Terminal slowdown apparatus for elevator

A terminal slowdown apparatus for an elevator comprises an acceleration detecting circuit which detects an acceleration in the normal speed pattern or an acceleration of the cage; a relative speed pattern generator which generates a relative speed pattern depending upon the output of the acceleration detecting circuit and the position of the cage and a comparator which is actuated when the normal speed pattern or the cage speed is higher than the relative speed pattern whereby the normal speed pattern is switched to the terminal slowdown speed pattern by the operation of the comparator.

BACKGROUND OF THE INVENTION 
The present invention relates to an improved terminal slowdown apparatus 
for an elevator. 
In an elevator, the speed of a cage near the terminal floors is monitored 
and if an excessive speed is detected, it is necessary to safely land the 
cage. 
As is well known, speed control of the cage is performed depending upon the 
speed pattern. The elevator has the structure for forming a terminal 
slowdown speed pattern which is different from the normal speed pattern, 
when the cage is near the terminal floors. 
The terminal slowdown speed pattern is formed by contacting the cage with a 
landing floor selected in a machine room or a plurality of switches 
disposed near the terminal floors in a hoistway. 
The relations are shown in FIGS. 1 and 2. 
In FIG. 1, the reference .sub.ABC shows the normal speed pattern of the 
cage (not shown) in landing at the terminal floor (C) after being driven 
at a constant speed. The speed of the cage is normally controlled 
depending upon the normal speed pattern. 
The reference .sub.DEC designates the lower floor landing speed pattern. If 
an error occurs in the normal speed pattern .sub.ABC to cause the pattern 
.sub.ABE , the speed pattern is switched to the terminal slowdown speed 
pattern to give .sub.ABEC . 
The cage is controlled along the speed pattern .sub.ABEC whereby the speed 
of the cage is changed as shown by the broken line and the cage is safely 
stopped at the terminal floor (C). 
However, when a deceleration is caused before reaching the specific speed, 
(hereinafter referring to as a short landing operation), the normal speed 
pattern is given by the reference .sub.ABC in FIG. 2. 
If the error in the normal speed pattern occurs during an acceleration of 
the cage, the speed pattern is varied to the speed pattern .sub.A'B'E'C 
and the speed of the cage is changed so as to be shown by the broken line. 
As it is clear from the drawings, the acceleration of the cage is 
significantly large in the negative direction and the sudden deceleration 
causes a shock to the passengers in the cage to provide an insecure 
feeling. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to overcome the abovementioned 
disadvantages and to provide a terminal slowdown apparatus which safely 
lands a cage without any insecure feeling even though the normal speed 
pattern is switched to the terminal slowdown speed pattern during an 
acceleration of the cage. 
The foregoing and other objects of the present invention have been attained 
by providing a terminal slowdown apparatus for an elevator by switching 
the normal speed pattern to a terminal slowdown speed pattern whenever the 
normal speed pattern causes over the terminal slowdown speed pattern near 
the terminal floors which comprises an acceleration detecting circuit 
which detects an acceleration in the normal speed pattern or an 
acceleration of the cage; a relative speed pattern generator which forms a 
relative speed pattern depending upon the output of the acceleration 
detecting circuit and the position of the cage; and a comparator which is 
actuated when the normal speed pattern or the cage speed is higher than 
the relative speed pattern; whereby the normal speed pattern is switched 
to the terminal slowdown speed pattern by the operation of the comparator.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to FIGS. 3 and 4, one embodiment of the present invention will be 
illustrated. 
In FIG. 3, the reference (1) designates a normal speed pattern generator 
which generates normal speed patterns (1a), (1b); (2) designates a 
differentiator; (3) designates an acceleration function generator for 
generating a constant output (3a) during an acceleration of the cage; (4) 
designates a terminal slowdown speed pattern generator which generates the 
terminal slowdown speed pattern (4a); (5) designates an subtractor; (5a) 
designates an output of the subtractor as the relative speed pattern; (6) 
designates a comparator; (7) designates a fall distance adjuster; (8) 
designates a switch and (8a) designates an output as a speed pattern. 
The normal speed pattern (1a) is given in the long landing operation and 
the normal speed pattern (1b) is given in the short landing operation. 
The reference (9) designates a diode; (10) designates a comparator; (11) 
designates a flip-flop; (12) designates a subtractor; (13) designates a 
switch; (14) designates a capacitor; (15) designates a resistor; (16) 
designates a subtractor. 
In the normal speed pattern generator, the normal speed pattern can be the 
same with the output SRAT of the speed pattern generator (48) under the 
OFF state of the analog switch (560) in U.S. Pat. No. 3,750,850. 
In the terminal slowdown speed pattern generator, the terminal slowdown 
speed pattern can be the same with the output TSAN of the terminal 
slowdown (558) in the speed pattern generator (48) in U.S. Pat. No. 
3,750,850. 
The differentiator (2) outputs a value being proportional to an 
acceleration of the speed pattern (1a). 
The acceleration function generator (3) outputs a positive specific value 
when the output of the differentiator is negative but the absolute value 
of the output is larger than the reference value A.sub.r whereas it 
outputs about zero volts because of the diode (9) when the output is 
positive or smaller in negative value than the reference value A.sub.r. 
The relative speed pattern (5a) is output from the subtractor (5) of the 
circuit for subtracting the output (3a) of the acceleration function 
generator from the terminal slowdown speed pattern (4a). 
The comparator (10) compares the normal speed pattern (1a) with the 
relative speed pattern (5a). When the normal speed pattern (1a) is larger 
than the relative speed pattern (5a), the low signal is input to the SET 
terminal of the flip-flop (11) to form high signal for the output Q of the 
flip-flop. 
The fall distance adjuster (7) includes a subtractor (12) which outputs the 
difference between the normal speed pattern and the terminal slowdown 
pattern. The switch (13) is in the ON state when the output Q of the 
comparator is low whereby the potential of the capacitor (14) is the same 
with the output of the subtractor (12). 
The switch (13) is in the OFF state when the output Q of the comparator is 
high, and the capacitor is discharged through the resistor (15). The 
subtractor (16) subtracts the voltage of the capacitor from the terminal 
slowdown pattern to form the modified terminal slowdown pattern (7a). 
The switch (8) selects the normal speed pattern when the output Q of the 
comparator (6) is low and selects the modified terminal slowdown pattern 
when the output Q of the comparator (6) is high. 
In FIG. 4, the reference (1aA) designates the acceleration in the normal 
speed pattern (1a); (1bA) designates the acceleration in the normal speed 
pattern (1b); and (1bB) designates a command for reducing the acceleration 
in the short landing operation. 
That is, in the normal speed pattern (1b) for the short landing operation, 
the decrease of the acceleration is commanded at the point X.sub.0 to give 
zero acceleration at the point X.sub.1, and at the point X.sub.2, the 
normal speed pattern (1b) corresponds to the normal speed pattern (1a) for 
the long landing operation. 
When the value of the normal speed pattern (1a) is given as V.sub.1a and 
the value of the terminal slowdown speed pattern (4a) is given as 
V.sub.4a, the value V.sub.5a of the relative speed pattern (5a) in the 
case of the normal speed pattern (1a) of V.sub.1b is preferably selected 
by the equation: 
EQU V.sub.5a =V.sub.4a -[V.sub.1a -V.sub.1b ] (1) 
The second term of the right side of the equation (1) V.sub.1a -V.sub.1b 
can be shown as the function F(.alpha.) for the acceleration .alpha. of 
the speed pattern. 
That is, the equation can be modified as the equation: 
EQU V.sub.5a =V.sub.4a -F(.alpha.) (2) 
In the following embodiment, the output (3a) of the acceleration function 
device (3) which forms a constant value during the acceleration is used 
instead of the function F(.alpha.) in the equation (2) so as to simply 
describe the embodiment. 
Thus, when the cage approaches to the terminal floor (C) in a deceleration 
in the long landing operation, the output (3a) of the acceleration 
function device is zero even though the differentiator (2) generates the 
output. Accordingly, the speed pattern (5a) is the same with the speed 
pattern (4a). 
The speed pattern (1a) and the speed pattern (4a) are compared by the 
comparator (6). The cage is controlled along the pattern (1a) in the case 
of pattern (1a)&lt;pattern (4a) whereas the speed pattern of the apparatus is 
switched to the speed pattern (4a) in the case of pattern (1a)&gt;pattern 
(4a), as described above. 
When the cage is started from the point A' to perform the short landing 
operation, the acceleration function device (3) generates a specific 
output (3a) in the acceleration. Accordingly, the relative speed pattern 
(5a) as the output of the subtractor (5) is the pattern given by 
subtracting the output (3a) from the pattern (4a) and this is V.sub.5a 
shown by the equation (2). 
The speed pattern (1b) and the relative speed pattern (5a) are compared by 
the comparator (6), and the cage is controlled along the speed pattern 
(1b) during the condition of pattern (1b)&lt;pattern (5a). When it is changed 
to the condition of pattern (1b)&gt;pattern (5a) at point, F the comparator 
(6) generates the output and the switch (8) is actuated and the speed 
pattern (4a) is switched to the speed pattern (8a) through the fall 
distance adjuster (7) and the cage is controlled along the speed pattern 
(8a). 
The fall distance adjuster (7) has the function for smoothing the speed 
pattern by adjusting the speed pattern fall when the normal speed pattern 
(1b) is switched to the terminal slowdown speed pattern (4a). 
As it is clearly understood by the drawings, point F is nearer than point 
E', whereby the cage is landed at the terminal floor (C) without rapid 
deceleration to cause an insecure feeling. 
In said embodiment, the normal speed patterns (1a), (1b) are used for 
detecting the acceleration. It is also possible to use a differential 
value of the output of a tachometer dynamo (not shown) for indicating the 
speed of the cage or to use an acceleration reducing command (1bB). 
It is also possible to substitute the normal speed patterns (1a), (1b) as 
one of the inputs of the comparator (6) with the speed signal for 
indicating the speed of the cage. 
In said embodiment, the acceleration function device (3) is used for 
F(.alpha.) in the equation (2). 
Thus, it is clear to give superior driving for the terminal slowdown by 
using a function device for providing the function being closer to F 
(.alpha.) instead of the acceleration function device (3). 
As described above, in accordance with the present invention, the 
acceleration of the normal speed pattern or the acceleration of the cage 
is detected and the relative speed pattern is provided depending upon the 
detected acceleration and the position of the cage and the normal speed 
pattern is switched to the terminal slowdown speed pattern when the normal 
speed pattern or the speed of the cage becomes higher than the relative 
speed pattern, whereby the cage can be safely landed at the terminal 
without insecure feeling even though the terminal slowdown operation is 
started during the acceleration in the short landing operation.