US2654388A

US2654388A - Backflow preventer

Info

Publication number: US2654388A
Application number: US562304A
Authority: US
Inventors: Glass Ann Thesing
Original assignee: Individual
Current assignee: Individual
Priority date: 1944-11-07
Filing date: 1944-11-07
Publication date: 1953-10-06
Anticipated expiration: 1970-10-06

Description

Oct. 6, 1953 Filed Nov. 7, 1944 T. A. GLASS 2,654,388

BACKFLOW PREVENTER 3 Sheets-Sheet 1 T. A. GLASS BACKFLOW PREVENTER 3 Sheets-Sheet 2 Oct. 6, 1953 Filed Nov. 7, 1944 #la E 1". A. GLAss BACKFLOW PREVENTER Oct. 6, 1953 3 Sheets-Sheet 3 Filed Nov. 7, 1944 IQ M Figs. 6 and 7 show the device in full open and in nearly closed positions, respectively.

Figs. 8 and 9 show modified forms of the disk and ring,

Fig. 10 shows a modified valve.

In Fig. 1 is shown my preferred form of back flow preventer, including a main valve body ill thru which fluid passes from the inlet II to the outlet [2, past a check valve which is closed during periods of no flow and whenever the outlet pressure equals or exceeds the inlet pressure. In keeping with the suggested requirements the relief valve !6 is of a Capacity to discharge up to one-fifth of the normal flow in case of leakage into the main valve body. This relief valve !6 is acted upon by opposed pressures of the inlet and outlet sides of the main valve. Referring par ticularly to Figure 4, while it seems from the figure that the diaphragms 6!) and 65 are the same size, there is a very slight difference and the diaphragm '55 hasa slightly greater area. Hence, since the outlet pressure is exerted upon a larger area than is the inlet pressure, the relief valve IG will be opened to the atmosphere whenever the two opposing pressures are equal in head or in pounds per square inch. The dierence in area is very slight, for example, in the 4" size the diaphragm 60 which is subjected to the inlet pressure, would be 4" in diameter and the outlet diaphragm 65, subjected to the outlet pressure, Would normally be l in diameter.

The body o has an arched cover ll and may carry a plug !8 having an inserted rubber bumper :9 acting as a stop for the valve !5 when fully open. The cored passage 20 in the body forms the middle portion of the central zone. The central zone extends from the inner seat 25 to the outer seat 26 and includes a waste pipe controlled by the valve e governed by the pressures in the inlet zone. The inlet zone is up to the inner seat 25 and the outlet zone includes the piping beyond outer seat 26 including the chamber 21 of body n and the outlet l2. Detachably secured to the body I a, as by bolts 21, is a bronze casting 22 having an annular recess 23 forming the inlet section of the central zone bounded by an inner seat 25 and an outer seat 26 preferably lying in a single plane, although the outer seat may extend further into the chamber 21 of the main valve body !5, it being important that the outer seat 26 be closed before the inner seat 25 and opened later so that the central zone is first closed to the outlet water and then closed to the inlet water and that the central zone be opened to the inlet water before being put in communication with the outlet water which may be non-potable, as when the consumer has an emergency tank filled from a nearby stream.

While the bracket 29 might extend from the body, it is more convenient to form this as an extension of the casting 22 so that the entire assembly may be removed as a unit when the top cover H is off. The hinge 30 is in the form of a yoke and having widely spaced arms 3| loosely receiving a mounting pin 32 carrying a weight' 33 to maintain a pressure drop in excess of two pounds to insure that the differential relief valve shall stay closed when either or both of the seats are uncovered, that is, that the relief valve be closed at all times when there is a flow in the normal direction thru the main valve. The extra weight mounting pin 32 may be kept in place in any conventional manner.

The valve closure [5 may be of any convenient type and is shown in Fig. 1 as compose of a s 4 36 held by two clamp plates 31 and 38 in engagement with a rubber facing 40 engaging both of the

annular seats

25 and 26, and a flexible member 4! which might be of laminated metal, but is preferably of a sheet membrane. The facing 48 is secured to the ring 44 as by the clamp ring 45 and the membrane 4! is similarly secured to the ring 44 by the clamp ring 46. Since both AD and 41 are flexible, the ring 44, which is thicker axially than the disk, has a slight movement axially of the common axis of the disk, ring, and closure. The ring and the disk have engaging

shoulders

48 and 49 to limit the outward movement of the disk when the closure starts to open and one or the other of these closure members carries a small annular rubber seal 50 te prevent foreign particles getting into the space between the

shoulders

48 and 49 to lessen the relative movement of the disk and ring. The axial pin 5! is threaded at both ends, as shown, but might be integral with either the clamp plate 31 or the nut 52 which engages the Washer 53 holding in place the yoke of the hinge 30 and the sleeve 54.

Considering now the differential relief valve !6, the body is of standard Construction having a pair of

valves

56 and 51 on a common stern 58 which, however, extends thru flexible sheet membranes 53 on opposite sides of the body and is secured at one end? to a diaphragm 60 acted upon by the inlet pressure transmitted by pipe 61, leading from a connection 62 near the inlet flange. The other end of the valve stern 58 is secured to a diaphragm 65 acted upon by the outlet pressure transmitted by a pipe 65 leading from a connection 61 near the outlet fiange of the main valve body I 0. A pipe 10 much larger than pipes 6I and 56, leads from the cored passage 20 to the relief valve inlet 'H so that when the relief valves are open the central zone fluid may be discharged thru the relief valve outlet M, preferably thru a pipe 15 having thei-ein a flow responsive element 16 controlling a visual indicator 11 for a slight flow and an audible indicator 18 for a larger flow so as to notify the attendant of abnormal conditions.

It is advisable to have the relief valve outlet '14 at a level well above the main line so that the central zone is always filled with water, if that be the fluid passing the main valve. By this the? draining of the central zone every time there is no flow is avoided and also the relief valve is protected from sand and sediment sifting into it as would occur with the relief valve located beneath the main valve. It is advisable to coat the bodies of the valves with porcelain enamel to avoid corrosion and incrustation.

As a Construction refinement to increase the ease of inspection and repairs, the seat and central zone casting 22, together with the disk and ring assembly !5, can be removed from the valve body thru its open top. This can be done by removing the valve body cover i? and the outside cap screws 2l that hold the seat and central zone casting. A new gasket 24 of suitable sheet material between the casting and the valve body will seal the joint against leakage when the seat casting is secured in place With the holding cap screws. To facilitate the removal of the disk assembly !5 without removing the seat casting 22, the hinge pin can be withdrawn thru the hole 8! opposite the pin. The disk assembly can then be lifted free of the valve body for inspection or replacement.

In Fig. 10 there are two spring pressed

valves

84 and 85 having a common stem 83 and, there-'- fore. actingas a unit. The rehe! valve.- Ii& as before: is; governed' by' opposing inlet and outlet pressure& thru: pipes: BB" and 81 communicating with the inlet; chamber- 88: and the-outlet: chamber 83,. respectivelyg. The central zone 90: in. this type is: cylindrical and vents. thru the. relief: valve ta by the. waste. pipe m.

The closure is` much more' efiioient than if the rubbe: facingi 40 were backed: by' a: solid member, as the latter would require too great a drop ina outletpressure before the' valve could open. Assuming a 4 size, seats of 4% and 6% diameter; and an inlet. pressure ot 60 pounds, it` would: necessitate the momentary fall of the outlet pressureto 20. pounds before the flow could start from statio pressure. 'I-lhis naturallywould prevent the use of faucets lo'- cated higher than 46 feet above the main line. But by making: the closure in two pieces with the disk 4 inches in diameter; it would necessitate the momentary fall of outlet pressure to- 4 1 7 pounds to rai'se the disk off its seat. When the outerseat only is closed and' the: outlet pres'- sure is i'l pounds, the force holding the ring to its seat is only about 200 pounds and the force holding the disk ofi' its seat is about 196 paund& The resultant force then, that isholding the ring to its seat is a force; of but 3 pounds. A further drop in pressure of a few ounceswill force the ring from its seat and flow will' start and these few ounces will continue to hold the close assembly justfree of the seats.

We will now consider the operation of the back flow preventer; starting with the position shown in, Fig. 'T which illustrates the mechanism as it Would' appear just after the demand for water had ceased in the house, factory or other consumer's property. With the cessation of flow, the pressure in the body ID* starts to. built up. The closure !5, aid'ed' by extra weight 33', tends to turn about its pivot 80' on bracket 29' and close flow of water from the body w across the central zone. The seat 26 is closed prior to the closing of the seat of the inlet' pipe, hence the inlet is stillopento t-hecentral zone. The chamber 20 and valve s are filled, but the relief valve is not yet wasting as the pressure in the body n has not quite risen to the point where the greater exposed area of the membrane 65 is able to overcome the lesser area of membrane 60 where the pressure is substantially the inlet pressure, as the flow is so slight. Almost immediately after the first closing of the valve |5 the body pressure reaches the necessary point to overcome the somewhat higher pressure at the left of the valve Hi so the

relief valves

56 and 51 open, as shown in Fig. 7, and this is followed by the complete closure of the val-ve !5, both of the concentrc seats being now engaged by their respective facings, so that no water flows from the inlet or from the outlet. The central zone is then open to atmospheric pressure, as it always is when there is no flow thru the system. This incidentally takes care of any possible leakage from the body and insures that such leakage cannot pass to the main.

Although the relief valve 16 is open to atmosphere during all periods of no flow, it closes promptly when a faucet is opened in the consumer's premises, and remains closed during all of the flow. The demand causes a slight drop in pressure in the body ID. This is immediately refiected at chamber 65, so that pressure on the opposite side closes the relief valve. At the same time the pressure of the Water on the inlet side arthe clos..u i-eli:` opensrthiedisk ssemblrin part. water now flowing' from; the.. inletto the; central zone build ng un. pressure therein. as the water cannoteape as long asgthe valve t&- is closed. The portion othegdi-sk assembly l-inri n irom the: first or: seatmores to its: back, position. and in: thepreierredconstruction. contact& fimly withtheshoulder. ot the, cute:: ring of: closure !5, This closure now opens: to flow fromvinl t to duhet; The extra; weight; &3; is so located to came ia. higherrpressure. differentiali at: the; &nale atao/nich the closurehangssfrom its pivot; 8.& when the'.- nate of flow: of: the water is: low; Il'he :lehet valve consequently eld: c osed until ter' h demand; to waterithe consumers .premisemas ceamdiasjtstecplaned.,

tsapparent from theabovethat no, back flow can occur normatmas a greater outl t pres ur would' merely hold. the closne all` the. tighter against i s two-seats and: hold the, relief'valve. in wideiopen position. binden ertraordinaryz condi tions' nem tor exannleas. would. occur ita; for eign, body were. caught between; the closure and the; seats, the relief; val ve would open. wide.. and its chamber would' continuously waste thru pipe 15,; This, howevem would be ndicated, first by the lamp; H' and; then; by' the bell ta; bringing p omnt attention..

Ina the: modified forms shown. in figures& and 9 are shown slight; modifications of the facing material; and the dexible -nemlarane Ihe form of Figo e is; somewhat preferred over that of F 8; and; shows, the body: seats. 25 and' 25; touchi-n inserted' facings Me; of semizhard rubher com: position facing material. In Eig; 8: the; facing material; ao is bronzeand; in this figure: the flexible material ist of the metallio. type as shown at 42th This inconveniently silver sol'dered as; at &2: at: the end of' the bend; so as to provide the necessary movement..

Lolaim::

1.. !k guidcd, closure. plate. for a back flow pre: Mentor.. consisting: of a di k. a ring: cnaxal: with the disk.: and hatme: a should r d eng cment iherewith; a racin formen of; a. sin le piece engaging both the disk and the ring, a flexible sheet carrying the ring and engaging the disk on the side opposite the facing, clamping means for securing together the facing, disk, ring, and sheet, and means for guiding the closure plate.

2. In a back flow preventer, a body having a plurality of concentric ports, means carried by the body for closing the ports in sequence including a single closure, and means tending t hold the closure in port-closing position with constantly lessenng force as the closure opens under urge of the inlet pressure at the central port.

3; A back flow prevention valve for insertion between a potable Water intake and a discharge pipe which might be connected to non-potable water, comprising avvalve body or casing having a major chamber and a communicatng passage forming part of a central zone, a removable multiple valve seat and closure detachably secured within the body having concentric seats so that the inner seat is the sole port admitting intake water and the space between the two seats is the sole communication between the major chamber and said part of the central zone, said body having an opening of such size as to receive the removable valve seat and closure for withdrawal, a cover for said opening, said closure being hinged and including a ring to engage the outer seat, a disk to engag the inner seat and flexible means connecting the ring and the disk so they Will normallymove together but the disk will have lost motion so as to move with respect to the ring when the inlet pressure exceeds the pressure in the central zone, said body having an inlet member communicating with the intake and having an opening therein for transfer of pressure and also having an outlet member leading from the major chamber and having an opening therein for transfer of pressure.

4. In a valve comprising a body having a pair of concentric, adjacent ports, a closure unit mounted adjacent said ports and movable toward said ports for closing one of said ports and subsequently closing the other port, said closure unit eomprising a portion of relatively large area exposed to pressure within the body for closing the first mentioned port, a portion of smaller area for closing the second mentioned port, said last mentioned area being protected from pressure within the body by the closing of the one port, said one port being the outer of the two concentrio ports, and flexible means joining the portions whereby pressure within the body greater than the pressure in the other or inner port exerted on the closure unit to move it toward the ports will cause the portion of larger area to move into port closing position in advance of the portion of smaller area, as the portion of smaller area is moved away from port closing position by the pressure in the body of the valve.

5. The device of claim 4 in which th closure unit comprises a disk of relatively large area on the seat side and a ring of relatively smaller area on the seat side surrounding the disk and movable relative thereto.

6. In a back flow preventer a valve body having an inlet, an outlet, a chamber communicating with the inlet and the outlet and a waste discharge passage communicating with the chamber in spaced concentric relaton to the inlet, an inner seat within the chamber surroundin the inlet, a disk within the chamber and movable into engagement with the inner seat to interrupt communication between the chamber and the inlet when the pressure within the chamber exceeds the pressure' within the in1et,' an outer seat within the chamber surrounding the waste discharge passage in spaced concentric relation to the inner seat, a ring surrounding the disk and movable therewth for engaging the outer seat and interrupting the passage of fluid from the chamber into the waste passage, and means carried by the disk and connected to the ring for supporting said ring for movement relative to the disk 7. The device of claim 6 in which the disk and ring contacting faces of the inner and outer seats lie in the same plane, and the disk and ring are pivoted to move as a unit progressively and sequentially into closing relation with the inner and outer seats respectively when fluid pressure in the chamber equals or exceeds the pressure of fiuid in the inlet.

8. The device of claim 6 in which the area of the disk exceeds the area of the ring whereby when the inlet and waste discharge passage are closed th pressure of the disk against its seat exceeds the pressure of the ring against its seat.

THOMAS A. GLASS.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 968,'794 Peare Aug. 30, 1910 1,044,623 Bailey Nov. 19, 1912 1,1G5,991 Miller Aug. 4, 1914 1,198,128 Hills Sept. 12, 1916 1,648,486 Larsen Nov. 8, 1927 1,668,456 Jennings May 1, 1928 1,693,842 Grimes Dec. 4, 1928 1,765,422 Grimth June 24, 1930 2,068,833 White et al Jan. 26, 1937 2,162,779 Lentwiler June 20, 1939 2,303,808 Wolcott Dec. 1, 1942 FOREIGN PATENTS Number Country Date ?47,081 France V Mar. 21, 1933