US 2889779 A
Abstract available in
Claims available in
Description (OCR text may contain errors)
June 9, 1959 D. l.. HoFl-:R
RELIEF VALVE SYSTEM Foa sucTIoN DREDGES Filed June 24, 19.57
INVENToR. D. [..Jofer Qm. m'N NN mm. Nm
'- 'cuius United States Patent O RELIEF VALVE SYSTEM FR SUCTION DREDGES l David Louis Hofer, Berkeley, Calif.
Application June 24, 1957, Serial No. 667,375
l 4 claims. (c1. 10s-11) This invention is directed to a novel control system for an underwater relief valve on the suction pipe of a hydraulic dredge; such valve being normally closed, but adapted to be opened to admit water into the suction pipe in order to relieve abnormal pumping conditions existing in either or both the suction and discharge pipes of the dredge. In order to prevent possible damage to the equipment, the relief valve is opened, for example, upon the occurrence of too low pressure in the discharge pipe, or excessive pressure in such discharge pipe accompanied by a fall in vacuum in the suction pipe.
To most electively attain the desired relief of such an abnormal pumping condition, the relief valve must be quick-opened to permit substantially instantaneous entry of a relatively large quantity of Water into the suction pipe above its intake end. However, when the pumping conditions return to normal, the relief valve has to be relatively slowly closed as otherwise the pump may be unduly overloaded and possibly damaged due to impact of the dredged material on such pump. It is, therefore, the purpose and main object of this invention to provide an automatic system to control the relief valve, and particularly to quick-open and slowly close such valve in response to abnormal pumping conditions and return to normal pumping conditions, respectively.
It is another important object of this invention to provide a relief valve system, for suction dredges, which is relatively simple in structure yet extremely effective in operation.
It is also an object of the invention to provide a practical and reliable relief valve system for suction dredges.
These objects are accomplished by means of such structure and relative arrangement of parts as will fully appear by a perusal of the following specification and claims.
In the drawings:
Fig. 1 is a diagrammatic elevation of the system under normal pumping conditions, and with the relief valve closed.
Fig. 2 is a similar but fragmentary view, showing the system under abnormal pumping conditions, and with the relief valve open.
Referring now more particularly to the drawings and to the characters of reference marked thereon, the relief valve system is adapted for use in connection with a hydraulic dredge, indicated generally at 1, which includes a suction pipe 2 whose intake end is indicated at 3.
At its upper and opposite end the suction pipe 2 delivers to a heavy duty motor driven pump 4 connected, in turn, to a discharge pipe 5.
Adjacent but short of the intake end 3 thereof, the suction pipe 2 is providedpwith a normally closed butterfly valve 6 which includes a radial operating lever or arm 7 disposed in an upstanding position. A control cable 8 is attached intermediate its ends to the radial arm 7, and such cable 8 extends longitudinally above the suction pipe 2 and inopposite directions from said radial arm 7.
vworking position of the At its forward end the cable 8 is connected to an up-v standing bracket 9 by an assembly which includesin end-to-end connectiona heavy duty tension spring 10 and a turnbuckle 11.
At its upper or opposite end, the cable 8 is connected by means, including a turnbuckle 12, to the outer end of the piston rod 13 of a longitudinally disposed air pressure` actuated power cylinder 14 which is attached, at the end opposite the piston rod 13, to an upstanding bracket 15.
When the power cylinder 14 is deenergized, its piston 16 is `advanced toward the intake end of pipe 2, as is the piston rod 13, as shown in Fig. 2.
A conduit 17 of substantial inside diameter or capacity is connected to the forward end of the power cylinder 14 and thence leads to a threeway rotary valve 18 suitably mounted on the dredge and adapted to be actuated by a solenoid 19 connected to said rotary valve by suitable linkage 20.
In one position of said valve 18, as in Fig. l, such valve establishes communication between the conduit 7 and a restricting air pressure feed pipe 21 which leads to said valve; such feed pipe 21 being connected to an air pressure supply pipe 22 having a normally open hand valve 23 interposed therein.
With the valve 18 in the position of Fig. l, air pressure is delivered from supply pipe 22 through restricted air pressure feed pipe 21, said valve 18 and conduit 17 causing energization of the power cylinder 14.
When the power cylinder 14 is energized, the piston 1 6 travels rearwardly therein, retracting the piston rod 13 and pulling the cable 8, against the tension of spring 10, to close the butterfly valve 6. This is the normal system, and at which time the solenoid 19 is energized and works against the tension of a pullback spring 24. The solenoid 19 is energized by a circuit which comprises leads 25 and 26 which extend from an electric current source, not shown.
Switches 27 and 28 are interposed in series in the lead26; said switches being of normally closed pressure actuated type, and are connected in common and by branched pipe 29 to the upper end of a standpipe 30 mounted and communicating with the discharge pipe 5; normally open manual valve 31 in said 29.
The standpipe 30, while being of lesser diameter than the discharge pipe 5, is considerably larger than pipe 29;
the purpose being to prevent the entry of material intoand the plugging of-said relatively small pipe 29.
The switch 27 is responsive to and opens under the inuence of low pressure in the discharge pipe 5, while the switch 28 is responsive to and opens under the influence of excessive pressure in said discharge pipe.
A vacuum responsive switch 32 is included in the f l"system and is connected in parallel to the switch 28 by a side circuit 33; such switch 32 being normally closed.
A separate standpipe 34 upstands from the suction pipe 2 adjacent the pump 4 and at its upper end such standpipe 34 is connected by a relatively small pipe 35 -to the switch 32; the latter being responsive to and opening upon occurrence of a low vacuum in the suction p1pe 2, and which low vacuum usually accompanies excessrve pressure in the discharge pipe 5. =A normally open manual valve 36 is provided in the pipe 35. A normally closed manual switch 37 is interposed in the lead 2,6 of the solenoid circuit. Y
Under normal pumping conditions, the switches 27, 28,
32 and 37 all remain closed; the solenoid 19 is ener-f gzed; and the valve 18 is in the position of Fig. l, main- .V-taining the butterfly valve 6 closed, as hereinbefore described.
In -the event.V that low pressure occurs in the discharge t p1pe 5, the switch 27 ,responds and opens which breaks the circuit to the solenoid 19, whereupon the pullback spring 24 functions to actuate the valve 18 from its position, as in Fig. l, to the position as in Fig. 2. In such latter position of the valve, it establishes full open communication between the conduit 17 and an nnrestrictive vent 38, whereupon the air pressure is Vinstantaneously released from the power cylinder 14 through said conduit 17, valve 18 and vent 38. When this occurs the piston 16, piston rod 13 and cable 8 snap forward under the intluence of the loaded tension spring 10, and which results in quick-opening of the buttery valve 6.
With such opening of the butterfly valve 6, a large quantity of water rushes into the suction pipe 2 for the purpose of relieving the abnormal pumping condition; i.e. in this instance low pressure in the discharge pipe 5 and which would be caused, for example, by a plug in the intake end 3 of suction pipe 2.
The buttery valve 6 remains open until such abnormal pumping condition is eliminated, and yat which time the switch 27 closes, resulting in energization of the solenoid 19 and the latter then returns the valve 18 to its initial position, as in Fig. l.
Upon such return of the valve 18 to its initial position, air pressure is fed-but relatively slowly-to the conduit 17 from the restricted air pressure feed -pipe 21; the latter being of quite small internal diameter. With such slow feed of air pressure through the conduit 17 to the power cylinder 14, the piston 16 retracts slowly, and which results in a corresponding slow closing of the buttery valve 6, and which closing requires at least eight to ten seconds.
The system functions in the same manner as above described upon occurrence of excessive pressure in the discharge pipe 5 accompanied by resultant and low vacuum in the suction pipe 2. When such excessive pressure occurs in discharge pipe 5, and low vacuum results in suction pipe 2, switches 23 and 32, respectively, both respond and open, breaking the circuit to the solenoid 19 whereupon the butterfly valve 6 is quick-opened in the manner previously described.
As the switches 2S and 32 are in parallel relation to each other in the solenoid circuit, both of said switches must open before the solenoid circuit is broken and the butterliy valve 6 opens.
As soon as the abnormal pumping conditionoccasioned by excessive pressure in the discharge pipe 5 and low vacuum in the suction pipe 2-is corrected, and upon closing of either of the switches 28 or 32, the solenoid 19 is `again energized which results in slow-closing of the buttery valve 6, as before described.
The relief valve system, in addition to automatically and effectively controlling the valve 6, has an important safety function. For example, if there is a failure of the electric current to the solenoid 19, or a failure of the air pressure supply to the valve 18, the system will open the buttery valve 6 until such failures are corrected.
Also, if at any time the operator desires to 4cause opening of the buttery valve 6, he can do so by opening the manual switch 37 which has the same eect as opening of the switch 27, or of the switches 28 and 32 in common.
The described relief valve system, for a hydraulic dredge, thus provides for the effective and automatic control of abnormal pumping conditions, and accomplishes the result by relatively simple but practical apparatus which may be readily and conveniently installed on an existing dredge.
From the foregoing description, it will be readily seen that there has been produced such a system as ,substan tially fulfills the objects of the invention, as set -forth herein.
While this specification sets forth in detail the present and preferred construction of the system, still in practice such deviations from such detail may be resortedto as do not form a departure from the spirit of the invention, as dened by the appended claims.
Having thus described the invention, the following is claimed as new and useful, and upon which Letters Patent is desired:
1. A relief valve system for a hydraulic dredge which includes a suction pipe, a driven pump, and a discharge pipe; comprising a normally closed underwater relief valve on the suction pipe, means to close the valve and hold the same closed when pumping conditions are normal, separate means to open the valve, and means responsive to an abnormal pumping condition to enable the second named means to unrestrictedly and rapidly open the valve and upon restoration of normal pumping conditions to then cause the rst named means to function in a manner to impart a relatively slow closing movement to the valve.
2. A relief valve system, as in claim l, in which said rst named means includes a fluid pressure power cylinder operatively connected to the relief valve and when energized closing said valve, and spring means connected to the valve to open the same upon deenergization of the power cylinder; said last named means including another valve, said other valve in one position causing said deenergization and in a second position allowing said relatively slow reenergization of the power cylinder, an electromechanical device adapted to operate the other valve, a control circuit for the electro-mechanical device, a pressure actuated switch in the circuit; said switch, in response to an abnormal pumping condition, being operative in the circuit Ato cause the electro-mechanical device to move the valve to said one position, and in response to a normal pumping condition to move the valve to said second position, an air pressure conduit connecting the valve and cylinder, an .exhaust port in the valve, and a uid pressure feed pipe leading to the valve and of materially restricted size relative to the pressure conduit and the exhaust port; the valve when in said one position connecting the pressure conduit and the exhaust port and Vwhen in the second position connecting the feed pipe and the pressure conduit.
V3. A relief valve system for a hydraulic dredge which includes a suction pipe, a driven pump, and a discharge pipe; comprising an underwater relief valve on the suction pipe, an energized tluid pressure power cylinder closing the relief valve whenpumping conditions are normal, a spring yieldably tending to open ythe relief valve, Vmeans responsive to an abnormal pumping condition in one of said pipes operative to deenergize the power cylinder, and means included in part with said irst named means and functioning in response to a return to normal pumping V conditions subsequent to an abnormal pumping condition to relatively slowly reenergize the power cylinder with afcorresponding resultant and relatively slow closing movement of the relief valve. Y
4, A system, as in claim 1, in which said first named means includes -a normallyrenergized fluid pressure power cylinder operatively connected to the relief valve to close the same, and spring means to open said valve upon Vdeenergizing of the power cylinder; said last named means including aconduit leading to and from one end of the cylinder, a discharge vent no smaller than the conduit, a pressure feed conduit relatively small as compared to the first namedconduit, and a valve interposed between the conduits and the vent; said valve when pumping conditions are abnormal establishing unrestricted communication between the irst conduit and the vent and when the pumping conditions are restored to normal, establishing communication between the pressure feed conduit and the first named conduit.
References Cited in the file of this patent UNITED STATES PATENTS 1,971,441 Broadhurst Aug. 28, 1934 2,250,021 Hofer July 22, 1941 2,572,263 Hofer Oct. 23, 1951 2,644,400 Hofer July 7, 1953 2,754,763 Hofer July 17, 1956