US2688300A - Alarm system - Google Patents

Description

M. "r. WORKS ALARM SYSTEM Filed June 29, 1949 mm v f M W987 5 m WV M IfiI I M I f- M 1 U I I U I N W J J g 7 M 5 a w a J l] a 0 a W.

Sept. 7, 1954 A TTORNEYJ Patented Sept. 7, 1954 UNITED STATES PATENT OF F I CE 3 Claims.

This invention relates to improvements in low pressure alarms and a novel valve mechanism therefor and refers more particularly to a system for giving an alarm when the pressure within a gas pressure system drops below a predetermined limit.

In many fluid pressure systems, it is customary to employ an alarm to indicate a drop in pressure within the system below some predetermined minimum to facilitate maintenance of satisfactory pressure levels within the system. These alarms are of two general types, one type being electrical and the other type being fluid operated. While electrical alarms operate with a degree of satisfaction, they are expensive and their opera tion necessarily depends upon a source of electric current which is not always reliable or readily available. Mechanical or pressure actuated alarms have been devised which are reliable from the standpoint of giving the alarm but which are objectionable as wasting large volumes of pressure fluid and also in requiring a manual resetting of the alarm each time it is actuated.

An object of this invention is to provide an alarm for pressure systems which is actuated by the pressure of the gas in the system, which is fully automatic in giving an alarm when the pressure drops below normal and resetting when the pressure within the system is restored to normal.

Another object is to provide an alarm for pressure systems which is actuated by the pressure in the system and which is very miserly of the gas of the system.

A further object is to provide an alarm for pressure systems wherein the alarm employs a novel valve assembly which in operation, upon occurrence of predetermined low pressure conditions within the systems will alternately open and close and which thereby permits escape of only a small amount of the gas of the system pro tected.

Still another object is to provide an alarm for pressure systems employing a novel valve assembly wherein the main valve controlling flow through the alarm is forced open by resilient means when the pressure within the systems falls below a pre-selected value and is then closed by a separate pressure actuated means.

A still further object is to provide an alarm for a pressure system which will provide a continuous alarm when the pressure in the system is between pro-selected low pressure limits and will automatically close when the pressure within the system is outside these limits.

Yet another object is to provide a valve assembly for controlling flow through a conduit in response to the upstream pressure in the conduit wherein the valve member is urged toward seated position by the pressure controlled and is unseated by a resilient means when the pressure controlled falls below a pre-selected value and additional means, responsive to the pressure controlled, is provided to reseat the valve member when the controlled lected value.

Other and further objects of this invention will appear from its description.

In the accompanying drawings, which form a part of the instant specification, are to be read in conjunction therewith and wherein like reference numerals indicate like parts in the various views:

Fig. 1 is an elevational view, partially in vertical section, of an alarm illustrating an embodiment of this invention; and

Fig. 2 is a sectional view, upon an enlarged scale, showing the details of the novel valve assembly of the device shown in Fig. 1.

The device shown in the drawings is a whistle type alarm adapted to give a shrill whistle when the pressure within a pressure system drops below a predetermined value. The alarm is such, that when the pressure within the system protected returns to a value above the set point for the alarm, the control valve of the alarm will automatically close and the whistle will stop blowing.

The device comprises parts forming a conduit connectable to the pressure system to be protected. These parts include a coupling 5 having a threaded socket in its lower end adapted to be connected to a pressure system to be protected. The other end of the coupling 5 is also threaded to receive a stem 6 having a central passage 7 forming a part of the conduit and communicating through a radial passage 8 with an annular space 9 formed between the inner wall of coupling 5 and the periphery of stem 6. This space 9 communicates through a narrow annular passage l0 with the exterior of the device at a position just below the open end of whistle element II. The whistle element is threaded on the exterior of stem 6, and by rotation of the element upon the stem, its position relative to passage l0 may be adjusted to vary the tone of the whistle. A cap [2 is threadedly connected to the upper end of stem 6 and provides a cap for a pressure adpressure is above a pre-selusting screw I3 to be hereinafter more fully described. It is contemplated that the cap l2 and whistle element ll may be integrally formed but the two piece arrangement is preferred in order that screw l3 can be adjusted without disturbing the whistle setting. Also, the cap in this arrangement acts as a jamb nut for the whistle element.

It is to be understood that the entire whistle and valve arrangement may be located at a great distance from the vessel protected and connected thereto by a pipe connected to the lower end of coupling 5 or the passage 8 may lead to a whistle element that is located remote from the valve mechanism controlling passage 7.

A valve assembly is housed within the conduit and more particularly within coupling 5 which controls flow through passage l. This assembly includes a seat [4 formed on the lower end of stem 6 and a valve member l adapted to engage the seat to control flow through the conduit. Inasmuch as the valve member is located in the conduit upstream from the seat [4, the pressure to be controlled urges the valve member toward seated position. A resilient means, which may include a coil spring I6, is arranged to urge the valve member l5 ofi of its seat.

The resilient means referred to preferably is such as to provide an adjustable force tending to unseat the valve member, in order that the pressure at which the alarm will be energized may be adjusted or selected. In order to accomplish this, the spring may abut the lower end of spacer El extending axially within the central passage through stem 6. The other end of the spacer abuts the lower end of pressure adjusting screw i3 which is threaded through the upper end of stem 5. The screw may carry a jamb nut [9 adapted to lock the adjusting screw in a selected position. With this arrangement, rotation of the adjusting screw will change the compression on coil spring Hi to vary the unseating force acting against valve member 15.

The valve assembly includes a means for imparting a reseating force against the valve mem-I ber when flow of fluid is established through the conduit. This reseating means may in addition serve as a choke to substantially limit flow through the conduit whereby the alarm is very miserly of the pressure fluid in the system protected. This means may include a pressure responsive member as, for example, a piston-like member or sleeve slidably mounted within the conduit.

The inner wall of coupling 5 is provided with two cylindrical portions 2| and 22 joined to-,

gether by a tapered seat portion 23. The pressure responsive member 28 is provided with cor-.

responding outer peripheral portions. The crossseotional area of cylindrical portion 22 is greater than the area across seat I4 so that the pressure controlled, acting against the lower end of sleeve 20, upon opening of valve [5, forces the sleeve in a direction to return ball 15 to seated position.

It is preferred to provide the valve member and pressure responsive member as separate parts. A weak spring 24 may be employed between the valve member and sleeve 23 whose purpose is to return sleeve 20 to seated position against seat 23 when the valve member is in seated position and the pressure has equalized about the sleeve. This seating of the sleeve is more of a stop and does not positively provide a seal. Spring 24 may have only sufficient strength for this purpose. The arrangement is such that the tapered shoulder 25 within the socket of sleeve 20 engages ball IS, on unseating of the ball, so that movement of the sleeve under the influence of the pressure differential which develops across the sleeve, when the valve member is unseated, returns the valve member to seated position.

The narrow diameter cylindrical portion of sleeve 20 should have a close fit within portion 22 of the conduit. The looseness of this fit Will afiect the frequency of the sounded alarm and also will govern to a large degree the amount of pressure fluid lost due to the giving of the alarm. The clearance between the sleeve and cylinder 22 should be such as to permit free sliding movement of the sleeve within the conduit, but should be such as to provide a very small annular orifice to materially restrict the flow of fluid therepast. In any event, the area of this orifice should be materially less than the area within seat I4. This latter is true in order that the pressure downstream from the sleeve, upon unseating of the valve member, will quickly vent to provide a pressure differential for actuating the sleeve.

By way of example only, but not by way of limitation, certain dimensions for the O. D. of the sleeve and the I. D. of cylinder 22 will be given which have been found entirely satisfactory for use upon a whistle type low pressure alarm for air resorvoirs commonly found in connection with compressed air system. Where the I. D. of the conduit within cylindrical portion 22 ranges between .514 inch and .516 inch, the O. D. of the sleeve may range between .511 inch and .512 inch. Due to the annular character of the orifice thus provided and to the constant movement of sleeve 20 when an alarm is given, there is very little likelihood of the small area orifice becoming clogged with debris or the like.

In operation, it will be assumed that the coupling 5 is connected to a gas pressure system to be protected, in order that occurrence of a low pressure within the system will be called to the attention of the person in charge of the system. Assuming that the pressure within the system is above the preselected set point for the giving of the alarm, the valve member IE will be held against seat I4 and the pressure will be equalized on both ends of sleeve 2a because seat 23 does not provide an absolute seal. The valve member will be subjected to the force of the spring tending to unseat the valve and the force of the pressure controlled holding the valve seated. Then as the pressure reduces within the system protected, it will also reduce about valve 15 because seat 23 does not provide a perfect seal. Thus the seating force reduces, and when this is overcome by the constant pre-selected force of the resilient unseating means, the valve member will move oif of its seat. In the embodiment shown, the ball [5 will drop into the socket of sleeve 20 and be held against shoulder 25 by the force of spring [6.

With the valve opened, the pressure downstream of sleeve 20 is quickly vented creating a pressure differential across the sleeve. The fluid discharged by this venting sounds the alarm. The differential will be substantially the same difierential to which the seated valve member was subjected at the time the valve was forced from its seat. However, due to the greater crosssectional area or eifective area of the sleeve, a force will be exerted against the valve member tending to seat it, which is greater than the force due to the resilient unseating means. Thus, the valve member will be automatically and quickly returned to seated position. The alarm is sounded during this interval when the valve member I5 is opened, for a rush of fluid through the interior of stem 6, passages 8, 9 and I9 and into and about the whistle I I will cause the emission of a shrill sound.

When the valve member is seated again by sleeve 20 subjected to the pressure within the system protected, the pressure will quickly equalize about the sleeve and the weak spring 24 will return the sleeve toward shoulder 23 which limits its travel away from seat [4. As long as the pressure of the system protected is below the set point of the resilient unseating means, the valve member [5 will again be unseated and the reseating operation will repeat. The affect of this will be a resulting intermittent shrill whistle which will continue as long as the pressure within the conduit is less than the pressure setting on spring I 6, but is great enough so that the force of the pressure against sleeve 20 will overcome spring I6. On the other hand, when the pressure drops below that point at which it will return sleeve 26 against the spring, a continuous whistle will sound and this will indicate to the operator of the pressure system that the pressure has fallen below not only the set pressure but some lower preselected pressure. On the other hand, when the pressure within the conduit increases to one greater than the setting of spring E6, the valve member I 5 will remain in seated position when returned thereto by sleeve 20 under the influence of the pressure controlled.

The diameter of sleeve 29 and the strength of spring It may be selected so that when the conduit pressure upstream of sleeve 20 falls below a pre-selected-low value, the spring IE will urge the sleeve against seat 23 closing off the conduit to prevent further dissipation of gas from the system. Still seat 23 will not provide an absolute seal, but will reduce the rate of flow of fluid therepast far below the rate required to blow the whistle. The slight leakage past seat '23 is entirely sufficient to allow the pressure within the chamber about valve l5, which is of small capacity relative to the volume of the system protected, to reflect substantially the pressure within the system, which in turn will normally rise or fall slowly. Of course, in any event sleeve 20 will not seat until an entirely adequate alarm has been given.

It will be seen that the objects of this invention have been accomplished. There has been provided a fully automatic low pressure alarm which will give an alarm when the pressure within a pressure system drops below some preselected value and which will automatically discontinue the alarm when the pressure within the system rises above this value. The construction is such that very little pressure fluid is dissipated from the pressure system because of the giving of the alarm. The arrangement is such that an alarm will be given as long as the pressure within the system resides within a preselected low pressure range but that the character of the alarm will change when the pressure within the system falls below an intermediate value in the range. Upon occurrence of a pressure within the system less than the lower limit of the range, the valve mechanism may be arranged so as to close preventing further dissipation of gas, but this does not. occur until an adequate alarm has been given.

It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims.

As many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

The invention having been described, what is claimed is:

1. A low pressure alarm for pressure systems comprising a conduit connectable with the System, fluid actuated alarm means connected to the conduit and actuated by fluid flow therethrough, a valve assembly controlling flow through the conduit in response to the pressure therein upstream of the assembly, said assembly including a seat in the conduit, a valve member disposed upstream thereof and urged thereagainst by the line pressure, a first resilient means urging the valve member toward open position with a preselected force, a pressure responsive member having an effective pressure area greater than the area across the valve seat movable with respect to said valve member, said pressure responsive member exposed to the pressure within the conduit upstream of the valve member and substantially restricting the conduit whereby upon unseating of the valve member the upstream pressure moves the pressure responsive member toward the valve seat to force the valve member to seated position, and a second resilient means engaging the valve and pressure responsive member and urging the valve and pressure responsive member apart.

2. The alarm of claim 1 wherein the second resilient member is a weak spring which moves the pressure responsive member away from the valve member when the valve member is seated.

3. The subcombination of a valve assembly for automatically controlling flow through a conduit in response to pressure conditions in the conduit comprising, a valve seat in the conduit, a valve member upstream thereof urged against the seat by the upstream pressure, resilient means urging the valve member toward unseated position with a predetermined force, and pressure responsive means in the conduit upstream of the valve member obstructing flow therepast to an amount less than the flow of pressure fluid past the valve member when open to provide a pressure drop across the pressure responsive member upon opening of the valve to move it toward the valve seat, said pressure responsive member engaging the unseated valve and having a pressure face of greater area than the area of the valve seat whereby it will return the valve to its seat, resilient means disposed between and engaging the pressure responsive member and valve urgin the pressure responsive member in an upstream direction to increase the volume of the chamber defined in part by the valve seat and the pressure responsive member, said resilient means between the valve and pressure responsive member being weaker than the resilient means urging the valve 01f its seat whereby the valve when cracked from its seat will move into engagement with the pressure responsive member.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 257,069 Reznor Apr. 25, 1882 569,943 Shirley Oct. 29, 1896 777,538 Puckett Dec. 13, 1904 842,160 Aikman Jan. 29, 1907 1,220,419 Hawley Mar. 27, 1917 1,966,854 Eskilson July 17, 1934 2,041,198 McLean May 19, 1936 2,351,035 Grant June 13, 1944 2,372,408 Trick Mar. 2'7, 1945 2,389,887 Baxter Nov. 27, 1945 2,404,924 Sacchini July 30, 1946 FOREIGN PATENTS Number Country Date 374,332 Italy of 1939

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