DE4438771A1 - Automatic switch-off system for hydraulic load with occurrence of leakage - Google Patents

Abstract

The vol. flow measuring motors are respectively fixed to the endfaces of the valve housing. The shafts of the motors are mutually aligned and lie inside the valve housing. The shaft (1) of the measuring motor (9) transmits the shaft rotational movement on to a sliding sleeve movable axially on the shaft (1). The shaft (2) of the measuring motor (10) is connected with this sliding sleeve across a thread. The sliding sleeve moves axially with a sliding piston. The sliding piston with the valve housing forms a 5/4 way valve, provided with connections (P,T,A,B,H). The sliding sleeve following the unscrewing of the screwed connection: slider sleeve/thread rod, is held in a selected position by plates and springs. In the event of a leakage, the connection (H) is connected without pressure.

Description

The invention relates to a device for automatic Shutdown of a hydraulic consumer at Leakage occurs using two volume flow Measuring motors and a valve, the valve position in Dependence of the speeds of the two volume flow Measuring motors is determined.

The object underlying the invention is a leak in a hydraulic consumer reliable detection and a (hydraulic) signal for To be made available if the leak occurs.

In hydraulics, a liquid, mostly oil, becomes a exposed to high pressure. If the liquid fails leading components (e.g. hoses) Pollution of the environment and endanger the Operating personnel of the corresponding system, if this is not switched off immediately.

Hose rupture safety devices are known which are based on a Pressure drop in the hydraulic system or on a react sudden increase in volume flow. Kick however due to the system, these states in normal operation of a hydraulic consumer, so this hose break protections are not used.

On the other hand, it is known that in a faultless system the sum of all in and out of the system flowing currents must be zero. This applies to the Electrical engineering (see residual current circuit breaker) as well as for the hydraulics (current here: volume flow).

This principle is used in hydraulics to detect a However, leakage is rarely used. The reason for this is to search in that the volume flow information mostly first be converted into electrical signals and then the Summation also made electrically / electronically becomes.  

This requires a high level of technical equipment and is accordingly expensive.

Another problem is the accuracy of the volume flow Transducer. A measurement inaccuracy leads to a wrong one Totaling, so is the hydraulic consumer switched off, even if no leakage has occurred.

According to the invention is the task set solved in that from the rotational movement of two Volume flow measuring motors a spool movement of a Valve is generated, which is the volume flow difference volume flows through the measuring motors proportional is. When a certain volume flow difference occurs the valve provides a hydraulic output available, with the help of the hydraulic Consumer switched off in the event of a leak (fault) can be.

The device works on the above. Principle of Summation of the currents flowing into a system with the currents flowing to the system.

A shutdown of the consumer due to measurement inaccuracy the volume flow measuring motors is prevented by Volume flow measuring motors, each with two displacement volumes Settings are used.

The swallowing volume adjustment is dependent on the Piston slide position made. This ensures that the spool is in faultless operation (no Leakage or hose break) has the tendency in the To remain in the middle position.

The device is based on purely hydraulic / mechanical Working principles and does not require any auxiliary electrical energy.

In the drawings Fig. 1 to Fig. 8, the invention is illustrated, for example and in a schematic view, partly in section.

Fig. 2 shows the symbolic representation of the inventive device.

In FIGS. 3 to FIG. 7, the parts (1), (2), (3), (4), (5) of Fig. 1 are shown again individually. FIG. 6 shows a side view of FIG. 5.

Fig. 8 is a sectional view of the volume flow measuring motor ( 9 ) or ( 10 ). In this Fig. 8, the parts ( 11 ), ( 12 ), ( 13 ), ( 14 ), ( 15 ), ( 16 ) are shown.

In Fig. 9, the integration of the inventive device is illustrated in a hydraulic system.

The shaft ( 1 ) of a volume flow measuring motor ( 9 ) carries a driver connection (e.g. feather key). The driver connection transmits the rotary movement of this measuring motor to a slide sleeve ( 4 ). This slide sleeve is axially movable on the measuring motor shaft ( 1 ).

The shaft ( 2 ) of a second volume flow measuring motor ( 10 ) drives a threaded rod ( 3 ). This threaded rod ( 3 ) is torsionally rigid and axially rigid on the shaft ( 2 ).

The thread (right-hand thread) of the threaded rod ( 3 ) engages in an internal thread of the slide sleeve ( 4 ); ie if the shaft ( 1 ) stands and the shaft ( 2 ) rotates (or vice versa), the slide sleeve ( 4 ) is forced to move axially.

If the shafts ( 1 ) and ( 2 ) rotate at the same speed, but with the opposite direction of rotation (e.g. shaft ( 1 ) clockwise (positive), shaft ( 2 ) counterclockwise (negative)), the slide sleeve ( 4 ) stops axially ( Direction of rotation right / left when looking at the waves).

The deflection of the slide sleeve ( 4 ) is therefore proportional to the total rotation of the shafts ( 1 ) and ( 2 ):

Deflection ∼ (sum (n1 + n2))
n1: shaft speed ( 1 ); n2: shaft speed ( 2 ).

The slide sleeve ( 4 ) axially moves a piston slide ( 5 ) with the help of two rings. Together with the valve housing ( 6 ), this spool ( 5 ) forms a hydraulic 5/4-way valve (5 connections, 4 positions) (symbol Fig. 2).
The connections are: pressure connection P; Tank connection T.
The outputs are: connection H, A, B.

The positions of the 5/4-way valve are designated S1, S2, S3, S4.
S2: middle position, sum (n1 + n2) equal to zero;
S3, S4: sum (n1 + n2) is positive;
S1: sum (n1 + n2) is negative;
(Sign regulation: n1 = clockwise = positive; n2 = counterclockwise = negative).

In positions S1, S3, S4 the valve provides the outputs A and B available. These outputs are used for Realization of the automatic zero adjustment (see below).

The positions S1, S2, S3 are normal positions that Position S4 indicates the fault, i. H. the sum (n1 + n2) is positive and n1 »n2. In this position S4 the output H is connected to the tank connection (fault e.g. E.g. hose break).

In positions S1, S2, S3, S4, the external thread of the threaded rod ( 3 ) is in engagement with the internal thread of the slide sleeve ( 4 ).

When positions S1 or S4 are exceeded, the threads turn apart (undefined operating state in the hydraulic system). The piston slide ( 5 ) with slide sleeve ( 4 ) is then held axially in the last position by the washers ( 7 ) and springs ( 8 ).

Only with a relative reversal of the direction of rotation of n1 and n2 engage the threads again.

All volume flows Q1 flowing to a consumer are guided through the volume flow measuring motor ( 9 ) with the shaft speed n1 = Q1 / V1 or n1 = Q1 / VA (clockwise, positive if the flow direction is shown);
(n: speed, V: absorption volume, Q: volume flow).

The volume flow measuring motor ( 9 ) is a measuring motor with two displacement volume positions V1 and VA. At a control pressure at A, the measuring motor has the displacement volume position VA; there is no control pressure A, the displacement volume position V1.

All volume flows flowing back from the consumer Q2 are guided by the volume flow measuring motor ( 10 ) with the shaft speed n2 = Q2 / V2 or n2 = Q2 / VB (counter-clockwise, negative).
V2: Displacement setting at control pressure B equal to zero
VB: Swallowing volume when control pressure B is applied

In Fig. 8, the volume flow measuring motors ( 9 ) and ( 10 ) are shown as an example in section.

In this case, the measuring motors are vane-cell motors with an adjustable slide ring ( 15 ).

With the adjusting screw ( 11 ) the slide ring ( 15 ) is adjusted so that the absorption volume of the measuring motors ( 9 ) and ( 10 ) are the same (V1 = V2).

This adjustment work is done on both (structurally identical) measuring motors ( 9 ), ( 10 ) at a control pressure of A, B equal to zero.

The cylinder housing ( 12 ) is arranged together with the control piston ( 14 ) in an axially movable manner in a bore. The spring ( 16 ) holds the slide ring ( 15 ) in the position specified by the adjusting screw ( 11 ).

With a control pressure at A or B, pressure oil enters the chamber ( 13 ) of the cylinder housing ( 12 ) - the control piston ( 14 ) extends and adjusts the slide ring ( 15 ) against the spring ( 16 ), the swallowing volume is then VA or VB.

The following applies:

V1 = V2 ± deltaV

deltaV is the swallowing volume deviation, this deviation (Inaccuracy) leads to the same volume flows Q1 and Q2 at different output speeds n1 and n2 (Measurement inaccuracy).

VA and VB must be designed (stroke of the control piston ( 14 )) that

VA - V1 <deltaV

and

VB - V2 <deltaV

is.  

If n1 <n2 (Q1 <Q2), the spool ( 5 ) of the 5/4-way valve moves to the left into positions S3 and S4; with n2 <n1 (Q2 <Q1) to the right in position S1. In positions S1, S3 and S4, ports A and B are pressurized. This then turns the measuring motors with the speeds n1 = Q1 / VA or n2 = Q2 / VB (i.e. slower compared to n1 = Q1 / V1 or n2 = Q2 / V2, since VA <V1 and VB <V2!).

That means after a piston slide movement of the valve the speed n1 is shown on the left by the swallowing volume magnification smaller, with a spool movement speed n2 to the right.

This mechanism (automatic zero adjustment) means that the spool ( 5 ) of the 5/4 valve always tries to return to the central position S2.

If a speed difference n1 = Q1 / VA <n2 = Q2 / V2 occurs, ie Q1 »Q2 (e.g. due to hose break), the piston ( 5 ) moves into position S4. In this position, the control line H is depressurized.

As an external circuit of the device according to the invention, it is advisable to switch off a shut-off valve (abbr. AV) with the help of the connection H in this case and thus to disconnect the hydraulic consumer from the network ( FIG. 9).

Once the error has been rectified, the consumer can Actuation of a restart valve (abbr. WV) again with the hydraulic supply. This happens by the WV the measuring motor in Return flow until a volume flow is supplied until the 5/4-way valve returns to the middle position has adjusted (n2 <n1: spool of the 5 / 4- Directional control valve moves to the right).

Claims (2)

1. Device for automatically switching off a hydraulic consumer when a leak occurs by means of two volume flow measuring motors and a valve, the valve position of which is determined as a function of the rotational speeds of the two volume flow measuring motors, characterized in that

• - The two volume flow measuring motors ( 9 ) and ( 10 ) are attached to the end of the valve housing ( 6 ),
• - The shafts ( 1 ), ( 2 ) of the volume flow measuring motors are aligned with one another and lie within the valve housing ( 6 ),
• - The shaft ( 1 ) of the volume flow measuring motor ( 9 ) transmits the shaft rotation to an axially displaceable on the shaft ( 1 ) slide sleeve ( 4 ) and the shaft ( 2 ) of the volume flow measuring motor ( 10 ) via a thread ( 3 ) is connected to this slide sleeve ( 4 ),
• - The slide sleeve ( 4 ) moves a piston slide ( 5 ) axially,
• - The spool ( 5 ) forms a 5/4-way valve with the valve housing ( 6 ) (connections P, T, A, B, H),
• - The slide sleeve ( 4 ) after unscrewing the threaded connection, slide sleeve ( 4 ) / threaded rod ( 3 ) is held in a defined position by washers ( 7 ) and springs ( 8 ),
• - In the event of a leak, port H is depressurized.

2. Device according to claim 1, characterized in that

• - The volume flow measuring motor ( 9 ) has the swallowing volume settings V1 and VA, the volume flow measuring motor ( 10 ) has the swallowing volume settings V2 and VB, where V1 = V2 and VA <V1 and VB <V2,
• - The displacement volume adjustment of both volume flow measuring motors ( 9 ), ( 10 ) in dependence on the piston slide position ( 5 ) is carried out through the connections A and B.