DE3838496A1 - Safety circuit for the control of hoists - Google Patents

Abstract

The invention relates to a safety circuit (8) for the control of hoists, especially of ploughs (1). According to the invention, control via the safety circuit (8) is only activated if the desired force value (WK) is smaller than the negative value of the actual force value signal (-XK), the stroke-limiting desired value (WHB) is greater than the actual position value signal (XL) and, at the same time, equality between the desired position value (WL) and the actual position value signal (XL) has been produced via the desired position value setter or digging arm, or this condition is passed. It is thus achieved that, upon activation of the control, no unexpected and uncontrolled movements occur on the hoist. <IMAGE>

Description

State of the art

The invention relates to a safety circuit for the rain Development of hoists, especially plows on agricultural machinery nen.

In a known safety circuit for regulating hoists on agricultural machinery, the regulation comprises a setpoint adjuster for specifying a setpoint for the force as a force setpoint ( W _K ) and for the position as a position setpoint ( W _L ). Corresponding actual value transmitters are also provided for a force actual value X _K and an actual position value X _L. With a mixer actuator, the tool attached to the hoist can be regulated either to constant tractive force or constant position or a defined combination of these quantities or a mixture of the two associated signals. The mixer controller can be set to pure position control or pure force control as well as an intermediate position to mix both controls. Furthermore, a stroke limitation is known which limits the stroke of the hoist or the tool attached to it to a maximum set stroke value prior to the control.

Such a device must be used for safety reasons  be guaranteed that when starting the device and the existence of a difference between the setpoint and actual value deflectable hoist not automatically ver to the setpoint is posed. For example, in a tractor Height of the hoist set by a lever, it can happen that after turning off the tractor the lever is adjusted so that when switched on again a difference between the actual height of the hoist and the set one Height is present. Without an appropriate safety circuit the hoist would then automatically move into position corresponds to the lever position. Since this with considerable Ge driving is connected, it is necessary to have a security circuit to create the uncontrolled deflections Prevent start-up of the device.

Means are provided in the known safety circuit when commissioning the adjustment device and available the difference between the setpoint and actual value Lock element on the actual value and that the locked, deflectable hoist when adjusting the setpoint to the Actual value is unlocked.

However, dangerous states and movements can occur if pure force control is selected on the mixer: If the set power setpoint ( W _K ) is less than the weight of the hoist or plow, the plow is lowered using the force control. However, if the force setpoint W _{K is} set higher than the weight of the plow, the plow will move to its uppermost position. In the known safety circuit, the force setpoint W _K must be adjusted to the actual force value X _{K in order} to activate the control when pure force control is set. However, this state corresponds to an unstable equilibrium state, since slight deviations and adjustments to the force setpoint compared to this state trigger a lifting or lowering. Thus, in most cases, the operation triggers a movement when activated, which is also unexpected because only the safety circuit should be unlocked. Such unexpected and uncontrolled movements are dangerous and can lead to accidents.

Another safety circuit is known, which in a control system with separate setpoints for the location and force control works. The regulation becomes active fourth, that the setpoint for the position control via the so-called called lifting lever is brought into the uppermost position. Then the control starts immediately with the lifting process, if the hoist or plow is not already in the top one Position. This movement can usually be seen there by stopping the lifting lever from being withdrawn. Is but the force setpoint depending on the set mixture for Force control, position control or any intermediate stood at a high enough value, then lifts the scheme accordingly, without having to withdraw the off to respond to the lever. The reason for this is that the higher setpoint always dominates what is normal Regular operation is also useful and appropriate. At the present the activation process can dominate the higher Setpoint for uncontrolled and dangerous movements during the activation process.

Advantages of the invention

With the safety circuit according to the features of the claim 1 is achieved that when starting up a machine, for example, a tractor, the regulation first does not work according to the control function, as this is too un controlled, unexpected and accident-prone movements of the hoist. In particular, there is such a prevailed when in the parked state setpoints, Mixing ratios between position and force control, end position limits and the like have been adjusted. over the safety circuit activates the rain only if three conditions are met, in the case of which Hazardous movement conditions are excluded.  

drawing

An embodiment of the invention is shown in the drawing shown and in the description below he purifies.

Show it:

Fig. 1 is a diagram showing the dependence of the actual position value X _L from the set force setpoint W _K,

Fig. 2 is a block diagram of the safety circuit,

Fig. 3 is a flowchart illustrating the working of the safety circuit.

In the coordinate system of FIG. 1 of the force target value _K is plotted W and upwardly of the actual position value X _L to the right. The zero point for the actual position value X _L corresponds to the top edge of the floor. Negative values of X _L thus mean that a plow treated in the previous exemplary embodiment has been introduced into the ground and positive values of X _L mean that the plow has moved out of the ground. The drawn-in distance AB thus corresponds to the excavation path for the plow above the ground, the horizontal line at point A corresponding to the highest possible position of the plow.

The force setpoint W _K on the vertical line AB corresponds to the weight of the plow. The plow is raised to its uppermost position when the force setpoints are high and a pure force control is set; when the force setpoints are lower, the plow is lowered.

In the block diagram of FIG. 2, a plow 1 is shown schematically, which is attached to a linkage 2 with a lifting device and can thus be raised and lowered. From the type of suspension, especially when looking at the approximately horizontal strut 3 , it can be seen that in the event that the plow 1 has been sunk into the ground and the tractor (not shown) pulls to the right, a counterforce on the plow 1 is applied to the left.

Via the strut 3 and an articulated, spring-loaded pressure plate 4 , an actual force value transmitter 5 is applied, which emits an actual force value signal X _K. Due to the described plow suspension it can be seen that the actual force value signals X _{K of} the actual force value transmitter 5 become smaller and greater tractive forces on the plow 1 , since the pressure plate 4 then lifts more from the actual force value sensor 5 . The actual value signal X _K is thus to be evaluated with the opposite sign in the control or to be multiplied by minus 1.

If, on the other hand, the plow was raised above the ground, the plow 1 presses according to its weight over the stre 3 because of its suspension diagonally upwards on the pressure plate 4 . The actual force value X _{K determined} corresponds to the weight of the plow 1 and (in the static case) assumes its greatest value here. See also the illustration in FIG. 1.

Furthermore, a position actual value transmitter 6 is provided, which is more or less strongly deflected via a cam 7 according to the plow position and emits a position actual value signal X _L.

The Lageistwertsignal X _L and X Kraftistwertsignal _K are fed to a safety circuit 8, in which the Kraftistwertsignal X _K is compared in a first comparator 9 with the adjusted power target value W _K in a first release condition. If the set power set value W _K klei ner than the negative value of the Kraftistwertsignals (- X _K) supplies a first enable signal is generated on line 10 degrees. This first condition ensures that the plow 1 with switched on (and later activated) pure force control or accordingly their mixing ratio has the tendency to move the plow 1 down. The most dangerous condition is when the plow could be driven up into the cab unexpectedly and in an uncontrolled manner.

Furthermore, the position actual value signal X _{L is} compared with a set stroke limitation setpoint W _HB in a second comparator 11 . If the stroke limitation setpoint W _{HB is} greater than the actual position value X _L , a second enable signal is generated on a line 12 . Since the stroke limitation and thus the stroke limitation setpoint W _{HB have} priority over the rest of the control, the plow would be lowered unexpectedly to the set, lower stroke limitation value when the control was activated without the above condition.

The presence of the two above conditions or the release signals on lines 10 and 12 is required for a release of the control simultaneously and in parallel. Therefore, these enable signals are fed to an AND gate 13 . In the presence of the two conditions, the AND gate 13 switches through, a summarized release signal is generated on a line 14 , which is fed to a further AND gate 15 . With an AND gate 15 connected through, the control 17 is activated via the line 16 , which is shown schematically by a switch 18 .

For this purpose, a further condition on the AND gate 15 is that the condition is detected in a third comparator 19 that the position setpoint W _{L is} equal to the actual position value X _L or that this state is achieved by adjusting the position setpoint adjuster, the so-called lifting lever or happened. Then, the second signal for the through circuit of the AND gate 15 is generated via line 20 , so that the control 17 is activated. The activation is thus carried out via the excavation lever or the position setpoint adjuster when the first two conditions are met, the position setpoint and actual position value being brought into line, and it is also sufficient to run over this state. This is essential and advantageous, since to activate the control the state where the position setpoint and actual position value coincide does not have to be searched exactly, which would be an uncomfortable search task if the dead zones were included. On the other hand, the plow can be directed and adjusted immediately with the lifting lever based on the actual position value; the plow practically "hangs" on the lifting lever immediately after activation. This case corresponds to the normal case when pure position control or at least one position control part has been set via the mixer. If pure force control is set, it is accepted that when activated, the plow will lower to the ground in a controlled manner due to the first condition (this can also be prevented if the activation is only permitted in pure position control), but no dangerous movement in the direction of the driver's cabin.

The function of the safety circuit is explained again using the flow diagram according to FIG. 3:

The first condition for the activation of the regulation is the tendency to lower the plow from the force regulation by the condition W _K less - X _K. The negative sign is because of the conditions already described he required that the smallest force setpoints W _K correspond to the greatest tensile forces.

As a second condition for the activation of the control system, it is required that the stroke limitation setpoint W _{HB is} above the actual position value, so that the stroke limitation does not intervene when the control system is activated.

If the first two conditions are met, the last requirement is that the position setpoint W _{L is made to} coincide with the position actual value X _L via the position setpoint lever or lifting lever, or that this position has been briefly passed, whereupon the control is activated and responds and the plow 1 can usually be directed with the lifting lever over the position control.

Claims (1)

Safety circuit for the control of hoists, in particular of plows on agricultural machines, the control each having a setpoint adjuster for specifying a setpoint for the force as a force setpoint ( W _K ) and for the position (lifting lever) as a position setpoint ( W _L ), one each Actual value transmitter as a force actual value transmitter ( 5 ) for emitting a force actual value signal ( X _K ) and as a position actual value transmitter ( 6 ) for emitting a position actual value signal ( X _L ), a mixer actuator for setting the mixing ratio between force and Position control component, a controller ( 17 ) and a stroke limitation that works primarily before the force and position control with a setpoint adjuster for a stroke limitation setpoint ( W _HB ), the control can be activated via a safety circuit ( 8 ) and the hoist ( 1 ) is suspended in this way that largest tensile forces belong to the smallest force setpoint ( W _K ), characterized in that in the safety circuit ( 8 ) with a first comparator ( 9 ) the set desired force value ( W _K ) is compared with the negative value of the actual force value signal (- X _K ) and in the event that the desired force value ( W _K ) is smaller than the negative value of the actual force value signal ( - X _K ), a first enable signal (line 10 ) is generated, that the set stroke limitation setpoint ( W _HB ) of the stroke limitation is compared with the actual position signal ( X _L ) using a second comparator ( 11 ) and in the event that that the stroke limitation setpoint ( W _HB ) is greater than the actual position value signal ( X _L ), a second enable signal (line 12 ) is generated, that with a third comparator ( 19 ) the desired position value ( W _L ) and the actual position value signal ( X _L ) are compared and if they are the same ( W _L = X _L ) or if this state is reached or passed by adjusting the position setpoint actuator (lifting lever), the control via the safety circuit or an AND Linkage ( 15 ) activated and released will when the first and second enable signal (lines 10, 12 ) are generated at the same time.