GB1560348A

GB1560348A - Methods of and apparatus for delaying the commencement of braking in regulated transport drives

Info

Publication number: GB1560348A
Application number: GB2965177A
Authority: GB
Original assignee: Loher GmbH
Current assignee: Loher GmbH
Priority date: 1976-09-17
Filing date: 1977-07-14
Publication date: 1980-02-06
Also published as: FR2364847A1; AT353441B; FR2364847B1; IT1084884B; CH629729A5; ATA412277A; DE2641983A1; ES462407A1; DE2641983C2

Abstract

The braking command is triggered, particularly in a lift drive, in dependence on two guide curves (VS1, VS2) which correspond to two voltages (Usoll, Ucomp) and on a third voltage (UX). The first guide curve represents the start-up variation, that is to say the speed of travel as a function of time. The second guide curve is the nominal braking variation in the same type of representation. The said third voltage is obtained by integrating the difference between these two guide curves in that the voltages corresponding to the guide curves are supplied to the input of an integrating section and the third voltage appears as output voltage at the output of this section. The voltages corresponding to the guide curves and the said output voltage are supplied to a comparator. The output signal of the comparator is used as braking command. This braking command delays the initiation of the braking process to a time (t1) so that a maximum speed is reached at the switch-over point. In this manner, the so-called crawling distance can be kept to an optimum shortness. <IMAGE>

Description

(54) METHODS OF AND APPARATUS FOR DELAYING THE COMMENCEMENT OF BRAKING IN REGULATED TRANSPORT DRIVES (71) We, LOHER GMBH ELEK TROMOTORENWERKE, a body corporate organised and existing under the laws of the Federal Republic of Germany, of 8399 Ruhstorf/Rott, Federal Republic of Germany, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to methods of and apparatus for delaying the commencement of braking in regulated transport drives, particularly (but not exclusively) lift drives.

Preferred embodiments of the invention described hereinbelow provides for a time delay of the commencement of braking, more particularly of the switch-over point from driving to braking, with the object, particularly for example in the case of rapidly moving lifts, of also controlling travel between adjacent floors so that as large a distance as possible will be traversed at the highest possible speed so as to reduce to a minimum the time that is required for a given journey.

If a lift car is moved over long distances, the full speed of travel is attained after an accelerating interval and is kept constant up to a particular point in the journey. This point in the journey is disposed upstream of the target floor (target stop or target point), initiates the braking stage and will hereinafter be referred to as the brake switch (brake lug). Generally, this brake switch is provided at the floor and is actuated by the passing car, or the brake switch is provided on a so-called copying mechanism and is operated by a cam that moves simultaneously with the car.

Since the brake switch is disposed at a predetermined fixed distance upstream of the target stop, a certain distance will be available for braking. The distance required for braking is calculated by the formula V2 max S (1) 2b In this formula, s=the braking distance Vmax=the maximum speed b=the retardation (negative acceleration).

In formula (1), the maximum speed Vmax is employed because the braking distance must be dimensioned so that the car coming from a remote stop and certain to have reached Vmax can be braked at the target.

If the car is moved between two adjacent floors, it may happen that, particularly in the case of rapidly moving lifts, the brake switch is already actuated before the car has reached its full speed of travel. This makes the braking distance very short because in formula (1) one would have to replace Vmax with the lower speed of travel V actually reached: V2 s= (2) 2b If, as is usual, the braking stage is followed by an interval of creeping travel (fine travel), the distance for a prematurely braked car up to reaching the target stop will become very long and this will take a very long time, particularly in the case of a low creeping speed.

Austrian Patent Specification 248,057 describes a method in which the commencement of braking is delayed. This method does not take the instantaneous speed of the car into account and works inaccurately.

German Patent Specification 1,488,397 describes a method according to which two speed versus time guide curves which are represented by time-dependent voltages move towards one another in such a way that the value happening to be the minimum prescribes the speed. This method has the disadvantage that, as will be explained later, one loses a distance that must be compensated again by a long creeping path.

Similarly, German Accepted Patent Application (DE-AS) 2,047,281 describes two speed versus time guide lines, the guide lines for the starting stage approaching the maximum speed and the guide line for the braking stage approaching zero. The lower of the speeds prescribed by the guide curves represents the desired value speed.

German Published Patent Application (DE-OS) 2,004,812 describes a method in which the degree of retardation is influenced by a signal that depends on the spacing. This has the disadvantage that the properties of travel are different for long distances than for short journeys during which the lift car does not reach the maximum speed.

According to the invention there is provided a method of delaying the commencement of braking in a regulated transport drive, comprising generating two speed versus time guide curves of which a first initially rises from zero to govern driving and the second is initially at a value greater than zero and starts to fall only upon the appearance of a braking command to govern braking, wherein the commencement of braking is delayed after the appearance of the braking command at least until the second curve drops so far that the first and second curves intersect, and wherein the first curve starts to fall after the first and second curves intersect.

In preferred embodiments of the present invention described hereinbelow the switching-over point from driving to braking is so delayed relatively to the braking command of the brake switch as electronically calculated that as long a distance as possible is traversed at the highest possible speed.

An arrangement in accordance with the invention can be used as a desired speed value generator for a regulatable transport drive, which may in particular be a lift drive.

The invention will now be further described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a speed-time diagram for a lift for which the distance of travel is sufficiently large to enable the car to reach a maximum speed of travel; Figure 2 is a speed-time diagram for a lift of which the car does not reach the full speed of travel because of premature switching off; Figure 3 is a speed-time diagram for a lift in which the switching-over point from driving to braking is delayed, in accordance with a first embodiment of the invention, by introducing a speed versus time guide curve; Figure 4 is a speed-time diagram for a lift in which a time delay of the switching-over point is brought about, in accordance with a second embodiment of the invention, by electronic evaluation; and Figure 5 is an example of the circuitry of an arrangement for achieving the delay effect of Figure 4.

Figure 1 diagrammatically illustrates the diagram of travel of a lift. The speed V of the lift is plotted against time (t). On commencement of travel, at t=0, the speed first of all increases with a finite acceleration up to a maximum value Vmax.

At an instant t1, the drive starts to brake with a finite retardation and finally reaches a creeping speed Vo. At an instant t2, the installation is again braked with a finite retardation and reaches a standstill at an instant t3.

In the case of lifts, particularly those having a high speed, the distance to be traversed by the lift between the instants t1 and t2 is very large. Accordingly, the switching-over point on commencement of braking at t1 is disposed very far upstream of the target point t3. This means, particularly when travelling between adjoining stops, that braking might have to commence even during the starting stage.

Fig. 2 shows a diagram in which the braking stage takes place within the starting zone, i.e. before the maximum speed is achieved. Since braking is here not started at the maximum speed of travel but at a lower speed corresponding to the instant t1, the creeping speed Vo is reached sooner.

The cross-hatched area S1 in Fig. 2 representing a distance is initially lost and must be caught up again by an area S1' as a distance during creeping travel. The area S1' is equal to the area S1 and therefore also represents the same distance as does the area Si. This behaviour requires undesirably long periods of creeping travel.

According to an embodiment of the -invention now to be described with reference to Fig. 3, the introduction of a second speed-time guide curve brings about a comparison to delay the switching-over point at ti to such an extent that the area S is as small as possible.

Fig. 3 shows a first speed-time desired value curve VS1 according to which the actual speed of the lift is guided. A second speed-time guide curve VS2 runs at the elevation Vmax up to the appearance of a brake command at the instant ti.

Thereafter, VS2 drops off at an inclination corresponding to the inclination of the braking delay of VSI. The commencement of braking, more specifically the switching over point from driving to braking, does not take place at the point t1 (as it does in Fig.

2), but only at an instant t11 at which the two curves VSI and VS2 intersect (see Fig. 3).

The guide curve VS2 is represented by a proportional voltage Uconip. The desired value curve VSI is represented by a proportional voltage Use".

A voltage comparator compares these two voltages Usoi and Ucomp. At the point of intersection of these two curves VSI and VS2 there arises an output signal. Up to the appearance of this output signal, the commencement of braking is delayed. In the diagram of Fig. 3, this corresponds to a displacement of t1 tot11. One therefore saves a portion of the distance S, but one nevertheless still loses the distance S2 which must be caught up again by the distance S2' during the creeping travel.

Another embodiment of the invention now to be described with reference to Figs.

4 and 5 particularly provides for the displacement of the distance S2 by a further time delay so that it need no longer be caught up during creeping travel.

Accordingly, Fig. 4 shows an additonal displacement of the switching-over point from t,' to t,". The distance S2 represented as a cross-hatched area is caught up during the braking stage and appears as the area S2". This additional displacement is determined as follows.

Whereas the displacement of the switching-over point from t, to t,' occurs by means of a comparator according to Uso" UcomP=o (3) a third parameter is introduced during the displacement of the switching-over point to t"1.

This parameter Ux depends on the area S2 and can be formed by integrating the difference of the voltages UcOmpUso" with respect to tme:

T is a constant determined by the components of an electronic circuit to be described hereinafter.

The concept is to provide an arrangement so that it will produce an output signal when the following formula (5) is fulfilled:

This output signal appears at the instant t," and initiates the braking stage. The braking procedure then takes place according to the line VSI' (Fig. 4).

The principle of the construction of the electronic circuit is represented in Fig. 5, according to which the operation of formula (5) is carried out.

An operational amplifier 5 works as an integrator in conjunction with a capacitor 4.

The prerequisite that the output voltage of this integrator be zero on commencement of integration is ensured by a contact 3 which opens at the instant t,. Signals +Uso" and UCOmp are fed to the input of the amplifier 5 via respective resistors 1 and 2. The integral of the difference Uso"UcOmD appears at the input of the integrator. The voltage at the integrator output is inverted and appears at the output of an inverting amplifier arrangement 13, 14, 15 as the signal

The constant T is here determined by the capacitor 4 and the two resistors 1 and 2. If the resistance of the resistor 1 is equal to the resistance of the resistor 2 is equal to R and the capacitance of the capacitor 4 is equal to C, then T=R.C.

A comparator 9 receives the signals Ux +Uso" and Ucomp via resistors 6, 7 and 8, respectively. The comparator. 9 delivers a positive signal at its output, which is connected to the coil 11 of a relay via a diode 10, and the relay coil 11 remains attracted as long as the condition USo"UcomPUx < is fulfilled.

If Uso"UcOmpUx > 0, the output voltage of the comparator 9 becomes negative and the relay drops out. A contact set 12 of the relay then opens and initiates braking.

WHAT WE CLAIM IS: 1. A method of delaying the commencement of braking in a regulated transport drive, comprising generating two speed versus time guide curves of which a first initially rises from zero to govern driving and the second is initially at a value greater than zero and starts to fall only upon the appearance of a braking command to govern braking, wherein the commencement of braking is delayed after the appearance of the braking command at least until the second curve drops so far that the first and second curves intersect, and wherein the first curve starts to fall after the first and second curves intersect.

2. A method according to Claim 1, wherein the first and second curves are represented by respective proportional voltages.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

take place at the point t1 (as it does in Fig.

2), but only at an instant t11 at which the two curves VSI and VS2 intersect (see Fig. 3).

The guide curve VS2 is represented by a proportional voltage Uconip. The desired value curve VSI is represented by a proportional voltage Use".

A voltage comparator compares these two voltages Usoi and Ucomp. At the point of intersection of these two curves VSI and VS2 there arises an output signal. Up to the appearance of this output signal, the commencement of braking is delayed. In the diagram of Fig. 3, this corresponds to a displacement of t1 tot11. One therefore saves a portion of the distance S, but one nevertheless still loses the distance S2 which must be caught up again by the distance S2' during the creeping travel.

Another embodiment of the invention now to be described with reference to Figs.

4 and 5 particularly provides for the displacement of the distance S2 by a further time delay so that it need no longer be caught up during creeping travel.

Accordingly, Fig. 4 shows an additonal displacement of the switching-over point from t,' to t,". The distance S2 represented as a cross-hatched area is caught up during the braking stage and appears as the area S2". This additional displacement is determined as follows.

Whereas the displacement of the switching-over point from t, to t,' occurs by means of a comparator according to Uso" UcomP=o (3) a third parameter is introduced during the displacement of the switching-over point to t"1.

This parameter Ux depends on the area S2 and can be formed by integrating the difference of the voltages UcOmpUso" with respect to tme:

T is a constant determined by the components of an electronic circuit to be described hereinafter.

The concept is to provide an arrangement so that it will produce an output signal when the following formula (5) is fulfilled:

This output signal appears at the instant t," and initiates the braking stage. The braking procedure then takes place according to the line VSI' (Fig. 4).

The principle of the construction of the electronic circuit is represented in Fig. 5, according to which the operation of formula (5) is carried out.

An operational amplifier 5 works as an integrator in conjunction with a capacitor 4.

The prerequisite that the output voltage of this integrator be zero on commencement of integration is ensured by a contact 3 which opens at the instant t,. Signals +Uso" and UCOmp are fed to the input of the amplifier 5 via respective resistors 1 and 2. The integral of the difference Uso"UcOmD appears at the input of the integrator. The voltage at the integrator output is inverted and appears at the output of an inverting amplifier arrangement 13, 14, 15 as the signal

The constant T is here determined by the capacitor 4 and the two resistors 1 and 2. If the resistance of the resistor 1 is equal to the resistance of the resistor 2 is equal to R and the capacitance of the capacitor 4 is equal to C, then T=R.C.

A comparator 9 receives the signals Ux +Uso" and Ucomp via resistors 6, 7 and 8, respectively. The comparator. 9 delivers a positive signal at its output, which is connected to the coil 11 of a relay via a diode 10, and the relay coil 11 remains attracted as long as the condition USo"UcomPUx < is fulfilled.

If Uso"UcOmpUx > 0, the output voltage of the comparator 9 becomes negative and the relay drops out. A contact set 12 of the relay then opens and initiates braking.

WHAT WE CLAIM IS: 1. A method of delaying the commencement of braking in a regulated transport drive, comprising generating two speed versus time guide curves of which a first initially rises from zero to govern driving and the second is initially at a value greater than zero and starts to fall only upon the appearance of a braking command to govern braking, wherein the commencement of braking is delayed after the appearance of the braking command at least until the second curve drops so far that the first and second curves intersect, and wherein the first curve starts to fall after the first and second curves intersect.
2. A method according to Claim 1, wherein the first and second curves are represented by respective proportional voltages.
3. A method according to Claim 2,

wherein braking is commenced when the first and second curves intersect, that is to say when the two voltages are equal.
4. A method according to Claim 1, wherein the values of the two curves are compared with a parameter obtained by integrating the difference between the values of the two curves and braking is commenced after the two curves have intersected and when the difference between the values of the two curves and becomes equal to said parameter.
5. A method according to Claim 4, wherein the first and second curves are represented by respective proportional voltages (U,,,, and UcOmp) and said parameter (U5) is formed by integrating with respect to time the difference between the two voltages, whereby braking commences at a time (t1,,) when U5011-U compUx=0, the parameter Ux being given by

where T is a constant and ti is the time of arrival of the braking command.
6. A method of delaying the commencement of braking in a regulated transport drive, the method being substantially as herein described with reference to Figure 3 or Figure 4 of the accompanying drawings.
7. Apparatus for performing a method according to Claim 3, including a voltage comparator operative to compare the two voltages and to produce an output signal to cause the commencement of braking when the voltages are equal.
8. Apparatus for performing a method according to Claim 5, comprising an operational amplifier having capacitive feedback whereby it functions as an integrator, means to maintain the output voltage of the operational amplifier at the value zero until the appearance of the braking command, and means for supplying one of the respective proportional voltage (Uso") and the inverse of the other (UcOmp) to the operational amplifier whereby the amplifier solves the integral equation for Ux set forth in Claim 5.
9. Apparatus according to Claim 8, including an inverting amplifier connected to the output of the operational amplifier to form the expression -U5 and means to sum -U5, Usor and UcOmp to determine when Uso"UcomPUx= -
10. Apparatus for delaying the commencement of braking in a regulated transport drive, the apparatus being substantially as herein described with reference to Figure 5 of the accompanying drawings.