Fail safe hold open telescoping rod

A fail safe hold open telescoping rod movable from a retracted to an extended position. A locking member coacts with telescoping tubes of the rod to allow the tubes to be fully extended by pulling the member away from the tubes and locking the same in a retracted position permitting extension of the tubes without need for manually holding the locking member. When the fully extended position is reached, the locking member automatically returns to a lock position holding the tubes in a fully extended position.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention relates to telescoping rods; and, more particularly, to a 
telescoping rod that can be selectively retracted and extended and locked 
in the extended position. 
2. Description of the Prior Art 
Telescoping rods or struts are well known in the aircraft art. Such struts 
are used, for example, to hold aircraft doors in a fully open position. 
Certain known telescoping struts are locked in a fully extended position 
by locking pins which must be inserted in place. If the operator forgets 
to insert the locking pins, or does it improperly, the struts will 
collapse and damage the aircraft or injure the operator or others. 
There is thus a need for a telescoping rod or strut which automatically 
locks in fully extended position while simultaneously maintaining the 
locking means out of locking engagement during extension. 
SUMMARY OF THE INVENTION 
It is an object of this invention to provide a telescoping strut or rod 
which is self locking in the fully extended position. 
It is a further object of this invention to carry out the foregoing object 
automatically maintaining the locking means our of locking engagement 
during extension. 
It is still further can object of this invention to carry out the foregoing 
objects where, under compressive load where it is difficult to unlock such 
struts or rods to retract the same, some of the load acting on the rods or 
struts can be taken up for ease in unlocking. 
These and other objects are preferably accomplished by providing a fail 
safe hold open telescoping rod movable from a retracted to an extended 
position. A locking member coacts with telescoping tubes of the rod to 
allow the tubes to be fully extended by pulling the member away from the 
tubes and locking or maintaining the same in a retracted position 
permitting extension of the tubes without need for manually holding the 
locking member. When the fully extended position is reached, the locking 
member automatically returns to a locking position holding the tubes in a 
fully extended and locked position.

BRIEF DESCRIPTION OF THE DRAWING 
Referring now to FIG. 1 of the drawing, a hold open rod 10 in accordance 
with the teachings of the invention is shown having a first main outer 
tube 11 and a secondary inner telescoping tube 12. Rod 10 is shown as 
being part of an aircraft 13 attached at one end thereto and at the other 
end to a door 14 pivotally mounted on the aircraft 13. 
Rod 10 may be attached to door 14 and aircraft 13 in any suitable manner. 
For example, as seen in FIG. 6, one tube, such as tube 11, may terminate 
in an integral extension portion 15 having an integral yoke 16 mounted to 
a bracket 17 by a pivot pin 18. Bracket 17 is mounted on aircraft 13. 
The inner tube 12 may be coupled to door 14 by a hook member 19 (FIG. 5) 
which includes a cavity 20 therein adapted to hook to pin 21 mounted on 
door 14. A knurled sleeve 22 is slidably mounted on tube 12. Tube 12 has 
an extension portion 23 having a slot 23' at the terminal end thereof. A 
slot 25 is provided in portion 23 with a rivet 26 extending through sleeve 
22, a bearing 27 mounted within slot 25 and a slot 28 in hook member 19. A 
similar bearing 29 and rivet 30 pivotally connects hook member 19 to 
housing 23. A coiled spring 24 is mounted in sleeve 22 normally biasing 
sleeve 22 to the position shown in solid lines in FIG. 5 wherein hook 19, 
shown in solid lines, locks onto pin 21. Thus, pulling back sleeve 22 
against the bias of spring 24 allows hook member 19 to move to the dotted 
line position releasing hook concave portion 20 from engagement with pin 
21. Of course, releasing sleeve 22 allows it, under its spring bias, to 
return back to the solid line position shown in FIG. 5. 
Referring again to FIG. 1, a hold open means 31 is shown associated with 
tubes 11, 12. As seen in FIG. 2, means 31 includes a main housing 32 
mounted to tube 11 (see FIG. 4) having a sleeve 33 (FIG. 2) mounted 
therein. Sleeve 33 has a pair of spaced openings 34, 35 therein and an 
enlarged head 36 at top. A threaded portion 37 integral with head 36 
extends through an opening 38 in the upper wall 39 closing off the top of 
housing 32 and a handle 40, having an integral inner threaded sleeve 
portion 41, is threaded to threaded portion 37. 
A pin 42 is mounted within sleeve 33 and reciprocal therein. Pin 42 has an 
enlarged head 43 at top disposed in a mating cavity 44 in housing 32. Pin 
42 also has an integral terminal end 45 extending above head 43 within 
cavity 46 in sleeve portion 41. A coiled spring 47 is mounted within 
cavity 46 normally biasing handle 40 (and, thus, sleeve 33 and pin 42) 
into the FIG. 2 position. 
Pin 42 includes an annular groove 48 therein and a pair of balls 49, 50 are 
mounted in groove 48 and aforementioned openings 34, 35 in sleeve 33. As 
seen in FIG. 2, inner tube 12 extends through an opening 51, 32 and may be 
hexagonal in configuration. 
Housing 32 also includes a pair of spaced chambers 52, 53 (FIG. 3) on each 
side of housing 32. A pair of pistons 54, 55 are reciprocal in each 
chamber 52, 53. Each piston head 57 is of relatively the same diameter as 
chambers 52, 53 so that they reciprocate therein. 
Piston rods 56 extend through suitable openings 58, 59 in housing 32 and 
coiled springs 60 are mounted in each chamber 52, 53 between the upper 
surface 62 of housing 32 and piston head 57, surrounding rod 56, normally 
biasing pistons 54, 55 to the FIG. 2 position. 
The upper terminal ends 61 of each piston rod 56 are receivable in caps 62 
integral with wall 39. As seen in FIGS. 2 and 3, wall 39 is retained 
between sleeve 41 and head 36 so that, when handle 40 is pulled up 
inwardly from the FIG. 2 to the FIG. 3 position, wall 39, and thus rods 56 
press-fit or the like into caps 62 move upwardly against the bias of 
springs 60. 
As seen in FIG. 4, tube 12 has an elongated groove 63 (seen also in FIG. 3) 
in which the lower end 64 of pin 42 rides in groove 63. Also, a raised 
portion 65 (FIG. 4) is provided along groove 63 for reasons to be 
discussed. 
Referring now to FIG. 2, the locked position of pin 42 with respect to tube 
12 is shown with pin 42 extending into hole 66 through tube 12. Balls 49, 
50 in groove 48 are locked in openings 34, 35. 
When it is desired to extend tube 12 and pull it up to the FIG. 1 position, 
handle 40 is grasped and pulled upwardly against the bias of springs 60 
thus also pulling upwardly sleeve 33 (due to the coaction with balls 49, 
50) and also pulling pistons 54, 55 upwardly as seen in FIG. 3. Balls 49, 
50 enter cavity 44 and the lowermost end 64 of pin 42 enters groove 63 in 
tube 12 (see also FIG. 4). Tube 12 can now be extended out of telescoping 
engagement with tube 11 in the direction of the arrow in FIG. 4 with end 
64 riding in groove 63. Spring 47 serves to bias pin 42 downwardly and 
retain the same in groove 63. 
Tube 12 is extended in the direction of the arrow in FIG. 4 until pin end 
64 abuts against raised portion 65. The sides 67, 68 thereof are tapered, 
as seen in FIG. 4A, so that pin end 64 goes up side 67 and reaches the 
apex 69. At the same time, balls 49, 50 enter groove 48 thus locking pin 
42 in the FIG. 4A position. Springs 60 and 47 are of course biasing pin 42 
downwardly. 
As tube 12 is continued to be pulled in the direction of the arrow in FIG. 
4A, pin end 64 rides over raised portion 65 (FIG. 4B) until pin 42 reaches 
the hole 70 through tube 12 (similar to hole 66) adjacent the terminal or 
fully extended position of tube 12. Springs 60 and 47 bias pin end 64 down 
into hole 70. 
It can be seen that, by pulling upwardly on handle 40, balls 49, 50 lock 
pin 42 in a hold out position. When pin end 64 rides over raised portion 
65, the pin 42 is forced upwardly (FIG. 4A) releasing balls 49, 50 but 
springs 47, 60 force pin 42 downwardly (FIG. 4B). Pin end 64 now snaps 
into hole 70 in the fully extended position. (identical to the view shown 
in FIG. 2). 
Although a pair of telescoping tubes 11, 12 are disclosed, obviously a 
plurality of such tubes may be provided. Also, the use of the invention is 
illustrated in conjunction with the door of an aircraft, obviously rod 10 
can be used in a variety of applications. 
Since, under compression load, it is difficult to unlock such rods or 
struts when in the fully extended position, as shown in FIG. 1, a double 
safety mechanism is provided by use of the automatic latching mechanism 
shown in FIG. 5 and herein described. Pulling back on collar 22, due to 
the slots 25, 28, takes up some of the load allowing the locking means of 
FIGS. 2 to 4 to be unlocked. 
It can be seen that there is described a fail safe hold open telescoping 
rod or strut which can be operated with one hand to extend the same, then 
automatically locks in fully extended position. The rod can then be 
quickly and easily unlocked to retract the telescoping tubes. Although a 
preferred embodiment of the invention is disclosed, variations thereof may 
occur to an artisan and the scope of the invention should only be limited 
by the scope of the appended claims.