CA2218772A1 - Water hammer driven vibrator - Google Patents

Abstract

The invention provide apparatus for shaking structures such as fins in a fluid agitator, shaking screens, walls of bins or hoppers, conveyors, shaking tables, containers and tanks.
The apparatus is driven by a hydraulic driving system in which high pressure pulses are generated by repeatedly creating water hammer within a working conduit. This conduit is formed into a loop or a coil and is attached to the member to be vibrated. The working conduit is attached to the driving hydraulic system by flexible connections. This arrangement allows the water hammer to shake vibrated structures directly. Waterhammer generated forces act along the axis of the conduit. By each change of direction of the working conduit water hammer generated force is also changed to correspond with the axis of the working conduit. When working conduit is formed into a coil we can increase number of times that the water hammer generated will act on the workingconduit per one closure of the repeatedly interupting valve.

Description

~ CA 02218772 1997-12-22 , WATER HAMMER DRIVEN VIBRATOR
FIELD OF THE INVENTION
This application relates to devices used for shaking industrial devices or structures. The structure may be the wall of a hopper bin, a screen for separating finer particles from coarser particles, a fin for agitating or stirring a liquid, vibrating cont~inPrs, shaker tables or the like.

BACKGROUND OF THE ~VENTION
Vibrators are used in many industrial applications where it is nPcess~ry to shake a structure or device with high ~mplihl~le vibrations. For example, vibrators are used to:
shake screens for separating particles, such as crushed rock, by size; to vibrate bins and hoppers to prevent gr~n~ r particles from "bridging" and to help granular particles flow;
and to vibrate pieces of machinery, such as steam rollers. Various types of vibrators are currently available. All of these vibrators have disadvantages.

Many prior art vibrators cause vibration by turning an unbalanced rotor with an electric or hydraulic motor or by compressed air. These vibrators tend to be expensive because they require precision heavy duty bearings and/or are inefficient at converting input energy into vibration energy. Another characteristic of the prior art vibrators is that amplitude versus time generated force is following sinusoidal curve.

Water h~mmPr is a phenomenon by which high intensity pressure pulses are produced in a confined body of flowing fluid when the flow of the fluid is suddenly blocked. Water hammer is generally undesirable, and can be destructive. Much effort is spent in the design of hydraulic circuits to avoid water hammer. The mathematics of water h~mmPr are discussed in various texts on fluid mechanics including Fluid Mechanics (7th Edi~ion) Victor L. Streeter and E. Benjamin Wylie, McGraw-Hill Book Company, 1979 and R.L. Daugherty and J. B. Franzini, Fluid Mechanics With Engineering Applications, pages 425-431 McGraw-Hill Book Company, 1977.

Water hzlmmPr has been used to generate acoustic pulses for use in marine seismic exploration. For example, Baker et al., US Pat. No. 3,376,949, Anstey, U.S. Pat. No.

~ CA 02218772 1997-12-22 ~ , .
3,536,157, Burg U.S. Pat. No. 4,271,926, Bricout, U.S. Pat. No. 3,36g,519 and Davis, U.S. Pat. No. 3,690,403 disclose underwater acoustic generators, also for use inunderwater seismic exploration. Each of these devices use a deliberately created water hzlm me.r to produce a one shot high amplitude burst of acoustic signals appropriate for geophysical seismic exploration. Akimoff, German Patent No. 620,483 discloses a siren for broadcasting noise into air wherein the noise is generated by series of water hammers in a pipe.

Bayhi, U.S. Pat. No. 4,396,088 discloses a generator of low power, low frequencyacoustic waves for seismic exploration. The Byhi apparatus modulates the flow of fluid flowing into an array of flexible sleeves at the frequency of the desired sound. Bayhi does not disclose the use of water h~m m~r and is not designed for or adapted to shake industrial machinery or structures.

Walter, U.S. Pat. No. 5,467,322 discloses a system for shaking structures such as fins in a fluid agitator, sh~king screens, tables, bins of hoppers or the like. Disclosed apparatus transfers repeatedly generated water hammer pressure pulse to the vibrated structure via expanding rubber conduit or through an actuator.

Walter, U.S. Pat. No. 5,626,016 shows vibrating of members by transferring waterhammer generated pulses into a deformable element which is attached to the vibrated member.

SUMMARY OF THE INVENTION

This invention provides a vibrator suitable for use in industrial settings which uses water h~m mer pressure pulses to shake a member.

The vibrator comprises a hydraulic circuit where the working conduit is connected to the hydraulic driving system by flexible conduits or by conduits allowing free movement of the working conduit.

Working conduit can be formed as a single loop or it can be formed into a coil.
This working conduit is directly attached to the member that is to be vibrated. Each closure of the interrupting valve provides multiple vibrating forces acting on the working conduit.

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BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described with reference to the accompanying drawings which illustrate specific embo-lim~,nt.c of the invention, but which should not be construed as restricting the spirit or scope of the invention in any way:

FIG, 1 is a partially cut-away schematic view of a system according to the invention for ~git~ting fluid, FIG . 2 is a graph showing water hammer generated forces acting on the working conduit in time, FIG, 3 is a schematic view of a working conduit formed in a coil for ~git~3ting fluids.

FIG, 4 is a graph showing water h~mme,r generated forces acting on the working conduit that is formed in a coil in time.

FIG, 5 is a partially cut-away schematic view of a system according to the invention for agitating fluid. Shape of the working conduit allows for axial agitation in this arrangement, FIG. 6 is a partially cut-away schematic view through a hopper with the working conduit formed into a coil that is attached to the hoppers wall, DETAILED DESCRIPTION OF THE PREFERRED EM~ODIMENT

FIG. 1 Shows a liquid agitation device 10 which incorporates apparatus according to the invention for shaking fluid agitation fins 11 to agitate and stir fluid 12.
Agitation device 10 comprises a hydraulic driving system 14 which drives agitation device 10. Agitation device 10 may include a tank 15 containing a fluid 12 which may for example be a cleaning fluid or tar sands slurry, Liquid agitation device 10 further includes working conduit 16 on which are fastened or welded fins 11. Working conduit 16 is attached to the hydraulic driving ' CA 02218772 1997-12-22 .
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system by flexible conduits 17 and 18. This connection can also be secured by designing pivotal rigid conduits that would allow free movement of the working conduit.
Working conduit 16 is suspended by movable supporting means 19. This supporting means 19 can be in a form of a steel cable, chain or springs, or in any configuration that would allow for the free movement of the working conduit 16.
Hydraulic driving system 14 produces a series of high pressure pulses by deliberately creating a series of water hammers in the hydraulic circuit 20.
Hydraulic circuit 20 comprises of a tank 21, conduit 24, fluid 25, hydraulic pump 22 which can be replaced by any other means of delivering pressurized fluid, driving motor 23, conduit 26, conduit 18, working conduit 16, conduit 17, conduit 27, valve 28, valve actuator 29 and conduit 30.
Hydraulic pump 22 is driven by preferably electric motor 23. The output pressureof the pump is typically in the range of 30 - 300 psi, although it is possible to practice invention outside of this range. Exiting pump 22 fluid 25 flows trough conduit 26 to enter flexible pressure conduit 18. This conduit and conduit 17 can be designed in many dirr~ l ways, however preferred way would be to use a flexible rubber pressure hose that is currently being used in high pressure hydraulic systems.
Fluid 25 flows through the working conduit 16, through conduit 17 into conduit 27, through the valve 28 through the conduit 30 into the tank 21.
Driving hydraulic system 14 can also comprise a system where pump 22 and motor 23 is replaced by supply of fluid flow from a reservoir under pressure or a tank sufficiently elevated above the working conduit 16 to provide pressure head required for adequate velocity V of the fluid 25.
In some instances conduits 24 and 30 can be connected through the wall of tank 15 and use fluid 12 as a working fluid. Valve 28 is provided between conduit 27 and conduit 30. When the valve 28 is open working fluid 25 will circulate through the entire hydraulic circuit 20 and through the valve 28 substantially unintell upl~d. When valve 28 is closed it substantially blocks the flow of working fluid through hydraulic circuit 20.
Valve 28 is operated by a suitable actuator 29 which is capable of suddenly moving valve 28 from its open state to its closed state. Valve 28 must be of a type which can be opened and closed at the desired frequency of operation of the hydraulic driving system 14. For example, valve 28 may be a solenoid activated spool or needle valve, a self actuating-valve operated by the flow of working fluid 25 or a cam operated valve as described on FIG. 15, FIG. 16 and FIG. 17 in my U.S. Patent No. 5,459,699 issued October 17, 1995.

, Another arrangement for the valve operation is shown in FIG. 8 of my U.S.
Patent 5,549,252 issued Aug. 27, 1996. In this arrangement the valve is being closed by the effect of the flow of the working fluid and the valve is opened by the generated water hammer pressure.
Hydraulic driving system 14 functions as follows. With valve 28 open, pump 22 pumps working fluid 25 at a high velocity V through hydraulic circuit 20. Valve 28 is than suddenly closed by actuator 29. The sudden closure of valve 28 causes a water hammer within hydraulic circuit 20. In general, valve 28 need not completely block the flow of working fluid 25 in hydraulic circuit 20 to create a water hammer but a more intense water hammer is created if valve 28 is closed completely and suddenly. The water hammer results in a high pressure pulse prop~g~ting upstream through the conduit 27, flexible conduit 17, through the working conduit 16, through the flexible conduit 18, through the conduit 26, pump 22, conduit 24 and into the tank 21.
In a typical application the pressure of the water h~mm~r pulse is in the range of 500 psi to 2000 psi. The pressure of the water hammer pressure pulse is determined by the velocity V, the comprescihility of the working fluid 25, the speed at which valve 28 is closed, the degree of closure of valve 28 and the speed of sound in the working fluid 25, among the other factors. Under ideal circumstances, when valve 28 closes fully, the magnitude of the water hammer pressure is given by:
Ph=Q Cp V

Where Ph is the pressure of the water hammer pulse, Q is the specific density ofthe working fluid 25, and Cp is the velocity at which the water hammer pulse travels in hydraulic circuit 20. By increasing the velocity V of working fluid 25 in hydraulic circuit 20, making the walls of conduit 27 and conduit 16 rigid, and closing the valve 28 completely and very quickly the pressure of the water hammer pulses generated byhydraulic driving system 14 may be m~imi7~d Actuator 29 continuously opens valve 28, retains valve 28 open for a time sufficient for working fluid 25 to attain a significant velocity through valve 28 and suddenly closes valve 28 to create a continuous series of water hammer pressure pulses within hydraulic circuit 20.
When valve 28 closes suddenly, fluid 25 which flows at velocity V is suddenly stooped. Kinetic energy of the flowing fluid 25 is suddenly converted into a pressure.
This raise in pressure - water hammer pulse travels upstream through the conduit 27 and into a conduit 17 at the speed of sound in the particular conduit. Stiffness of the conduit wall is determining factor in the velocity Cp of sound in the fluid 25. When raise in pressure enters working conduit in the location marked 31 the water h~m m~r pressure acting on the projected area marked Al creates a force Fl acting in the direction of Fl.
This force Fl will accelerate working conduit with fins 11 in the direction of Fl. This acceleration will stir and agitate fluid 12. Time during which force Fl will aet on the working conduit 16 is obtained by dividing length Ll/Cp. When raise in pressure due to water hammer reaehes position marked 32 foree Fl will stop to aet on the workingeonduit 16.
When water hammer pulse passes position marked 32 a new foree F2 aeting in the direetion of F2 will act on the working conduit 16 and fins 11. Force F2 will aecelerate working conduit 16 and fins 11 in the direetion of F2 eausing effeetive agitation of the fluid 12. Time during whieh foree F2 will aet on the working eonduit 16 ean be obtained by dividing length L2/Cp.
After passing loeation 33 pressure pulse eontinues upstream through eonduit 18, eonduit 26, pump 22 and eonduit 24 into the tank 21. To reduee effect of the water h~m mer pressure pulse on the pump 22 we can place a pulsation dampener in front of the pump 22 ( not shown).
Movement of the working eonduit 16 and fins 11 is allowed by suspending working eonduit 16 by ehains or eables 19 and by eonneeting the working eonduit 16 to the hydraulie driving system 14 by flexible eonduits 17 and 18. Flexible eonduits 17 and 18 ean be substituted by a pivotal arranged rigid eonduits, however a flexible eonduit sueh as a hydraulie pressure rubber reinforeed hose would be most practical for water h~m m~r pressure in the range of 500 to 2000 psi.

FIG. 2 shows a graph describing action of the forces Fl and F2 acting in time onthe working conduit 16.

FIG. 3 shows a working conduit 33 on which are attached fins 11. This working conduit is formed in a coil. In this particular case eoil consist of two turns.
Working conduit 33 is suspended by cables 19 and is connected to conduits 26 and 27 by flexible pressure conduits 17 and 18. When hydraulic driving system 14produces water hammer pressure pulse, this pulse travels upstream from the valve 28 and enters the working conduit 33 at the position marked 34. For the duration of time Ll/Cp resulting force Fl acts on the working conduit 33 and fins 11 in the direction Fl . After water hammer pulse passes location marked 35 a force Fl stops and Force F2 starts acting in the direction of F2 for the time duration L3/Cp. Working conduit 33 and fins 11 are accelerated in the direction F2 and effectively stirring and agitating fluid 12. After .
water h~m m~r pulse passes location marked 36 Force F2 stops and force Fl starts acting on the working conduit in the direction of Fl for the duration of time L3/Cp. Working conduit 33 is now accelerated in the direction of Fl and it is stirring the fluid 12. After water hammer pulse passes location marked 35 force Fl stops and force F2 acts in the direction of F2 for the time L2/Cp. Working conduit 33 and fins 11 are accelerated in the direction F2 and are actively stirring and agitating fluid 12. By creating a coil of more turns we would create additional forces that would accelerate working conduit and fins at higher frequency than is the frequency of the hydraulic driving system 14. Therefore the frequency of the hydraulic driving system 14 is multiplied by a single loop by two For each additional turn of the coil we will multiply the frequency of the hydraulic driving system 14 by two.

FIG 4 shows a graph describing action of the water hammer generated forces Fl and F2 acting in time on the working conduit 33.

FIG. 5 shows a liquid agitation device 10 that was shown on FIG. 1 with the exception that working conduit 16 shown on FIG. 1 is replaced by working conduit 37.
Suspending cables 19 shown on FIG. 1 are replaced by springs 38.
Movement of the working conduit 37 is caused by water hammer generated forces that are generated as described in FIG. 1 and FIG. 3 and these forces act in the direction Fl, F2, and F3. It follows that a great versatility of arrangement is possible.

FIG. 6 shows hydraulic driving system 14, vibrator 41 and hopper 42. Hydraulic driving system 14 is connected to the working conduit 43 by flexible pressure hoses 17 and 18. Working conduit 43 is connected to the wall 40 of the hopper 42 by a bracket 39.
When valve 28 is suddenly closed water hammer pressure pulse travels upstream inconduit 27, 17 and enters working conduit 43 at location marked 44. Water hammerpressure pulse acting on the inside projected area of the working conduit 43 creates force Fl that is acting in the direction Fl. When the water hammer pulse reaches the location marked 45 force Fl stops and force F2 acting in the direction F2 on the working conduit 43. The effect of the water hammer pulse on the working conduit 43 is the same as the effect of the water hammer generated forces acting on the working conduit 33 as shown in FIG. 3.
It is clear that we can vibrate numerous industrial members by a wide variety ofconfiguration of working conduit. The big advantage of this system is that we can increase the effective frequency of the vibrated member beyond the frequencies of the .
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hydraulic driving system 14. In some instances we could also fasten the hydraulic driving system to the vibrated member.

Working conduits 16, 33, 37 and 43 should be made from material that is strong and light for the best acceleration of the working conduit. High strength steel or carbon fiber filament wound composite material would allow for the lightest working conduit that would allow for maximum acceleration. High strength would also provide minimum expansion of the conduit wall and therefore allow for the maximum Cp in the fluid 25 which will produce maximum water hammer pressure pulse.

As is shown on all drawing it is preferable that the working conduit incorporates longer section of the straight portion which will provide sufficient length and therefore time during which the water hammer generated force will have time to accelerate working conduit to stir fluid more efficiently.

As will be apparent ~o the skilled in the art in light of the foregoing disclosure, many alterations and modifications are possible in the practice of this invention without departing from the spirit or scope thereof.

Claims

I claim:

1. A water hammer driven vibrator substantially as described herein with reference to the accompanying drawings.