NO143105B - MATT AND RIPFIX, AMORPH FOR CRYSTALLINIC MOVIES OR FILES AND PROCEDURE FOR THEIR PREPARATION - Google Patents

Description

Hydraulically controlled air cylinder construction.

This invention relates to fluid-driven maneuvering means and more particularly to a hydraulically controlled air cylinder construction.

Fluid-driven linear actuators are of two general types, namely those in which the fluid used is compressible (air) and those in which the fluid used is not compressible (hydraulic). Each type has advantages and disadvantages.

Air cylinders are widely used because they and their controls are simple and cheap and they can be conveniently connected to a source of compressed air commonly available in mines and industrial plants. The movement or stroke of an air cylinder's piston is, however, highly dependent on the load and the speed cannot be regulated, nor can the piston

easily stopped precisely during its stroke. Moreover, if an attempt is made to regulate the speed of an air cylinder's piston by constricting its passages, any temporary constraint imposed by the load during the stroke will result in a pressure build-up which may "let loose" explosively in a destructive and dangerous manner.

Where precise setting and control is required, a hydraulic actuation device is usually preferred. However, this involves the arrangement of a complete system including motor, pump, safety valve, a leak-free pipeline for a closed flow, filter, control valves and a reservoir. Questions about power supply, maintenance of the motor and pump, wire loss and leakage make the system far more complicated and much more expensive to install and maintain than a similar air-powered maneuvering device.

An object of the present invention

is to provide an improved air cylinder design which is subject to practically accurate speed and setting control while having the characteristics of being cheap to manufacture, compact in size,

easy to install and cheap to maintain.

In one embodiment of the invention, the speed of the piston can be set in advance independently for each direction of movement. Thus, e.g. the piston rod is set to extend by 0.6 m/sec. and to draw

kes back at 3 m/sec. Moreover, variations in the load will not cause these limits to be exceeded.

In another embodiment, the direction, speed of the stroke and locked position are subject to precise control. This control can be remotely controlled and either manual or part of an automatic system. It can be electric, mechanical or pneumatic. The latter is very simple and requires connecting

then of only a small, dual air line between the cylinder and the control, plus a supply line for main air to the cylinder.

A further embodiment enables that

a non-linear time can be set in cylindrical

clean so that the rod will follow independent speed-length curves during extension and retraction. Thus, e.g. the rod during extension accelerate, re-

decelerate and then accelerate again, while during retraction it can simply be made to accelerate and then decelerate to dampen the end of the stroke. As another example, the non-linear movement or gait can be arranged to open a damper or a door in such a way that the peripheral speed of the door is constant between the end of acceleration and deceleration.

The invention shall be described in more detail with reference to the drawings where fig. 1 is a side view in section of an embodiment of an air cylinder construction according to the invention, fig. 2 is an end view of the one in fig. 1 shown construction, fig. 3 is part of a side view in section of another embodiment, fig. 4 is a similar view of a further embodiment, fig. 5 is a similar view of a support leg according to the invention, fig. 6 is part of a side view of another embodiment of the invention, fig. 7 is a side view in section of a modified embodiment of a support leg construction fig. 8 is a similar view of an altered embodiment of a buttress construction, FIG. 9 is an enlarged section of a valve assembly used in the construction according to fig. 8, fig. 10 is a section of a modified embodiment of the valve assembly according to fig. 9 and fig. 11 is a side view in section of a further modified form of an air support structure.

In fig. 1 and 2, 1 is a cylinder casing which has an end cap 2 for the passage of a rod at one end and a blind end cap 3 at another end, which elements are fastened together by tension rods 4. An air piston 5 is mounted movably back and forth in the casing 1 and is arranged to act upon an external load by means of a tubular air piston rod 6 which terminates at the rod end 7 and an eye or fork 8 connected thereto. It will be noted that these elements correspond to the elements of a normal air cylinder.

Compressed air is supplied or blown out through air channels 9 in cap 2 and 10 in cap 3 by means of a standard four-way air control valve (not shown) to extend or retract piston rod 6 from cylinder 1.

The piston 5 is attached to the inner end of the rod 6 by means of an anchoring ring 11 to which the piston is attached by bolts 14, the ring 11 being attached to the rod by a resilient stop ring 15.

The tubular piston rod 6 is arranged to form a hydraulic cylinder which slides back and forth on a hydraulic piston 16 which is held stationary in relation to the main cylinder 1 by a tubular hydraulic piston rod 17 attached to the lid 3 by a bolt 18.

An oil reservoir 19 is arranged between the lid 3 and a lid 20 for a liquid oil reservoir through which the piston rod 17 extends. A flexible tube 21 provides a connection for transferring air from the channel 10 to the interior of the cylinder 1 through the air channel 22 in the lid 20.

An inner oil transfer tube 23 is held concentrically in the hydraulic piston rod 17 by means of a pressed-in bushing 24 and the end 25 of the hydraulic rod which is soldered to the tube 23. The hydraulic piston rod 17 thus includes a central oil passage 26 which connects a front oil chamber 27 in the piston rod 6 with an oil transfer channel 28 in the hydraulic piston 17, together with concentric annular passage 29 connecting a rear oil chamber 30 between the piston rods 6 and 17 via a channel 31 at the front end of the piston rod 17 with an oil transfer channel 32 at the rear end of piston rod 17.

The blind end cap 3 contains oil passages 33 and 34 which connect the oil reservoir 19 with the respective oil channels 28 and 32 across the sealing ring-equipped connection 35 of the piston rod 17 and the lid 3.

A needle valve 36 in the passage 34 restricts the flow of oil to the reservoir 19 from the rear oil chamber 30 in accordance with its setting while a check valve 37 also provided in the passage 34 allows oil to flow freely from the reservoir 19 to the rear oil chamber 30 by diverting the needle valve 36 Similarly, a withdrawal needle valve 38 restricts the flow of oil to the reservoir 19 from the front oil chamber 27 in accordance with its setting, while a check valve 39 allows oil to flow freely in the opposite direction.

Assuming that the air piston rod is in the fully retracted or retracted position, the effect of the described air cylinder is as follows: Compressed air is supplied through channel 10, while channel 9 is simultaneously connected to the atmosphere. The air piston 5 will then be applied a force which seeks to lead it towards the end cap 2. The hydraulic piston 16 presses on the oil in the rear chamber 30, and as the oil is virtually incompressible, the air piston can only be moved at a speed determined by the speed of this oil's transfer to the reservoir 19. This transfer rate is regulated by setting the needle valve 36.

When the air piston 5 is moved forward, the front oil chamber 27 increases in volume and oil is sucked from the reservoir 19 through the non-return valve 39 to supply the need. The extension speed is thus only regulated by setting the extension needle valve 36.

It must be noted that the total amount of oil contained in the front and rear chambers of the hydraulic cylinder increases as the air piston rod is extended, due to the retraction of the hydraulic piston rod 17. The floating oil reservoir cap is therefore moved towards the end cap 3 during the extension stroke as more oil is introduced into the front oil chamber than is returned from the rear oil chamber.

It is also clear that the air pressure applied by the extension stroke is also applied to the oil system through the oil reservoir cap. Due to the unbalanced pressure areas on the front and rear sides of the hydraulic piston, a residual unbalanced force assists the extension stroke.

An excessive overload can, of course, slow down the actuator, or even stop it altogether, but when the overload is removed the piston simply resumes its regulated speed unlike the normal air cylinder, which can quickly detach. As long as compressed air is supplied through channel 10, the air piston will move to its full range of motion at the pre-set speed.

If the channel 10 is now opened to the atmosphere and compressed air is supplied to channel 9, the air piston will be withdrawn and press against the oil in the front oil chamber 27. During the retraction stroke, the speed is limited by the flow of oil through the retraction needle valve 38 to the reservoir 19. At the same time, a smaller amount of oil flows freely into the rear oil chamber 30 from the reservoir 19 through the check valve 37, bypassing the indentation at the needle valve 36. The increasing volume of reservoir oil causes the reservoir cover to slide to meet the air piston when retracted.

The required seal is shown schematically as packing and O-ring seals, but it will be understood that the seal that is actually used in practice depends on the pressures occurring. It is clear that the resulting hydraulic pressure will be greater than the main air pressure in relation to the effective areas of the piston surfaces and this must be taken into account in the design.

The embodiment shown in fig. 3 makes the precise control of the direction, travel speed and locked position possible by remotely arranged pneumatic devices. In this embodiment, the arrangement of the master cylinder is exactly the same as in fig. 1, except for the blind end cap, and therefore does not need to be described again.

A hydraulic control housing 40 and a steering control housing 41 are mounted at the rear of the blind end cap 42 with sealing gaskets, as shown, the whole being attached to the cylinder 1 by suitable tie rods.

The tubular hydraulic piston rod 17 is attached to the cover 42 by a bolt 43. Oil is transferred across the packed connection 44 from the front and rear oil chambers 27 and 30 and passes through the respective channels 45 and 46 in the cover 42. In a similar manner as in the first embodiment, oil can flow freely outwards from the oil reservoir 19 from the channels 45 and 46 through the check valves 47 and 48 when required, but oil driven back from the front oil chamber 27 must pass through a withdrawal needle valve 49 in the cap 42 via the chamber 50 in the housing 40 and oil driven back to the reservoir 19 from the rear oil chamber 30 must pass through an extension needle valve 51 in the lid 42 via a chamber 52 in the housing 40.

The needle valve 42 is connected to a piston 53 which controls the retraction and is mounted in the cylinder 54 in the housing 40 by a stem 55. The piston 53 travels back and forth in the cylinder 54 under the action of an air balancing spring 56 in the cylinder on the stem side and against a smaller oil balancing spring 57 plus regulated air pressure from a channel 58 both on opposite sides of the piston. An air hole 59 connects the stem side of the piston with the atmosphere.

In a similar manner, the extension needle vehtil 51 is connected to an extension read control piston 60 mounted in the cylinder 61 in the housing 40 by a stem 62. The piston 60 slides in the cylinder 61 under the influence of an air/oil balance spring 63 at the rear and regulated air pressure enters the channel 64 on the stem side of the piston. An air hole 65 connects the back of the piston with the atmosphere.

The steering control housing 41 contains an air steering control piston 66 which slides in a cylinder 67 under the action of regulated air access through a channel 68 on one side thereof, and a counteracting air balancing spring 69 located on the other side thereof.

The side of the .cylinder which contains

the channel 68 is sealed by a cover 70, and it

the opposite side of the cylinder is connected to the atmosphere through an air hole 71.

The control valve 72 has a stem 73 which is mounted movably back and forth in a cylinder 74 which is axially aligned with the cylinder 67 whereby the stem 73 extends into the cylinder 67 on the side of the piston 66 which contains the spring 69. Control valve 72 has a head 75 (mainly conical as shown) and an intermediate reduced diameter portion 76 forming a chamber 77. The control valve head 75 cooperates with a seat 78 through which the chamber 77 communicates (in the open position of the valve) with a cylinder portion 79. A spring 80 between the head 75 and a plug 81 which closes the cylinder part 79 drives the valve in the closed position.

The control valve 72 acts as a three-way valve which allows compressed air to be supplied through a channel 82 leading to the cylinder portion 79 to enter a four-way valve control channel 83 leading from the chamber 77 when the control valve is lifted from the seat 78. In such a lifted position, an outflow channel 84 leading from the chamber 77 is closed by an O-ring 85. When there is no upward force on the control valve 72, the air pressure assisted by the spring 80 causes it to descend rapidly towards the seat 78 and thereby opens the control channel 83 to the atmosphere through channel 84.

A standard four-way air operated controlled air valve (not shown) is connected to control duct 83 and ducts 9 and 10 of the main air cylinder in such a way that when duct 83 is at atmospheric pressure (control closed) compressed air is supplied to duct 9, and duct 10 is connected to atmosphere (retraction stroke ). When control valve 72 opens and control channel 83 is pressurized, the four-way valve supplies compressed air to channel 10 and opens channel 9 to the atmosphere (extension stroke).

A main regulated air duct 86 serves to supply air from a standard relief type air pressure regulator (not shown) to the ducts 58, 64 and 68.

The operation of the described device is as follows; assuming that the relief type air pressure regulator, which acts as a pneumatic remote control, is set to true atmospheric pressure.

The control piston 66 is in its lowest position due to the spring 69, the control valve 72 is closed and air pressure in the main piston through the channel 9 seeks to retract the main piston rod 6, the retraction needle valve 49 is fully open due to the force exerted on the piston 53 by the spring 56, oil pressure against the stem 55 is balanced by the spring 57 and the extension needle valve 51 is held closed by the piston 60 under the action of the spring 63. In other words, a low air pressure for regulator control will result in regulated retraction of the air cylinder at maximum speed.

If now the regulated air pressure is increased, the withdrawal needle valve 49 is gradually closed, the extension needle valve 51 remains closed and the control piston 66 gradually rises towards the control valve 72 stem. Thereby the retraction speed is slowed and it is arranged so that at 40% of fully regulated air pressure, the spring 56 will be compressed to such an extent that the needle valve 49 will close completely. As no oil can now flow, the main air piston 5 is locked in any position it is in when both oil valves close.

The sequence of events when the regulated air pressure is further increased is that the control piston continues its position against the spring 69 until it meets the stem of the control valve 72. A small increase in the regulated air pressure must now be provided to overcome the air pressure and the action of the spring 80 on top of the valve 72 which will then slip into the open position. When it does this, the four-way valve for the main air control is turned back and puts duct 10 under pressure and the main air cylinder's duct 9 in connection with the atmosphere (extension). However, the main air cylinder will not yet move as the extension needle valve 51 is held closed by the spring 63 at this pressure. It is arranged so that the control valve will change when the regulated air pressure reaches about 50% of its total pressure range.

When the regulated air pressure reaches 60% of the full range value, the spring 63 will begin to compress and allow the extension needle valve 51 to begin opening. The main air piston rod 6 will then extend very gently from its locked position. By increasing the regulated air pressure to its full value, the extension needle valve 51 opens to its greatest extent and provides the greatest rate of air piston extension.

Briefly, the pneumatic control provides a small closed zone around the center of the regulated pressure range within which the main air control is switched to provide either extension or retraction potential. Outside this dead zone, an increase or decrease in regulated pressure is provided which varies the speeds of the extension or retraction of the main air piston rod 6.

It should be noted that while the air steering control is shown in a separate housing 41, to simplify the illustration, in practice it is quite possible to arrange the entire assembly of hydraulic and air steering controls, together with the four-way main valve in one housing. A main air connection then serves to feed both the steering control and the four-way valve, and an outlet can be arranged for supply to the remotely placed pressure regulator control.

Although the pneumatic control has been fully described, it is obvious that other arrangements can be provided to perform the necessary operation of switching the main air from extension to retraction while both hydraulic needle valves are closed and then regulating the operating speed by regulating the right needle valve . Thus, e.g. a simple direct-acting weight arm be mounted on the air cylinder for manual maneuvering and which provides varying speeds, of extension and retraction on either side of a "locked" center position. It should be mentioned that when the main air is set for a certain direction, e.g. retraction, only the corresponding needle valve has any control over the speed and whether the extension needle valve is open or closed is of no consequence, as the correct check valve serves as a switch allowing oil to flow freely from the reservoir to the enlarged oil chamber. A remote controlled electromechanical system can easily be designed to perform the same functions.

Fig. 4 illustrates a third embodiment which allows a non-linear movement to be initiated in the air cylinder so that the rod will follow independent speed/distance curves during extension and retraction. Also in this case, the master cylinder arrangement is the same as that in fig. 1 showed apart from the blind end cap.

A control housing 87 and a control housing cover 88 are mounted at the rear of a blind end cover 89 with a gasket seal and by means of suitable tie rods, as shown.

The tubular piston rod 17 is attached to the blind end cap 89 by a bolt 90 which holds the hydraulic piston. Oil is transferred across the gasketed union 91 from the front and rear oil chambers 27 and 30, and passes through respective oil transfer channels 92 and 93 in the blind end cap 89 and control housing 87. In a similar manner to the previously described cylinders, oil can flow freely outward from a control oil reservoir 94 in the housing 87 through the check valves 95 and 96 as necessary, but oil driven back from the front oil chamber 27 must pass a withdrawal control valve 97 over a withdrawal valve oil chamber 98 and a circular withdrawal valve opening 99, and oil driven back to the control oil reservoir 94 from the rear oil chamber 30 must pass an extension control valve 100 over a valve oil chamber 101 and a circular extension valve opening 102.

The retraction valve 97 is attached at one end to a control piston 103 by a nut 104, while the other end, with O-ring seal 105, slides in a retraction cylinder 106 with a piston movement. The front end of the retraction cylinder 106 is connected to the main air duct 10 through a duct 107.

Similarly, the valve body 100 for a valve is attached at one end to the control piston 103 by a nut 108 while the other end, which has an O-ring seal 109, slides in a cylinder 110 with a piston movement. The front end of the cylinder 110 is also connected to the main air duct 10 by ducts 111 and 107.

The control piston 103 which slides in a control cylinder 112 with O-ring seals as shown carries a central check valve 113, which will open when driven against a stroke limiter 114 which is screwed into the control housing 87. When the valve 113 is open, oil is admitted from the addition reservoir 115 between the piston 103 and the cover 88 to pass through to the control reservoir 94 until the piston 103 is brought back sufficiently for the valve 113 to close. Oil for the additive reservoir 115 is supplied through an oil transfer channel 116 from the main reservoir 19 which is placed as before in the main cylinder and sealed by the floating reservoir cover 20.

The effect of the control is to use the volume difference between the front and rear oil chambers 27 and 31 to convert the movement of the main piston 5 into a proportional but much smaller movement of the control piston 103. The extension and retraction valves 100 and 97 are directly connected to the piston 103 and have a contour showing varying diameters along their stroke, as shown. For each position of the main piston along its stroke there is a corresponding position of the control piston, and thus a definite constriction value of the control ports 102 and 99. By giving the control valves suitable contour it becomes possible to initiate independent speed-distance curves for retraction and extension in the movement of the main air piston 5.

When examining the effect in more detail, it must be assumed that the main piston rod 6 is in its fully retracted position. The large front oil chamber 27 then contains a minimum oil volume, the smaller rear oil chamber 31 contains a maximum oil volume, the control oil chamber 94 is expanded to receive the volume difference between the rear and front oil chambers, and the control piston 103 and the associated control valves are located completely at the posterior limit of their stroke. Oil that has been displaced from the addition reservoir 115 by the return movement of the piston 103 has passed through the channel 116 to the main oil reservoir 19 and the floating oil reservoir cover 20 is thus at the very front.

If compressed air is now supplied to the channel 10, and the channel 9 is opened to (the atmosphere, the main piston rod 6 will be extended as previously described, driving oil from the rear oil chamber 31 through the opening 102, which controls the extension, into the control oil reservoir 94. At the same time, a larger quantity of oil is drawn freely back from the control reservoir 94 through the check valve 96 to fill the expanding front oil chamber 27. The net effect is that the piston 103 and the associated retraction and extension valves 97 and 100 are moved forward with the instantaneous rate of extension of the main piston rod 6 determined solely by the size of the annular opening which exists between the valve 100 and the opening 102 in the extension valve at the present point of the movement. The floating oil reservoir cap 20 is of course carried towards the blind end cap 89 as a result of the transfer of oil through the channel 116 to the addition reservoir 115.

The movement of the air piston 5 along the hydraulic piston rod 17 results in a small loss of oil through the seal which, despite an insignificant amount per stroke, nevertheless becomes significant over the course of a few million operations. It can easily be seen that a loss of oil through this seal will be reflected in a restorative forward movement of the control piston 103 and the control valves 97 and 100, which will then no longer have strokes "matched" to the main air piston. Consequently, the speed of movement will not correspond to the assumed or set speed at a given distance.

The action of the check valve 113 and stroke limiter 114 overcomes this difficulty of oil loss. To illustrate, it can be assumed that an amount of oil X is lost during each cycle of retraction/extension. Now when the main piston 6 extends to its limit after one cycle, the control piston 103 will go to a limit that is further forward than in the previous stroke to compensate and brings the stroke limiter 114 to open the check valve 113. The air pressure prevailing in the channel 10 and which is transferred to the front ends of the control valves 97 and 100 through the channels 105 and 111, will then drive the piston 103 to displace an amount of oil X from the supplement reservoir 115 through the check valve 113 into the control reservoir 94 when the valve 113 will close again.

In this way, the control valves will always set to exactly the same position when the main piston is fully extended. The main oil reservoir 19 has sufficient capacity to replace oil loss and allow the cylinder to operate at its prescribed settings, unattended, for many millions of cycles, or indeed for the lifetime of the seals.

The effect of the system on the retraction stroke is quite similar to the extension stroke already described. Assume that the main air piston 6 is fully extended. By adding pressure to the channel 9 and connecting the channel 10 to the atmosphere, the main air piston will seek to move towards the blind end cap 89, compressing the oil in the front oil chamber 27 and driving it through the withdrawal opening 99 into the control reservoir 94. At the same time, a smaller amount of oil is drawn from the control reservoir 94 through the one-way valve 95 to fill the expanding rear oil chamber 31. Its net effect is to move the piston 103 and associated retraction and extension valves 97 and 100 away from the blind end cap 89. The instantaneous retraction speed of the main piston rod 6 is determined solely by its size of the annular

opening consisting between the withdrawal valve 97 and the opening 99 at it

present point of the movement. The lid 20 of the liquid oil reservoir is removed

from the blind end cap 89 during the retraction stroke due to transfer of oil

through the channel 116 from the additive reservoir 115.

The described air cylinder can be used in many phases of industrial activity. Compressed air is almost universally available throughout the industry, and it is also a fact that there is a large and growing need for simple and accurate control mechanisms to complement this appropriate means of power. When it comes to linear actuators, many special, complete and expensive hydraulic systems have had to be installed in situations where air power is readily available not because a greater force than air power is required but because the normal air control device is insufficient. The described construction is shaped to include a control device which will make the use of maneuvering means of the air power type easier and cheaper for a far greater area of application than has previously been possible. Thus, as an example, the mining industry can be mentioned as a field where the air cylinder according to the present invention will be particularly applicable.

A mining facility typically consists of two distinct parts — mining or extraction operations, either underground or on the surface, and the mill or recovery facility, which is essentially a specialized chemical treatment operation.

Compressed air lines are run all the way through virtually every mine in the world to every workplace. Apart from hauling or hauling, and sometimes even then, air is the prime mover. It is used to drive rock drilling machines, ventilation doors, chute gates, wagon tippers, chain lock valves, cargo pocket controls and the like. Although convenient, air power can be dangerous and many accidents each year can be directly or indirectly attributed to the uncontrollable, explosive properties of raw air power.

Ventilation or fire doors are used in many places in a mine. They are usually operated by double controls placed on opposite sides of the door and removed about 30 m from this to be suitable for ore train operation. A significant differential pressure built up by the ventilation air generally occurs against the door. If an air cylinder is used to operate the door a considerable force is required to bring it to begin opening and almost full air pressure builds up in the cylinder before any movement occurs. As soon as the door opens sufficiently so that the ventilation air pressure against it can be released, the door is flung open violently by the pressure that has built up in the cylinder and it is clear that narrowing the air channels to the cylinder will not significantly help this.

The doors must be made solid and heavy to withstand the violent impact and this in turn increases inertia, results in high costs, extensive maintenance and a greater risk of injuring staff who happen to be in the way. A hydraulically controlled air cylinder would be particularly suitable for operating such doors.

As another example, long-stroke air cylinders or "push supports" are quite commonly used to support and adjust rock drilling machines and provide the significant force required for effective rock crushing at the impact drill. During drifting or at cross locations, holes are drilled horizontally in a finished pattern in the stub for charging and blasting. The horizontal pressure and the upward supporting force is supplied by an air support or leg whose piston is attached to the machine and can swing in a vertical plane, while the cylinder itself tilts backwards and downwards to a spike-like end which is driven into the floor of the operation.

Apart from the difficulty with the initial alignment of the holes due to a lack of precise control, there is a constant danger of the drill steel breaking as soon as the hole is created and strong pressure is applied. Boron steel is exposed to constant bending and knocking and eventual wear and breaks quickly. Released from force, the air support explodes under full line pressure, pulling the drill operator towards the stub and possibly impaling the spent steel away, if his reaction is not quick enough to release the engagement of the machine.

In fig. 5 shows an air leg or support which is intended for safe, controllable operation and increased service life.

An air cylinder casing 117 is closed at one end by a blind cover 118 into which an external base spike 119 is screwed. A cap or cap 120 is screwed into the other end and forms the bearing through which a tubular air piston rod 121 extends and retracts, sealed by O-rings as shown and incorporating a rod end wiper 122 of molded rubber.

A standard impact drill attachment 123 is screwed into the outer end of the tubular air piston rod 121 and includes an air inlet and outlet port 124 along with pressure and relief valves and impact drill swivel connection (not shown). An air piston 125 is a press fit on the inner end of the piston rod 121 and slides in the cylinder jacket 117 on O-ring seals as shown.

A tubular hydraulic piston rod 126 is screwed into the blind end cap 118 and

locked by a nut 127. As shown, the air piston 125 has a central bore to allow sliding movement along the hydraulic piston rod 126, and O-rings 128 provide sealing and wiping action. The other end of the piston rod 126 ends at

a hydraulic piston seat 129. A hydraulic piston 130 is held in contact with the seat 129 by a weak piston spring 131 which acts against an adjusted collar 132 attached to the piston rod 126.

An air transfer tube 133 can slide freely in the tubular hydraulic piston rod 126 and through a central bore in the hydraulic piston seat 129 equipped with an O-ring seal 134. The transfer tube 133 is soldered to a floating oil reservoir cap 135 which can slide in the tubular air piston rod 121 on the O-ring seal as shown. The described arrangement provides a rear oil chamber 136 in the piston rod 121 between the pistons 125 and 130 and a front oil chamber 137 between the piston 130 and the cap 135. An air valve 138 is arranged as an air valve when the rear chamber 136 and the front chamber 137 are filled with oil. A sealed air passage is thus provided from the external supply via the opening 124 into an air inlet chamber 139 in the piston rod 121, from there through the transfer tube 133 into the tubular hydraulic piston rod 126 and finally out of an opening 140 in the blind end cap 118 into the main air pressure chamber 141 in the main cylinder 117 between the jacket 118 and the piston 125.

A controlled air passage is provided in the piston 125 from the main air pressure chamber 141 to the front air chamber 142 in the master cylinder in front of the piston 125. This air passage is provided with a shuttle valve arrangement in the piston 125 and comprises an outlet shuttle valve 143 slidably mounted in a valve liner 144 which is fixed in a hole 145 drilled in the piston 125 pressure chamber side. A channel 146 provides connection from the hole 145 to the chamber 142. A spring 147 drives the valve 143 in a direction towards a retaining snap ring 148 in the liner 144 at its pressure chamber end, and it will be clear that when the pressure chamber 141 is released from pressure, the valve 143 is held in this position by the spring 147. In this rearward position, air can pass through the transfer channels 149 formed in the valve over a transfer chamber 150 formed in the hole 145 into the transfer channel 146.

Movement of the valve 143 in the other direction is limited by a valve seat 151 arranged in the hole 145. It will be clear that the valve 143 can be operated by air pressure against the seat 151 and thereby the connection between the main pressure chamber 141 and the front air chamber 142 is broken.

A relief channel 152 is provided in the rod cover 120 to connect the front air chamber 142 with a low pressure relief valve 153. A handle 154 is provided for moving and positioning the air support.

The effect of the described air support or leg is as follows: First assume that the support is in its fully retracted position when the air piston 125 is close to the blind end cap 118, the shuttle valve 143 is held against the stop ring 148 by spring 147, rear oil chamber 136 is at its maximum volume, front oil chamber 137 is at its minimum volume with the hydraulic piston seat 129 positioned close to the floating oil reservoir cap 135, the air inlet chamber 139 is at its minimum volume and the low pressure relief valve 153 is closed.

If now compressed air is supplied at the inlet 124, it is transferred through the transfer pipe 133 and the opening 140 in the hydraulic piston rod 126 into the air pressure chamber 141. The opening 140 is considerably larger than the shuttle valve's transfer channels 149 and furthermore the front air chamber 142 is relieved by a few kilos of excess pressure at the valve 153, consequently, the shuttle valve 143 is closed against the seat 151 when the pressure difference on opposite sides of the shuttle valve reaches a certain value determined by the spring 147.

The air pressure against the end of the piston 125 drives it away from the blind end cap 118 and extends the air piston rod 121 from the cylinder. However, the speed of movement is limited by the rate at which the pressure oil in the rear oil chamber 136 can leak past the controlled clearance provided between the piston 130 and its bore in the piston rod 121. It will be seen that a sealed piston with an internal leakage opening would be an alternative arrangement .

When the piston rod 121 is extended and the hydraulic piston rod 126 is withdrawn from the rear oil chamber 136, a net movement of the reservoir cap 135 away from the drill attachment 123 occurs to equalize the volume difference between the piston rod 126 and the air transfer tube 133. During this extension stroke, air is driven out of the front air chamber 142 through the relief valve 153.

It is important to understand that it is highly undesirable in a rock dust atmosphere to allow outside air to be drawn into any part of the cylinder during the retraction stroke, although this is common practice. A controlled air leak through the air piston can be used in an attempt to overcome this disadvantage, but this is a waste of air power. The combination of a shuttle valve and a low pressure relief valve in the described arrangement virtually eliminates dust contamination and air loss.

The effect of the withdrawal will now be described with the opening 124 open to the atmosphere through an external valve (not shown) which is under the control of the drilling machine operator. When the pressure in the main cylinder chamber 141 drops to a certain pressure determined by the spring 147, the shuttle valve 143 opens and allows the air to flow out through the channel 146 into the front air chamber 142 as well as through the opening 140. In this way, no resistance to normal retraction of the air piston by gravity by some vacuum action in front air chamber 142, and no air is drawn in from outside. At the same time, the expansion of the rear oil chamber 136 behind the hydraulic piston 130 will lift it from the seat 129 against the weak spring 131 so that oil is allowed to flow freely from the front oil chamber 137 as needed, and in reality does not provide any compression force on the hydraulic piston 130.

The floating end cap 135 responds to the retraction stroke by moving toward the drill mount 123, as a result of which the hydraulic piston rod moves into the rear oil chamber and supersedes the action of the smaller diameter air transfer tube 133.

The safely regulated maximum speed of extension of this hydraulically controlled air support or leg is of primary importance from the point of view of safety and expediency. However, an additional advantage is obtained from the complete seal provided in the described construction. The mechanism is completely isolated from air contaminated by water and dust and free from abrasive particles, therefore the gaskets last for their entire intended life. This is many times greater than the lifetime of gaskets working in the degrading conditions present in the previously used air-type drilling machine support legs.

Also, in this hydraulically controlled air leg or support, the high frequency vibration, which is caused by the percussive nature of the drill, is virtually oil damped by the swivel joint instead of by the movement of the air piston. This high-frequency movement of the piston in the dust-contaminated cylinder of a standard air strut or leg is the cause of the high rate at which the leather seals used wear. This siltation takes place so quickly that it is common practice to equip the miner with extra gaskets which he himself has to replace during the shift at considerable cost in lost working time.

In many places in a mine, air cylinders are used to maneuver chute gates or chains that control the flow of ore through openings and it is a distinct advantage for this purpose to have a device that can do more than just violently open or violently close.

Shaft cargo pockets, e.g. filled in a certain

height before the ore is tipped into the lift vessel and

it is important that this height is not exceeded due to possible play in the shaft and overloading of the lift, nor should

it will be too lightly loaded if the optimal health effect is to be achieved.

This loading is normally carried out by an operator controlling a two-way air cylinder to open and close the main ore passage gate. It is clear that with only two stable positions of the available air cylinder (gate open/gate closed) complicated by varying flow properties of the ore, fineness of control is very difficult and effective loading depends quite a lot on the operator's experience, judgement, skill and vigilance and reaction. The use of a remote-controlled cylinder, e.g. as shown in fig. 2, allows a precisely locked position, and variable speed for the opening and closing of the gate will significantly improve the difficulties and improve the performance at this important point in the mine. It will also be suitable for fully automatic load control for the lift vessel.

A further modification is shown in fig. 6 in which the locked position of the maneuvering device is subject to control by a remote signal source. In this case, for each valve for each control signal there is a corresponding locked and stable position of the piston, and a change in the signal will cause the piston to move to the required new position at a regulated speed.

A fluid control housing 155 and a make-up reservoir cap 156 are mounted at the rear of a blind end cap 157 with packing or O-ring seals, as shown, which assembly is attached to the cylinder jacket 1 by suitably arranged tie rods, not shown.

The tubular hydraulic piston rod 17 is attached to the cover 157 by the bolt 18. Oil is fed across the gasket connection 35 from the front and rear oil chambers

27 and 30, and is passed through appropriate oil transfer channels 158 and 159 in the blind end cap 157 and the control housing 156. In a similar manner to the cylinders already described, oil can flow freely outwards from a control reservoir 160 in the housing 155 through the check valves 161 and 162 as needed , but oil driven back from the front oil chamber 27 must pass a withdrawal control valve 163 over a withdrawal oil chamber 164 and a circular withdrawal valve opening 165, and oil driven back to the control oil reservoir 160 from the rear oil chamber 30 must pass an extension valve 166 over an extension valve oil chamber 167 and a circular extension valve opening 168.

The retraction valve 163 is connected to a retraction control piston 169 by a stem 170 with O-ring seals as shown. The piston 169 slides in a cylinder 171, and closes the valve 163 when compressed air is supplied to a valve chamber 172 through an oil control air passage 173 from a normally open, solenoid operated, three-way air valve 174. An air hole 175 opens the stem side of the piston 169 to the atmosphere.

In a similar manner, the valve 166 is connected to a control piston 176 by a stem 177 with the arrangement of O-seals as shown. The piston 176 slides in a cylinder 178, closing the valve 166 when compressed air is supplied to a valve chamber 179 through oil control air channel 173 at a recess 180 for a fastening bolt for the piston. Both the extension and retraction valves thus close simultaneously whenever the oil control air valve 174 is de-energized.

A main control piston 181 sliding in a control cylinder 182 with an O-ring seal as shown carries a regulating check valve 183 which will open when driven against a stroke limiter 184 screwed into the housing 155. When open, the valve 183 allows oil from a additive reservoir 185 is allowed to pass through a channel 186 into the control reservoir 160 until the piston 181, under the action of a spring 187, is returned sufficiently to allow the valve 183 to again close. Oil from the additive reservoir 185 is supplied through an oil transfer channel 188 from the main oil reservoir 19 placed as before in the main cylinder and sealed by the floating reservoir cover 20.

A tubular extension 189, terminated by a threaded end cap 190, is threaded onto the control piston 181 and slides reciprocatingly through O-ring seal 191 in the additive reservoir cap 156. A switch piston 192 slides in a short cylinder bore 193 formed in the rear end of the tubular extension 189 with O-ring seals as shown. The hollow stem 194 of the piston 192 becomes through an O-ring seal in the end cap 190 and serves to operate a switch 195, which comprises a control weight arm 196 pivotable at 197 to an arm 198 which is attached to the cap 190 and is actuated in one direction by a spring 199.

An air balance spring 200 is pressed together between the front side of the piston 192 and a spring holder 201 equipped with air holes. The position of this is set by a spring stop rod 202, threaded and locked on a rod support part 203 which is firmly connected to the lid 156 of the additive reservoir.

A sealed air chamber 204 in the piston

192 stem side is in connection with a control air channel 205 on the reservoir cover 157 through a flexible tube 206 and a channel 207 on the end cap 190. A remotely regulated source of compressed air 208 is connected to the control air channel 205 and supplies a pneumatic control signal which sets the main air piston rod 6, which later must be described.

The switch spring 199 keeps the switch control weight arm 196 in contact with the piston stem 194. The movement of the stem 194, amplified by the weight arm action of the switch 195, is transmitted to a common force contact 209 which is carried by the switch weight arm 196. Opposite insulated contacts 210 and 211 are fixedly placed by a contact carrier 212 screwed onto the end cap 190, in such a way that the main power contact 209 contacts either 210 or 211 on either side of a neutral "all solenoids de-energized" position.

Electrical connections are as indicated removed from the contacts in the usual way and a cover 213 keeps dust out from the rear end.

The contact 210 is connected to a solenoid 214 for a three-way normally open air valve 215 which, when energized, opens the master cylinder passage 10 to the atmosphere. The contact 211 is connected to a solenoid 216 for a three-way normally open air valve 217 which, when energized, opens the master cylinder passage to the atmosphere. A solenoid 218 for the oil control valve 174 is in series with the solenoids 214 and 216

parallel arrangement and is therefore energized

when either 214 or 216 is energized. The main power supply 219 is shown schematically.

As schematically indicated, the valve 174 has a line 220 to the channel 173, a supply line 221 for compressed air and a line 222 leading to the atmosphere, the valve 217 has a line 223 to the channel 9, a supply line 224 for compressed air and a line 225 to the atmosphere, and the valve 215 has a line 226 to the channel 10, a compressed air supply line 227 and a line 228 to the atmosphere.

Briefly stated, the effect of the control is to use the volume difference between the front and rear oil chambers 27 and 30 to convert the movement of the main piston 5 into a proportional but much smaller movement of the control piston 181. A continuous comparison is made between the position of the control piston 181 and the amplitude of a remotely controlled position signal, so that in this way an error signal is produced which activates control means to iron out the error and position the air piston rod in accordance with the requirements from the control signal.

The effect is examined in more detail on the assumption that a low value of the control air pressure has caused the main piston rod 6 to assume a stable locked position at the limit of its retraction stroke. The large front oil chamber 27 then contains a minimal oil volume, the smaller rear oil reservoir 160 has expanded to accommodate the volume difference between the front and rear oil chambers, the control piston 181 and the tubular extension 189 are at their rearmost limits of their stroke, the force of the spring 200 against the switch piston 192 is at a minimum and is balanced by regulated air pressure from the control 208, the piston 192 and the connected switch 195 are in the middle position, all solenoids are de-energized and allow full air pressure on both sides of the main air piston 5 and on both oil valves 163 and 166, whereby these are kept closed.

If it is now desired to extend the main air piston rod 6 to a specified position, a proper increase of the regulated pressure is set at the outlet of the control 208. The increased pressure against the breaker piston 182 overcomes the spring 200 and carries the piston the very small distance to its forward limit of travel, closes contacts 209 and 211 and energizes solenoids 216 and 218. Solenoid 216 operates air valve 217, opens passage 9 to atmosphere and allows line pressure through passage 10 to drive air piston 5 forward. Solenoid 218 operates air valve 174, opens passage 173 to atmosphere and allows oil control valves 163 and 166 to open.

The main piston rod 6 will now extend and drive oil from the rear oil chamber 30 through the extension control opening 168 into the control reservoir 160. At the same time, a larger amount of oil freely flows back from the control reservoir 160 through the check valve 162 to fill the expanding front oil chamber 27. The net effect of this is that the piston 181 and connected parts are moved forward, and the lid 20 of the floating oil reservoir is moved towards the blind end cap 157 as a result of the transfer of oil through the channel 188 to the addition reservoir 185. As before, the speed is limited by the extension of the piston rod 6 at the oil control opening 168.

When the control piston 181 is moved forward, the spring 200 is again compressed against the spring holder 201. When this increasing spring shaft and the counter force created by the regulated air pressure approach balance, the breaker piston 192 floats to its middle position and connected switch 195 separates the contacts 209 and 211 de-energizing all solenoids, the oil valves 163 and 166 closes and locks the main air piston rod 6 in the new position, and air is supplied to the channel 9, pressurizing both sides of the air piston 5 ready for positive movement in accordance with the next control.

The effect of the limiter 184 and the check valve 183 is as described earlier in connection with fig. 4. They compensate for long-term oil loss by setting piston 181 in exactly the same position whenever the main piston reaches a predetermined extension limit.

The action of the system when there is a need to retract the main air piston is essentially the opposite of the extension movement already described. A proper lowering of the regulated pressure is set by the action of the control 208. The lowered pressure against the breaker piston 192 allows the spring 200 to move the piston to its rear limit of travel, to close the contacts 210 and 209 and energize the solenoids 214 and 218. The solenoid 214 acts on the air valve 215 , puts the channel 10 in communication with the atmosphere and allows the line pressure through the channel 9 to drive the main air piston 5 back. The solenoid 218 actuates the air valve 174, communicating the passage 173 to the atmosphere and allowing the oil control valves 163 and 166 to open.

The main piston rod 6 will now retract, driving oil from the front oil chamber 27 through the control opening 165 into the control reservoir 160. At the same time, a smaller amount of oil is drawn from the control reservoir 160 through the check valve 161 to fill the expanding rear oil chamber 30. The net effect is that the piston 181 and connected parts are moved backwards, and the floating oil reservoir cap 20 is moved forwards as a result of the transfer of oil through the channel 188 from the addition reservoir 185. As before, the speed of the retraction of the piston rod 6 is limited by the oil control opening 165.

When the control piston 181 is moved backwards towards the lid 213, the spring 200 is released

voltage. When the decreasing spring force and the counter force created by regulated air pressure approach balance, the breaker piston 192 floats to its center position, de-energizing all solenoids and locking the main air piston 6 in the required position as previously described.

Although the example in question uses a combined pneumatic-electric control, it is clear that a completely pneumatic control can easily be designed. The enhanced movement of the break piston 192 around the balance point will in this case drive the control of the main air valves directly.

An all-electric control will be just as easy to design. A wide variety of input and output transducers with associated controls are available and will enable analog information regarding a flow to produce the required continuously variable linear motion of this cylinder.

This system can be used in mechanical or electrical feedback circuits. Thus, e.g. shutters or dampers for large mine ventilation fans are regulated by this device. The temperatures of the fan air must not fall below a certain limit regardless of variations in the temperature of the outside air down to below zero. The most economical use of the heater and fan capacity under all conditions can only be achieved by regulating the shutters or damper in accordance with the fan air temperature.

As another example, continuous proportioning of the materials can be accomplished by feeding back messages from a belt weigher to control gates operated by this type of cylinder.

Large valves and mechanisms of various types that require a proportional linear movement maneuvered at a distance can be adapted to this type of control.

Fig. 7 shows the construction of an air leg or support which allows rapid retraction of the main piston rod if necessary. The main air cylinder's mantle 229 is equipped at one end with a blind end cap 230 and the other end with a rod cover 231. This includes a sleeve 232 with a liner 233 and seal 234 through which a tubular air piston rod 235 extends. An air piston 236 is mounted on the end of the rod 235 and slides in the jacket 229 on a sealing ring 237.

A tubular hydraulic piston rod 238 has one end attached to the blind end cap 230 and a hydraulic piston seat part 239 attached to its other end. An air transfer tube 240 can slide freely in the piston rod 238 and through the part 239 which is equipped with a sealing ring 241. The transfer tube 240 is attached to a floating oil reservoir cover 242 which can slide in the air piston rod 235 on a sealing ring 243.

A hydraulic piston 244 is slidably mounted on the piston rod 238 and provides, in conjunction with the piston seat portion 239, controlled connection between a rear

oil chamber 245 and a front oil chamber 246 in the piston rod 235. The piston 244 has

a closed position in which it says under construction

against the valve seat part 239 and an open position delimited by a stop ring 247 on the piston rod 238 in which connection is provided between the chambers 245 and 246 through the channels 248 and an annular passage 249 in the piston 244.

It will be clear that in the mantle 229 at the piston 236 a main air chamber 250 is provided behind it and a front air chamber 251 in front of it. Connection between the air inlet chamber 252 in front of the lid 242 and the main air chamber 250 is provided through a transfer tube 240, the hollow piston rod 238 and the channels 253 in the rod 238.

Controlled communication between the chambers 250 and 251 is provided by an annular internal air transfer passage 254 which encloses the piston rod 238 in the rear end portion of the piston 236, an annular external recess 255 in the piston 236 which borders the front end thereof and forms an annular passage 256, and a number of radially extending channels 257 which connect these passages 254 and 256 through a bore 258 in the piston 236. A cylindrical valve 259 is slidably mounted in a bore 258 and on the piston rod 238 and is equipped with sealing rings 260, 261. The bore 258 ends in an annular shoulder 262 at the passage 254, which shoulder forms a valve seat for cooperation with the valve 259 to define its closed position and in which the channels 257 are closed.

It will be noted that the valve 259 controls the passage between the main air chamber 250 and the front air chamber 251 in accordance with the pressure difference between the rear oil chamber 245 and the main air chamber 250.

The compressed air supplied to the air piston rod 235 through the generally arranged control valve (not shown) transfers pressure almost instantaneously to the hydraulic fluid through the floating reservoir cap 242. Corresponding build-up or reduction of the pressure in the main air chamber 250 occurs after the controlled pressure due to the constricting characteristic of the air transfer tube 240 and the capacity of the main air chamber 250.

When supply pressure is thus applied, the valve 259 closes against the seat 262 and the pressure then builds up in the main air chamber 250 and extends the air support or leg. As soon as the valve 259 is closed, its end face area exposed to the air pressure in the annular transfer passage 254 becomes less than the area exposed to the hydraulic pressure in the chamber 245 and the valve becomes overbalanced. The control air pressure on the hydraulic fluid must be reduced below the pressure in the main air chamber 25 before the valve 259 will open again, and again the narrowing of the transfer pipe 240 and the capacity of the chamber 250 contribute to a rapid achievement of this necessary opening differential.

As soon as the valve 259 is opened as a result of a sharp reduction in the control pressure, air in the chamber 250 can freely flow out through the channels 257 into the front air chamber 251 which can be connected directly to the atmosphere as shown at 263, or kept at a slight overpressure by low pressure relief valves f e.g. as shown at 153 in fig. 5. This rapid reduction of main chamber 250 pressure allows rapid retraction of piston rod 235 if necessary, or simply rapid pressure relief to an intermediate control pressure as it will be noted that valve 259 will close any time the pressure in chamber 251 has dropped to that set control pressure.

It will be noted that the air pressure in the inlet chamber 252 is transferred almost instantly to the hydraulic fluid and that this pressure is actually independent of the pressure/flow conditions in the air chambers of the device itself. By using this hydraulic pressure to operate the relief transfer valve 259 with a high flow characteristic in the air piston, retraction can be performed with speed and ease.

In fig. 7 also shows an improved attachment for the blind end cap. It is common practice to attach the blind end cap to the cylinder jacket with screw threads. This is not entirely satisfactory as the cylinder casing must usually be made of light metal, such as aluminum alloy, and all strokes of the drill are transferred through the threaded connection to the base spike. Loosening the lid and destroying the threads with the consequent discarding of valuable pipes is a common accident.

As shown, the blind end cap 230 comprises an end part 264 with a threaded annular shoulder 265 which can rest against the end of the mantle 229, and a compression plug 266 which is mounted by screw threads in a holder or bore 267 in the part 264 and has a sliding fit in the cylinder jacket 229. The plug 266 has an outer annular recess 268 and in this is placed a compression ring or

-collar 269, which is slidable on the plug in the mantle 229 but is prevented from moving behind

above by a retaining ring 270 mounted in the mantle. A number of sealing rings 271, e.g. ordinary O-rings, are inserted in the recess 268 between the ring or collar 269 and a shoulder 272 which delimits the end of the recess.

The rings 271 provide a pressure seal and result in a vibration-proof lock washer action by maintaining tension on the threads over a number of revolutions of the final tightening of the cap member 264. The shoulder 265 is under constant pressure against the cylinder jacket end face and vibration is transmitted without wear, solution or stroke.

Further embodiments of the invention will now be described with special reference to air supports or legs which include a power-driven retraction device.

When drilling horizontally with a combination of an air prop or leg and a drill, it is necessary for the operator to regularly advance the air leg as the drill steel is fed into the rock, in order to maintain the correct angle and force components for optimal drilling. When air legs that cannot be retracted are used, the supply pressure must be switched off and the air legs must be pulled up and set manually each time a movement is made.

The retractable air legs that are now in use are usually of the "turned" type, i.e. the cylinder is connected to the drill and the end of the piston rod is pressed against the sleeper. This orientation simplifies the placement of the common four-way extension/retraction valve, which must be at the blind end of the air leg cylinder to facilitate "piping" to the front and rear air chambers, and must also be suitably

within reach of the operator's hand

the drill. However, this inverted orientation has a disadvantage in that the height of the handle on the cylinder changes when the air leg is extended, and while the force-retraction reduces the necessary lifting, the leg must still be controlled and positioned manually. On tall gangway holes, the handle may be at chest height, which is not an appropriate height for lifting.

Two versions of a proper upwardly retractable air leg incorporating hydraulic damping and a single valve control for extension/retraction and pressure regulation will now be described.

In fig. 8 and 9, 273 is a main air cylinder jacket closed at one end by a blind end cap 274 into which a base spike can be screwed. On its other end is screwed a cap 275 which supports a bearing 276 through which a tubular air piston rod 277 is extended and retracted. As shown, the bearing includes a replaceable liner 278, a rod end wiper 279 and a sealing O-ring 280.

It will be understood that a standard mount for a rock drill will be screwed onto the outer end 281 of the piston rod 277 to connect the air leg to the drill and to provide an air passage into the piston rod 277 from the pressure control valve (not shown).

An air piston 282 has a tight thread fit on the inner end of the piston rod 277 and slides in the cylinder jacket 273 on the O-ring seal 283 as shown.

One end of a tubular hydraulic piston rod 284 is screwed into a holder 285 which is carried by a valve body 286 attached to the blind end cap 274. The air piston 282 has a central bore 287 for sliding along the piston rod 284, a hydraulic sealing O-ring 288 is arranged as shown. A seat part 289 adapted for a hydraulic piston is mounted on the other end of the piston rod 284. A hydraulic piston 290, slidable on the piston rod 284 has a limited travel between a stop ring 291 on the rod 284 and the seat 289, and provides controlled connection between rear oil chamber 292 and front oil chamber 293 in the piston rod 277. When the piston 290 is in contact with the seat 289 (as during the air leg extension) there is controlled oil transfer between the chambers 292 and 293 through an annular passage 294 in the piston 290, a channel 295 in the piston 290 which leads from the chamber 292 to the passage 294, and self-cleaning groove 296 on the seal side of the piston 290. As the piston 290 is guided by the seat 289, oil flows in the opposite direction in unobstructed passageways 294 and channel 295 (as a retraction of the air leg).

An air transfer tube 297 can slide freely in the tubular hydraulic piston rod 284 and through a central bore 298 in the piston seat -289 which is equipped with a sealing ring 299. A floating oil reservoir cap 300 is fixed on the front end of the transfer tube 297, and is slidable in the air piston rod 277 on a sealing ring 301.

The valve body 286 contains a pressure-sensitive four-way valve structure which will now be described with reference to fig. 9.

As shown, the holder 285 equipped with seal 302 for the hydraulic piston rod is stopped in part 286 by means of a ring 303. In part 286, a valve lining 305 is also mounted between the holder 285 and a stop ring 304, and between this and another stop ring 306 mounted two spring housings 307 which contain a spring 308, as the housings

307 are normally separated from each other under the action of the spring 308.

A shuttle valve part 309 is mounted in the liner 305 and the valve part 309 has a pressure distribution chamber 310 with a channel 311 leading to its face at the holder 285 and communicating with the interior of the piston rod 284 through the opening 312 in the holder 285. The channel 311 is normally closed by a check valve 313 under the action of a spring 314. The chamber 310 has a small opening 311a which bypasses the valve 313.

An extension channel 315 connects the chamber 310 with a circumferential groove 316 in the part 309 and a retraction channel 317 connects the chamber 310 with a circumferential groove 318.

The portion 309 also contains an outflow passage 319 which is open to the rear and has a channel 320 connected to an outlet circumferential groove 321 in the portion 309. The rings 322 provide a pressure seal between the circumferential grooves, as shown.

The liner 305 has a number of radially extending channels 323 leading inwards from an extension circumferential groove 324 thereon which is in communication with the groove 321. The liner 305 also has a number of radially extending extension channels 325 leading inwards from a retraction circumferential groove 326 which is in connection with the groove 318. The lining groove 324 is in connection with the extension channels 327 in the valve body 286 and the lining groove 326 with the withdrawal channels 328 in the same.

A circumferential groove 329 in the valve body 286 provides a passage from the withdrawal channels 328 to an external transfer tube 330 which communicates with the front air chamber 331 through an annular groove 332 in the piston 282. The extension channels 327, separated by a sealing ring 333 from the withdrawal groove 329, leads directly into the main air chamber 334 over a circumferential groove 335 in the body 286.

The liner 305 is preferably made of a plastic composition, e.g. "Teflon". The circumferential grooves 324 and 326 in the same are sealed by O-rings 336. Danger of destruction or extrusion of the O-rings can be avoided by making the diameter of the rings larger than that of the channels 323 and 325.

The outlet passage 319 is connected to the atmosphere through openings 337 in the spring housings 307, a space 388 between the valve body 286 and the blind end cap 274 and the channels 339 therein.

The parts shown in the drawing are in their normal or "retracted" position.

When during operation it is desired to extend the air leg, compressed air is supplied through the air transfer tube 297 and the piston rod 284 to the front end of the valve part 309 and when the air pressure overcomes the force exerted by the spring 308 the valve part will be carried rearwards to its retracted position. In this position, compressed air is supplied to the main air chamber 334 through the elements 311, 315, 316, 323, 327 and 335 while the front air chamber 331 is connected to the atmosphere through the elements 332, 330, 329, 325 and 321, to the channels 339.

If it is necessary to reduce the pressure of the extension, this can be done by slowly relieving the control pressure and releasing through the diverter 311a.

If, on the other hand, a quick relief of pressure is required to bring the valve 309 to the retract position, the standard manual control valve can be closed quickly. The return valve 313 then allows a rapid outflow of the pressure 1 the hydraulic piston rod 284, the valve 309 is changed to the "withdrawal" position and the large capacity of the main air chamber 334 is quickly emptied through the elements 323, 321, 320 and 319 and then to the channels 339. in this way, the non-return valve's diverting arrangement enables a rapid changeover to withdrawal mode, without having to wait for the large contents of the main air chamber 344 to be drained down to the switching pressure. It will be understood for the time being that although the non-return valve is quite appropriate, it is not of importance for the fundamental operation.

The setting of the described mechanism can be such that retraction force occurs at pressure between, e.g. 0 and 2 kg/cm<2>. Over e.g. 2 kg/cm<2> the valve member 309 is displaced, emptying the front air chamber 331 and pressurizing the main air chamber 334 for rod extension at any pressure set by the conventional manual control valve.

In fig. 10, a valve arrangement is shown which enables the use of a larger pressure range during both the extension and retraction operations.

The embodiment according to fig. 10 is practically the same as in fig. 8 and 9 but includes the arrangement of ball stoppers 340 mounted in the valve body 286 and pressed by springs 341 into engagement with the side wall of the front spring housing 307. This has a circumferential groove 342 arranged to receive the spring-actuated stoppers 340 when the housing is moved to the "extension position" of the valve part 309.

By properly selecting the spring pressure and release force from the stoppers, an extensive choice of overlapping extension and retraction areas is available. Thus, the control valve 309 can be set to move to the "extension" position at a pressure greater than, e.g. 4 kg/cm<2> and the stoppers 340 can be used to hold it in this position until the pressure is reduced to e.g. 0.7 kg/cm<2> as it will be tilted back to the "retraction" position. Thus, once a specific extension method has been chosen, any pressure between 0.7 kg/cm<2> and full line pressure can be used for extension. Similarly, once the pressure is reduced below 0.7 kg/cm<2> any pressure between zero and 4 kg/cm<2> can be selected for retraction.

In short, the valve return spring 308 therefore determines the control pressure required to switch the valve to position

"extension", while the difference between

the force of the spring 308 and the retaining force of the stoppers 340 determine the switching pressure below which the valve will slip back to the "retraction" position.

Fig. 11 shows a further modification of a hydraulically controlled air support or

- legs with power-driven retraction. It includes a jacket 343 for a master air cylinder, a tubular air piston rod

344 which extends slidingly through a

end cap 345, an air piston 346 which is attached to the inner end of the rod 344 and which in the mantle 343 forms a main air chamber 347 and a front air chamber 348,

and a tubular hydraulic piston rod 349 with one end attached to a blind end cap 350 and a hydraulic piston 351 sliding

mounted on the same between a stop ring

352 and a piston seat 353 attached to its other end. An air transfer pipe 354 extending into the hydraulic piston rod 349 and carrying a floating oil reservoir cap 355 provides connection between the air inlet chamber 356 and the main air chamber 347 through the channel 357. A drill attachment 358 is connected to the front end of the air piston rod 344.

A thin-walled tube 359 is concentrically mounted inside the air piston rod 344 in a radially separated position from the rod 344 and from the hydraulic piston rod 349. The rear end of the tube 359 extends into the air piston 346 and is equipped with a gasket 360 to seal the rear oil chamber 361 against an annular air passage 362 formed between the tube and the air piston rod 344. The front end of the tube 359 is mon-

tert on a hub 363 on the mount 358 and fix-

is held on this by a retaining ring 364.

The passage 362 connects the front air chamber 348 through the channel 365 with a channel 366 in the machine mount 358 which controls retraction. A channel 367 in mount 358, which controls extension,

communicates with the air inlet chamber 356 and the main air chamber 347 through the transfer tube 354 and the hydraulic piston rod 349. The channels 366 and 367 will be connected by common control valve mechanisms.

It will be noted that the modified air legs or supports produced here have been

written in relation to the orientation of the same in which air is supplied through the piston rod and the blind end of the cylinder to the substrate. However, it will be clear that the reverse orientation of the air legs can be arranged by making smaller, obvious

end rearrangements of the same parts if such orientation becomes necessary or preferred.

Claims (11)

1. Hydraulically controlled air cylinder construction, comprising a main air- cylinder (1, 117, 229, 273, 343) with an air piston (5, 125, 236, 282, 346) arranged to move back and forth in the air cylinder, a tubular piston rod (6, 121, 235, 277, 344) located in the cylinder with a front end outside the cylinder and its rear end attached to the piston, where the piston rod performs extension and retraction strokes as a result of air pressure supplied to the piston, and a hydraulic device for controlling and adjusting the speed of the strokes, comprising a hydraulic piston (16, 130, 244, 290, 351) on a hydraulic piston rod (17, 126, 238, 284, 349) arranged in the air piston rod (5, 135, 236, 282, 346), in which air piston rod there is a front hydraulic fluid chamber (27, 137, 246, 293) on one side of the hydraulic piston and a rear hydraulic fluid chamber (30, 136, 245, 292, 361) on the other side of said piston, where the capacity of these chambers depends on the movement of the air piston rod relative to the hydraulic piston, and a hydraulic fluid passage (29, 129, 249, 294) between one and the other hydraulic fluid chamber, characterized in that devices for controlling the fluid flow through the passage comprise a partition wall (20, 135, 242, 300, 355) which is displaceable in the air cylinder or on the air piston rod for axial movement in nominal te cylinder, one side of which partition wall is exposed to air that communicates with the air chambers and whose other side is exposed to the liquid that communicates with the liquid chambers. 2. Construction according to claim 1, characterized by a reservoir (27, 136, 246, 292, 293, 361) arranged in the air cylinder for hydraulic fluid, which reservoir communicates with the aforementioned chambers and forms part of the liquid passage. 3. Construction according to claim 2, characterized in that the liquid passage includes one passage (33, 34, 45, 46, 92, 93) leading from each of said chambers to the liquid area, a valve (38, 36, 49, 51 , 97, 100) in each of the passages for controlling the flow through the same, and a one-way valve (39, 37, 47, 48, 161, 162) leading from the storage to each of the passages. 4. Construction according to claim 2, characterized in that the hydraulic piston rod is attached to the end cover of the cylinder (3, 42, 89, 118) and the partition wall is displaceable on the hydraulic piston rod between the air piston and the end cover, that the liquid supply is limited by the partition wall and the end cover , that the fluid passage comprises a pipe (23) which has a passage (26) through the hydraulic piston rod and communicates with the front oil chamber, and which in the interior of the hydraulic piston rod forms an oil passage (29) which is concentric with the first-mentioned oil passage, a device forming a connecting passage (32, 34) between the concentric oil passage and the liquid reservoir, a device forming a connecting passage (28, 33) between the first-mentioned oil passage and the reservoir, and that the liquid flow controlling device comprises flow regulating devices (36, 38) in each of the passages, as well as a non-return valve (37, 39) which leads from the storage to each of the passages. 5. Construction according to claim 3, characterized in that the control device comprises a control housing (40), a pair of pistons (53, 60) which are connected to the passage valves' valve bodies (49, 51) and control these and are movable in the housing, a control valve (72) which is arranged in the housing in the housing and regulates the air passages, a piston (66) which affects the control valve, and an air passage (68) which communicates with the valve pistons and the piston which affects the control valve. 6. Construction according to claim 5, characterized by a first spring (63) which acts on one piston (60) and seeks to move this in the closing direction of one valve, and another spring (56) which acts on the other piston (53) and seeks to move this in the opening direction of the other valve, a control valve (72) arranged in the housing, a third piston (66) acting on the control valve, and an air supply channel (86) with one branch (64) communicating with the first-mentioned piston chamber to move this piston to the closed position, another branch (64) communicating with the control valve piston chamber to move this third piston in the open direction. 7. Construction according to claim 3, characterized in that each of said passages has an opening and that each of the valves (97, 100) is movable to set the size of said openings for regulating the flow through them, a control cylinder (94 ) with a therein reciprocating control piston (103) which carries the valve bodies of the said valves, and connection devices which establish a connection between one of the said chambers and the control cylinder on one side of the control piston and between the other chamber and the other side of the control piston. 8. Construction according to claim 7, characterized by a passage which in the control piston with a non-return valve (113) controls the flow of liquid through the passage, as well as a device (114) which affects said non-return valve periodically. 9. Construction according to claim 1, characterized in that the liquid passage (129, 249, 294) is led through the hydraulic piston (130, 244, 290, 351) which is mounted on the said piston rod and has a limited axial movement on this. 10. Construction according to claim 9, characterized by a hydraulic piston seat (129, 239, 289, 353) which is attached to the hydraulic piston rod having a first position represented by its abutment against the seat, and a second position represented by that it has no contact with the seat, and in the case of devices that form a limited passage from one of the chambers to the other through the hydraulic piston and the seat in the piston's first position, which chambers communicate essentially without restriction with each other in the aforementioned second position. 11. Construction according to claim 9, characterized in that the air piston has an air intake chamber (139), that the air cylinder has a main air chamber on one side of the air piston and another air chamber on the other side of the air piston, that the partition forms a wall in the air intake chamber and separates this from the rear hydraulic fluid chamber, that there is an air passage (133) from the air intake chamber to the main air chamber, an air passage (146) through the air piston from the main air chamber to the second air chamber, and a valve (143) which in one position closes the air passage and in its other position opens this passage.