GB2182121A - Hydrodynamic couplings and control means therefor - Google Patents

Abstract

A control arrangement for a hydrodynamic coupling 11 includes passages whereby working fluid is enabled to gain access to the working chamber 19 of the coupling 11, and a scoop-tube adjusting mechanism 23 for controlling the extent of filling of the chamber 19 by changing the rate at which the working fluid is withdrawn from the chamber. A piston-and-cylinder actuator 29 is provided for controlling the adjusting mechanism 23 over a starting period during which the coupling 11 is gradually filled. A fluid pressure supply circuit 33 for the actuator 29 includes a source 36 of fluid under pressure and two conduits 41, 42 by way of which the fluid under pressure passes via common porting 49 into actuator 29. The conduit 41 includes a restrictor 43 and the conduit 42 includes a restrictor 46. The circuit 33 includes a valve 45 selectively operable to ensure that, for a first stage of movement of the actuator 29, and thus movement of mechanism 23 at a relatively slow rate, flow to actuator 29 takes place through conduit 41, and, for a second stage of movement of the actuator 29, and movement of mechanism 23 at a relatively fast rate, flow to actuator 29 takes place additionally through conduit 42. <IMAGE>

Description

SPECIFICATION Hydrodynamic couplings and control means therefor This invention relates to hydrodynamiccouplings and to control means therefor.

Hydrodynamic couplings and control means therefor have hitherto been proposed in which an adjusting mechanism, forcontrolling the extent offil- ling of the working space of the coupling by variation ofthe rate of discharge of the working fluid fromthe working space, has been operated by actuator means and, in orderto avoid excessive loading in the equip ment driven through the intermediary ofthe coupl ing, it has been arrangedtoensurethatthetorque transmitted bythe coupling tothe equipment has been maintained at the required level during starting-upofthedrive.In one proposal hitherto madethe working velocity ofthe actuator means has been increased in a step-wise manner to dividethestarting period into at least two sections. In this way the starting cycle has been controlled in such a way that the transmitted torque can be limited to a given value and maintained substantiallyconstantfora given time.

The actuator means in one embodiment has comprised an hydraulically-operable piston-and-cylinder device so hydraulically supplied asto operate in step-wise manner and connected to a scoop-tube which is in consequence caused to so control the fluid contents of the working chamber ofthe coupl ingastoeffectstarting oftheequipmentthroughthe intermediary ofthe coupling as it is progressively engaged in step-wise manner.To achieve such step wise operation the cylinder of the piston-and- cylinder device has been provided with a plurality of inlet ports spaced in the axial direction, whereby during the supply of working fluid to the cylinderthe ports are uncovered progressively by movement of the piston of the device, thereby increasing the velocity ofthe movement of the piston in steps, and to this end flow setting valves have been provided for controlling theflowoffluidto each port.

It is an object of this invention to provide an improved hydrodynamic coupling and control means therefor.

According to this invention a hydrodynamic coupling and control means therefor include means whereby working fluid is enabled to gain access to the working chamber of the coupling, an adjusting mechanism for controlling the extent offilling ofsaid working chamber by change in the rate at which the working fluid is withdrawn from said working chamber, an actuator means for controlling said adjusting mechanism over a starting period during which the coupling is gradually filled, said actuator means being of fluid-pressure-operable type, and a fluid pressuresupplycircuitforsaid actuator means, said circuit including a source offluid under pressure and two generally parallel conduitsbywayofwhich said fluid under pressure can pass through common porting into one end of said actuator means, thefirst conduit including a first flow control means permitting flowthrough that conduitat afirst pred etermined rate and the second conduit including a second flow control means permitting flowthrough that conduit at a second predetermined rate, and said circuit further including valve means selectively op erable to ensure that for a first stage of movement of said actuator means, and thus movement of said adjusting mechanism at a relatively slow rate, flow of fluid to said actuator means takes place through said first conduit, and for a second stage of movement of said actuator means, and thus movement of said adjusting mechanism at a relatively fast rate, flow of fluid to said actuator means takes place additionally through said second conduit.

Preferably, the said second stage of movement of said actuator means is caused to commence when the rotational speed of the output member of said coupling reaches a predetermined percentage of its designed maximum operating speed.

The valve means may include a valve disposed in said second conduit immediately upstream of said second flow control means.

The first and second flow control means may each comprise a flow restrictorwhich in suitable manner is adjustable as to its precise flow rate characteristics.

The adjusting mechanism may comprise a linearly moveable scoop-tube which is arranged to project into an annularcompartmentorsumpwhich isrotat- able with the input shaft of said coupling, said com- partment being in communication with said working chamberofthe coupling.

The actuator means may comprise a piston-andcylinder device, the piston of which is connected to said scoop-tube. In this case said common porting is provided in thewall ofthe cylinderofthe device and is open to one of the two chambers of said device separated by said piston.

Since each of said two flow control means is disposed in a respective one ofthetwo parallel conduits, one flow control means being used for slowspeed movement of the adjusting mechanism inthe first-stage of operation thereof and the other being brought into use for high-speed movement of the adjusting mechanism in the second-stage of operation thereof, the bringing ofthe output member of said coupling up to its designed maximum speed can be achieved relatively rapidly yet without any appreciable tendency of the output member to deliver undesirably high power peaks of short duration which might otherwise cause damage to the members, for example loaded conveyor belts, driven by the coupling.

One way of carrying out the invention is described in detail belowwith reference to drawings which illustrateonlyonespecificembodiment,inwhich: Figure 1 shows an hydrodynamic coupling and control meanstherefor, and Figure 2 is a graphical representation of alternative starting cycles ofthe coupling shown in Figure 1.

In the drawings a hydrodynamic coupling 11 suitable for use in the transmission of driving power from an electric motor (not shown) to a belt conveyor (also not shown) includes an input shaft 12, adapted to be connected to the motor, and an output shaft 13, adapted to be connected to the conveyor. The coupl- ing is housed in a casing 14 and has an impeller 15 formed integrally with a member 16 of the cross- sectional shape shown in Figure 1. Member 16 has a flanged connection at 17 with input shaft 12 and is thus rotatable within casing 14. The coupling also has a turbine 18, co-operable with impeller 15, which is drivingly mounted on output shaft 13.The working chamber 19 defined by impeller 15 and turbine 18 is oftoroidal shape, and the shape of member 16 is such asto provide an annular sump 20 which is rotatable as one with impeller 15. The casing 14is prov ided tothe level indicated with hydraulicfluid which is able to gain access to working chamber 19 in conventional mannerthrough suitable passage means.

A scoop-tube 23, which islinearlyslidableina fixed sleeve 24, is provided in casing 14, its lowered portion being disposed in the annular sump 20. At its upper end portion tube 23 is pivotally connected through the intermediary of link 25 to one arm 26 of a bell-crank lever 27 pivotally mounted at 28 on casing 14.

Hydraulically-operable actuator means in the form of a piston-and-cylinder unit 29 is provided adjacent casing 14, the piston rod 30 thereof being pivotaly connected at 31 to the other arm 32 of lever27. Unit 29 is included in a hydrauliccircuit33 powered bya pump 34 driven by an electric motor 35. Fluid drawn by the pump from reservoir 36 is delivered under pressure by the pump through filter37 to a solenoid- operated two-position valve 38, shown energised. A conduit 39 taken from valve 38 is provided with a relief valve 40, and upstream of that relief valve two parallel conduits 41,42 are branched from conduit 39.Conduit41 incorporates a first flow control means in the form of a firstflow restrictor43, the precise flow rate characteristics ofwhich are adjustable in known manner. A check valve 44 is provided in parallel with restrictor43. Conduit 42 incorporates a solenoid-operated two-position valve 45 and, downstream ofthatvalve, a second flow control means in the form of a second flow restrictor 46, the precise flow rate characteristics of which are adjustable in known manner.Acheckvalve47 is provided in parallel with restrictor46.

Downstream of restrictors 43 and 46 conduits 41 and 42 combine into a single conduit 48 which opens into porting 49 thus common to both conduits 41,42 and disposed in the wall of cylinder 50 of unit 29 immediately adjacent the right-hand end wall thereof.

Thus conduits 41,42 are always in full communica tion with the annular chamber51 ontheright-hand side of piston 52 of unit 29 while chamber 53 to the left of the piston is in communication with atmospherethrough porting 54 and filter 55.

Acoil spring 56 is interposed between cylinder50 and a flange 57 on rod 30, thereby providing a mechanical bias for scoop-tu be 23 in the downward direction.

When the electric motor (not shown) is brought into operation and shaft 12 and member 16 are run up to desired rotational speed the scoop-tube 23 is in the position shown in Figure 1. Motor 35 may already be running, or alternatively is brought into operation, to drive pump 34, and valve 38 is opened. Since valve 45 is closed hydraulic fluid under pressure in conduit 39 passes only through conduit 41 and restrictor 43 into chamber 51 of unit 29 art a rate dependent on the setting of restrictor 43 and relief valve 40.

Thus piston 52 moves to the left in cylinder 50 at a relatively slow rate and in consequence tube 23 moves upwardly also at a relatively slow rate with respect to sleeve 24 so thatforthe first part ofthe start-up cycle of the fluid coupling the rate offlow of hydraulicfluid outthrough tube 23 from annular sump 20, and back in suitable manner into the fluid contained within the sumpformed by the casing 14, is relatively high. This results in the working chamber 19 being only partlyfilled and the rate of increase in the speed ofturbine 18 and shaft 13 is relatively low, indicated by the first part of the gradient of each of the graphical representations of Figure 2.

At this stage, and automatically by means not shown, valve 45 is operated to cause hydraulic fluid to pass through conduit 42 in parallel to that already flowing through conduit 41, so that hydraulicfluid now passes through porting 49 into chamber51 ata rate dependent on the settings of both restrictors 43 and 46 and the pressure setting of relief valve 40.

Thus the piston 52 now moves to the left in cylinder 50 at a relatively fast rate so that tube 23 is further withdrawn upwardly, and more quickly, and so that in the remainder of the start-up cycle the rate of flow of hydraulic fluid outthroughtube 23 from annular sump 20 and into casing 14 is now relatively low, with the resu It that now the working chamber 19 reaches its filled condition rapidly. As a result the rate of increase in speed ofturbine 18and shaft 13 is relatively high as indicated by the second part ofthe gradients shown in the graphical representation of Figure 2.

Thus the speed of turbine 18 and output shaft 13 rapidly reaches the speed of the input shaft, or substantially so, and the coupling isthenoperating in its full load transmitting condition.

By the above described two-stage operation ofthe scoop-tube 23 the bringing of output shaft 13 up to designed maximum speed is achieved very rapidly yet without any appreciable tendency of that shaft to deliver undesirably high power peaks of short duration which might otherwise cause damage to the driven apparatus.

It will be understood that subsequently, for discontinuing the drivethrough the coupling,thesolenoids of valves 38 and 45 can be de-energised whereupon chamber 51 of device 29 is placed in communication with the reservoir through conduits 48, 41 and 39 and the valve 38. The spring 56 then takes over to movescoop-tube 23 downwardly as far as possible in the annular sump 20 and as a result fluid iswithdrawn from the sump and from theworking chamber 19 sufficiently to effect stopping of shaft 13.

In the above embodiment the second stage of movement of unit 29 is caused to commencewhen the rotational speed of output shaft 13 reaches a predetermined percentage of its designed maximum operating speed. Figure 2 graphically illustrates alternative scoop-operating characteristics and alternative points of change from slow to fast scooptube travel, these being chosen to suit particular circumstances.

Byso providing valve means in association with our second conduit, adjustment inthetiming of change from slow scoop-tube rate to fast scoop-tube rate is readily obtainable.

Claims (8)

1. A hydrodynamic coupling and control means therefor including means whereby working fluid is enabled to gain access to the working chamber ofthe coupling, an adjusting mechanism for controlling the extentoffilling of said working chamber by change in the rate atwhichtheworking fluid iswithdrawn from said working chamber, an actuating meansfor controlling said adjusting mechanism over a starting period during which the coupling is graduallyfilled, said actuator means being offluid-pressu reoperable type, and a fluid pressure supply ci rcuit for said actuator means, said circuit including a source offluid under pressure and two generally parallel conduits by way of which said fluid under pressure can pass through common porting into one end of said actuator means, the first conduit including a first flow control means permitting flow through that conduitat a first predetermined rate and the second conduit including a second flow control means permitting flowthrough that conduit at a second predetermined rate, and said circuit further including valve means selectively operable to ensure that, for a first stage of movement of said actuator means, and thus movement of said adjusting mechanism at a relatively slow rate, flow offluid to said actuator means takesplacethrough saidfirstconduit,and,fora second stage of movement of said actuator means, and thus movement of said adjusting mechanism at a relatively fast rate, flow of fluid to said actuator means takes place additionallythrough said second conduit.

2. A hydrodynamiccoupling and control means therefor according to claim 1,wherein the said second stage of movement of said actuator means is caused to commence when the rotational speed of the output member of said coupling reaches a predetermined percentage of its designed maximum operating speed.

3. A hydrodynamic coupling and control means therefor according to claim 1 or2, wherein thevalve means includes a valve disposed in said second conduit immediately upstream of said second flow control means.

4. A hydrodynamic coupling and control means thereforaccording to claim 1,2 or3,whereinthefirst and second flow control means each comprises a flow restrictor which in suitable manner is adjustable as to its precise flow rate characteristics.

5. A hydrodynamic coupling and control means therefor according to any one of claims 1 to 4, wherein the adjusting mechanism comprises a linearly movable scoop-tube which is arranged to project into an annular compartment or sump which is rotatable with the input shaft of said coupling, said compartment being in communication with said working chamber ofthe coupling.

6. A hydrodynamiccoupling and control means therefor according to claim 5, wherein the actuator means comprises a piston-and-cylinder device, the piston of which is connected to said scoop-tube.

7. A hydrodynamic coupling and control means therefor according to claim 6, wherein said common porting is provided in the wall of the cylinder of the device and is open to one ofthe two chambers of said device separated by said piston.

8. A hydrodynamic coupling and control means therefor substantially as herein before described with reference to the accompanying drawings.