Apparatus for preventing unintended movement of elevator car

Apparatus for restricting motion of an elevator car includes bars or other stiff, elongated members, which are extended outwardly from opposing ends of the elevator car, when the car is positioned in a specified zone of vertical displacement, above the lower edge thereof The displacement zone may be on the order of twelve inches. An elevator control, such as an inspection bank mounted on top of the elevator car, is then operated to move the elevator car slightly downward, to the lower edge of the displacement zone, whereupon the elongated members are brought into solid contact with respective complementary supporting members, joined to opposing elevator guide rails. As the elongated members are extended, a switching arrangement, electrically coupled to the control, is simultaneously actuated to prevent movement of the elevator car above the displacement zone while the elongated members are in their extended mode.

BACKGROUND OF THE INVENTION 
The invention disclosed and claimed herein generally pertains to apparatus 
for preventing unintended downward or upward movement of an elevator car 
or platform. More particularly, the invention pertains to apparatus of 
such type which can be readily actuated, when desired, to hold the 
elevator car at a substantially fixed level. Even more particularly, the 
invention pertains to apparatus of such type which is comparatively simple 
and inexpensive, and can be readily adapted for use with existing 
elevators and elevator controls. 
It is anticipated that the invention will be particularly useful in 
connection with the class of elevators known commercially as hydraulic 
elevators, although the invention is by no means limited thereto. As is 
well known in the art, elevators of such type are raised and lowered by 
means of a hydraulic lift and/or power system which includes a piston and 
cylinder arrangement, and further includes hydraulic lines, valves, 
couplings, and fluid. 
In the operation and use of a hydraulic elevator, it is frequently 
necessary to position the elevator car at some level above the bottom of 
the elevator shaft or "pit". This may be required, for example, to enable 
a worker to perform inspection, maintenance, or other tasks. If it is 
anticipated that the task will not require disassembly of the hydraulic 
power system, it is common practice to rely on such power to maintain the 
car at the raised level. However, such practice can be very hazardous. If 
a worker in the pit inadvertently trips over or otherwise ruptures a 
hydraulic line or other hydraulic system component, allowing the hydraulic 
fluid to rapidly escape, the elevator car will free fall. This is 
extremely dangerous, and serious and even fatal injuries have resulted 
therefrom. 
Other work tasks routinely performed in a hydraulic elevator pit require 
disassembly of components of the hydraulic power system, so that fluid is 
necessarily released therefrom. Such tasks include, without limitation, 
packing replacement, fluid line repair and any other work that involves 
disconnecting the piston from the bottom of the elevator. Since tasks of 
this type require disablement of the hydraulic power systems, they cannot 
be performed until an elevator support structure has been constructed, in 
order to provide independent support for the elevator car. Such structures 
typically extend upwardly from the floor of the elevator shaft, and are 
formed of pipe stands or hardwood timbers. It is essential that these 
structures be properly and reliably constructed. Accordingly, substantial 
amounts of time, effort and care may be required therefor. Moreover, in 
such arrangements the space between the shaft floor and the bottom of the 
elevator car is generally limited by the maximum height of the elevator 
support structure. A further hazard may be created thereby, if the volume 
of the hydraulic fluid used in connection with the elevator is larger than 
the space beneath the elevator car. Under certain circumstances, an 
inadvertent break or rupture of the hydraulic fluid line can cause the 
space to rapidly fill with fluid. In the past, accidents of this type have 
created life-threatening situations for workers trapped in the pit. 
SUMMARY OF THE INVENTION 
The invention generally comprises means for selectively locking an elevator 
car against downward motion below a specified level, in combination with 
means for restricting upward travel of the car, from the specified level, 
to a very limited zone or range which may be on the order of inches. The 
invention further includes means for actuating the locking means and 
upward travel restricting means simultaneously, or in other coordinated 
relationship. 
In a preferred embodiment, wherein the elevator car is positioned for 
movement with respect to a stationary guide rail system, and an electric 
circuit is provided for enabling an operator to control elevator car 
movement from the top of the car, the locking means includes bars or the 
like which are extendible outward from opposing ends of the underside of 
the car to engage complementary means located along the guide rail system. 
The travel restricting means comprises means for interrupting the electric 
control circuit to prevent the car from rising above the zone. 
OBJECTS OF THE INVENTION 
An object of the invention is to provide improved apparatus for selectively 
preventing an elevator car or other movable component from descending 
below a specified level along its vertical path of travel, for safety or 
other reasons. 
Another object, is to provide apparatus of the above type, wherein the 
specified level can be located at virtually any desired position along the 
elevator path of travel. 
Another object is to provide apparatus of the above type which additionally 
is able to limit displacement of the elevator car above the specified 
level to a very small zone, which may be on the order of inches. 
Another object is to provide apparatus of the above type which can be 
quickly and easily actuated or released. 
Another object is to provide apparatus of the above type which is 
comparatively simple and inexpensive. 
Another object is to provide apparatus of the above type which can be 
readily installed for use with an existing elevator system, and is 
especially useful in connection with hydraulic elevators, although not 
limited thereto.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIG. 1, there is shown a conventional hydraulic elevator 10 
generally comprising a car sling 11, mounted for vertical movement along 
stationary, vertically oriented guide rails such as 30a and 30b. Hydraulic 
elevator 10 further comprises a floor or supporting platform 12, and sling 
11 comprises side stiles 11a and 11b, a pair of top cross head members 11c 
and 11d, and a pair of bottom bolster channels 11e and 11f, which carry 
floor 12. The sling 11, floor 12 and sheet metal shrouding (not shown) are 
principal components of the vertically movable structure referred to 
herein as the elevator car. The shrouding is carried by the sling 11 and 
floor 12, and is positioned therearound to form a passenger enclosure, 
which is accessible through a door 15. It is to be understood that none of 
the drawings show the elevator passenger enclosure, which was 
intentionally left out in order to clearly show critical or essential 
elevator components and the embodiment of the invention. Roller guide 
assemblies, slide guide assemblies, or the like 13a and 13b, as best shown 
in FIGS. 2 and 3 respectively, are mounted to the top and bottom of car 
sling 11, i.e. to the top cross head members 11c and 11d and to the bottom 
bolster channels 11e and 11f, respectively, and engage guide rails 30a and 
30b. The car sling 11 is thereby constrained to a vertical path of travel. 
The floor 12 is not shown in figures other than FIG. 1, to enhance 
illustration. 
FIG. 1 further shows a hydraulic lift system 31 including a hydraulic 
cylinder or cylinders 32 positioned in floor 21 at the base or bottom of 
elevator shaft 20, each cylinder receiving a hydraulic piston 32a which 
acts against the bottom of car sling 11. Hydraulic fluid is moved into or 
out of cylinder 32 through a hydraulic line 32b as required, to drive 
piston 32 and car sling 11 upward or downward. Other components of a 
hydraulic lift system 31 for elevator 10, such as a pump and motor or 
other hydraulic actuator (not shown) are generally located in an adjoining 
machine control room (not shown). 
It is to be understood that both the hydraulic elevator 10 and the 
hydraulic system 31, as depicted in FIGS. 1-3, are well known in the art. 
Hydraulic elevator 10, in normal mode of operation, is controlled by an 
operator within the car, but not from a position on top of the car and 
sling 11. However, as further described hereinafter, certain inspection 
and other tasks must be performed by an operator positioned on top of the 
elevator car. Accordingly, a local elevator control 50, known in the art 
as an inspection control bank and described hereafter in connection with 
FIGS. 6 and 7, is placed on the elevator car top and is generally mounted 
to either of the cross head members 11c or 11d. 
Referring to FIG. 4, there is shown a mechanism 60, comprising an 
arrangement of mechanical components, and further comprising a portion of 
the embodiment of the invention. Mechanism 60 includes a bar 61, which is 
securely joined to a rod 61b at its rightward end with a pin 61a, as 
viewed in FIG. 1. Bar 61 and rod 61b are mounted to bolster channel 11e by 
means of a horizontal guidance system comprised of brackets or other 
supporting members 61c, so that bar 61 and rod 61b can reciprocate in 
unison with respect to bolster channel 11e, in the directions indicated by 
double headed arrow A. 
FIG. 4 further shows the end of rod 61b opposite bar 61 tied to a pivoting 
member 62, such as by means of a pin 62a. Member 62 is mounted for pivotal 
or rotational movement by means of a shaft 62b. Shaft 62b is of such 
length that it passes through both bolster channels 11e and 11f and 
extends outward from the side thereof opposite to the side shown in FIG. 
4. It is to be understood that pivoting member 62 is fixed to shaft 62b, 
so that rotation of member 62 causes shaft 62b to rotate in unison. Shaft 
62b may be supported for such movement by extending it through a hole 
formed in bolster channels 11e and 11f having a diameter which is slightly 
larger than the shaft 62b diameter. Alternatively, shaft 62b could be 
supported for rotation by bearings (not shown). Member 62 can pivot 
clockwise or counterclockwise, as shown in FIG. 4, by double-headed arrow 
B. An end of a rod 63 is also joined to pivoting member 62 by pin 63a, and 
the opposing end of rod 63 is joined to a second pivoting member 64, by a 
pin 64a. 
Member 64 can pivot around pin 64b, as shown by double headed arrow C. The 
lower end of a lift rod 65 is joined to pivoting member 64 by a pin 65a. 
The lower portion of lift rod 65 is shown in FIG. 4 and the upper portion 
thereof is shown in FIGS. 2 and 5. FIG. 5 shows a cam 67 joined to the 
upper portion of rod 65, and vertically movable therewith, to respectively 
engage switch elements 67a and 67b, of respective micro switches 68a and 
68b, when rod 65 is moved along its vertical path of travel. More 
particularly, switch elements 67a and 67b are operated to turn switches 
68a and 68b off when rod 65 and cam 67 are moved upwardly, and to turn 
switches 68a and 68b on when rod 65 and cam 67 are moved downwardly. 
Switches 68a and 68b are respectively connected to inspection bank 50 
through electrical leads 69a, 69b, 69c and 69d, and are provided to 
interact with inspection bank 50 as described hereinafter in connection 
with FIG. 7. Switches 68a and 68b are usefully contained in a housing 70, 
as viewed in FIG. 2. Leads 69a-d are shown schematically in FIG. 7, and 
are collectively included in cable 69e, shown in FIG. 2, which extends 
between housing 70 and inspection bank 50. 
Cam 67 and switches 68a and 68b are mounted upon a mounting plate 58, 
attached to side stile 11a of sling 11. Housing 70, containing the 
switches, is mounted upon plate 58 on side 58a thereof, as shown by FIG. 
2. FIG. 5 shows cam 67 mounted on the opposing side of plate 58, i.e., 
side 58b thereof. The switch elements 67a and 67b extend through an 
aperture 58c formed through the mounting plate, for engagement with the 
cam 67. 
Referring further to FIG. 5, there is shown a magnetic switch 71 mounted on 
side 58b of plate 58, next to cam 67. Face 71a of switch 71 extends 
outwardly from plate 58. Magnetic switch 71 is generally open or in an 
open mode as it moves with car sling 11 along the vertical path of travel 
thereof However, to close switch 71, a sheet of conductive material, such 
as a steel plate 72, is joined to guide rail 30b at a selected vertical 
level. More specifically, conductive plate 72 is positioned so that face 
71a of magnetic switch 71 may move into very close proximity with plate 
72. When the point P shown on face 71a is within a zone Z defined by the 
position of plate 72, the plate 72 and certain operative components in 
switch 71 (not shown) will be closely spaced apart, causing switch 71 to 
close. The zone Z usefully has a length on the order of twelve inches. 
Magnetic switch 71, which is well known in the art, is likewise connected 
to inspection bank 50, through electrically conductive leads 69a and 69d, 
thus effectively placing the magnetic switch in parallel with the micro 
switch 68b, and interacting with inspection bank 50 as described 
hereinafter in connection with FIG. 7. 
By suitable design, point P on switch 71 will be at the lower end of zone Z 
when the lower edge of bar 61 is at the lower end of a zone Z', which is 
equal in length to the zone Z. Thus, conductive plate 72 is joined to 
guide rail 30b so that plate 72 causes switch 71 to close only when the 
elevator car is positioned so that bar 61 is within the zone Z'. 
Otherwise, the switch 71 will be open. As shown in FIG. 4 and described 
hereinafter, the lower edge of the zone Z'coincides with the upper edge of 
a steel plate 80 bolted to guide rail 30a. 
Vertical movement of rod 65, in addition to operating micro switches 68a 
and 68b shown in FIG. 5, serves to operate the mechanism 60 shown in FIG. 
4 and including rods 61b, 63, and 65, bar 61 and pivoting members 62 and 
64. As shown in FIG. 5, rod 65 passes through guides 66a and 66b, 
respectively attached to the top and bottom of plate 58, which constrain 
rod 65 to vertical movement. 
When a force is applied to move rod 65 upward, member 64 is pivoted in a 
counterclockwise direction, causing rod 63 to move rightwardly, as viewed 
in FIG. 4. Member 62 is thereby pivoted in a counter-clockwise direction, 
so that rod 61b and bar 61 are moved leftward, to an extended position. 
Extending bar 61 and rod 61b compresses spring 73 positioned around rod 
61b, wherein one end of spring 73 is constrained by a pin or locking 
device 73a, which is attached to rod 61b, and the other end of spring 73 
is constrained by a bracket 73b, which has a guide hole for rod 61b, and 
is attached securely to bolster channel 11e. Additionally, upward movement 
of rod 65 compresses a spring 75, positioned around rod 65, as viewed in 
FIG. 5. Spring 75 is constrained on one end by a pin or locking device 
75a, attached to rod 65, and the opposing end is constrained by lower 
guide 66b. In a useful embodiment, rod 65 is moved upwardly manually, as 
indicated in FIG. 5 by arrow E. To maintain the bar 61 in its extended 
position, a pin 74 is thrust through a hole 74a in the end of rod 65, 
after the hole 74a has been moved above top guide 66a, to place the rod 65 
in its upward position. The pin 74 then acts against the guide 66a to hold 
rod 65 upwardly. Both springs 73 and 75 act to release the mechanism 60 
from its activated position, and thereby cause bar 61 to move rightward to 
its retracted position, upon removal of pin 74 from hole 74a. 
Referring further to FIG. 4, there is shown bar 61 extending beyond the 
adjacent guide rail 30a. There is further shown a plate 80, of very heavy 
steel stock, solidly joined to the guide rail 30a such as by means of 
bolts 81. Plate 80 is attached to the guide rail 30a so that the upper 
edge 80a of the plate coincides with the lower edge of the zone Z'. 
Moreover, the plate 80 is of such dimension that the side edge 80b of the 
plate 80 extends beyond guide rail 30a such that it lies in the vertical 
path of the bar 61 in its extended position. Thus, when bar 61 is located 
above plate 80 and is in its extended position, elevator car sling 11 can 
only descend until bar 61 is brought into contact with the upper edge 80a 
of plate 80. Accordingly, bar 61 acts to prevent the bottom of car sling 
11 from descending below a selected level, determined by the location at 
which plate 80 is attached to guide rail 30a. 
Referring again to FIG. 4, there is shown a mechanical arrangement 90, 
which comprises a further component of the embodiment of the invention. 
Arrangement 90 generally includes a pivoting member 91, a rod 92 having an 
end joined to member 91 by means of a pin 91a, and a bar 93 securely 
joined by means of a pin 92a to the opposite end of rod 92. Bar 93 is 
similar or identical to bar 61, and bar 93 and rod 92 are mounted to 
bolster channel 11f by means of brackets or the like 93a, which are 
similar or identical to brackets 61c. Thus bar 93 and rod 92 can 
reciprocate in unison with respect to bolster channel 11f, in the 
directions indicated by the double-headed arrow F, in response to pivoting 
movement of member 91. 
Referring further to FIG. 5, there is shown pivoting member 91 joined to 
the shaft 62b, and rotatable therewith in clockwise and counterclockwise 
directions, as indicated by double-headed arrow G. Thus, mechanical 
arrangement 90 is configured so that as rod 65 is moved upward to extend 
bar 61 outward, past guide rail 30a, rotational power is simultaneously 
transferred through pivoting member 62, shaft 62b, and pivoting member 91. 
Such rotational power acts to extend bar 93 outward, in a direction that 
is opposite that of the bar 61 movement and past the guide rail 30b. A 
steel plate 94, similar or identical to plate 80, is joined to guide rail 
30b, that is, so that it lies in the vertical path of the bar 93 in its 
extended position. Plate 94 and bar 93 are respectively positioned so that 
when both bars 61 and 93 are extended outward, and car sling 11 is 
descending, the lower edges of the bars will simultaneously contact the 
upper edges 80a and 94a of their respective plates 80 and 94. Elevator car 
sling 11 will thereby be firmly held in position, and prevented from 
descending below the selected level. 
It will be readily apparent that when rod 65 is moved downward, the bars 61 
and 93 will simultaneously be retracted, that is, moved rightward and 
leftward, respectively, as viewed in FIG. 4. Referring once again to FIG. 
5, such action may be simply achieved by removing pin 74. As springs 73 
and 75 expand from their compressed positions, as described above, in 
addition to retracting bar 61, rotational power is delivered through shaft 
62b and pivoting member 91, to draw bar 93 into its retracted position. 
While not shown, the retracted positions of bars 61 and 93 are 
respectively selected so that, when retracted, the bars will not interfere 
with the free vertical travel of elevator car sling 11. 
Referring to FIG. 6, there is shown car top inspection bank 50, comprising 
a conventional set of controls for enabling an operator to locally control 
elevator movements from a position on the top of the car sling 11. 
Inspection bank 50 is connected to an elevator control system 96, 
comprising a network of control relays or other elements, such as are well 
known in the art. The control system may be located in the machine control 
room. Inspection bank 50 includes a mode selection switch 51, for 
selecting either inspection or automatic mode of elevator operation. When 
the selection switch 51 is moved to the inspection mode of operation, 
electrical current is transferred from line 101 to line 102. In response, 
the elevator control 96 eliminates power from line 100, effectively 
disabling the up button 51a, down button 51b and safe button 51c of 
inspection bank 50. However, when the switch 51 is moved to the inspection 
mode of operation, electrical current is removed from line 102, whereby 
the elevator control room 96 transfers power to line 100. This now allows 
elevator control by means of inspection bank 50, by use of the buttons 
51a, 51b, and 51c. The inspection bank allows elevator operation from a 
position on top of the car, to perform tasks such as elevator maintenance, 
inspections, or cleaning. Such operation typically requires the use of two 
hands, for safety reasons. The possibility of accidental movement of the 
elevator, for example, resulting from an object inadvertently depressing a 
single button, is thereby greatly reduced. Accordingly, to transfer 
electrical current from line 100 to either the up button 51a or the down 
button 51b, the safe button 51c must first be depressed with one hand. A 
second hand must then depress either the up button 51a, or the down button 
51b, in order to close a circuit to transfer the current from line 100 
back to the elevator control system 96, and thereby move the elevator car 
upward or downward. 
Referring to FIG. 7, there is shown a switching arrangement 110, comprising 
the micro switches 68a and 68b and magnetic switch 71 described above, 
interconnected to inspection bank 50. Such connections may be made with 
comparative ease, by means of electrical leads 69a, 69b, 69c, and 69d, 
respectively. More particularly, switch 68a is coupled in series with the 
mode selection switch 51, and switch 68b is coupled in series with safe 
button 51c. Magnetic switch 71 is coupled in parallel with micro switch 
68b. 
The embodiment of the invention described above generally comprises 
mechanical arrangements 60 and 90, and switching arrangement 110. The 
operation of the embodiment, comprising an elevator motion restraining 
device, may now be readily understood. When rod 65 is in a downward 
position, bars 61 and 93 are retracted and switches 68a and 68b are both 
closed. Accordingly, the restraining device does not affect the normal 
elevator movement or the conventional controls thereof, including 
inspection bank 50. 
When it is desired to activate the motion restraining device of the 
invention, in order to lock the elevator in place at the selected level, 
an operator on top of the elevator operates switch 51 to select the 
inspection mode of operation. Controls 51a, 51b, and 51c are then employed 
to move the elevator car sling 11 to an actuation position, that is, so 
that the bar 61 is within the vertical zone Z'. In such position, the 
lower edges of the bars 61 and 93 will be above the upper edges of steel 
plates 80 and 94, respectively. However, the clearance therebetween will 
be no greater than the zone Z' dimension. Accordingly, magnetic switch 71 
will be within zone Z, so that switch 71 will be in its closed state. For 
the convenience of the operator, respective marks may be placed on the car 
sling 11 and on either guide rail, 30a or 30b, which will be in alignment 
when the car is in such actuation position. 
After such position has been reached, the operator moves rod 65 upward. 
Bars 61 and 93 are thereby extended outward, as described above, and 
switches 68a and 68b are opened. However, even though switch 68b is now 
open, magnetic switch 71 is closed. Accordingly, line 69d remains active, 
and the down control button 51b can be operated in conjunction with safe 
button 51c, to lower the elevator by the slight amount required to bring 
the bars 61 and 93 into rigid engagement with plates 80 and 94, 
respectively. Elevator car sling 11 will thereby be prevented from further 
downward motion, even if the associated hydraulic system should fail. 
With the motion restraining device of the invention activated, as described 
above, the elevator car will be prevented from rising by more than a 
displacement equal to the zone Z. For example, if the up button 51a and 
the safe button 51c are inadvertently operated while the bars 61 and 93 
are supported by respective plates 80 and 94, point P on magnetic switch 
71 will move out of zone Z after the elevator car has traveled the 
distance Z. Magnetic switch contact 71 will thereupon open, deactivating 
the up button 51a and preventing any further upward movement of the car 
sling 11. This prevents possible accidents, and damage to structure in the 
elevator shaft which would encounter the outwardly extending bars, if they 
moved upward a significant distance. Obviously, numerous modifications and 
variations of the present invention are possible in light of the above 
teachings. It is therefore to be understood that within the scope of the 
disclosed concept, the invention may be practiced otherwise than as 
specifically described.