US2754763A

US2754763A - Control system for suction dredge relief valve

Info

Publication number: US2754763A
Application number: US342257A
Authority: US
Inventors: David L Hofer
Original assignee: Individual
Current assignee: Individual
Priority date: 1953-03-13
Filing date: 1953-03-13
Publication date: 1956-07-17
Anticipated expiration: 1973-07-17

Description

D. L. HOFER July 17, 1956 CONTROL SYSTEM FOR SUCTION DREDGE RELIEF VALVE Filed March 13, 1953 United States Patent CONTROL SYSTEM FOR SUCTION DREDGE RELIEF VALVE David L. Hofer, Berkeley, Calif.

Application March 13, 1953, Serial No. 342,257

1 Claim. (Cl. 10311) The present invention is directed to, and it is a major object to provide, a novel control system for hydraulically opening the relief or water entry valve on the intake pipe of a suction dredge upon, and for the purpose of relieving, abnormal Working conditions prevailing in the pumping line of the dredge.

Upon the occurrence of abnormal Working conditions, such as a slug or plug occurring at the outer end of the intake pipe or gassy material being encountered thereby,'or the discharge pipe loading up, it is requisite that the relief valve on the intake pipe be opened so that water in substantial quantity may freely enter the pumping line to relieve such abnormal working conditions and prevent damage which might otherwise occur.

I have ascertained that when such abnormal working conditions exist in the umping line, the electrical load on the energizing circuit for the electric motor which drives the dredge pump, is materially reduced.

' It is therefore another important object of the invention to provide a control system, for the relief valve, which automatically responds to such a drop in the electrical load and opens said relief valve.

It is also an object of the present invention to provide a control system, for the purpose described, which is designed for ease and economy of initial installation, and positive and effective operation without manual attendance by the operator.

Still another object of the invention is to provide a practical and reliable control system for a suction dredge relief valve, and one which will be exceedingly effective for the purpose for which it is designed.

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 claim.

The figure of the drawing is a diagrammatic illustration of the novel control system.

Referring now more particularly to the characters of reference on the drawings, the control system is adapted to be embodied in a suction dredge which includes a dredge boat 1 which supports a pump 2 driven from an electric motor 3 by an endless drive unit 4; the electric motor 3 being energized from a circuit, indicated at 5.

An intake pipe 6 leads from an under-water point to the pump 2, and the latter includes a discharge pipe 7 which is adapted to couple to the pipe line which leads to the waste area.

Adjacent but above the outer end 8 of the intake pipe 6, the latter is fitted with a normally closed butterfly type relief valve 9; opening of such relief valve permitting water in substantial quantity to rush freely into the intake pipe 6 for the purpose of relieving the aforementioned abnormal working conditions.

The relief valve 9 includes a radial arm 10 pivotally connected, at its outer end, to a longitudinal rod 11 which extends upwardly above and parallel to the intake pipe 6.

At its upper end the connecting rod 11 is attached to the lower end of the piston rod 12 of a fluid pressure actuated power cylinder 13 mounted lengthwise in connection with said intake pipe 7, preferably at an abovewater point and in position such that the

rods

11 and 12 are in alinement.

A piston 14 is disposed in the power cylinder 13 intermediate the ends of the same and in connection with the piston rod 12; there being a loaded compression spring 15 surrounding said piston rod 12 between the piston 14 and the lower end of the power cylinder 13. The spring 15 urges the piston 14 in a retracting direction, which is the direction of movement to open the relief valve.

At its upper end the power cylinder 13 is in communication with a two-position valve 16; such valve when in one position, as shown in the drawings, establishing communication between an air pressure supply 17, and when in another position (not shown) blocking off the conduit 17 and establishing communication between the power cylinder 13 and a vent port 18.

When the valve 16 is in the position shown, and at which time the conduit 17 is in communication with the power cylinder 13, the resultant air pressure in said cylinder works against the piston 14, maintaining it advanced against the spring 15 and holding the relief valve 9 closed. However, when the valve 16 is actuated to a position blocking. conduit 17, the power cylinder 13 vents through port 18, whereupon the spring 15 acts to retract the piston 14 and open the relief valve 9.

The novel control system, which embodies the essence of the present invention, comprises the following:

The valve 16 is normally maintained in the position establishing communication between conduit 17 and power cylinder 13, by means of an energized solenoid 19; such solenoid being energized by a circuit 20 drawing from a suitable source of current.

A normally closed adjustable electro-responsive circuit breaking unit 21, such as a wattmeter or other loadresponsive instrument which can be purchased on the open market, includes normally closed contacts 22 forming a switch interposed in the circuit 20. The opening of the contacts 22 is controlled by the functioning of the instrument 21 upon a reduction of the load on the motor as indicated by the wattmeter.

A transformer 23 is connected into the energizing circuit 5 ahead of the electric motor 3, and a feed circuit 24 leads from the transformer 23 to the input terminals of the electro-responsive circuit breaking unit 21. The working or actuating mechanism of said circuit breaker is energized by another circuit 25 which leads from the circuit 5; there being a voltage reducing transformer 26 in the circuit 25.

The above described control system functions as follows:

When the pumping line of the dredge, including the pump 2, is under normal working conditions, the electrical load on the circuit 5 is relatively heavy; the contacts 22 then being adjusted so as to remain closed.

In turn this causes the solenoid 19 to stand energized, holding the valve 16 in the position which loads the power cylinder 13, maintaining the relief valve 9 normally closed.

However, upon an abnormal working condition occurring in the pumping line of the dredge, the load on the electric motor 3, and consequently the electrical load on the circuit 5, substantially reduces. When this oc curs lesser current is fed by circuit 24 to the circuit breaker unit 21, resulting in the contacts 22 being opened.

This breaks the circuit 20, and solenoid 19 is deenergized, moving the valve 16 to its power cylinder venting position. As soon as the power cylinder 13 vents, the spring 15 retracts the piston 14 and the relief valve 9 is opened, whereupon water rushes freely into the pumping line to relieve the abnormal working condition.

With the described control system, the relief valve on a suction dredge is automatically opened whenever the necessity arises, and automatically closed when the abnormal working condition is alleviated.

At certain times the operator might desire to open the relief valve 9 independently of the automatic control, and this is accomplished by the use of a manual or foot switch 27 interposed in the circuit 20 in series with the circuit breaker 21; the switch 27 normally being closed.

With a control system as described the suction dredge works with increased efiiciency, safety, and yardage, yet with a nominal initial cost of the system, and practically no maintenance thereafter required.

From the foregoing description it will be readily seen that there has been produced such a system as substantially 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 resorted to as do not form a departure from the spirit of the invention, as defined by the appended claim.

Having thus described the invention, the following is claimed as new and useful, and upon which Letters Patent are desired.

In a suction dredge which includes a pipe line having a normally closed relief valve connected thereto intermediate its ends and arranged when open to admit water into the line, an electric motor driven pump in the pipe line, an energizing circuit for the electric motor, power mechanism adapted to open said relief valve, a fluid pressure control valve movable from one position to another position to then cause said power mechanism to open the relief valve, and an electric device to so move the valve; an automatic control system for said relief valve comprising a control circuit connected to the electric device of said control valve, a switch interposed in the control circuit and having open and closed positions, an electric-load responsive instrument, a feed circuit connecting the energizing circuit and said instrument, and means an the instrument and switch to cause the latter to move from one position to the other upon the ioad in the energizing circuit and reflected in the instrument, dropping below a predetermined normal to then place the control circuit in condition so that the electric device moves the fluid-pressure control valve from said one position to the other position.

References Cited in the file of this patent UNITED STATES PATENTS 1,562,561 Horter Nov. 24, 1925 1,773,963 Deutsch Aug. 26, 1930 1,783,036 Crawford Nov. 25, 1930 2,572,263 Hofer Oct. 23, 1951 2,644,400 Hofer July 7, 1953 2.687,693 Hudson Aug. 31, 1954