Automatic emergency escape for tall structures

A device for safely lowering persons from upright structures such as buildings during an emergency at a safe, predetermined speed of no more than about four feet per second irrespective of the weight of the person being lowered. The device has a drum about which a cable is wound, a gear pump driven by the drum via a reduction gear train, and a hydraulic circuit which includes the gear pump and a flow control valve which maintains a constant hydraulic fluid flow through the circuit irrespective of the weight of the person being lowered and, therefore, also irrespective of the fluid pressure generated by the pump during operation. The hydraulic circuit is in fluid communication with a hydraulic fluid tank having an exterior surface dimensioned to cool the hydraulic fluid and prevent its temperature from rising by more than about 200.degree. F. above the ambient temperature during operation of the device. A handle can be used for manually rewinding the cable about the drum, and the hydraulic circuit includes a one-way branch line, controlled with a check valve, to permit countercurrent circulation of hydraulic fluid during the rewinding of the cable. The gear train causes the gear pump to rotate at a substantially higher rate of rotation than that of the drum to facilitate the control of the fluid flow in the hydraulic circuit. The increase in fluid volume results in improved flow control in the flow control valve.

BACKGROUND OF THE INVENTION 
During emergencies, typically fires, it becomes often necessary to rapidly 
evacuate persons from the affected structure such as a highrise building 
(hereinafter simply referred to as "building"). This can become difficult, 
dangerous and impossible if access to the internal fire escapes is 
blocked; for example, by flames and smoke. In such cases the only 
available escape route may be along the exterior of the building, but 
ordinarily that route is, under the best of circumstances, available to 
only the occupants of the lowest floor or floors of the building. 
While floors at intermediate heights of the building could be evacuated via 
ladders, provided they are available at all, occupants of the higher 
floors are in great danger unless the fire can be controlled in time 
before it reaches and/or spreads throughout such floors. 
Thus, attempts have been made in the past to provide occupants of buildings 
with a way to escape along the exterior of the building during 
emergencies. Typically, this involved providing a rope or cable that is 
suitably anchored to the building, a mechanism frictionally engaging the 
rope and adapted to suspend the escaping person therefrom, and means 
operable by the escaping person for controlling friction to thereby lower 
himself at a controlled, sufficiently low speed to prevent injury upon the 
person's arrival on the ground. Exemplary of prior art efforts for 
escaping along the exterior of buildings are U.S. Pat. Nos. 5,145,036; 
4,934,484; 4,705,142; 4,679,654; 1,190,389; and 702,858. 
The prior art devices have a number of drawbacks, including their reliance 
on power from the person descending to slow the rate of descent, their 
need for some skill on the part of the descending person to properly 
operate it, and their inability for an efficient and quick reuse by 
several persons requiring evacuation because the devices are typically 
limited for use by one person only. They are therefore more suitable for 
individual escape mechanisms, adapted to be carried around by the intended 
user, but not well suited for permanent installation at various building 
sites as a standby to quickly evacuate several persons if and when an 
emergency arises. 
From operational and safety points of view, it would of course be preferred 
if buildings could be fitted with escape devices which, on demand, 
automatically lower a person at a safe, controlled speed along the 
exterior of buildings without relying on the strength, dexterity, skill 
or, indeed, consciousness of the person being lowered. Such devices could 
be powered by electric motors, and appropriate mechanical, 
electromechanical and/or electronic controls are available to operate the 
devices. The problem with this approach is that in emergencies it is 
possible, indeed it is to be expected, that no power is available. Hence, 
power-driven escape devices are not feasible because the likelihood that 
they will be inoperative is greatest at the very moment when they are 
needed. 
Accordingly, there is presently a need for a self-contained device which, 
without the need for external power and/or personal strength and skill, 
can lower persons during emergencies from the building to the surrounding 
ground at a controlled, safe speed at which injuries due to impact with 
the ground are prevented. 
SUMMARY OF THE INVENTION 
The present invention enables persons to escape buildings, even the 
uppermost floors of tall highrise buildings, during emergencies such as 
fires. This is achieved by using the energy of the person being lowered to 
drive the device and, without the need for external power and/or any 
controls, to further use the weight of the person to determine and control 
his or her rate of descent by maintaining it at a safe rate. In this 
manner, a person can escape from a building floor by simply attaching 
himself to the device, as is more fully described below, stepping outside 
the building, and then, as a result of no more than stepping outside the 
building and without assistance from anyone or any outside power, slowly 
descending to the ground. Once on the ground, the device can be reset to 
enable others to escape. 
A first aspect of the present invention involves a method for lowering a 
person along the upright exterior of a building by providing a cable of 
sufficient length to reach the surrounding ground, suspending the person 
from an end of the cable, and lowering the person while applying a braking 
force to the cable so that the person descends gravitationally downward at 
a predetermined, constant speed. In a presently preferred embodiment of 
the invention, this is a speed of about four feet per second. 
To maintain this speed, the braking force applied to the cable is 
controlled as a function of and solely in response to the suspended 
person's weight by unwinding the cable from a drum and braking the cable 
speed with a gear pump. The latter is in a hydraulic circuit which 
includes a flow control valve that keeps the rate of flow in the circuit 
constant irrespective of the weight of the descending person. 
As a result, and as briefly indicated above, the act of becoming suspended 
from the free cable end not only automatically generates a braking force, 
by virtue of a gear pump driven by the cable drum, but further 
automatically adjusts this braking force to the actual weight of the 
suspended person so that his/her rate of descent will always be 
substantially the same irrespective of his/her weight. There is no need 
for the person to manipulate anything, indeed there is no need to commence 
or stop the operation of the emergency exit device of the present 
invention, because both are automatically initiated when the person steps 
out of the building to become suspended from the cable and again upon 
his/her arrival on the ground. Moreover, the device requires no outside 
power, so that power outages, frequently encountered during emergencies, 
have no effect. 
A second aspect of the present invention is directed to the construction of 
the emergency escape device. Generally speaking, such a device includes a 
support frame for permanent attachment; e.g. by way of bolts or welding, 
to the structure in the vicinity of an opening such as a window through 
which persons can escape in the event of an emergency. A drum is rotatably 
mounted to the frame and has a cable wound about its periphery, a free end 
of the cable being adapted to be attached to the person that is to be 
lowered to the ground. 
A gear pump includes a rotatable shaft that is located exteriorly of and 
proximate to the drum. A drive connection, such as a gear train or a chain 
drive, for example, couples the gear pump to the drum so that rotation of 
one causes rotation of the other one. The drive further preferably rotates 
the shaft of the gear pump at a substantially higher rate than that of the 
drum to facilitate the control of the pump, as is further discussed below. 
The hydraulic circuit communicates with a hydraulic fluid storage tank 
mounted to the frame. The circuit includes a flow control valve downstream 
of the pump for maintaining the hydraulic fluid flow rate in the circuit, 
and thereby through the pump, substantially constant irrespective of the 
fluid pressure generated by the pump. Since the hydraulic fluid is a 
noncompressible liquid, the constant fluid flow rate in the circuit 
results in a constant rate of rotation of the gear pump and therewith also 
of the drum. Thus, the speed at which cable is paid out from the drum does 
not change irrespective of the weight of the person suspended from the 
cable. 
In a presently preferred embodiment of the invention the flow control valve 
is of the type which has one or more orifices through which the hydraulic 
fluid flows, the effective open area of which changes in response and 
inversely to a change in the fluid pressure generated by the pump. Such 
gear pumps are commercially available as standard, off-the-shelf items. As 
such, the pumps are not only effective and efficient, they are also 
relatively inexpensive, thereby lowering the cost of the emergency exit 
device of the present invention. 
At present applicant prefers to use fixed displacement gear pumps available 
from the Parker Hannifin Corporation, Fluid Power Pump Division, of 
Otsego, Mich. 49078, and referred to as Series H pumps, which have a 
maximum pressure of 2500 psi (172 bar) and a maximum speed of 4000 rpm. 
This pump limits the generated maximum pressure to about 2500 psi, which 
is important to protect internal seals and is well below 4000 psi, a 
pressure which is so large that it is generally considered to be 
dangerous. When installed in the escape device of this invention as 
disclosed herein, the pump will generate a pressure of between about 260 
psi and 2080 psi when persons weighing between 50 lbs. and 400 lbs. are 
being lowered. 
The flow control valve in the hydraulic circuit is also preferably an 
off-the-shelf item to assure ready availability and relatively low cost. 
Applicant presently prefers to use pressure-compensated flow control 
valves available under the trademark MANATROL, Series PC, and available 
from Parker Fluid Power, Hydraulic Valve Division, of Elyria, Ohio 44035. 
Applicant presently prefers flow control valve Model PCK820S, which is 
particularly well adapted for use with the above-referenced, commercially 
available gear pump. 
The device of the present invention further preferably includes a handle, 
operatively coupled to the drum, for manually rotating the drum so that 
the cable can be retracted and rewound after a person has been lowered to 
the ground. Thus, rewinding too is accomplished without the need for 
power, which may not be available during the emergency. 
To facilitate rewinding, the hydraulic circuit includes a return branch 
line so that hydraulic fluid circulated by the pump while the cable is 
rewound can flow in the reverse direction from the tank, through the pump 
and back to the tank again. A check valve closes the return line when a 
person is lowered and hydraulic fluid circulates in the operative flow 
direction. 
It is desirable to minimize the amount of hydraulic fluid in the hydraulic 
circuit and the hydraulic tank to minimize the weight of the device and 
its size as well as to reduce costs. However, during descents the gear 
pump converts relatively large amounts of energy into heat, thereby 
heating the hydraulic fluid. To prevent a degradation of most hydraulic 
fluids, the fluid temperature should not exceed about 250.degree. F. 
Increasing the volume of the available hydraulic fluid in and of itself 
lowers its temperature during operation. To further assist in this regard, 
the fluid tank is constructed so that a portion thereof; e.g. its sides 
not attached to the frame, is exposed to the atmosphere and can act as 
heat exchange surfaces to cool the hydraulic fluid. The tank is preferably 
constructed so that its effective heat exchange surfaces (which are 
exposed to the atmosphere) prevent a fluid temperature rise of more than 
about 200.degree. F. after five consecutive descents of persons with a 
maximum design weight of about 400 lbs. 
In addition to the control of temperature, it is important to control the 
rate of fluid flow in the hydraulic circuit and, thereby, to the gear 
pump. At low rates of gear pump rotation, such control becomes more 
difficult and unreliable because the liquid flow rate through the pump 
and, more importantly, through the flow control valve can become too 
small. In such an event even relatively minor deviations in the flow rate 
can lead to undesirable and potentially dangerous changes in the rate of 
descent along the exterior of the building. 
To prevent this, the present invention employs a reduction gear drive which 
increases the speed of rotation of the gear pump by a factor in the range 
of between about 3:1 to 10:1, and preferably of about 5:1 over the rate of 
rotation of the drum. By giving the drum a relatively small diameter, in a 
preferred embodiment about seven inches, the gear pump will rotate at a 
rate of at least about 500 rpm when the cable payout speed is about four 
feet per second. At that speed the hydraulic fluid flow rate in the 
circuit should be in the range between about two and four gallons/minute 
with a presently preferred flow rate of about three gallons/minute. The 
above-identified Parker gear pump generates a flow rate of about three 
gallons/minute at a gear pump rotation of about 500 rpm, which assures 
good fluid flow control for all components of the hydraulic circuit.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring first to FIG. 1, a structure such as a highrise building 2 has an 
upright, exterior wall 4 and is divided into multiple, vertically 
separated floors 6. The upright walls include openings, such as 
floor-to-ceiling windows 8 which, upon the removal (e.g. breakage) of a 
window pane (not shown), provide access from an interior 10 of the 
building to the exterior thereof. One of the floors; say, an upper floor 
12, includes an emergency exit device 14 constructed in accordance with 
the present invention. 
A cable, constructed of a heat-resistant, non-flammable material, such as 
steel or non-combustible (at the encountered temperatures), e.g. glass or 
carbon filaments, to prevent damage to the cable from heat or flames 
generated during a fire, extends from the device over a pulley 18 and 
terminates in a free end to which a suitable connector 20 is secured. The 
connector may be part of a harness (not shown) which can be applied to a 
person to secure the person to the free end of the cable. The construction 
of such connectors and harnesses is well known and is therefore not 
further described herein. 
Pulley 18 is mounted at the end of a cantilever arm 22 which extends 
through opening 8 sufficiently far outwardly so that cable 16 and 
connector 20 attached thereto are clear of the exterior wall 4. Pulley 18 
is preferably sufficiently horizontally spaced from the exterior so that a 
person suspended from the cable clears, i.e. does not touch the building 
exterior, to prevent that person from sliding along the exterior during 
his or her descent. In the illustrated embodiment of the invention, the 
connector arm is attached to a pivot 26 mounted to an inside wall 24 of 
the building so that the arm can swing between its extended position 
(shown in FIG. 1) and an inoperative position, in which the arm and the 
pulley are in the interior 10 of the building, approximately at a position 
180.degree. offset from the operative position. 
The cantilever arm can of course be differently attached to the building. 
For example, it can be attached to and be an integral part of exit device 
14, it can be pivotally attached to other walls of the building, including 
interior floor 12, the ceiling or the exterior wall 4 (in which event 
pivot 26 may not be needed). Cable 16 can also be paid out from exit 
device 14 so that it runs over an edge 28 between floor 12 and exterior 
building wall 4. Although such an arrangement creates normally undesirable 
friction, particularly during the descent of a person, it nevertheless can 
be an acceptable arrangement because the exit device of the present 
invention is only rarely used, and since the cable is constructed of such 
materials as steel, occasional uses will not noticeably affect its 
integrity. When the cable is paid out over edge 28, it is preferred to 
round the edge where the cable can contact it to reduce friction and 
assure a smooth movement of the cable over the edge. 
In use, a person about to be lowered from upper floor 12 steps into or 
otherwise applies the harness, attaches it to cable end connector 20 (if 
not already attached), and then steps through opening 8 to the exterior of 
the building. As will be described in more detail below, as soon as the 
person's weight becomes suspended from the cable, the exit device 14 of 
the present invention self-initiates a controlled payout of the cable at a 
predetermined, safe speed, preferably at about four feet per second, until 
the person reaches ground 30 adjacent the building. Once on the ground, 
the person's weight is no longer suspended from the cable, which 
automatically terminates the payout of cable. On the ground, the person 
steps out of the harness and the cable can thereafter be retracted to 
raise the harness to upper level 12 for either standby storage and use in 
the event of another emergency, or for lowering the next person to the 
ground under the existing emergency. 
Referring now to FIGS. 2 and 3, the construction and operation of exit 
device 14 of the present invention are described in detail. The device 
includes a frame 12 forming a base 34 for attachment to building floor 12 
(not shown in FIGS. 2 and 3) and a pair of opposed, spaced-apart upright 
supports 36 the upper ends of which terminate in and are securely 
interconnected by an upper, generally horizontal top plate 38. In a 
preferred embodiment, the frame is a metal casting. 
A drum 40 is nonrotatably mounted on a shaft 44 with a key 46. The shaft is 
journalled in bearings 42 housed in appropriately sized holes formed in 
upright supports 38. 
In a presently preferred embodiment of the invention, the drum is made of 
two cast sections 48, 50 which are suitably secured to each other; for 
example, with bolts 52. Other methods of connection, such as welding, 
bonding, brazing, shrink fitting or directly threading the two drum 
sections to each other (not shown), can of course be substituted. The drum 
sections define a cylindrical cable winding periphery 34 which terminates 
in radially outwardly extending drum end flanges 54. Cable 16 can be wound 
onto or paid out from the drum periphery by rotating the drum in one or 
the other direction. 
In a presently preferred embodiment, the cable is paid out from the drum in 
a generally upward direction (as illustrated in FIG. 3) and extends 
through a guide plate 58 bolted to top plate 38 and having a slit 60 that 
extends parallel to and approximately over the length of cable winding 
drum periphery 56 as shown in FIG. 4. To minimize friction and cable 
bending during use, the longitudinal edges of slit 60 are rounded (not 
shown). When installed in a building and ready for use, cable 16 extends 
at an angle from the slit to pulley 18 as is generally illustrated in FIG. 
1. 
One end of shaft 44 extends past frame 32 and terminates in a stub shaft 62 
onto which a hand crank 64 can be nonrotatably attached; e.g. by giving 
the stub shaft and bore 63 of the crank a noncircular cross-section; e.g. 
a square, serrated or the like cross-section, or by keying the crank to 
the end of the shaft so that shaft 44, and therewith drum 40, can be 
manually rotated with the crank for retracting cable 16 and winding it 
about the drum periphery. 
To control and limit the speed with which the drum rotates when a person is 
being lowered to the ground, the shaft is rotationally coupled to a gear 
pump 66 by a drive connection. In a preferred embodiment of the invention, 
the latter is formed by a sprocket gear 68 nonrotatably carried on a drive 
shaft 65. A coupling 76 connects the drive shaft to the shaft 67 of the 
gear pump. A cooperating spur gear 70 is nonrotatably secured to drum 
shaft 44 by key 72. A spacer 74 may be provided for maintaining a fixed 
distance between the spur gear and drum 40. 
As is best seen in FIG. 2, an inlet 78 (shown in FIG. 3) and an outlet 80 
of the gear pump are in a hydraulic circuit 82 which begins and terminates 
at a hydraulic fluid tank 84 attached to frame 32 of the exit device. The 
hydraulic circuit has an intake line 86 which extends from the tank to 
inlet 78 (shown in FIG. 3) of the pump and a return line 88 which extends 
from outlet 80 of the pump back to tank 84. A constant flow control valve 
90 in the return line is located downstream (during normal operation) of 
the pump 3.5 outlet, and it controls the rate of fluid flow through the 
hydraulic circuit so that the flow remains constant irrespective of the 
fluid pressure generated by the pump in the return line and, therefore, 
also irrespective of the weight of the person being lowered to the ground 
during an emergency. Its construction is described in more detail below. 
Since the return line draws no liquid out of the tank, it can terminate at 
a relatively higher portion of the tank than where the intake and branch 
lines terminate because both of the latter must draw hydraulic fluid out 
of the tank during operation of the pump. 
The hydraulic circuit further includes a branch line 92 which is in fluid 
communication with the return line 88 upstream (during normal operation) 
of flow control valve 90. A check valve 94 in the branch line prevents 
flow therein in a direction away from pump 66 so that hydraulic fluid can 
only flow in the branch circuit from tank 84 to pump outlet 80. 
In use, when a person is suspended from cable connector 20, the weight of 
the person pulls on cable 16, which in turn causes drum 40 to rotate in 
drum bearings 42, thereby paying out cable and lowering the person to the 
ground. Rotation of the drum causes rotation of sprocket drive shaft 65 
and, via coupling 76 of gear pump shaft 67, at a rate which corresponds to 
the rate of rotation of the drum times the gear ratio between spur gear 68 
and sprocket 70. In the presently preferred embodiment this ratio is 5:1. 
As is well known, rotation of pump shaft 67 correspondingly rotates the 
pump gears on the inside of the pump (not shown). This rotation causes a 
vacuum at pump inlet 78, thereby drawing hydraulic fluid via intake line 
86 from tank 84, and expels pressurized fluid from outlet 80 into return 
line 88. Check valve 94 in branch line 92 prevents any fluid expelled from 
the pump from flowing through the branch line 92. 
Flow control valve 90 in return line 88 is set to generate a back pressure 
and limits the flow rate. The flow rate is selected so that the resulting 
rate of rotation of gear pump shaft 67 yields a surface speed at the drum 
periphery 56 which equals the predetermined speed at which the person is 
to be lowered to the ground; e.g. four feet per second as previously 
mentioned. Since the hydraulic fluid is not compressible, the gear pump 
will maintain this rate of rotation irrespective of the torque applied to 
it and, therefore, also irrespective of the weight suspended from cable 
connector 20. 
After the person has arrived at the ground and has been disconnected from 
the cable, the cable is rewound onto the drum with hand crank 64. 
During rewinding, the drum and therewith the gear pump rotate in the 
opposite direction. This creates a vacuum at pump outlet 80 and generates 
a reverse flow of hydraulic fluid through the pump; that is, into outlet 
80 and out of inlet 78. This flow direction is permitted by check valve 94 
so that, during rewinding of the cable, hydraulic fluid flows through 
branch line 92, check valve 94, pump 66 and then via inlet line 86 of the 
hydraulic circuit back into tank 84. The inlet line contains no flow 
restrictors so that there is substantially no resistance generated by the 
pump, to make the rewinding of the cable relatively easy and effortless. 
As soon as the free cable end has arrived at the upper floor 12, the exit 
device of the present invention is ready for reuse and will cause gear 
pump 66 to again apply the required braking force to drum 40 so that the 
next person can descend to the ground at the predetermined speed. 
The energy generated by the descending person is to a large extent 
converted into heat as the gear pump rotates and forces hydraulic fluid 
through flow control valve 90 back into tank 84. Since high temperatures 
can damage hydraulic fluid, it is important to control its temperature. 
This is at least partially achieved by providing the hydraulic circuit 82, 
including tank 84, with a sufficient volume of fluid to moderate its 
temperature rise. To prevent a repeated use of the emergency device from 
heating the hydraulic fluid to an unacceptably high temperature; e.g. to 
more than about 250.degree. F., without requiring an excessive amount of 
hydraulic fluid, it is further preferred to mount tank 84 so that its 
walls 96 (except for the wall attached to frame 32) are exposed to the 
surrounding atmosphere so that there will be heat transfer from the 
hydraulic fluid via the tank walls to the atmosphere once the temperature 
of the fluid exceeds the ambient temperature. The precise size of the heat 
exchange walls of tank 84 depends on the volume of hydraulic fluid, the 
expected number of repetitive uses during a given emergency; i.e. one use 
following shortly after another, the material and thickness of the tank 
walls, and the expected maximum ambient temperature. Those skilled in the 
art know how to dimension and shape (e.g. the use of undulating walls to 
increase their heat exchange surfaces without noticeably increasing the 
tank volume) the tank walls to effect the desired rate of heat exchange 
under the conditions for which the device is to be designed. 
Referring to FIGS. 3 and 5, the construction and operation of flow control 
valve 90 will be briefly described. As earlier mentioned, such valves are 
available, for example, from Parker Fluid Power, Hydraulic Valve Division, 
of Elyria, Ohio. For purposes of the present invention, such valves may be 
preset to permit a predetermined flow rate or they may be adjustable to 
change the flow rate. FIG. 5 illustrates an adjustable flow control valve, 
although it is presently preferred not to provide adjustability to prevent 
an unauthorized tampering of the valve during its long standby periods. 
The presently preferred Parker valve Model PCK820S has a preset flow rate 
of three gallons per minute. 
The adjustable valve illustrated in FIG. 5 has a generally cylindrical 
housing 98 and has an intake port 100 and an outlet port 102 at the 
respective ends of the housing. A flow control adjustment knob 104 (not 
used in the preferred embodiment of the invention) permits retraction and 
extension of a conical valve member 106 on the interior of the housing to 
vary the size of an annular opening between the conical valve member and 
the opposing valve seat. 
In operation, hydraulic fluid enters intake port 100 and flows via bores 
108 into an open space 110 on the interior of the housing. From there the 
fluid flows past conical valve member 106 and interior holes 112 in a 
longitudinally reciprocable spool 114 into an axially extending chamber 
116 formed by the spool. From the chamber the fluid flows past sets of 
compensating orifices 118, through an annular space 120, and out of outlet 
port 102. 
When the flow control valve 90 operates at its lowest operating pressure, 
spool 114 is positioned as is illustrated in FIG. 5 when the flow 
generated by gear pump 66 rises; say, as the result of a relatively 
heavier person being lowered to the ground, correspondingly higher 
pressure appears at inlet port 100 of the valve, thereby correspondingly 
raising the fluid pressure in interior space 110. The increased pressure 
generates an increased force acting on end face 122 of spool 114. This 
moves the spool in a downstream direction (to the right as seen in FIG. 5) 
in opposition to a force generated by a spring 124 acting against the 
other end of the spool, until the force generated by the increased fluid 
pressure equals the spring force. This axial movement offsets the sets of 
compensating orifices 118 formed in spool 114 and a surrounding portion 
126 of the housing, thereby effectively reducing the area of the 
compensating orifices and correspondingly reducing the area through which 
the fluid can flow. The reduction in the effective open area of the 
compensating orifices is selected, by appropriately configuring the size 
of the spool, the compensating orifices and spring 124, so that the fluid 
flow rate through the valve stays constant; e.g. at three gallons per 
minute. In other words, the effective open area of the compensating 
orifices is reduced in response to higher pressure to maintain the fluid 
throughput volume constant. 
Conversely, when the fluid pressure at inlet port 100 is reduced, the 
correspondingly reduced force acting on spool face 122 permits spring 124 
to axially move the spool in an upstream direction (to the left as seen in 
FIG. 5) until the compensating orifices in the spool and the surrounding 
portion 126 of the housing are again aligned. 
The flow control valve is selected so that the compensating orifices are 
aligned when the least amount of fluid pressure is generated by gear pump 
66. The valve is constructed and set so that the desired flow rate is 
achieved when the anticipated minimum weight is applied to cable end 
connector 20. In a presently preferred embodiment of the present 
invention, the minimum weight is 50 lbs.; e.g. the weight of a young child 
of sufficient age and ability to be lowered to the ground alone.