US3811400A

US3811400A - Fluid operated alarm system

Info

Publication number: US3811400A
Authority: US
Inventors: B Smilg
Original assignee: Globe Safety Products Inc
Current assignee: Globe Safety Products Inc
Priority date: 1971-07-20
Filing date: 1972-07-21
Publication date: 1974-05-21
Anticipated expiration: 1991-05-21

Abstract

A whistle is actuated by a substantially constant low pressure gas supply which is also used for breathing equipment and which is obtained through a regulator connected to a high pressure gas supply. The actuation of the whistle is controlled by a valve system which opens to supply low pressure gas to the whistle when the pressure of the high pressure gas supply decreases to a predetermined level. In accordance with modifications of the invention, the whistle is also controlled in response to the demand for low pressure gas and is operated by either high or low pressure gas.

Description

United States Patent 1191 3,8 1 l ,400 Smilg I [4 May 21, 1974 [5 FLUID OPERATED ALARM SYSTEM 3,250,288 5/1966 Hammon 137/1163 3,311,125 3/1967 Beasley 1. 137/117 lhvehtor- Belllamln smug, Dayton, Ohlo 3,400,735 9/1968 Favors et 31.... 137/557 73 Assignee; Globe s f t products Inc, Dayton, 3,584,596 6/ 1971 Westcott 1 116/70 Ohio 3,611,981 10/1971 Warncke 116/70 [22] Filed: July 1972 Primary Examiner-Louis J. Capozi [21] APPL 27 Attorney, Agent, or Firm-Jacox & Meckstroth [63] C 'Relteq Us f S l: n 1 240 J 1 [57] ABSTRACT fi g sga ali 0 u y A whistle is actuated by a substantially constant low pressure gas supply which is also used for breathing [52 U.S. c1 116/70, 128/142.3, 137/557 equipment and which Obtained through a regulah [51 1111. C1. G011 19/12 Conneqed Q a high P gas supply- The actua- [58] Field of Search 116/70, 65, 112, 34 R, of the Whistle is Controlled y a valve System 116/117; 137/5571163; 128/1423 which opens to supply low pressure gas to the whistle i when the pressure of the high pressure gas supply de- [56] References Cited creases to a predetermined level. In accordance with modifications of the invention, the whistle is also con- UNITED T PATENTS trolled in response to the demand for low pressure gas 5 33???? 3: 2;: 116/34 R and is operated by either high or low pressure gas. 3,244,196 4/1966 Replogle 137/557 15 Claims, 3 Drawing Figures- I 62 1 f. I a5\ i l 93 52 66 as A- m {g5 44 so /04 5,2? 1?? I 45 6 98 10 3 25 9.9 82 2a 34 ,4

2 1 a E a4 74 ow /2 76 73 PRESSURE 77 FLUID 78 36 HIGH PRESSURE FLUID l9 PATENTEDMAY 21 I974 LOW PRESSURE FLUID 55 FIG.I

HIGH PRESSURE FLUID FIG.2Z36

1. FLUID OPERATED ALARM SYSTEM RELATED APPLICATION BACKGROUND OF THE INVENTION In safety breathing equipment such as the equipment used by personnel fighting fires, stopping riots, etc., air or pure oxygen, hereinafter referred to as a gas, is supplied to a breathing mask through a flexible line connected to a gas supply tank where the gas is pressurized to a substantially high level, for example, on the order of 2500 p.s.i. A pressure regulator is employed to supply the gas to a breathing mask at a substantially lower pressure, for example, on the order of 40 p.s.i. Usually, it is desirable for the breathing equipment to include an alarm system which is actuated when the pressure in the supply tank drops or decreases to a predetermined lower level, for example, around 500 p.s.i., thereby indicating that there is a limited supply of gas remaining in the supply tank. Preferably, the alarm system incorporates an audible whistle which begins blowing when the air pressure in the tank decreases to the predetermined lower level and continues to blow while the pressure is dropping to an even lower level, for example, 100 p.s.i.

In prior art alarm systems, the actuation of the whistle is controlled by a pressure responsive valve which is designed to open when the tank pressure arrives at the predetermined lower pressure, and the whistle is actuated by a gas supplied at the tank pressure. Thus, since the whistle is first actuated by gas which may be as high as 500 p.s.i. or more, it has been necessary to use a very small orifice in the gas passage connecting the supply tank to the whistle to minimize the loss of the pressurized gas during blowing of the whistle. This small orifice is subject to clogging by dirt or other small foreign particles,thereby preventing functioning of the alarm. It has also been found that precise tolerances must be maintained between the moving parts of the alarm system, and selective fitting of the parts isusually required, thus significantly increasing the manufacturing and repairing costs of the equipment. Furthermore, since the tank supply pressure is decreasing, for exampie, from 500 p.s.i. to I00 p.s.i. while the whistle is blowing, it is difficult to obtain an audible alarm signal at a pitch and loudness which remains substantially constant.

SUMMARY OF THE INVENTION The present invention is directed to an improved fluid alarm system which is ideally suited for safety breathing equipment. In accordance with one embodiment of the invention, a signal or alarm is actuated by a substantially constant low pressure fluid obtained through a regulator connected to a high pressure fluid supply, but the inactuation and determination of the actuation of the alarm is controlled directly by the pressure of the high pressure fluid supply. As a result, an alarm system of the invention produces an audible signal which remains substantially constant. In accordance with modifications of the invention, the alarm is operated by either high pressure fluid or the same low pressure fluid supplied to the breathing apparatus, and

2 the alarm is actuated only upon demand of the fluid so that the fluid required for operating the alarm is minimized. The alarm system of the invention also eliminates the need for maintaining precisely close tolerances in the manufacturing of the movable components of the alarm system and thereby provides for convenient assembly and servicing of the components.

Other features and advantages of the invention will be apparent from the following description, the accompanying drawing and the appended claims.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is an axial section view of a fluid operated alarm system constructed in accordance with the invention and showing substantially all of the internal components;

FIG. 2 is a fragmentary axial section showing a modified alarm system also constructed in accordance with the invention; and

FIG. 3 is a fragmentary section showing another modification of the alarm system.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The alarm system shownin FIG. I includes a body 10 having an upwardly projecting cylindrical portion 12 with external threads and defining a cavity or chamber 14. A passage 16 extends downwardly from the cham- I threads and receives a hollow fitting 24 forming part of a pressure regulating device 25. As shown, the pressure regulating device 25 is constructed in a manner similar to that disclosed in u. s. Pat. No. 3,250,288, however, it is to be understood that the pressure regulating device may be constructed in another form without departing from the scope of the invention.

The fitting 24 defines a tapering orifice 28 of circular cross-section and which connects the chamber 14 to a cylindrical bore or chamber 29 formed within the fitting 24 and open at the bottom to the chamber 22. A'

spool-like valve plunger or member 32 is located within the chamber 29 and includes hexagonal end portions 33 which provide for the passage of high pressure gas from the chamber 22 through the chamber 29. The valve member 32 includes an upper frusto-conical tip portion 34 which normally closes the bottom of the orifice 28 as a result of an upward force exerted on the valve member 32 by a compression spring 36 extending from the bottom of the chamber 22 upwardly into a bore (not shown) in the valve member 32.

A circular flexible diaphragm 40 includes an outer peripheral portion 41 which seats on an O-ring 42 recessed within an annular cavity 43 formed within the upper end surface of the body portion 12. The diaphragm 40 also includes a generally cylindrical hollow hub portion 44 in which is inserted a rigid valve actuator 45 having a lower tapering tip portion 46 which extends into the orifice 28 for engagement with the upper tip portion 34 of the valve member 32. The peripheral 3 portion 41 of the diaphragm 40 is urged into sealing relation with the O-ring seal 43 by an annular retaining plate 48 and a compression spring 50. The spring 50 extends between the retaining plate 48 and a radial shoulder 52 formed within a hollow cap member 55 which has an internally threaded lower end portion engaging the upwardly projecting cylindrical portion 12 of the 7 body 10.

An annular plate 56 surrounds and engages the hub portion 44 of the diaphragm 40 and is located concentrically within the annular retaining member or plate As disclosed in the above patent, the spring 58 cooperates with the diaphragm 40 and valve actuator 45 to provide for maintaining the fluid or gas within thechamber 14 at a substantially constant pressure. That is, when the pressure within the chamber 14 drops below the desired level as determined by the setting of the plug member 60 within the cap member 55, the

valve actuator 45 lowers and depresses the valve member 32 downwardly so that gas flows from the high pressure chamber 22 into the lower pressure chamber 14. When the gas pressure within the chamber 14 reaches the predetermined desired level, the diaphragm 40 and the valve actuator 45 move upwardly causing the upper tip portion 34 of the valve member 32 to restrict further or close the orifice 28, thereby creating a balanced pressure condition between the

chambers

14 and 29 and producing a substantially constant pressure within the chamber 14.

ln the event that a foreign particle prevents the valve member 32 from completely closing the orifice 28 so that the pressure within thecha'mber 14 substantially exceeds the predetermined tower level, the retaining member 48 and the outer peripheral portion 41 of the diaphragm 40 will move upwardly from the O-ring seal 42. This permits the high pressure gas to escape into the cap member 55 and exhaust through a lateral port 66 formed withinthe. cap member 55. The pressure required to lift the peripheral portion 41 of the diaphragm, 40 from the seal 42, is determined by the downward force exerted by the compression spring 50. This force may be adjusted simply by rotating the cap member 55 and adjusting its axial position relative to the body 10.

In accordance with the present invention, the body includes an upwardly projecting cylindrical portion 70 in which is formed an elongated cavity or chamber 72. A passage 73 extends from the lower end of the chamber 72 to the high pressure gas chamber 22. The intermediate portion of the chamber 72 is connected by a passage 74 to the low pressure chamber 14 defined within the cylindrical portion 12 of the body 10. A plunger-like valve member 76 is slidably mounted within the lower end portion of the chamber 72, and a split rigid washer 77 and a resilient O-ring 78 form a gas tight seal between the valve member 76 and the lower end portion of the chamber 72. The valve member 76 includes an upwardly projecting cylindrical portion 79 which has a flat upper end surface 82 and receives a compression spring 84.

An audible alarm device in the form of a whistle 85 includes a body 86 which has a lower tubular end portion 87 threaded into the upper end portion of the chamber 72. A resilient O-ring 89 forms a fluid tight seal between the body 86 of the whistle 85 and the cylindrical portion 70 of the body 10. A stepped cylindrical bore or cavity 92 is formed within the whistle body 86 and is intersected by a notch 93 forming a sharp tapering edge 94. A fitting 96 is inserted within the lower portion 87of the whistle body 86 and is sealed therewith by an O-ring 98 which is retained within a peripheral groove located adjacent the lower end portion 99 of the fitting 96. A part spherical seat 101 forms the lower end surface of the fitting 96, and a passage 102 extends axially from the center of the seat 101 to a radially extending port 104. A slot 105 is formed within the outer surface of the fitting 96 and extends axially from the port 104 to the notch 93 directly under the tapering edge 94 on the whistle body 86.

' The alarm system or device described above operates in the following manner. The opening 19 is connected by a line to a high pressure gas supply which is stored within a tank at a high pressure such as 2,500 p.-s.i. This high pressure gas is conducted by the passage 73 to the lower end of the valve member 76 and causes the valve member to shift upwardly against the bias of the spring 84 to a position where the end surface 82 of the valve member effectively closes the lower end of the passage 102 within the fitting 96 of the whistle 85. The regulator 25 is set or adjusted so that a low gas pressure such as 40 psi. is maintained within the chamber 14.

This low pressure gas is supplied through the passage 16 and opening 17 to a linewhich'connects with a breathing mask as mentioned above. When the pressure of the high pressure gas supply within the chamber 22, drops to a predetermined lower level such as 500 p.s.i., the compression spring 84 is effective to shift the .valve member 76 downwardly so that low pressure airis supplied from the chamber 14 through the passage 74 and chamber 72 to the opened passage l02with-in the whistle fitting 96. The low pressure gas escapes through the port 104 and slot 105 for effectively blowing the whistle to produce an audible alarm.

As mentioned above, it is desirable for the whistle 85 to continue blowing while the pressure-in the supply tank drops from 500 p.s.i.-to a lower level such as psi. Since the valve member 76 remains in its open position as shown in FIG. 1 during this period, the whistle 85 continues to blow as a result of the continued supply of low pressure gas from the chamber 14.

Another embodiment of a fluid operated alarm system or device constructed in accordance with the invention is shown in FIG. 2. This embodiment incorpo- The alarm system or device shown in FIG. 2, operates only when there is a demand for low pressure gas such as when the person wearing the breathing mask inhales.

Thus the whistle alarm is actuated only when the v high pressure supply fluid or gas drops to a predetermined level and low pressure gas is demanded by the person wearing the breathing mask.

As shown in FIG. 2, a threaded bore or cavity 210 is formed within the body 110 extending inwardly from the chamber 114. The cavity 210 is connected by a passage 212 which opens into the chamber 172 and which functions in the same manner as the passage 74 shown in FIG. 1, that is, to conduct low pressure gas from the chamber 114 to the chamber 172. A control valve 215 includes an inverted cup-shaped fitting 216 which is threaded into the cavity 210 and includes an annular array of small openings or holes 217 within its top wall. The fitting 216 retains a washer-like plate 218 which is positioned within the bottom of the cavity 210 and includes a central orifice 219 having a predetermined diameter selected to limit the maximum flow of gas through the passage 212.

A valve member 225 is supported for axial movement within the fitting 216 and includes a hexagonal head which supports a resilient annular washer 227. The washer 227 is effective to seal or close the holes 217 in response to upward pressure exerted on the valve member 225 by a compression spring 230 seated on the plate 218 within the fitting 216. The valve member 225 includes a stem 232 which projects upwardly through a center hole within the top wall'of the fitting 216. An adjustable cap-like nut 234 is threadedly connected to the stern 232 and is adapted to engage the underneath surface ofa rigid disc-like plate 236 forming part of the actuator 145.

The embodiment shown in FIG. 2 operates in the following manner. When the pressure of the high pressure gas received within the inlet opening 119 drops to a predetermined level, for example, 500 p.s.i. as mentioned above, the valve member 176 moves downwardly within the chamber 172 as a result of the force exerted by the compression spring 184. The downward movement of the valve member 176 opens the inlet to the whistle alarm 185 for actuation by any low pressure gas within the chamber 172. The control valve 215 prevents the flow of low pressure gas from the chamber 114 through the passage 212 to the chamber 172 until the diaphragm actuator 145 moves downwardly as a result of the decreased gas pressure in chamber 114 resulting when the person wearing the breathing mask inhales.

When the pressure in the chamber 114 begins to decrease. the diaphragm actuator 145 moves slightly downwardly so that the tip portion 146 depresses the valve member 134, and gas flows from the chamber 129 through the orifice 128 and into the chamber 114 in a manner as described above. The downward movement of the actuator plate 236 also engages the adjustable cap nut 234 and depresses downwardly on the valve member 225 so that the low pressure gas within the chamber 114 flows downwardly through the holes 217 within the fitting 216 and past the head ofa valve member 225, through the restriction orifice 219 and through the passage 212 into the chamber 172 for actuating the whistle alarm 185.

When the demand for lowpressure gas within the chamber 114 ceases at the end of the inhalation, the diaphragm actuator plate 236 rises, and the spring 230 moves the valve member 225 upwardly to close the flow of gas through the holes 217. Thus the alarm 185 is only actuated when the pressure of high pressure gas within the supply tank, drops to a predetermined lower level and a demand is made for low pressure gas from the chamber 114. Thus an alarm is produced only when the person wearing the breathing equipment inhales.

Referring to the modification shown in FIG. 3, the signal device or whistle 185 is mounted within a body 240 and is actuated by high pressure fluid or gas which is supplied to the passage 212 and the chamber 172 from the passage 173 in response to actuation of a control valve 245 by the diaphragm actuator 145. The valve 245 includes a tubular fitting 246 which retains a cylindrical valve seat member 248 within a stepped bore or chamber 249. The fitting 246 includes a center passage 251 which is connected by a series of radial ports or passages 253 to a peripherally extending groove 254 aligned with the passage 212.

A valve stem or member 256 extends'through the fitting 246 and seat member 248, and is sealed to the seat member 248 by an O-ring seal 257. The lower head or end portion of the valve member 256 supports an annular resilient washer 269 which normally closes the passage 251 in response to the force exerted upwardly on the valve member by the gas within the passage 249 and by a compression spring 261. An adjustable caplike nut 262 is threaded onto the upper end portion of the valve member 256 in the same manner as the nut 234 is mounted on the upper end portion of the valve member 225 shown in FIG. 2, and is adapted to be engaged by the diaphragm actuator 145.

When the valve member 256 is momentarily depressed downwardly in response to downward movement of the diaphragm actuator 145 during a period of inhalation, the valve 245 opens, and high pressure air flows through the

passage

251, 253 and 212 into the chamber 172. Thus when the pressure of the gas within the supply tank and passage 173 reduces to the predetermined lower value; the valve member 179 opens, and the whistle 185 is actuated or pulsed during each period of inhalation by gas supplied from the passage 173.

From the drawing of the abovedescription, it is apparent that an alarm system or device constructed in accordance with the present invention, provides desirable features and advantages. One important feature is provided by the fact that the alarm or whistle -0r 185 in the embodiments of FIGS. 1 and 2, is .actuated by low pressure gas which is supplied by the regulator 25 or at a substantially constant pressure. As a result, the audible alarm operates with a minimum loss of gas and at a uniform loudness even though the pressure of the high pressure gas supply continues to drop. Thus the whistle 85 or is designed to operate at the same pressure at which the gas is supplied to the breathing mask. This lower pressure operation of the whistle eliminates the need for a substantially small orifice within the gas supply passage to the whistle. Furthermore, since the whistle operates at a substantially constant low pressure, the components of the whistle may be made with greater tolerances thereby enabling the components to be more economically manufactured, assembled and services.

In reference to the embodiment shown in FIGS. 2 and 3, as mentioned above, the alarm is actuated only when the person wearing the breathing mask inhales." As a result, this embodiment provides the feature of a substantial reduction in the use of either low or high pressure gas for actuating the alarm or whistle 185. In

- addition, the person'wearing the breathing mask has should soon obtain another supply tank of. pressure gas.

While the forms of alarm system herein described I constitute preferred embodiments of the invention, it is to be understood that the invention is not limited to these precise forms of system, and that changes may be made therein without departing from the scope and spirit of the invention, as defined by the following claims. I

Theinvention having thus beendescribed, the following is claimed:

' l. A fluid operated alarmsystem comprising means defining first and second passages,-means for directing to said .first passage a high pressure fluid which varies in pressure, means for supplying fluid'from said first passage to said second passage and for maintaining the fluid in said second passage at a substantially constant pressure lower than the pressure of the fluid within said first passage, a fluid actuated signal device connected to said second passage, and means for controlling the supply of low pressure fluid from said second passage to said signal device and for actuating said signal device in response to a predetermined pressure of the high pressure fluid within said first passage.

2. A fluid-operated alarm system comprising means defining a high pressure fluid passage adaptedto be connected to a supply of high pressure fluid which changes in pressure, means defining a low pressure fluid passage, pressure regulating means for supplying low pressure fluid at a substantially constant pressure to said low pressure fluid passage fromsaid high pressure fluid passage, a signal device adapted to beactuated by low pressure fluid and connected to said low pressure fluid passage, and valve means for controlling the supply'of low pressure fluid to said signal .device and for actuating said signal device in response to a range of pressures of the fluid in said high pressure fluid passage when the range is below a predetermined value.

3. An alarm system as defined in claim 2 wherein said valve means includes means defining a valve -chamber connected tb said signal device, a valve member movable within said chamber between a position closing the supply of low pressure fluid to said signal device and an open position permitting low pressure to actuate said device, spring means for urging said valve member toward said open position, and means defining a passage for directing fluid from said high pressure passage to said chamber at a location to urge said valve member toward said closed position.

4. An alarm system as defined in claim 2 wherein said signal device is effective to produce an audible sound, and a body supporting said device and said pressure regulating means.

5. An alarm systemas defined in claim 4 wherein said pressure regulating means and said signal device have corresponding axes and are arranged on said body with said axes in parallel spaced relation.

6; An alarm system as'definedin claim Zincluding means for connecting said low pressure fluid passage to a breathing apparatus, means for adjusting said regulating means to set the pressure of the fluid within said low I means for directingto said first chamber a high pressure fluid which varies in pressure, pressure regulating means for supplying fluid from said first chamber to said second chamber and for maintaining the fluid in said second chamber at a substantially constant pressure lower than the pressure of the fluid within said first chamber, a fluid actuated whistle connected to said body, means defining a passage connecting said whistle to said second chamber, and valve means in said latter passage for controlling the supply of substantially constant low pressure fluid from said second chamber to said whistle in response to a change in the pressure of the high pressurefluid within said first chamber.

8. An alarm system as defined in claim 7 wherein said latter passage comprises a third chamber within said body and connected to said whistle, a valve member slidably disposed within said third chamber, said valve member being movable between a closed position blocking the flow of low pressure fluid from said second chamber to said whistle and an open position permitting such flow, means defining a passage within said body for connecting said first chamber to said third chamber permitting the high pressure fluid to urge said chamber adapted to be connected to a breathing device which requires low pressure fluid, pressure regulating means for supplying fluidfrom said first chamber to said chamber and for maintaining the fluid in said second chamber at a lower pressure than the pressure of the fluid in said first chamber, means defining a third chamber, a fluid actuated signal device connected to said third chamber, means defining a passage connecting one of said first and second chambers to said third chamber, and valve means associated with said third chamber for controlling the flow of fluid through said passage and for actuating said signal device in response to a predetermined range of pressures of the fluid in said first chamber. 7 I i 10. A fluid operated alarm system comprising means defining a first chamber. adapted to be connected to a supply of high pressure fluid, means defining a second chamber adapted to be connected to a breathing device which requires low pressure fluid, movable pressure regulating means for'supplying fluid from said first chamber to said second chamber and for maintaining.

the fluid in said second chamber at a lower pressure than the pressure of the fluid in said first chamber, a

said signal device, and valve means actuated by movement of said pressure regulating means for controlling the flow of fluid through said passage to said signal device.

ll. A fluid operated alarm system as defined in claim 10 wherein said valve means include a normally closed control valve disposed to control the flow of fluid to said signal device, and means for opening said control valve in response to operation of said pressure regulating means upon demand for low pressure fluid from said second chamber.

12. A fluid operated alarm system as defined in claim 11 wherein said pressure regulating means includes a movable actuating member, said control valve includes a valve member movable between a closed position and an open position, and said valve member is movable to said open position in response to engagement by said movable actuating member.

13. A fluid operated alarm system as defined in claim 12 wherein said valve member includes adjustment means providing for selecting the extent of movement of said actuating member required to effect movement of said valve member to said open position.

14. A fluid operated alarm system comprising a body having means defining first and second chambers, means for directing to said first chamber a high pressure fluid which varies in pressure, movable pressure regulating means for supplying fluid from said first chamber to said second chamber and for maintaining the fluid in said second chamber at a generally constant pressure lower than the pressure of the fluid within said first chamber, means defining a third chamber within said body, a fluid actuated alarm connected to said third chamber, a valve member slidably disposed within said third chamber and being movable between a closed position blocking the flow of fluid from said third chamber to said alarm and an open position permitting such flow, a first passage within said body for connecting said first chamber to said third chamber to permit the high pressure fluid to urge said valve member towards said closed position, spring means for urging said valve member towards said open position when the pressure of the fluid in said first chamber drops to a predetermined level, and a second passage within said body for supplying fluid from one of said first and second chambers to said third chamber.

15. A fluid operated alarm system as defined in claim 14 including a control valve disposed within said second passage, and means for actuating said control valve in response to movement of said pressure regulating means.

Claims

1. A fluid operated alarm system comprising means defining first and second passages, means for directing to said first passage a high pressure fluid which varies in pressure, means for supplying fluid from said first passage to said second passage and for maintaining the fluid in said second passage at a substantially constant pressure lower than the pressure of the fluid within said first passage, a fluid actuated signal device connected to said second passage, and means for controlling the supply of low pressure fluid from said second passage to said signal device and for actuating said signal device in response to a predetermined pressure of the high pressure fluid within said first passage.

2. A fluid operated alarm system comprising means defining a high pressure fluid passage adapted to be connected to a supply of high pressure fluid which changes in pressure, means defining a low pressure fluid passage, pressure regulating means for supplying low pressure fluid at a substantially constant pressure to said low pressure fluid passage from said high pressure fluid passage, a signal device adapted to be actuated by low pressure fluid and connected to said low pressure fluid passage, and valve means for controlling the supply of low pressure fluid to said signal device and for actuating said signal device in response to a range of pressures of the fluid in said high pressure fluid passage when the range is below a predetermined value.

3. An alarm system as defined in claim 2 wherein said valve means includes means defining a valve chamber connected to said signal device, a valve member movable within said chamber between a position closing the supply of low pressure fluid to said signal device and an open position permitting low pressure to actuate said device, spring means for urging said valve member toward said open position, and means defining a passage for directing fluid from said high pressure passage to said chamber at a location to urge said valve member toward said closed position.

5. An alarm system as defined in claim 4 wherein said pressure regulating means and said signal device have corresponding axes and are arranged on said body with said axes in parallel spaced relation.

6. An alarm system as defined in claim 2 including means for connecting said low pressure fluid passage to a breathing apparatus, means for adjusting said regulating means to set the pressure of the fluid within said low pressure fluid passage at a predetermined pressure corresponding to the desired pressure for the breathing apparatus, and said signal device is effective to produce an audible signal of substantially constant loudness in response to a supply of fluid at said predetermined pressure.

7. A fluid operated alarm system comprising a body having means defining first and second chambers, means for directing to said first chamber a high pressure fluid which varies in pressure, pressure regulating means for supplying fluid from said first chamber to said second chamber and for maintaining the fluid in said second chamber at a substantially constant pressure lower than the pressure of the fluid within said first chamber, a fluid actuated whistle connected to said body, means defining a passage connecting said whistle to said second chamber, and valve means in said latter passage for controlling the supply of substantially constant low pressure fluid from said second chamber to said whistle in response to a change in the pressure of the high pressure fluid within said first chamber.

8. An alarm system as defined in claim 7 wherein said latter passage comprises a third chamber within said body and connected to said whistle, a valve member slidably disposed within said third chamber, said valve member being movable between a closed position blocking the flow of low pressure fluid from said second chamber to said whistle and an open position permitting such flow, means defining a passage within said body for connecting said first chamber to said third chamber permitting the high pressure fluid to urge said valve member towards said closed position, spring means for urging said valve member towards said open position when the pressure of the fluid in said first chamber drops to a predetermined level.

9. A fluid operated alarm system comprising means defining a first chamber adapted to be connected to a supply of high pressure fluid, means defining a second chamber adapted to be connected to a breathing device which requires low pressure fluid, pressure regulating means for supplying fluid from said first chamber to said chamber and for maintaining the fluid in said second chamber at a lower pressure than the pressure of the fluid in said first chamber, means defining a third chamber, a fluid actuated signal device connected to said third chamber, means defining a passage connecting one of said first and second chambers to said third chamber, and valve means associated with said third chamber for controlling the flow of fluid through said passage and for actuating said signal device in response to a predetermined range of pressures of the fluid in said first chamber.

10. A fluid operated alarm system comprising means defining a first chamber adapted to be connected to a supply of high pressure fluid, means defining a second cHamber adapted to be connected to a breathing device which requires low pressure fluid, movable pressure regulating means for supplying fluid from said first chamber to said second chamber and for maintaining the fluid in said second chamber at a lower pressure than the pressure of the fluid in said first chamber, a fluid actuated signal device, means defining a passage connecting one of said first and second chambers to said signal device, and valve means actuated by movement of said pressure regulating means for controlling the flow of fluid through said passage to said signal device.

11. A fluid operated alarm system as defined in claim 10 wherein said valve means include a normally closed control valve disposed to control the flow of fluid to said signal device, and means for opening said control valve in response to operation of said pressure regulating means upon demand for low pressure fluid from said second chamber.