Vertical conveying apparatus

Apparatus for conveying goods in vertical direction, such as a stacker crane or elevator, with a lifting unit and an emergency braking system which influences the lifting unit as soon as a preselectable speed is exceeded. The braking system comprises two wedges connected to an endless rope drive moving synchronously with the lifting unit. The rope drive moves only up to a preselectable top speed, and as soon as a speed difference between rope drive and lifting unit occurs, the brake wedges are activated and decelerate the lifting unit progressively until it stops.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention refers to a vertical conveying apparatus with a 
lifting unit guided in two guiding rails and with an emergency brake which 
influences the lifting unit as soon as a preselectable lifting speed is 
exceeded, to decrease the speed of the lifting unit. Such an apparatus is 
intended to work at high speed and acceleration even if the lifting unit 
is heavily loaded and must provide absolute safety against damage and 
accidents as a consequence of too high a lifting speed of the lifting 
unit. 
2. Description of the Prior Art 
For emergency brakes to be used with such apparatus or with elevators for 
humans, which are used to switch off the driving gear and to safely stop 
the lifting unit, it is imperative to provide a system which works 
absolutely reliably and effectively. The emergency braking systems known 
in the prior art work abruptly inasmush as a braking wedge provided with a 
toothed surface is suddenly pressed against a guiding or braking rail, 
whereby it often happens that the tooths of the braking wedge damage the 
surface of the guiding or braking rail, which is then ruined and subject 
to re-machining or replacement. The braking effect is very abrupt and the 
releasing of the braking system is sometimes very difficult. If the 
lifting unit is heavily loaded or subjected to a great acceleration or 
deceleration, there occurs the danger that passengers on the lifting unit 
may be severely injured by the sudden stop common to the emergency braking 
systems of the prior art. This danger can only partially be avoided by 
overdimensioning the driving and braking system. 
If an automatic position coding system is used with such an apparatus, it 
may happen that the lifting unit stops between two distance marks if the 
emergency braking system is activated, thereby rendering it impossible to 
determine the actual position of the lifting unit by means of the remote 
control system. 
OBJECTS OF THE INVENTION 
It is an object of the present invention to propose a vertical conveying 
apparatus with a lifting unit guided by two vertically arranged guiding 
rails and equipped with an emergency braking system, which avoids the 
disadvantages mentioned above. A further object of the invention is to 
provide such an apparatus with an emergency braking system which, once 
actuated, decelerates the lifting unit progressively but nevertheless 
reliably, as soon as a predetermined conveying speed is exceeded. 
SUMMARY OF THE INVENTION 
The apparatus according to the invention comprises at least two braking 
wedges, each acting on a pair of vertical guide rails and movable together 
with the lifting unit and displaceable in relation to this lifting unit. 
The wedges are floatingly suspended from a lever mechanism and are 
connected to an endless rope drive moving synchronously with said lifting 
unit whereby a decrease in the speed of the rope drive relative to the 
speed of the lifting unit causes a displacement of said braking wedges to 
decelerate and stop the motion of said lifting unit. The braking wedges 
are arranged to cooperate with a parallel wear strip, one strip at each of 
the two lateral shoulders of the head of the guiding rails so that each 
wedge comes into instantaneous full face braking engagement with its 
corresponding parallel wear strip and are slideably received in supporting 
members to be displaceable in a horizontal direction by wedging action 
relative to said supporting members. The supporting members are joined by 
two or more parallel bolts which engage cup springs and washers to a 
supporting block rigidly connected to the lifting unit whereby the braking 
wedges move in full face engagement against the parallel wear strips 
against the spring forces of the cup springs of said bolts to gradually 
increase the wedging pressure from gentle pressure to full force braking. 
Thus the brake falls downwardly in full face engagement and is drawn by 
lever means and by frictional forces between the face of the wedge and the 
left shoulder of the head of the guide rail between the wear strip and the 
right shoulder of the guide rail head until the wedge has fully compressed 
the springs associated with the outwardly movable support block.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The stacker crane shown in FIG. 1 comprises two lifting posts 1 which are 
arranged on a base plate 13. The base plate 13 is travelling on rails 4 
which are arranged on the ground floor. A driving gear 5 is provided to 
drive the stacker crane along the rails 4. On the top, there is provided a 
horizontal guiding rail 2' to guide the stacker crane and to improve its 
stability. Each of the lifting posts 1 is equipped with a vertically 
extending guiding rail 2 which receive and guide a lifting unit 3. A rope 
drive 7 is provided to lift and lower the lifting unit 3, which comprises 
a driving gear 6. The stacker crane is equipped with an emergency brake to 
decelerate and stop the lifting unit 3 as soon as a predetermined lifting 
or lowering speed is exceeded by more than 40%. In the embodiment now to 
be further described, the normal lifting or lowering speed is 50 m/min, 
and consequently the emergency brake will be activated as soon as the 
speed exceeds 70 m/min. The travel of the lifting unit 3 is more than 18 
meters and the maximum load received on the lifting unit may be up to 5 
tons. 
As can be seen in FIG. 2, there are provided endless steel ropes 16 which 
are guided by sheaving pulleys 14 and 15 and which are connected to the 
lifting unit 3 to monitor its lifting speed. The upper sheaving pulley is 
rotatably arranged at the top of the guiding rail 2, while the lower 
sheaving pulley 15 is mounted on a tension slide 30 providing enough 
tension in the rope 16 that no slipping between rope 16 and pulleys 14 and 
15 can occur. The steel rope 16 is thereby connected to a lever 17 of the 
emergency brake, which is mounted on the lifting unit 3. 
The design and construction of the emergency brake can best be seen in 
FIGS. 4 and 5. The lifting unit 3 is provided with a support member 34, 
comprising on its left side a support block 12 and on its right side a 
counterpart 27. All three parts 34, 12 and 27 have a number of bores and 
are held together by means of rigid bolts 18 and nuts 18', whereby a 
number of distance washers 22 and cup springs 21 are inserted between nuts 
18' and support block 12 and a number of cup springs 20 are inserted 
between support member 34 and counterpart 27. The provision of the cup 
springs 20 and 21 enable the support block 12 and the counterpart 27 to be 
displaced along the bolt 18 in relation to the support member 34 by a 
small amount. Under the influence of the cup springs 21, the support block 
12 is pressed against the left side of the support member 34 and the 
counterpart 27 to the right side of the support member 34, whereby the 
amount of pressure can be selected by tightening the nuts 18' more or 
less. In this way the cup springs 20 and 21 can be selectively biased. 
The support block 12 comprises a protruding portion 12' reaching to the 
left shoulder 32 of the head 33 of the rail 2, while the counterpart 27 is 
equipped with a corresponding protruding portion 27' reaching to the right 
shoulder 32' of the head 33 of the rail 2. The protruding portion 12' has 
a groove which receives a braking wedge 10 with a guiding rod 24 bolted 
thereon. As can be seen in FIG. 4, the braking wedge 10 is suspended to 
the free end of the lever 17 by means of a linkage 11, whereby the lever 
17 is pivotably arranged by a connecting rod 9, the ends of which are 
rotatably received in two supports 19 and 19' mounted on the lifting unit 
3. On the other side of the lifting unit 3, there is provided, as shown in 
FIG. 3 a further lever 17' which activates a corresponding braking wedge 
(not shown). 
The upper sheaving pulley 14 comprises a built-in centrifugal governor 8 
which decelerates the pulley 14 as soon as a predetermined revolution 
speed is exceeded. As a consequence, the rope 16 also decreases its speed 
relative to the lifting unit 3 and the lever 17 is pivoted upwardly in the 
direction of arrow P' in FIG. 2. The lever 17' on the other side of the 
lifting unit 3 being rigidly coupled with the lever 17 by means of the 
connecting rod 9, it will also be pivoted in a clockwise direction, so 
that both wedges 10 are displaced upwardly and come into contact with the 
shoulders 32 of the head 33 of the rails 2. The lifting unit 3 is thereby 
braked in a progressive manner, as the cup springs 20 and 21 are more and 
more compressed while the braking wedges 10 are displaced upwardly. Thus, 
the braking of the lifting unit begins gently and gets progressively 
stronger as the wedge 10 is drawn upwardly and the cup springs 20 and 21 
are compressed. 
Simultaneously, a wear strip 25 arranged on the protruding portion 27' of 
the counterpart 27 is pressed against the right shoulder 32' of the head 
33 of the rail 2, as the counterpart 27 is displaced against the force of 
the springs 20 to the support member 34. Preferably, the surface of the 
wedge 10 which contacts the shoulder 32 is roughened. 
The desired braking effect can be selected by the number and the 
characteristics of the cup springs 20 and 21 and by tightening and loosing 
the nuts 18'. 
As can be seen in FIG. 5, the connecting rod 9 comprises a control disc 23 
rotating with the rod 9 and cooperating with a limit switch 28, which is 
activated as soon as a preselectable position of the lever 17 is reached. 
Thereby the drive of the lifting unit 3 is switched off. 
In most cases, the emergency brake can easily be released by reversing the 
drive 6 for the lifting unit 3. Thereby the centrifugal governor 8 
releases the pulley 14 which now can freely rotate and the rope 16 is 
displaced in the direction of arrow P" until the lever 17 abutes against a 
stop edge 29. If it should happen that the braking wedge 10 is so heavily 
blocked that it cannot be pushed out, the brake can be released by 
loosening the nuts 18' on the bolts 18 so that the cup springs 20 and 21 
become free moving and are somewhat decompressed. 
In order to monitor the tension of the rope 16, there is provided a limit 
switch 31 below the tension slide 30. If the rope 16 is flabby or broken, 
the slide 30 will be displaced downwardly and activate the limit switch 
31, which then will activate an alarm signal or switch the drive of the 
lifting unit 3 off. 
The apparatus according to the present invention has the important 
advantage, that the lifting unit can be stopped within an exactly defined 
braking path by selecting the number and the characteristics of the cup 
springs, whereby the braking is progressive, i.e. it begins gently and 
gets stronger. All parts of the construction can be made lighter but there 
remains nevertheless enough braking power. If passengers are on the 
lifting unit, any injuries can be avoided as the deceleration forces can 
be calculated in advance. A further advantage lies in the fact that no 
damage or wear of the guiding rails can occur, especially if the wedges 
are guided by bronze rods 24 and coacting wear strip 25 as explained 
before.