US2857889A - One stroke thruster with speed reducer - Google Patents

Description

Oct. 28, 1958 .A. M. s'rc'r'r ET AL ONE STROKE THRUSTER WITH SPEED REDUCER Filed March 6, 1957 The invention described herei'nmay be manufactured? and used by or for the Governmentffory governmental pur` poses without payment of any royalty thereon.

This invention relates to a mechanism for movingy a seat on a high speed airplane prior to` its being ejected forcibly therefrom. ment must be `Within aprescribed range-from the lstandpoint of protecting personnelyagainstjolt and protecting.

the plane from dangerous structural over-loads. Heretofore, cartridge actuated catapults and` thrusters forvarious purposes have been used, but such devices -have not been appropriate within the conned` andcranlpedl space avaiiable in a plane for moving the seatsbecause the pressures available for short movements havebeen4 either unsuitable or the speeds of movements too rapid.

An object of this invention is to` provide a cartridge actuatedA thruster for moving a seat in a planetyregardless of the adjusted position 'of the seat and for other uses requiring comparatively short travel at safe speeds; AV

further object is to provide such a thruster havingasingle l stroke speed reducing mechanism: compalctl'y embodied" therein which acts to closely control speeds over the load and temperature range.

According to this invention, a cartridgeactuat'ed:piston operates a secondpiston by an interposed liquid'.- lA checkf valve on the second piston allowsdiquid" tollow into a restricted space onan opposite: sideofasecond piston for cushioning its movement; Durin'g'movemen't' of the piston and integral pistonrod, the check valve' is closed anda highpressure is developedon'the'lliquid in such1 restricted spaceibyvlimiting liquid escape"throughV a"` constricted passageway; whoseJY cross sectional area" determines toalarge extent the speed: of the second* piston and the thrustoutput.A In addition,A the burningy rate of the `propellant is `controlled withirespect tol the stroke -and mass being positioned.

the space between the pistons where the pressure is lower than that in said `restricted space.

The two figures of the drawing are aflongitudinal cross section ofa preferred embodiment of this invention, Figs 1A and 1B being at opposite ends ofthe same thruster. l

Referring to the drawings, the cylinder 10 is provided at its `left end with a tting 11 to which may be attached any convenient source ofpressure such as a gaspressure cylinder or some cartridge device capable of delivering the appropriate pressurewof about'LOOO- lbs/sq. in. to the iiringpin 13. A shear pin 12 releases the tiring pin for 'movement `as soon as adequate-pressure exists onthe left side ofthe ringpin'. As shown inthe drawing; the ring pin is provided with a suitable packing around its periphery and after rupture of the shear pin 12, the tiring pin 13 impinges upon the primer 14 and related parts causing the propellent charge 15 to be set oft. After being set off, the products of combustion from the cartridge 15 fill the space 16 within the skirt of the piston 17 and move the piston to the right. This piston is also provided with suitable packing 18 as illustrated.

lt is known thatthe speed rot-such seat move Instead of'- escapingl' t to the outside, liquid from thef constriction isfd laclc'tol States Patent ICC A ileXible container 19 holds an oily silicone liquid-of` low Viscosity under wide temperature changes. The parti-cular liquid selected has such nearly uniform viscosity throughout a temperature range fromplus Fahrenheit to minus 65 Fahrenheit; Movement' of the rst piston 17 to the right causes similar movement-to" the right of the liange 21 having attachedthereto a' tube `22 fitting over antinner'tube 24 secured to thev second piston. Under suitable pressure a snap ring 23, shown a's being located on the inner tube 24, is moved out of placeV and the outer tube continues its movement tothe rightv exposing an end of the inner tube `as illustrated.. On the end of the inner tube is an arcuate shaped punch 25 adapted to pierce the exiblecontainer 19' with an arcuate shaped cut so that a hap on the bagexists through which the liquid is then able to escape and ow` to the ball check valve 26. This ball check valve is` shown in `the drawing as being threadedly secured within a second` piston 27, the right end of which could be designated as a rod 28. The terms piston and rod as used herein are Abroad enough to cover a plunger as illustrated-orother equivalent. Theange 21 contains a4 peripheralclearance space 29 for purposes disclosed hereinafter. Thepiston 27 is provided with appropriate packing 30. The springv 31 cooperates with the `ball check valve 26 and with the plug 32 to control the stress in the spring. A number of passageways 33 in the' inner tube 24 are connected with a similar number of passageways 34'in the piston 27 `by means of a circular depression or undercut -35`in an outer portion of the inner tube 24.

The'piston and piston rod have `a` hollow central por` tion 36 for the purpose of lightening their weight.- 'In the"thruster illustrated a shear pin 37 at the right end of the piston rod ruptures on application of the pressure developing about 2,000 lbs. force, and after this rupture thepistonrod is forced outwardly. The right end 38 of the pistonrod is shaped convenientlyA for cooperation with whatever type of load it engages duringany portion of its stroke; in the embodiment illustrated this right end is shown' as being rounded. A' cap 39` is threade'dor otherwise secured to the cylinder and is provided with appropriate packing 40 between the pistonv rod 28"'and the inner wall of said cap. A Y 1' A"`restricted space 41A is provided between the insidey ofthe cylinder 10 and the outside ofthe piston' rod `28,1 this space being available for4 development of a high pressure on liquid after it has passed the ball check valve illustrated. Because the ends of this restrieed space 41 are ofsmall cross sectional area, the outward ymovement` oflthe piston and piston rod tends to compressliquid within: this restricted space `41=and develop'a higher than usual pressure after the ball check valve has closed. Within the second piston 27, and at the left end of the restricted space 41, is a constricted passageway M'throgh which liquid under pressureinthe space 41n`1aybeffor`ced. The` size of`- the constricted passageway `42 is Aefe'ctiveiri' controlling'lthe rate of outward travel' of the piston`a`rid pistonirod' andthe thrust output. at theleft end of the restriced space t1 has been moved totheright and impinges upon the shoulder ll4"sh'ovvn `in` thecap' 39,' engagement of these two 'shouldersacts as anabutment to stop or limit outward m'ovemer'iti of the piston and fpistonrod.

Thus; in` operation, tiring of'thefcartridgel v15`moves the piston 17 to the right, imposing pressure upon the container 19 and also upon the ange 21. As the flange is moved to the right, the arcuate punch 25 perforates the container allowing liquid to flow to the ball check valve 26 in the piston 27. This check valve opens upon attainment of a predetermined pressure allowing liquid to ow radially outward through the passageways 33 and When `a` shoulder "43 34 into the restricted space 41 between the piston rods and the cylinder. As the piston and piston rod are moved to the right, the force causing the displacement becomes sufiicient to rupture the shearing pin 37. After the rupture of the shear pin 37, the piston and piston rod-continue their movement to the right placing pressure on the liquid in the restricted space 41 and raising its pressure to a value higher than that on the input side of the check valve. The rate of outward movement of the piston and piston rod depends on the cross sectional area of the constricted passageway 42 through which liquid is allowed to move rearwardly or to the lett, filling the space to the left of the piston 27 and passing around the flange 21 and into and around the space occupied by the flexible container which by this time will have become compressed to contain folds and other irregularities. Also, the rate is substantially retarded regardless of whether the load is encountered at the beginning or end of stroke.

Among the advantages of this invention may be mentioned the provision, for the first time, of a reduction of speed for a one-stroke thruster operated by a cartridge. High pressure is developed in the liquid in the space 41 due to the small annulus area at the ends of this space, this area being smaller in cross sectional area than the effective area of the piston subject to the incoming liquid from the rubber bag. A desirable feature of the present construction is the absence of any leakage of liquid or gas to the outside, both pressures being contained within the package or outer casing. An especially noteworthy feature is the adaptability of the present thruster for functioning under extreme cold to which an airplane may be subjected at great heights. The piston 17 may be called a floating one inasmuch as it is not directly connected to the piston rod 28. When a tloating piston is used in the illustrated combination with a continually open constricted passageway 42, the floating piston will have a shorter stroke than the main piston 27 due to these two pistons moving farther apart as they move forward, and as liquid from the restricted high pressure chamber 41 is fed into the low pressure chamber between them occupied by the container 19. When an aircraft seat is to be moved and the seat position is adjustable the thruster can start with or without load, contact the seat without excessive jar and then position it without exceeding the permissible velocity, acceleration,

or rate of change of acceleration. A speed of 6 to l2 feet per second is desirable for such a seat. The contents of the container are adapted for use under a wide range of temperature because any expansion in the flexible container need not be objectionable. The foregoing advantages of a floating piston are made possible by the addition to the total length of the thruster of an amount no greater than the axial length of the floating piston. The shorter stroke of the floating piston makes for a more desirable initial to final expansion ratio of the propellent sion and providing a cutting edge for puncturing said container in response to said movement, a power applying member fixed to said second piston and arranged to form within said casing a space having a transverse area substantially less than the transverse area of said second piston, a valve arranged in said central opening to admit some of said fluid to said space and to be closed in respouse to a pressure increase in said admitted fluid, and a restricted passageway extending longitudinally of said second piston for cushioning the effect of said increased y liquid pressure.

ti (l 2. A thruster including a casing enclosing means for producing a fluid pressure, a flexible container enclosing a fluid, a member having an opening terminating in a first tubular extension, a first piston arranged to move said container and said member in response to said pressure, a second piston having a central opening terminating in a second tubular extension extending into said first tubular extension and providing a cutting edge for puncturing said container in response to said movement and applying said fluid to said second piston, a power applying member fixed to said second piston, and means for fixing said power applying member to said casing until the pressure of said applied fluid has attained a predetermined value.

3. In a thruster having a casing enclosing means for applying an operating pressure and for releasing a fluid in response to said pressure, the combination of a piston movable in response to said released fluid and having a central opening, a power applying member fixed to said piston and arranged to form with said casing a space having a transverse area substantially less than the transverse area of said piston, a valve arranged in said central opening to admit operating fluid to said space and to be closed in response to a predetermined increase in the pressure Aof said admitted fluid, and restricted passageway means extending longitudinally of said piston for controlling the etect of said increased liquid pressure on said power applying member.

4. In a method of operating a thruster having a casing which encloses a piston fixed to a power applying member, the steps which include generating an operating pressure, utilizing said pressure to a fluid to said piston, confining some of said fluid so that its pressure is increased in response to movement of said piston, and ventying said confined fluid in response to said increased pressure at a rate dependent on the desired thrust of said power applying member. y

5. In a method of operating a thruster having a casing which encloses a piston fixed to a power applying member, the steps which include generating an operating pressure, utilizing said pressure to a fluid to said piston, confining some of said fluid so that its pressure is increased in response to movement of said piston, and venting said confined fluid to the rear of said piston in response to said increased pressure at a rate dependent on the desired thrust of said power applying member.

References Cited in the le of this patent UNITED STATES PATENTS 2,469,660 Martin May 10, 1949 2,539,720 Bender Jan. 30, 1951 2,558,810 Bent July 3, 1951 2,618,600 Moreton Nov. 18, 1952 2,775,605 De Benneville et al. Dec. 25, 1956 FOREIGN PATENTS 548,727 Great Britain Oct. 22, 1942 676,805 Great Britain Aug. 6, 1942

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