US2889895A

US2889895A - Pneumatic energy absorber

Info

Publication number: US2889895A
Application number: US553818A
Authority: US
Inventors: John E Snow
Original assignee: Individual
Current assignee: Individual
Priority date: 1955-12-19
Filing date: 1955-12-19
Publication date: 1959-06-09
Anticipated expiration: 1976-06-09

Description

2 Sheets-Sheet 1 'J. E. SNOW PNEUMATic ENERGY ABSORBER (www. m@ J M June 9, 1959 Firled Dec. 19, 1955 June 9, 1959 J. E.' sNow PNEUMTIC ENERGY ABSORBER 2 Sheets-Sheet 2 Filed Dec. 19, 1955 MQP JDSSH- M w W d Nm.

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m WNV 1M. m fmN NN" United States Patent 2,889,895 PNEUMATIC ENERGY ABsoRBER John E. Snow, Fairborn, Ohio Application December 19, 1955,Serial No. 553,818

Claims. (Cl. 18S-86) (Granted under Title 35, U.S. Code (1952), sec. 266) The invention described herein may be manufactured and used by or for Ithe Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

My invention relates to pneumatic piston drives and more particularly to pulling one piston by means of driving another.

Although not limited thereto, my invention has particular usefulness in the field of returning a piston in a drag tube to its initial starting position such as the piston described in my copending application, Serial Number 525,754, led August 1, 1955, and now Patent No. 2,860,732.

It is well known to provide drag means for aircraft deceleration purposes comprising a piston reciprocating in a tube wherein a piston is pulled against a predetermined constant air pressure or is pulled through a heavy uid such as water to provide a constant fluid friction drag. The problem of returning these pistons to the initial starting position has presented diiculties to the industry. It is obvious to return the piston by means of a cable attached to the rear of the drag piston which is wound on a winch or the like. However, the cost of maintenance and protection against weather is high and the relatively slow operation is unsatisfactory.

It is the principal object of my invention to provide al pneumatic pull which will aggravatel the drag of the principal piston during its forward operation and which will ,rapidly return the principal piston to its initial position.

It is a further object of my invention to provide a means of preventing the inadvertent return of the principal piston.

It is a further object of my inventionl to provide electrical control means for the return of the principal piston by means of the pull of a second piston.

It is a fur-ther object of my invention to provide a piston adapted to reciprocate within a tube whereby the piston is forced to move within the tube in one direction by being attached at one side to an exterior object such as another piston and in the other direction by means of air under pressure being introduced into the tube against the same side of the piston thereby pulling with it, the exterior pistons.

My means of accomplishing the foregoing objects vwill be more readily apprehended by having reference to the accompanying drawings in which:

Figure 1 is a vertical sectional view of my pneumatic pull at initial starting position;

'Figure 2 is a vertical view partly in section showing my pneumatic pull in the position to be returned to the initial starting position;

2 Figure 3 is a cross sectional view taken on lines 3 3 of Figure 1.

Similar numeralsrrefer to similar parts throughout the specification.

As shown in the drawings, I provide a cylinder 2 in which a piston 4 is adapted to reciprocate. I provide seal'- ICC v ing rings 6 to hold the piston in fluid-tight relation to the inside 8 of the cylinder 2. A cable 10, which may be a 5 I provide a simple bite 14 of the cable 10 bent aroundapin 16 which is inserted in a bifurcated stud 18. Not

shown in the drawings, but understood as being attached to the cable 10, may be any of the well known drag plugs or pistons referred to above. The cable may be sealed 10 at the end 20 of the tube 2 by means of a grommet 22 vinserted in a recess 24 cut into a boss 26 which is apertured at 28 to permit the passage of the cable 10. In

this form of seal a cap 30 is placed over the grommet 22 to hold it in position. This cap 30 may be attached by being threaded into the aperture 24 or by any other suitable means. I provide a vent in the rear plate 23 as ishown.

I provide a brake indicated generally as 32 which may be attached to end of the cylinder 2 with a vibration 20 dampener 34 inserted therebetween. I provide that when the pistonv 4 has traveled forwardly through the tube 2 as far as possible, the lingers 5 and 7 may contact the inner side of a plate to prevent further passage of the piston 4. This permits the port 21 to remain uncovered .25 at all times.

35 reverse direction (see Fig. 2). This valve 38 may be so constructed that it will be responsive to multiple pressure settings, if desired. In practice I prefer to provide that the valve 38 opens at pressure in excess of 1,500 p.s.i. This provides a constant resistance against the forward 40 travel of the piston 4.

The only force tending to retard the passage of the piston 4 in this direction is the air under pressure as itescapes to the accumulator. This force aggravates the inertia of the exterior piston or whatever is attached to i end of the cable 10. lf it is an exterior drag the other -piston, the force exerted against the travel of the piston augments the drag and is considered benelcial.

As shown in Figure 1, by closing the switch 74 the solenoid valve 78, which is normally closed, is opened and air under pressure is permitted to pass from the accumulator 40 through pipe 36 to port 21 into the tube '2 to bear against the forward side of the piston 4 and force its movement in a lateral direction. Of course, the pressure from the accumulator 40 may be controlled by a multiple setting switch, if desired.

If it is desired to vent the air in the tube 2 to permit lrepairs or for any other reason, theA switch 72 may be closed and the solenoid valve 94, which is normally closed, will `open and vent the air in the tube 2. As shown in the drawings, I have provided a selfenergized brake 32 to prevent inadvertent lateral movei "ment of the cable 10 after the piston 4 has traveled forwardly down the tube 2.

In the brake 32 I provide a pair of

brake shoes

42 and 44 which have tapered shoulders 54 and 56 as shown Ain the drawings. The tapered shoulders 54 and 56 ride :against rollers 58 set in slots 59 held by pins 61 in the brake housing 33. The

brake shoes

42 and 44 have longitudinal grooves 46 and 48 which are lined with brakev linings-50 and 52 and are adapted to engage the cable 10 as shown in Figure 3. I provide that the

brake shoes

42 and 44 embracev the cable 10 in a sutliciently rm Pad-termed June 9, 1959 p 3 manner so that if the cable moves backwardly, the

brake shoes

42 and 44 move forwardly a short distance against the rollers 58 and cramp the cable 10 to prevent further movement. This is accomplished by the

brake shoes

42 and 44 moving in the direction of the force against the piston 4 carried by the cable 1G. The tapered shoulders 54 and 56 are forced by the rollers 58 tol cramp the cable 10 in such a manner that the cable 10l 4is prevented from any further travel in that direction. Thus I have provided a self-energized brake which holds the piston 4 against inadvertent return.

In order to free the cable 10 when desired, I provide pistons 60 and 62 inside of cylinders 64 and 66 connected to the

brake shoes

42 and 44 respectively by rods 68 and 70. By means of appropriate piping `as shown, I provide that air may be introduced at the forward side of the pistons 60 and 62 to force the

brake shoes

42 and 44 to free the cable 10. I accomplish this when the switch 74 is closed. Besides opening the valve 78,-v it opens a normally closed valve 76 as shown in Figure il. The valve 76 is a normally closed three-way solenoid valve and is intended to permit air under pressure to pass from the accumulator 40V in the same manner as valve 78 when the switch 74 is closed. When the valve 76 is closed (the switch 74 being open) no air is permitted to pass to the

pipes

80 and 82. When the switch 74 is closed, the valve 76 permits air to pass from the accumulator 40 through the

pipes

80 and 82 thereby forcing the pistons 60 and 62 to move rearwardly, unseating the

brake shoes

42 and 44. The valve 76 is so constructed that when it is closed to prevent air from passing through it from the accumulator 40, the

pipes

80 and 82 are vented to the atmosphere through it.

If it is desired not to depend upon the self-energized features of my brake 32, I provide electric means to kick-in the brake should the cable 10 move rearwardly before desired. As shown in Figure 2, I provide a centrifugal switch 92 which may be any of the well known ball governors. I have shown schematically a simple rotating ball governor switch 92 which is normally opened when the cable is at rest. The arrangement shown in Figure 2 includes an idler wheel 96 in contact with the cable 10. I provide that the idler wheel 96 contains an override clutch which frees the wheel 96 from turning the shaft 9S except when the cable 10 moves in a rearward direction. The shaft 98, when engaged, rotates the gears 99 which in turn rotate a governor 100. As the balls rise due to any return movement of the cable 10, the contacts 102 which are normally below the contact 104, move upwardly and mate with the contact 104 thereby opening a three-way solenoid valve 90 (similar to valve 76) which instantly passes air from the accumulator 40 to the rear of the pistons 60 and 62 through the

pipes

84 and 86. This will cause the brake 32 to set and prevent further movement of the cable 10. The cessation of movement of the cable 10 will cause the contacts 102 to fall out of contact and the system will vent when the three-way solenoid valve 9i) goes normally closed. The venting of the three-way solenoid valve 9@ relieves the air pressure in

pipes

84 and 86, similar to the operation of valve 76 as set forth above.

In order that the governor switch 92 does not operate to energize the brake 32 during the retraction of the piston 4 when it is desired to force the piston 4 in a rearward direction through tube 2,v I provide that the electric switch 74 is so constructed that when it is closed in order to open the valve 78 and the Valve 76 to force the retraction of the piston 4 and the release of the brake 32, no current is supplied to the governor switch 92` and consequently even though it calls for the opening of valve 90, there is no current supplied for this purpose. HoW-' ever, on the other hand, when the switch 74 is thrown from its closed position over to the opposite position, it is clear that current will ow to the governor`92 and it thereby becomes energized and prevents the rearward movement of the cable 10.

I have set forth the details of my invention which provides pretension force on the cable 10 when it is in the position shown in Figure 1 and also permits the prepositioning of any drag, plug, or the like that may be attached to the other end of the cable 10. By adjusting the air pressure in the tube 2, I am able to position the piston 4 as desired along the tube 2 which will provide the pretensioning and the pre-positioning features described above.

Since I have provided both electrical and self-energized braking means, I have provided a fail-safe system that quickly will retract any drag or plug presently in use. For example, I have found in practice that with a tube of approximately two inches (2) in diameter several hundred feet long, I am able by means of my invention to retract in twenty seconds, a drag plug that has traveled two thousand feet in its tube resisting thirty million foot pounds of energy.

My device described above has the added Afeature of being temperature compensated since it accommodates for elongation of the cables due to thermal expansion or contraction. The system is also capable of being preset with multiple pressure settings from the accumulator 46 as described above.

Of course the system will perform satisfactorily without the brake governor and may be operated without any brake mechanism if desired.

Having described my invention what I regard as new and desire to protect by Letters Patent is:

1. A pneumatic pull comprising a cylinder adapted to be substantially airtight, a piston adapted to reciprocate in said cylinder, said piston connected to means to pull it forwardly through said cylinder, means to force said piston in the opposite direction in said cylinder, said last rnamed means including means adjacent the forward end of said cylinder for introducing air under pressure into said cylinder to move said piston in said opposite direction and means automatically engageable with the piston connected pull means lto prevent further travel of said piston in said opposite direction once it comes to rest after its forward movement in said cylinder, said means for preventing further travel of said piston in said opposite direction after its forward movementhas ceased comprising a self-energizing brake formed of a plurality of brake shoes adapted to clamp said pull means and toj wedge said pull means to prevent further movement of said pull means in said rearward direction when said piston moves in said opposite direction after ceasing its forward movement, wherein the brake is electrically initiated to wedge said pull means, said electrical initiating means comprising an energizing circuit, switch means in said circuit for opening and closing said circuit, a 'centrifugal switch in said energizing circuit actuated by said pull means, said switch adapted to be normally open when said pull means is at rest, said switch connected electrically when closed to an electrically operated valve in a piping system, said valve responsive to current in said energizing circuit from said centrifugal switch and adapted to open to pass air under pressure from an outside source to a plurality of tubes in the rear of a plurality of pistons adapted to reciprocate in said tubes, said pistons connected to said brake shoes and adapted to force said brake shoes to wedge said pull means, and electrical means to release said air under pressure'in the rear of said plurality of pistons whereby said brake is loosened from said pull means.

2. In a pneumatic pull device, a cylinder having av fixed forward end closure and a fixed rear end closure, a piston reciprocatable in said cylinder, elongated flexible pull means connected to saidr piston and extending through lsaid forward end closure to pull said piston from saidV rear end-closure forwardly toward said forward end closureandcontrolmovement of said piston from said forward end closure toward said rear end closure, pressure uid supply means, conduit means connecting said pressure supply means to the forward end of said cylinder, a luid pressure accumulator in said conduit means connected to said pressure supply means for supplying pressure uid into the forward end of said cylinder to move said piston toward said rear end closure and receive pressure uid from said cylinder when said piston is pulled forwardly toward said forward end closure of said cylinder by said elongated exible pull means, clamping means at the forward end of said cylinder, movable into and out of clamping engagement with said elongated flexible pull means, pressure operated means connected to said conduit means for moving said clamping means into clamping engagement with said elongated flexible pull means to control movement of said piston and pull means toward said rear end closure of said cylinder, pressure operated release means connected to said conduit means for moving said clamping means to relieve clamping pressure thereof on said elongated exible pull means, means for selectively controlling said pressure operated means and said pressure operated release means, check valve means in said conduit means between said pressure accumulator and said cylinder opening toward said pressure accumulator, said conduit means including a bypass conduit around said check valve means connected between said pressure accumulator and said cylinder, valve means in said bypass conduit means, separate uid pressure operated means connected to said clamping means for moving said clamping means into and out of clamping engagement with said elongated flexible pull means, separate conduit means connected between said pressure accumulator means and each of said separate uid pressure operated means, separate valve means in each of said separate conduit means for controlling pressure Huid from said accumulator to each of said separate uid pressure operated means for selectively controlling said clamping engagement of said clamping means on said elongated flexible pull means for controlling movement of said piston and pull means in said cylinder between said end closures.

3. Apparatus as claimed in claim 2, including electrically operable actuating means for said valve means, and switch means therefor for simultaneously actuating said separate valve means to admit pressure uid from said pressure accumulator to the forward end of said cylinder to move said piston toward said rear end closure and to admit pressure fluid from said pressure accumulator to said separate fluid pressure operated means for moving said clamping means to relieve the clamping engagement thereof on said pull means to permit movement of said p'iston from said forward end of said cylinder toward said rear end of said cylinder under the influence of pressure uid in said cylinder.

4. In a pneumatic pull device, comprising an elongated cylinder having a closed rear end and a closed forward end, a piston reciprocatable in said cylinder between said forward end and said rear end, means for supplying uid pressure to said cylinder adjacent said forward end for moving said piston toward said rear end, an elongated flexible pull member connected to said piston and extending longitudinally through said cylinder and said forward end for moving said piston from said rear end toward said forward end, packing gland means between said pull means and said forward end for preventing escape of pressure uid between said pull means and said forward end, self energizing clamping means disposed in front of said forward end for braking engagement with the opposite sides of said pull means incident to movement of said piston and pull means toward said rear end of said cylinder, fluid pressure operated means connected to said self energizing clamping means for moving said self energizing clamping means to release position to release said pull means, a pressure accumulator adapted to be supplied with a pressure lluid at a predetermined pressure, a first pressure conduit establishing communication between said accumulator and said cylinder in the forward end thereof, check valve means in said conduit opening toward said accumulator, a second conduit in communication between said accumulator and said forward end of said cylinder bypassing said first pressure conduit, valve means in said second conduit for controlling delivery of pressure fluid from said accumulator into said cylinder between said forward end and said piston, a third conduit means connected in communication between said accumulator and said fluid pressure operated means for releasing said self energizing clamping means, separate vvalve means in said third pressure conduit means for controlling uid pressure between said accumulator and said fluid pressure operated means for releasing said clamping means, and valve actuating means for opening said last mentioned valve means while said piston is in the forward end of said cylinder to disengage said clamping means and admit uid pressure to said cylinder to move said piston and pull means toward said rear end of said cylinder.

5. Apparatus as claimed in claim 4 including second uid pressure operated means for urging said self energizing clamping means toward self energizing clamping engagement with said pull means, la fourth pressure conduit connected between said accumulator and said second iluid pressure operated means for supplying operating fluid pressure thereto, independently of the other conduit means, valve means in said fourth pressure conduit means normally closing said fourth conduit means, speed responsive means engaging said pull means and operable to open said last Valve means during movement of said piston and said pull means toward said rear end of said cylinder at a speed in excess of a predetermined nate of travel of said piston to engage said clamping means with said pull means to limit the rate of travel of said piston and pull means toward said closed end of said cylinder.

References Cited in the le of this patent UNITED STATES PATENTS 787,374 Graham Apr. 18, 1905 840,877 Steedman Jan. 8, 1907 1,956,110 Turrettini Apr. 24, 1934 2,001,988 Temple May 21, 1935 2,632,425 Grover Mar. 24, 1953 2,765,054 Rossman Oct. 2, 1956 2,767,601 Reed Oct. 23, 1956 FOREIGN PATENTS 1,077,611 France May 5, 1954