GB2099150A - Pressure differential indicator - Google Patents

Abstract

A brightly coloured signal body 20 having a ferrous part 22 is restrained against the forces of a spring 21 within a housing by a permanent magnet 10 carried by a piston 8. The signal body 20 and piston 8 are physically separated by a relatively thin wall, and opposite ends of the piston 8 are exposed to fluid pressures from two locations, e.g., at the input and output sides of a filter. The piston 8 is urged toward the signal body 20 by a second spring 15. When the pressure difference across the piston 8 is great enough the piston 8 moves away from the body 20, taking the magnet and letting the first spring 21 push the body 20 to an obvious protruding position. The piston carries a valve member 16 which closes passage 7 when excess pressure occurs thereby preventing contaminated fluid passing to the low pressure side via channel 12. <IMAGE>

Description

SPECIFICATION Pressure differential indicator This invention relates to a pressure differential indicating device and especially to a device for indicating the presence of a predetermined pressure difference between pressure mediums in two locations such as at the input and output sides of a filter.

The prior art includes an indicator device which is intended to show when a difference in pressure between two locations exceeds a predetermined value. In that device, a housing contains a movable piston which is urged by a spring in one direction, opposite ends of the piston being coupled to the two locations. A permanent magnet is movable with the piston in the direction against the spring force as the pressure difference increases. The actuating member of a switch mounted outside of the housing is affected by the magnet so that as the magnet is moved, the switch operates. It has been found that operation of the switch in this device is not reliable, a serious disadvantage.

According to the present invention apparatus for indicating a pressure difference between two locations, the apparatus being of the type having a housing, a spring-urged pressure piston movable in said housing, opposite ends of said piston being coupled to the two locations, and a permanent magnet movable with the piston against the spring in response to increasing pressure differences, comprises a signal body composed at least in part of a ferromagnetic material coaxially disposed relative to one end of said piston in said housing and a second spring urging said signal body away from said piston and wherein said first spring urges said piston toward said signal body, the end of said piston facing said signal body being coupled to the pressure medium location having the greater pressure.

Apparatus in accordance with the present invention preferably provides a device for reliably indicating the existence of a predetermined pressure differential, for example across a filter, which device is simple to fabricate.

As will be recognised from the following description, the signal body may be reliably moved from its rest position whenever the high-pressure side of the pressure piston, which carries a permanent magnet, has reached a predetermined distance from the signal body. The apparatus according to the invention is developed in a simple fashion and is fluid-proof. It has a compact, rugged form of construction and requires little space.

In addition, the structure may be so arranged that pressure medium originating in one part of the system being measured, especially contaminated fluid, is reliably prevented from mixing with pressure agent of the other location, such as filtered or purified fluid.

In addition, the preferred characteristics of the apparatus make it rather insensitive to pressure surges occurring in the system being monitored.

In order that the manner in which the foregoing and other objects are attained in accordance with the invention can be understood in detail, a particularly advantageous embodiment thereof will be described with reference to the accompanying drawing, which forms a part of this specification, and which shows a side elevation, in section, of an apparatus in accordance with the invention connected to a schematically-illustrated fluid circuit.

As shown in the drawing, a vessel 1 carries an inserting body 2 which is generally cylindrical in shape and which constitutes a housing for the apparatus of the invention. The partially illustrated vessel 1 can be a pressure vessel or the lid or cover of such a vessel having a cavity to receive the pressure differential indicator. Body 2 has a blind bore and is threaded into the opening in vessel 1 in such a way that the opening of the blind bore can be connected to a filter 29 in a fluid system and such that the insert body 2 does not project into a channel 1 a which is provided in the vessel or lid 1 and extends transversely to it.

Sealing rings 3 and 4 serve to seal the gaps between the vessel 1 and body 2. In the mouth of the blind bore in body 2 is a lock nut 5 which threadedly engages the bore and which has, on the side toward the filter, a hexagonal part which can be engaged by a tool and on the side opposite the base of the blind bore in body 2 it has a throttle bore 7 which has a considerably smaller diameter.

Within the blind bore of body 2 is a pressure piston 8 which is mounted in such a way that it is axially movable. The piston is made of a nonmagnetic material such as aluminum and contains a bolt 9 of ferromagnetic material. The end of the bolt 9 facing away from screw 5 is attached to two disc-shaped permanent magnets 10 and 1 1 of which magnet 10 is further removed from the bolt and has predetermined small clearance from the end of piston 8, which distance prevents the sticking of the permanent magnet to body 2 as well as its striking against the end of the blind bore. Bolt 9 and magnets 10 and 11 are attached to each other and to the pressure piston 8 by means of an adhesive substance. Piston 8 has an annular groove 12 and is provided with axially facing shoulders 13 and 14 which are formed by constrictions in the shape of the piston.Between shoulder 14 and screw 5 is a compression coil spring 15 which urges the piston toward the upper end, as illustrated in the figure, or toward the bottom of tpe blind bore.

On the same end of piston 8, which faces away from the permanent magnets, is a valve member in the form of a ball valve 16. The ball 16 is attached to the end of the piston and cooperates with the upper edge 1 7 of bore 7, forming a valve assembly.

A guide part 18, which is made of a polymeric, plastic material, is attached to the projecting end of body 2, an end of guide part 18 having a radially inwardly extending annular bead which fits into an annular groove on body 2. Guide part 1 8 is developed as a hollow conical body having radially inwardly extending ribs 19 which form a cylindrical guide cavity in the interior of the guide part for receiving a graduated and colored signal body 20, which body is preferably red. Between a shoulder of the signal body facing the insert body 2 and the body 2 itself is a compression coil spring 21 which urges the signal body 20 away from body 2. A shoulder of the signal body facing away from the spring cooperates with a collar 36 projecting inwardly of the guide part 1 8, forming a stop. Signal body 20 likewise has a blind bore which is open toward the insert body 2.In that blind bore is a supporting body 22 made of a ferromagnetic material. Body 22 may alternatively be a permanent magnet. It projects on the side of body 2 beyond signal body 20 and is supported on a side facing away from this on a shoulder located within signal body 20.

The end of guide part 18 facing away from insert body 2 is covered by a hood 23 made of a soft, elastic transparent material. The hood 23 has a flange 24 projecting radially inwardly which engages with an annular groove in guide part 18.

A ventilation bore 25 permits the ventilation of the interior of hood 23 whenever the hood is deformed to permit it to recover its original shape.

In the lid or vessel 1 is a bore 26 which is connected by way of a longitudinal groove 27 located therein to the insert body 2. With this longitudinal groove a transfer bore 28 is connected, leading to the blind bore in the body 2, which bore 28 leads to the area of the annular groove 12.

In the drawing, a filter 29 is shown only schematically, the filter being a conventional type through which pressure medium flows in the direction of arrow A, which pressure medium is delivered by line 30 and carried away through line 31. A line 32 connected with bore 26 is connected to line 30, and line 31 is connected by way of line 33 with the hexagonal part 6 of lock nut 5. The pressure in at the input or upstream end of filter 29 is coupled by way of line 32, bore 26, longitudinal groove 27 and transverse bore 28 to the annular groove 12 in piston 8.Between groove 12 and the upper end of piston 8 which carries permanent magnets 10, 11 there is a damping collar 34 between which and the wall of the insert body there is a small gap dimensioned so that the pressure in the annular groove 12 can continue into chamber 35 defined in part by the permanent magnet 10, whereby pressure surges are dampened. Pressure surges occurring in the line 33 are damped by throttle bore 7.

As filter 29 becomes increasingly contaminated, the pressure increases in chamber 35 relative to the pressure at the inner end of bore 7. Whenever this pressure difference increases beyond a certain value, then the force of spring 1 5 is overcome and the pressure piston 8 is moved in the direction toward lock nut 5. As a result, the distance between the permanent magnets 10 and 11 from supporting body 22 is increased and, as soon as this distance reaches a predeterminable spacing, the magnetic "hold" is drastically reduced and the supporting body 22 is axially shifted by the action of spring 21 in the direction toward hood 23. Thus, the signal body 20 moves outwardly through guide part 18 and the end portion thereof becomes visible through hood 23.

The emergence of the signal body 20 from guide part 18 is thus a sign indicating the need to replace or otherwise clean the contaminated filter 29. As soon as contaminated filter 29 is removed, the pressure piston 8 returns to the starting position illustrated in the drawing. Signal body 20 can be restored manually to the position shown in the drawing, or depending on the space involved, it can be pulled back into that position by the magnetic force of magnets 10, 11. As will be recognized, manual restoration is accomplished by simply pressing on the end of hood 23, deforming the hood until it presses against the end of the signal body and pushes it back into its guide cavity within guide part 18.

If a predetermined higher pressure is allowed to occur in chamber 35, the ball valve 16 is pushed downwardly with the body to the point at which it seats on the edge 17 of lock nut 5 as a result of which the communication between the chamber containing spring 15 and the bore 7 is terminated.

Generally, the closing pressure of the valve 16, 17 is selected such that at the start of the transfer of pressure medium located in groove 12 into the chamber encompassing spring 1 5, the valve 1 6.

1 7 is closed so that transfer of contaminated r pressure medium into the passages containing clean pressure medium will be reliably prevented.

In a practical construction, such a gap was selected between piston 8 and the wall of body 2, and throttling annular grooves were formed in the piston 8 in such a way that pressure medium was transferred from groove 12 into the chamber containing spring 1 5 at a pressure of about 10 bar. At this pressure, valve 16, 1 7 was also closed.

The insert body 2 and the piston 8 each are made of nonmagnetic material such as, for example, non magnetic steel, nonferrous metal or the like. Body 2 can be threadedly engaged in either a housing head, a housing or a container lid.

While one advantageous-embodiment has been chosen to illustrate the invention it will be understood by those skilled in the art that various changes and modifications can be made therein without departing from the scope of the invention as defined in the appended claims.

Claims (7)

1. Apparatus for indicating a pressure difference between two locations, the apparatus being of the type having a housing, a spring-urged pressure piston movable in said housing, opposite ends of said piston being coupled to the two locations, and a permanent magnet movable with the piston against the spring in response to increasing pressure differences, comprising a signal body composed at least in part of a ferromagnetic material coaxially disposed relative to one end of said piston in said housing; and a second spring urging said signal body away from said piston; and wherein said first spring urges said piston in relation to said signal body, the end of said piston facing said signal body being coupled to the pressure medium location having the greater pressure.

2. An apparatus according to claim 1 wherein said housing includes a chamber at the low pressure end of said piston and means defining a passage leading to the lower pressure location; said apparatus further comprising a valve member movably carried by said piston at the end facing away from said signal body, said valve member being movable to close said passage at increased pressure.

3. An apparatus according to claim 1 or 2, wherein said piston includes an annular groove coupled to the higher pressure location; and a damping flange between said groove and high pressure end of said piston.

4. An apparatus according to any preceding claim, wherein said housing comprises an insert body attachable to a pressure vessel, said insert body having a blind bore for receiving said piston.

5. An apparatus according to claim 4 and including a guide member surrounding said signal body and a transparent elastic hood attached to said guide member through which said signal body is visible.

6. An apparatus according to claim 4 and 5, wherein said guide member includes a hollow outer body and a plurality of radially inwardly extending ribs defining a cylindrical recess for guiding said signal body, said outer body having a stop collar with a central opening to permit protrusion therethrough of a portion of said signal body; and said signal body includes a shoulder for engaging said stop collar.

7. Apparatus substantially as hereinbefore described with reference to and as illustrated in the accompanying drawing.