Parachute ground disconnecting devices

Reusable parachute ground disconnecting devices provide constant release load percentages within a range of 25 to 70 percent of the load weight for more reliable delatching characteristics on ground contact even in the presence of high ground winds, and with virtually no risk of premature delatching occurring while airborne. Non-linear main springs consisting of stacked disk springs provide ever diminishing deflection to the load suspending assembly as the load size increases, in combination with fixed latch geometry produce constant load release characteristics for the entire capacity rating for a given device. Various time delay means, including an hydraulic dampened load release timer provide added safety and reliability by isolating the delatching system when fluctuations in load weight occur during initial deployment. Disclosed concepts are readily adaptable to high capacity devices for loads of up to 30 tons, and even more.

TECHNICAL FIELD 
The present invention relates generally to the field of parachute 
accessories, and more specifically to improved devices which allow for the 
automatic release of parachute borne loads upon contact with the ground. 
BACKGROUND OF THE INVENTION 
In parachuting a load from an airplane it is important that the load be 
safely secured to the parachuting means during descent. Likewise, it is 
also important for the load to be spontaneously released from the 
parachuting means upon striking the ground, or other supporting surface. 
Unless there is immediate separation of the load from the parachuting 
means on ground contact the load can be dragged over the supporting 
surface by surface winds engaging the parachute. 
Parachute ground disconnecting devices have been developed which 
automatically release a payload with ground contact. Such devices perform 
as coupling means between the parachute and load to safely secure loads 
when suspended during descent of the parachute. When the load makes 
contact with the ground so the load weight falls the coupling device 
should automatically open to allow separation of the load and parachute. 
One significant problem associated with parachute ground disconnecting 
devices heretofore has been overcoming fluctuations in effective load 
weight during descent. For example, in the first few seconds after 
parachute deployment, forces applied to disconnecting devices can drop off 
severely or vary significantly due to transient parachute inflation 
phenomena. The device may repeatedly oscillate due to snatch forces, 
parachute over-inflation and swing through. To overcome such significant 
variations in forces the release load percentage or "RLP", which is the 
ratio of the tension at the instant of disconnection to the weight of the 
load during steady descent, can be lowered, e.g. below 25 percent. This 
however, can result in the parachute ground disconnecting device not 
readily releasing its load on ground contact, or exhibiting poor high wind 
release characteristics. In fact, many earlier parachute ground 
disconnecting devices required total slack-off of tension when the cargo 
made ground contact. But, with ground winds catching a parachute at the 
time of desired disconnection there was usually no slack of tension and 
the release device would not actuate. In attempting to modify ground 
disconnecting devices so the weight required to initiate load 
disconnection is more than zero and in some cases closer to the real 
weight of the load, i.e. a RLP of &gt;40 percent, trade-offs in descent 
security can result which increase the potential for premature delatching 
of the device and load loss while still airborne. 
Hence, it has been observed that prior efforts have not been entirely 
satisfactory in developing parachute ground disconnecting devices capable 
of providing both a high degree of load security at all stages of descent 
and conditions while also providing the desired instantaneous load release 
characteristics upon ground contact, especially in the presence of high 
ground winds and soft ground conditions. 
For instance, U.S. Pat. No. 2,732,245 appears to disclose an automatic 
parachute release coupling device which employs a time delay mechanism, 
main canopy activation and ground disconnecting action. However, this 
earlier device relied on coil type springs exclusively. It was found that 
with such linear type springs constant RLPs were not readily achieved. As 
a result, it was not possible to produce reliable load disconnection on 
ground contact throughout the entire rated load capacity of the device, 
under all wind and ground conditions. 
Other such devices have relied on load suspending assemblies having 
components which were not integral and capable of moving as fixed geometry 
units. Consequently, if after parachute deployment load force drops off or 
varies significantly, and erratic movements occur there is increased risk 
of premature delatching occurring. In addition, some earlier devices 
lacked the desired high degree of reliability, especially during the first 
few seconds after deployment before stable steady descent occurs. During 
this stage of descent if the disconnecting mechanism is not isolated from 
other component systems as to be rendered fully inoperative, the risk of 
premature delatching can also be greater. 
Earlier automatic parachute release devices, such as those disclosed by 
U.S. Pat. No. 2,732,245, while possessing merit, also relied on systems 
which added to the technical complexity and concomitant cost of the 
devices, making them largely impractical and non-economic, particularly 
those which were not readily reusable. 
Accordingly, it would be highly desirable to have more reliable and 
reusable parachute ground disconnecting devices which provide constant 
release load ratios (as a percentage of suspended weight) over an entire 
load range rating for a given device. Such devices should be readily 
adaptable for a broad range of payload sizes, including ultra-heavy 
payloads of up to 30 tons or more, such as required in parachuting armored 
vehicles, and which have a high degree of reliability and do not 
prematurely delatch while airborne, and spontaneously separate from the 
parachute on ground contact, even in the presence of high winds. 
SUMMARY OF THE INVENTION 
Accordingly, it is a principal object of the invention to provide for 
improved parachute ground disconnecting devices, especially those which 
are capable of maintaining substantially constant RLPs. Generally, devices 
of the invention are characterized by a casing with at least one interior 
compartment, a load suspending assembly located at a first end of the 
device and means for connecting the device to a parachute located at a 
second end of the device. Structurally, the devices also consist of means 
for locking and releasing a load on the load suspending assembly and 
spring means positioned in the interior compartment of the casing. The 
spring means are effective in retaining the device in a retracted position 
when not under load and limiting downward deflection when under force of 
load. The devices also have timer means for actuating the means for 
locking and releasing a load on the load suspending assembly after lapse 
of a sufficient time interval for stabilized descent of the parachute and 
load, and for release of the load from the load suspending assembly as the 
spring means returns towards a fully retracted position upon ground 
contact by the load. 
The spring means of the foregoing ground disconnecting devices are 
characterized by non-linear force displacement curves permitting load 
disconnection to occur throughout the rated weight capacity of the device 
when tension on the device falls to an adjustable range generally from 25 
to about 70 percent of the load weight. Thus, the spring means can be 
comprised of a plurality of disk type springs placed in stacks to provide 
ever diminishing deflection with additional load applied to the load 
suspending assembly. 
It is a further object to provide ground disconnecting devices wherein the 
means for locking and releasing a load on the load suspending assembly 
comprises a longitudinally movable bar or toothed rack member which freely 
moves with fluctuating load weights during the more turbulent initial 
period of descent, and bar or rack locking means automatically actuated by 
the timer means for engaging the movable bar or rack during stabilized 
descent and which releases the load from the load suspending assembly when 
the spring means returns towards a fully retracted position with ground 
contact by the load. 
It is yet a further object to provide for devices consisting of an upper 
casing with an interior compartment and means for connecting with a 
parachute, and an axially aligned load suspending assembly which is 
movable relative to the upper casing. The load suspending assembly 
comprises a rod extending into the casing interior, connecting means for 
holding a load, means for locking and releasing a load from the connecting 
means, and gear means, such as a rack for engaging the locking and 
releasing means of the load suspending assembly at a first end. The rack 
extends into the upper casing interior at a second end. Importantly, the 
device is powered by main spring means providing restricted deflection. 
That is to say, the main spring means is characterized as non-linear 
(designed to a specific function) providing ever diminishing deflection of 
the lower load suspending assembly as additional load is applied. The main 
spring means is positioned in the casing interior for engaging with the 
rod of the load suspending assembly for retaining the load suspending 
assembly in a retracted position prior to deployment, and for limiting the 
stroke of the load suspending assembly away from the casing when a load is 
applied. The device also includes timer means for providing a delay 
interval corresponding substantially to a period running from the time of 
parachute opening to the time of stabilized descent. Other elements of the 
device include rack locking means automatically actuated by the timer 
means for engaging the rack for preventing longitudinal movement of the 
rack during stabilized descent, and when the distance between upper casing 
and the lower load suspending assembly moves towards zero upon ground 
contact by the load, to delatch the locking and releasing means for 
separating the load from the parachute. 
It is thus a principal object of the invention to provide a reusable 
parachute ground disconnecting device characterized by constant RLPs over 
the entire rated load capacity, subject to the constraint of fixed latch 
geometry and associated fixed stroke to reliably actuate load release with 
ground contact. The objectives of the invention are more readily achieved 
thorough spring means characterized by non-linear force displacement 
curves permitting load disconnection to occur throughout the rated load 
capacity of the device when tension on the device falls to about 25 to 
about 40 percent of the real load weight. Significantly, the force of the 
load on the device need not drop to zero in order to effectuate 
delatching. Within the above range of 25 to 40 percent the risk of 
premature delatching or resistance to load disconnection occurring on 
ground contact is minimal. This is readily accomplished with a plurality 
of disk type springs placed in varying stacks for a shallow/short stroke 
of the load suspending assembly, even when under force of capacity loads. 
That is to say, deflection of the load suspending assembly from the upper 
casing is ever diminishing to a set final deflection, i.e. disks 
flattened, as additional load is applied. 
It is still a further object of the invention to provide a parachute ground 
disconnecting device wherein the main spring means provides the energy for 
retraction of the load suspending assembly towards the upper casing on 
ground contact for disengagement of a lever mounted release arm to actuate 
delatching and load release. 
It is yet a further object of the invention to provide timer means, such as 
in the form of a gear train and escapement, and other timer types for 
added security by providing automatic delays in actuating gear or rack 
locking means for about an initial 5 to 20 second period in which the 
release mechanism is isolated from possible premature release at the 
transient period of parachute deployment, and for readying the device for 
automatic ground disconnect during steady, stable descent. 
It is still a further object of the invention to provide a heavy duty 
version of the parachute ground disconnecting devices having load ratings 
of several tons for large loads, heavy equipment, large personnel 
carriers, armored vehicles, and so on, also characterized by substantially 
constant release load percentages. The devices consist of an upper 
parachute disconnecting block suitable for engaging several parachutes and 
an axially aligned lower load suspending casing having interior 
compartments and means for connecting a load. The lower load suspending 
casing is movable relative to the upper parachute disconnecting block, the 
latter comprising a plurality of rods extending vertically downwardly into 
the interior of the lower load suspending casing. The parachute 
disconnecting block also includes an outer frame member for supporting a 
plurality of parachute riser fingers and parachutes when the fingers are 
locked, an axially slidable retainer assembly (spring loaded) positioned 
adjacent to the outer frame member for locking and releasing the parachute 
riser fingers, and a gear, such as a rack for engaging the slidable 
retainer assembly at a first end. The rack extends into the interior of 
the lower load suspending casing at a second end. Significantly, the 
device includes non-linear main spring means to provide ever diminishing 
deflection characteristics to the load suspending casing with additional 
load applied. The main spring means are positioned in the lower load 
suspending casing for engaging with the rods of the parachute 
disconnecting block for retaining the load suspending casing in a 
retracted position when not under load, and for limiting the stroke of the 
load suspending casing away from the parachute disconnecting block when 
under force of a load. The lower load suspending casing also includes 
timer means for providing a delay interval corresponding substantially to 
the period running from the time of opening of a parachute to the time of 
stabilized descent. Rack locking means are automatically actuated by the 
timer means for engaging the rack and preventing longitudinal movement of 
the rack during stabilized descent. When the distance between the load 
suspending casing and the parachute disconnecting block moves towards zero 
upon ground contact the main spring means retracts the axially slidable 
retainer assembly against its spring loading to delatch the parachute 
riser fingers and parachutes from the device. As with other embodiments of 
the device, delatching is not dependent on the load dropping to zero. 
It is still a further object to provide an even more simplified embodiment 
of the parachute ground disconnecting device of this invention which still 
allows for maintaining a substantially constant release load percent, but 
where exact time delays for arriving at a steady, stable descent are less 
critical. This further embodiment consists of a casing with an interior 
compartment and means for connecting with a parachute. The device includes 
an axially aligned load suspending assembly movable relative to the 
casing, a rod extending into the casing interior, connecting means for 
holding a load, and means for locking and releasing a load on the 
connecting means with ground contact. The device employs load release 
timer means and main spring means both housed in the casing interior. The 
main spring means engages with the rod for retaining the load suspending 
assembly in a retracted position when not under load and for limiting the 
stroke of the load suspending assembly away from the casing when under 
force of a load. The load release timer means includes a pushrod cylinder, 
an axially aligned pushrod at a first end engaging the push rod cylinder 
and linking with the locking and releasing means of the load suspending 
assembly at a second end. Ram means are axially aligned with the pushrod 
cylinder and pushrod. Importantly, the load release valve means includes 
means for dampening vertical movement of the ram means and pushrod when 
under compression, such as on ground contact by the load. 
it is still a further object to provide for ground disconnecting devices 
with load release timer means with dampening means for rams and adjacent 
pushrods comprising a piston with an aperture for non-compressible fluids 
for gradual displacement through the aperture over a period of 
approximately 2 to about 20 seconds. The device includes adjacent spring 
means positioned in the pushrod cylinder for compression and gradual 
movement of the ram means towards the pushrod and gradual displacement of 
the hydraulic fluid when a load is applied to the load suspending 
assembly. 
It is still a further object to provide a parachute ground disconnecting 
device comprising a casing with at least one interior compartment, means 
for connecting the device to a parachute located at a first end of the 
casing, a load suspending assembly having latching means located at a 
second end of the casing, means for locking and releasing a load on the 
load suspending assembly including a longitudinally moveable bar affixed 
to the means for connecting the device to a parachute, and spring means 
positioned between the longitudinally moveable bar and the load suspending 
assembly. The spring means is characterized by limiting the downward 
deflection of the casing from the longitudinally moveable bar. The means 
for locking and releasing a load on the load suspending assembly comprises 
a longitudinally moveable bar affixed to the means for connecting the 
device to a parachute, axially aligned means for engaging with the 
longitudinally moveable bar and for releasing a load on the load 
suspending assembly on ground contact, means for laterally deflecting the 
axially aligned means for engaging with the longitudinally moveable bar 
and for releasing a load on the load suspending assembly on ground 
contact, and timer means for actuating the means for laterally deflecting 
the axially aligned means for engaging with the longitudinally moveable 
bar and for releasing a load on the load suspending assembly. The 
longitudinally moveable bar comprises a rack having a plurality of 
adjacent teeth. 
It is still a further object of the invention to provide ground 
disconnecting devices wherein the axially aligned means for engaging with 
the longitudinally moveable bar and for releasing a load on the load 
suspending assembly comprises a cup means, a vertically rigid wire having 
one end engaged with the cup means, and a vertically moveable pin means 
for contacting and de-latching the latching means. The cup means is 
adapted to engage with at least one of the teeth of the rack. 
It is still a further object of the invention to provide ground 
disconnecting devices wherein the means for laterally deflecting the 
axially aligned means for engaging with the longitudinally moveable bar 
and for releasing a load on the load suspending assembly is a horizontally 
moveable bar spaced from the cup means. The cup means is positioned on a 
vertical axis sufficiently close to the horizontally moveable bar to cause 
the cup means to disengage from the horizontally moveable bar and return 
to axial alignment after the vertically moveable pin means de-latches the 
latch on ground contact.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Turning to FIG. 1, there is shown a preferred first embodiment of parachute 
ground disconnecting device 10 in resting position before being deployed. 
Device 10 may be used in supporting loads over varying weight ranges from 
under 45 kg (100 pounds) and up to several hundred kilograms. The capacity 
of a typical disconnecting device could range, for example, from about 34 
kg (75 pounds) to about 227 kg (500 pounds). Larger capacity units for 
substantially heavier loads will be discussed in detail below. All such 
devices advantageously provide constant RLPs throughout their rated load 
capacities. 
Disconnecting device 10 includes principal sections consisting of an upper 
casing or housing 12 and a lower axially aligned load suspending assembly 
14. Integral with casing 12 is parachute connecting ring 16 for engaging 
with parachute 18, illustrated by a vertical arrow only. Parachute riser 
finger 20 shown sectionally may be affixed to the device via connecting 
ring 16. 
Lower axially aligned load suspending assembly 14 is shown by FIG. 1 in 
fully retracted position butted against casing 12. Assembly 14 is 
partially sheathed by outer protective housing 15. The assembly consists 
of hook 22, release latch 24 pivotally mounted to hook 22 through yoke and 
threaded pin assembly 26, at one end, and locking edge 28 at a second end 
interconnected with edge 30 of release arm 32, the latter being rotatable 
through connecting pin 34. Release arm 32 includes slot 36 which slidably 
engages with pin 40 of rack 39. 
Spring means (not shown) of conventional design exerts force to maintain 
release arm 32 in a locked position with release latch 24 prior to ground 
contact by the load. This retains load ring 38 of payload 41, shown only 
as an arrow, in a securely locked mode on hook 22. While not shown in FIG. 
1, when device 10 is first deployed lower suspending assembly 14 
translates downwardly from upper casing 12, and during the initial stages 
of descent rack 39 will be free to translate and move downwardly and 
upwardly in step with the lower suspending assembly without premature 
delatching of the device. 
The lower suspending assembly further includes a rod 42 and nut 44 
positioned for movement in cylinder 46 of the upper casing. As with rack 
39, downward movement of rod 42 and nut 44 occurs in concert with a load 
suspended from hook 22 of the lower suspending assembly. Cylinder 46 is 
preferably filled with non-linear disk type springs 48 of conventional 
design mounted on rod 42 for limiting free downward movement of the 
assembly. More specifically, the principal objective of the non-linear 
type springs is ever diminishing deflection of the lower suspending 
assembly with additional load applied. As main springs of the device, this 
can best be achieved by nesting disk type springs into layered stacks 50 
of varying numbers for RLPs of 25 to 40 percent over the entire rated load 
capacity for a given device. Various stacking patterns may be used to 
achieve this end result. One includes nesting several springs together 
into concave formats wherein individual spring stacks are positioned in 
alternative directions, i.e. front to back, and so on. 
It was discovered, for example, when spring stacks are layered in 
diminishing numbers/thicknesses where the largest stacks are positioned at 
the bottom of cylinder 46 and gradually decrease in number towards the top 
of the cylinder near nut 44 the desired ever diminishing additional 
deflection characteristics of the load suspending assembly with additional 
load applied occurs throughout the weight capacity rating of the device. 
That is to say, differential deflection will occur with a small load, 
e.g., 34 kg (75 pounds) to produce downward movement, e.g., 5 mm (0.20 
inches) of the load suspending assembly from its resting point, whereas 
with a substantially larger load, e.g. 227 kg (500 pounds), the relative 
movement of the load suspending assembly will be, for example, only 10 mm 
(0.40 inches), or in other words, only 5 mm more for over 6.5 times more 
weight. 
The significance of non-linear springs is demonstrated graphically by FIG. 
2 and Tables I and II below: 
TABLE I 
______________________________________ 
LINEAR SPRINGS 
Example 
Starting Load (lbs) 
Release Load (lbs) 
RLP (%) 
______________________________________ 
1 500 350 70 
2 400 250 63 
3 300 150 50 
4 200 50 25 
5 100 No Release -- 
______________________________________ 
TABLE II 
______________________________________ 
NON-LINEAR SPRINGS 
______________________________________ 
1 500 155 31 
2 400 130 32 
3 300 100 33 
4 200 65 33 
5 100 25 25 
______________________________________ 
FIG. 2 and Tables I-II demonstrate the absence of a constant release load 
percentage within the desired range of 25 to 40 percent of the 
starting/actual load weight with a ground disconnecting device equipped 
with linear springs, and constant RLPs with non-linear main springs within 
the desired range of 25 to 40 percent for all loads, regardless of weight. 
In this manner, the ground disconnecting devices of the present invention 
achieve constant RLPs through non-linear springs to provide a load 
suspending assembly with a downward stroke characterized by ever 
diminishing deflection with additional load applied, in combination with 
fixed latch geometry for constant load release performance when the 
tension on the device falls to about 25 to about 40 percent of the 
starting load weight. Advantageously, the geometry of the latching means 
does not change with variations in load weight. Regardless of the 
particular value of gap "g" attained during steady descent, a specific 
amount of gap reduction, ".DELTA.g", is required on ground contact for 
release to occur. This is due to the fixed geometry of release latch 24 
and release arm 32. Through the use of non-linear main spring stacks a 
condition is created wherein the main spring force drops nominally to 30 
percent of its initial value within the operating range of the device with 
re-extension of the main spring by the amount .DELTA.g. The limited 
deflection of the load suspending assembly achieved with the non-linear 
springs even with heavier loads restricts the degree of total movement of 
the suspending assembly and ultimate movement of the latch geometry to 
effectuate delatching and load release. Hence, while greater weight will 
increase the deflection of the suspending assembly away from the upper 
casing somewhat, variations in load weight, and particularly loads of 
greater weight do not necessitate modification of the release latch 
geometry to effectuate reliable delatching and load release over lighter 
weight loads. Accordingly, constant RLPs are achieved within a desired 
range of 25 to about 40 percent of the real load weight to provide 
reliable delatching characteristics for all loads within the rated 
capacity of a given device on ground contact even in the presence of 
winds, all with high descent security, i.e., virtually no risk of 
premature delatching while airborne. 
While the invention is specifically demonstrated with disk type springs, it 
should be understood that non-linear spring characteristics may also be 
substantially duplicated with other types of springs. For example, a 
short, rigid coil type spring in combination with a governor, for example, 
for limiting the downward stroke of rod 42 and nut 44, while less 
preferred, may nevertheless be employed in place of stacks of disk type 
springs. 
In addition to cylinder compartment 46, upper casing 12 has a second 
compartment 52 for housing timer 54, pushrod 56, rack 39 and rack wedge 
58. Timer 54 essentially functions as a "safety" by providing an initial 
delay period beginning with deployment of the parachute when turbulence 
and fluctuating load weights and movements present the greatest risks of 
premature delatching and load loss occurring before ground contact. During 
the initial 5 to 20 seconds after parachute deployment before steady 
descent of the load occurs timer 54 provides an important interval prior 
to activation of the ground disconnecting device by allowing unrestricted 
movement of rack 39. By allowing such unrestricted movement, momentary 
reductions in load weight due to transient parachute inflation, etc., and 
resulting retraction of the load suspending assembly by main spring 50 
will prevent premature rotation of release arm 32 and unlocking of release 
latch 24. Accordingly, timer 54 isolates the delatching system during the 
initial transient period of parachute deployment until the load achieves 
equilibrium and steady descent. 
With lapsing of the time delay and with steady descent of the parachute and 
airborne load, locking of rack 39 with rack wedge 58 occurs preventing 
further vertical movement of the rack. This effectively activates the 
disconnecting device for delatching to occur automatically upon ground 
contact as the weight load on the device falls to about 25 to about 40 
percent of the starting weight. 
Timer 54, which is mounted to the upper casing in compartment 52 by 
threaded mounting screws 55, includes a bellcrank 60 with locking ledge 
62, cranking input shaft 64, cranking spring 66 mounted to the timer 
bearing plate 82 by pin 68 at a first end and to thebellcrank by pin 70 at 
a second end. In running mode, cranking spring 66 turns bellcrank 60 in a 
counter clockwise direction. FIG. 1 is shown with the timer wound for 
running by turning input shaft 64 clockwise prior to the device being 
deployed. The uppermost end of rack 39 includes a bellcrank lock 71 which 
rests against bellcrank ledge 62 at the time of deployment. FIG. 1 thus 
illustrates the configuration of the device prior to deployment when not 
under load. A first end of pushrod 56 is mounted for movement to bellcrank 
60 with linking pin 72. Pushrod 56 is also mounted for movement at a 
second end to rack wedge 58 by linking pin 74. Rack wedge 58, which 
includes a locking tooth 76, is mounted for rotation to the upper casing 
12 in compartment 52 by connecting pin 78. Hence, counter clockwise 
movement of bellcrank 60 produces a downward movement of push rod 56 and 
clockwise rotational movement of rack wedge 58, so as to bring locking 
tooth 76 in an upward position towards toothed rack collar 80. 
Toothed rack collar 80 contains a plurality of adjacent teeth. Rack 39 and 
toothed rack collar 80 automatically index with movement of the load 
suspending assembly for engagement by locking tooth 76 of rack wedge 58 
between teeth of collar 80. The particular teeth engaged with by locking 
tooth 76 is dependent on the weight of the load. Accordingly, the 
parachute ground disconnecting device provides the important benefit of 
automatic sensing and registration of load weight. Downward movement is 
determined by load weight. With a fully inflated parachute, stable steady 
descent and lapsing of the time delay rack 39, toothed collar 80 and lower 
suspending assembly 14 become locked against any further sliding movement 
relative to upper casing 12. 
FIGS. 3-4 illustrate the internal components of one representative 
embodiment of timer 54 which is a gear train and escapement type. The 
timer consists of bearing plates 82, 84 with a plurality of drilled 
bearing holes for gears and shafts. Spring 66 (FIG. 1) applies counter 
clockwise rotational forces to bellcrank 60 and shaft 86 (FIGS. 3-4). 
Rotation of bell crank 60 turns gear 88 having 50 teeth with an 80 DP. 
Gear 88 meshes with pinion 90 having 10 teeth with an 80 DP on shaft 92. 
Gear 94 contains 48 teeth with a 96 DP. Rotation of gear 94 turns pinion 
96 having 10 teeth with a 96 DP on shaft 98. Gear 100 contains 44 teeth 
with a 96 DP. Rotation of gear 100 turns escapement pinion 102 having 10 
teeth with a 96 DP on escapement shaft 104. Escapement wheel 106 contains 
24 teeth 60.degree. sharp V form having a root diameter 8.13 mm (0.320 
inches) and an outer diameter 10.62 mm (0.418 inches). Escapement wheel 
106 mates with pallet 110. Revolution of escapement wheel 106 on shaft 112 
causes pallet 110 to oscillate over a narrow angular range. Pallet 110 may 
have mass addition (not shown) for increased energy dissipation and 
reduced timer running speed. 
Shafts 64, 86, 92, 98, 104 and 112 are free to rotate in bearing openings 
in each of plates 82 and 84. Spring 66 rotates bellcrank 60 and shaft 86. 
For every one rotation of shaft 86 there are 106 rotations of shaft 104 
due to an increase in gear staging. For every one rotation of shaft 104, 
pallet 110 goes through 24 full cycles of small angular oscillation, 
coming to full stop twice per oscillation. Each time pallet 110 is brought 
to a full stop, its kinetic energy is dissipated in the form of acoustic 
emission, i.e. a "click" and mechanical vibration are generated. 
Spring 66 imparts a certain amount of energy to the timer system and pallet 
110 dissipates this energy. The speed of the timer is determined by the 
speed producing an equilibrium between input spring energy, which is 
relatively speed independent, and pallet percussion energy out, which is 
very speed dependent. The parameters which control the running speed 
consist of spring force; overall gear ratio; pallet angular travel from 
extreme to extreme, and moment of inertia of pallet 110 about the axis of 
shaft 112. In practice, the time delay is determined by the speed at which 
bellcrank 60 travels and how far the bellcrank has to travel from the 
point of release/ activation to the point of travel completion. 
In most instances, timer 54 is actuated automatically. However, the timer 
can also be activated semi-automatically whereby the timer is provided 
with a pull pin (not shown) such that it can be rigged into the overall 
parachute system for starting the timer running when the parachute lines 
first reach their fully payed out state. 
While the invention has been illustrated with timer means consisting of a 
gear train and escapement type timer having running times of about 5 to 20 
seconds, it should be understood that other timers may be employed, e.g. 
pneumatic time delay, and so on. 
Operation of the parachute ground disconnecting device may be demonstrated 
by reference to FIGS. 5-8. Initial parachute deployment causes hook 22 of 
the load suspending assembly 14 to separate from upper casing 12 by the 
distance "g" (FIG. 5). The downward force 41 overcomes the retracting 
force of disk springs 48 in forming gap "g". This initial downward 
movement causes bellcrank lock 71 on the end of rack 39 to disengage from 
locking ledge 62 on bellcrank 60. Bellcrank 60 begins to move counter 
clockwise under the action of spring 66. The rotational movement is slow 
and regular due to the damping imparted by gear train and escapement type 
timer 54. Pushrod 56 interconnecting bellcrank 60 and rack wedge 58 under 
counter clockwise movement of the bellcrank produces a slow and regular 
clockwise rotational movement of the rack wedge. Locking tooth 76 moves 
towards toothed rack collar 80 as the rack wedge rotates. So long as 
contact has not been made between locking tooth 76 and any teeth of rack 
collar 80, the lower suspending assembly 14, including rack 39, release 
arm 32, release latch 24, hook 22 and rod 42 are free to move together as 
a fixed geometry unit. If in the first few seconds after parachute 
deployment force 41 drops off severely or varies significantly due to 
transient parachute inflation the entire load suspending assembly can 
freely retract back to the upper casing 12, and translate away therefrom, 
repeatedly if necessary, without any premature delatching occurring. 
Once stable, steady descent of the airborne load has been achieved under a 
fully inflated parachute, the gap "g" (FIG. 6) between upper casing 12 and 
lower load suspending assembly 14 will settle to a value which may be 
relatively large if load 41 is a heavy payload, e.g. 227 kg (500 pounds), 
and relatively small if load 41 is a lighter payload, e.g. 34 kg (75 
pounds). Locking tooth 76 on rack wedge 58 engages with toothed collar 80 
on rack 39 with lapsing of the time delay (FIG. 6). The rack becomes 
locked against any further vertical movements relative to upper casing 12. 
Pushrod 56 is preferably a compressible arm to assure that locking tooth 
76 on rack wedge 58 will be instantly driven and seated between teeth on 
rack collar 80 under a sudden upward movement of rack 39 (FIG. 7). The 
time delay for this action to occur is achieved with timer 54, timed to 
occur after the parachute is open and stable, based on foreknowledge of 
how long parachute inflation and stabilization is required in a worst 
case. 
When payload 41 makes ground contact (FIG. 8), the force created by load 41 
drops off suddenly towards zero, and the gap "g" between upper casing 12 
and lower load suspending assembly 14 moves toward zero in response 
thereto. Retraction of assembly 14 is driven by the main spring action of 
layered non-linear spring stacks 50. However, because rack 39 remains in a 
locked condition it is not free to move upwardly with other components of 
the load suspending assembly when the load weight on the device moves 
towards zero. As a result of pin 40 remaining stationary, release arm 32 
mounted on connecting pin 34 is forced downwardly in a clockwise movement 
causing edge 30 to pivot upwardly from locking edge 28 of the release 
latch 24 to instantaneously and reliably delatch when load 41 drops to 
about 25 to 40 percent of its steady descent value. The ground 
disconnecting device delatches without the load weight on the device 
dropping to zero. 
FIGS. 9-11 relate to a further embodiment of the parachute ground 
disconnecting device incorporating the concepts of the invention for 
maintaining a substantially constant release load percent. This embodiment 
is especially adapted for heavier loads, such as trucks, armored vehicles, 
and the like, which may weigh from about 2,275 kg (5,000 pounds) to about 
27,000 kg (60,000 pounds), and more. The heavy duty ground disconnecting 
device consists of an upper parachute disconnecting block 114, and an 
axially aligned lower load suspending casing 116 which is movable relative 
to the parachute disconnecting block. The parachute disconnecting block 
consists of an outer generally D-shaped frame 122 having dual spaced rods 
118 and terminal nuts 119, each rod and nut extending downwardly into 
cylindrically shaped interior spaces 120 in load suspending casing 116. 
The rods and nuts have a plurality of non-linear spring stacks 124, such 
as disk springs previously discussed. The stacks are preferably of 
diminished size towards the lowermost end of cylinders 120. The spring 
configuration is characterized by a non-linear force displacement 
permitting load disconnection to occur throughout the rated weight 
capacity of the device when tension on the device falls to about 25 to 
about 40 percent of the real load weight upon ground contact. 
Outer frame 122 of the parachute disconnecting block also includes a 
support bar 126 for holding multiple parachute riser fingers 128 as 
connectors for parachutes 130 shown by arrows. Each riser finger 128 and 
parachute can have a rated weight capacity, for example, of 2273 kg (5,000 
pounds). While the device of FIG. 9 is illustrated with eight riser 
fingers and parachutes for a total capacity of 18,182 kg (40,000 pounds) 
this embodiment is intended to have up to twelve or more such riser 
fingers for even larger payloads. 
Parachute disconnecting block 114 also includes a vertically slidable riser 
finger retainer 132 (spring loaded into position) for locking and also 
releasing the parachute riser fingers 128 when the suspended load makes 
contact with the ground and the weight of the load is reduced. The 
vertically slidable retainer 132 includes a generally U-shaped slot 134 
(shown best by FIGS. 10-11) at the head of the retainer for holding the 
fingers in a locked position around support bar 126 of outer frame 122. 
Riser finger retainer 132 includes parallel vertical rods 135, and arms 
136 mounted for rotation on their respective central axes by pins 138, 
each vertical rod 135 having an arm 136 slidably mounted at a first end. 
The second ends of arms 136 are slidably mounted to the upper end 140 of 
rack 142. It will be understood the device includes spring means (not 
shown) for maintaining riser finger retainer 132 in an elevated position 
wherein the riser fingers are locked together around support bar 126 for 
securing the parachutes. 
Lower load suspending casing 116 consists of load rings 144 for connecting 
payload 146, shown by arrows; timer 148 with bellcrank 150 spring loaded 
for counter clockwise rotation and bellcrank locking ledge 152; rotatable 
rack wedge 154 having locking tooth 156 for engaging toothed collar 158 
mounted on rack 142. Rack wedge 154 and bellcrank 150 are interconnected 
by pushrod 160. Counter clockwise rotation of bellcrank 150 results in 
clockwise rotation of rack wedge 154 and locking tooth 156 for engagement 
with teeth on toothed collar 158 causing locking of rack 142 from vertical 
movement after the airborne load has achieved steady descent and the delay 
provided by timer 148 has lapsed. 
FIG. 10 illustrates the locked position of parachute riser fingers 128 
during initial deployment and steady descent of the load, prior to ground 
contact. When the running timer becomes exhausted and rack 142 becomes 
locked, with ground contact of load 146 and the weight of the load being 
reduced main springs 124 retract lower load suspending casing 116. Because 
rack 142 is locked retraction of casing 116 results in rotational movement 
of arms 136 and retraction of riser finger retainer 132 (See FIG. 11) 
releasing riser fingers 128 from U-shaped slot 134 to disengage the 
parachutes from the device and payload. 
FIG. 12 is a further embodiment of the ground disconnecting device which 
provides the important advantages of constant RLPs in the range of 25 to 
40 percent of the real load weight. This alternative embodiment, like 
those previously discussed, also provides ever diminishing deflection of 
the lower suspending assembly additional load applied using non-linear 
springs and fixed latch geometry. The device of FIG. 12 is especially 
useful when specific time delays are less critical beginning with the 
initial transient period of parachute deployment to stable descent occurs. 
The device offers the advantages of a more simplified design, increased 
ruggedness, fewer exterior seals, greater compactness and fully automatic 
resetting, all without trade-offs in constant RLPs. 
Instead of employing a timer with separate gear train and escapement, 
bellcrank, pushrod, rack and rack wedge for locking the rack after the 
initial transient period of parachute deployment according to the prior 
embodiments, the device of FIG. 12 utilizes a load release timer 162, 
which serves an equivalent function of the aforementioned elements. Load 
release timer 162, which may include devices such as an hydraulic 
dash-pot, is positioned in the interior of upper casing 164, and consists 
of a guide gland or sleeve 166, and an upper axially aligned liner 168. A 
vertically positioned pushrod 170 is joined at a first end to release arm 
172 of the lower suspending assembly 173 by means of pin 167 for movement 
in slot 176. Pushrod 170 at a second end is threaded to pushrod cylinder 
174 and is retained by means of guide 171. Low drag wiper seal 175 is 
useful for excluding foreign matter. Load release timer 162 also utilizes 
a ram 178 axially aligned with pushrod 170. The interior of pushrod 
cylinder 174 includes a spring 180 coiled around the lower portion of ram 
178. Spring 180 is in contact with ram base 182 at a first end and flange 
184 of pushrod cylinder 174 at a second end. Ram base 182 makes contact 
with pushrod head 183 when the device is in locked position and not under 
load as illustrated by FIG. 12. The upper end of ram 178 also includes a 
piston 186 retained by nut 188. Piston 186 includes a valve aperture 190 
for transmission of a non-compressible fluid 192, such as hydraulic oil 
from the underside of the piston to the upper side thereof when compressed 
downwardly. Accordingly, valve aperture 190 is of sufficient dimension to 
allow regulated leakage flow-through of fluid 192 at a slow rate. Fluid 
192 is retained by seal 194 and O-ring 196. 
Operation of the device of FIG. 12 includes the step of applying a load 198 
to produce a lowering of suspending assembly 173 from the upper casing 164 
to produce a gap "g" (not shown). This also results in a lowering of 
pushrod 170 and push rod cylinder 174 which also creates a gap between ram 
base 182 and pushrod head 183. Because spring 180 is compressed by the 
downward movement of pushrod cylinder 174 there is a tendency of the gap 
between ram base 182 and pushrod head 183 to close in a slow regular 
manner, dampened by the action of piston 186 which allows control of the 
rate of downward movement by forcing hydraulic fluid 192 through aperture 
190. 
If load 198 is relieved partially or completely within, for instance, 0.25 
second of initial application, ram 178 will not have moved down 
sufficiently to have any effect on pushrod 170 than to cause a minor 
tremor in release arm 172. But, assuming sufficient time has lapsed e.g. 2 
to 20 seconds, after deployment and steady descent occurs the gap between 
ram base 182 and pushrod head 183 will close up completely. When ground 
contact occurs the gap "g" (not shown) between the suspending assembly 173 
and the upper casing 164 rapidly closes as the force of load 198 on the 
device drops. However, because ram 178 has been depressed downwardly 
pushrod 170 is blocked from moving vertically upwardly in a rapid manner 
on a time scale with ground contact. This causes release of load 198 to 
occur due to the "locked" state of pushrod 170 through clockwise movement 
of release arm 172 and unlocking of release latch 200. 
After release of load 198, the gap "g" between the upper casing 164 and 
lower suspending assembly 173 becomes fully closed in the absence of a 
load. Return spring means (not shown for clarity) applies a firm counter 
clockwise torque to lever mounted release arm 172. This torque is 
communicated to pushrod 170 via pin 167 placing an upward thrust to the 
pushrod, pushrod cylinder 174, ram 178 and piston 186, all of which move 
upwardly in a slow and regular manner. After several seconds, typically 10 
to 30 seconds, release arm 172 has moved to reset position, and made ready 
for reuse. 
As with other embodiments of the invention, the device of FIG. 12 exhibits 
a constant RLP with load disconnection occurring throughout the rated load 
capacity of the device when tension falls to about 25 to about 40 percent 
of the actual load weight. 
FIGS. 13-21 relate to a further embodiment of the parachute ground 
disconnecting device. FIGS. 13-15 show ground disconnecting device 300 
having a parachute attachment means 330 located at one end of casing 302 
for securing ground disconnecting device 300 to a parachute. At the other 
end of casing 302 is load suspending assembly 308. Load suspending 
assembly 308 includes a latch 303 for securing a load to ground 
disconnecting device 300. 
Timer shaft 305 is provided with a slot 329 at one end for winding the 
timer 310 (best shown in FIGS. 13 and 16). Slot 329 is engaged by a 
suitable flat tool such as a screwdriver and wound in a clockwise 
direction. As shown in FIG. 13 and 14, casing 302 has raised bumps 306 to 
protect slot 329 from impact damage. Raised bumps 306 also serve to 
provide tactile timing reference marks for setting the time in low light 
conditions. Slot 329 can be turned to align with raised bumps 306 
corresponding to the desired time setting. The time can be set to any 
value between about 5 seconds and about 20 seconds. 
FIG. 15 shows a side elevational view of ground disconnecting device 300 
opposite to the view of FIG. 13. FIG. 15 shows casing 302 including cover 
plate 375. Cover plate 375 allows access to the inner components (not 
shown) of ground disconnecting device 300 for maintenance purposes, and is 
secured to casing 302 by a plurality of screws 380. 
FIG. 16 depicts a vertical section of ground disconnecting device 300 taken 
generally along line 16--16 of FIG. 14. The device is shown without a load 
applied. Parachute attachment means 330 is affixed to the upper end of rod 
301. Parachute attachment means 330 may be affixed to rod 301 by a 
standard clevis and pin arrangement. Rod nut 314 is affixed to the lower 
portion of rod 301. In the no-load condition shown, rod nut 314 rests at 
its lower extreme position within casing 302. Disk spring stack 313 is 
disposed between rod 301 and casing 302. Disk spring stack 313 is 
preferably a non-linear disk type spring which limits deflection of rod 
301 in relation to casing 302 when a load is applied to ground 
disconnecting device 300. 
Rod nut 314 acts on interrupter clip 312 to hold interrupter clip 312 in 
contact with escapement 311. As long as contact is maintained between 
interrupter clip 312 and escapement 311, timer 310 cannot run. 
The lower portion of casing 302 includes load suspending assembly 308. Load 
suspending assembly 308 is depicted in the latched position and includes 
latch 303 and release arm 304. Spring and pin assembly 307 exerts force to 
maintain release arm 304 in the latched position with latch 303 prior to 
ground contact by the load. 
When a load is applied to load suspending assembly 308, casing 302 moves 
downward and rod 301 moves upward out of casing 302, against the action of 
disk spring stack 313. Rod nut 314 moves upward with rod 301. Interrupter 
clip 312 is moved out of contact with escapement 311 by the upward motion 
of rod nut 314 thereby allowing timer 310 to run. Preferably, the distance 
rod nut 314 must move before interrupter clip 312 is moved out of contact 
with escapement 311 is a fraction of the total upward distance rod nut 314 
moves under normal load conditions. 
Timer 310 can be any conventional timer means and may be similar to the 
timer means described in connection with previously described embodiments 
of the invention. Timer 310 includes timer output pin 320, shown in 
greater detail in FIGS. 20 and 21. Timer output pin 320 moves toward pawl 
bell 321 under the action of push rod 327. As timer 310 runs, link means 
315 rotates in a clockwise direction about timer shaft 305 causing arm 326 
to move push rod 327 in the direction of rod 301. Timer output pin 320 is 
pivotally mounted on the lower portion of push rod 327. As push rod 327 
moves toward rod 301, timer output pin 320 is moved laterally toward pawl 
bell 321. 
As shown in FIGS. 16-18 the lower portion of rod 301 is a rack 317 
comprising a plurality of grooves or teeth 340. When no load is applied to 
ground disconnecting device 300 rack 317 resides within pawl bell 321. 
Rack 317 is centrally suspended so as to be freely vertically moveable 
within pawl bell 321 as long as timer 310 is running. The maximum stroke 
of rack 317 under fluctuating load weight should not be so great as to 
take rack 317 completely out of pawl bell 321. In other words, one of the 
grooves or teeth 340 of rack 317 is always adjacent to pawl edge 325 
regardless of the weight of the load. 
FIG. 17 shows the upper portion of pawl bell 321. Pawl edge 325 is a sharp 
inward facing machined edge which forms a circular pawl capable of being 
positively engaged with any one of the teeth 340 of rack 317. As 
previously stated, timer 310 advances timer output pin 320 toward pawl 
bell 321 as timer 310 runs. When timer 310 reaches the end of the set 
time, timer output pin 320 pushes pawl bell 321 and pawl edge 325 into 
tight engagement with one of the teeth 340 of rack 317 as shown in FIG. 
18. Once pawl bell 321 is engaged with one of the teeth 340 of rack 317, 
pawl bell 321 will move in synchronization with rack 317 and rod 301. 
FIG. 19 is a horizontal cross sectional view taken along line 19--19 of 
FIG. 17. FIG. 19 shows rack 317 and teeth 340 centrally suspended within 
pawl bell 321. Pawl edge 325 remains spaced at a slight distance 342 from 
the outer circumference of teeth 340 while timer 310 is running. 
In order for timer output 320 pin to push pawl bell 321 into engagement 
with one of the teeth 340 of rack 317, timer output pin 320 must overcome 
the resisting elastic cantilever force on pawl bell 321 exerted by music 
wire column 322, shown in FIG. 16. Music wire column 322 is disposed 
within pawl bell 321 and maintains pawl bell 321 in axial alignment with 
rack 317 until timer output pin 320 laterally deflects pawl bell 321. 
Music wire column 322 is affixed at its other end to cup pin 323. Because 
music wire column 322 is rigid in the vertical direction, cup pin 323 will 
move vertically in synchronization with pawl bell 321. During descent, 
spring 324 holds cup pin 323 in contact with cup stop 319, and limits 
downward deflection of cup pin 323. Cup stop 319 is permanently located 
within casing 302 by dog grub screw 318. 
Upon ground contact by a suspended load (not shown), bullet nosed end 309 
of cup pin 323 is driven downward, causing release arm 304 to rotate 
clockwise. Release arm 304 releases latch 303 after slightly less that 
about 10.degree. of clockwise rotation, causing the desired release of the 
load from load suspending assembly 308. 
Pawl bell 321 and cup pin 323 sustain only brief downward deflection before 
pawl edge 325 moves past timer output pin 320. Once pawl bell 321 is free 
from the laterally deflecting force of timer output pin 320, pawl bell 321 
returns to its axially aligned and centered position underneath timer 
output pin 320. The distance pawl bell 321 must travel to pass timer 
output pin 320 is preferably just slightly more than necessary to reliably 
delatch release arm 304 from latch 303. This prevents jamming of ground 
disconnecting device 300 and allows the device to be easily reset after 
having been operated under heavy load conditions. 
Preferably, Rod 301 is free to rotate about the vertical axis. About 
2.degree. of rotational freedom is desirable at the upper end of rod 301, 
where rod 301 is affixed to parachute attachment means 330. If the upper 
end of rod 301 is held too rigid, the components of ground disconnecting 
device 300 may be damaged. 
As with the previous embodiments the device of FIG. 13 exhibits a constant 
RLP with load disconnection occurring throughout the rated load capacity 
of the device when tension falls to about 25 to about 40 percent of the 
actual load weight. 
While the invention has been described in conjunction with various 
embodiments, they are illustrative only. Accordingly, many alternatives, 
modifications and variations will be apparent to persons skilled in the 
art in light of the foregoing detailed description, and it is therefore 
intended to embrace all such alternatives and variations as to fall within 
the spirit and broad scope of the appended claims.