,
means to retain the said spring means on the said stem,
the arrangement of the flange on the outer surface of the stem and the step on the outer surface of the sleeve is such that in the OFF condition, the sleeve is forced against the flange by the action of the spring and the inlet is isolated from the outlet by the action of the second O-ring and in the ON condition, the sleeve is forced against the means to retain the said spring means under the action of air pressure and the inlet is connected to the outlet via the said annular gap and the first and the second radial passages and the forcing action of the air pressure on the sleeve is achieved by the action of air pressure on the internal step in the sleeve
The means to retain the spring means is a washer and a circlip.
The said stem is grooved to receive a circlip.
The outlet end of the said stem is threaded to a standard pipe thread to receive a standard female pipe fitting.
The invention will now be explained with reference to the accompanying
Fig. 1 shows the isometric view of the device.
Fig. 2a shows the stem, according to this invention
Fig 2b shows the sleeve of the device, according to this invention
Fig. 3 shows the sectional drawing of the device in the off position
Fig. 4 shows the sectional drawing of the device in the on position.
Referring to the accompanying drawings, figure 2a shows the stem and figure 2b shows the sleeve. The stem (1) contains an axial inlet passage (IN) at the upper end, and an axial outlet passage OUT at the lower end. The outer surface of the stem (1) is stepped to progressively decreasingly diameter from the inlet to the outlet end. The upper most end of the stem (1) forms a flange (F) around the inlet. Proceeding down from inlet to outlet the stem is stepped down to form first cylindrical sliding and sealing surface S1 for the sleeve (2), which contains a first radial passage (12) connecting to the inlet passage and second radial passage (15) axially displaced from the first one to connect to the outlet passage. The stem is further stepped down to form a second sliding and sealing surface S2 containing a third radial passage (17) connecting to the outlet. The sleeve (2) shown in figure 2b is bored at the upper and lower ends to a sliding fit over the first sliding surface of the stem (1). This bore contains an undercut and fitted with a first O-ring (11) on its upper side and a second O-ring (14) on the other side. In the assembled condition, this arrangement forms a sealed annular passage around the first sliding surface of the stem (1). The sleeve is also bored pout at the lower end to a sliding fit over the second sliding surface of the stem (1). This bore contains a groove at the lower end fitted with a third O-ring (18). The outer surface of the sleeve (2) contains an external step sized to support one end of the spring (5).
Figure 3 shows the sectioned view of the device in the off position. The device consists of a stem (1). A sleeve (2) fitted slidably on the stem, a spring (3) bearing against a step (130) on the sleeve and a spring retaining washer (4) which is retained on the internal stem by a circlip (5).
The stem contains an axial inlet passage IN and an axial outlet passage OUT. The inlet passage contains a radial passage (12) connecting to the outer surface of the stem. The outlet passage contains radial passages, (15) and (17) connecting to the outer surface of the stem. The outer surface of the stem
contains steps (110) and (101). A portion (10) of the inlet passage is threaded to accept a standard male pipe fitting. A portion (19) of the lower end of the stem is threaded to accept a standard female pipe fitting.
The sleeve contains O-rings (11, 14, 18) seated in grooves machines for the purpose, annular undercuts (131) and (132) sized to leave an annular passage around the stem. It also contains a step (102).
In operation the air supply is connected to the inlet passage (IN) and the outlet passage (OUT) is connected to the equipment to be supplied with air.
In the off condition shown in figure 3. The inlet and outlet passages are unconnected because of the isolating action of O-ring (14). Thus no compressed air is supplied to the outlet. Furthermore the outlet and thus the equipment connected thereto - is connected to the outside atmosphere by radial passage (17). Thus the outlet retains no pressure.
To turn the device on the operator slides sleeve (2) along stem (1) by exerting sufficient force to overcome spring (3), as the sleeve slides along the stem the O-ring (18) slides past passage (17) sealing the outlet passage against the atmosphere. Simultaneously O-ring (14) slides past hole (15) thus connecting passages (12) and (15) via annular passage (13). In this condition the inlet passage is connected to the outlet passage and compressed air can flow through the device to the connected equipment. This condition is shown in figure 4.
The device is designed such that it remains in the on condition even if the operator now releases the sleeve (2). This is ensured by the feet that passage (17) now connects the outlet to the annular gap (100). This gap is thus pressurized by the supplied air. This pressure acts in opposing directions on step (101) of the stem and step (102) of the sleeve. The steps are sized such that the resultant force due to this pressure is sufficient to overcome the action of spring (3).
If due to any reason the compressed air supply to the device at the inlet passage (IN) is lost, the pressure in gap (100) drops and is no longer sufficient to overcome the force exerted by the spring (3). The action of the spring then forces the valve to the off position (figure 3). Thus isolating the outlet from the inlet and also connecting the outlet to the atmosphere through passage (17).
An additional feature of the device is that the pressure at which mis switch OFF occurs is dependent on the stiffness of spring (3). By changing the spring, the switch OFF pressure may be changed, thus causing the device to act as an isolating pressure switch.
Once the valve is in the off position subsequent reapplication of pressure at the inlet passage will have no efifect at the outlet. Thus protecting the connected equipment from inadvertent startup. The outlet will be restored only when the device is turned on manually as previously described.
1. A device to limit the force on a LPG valve during a valve changing operation on a
pressurized cylinder using a valve changing machine comprising a shaft mounted on
a slide which moves up or down by a hydraulic cylinder and containing a socket
mounted slidably within a cavity at the lower end of the shaft, characterized in that
a sensing rod connected to said socket and extending upwards through an axial hole in the shaft,
- an intermediate portion of said sensing rod containing pins radially
extending outwards through slots in said shaft,
outward ends of said radial pins are fixed to a feedback ring such that any axial motion of the socket is transferred to said feedback ring,
- a feedback lever connected to said slide by a pivot at its one end and the
other end resting on said feedback ring such that any axial motion of the
feedback ring causes the feedback lever to rotate about said pivot,
a roller lever mounted on said slide to actuate a hydraulic spool valve with the roller resting on top of said feedback lever such that the movement of said feedback lever causes the roller lever to move the spool of the hydraulic valve, and
- the hydraulic output ports being connected to rod end and cap end of the
hydraulic cylinder, such that when the roller lever is raised up from neutral
position, it causes the rod of the hydraulic cylinder to extend and when the
roller lever is lowered from neutral position, it causes the rod of the
hydraulic cylinder to retract for limiting the force impressed on the LPG
2. The-device as claimed in claim 1 wherein the uppermost end of said sensing rod is
mounted slidably into a balancing chamber-in the upper end of the shaft, an axial
hole provided within the sensing rod connects the inside of said sealing bell to said
A safety device as claimed in claim 1 wherein the means to retain the spring means is a washer and a circlip.
2. A safety device as claimed in claims 1 or 2 wherein the said stem is grooved to receive a circlip.
4. A safety device as claimed in claim 1 wherein the outlet end of the said stem is threaded to a standard pipe thread to receive a standard female pipe fitting.
5. A safety device for compressed air supply driven equipment substantially as herein described with reference to and as illustrated in the accompanying drawings.
|Indian Patent Application Number||200/DEL/2000|
|PG Journal Number||31/2009|
|Date of Filing||07-Mar-2000|
|Name of Patentee||YUNUS PATEL|
|Applicant Address||508, ASIAN GAMES VILLAGE NEW DELHI-110049, INDIA.|
|PCT International Classification Number||F16L 37/28|
|PCT International Application Number||N/A|
|PCT International Filing date|