US3448662A - Fail-safe piston and cylinder arrangement - Google Patents

Description

June 10, 1969 E. E. MUELLER 3,448,662

FAIL'SAFE PISTON AND CYLINDER ARRANGEMENT Filed Dec. 9, 1966 Sheet of 3 I N VENTOR.

June 10, 1969 MUELLER I 3,448,662

FAIL-SAFE PISTON AND CYLINDER ARRANGEMENT Filed D80. 9, 1966 Sheet 2 GM. wm v E L M m 5 w 5 I I If 11171002 ,1! If r HTTOPNEYS I June 10, 1969 M E 3,448,662

FAIL'SAFE PISTON AND CYLINDER ARRANGEMENT Filed Dec. 9, 1966 7 Sheet of 3 United States Patent 3,448,662 FAIL-SAFE PISTON AND CYLINDER ARRANGEMENT Ernest E. Mueller, Kew Gardens, N.Y., assignor to Ozone Metal Products Corp., Ozone Park, N.Y., a corpora tion of New York Filed Dec. 9, 1966, Ser. No. 600,636 Int. Cl. F15b 15/17, 11/08; F16b 13/04 U.S. Cl. 91415 9 Claims ABSTRACT OF THE DISCLOSURE Background of the invention There are known in the prior art piston and cylinder assemblies for lowering and raising heavy loads and for positioning the supported member in a desired position. One application of such devices is the support of a cargo aircraft ramp, the lowered position of which is determined by the nature of the terrain on which the operation is to be performed. Installations of this type usually employ a pair of assemblies, the cylinder of each of which is carried by the aircraft body and the piston of which is secured to the ramp. Fluid under pressure is supplied to the cylinders to lower and to raise the ramp as required.

It will readily be appreciated that, in an installation of the kind described, a loss of operating pressure creates an extremely dangerous condition since it results in the ramp falling substantially freely to the ground. Attempts have been made in the prior art to overcome this problem by providing an assembly which fails safe. These systems may, for example, have an incremental mechanical lock to ensure that the supported member, such as the ramp, will not fall freely in the event that pressure is lost. Fail-safe assemblies of the prior art are relatively complicated and are consequently expensive. Moreover, they are not all as certain in operation as is desirable. They incorporate an undesirable backlash and do not provide as stiff a system as may be required.

In most installations of the prior art a mechanical device such as a winch is provided for moving the supported member in the event of a pressure failure. Such a procedure in the prior art, however, is relatively complicated and difiicult owing to the fact that no means is provided for ensuring that the supported member will be moved to the position it occupied under the action of the hydraulic system before failure.

Summary of the invention I have invented a fail-safe piston and cylinder arrangement which overcomes the defects of assemblies of the prior art pointed out hereinabove. My assembly is relatively simple in construction and operation. It is inexpensive to construct as compared with systems of the prior art. It is certain in operation. It has no backlash and will lock in precisely the position of the supported member upon failure of pressure. My assembly includes means for ensuring that mechanical operation after failure will position the supported element in precisely that position it occupied before fluid pressure failure.

One object of my invention is to provide a hydraulic piston and cylinder arrangement which fails safe.

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Another object of my invention is to provide a failsafe piston and cylinder arrangement which overcomes the defects of arrangements of the prior art.

A further object of my invention is to provide a failsafe piston and cylinder assembly which is simple in construction and certain in operation.

Still another object of my invention is to provide a fail-safe piston and cylinderarrangement which is relatively inexpensive as compared with systems of the prior art.

Yet another object of my invention is to provide a fail-safe piston and cylinder arrangement which rernembers the position to which it had been moved by the hydraulic system before failure thereof.

Other and further objects of my invention will appear from the following description.

In general my invention contemplates the provision of a hydraulic piston and cylinder assembly in which fluid under pressure is applied to the head side and through a one-way poppet valve to the rod side of the assembly for one direction of movement of the supported member. For movement in the other direction I apply fluid under pressure to the rod side and connect the head side to the exhaust. I may provide my assembly with an auxiliary slave piston which remains in the position to which it has been moved by the main piston when the main piston is moved mechanically from that position after a failure.

Brief description of the drawings In the accompanying drawings which form part of the instant specification and which are to be read in conjunction therewith and in which like reference numerals are used to indicate like parts in the various views:

FIGURE 1 is a fragmentary partially schematic view illustrating one application of my fail-safe piston and cylinder arrangement.

FIGURE 2 is a sectional view of the installation of FIGURE 1 taken along the line 22 of FIGURE 1.

FIGURE 3 is a sectional view of one of my fail-safe piston and cylinder arrangements taken along the line 3-3 of FIGURE 1 and drawn on an enlarged scale.

FIGURE 4 is a sectional view of the fail-safe piston and cylinder arrangement shown in FIGURE 3 taken along the line 44 of FIGURE 3 and drawn on an enlarged scale.

FIGURE 5 is a fragmentary sectional view of an alternate embodiment of my fail-safe piston and cylinder assembly.

Description of the preferred embodiments Referring now to FIGURES 1 and 2, by way of example I have illustrated an installation wherein two of my assemblies, indicated generally by the reference characters 10 and 12, are adapted to support a ramp 14 carried .by a hinge .16 on the body 18 of an aircraft or the like. Each of the assemblies includes a cylinder 20 and a piston rod 22, the lower end of which carries a clevis 24 which receives a bracket tongue 26 to which it is pivotally secured by a bolt 28. Each assembly further includes a spherical bearing housing 30. Bolts 32 or the like secure a mounting flange 34 on housing 30 to a bracket 36 carried by the body 18.

I provide each of the assemblies 10 and 12 with a fitting 38 connected by a line 40 to the head end inlet port fitting 42 of the assembly. Another fitting 44 leads to the rod end inlet port of the cylinder. I provided the system shown in FIGURE 1 with a control valve indicated generally by the reference character 46 having a housing 48 which slida'bly receives a spool 54 having a pair of lands 50 and 52. An actuating rod 56 extending out of the housing 48 permits the spool 54 to be posi- 3 tioned. A first outlet port 58 in the body 48 is connected by a line 60 to a common line 62 leading to both rod end inlet ports of the assemblies and 12. A second outlet port 64 in the body 48 is connected by a line 66 to a common line 68 leading to both the head end inlet ports of the assemblies.

A line 70* connects a first inlet port 72 to a suitable source (not shown) of fluid under pressure through an on-otl valve 73. A line 74 connects an exhaust port 76 in body 48 to the atmosphere or to a region of reduced pressure.

In one position of the spool 54 illustrated in full lines of FIGURE 1, the inlet port 72 is connected to both outlet ports 58- and 64. In the other position of the spool 54, port 58 is connected to inlet port 72 and .port 64 is connected to exhaust port 76. I have illustrated this position of the spool in broken lines in FIGURE 1.

Referring now to FIGURES 3 and 4, the cylinder slidably receives a piston 78 carried by the rod 22. Packing 80 provides a seal between the piston and the cylinder wall. Additional packing 82 seals one end of the cylinder with the piston rod. The spherical bearing housing 30 receives a bearing 84 carried by the cylinder 22 to permit limited tilting movement thereof of about 5. I close the end of the cylinder by means of an end cap 86 screwed into the cylinder. Packing 88 seals this end of the cylinder.

My assembly includes an auxiliary piston 90 slidably supported on the rod 22. Packing 92 and packing 94 respectively seal the auxiliary piston 90 to the cylinder wall and to the rod 22. I form the rod 22 as a hollow rod and provide the clevis 24 with a bore 96 which communicates with the hollow interior of the rod. An opening 98 in the rod wall between the auxiliary piston 90 and the main piston 78 permits the passage of fluid from between the pistons into the hollow rod and out through passage 96 for reasons which will be described hereinbelow. Line 40 is connected by fitting 42 to an inlet passage 100' leading to the head side of the cylinder.

The fitting 44 connects the line 62 to an inlet port 102 connected by a passage 104 to a valve assembly indicated generally by the reference character 106. I arrange the various parts of the valve assembly 106 in a bore 108 adjacent the spherical bearing 84. The valve 106 includes a seat 110 formed with an opening 112 communicating with passage 104. A spring 114 bearing between a retainer button 116 and a backup element 118 normally urges a poppet 120 slidably supported in a bore 122 in the valve housing 124 into engagement with the seat 110. A passage 126 connects the opening 112 with the interior of the cylinder on the rod side of the piston when the poppet 120 moves away from seat 110 against the action of the spring 114.

A bore 128 extending into the bore 108 from outside the cylinder wall threadably receives an actuating element 130 having a screwhead 132 which permits the actuator to be turned to move the poppet 120 away from seat 110 as will be described hereinafter. Preferably I provide the bore 128' with a cap 134 which must be removed before the actuator is turned.

Referring now to FIGURE 5, as an alternative to the screw-type actuator 130, I may provide an actuator 136 slidably received in a bore, such as the bore 128, and extending outwardly therefrom. A lever 138 pivotally supported on a pin 140 outside the bore can be turned slightly in a counterclockwise direction as viewed in FIG- URE 5 to push the actuator down to move the poppet 120 away from the seat 110.

I may also provide my assembly with a thermal relief valve indicated generally by the reference character 142. Valve 142 includes a seat 144 disposed in a bore 146 leading into the cylinder. The valve element 148 of the assembly 142 is urged by a spring 150 disposed in a block 152 into engagement with the seat 144. When, owing to an increase in temperature the liquid expands, the element 148' is moved away from its seat, it provides communication between the bore 146 and a bore 154 leading into port 156.

In operation of my improved piston and cylinder arrangement in an installation such, for example, as that shown in FIGURE 1, when I desire to lower the ramp I move the spool 54 to a position at which the supply line 70 is connected to both ports 58 and 64. I operate valve 73 to supply fluid under pressure to connect the supply of fluid under pressure to line 70 thus to supply fluid under pressure both to the head side and to the rod side of the cylinder. The fluid supplied to line 68 flows through lines 40 to the head side of both of the assemblies 10 and 12. Fluid supplied to the line 62 moves the poppet 120 of each of the assemblies away from its associated seat to permit the fluid to flow into the rod side of the cylinder. Owing to the fact that the pressure at the head side works on a greater area than does that at the rod side, the rod 22 of each of the assemblies is extended to lower the ramp. When the ramp has been lowered to the desired position, the supply of fluid is cut off by operation of valve 73 and the ramp remains in that position.

When the ramp is to be raised, spool 54 is moved to the broken line position shown in FIGURE 1 to connect the line 70 to port 58 and to connect port 64 to the exhaust line 74. Valve 73 is again opened and, under these conditions, fluid under pressure is supplied to the rod end of both assemblies and the head ends of the assemblies are connected to exhaust. The pressure acting on the rod sides of the pistons will raise the ramp.

If at any time fluid pressure is lost, the back pressure on the rod sides of the assemblies moves both poppets 120 into engagement with their seats to trap fluid in the rod sides to hold the supported members such as the ramp 14 in position.

It will be appreciated that as the ramp is being lowered, the auxiliary or slave pistons of each of the assemblies move with the main pistons 78. Should fluid pressure be lost and an auxiliary mechanical means such as a winch (not shown) be used to raise the ramp from that position, the auxiliary pistons 90 will remain in the positions to which they were moved as the ramp was lowered. Moreover, if after the ramp has been raised by mechanical means it is desired to restore it to its former lowered position, the main pistons 78 will move down until they engage the auxiliary pistons 90 so that the ramp is returned precisely to that position it occupied before being raised.

An internal pressure lockup is relieved by operating either the actuator 130 or the actuator 136 to move the poppet out of engagement with its seat.

It will be seen that I have accomplished the objects of my invention. I have provided a hydraulic piston and cylinder arrangement which fails safe. My assembly overcomes the defects of fail-safe piston and cylinder assemblies of the prior art. It is simple in construction and certain in operation. It is relatively inexpensive. My system incorporates means for ensuring that the supported member will be returned to the position from which it was moved mechanically after a pressure failure.

Having thus described my invention, what I claim is:

1. A hydraulic piston and cylinder assembly including in combination, a cylinder, a piston mounted for movement within said cylinder, a rod carried by said piston, said cylinder having a rod end and a head end, a source of liquid under pressure, means connecting both the rod end and the head end of said cylinder to said source to move said rod out of said cylinder, said connecting means comprising a one-way poppet valve between the source and the rod end of the cylinder, a seat for said valve between said valve and said source, an auxiliary piston slidably carried by said rod, and means forming an exhaust opening in said rod leading to the space between said pistons.

2. A piston and cylinder assembly for controllably raising and lowering a controlled member which normally moves downwardly under the influence of gravity including in combination, a cylinder, a piston mounted for movement within said cylinder, a rod carried by said piston, said cylinder having a rod end and a head end, means connecting said rod to said member for movement of the rod out of the cylinder to lower the member and for movement of the rod into the cylinder to raise the member, conduit means connecting both the rod end and the head end of said cylinder to said source to move said rod out of said cylinder to lower said member,

said conduit means comprising a one-way poppet valve between the sou-roe and the rod end of the cylinder and a seat for said valve between said valve and said source, said valve moving into engagement with said seat upon failure of the pressure of said source to trap liquid in the rod end of said cylinder to prevent said member from moving downward freely under the influence of gravity, and manually operated means for opening said valve independently of fluid pressure in said conduit means.

3. A piston and cylinder assembly as in claim 2 in which said valve is normally closed.

4. A piston and cylinder assembly as in claim 2 including a spring for biasing said valve closed.

5. A piston and cylinder assembly as in claim 2 in which said valve is normally closed and which said manually operated means includes a lever.

'6. A piston and cylinder assembly as in claim 2 including an auxiliary piston adapted to move with said main piston in one direction of movement thereof.

7. A piston and cylinder assembly as in claim 2 including an auxiliary piston slidably mounted on said rod.

8. A hydraulic piston and cylinder assembly as in claim 2 including an auxiliary piston slidably mounted on said rod, said first-named piston being a main piston, said piston rod being hollow and open to the atmosphere at its end remote from said main piston, the rod wall being formed with an opening between the main and auxiliary pistons.

9. A piston and cylinder assembly as in claim 2 including a thermal relief valve in the wall of said cylinder on the rod side of said piston.

References Cited UNITED STATES PATENTS 2,517,406 8/1950 Mott 91-468 X 2,764,131 9/ 1956 Knights 92-62 2,966,139 12/1960 Appel 91-415 X 3,088,283 5/1963 Furia et al. 91447 X 3,174,410 3/1965 Booth et a1. 91-4 19 3,273,468 9/1966 Allen 91-436 CARROLL B. DORITY JR., Primary Examiner.

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