GB2139382A

GB2139382A - An arrangement for controlling a pneumatic motor

Info

Publication number: GB2139382A
Application number: GB08324891A
Authority: GB
Inventors: Walter Lubos
Original assignee: G Duesterloh GmbH
Current assignee: G Duesterloh GmbH
Priority date: 1982-10-06
Filing date: 1983-09-16
Publication date: 1984-11-07
Also published as: NO862277D0; NO155340B; GB8324891D0; SE8305487L; NO833462L; NO862277L; NO155340C; NO163562C; NO163562B; GB2139382B; SE8305487D0; DE3236908C2; DE3236908A1; SE455087B

Abstract

An arrangement is disclosed for controlling a pneumatic motor 1, which, for example drives a hoist or lift. The arrangement allows the speed of the motor to be controlled, at a desired valve below the nominal speed. The arrangement includes a motor actuating valve 2 connected between the motor 1 and lines 17 and 3 respectively connected with a compressed air source N and, via a spool controller 4, with an exhaust line 26. The spool of the spool controller 4 has control surfaces 8, 13, 14, 21 so adapted to one another that adjustment of the motor actuating valve 2 causes the pressure difference upstream and downstream of said valve 2 to act via a two-way valve 10 on the spool controller 4 in proportion to the load on the motor 1 so as to throttle to a corresponding extent the exhaust flow from the motor. The motor 1 may have two directions of flow and the load may be effectively applied in both directions. A speed controller R is provided and may act to sense one of the pressures acting on the spool, as shown, when a set speed is reached or the inlet fluid, Figs. 2 & 3, not shown. The spool may be constructed as a differential piston (4', Figs. 2 & 3 not shown). <IMAGE>

Description

SPECIFICATION An arrangement for controlling a pneumatic motor THIS INVENTION relates to an arrangement for controlling a pneumatic motor, for example forming part of a transportation installation, in which arrangement, for the purpose of braking rotation of the motor under a torque applied thereto, a controller is provided in the motor exhaust air line, said controller being actuated in dependence on the motor speed and having a closure member for closing the exhaust air line. Such an arrangement is herein referred to as being "of the kind specified".

In a known arrangement of this kind in which the motor is used to raise or lower a load, the motor exhaust air line contains a controller having a closure member the position of which at any time is in a direct relationship with the motor speed once the motor has reached its nominal speed. If the load tends to increase the motor speed beyond the nominal speed, the controller displaces the closure member in order to reduce the cross-section of the exhaust air conduit.

An increasing compression pressure thus forms in the exhaust air conduit and its braking effect ultimately counteracts the accelerational effect of the load. The motor speed is reduced to the nominal speed again. The closure member returns to the initial position.

Consequently, the known controller gives speed control only in the nominal speed range of the pneumatic motor.

In many applications, however, it is desirable or may even be necessary to reduce the pneumatic motor speed to below the nominal speed and yet be able to effect a sensitive speed control indepandently of the size of the load. This is the case, for example, when passengers or loads have to be transported substantially vertically downwards. This occurs, for example in winches for off-shore installations and at the pit-head in underground mining, and also for cranes. A situation of this kind can also occur in underground mining material or passenger transportation installations conveying loads over alternately rising and falling sections. In such cases, the speed of conveyance was hitherto determined only by additional brakes, and not by motor braking, when the load moves in the downward direction.The disadvantages due to the brake constructions and their operation were deliberately tolerated.

It is an object of this invention to provide an improved arrangement of the kind specified by which it is possible, without additional brakes, to control the speed of a pneumatic motor under various loads, for example in a transport installation so that passengers or material can be lowered sensitively and safely.

According to one aspect of the invention there is provided an arrangement for controlling a pneumatic motor in which, for the purpose of braking rotation of the motor under a torque applied thereto, a controller is provided in the motor exhaust air line, said controller being actuated in dependence on the motor speed and having a closure member for closing the exhaust air line, and in which the motor inlet and outlet sides are connected to a continuous-transfer motor actuating valve and the controller has a spool connected to the closure member, and three control surfaces, one of which surfaces is adapted to receive either the pressure of the incoming air from a supply or the pressure of the motor exhaust air via a two-way valve, the second of which surfaces is adapted to be subjected to the input pressure of the incoming air at the motor while the third said surface is adapted to be subjected to the incoming air pressure which, when the motor nominal speed is reached, is adapted to be removed via a speed controller.

According to another aspect of the invention there is provided an arrangement for controlling a pneumatic motor, in which, for the purpose of braking rotation of the motor under a torque applied thereto, a controller is provided in the motor exhaust air line, said controller being actuated in dependence on the motor speed and having a closure member for closing the exhaust air line, and in which the controller has a piston connected to the closure member in the form of a differential piston, of which the end face is adapted to be subjected, via a two-way valve, either directly to the pressure of the incoming air from the supply or the pressure of the exhaust air in the line section between the outlet side of the motor and a continuous-transfer motor actuating valve and the annular face of which is adapted to be subjected to the pressure of the incoming air in the line section between the motor actuating valve and the inlet side of the motor.

Because the controller disposed in the exhaust air conduit is controlledly connected both to the exhaust side and to the incoming air side of the pneumatic motor, where the motor is used to raise and lower a load, the load can be sensitively lowered at any speed below the nominal motor speed irrespective of the size of the load. The control surfaces of the controller spool are preferably so adapted to one another that even minor variations in the pressure ratios between the incoming air side of the motor and the exhaust air side can be utilised in order exactly so to shift the spool controller that the required braking effect occurs.

In a preferred embodiment, in a neutral position, the control element formed by the spool and the closure member is subjected, via the two-way valve, initially basically to the pressure at the incoming air from the supply (which urges it towards the closed position).

The closure member is thus in the closing position and the exhaust air conduit is closed.

If compressed air is then fed to the motor via the motor actuating valve, for the purpose of lowering a load, the throttle effect at the actuating valve produces a pressure difference between the supply and the section of conduit between the actuating valve and the motor intake side. This reduced pressure can then be applied to one control surface and the pressure from the supply can be applied to another surface of the spool and the other side of the control element can be fed, via the two-way valve, with the incoming air pressure from the supply or the exhaust air pressure from the motor, or else the closure member may be subjected solely to the exhaust air pressure of the motor and the end face of the differential piston can be subjected to the incoming air from the supply or to the exhaust air pressure while the piston annular surface can be subjected to the reduced pressure at the motor intake. In either case, the control surfaces co-operate to displace the control element and hence open the exhaust air conduit when the pressure (exhaust air pressure or incoming air pressure) holding the closure member in the closing position is overcome.

This can be carried out sensitively by appropriate opening of the continuous-transfer motor actuating valve. There is therefore a proportional action between the throttling effect at the motor actuating valve and the load to which the motor is subjected.

In a preferred embodiment of the invention in its first aspect, both the spool and the closure member of the spool controller are in the form of stepped pistons having annular surfaces and end faces which are each separately adapted to be subjected to pressure. In this case, the annular surface of the spool can be subjected to the pressure at the motor intake side and the end face can be subjected to the pressure of the incoming air from the supply. The end face of the closure member is subjected, via the two-way valve, either to the pressure of the incoming air from the supply or the pressure of the motor exhaust air on the exhaust side. The closure member has a radial closing action.

Advantageously, the closure member is biased in the direction of its closing position by means of a closure spring. This spring bears, for example, against the annular surface of the closure member. Alternatively, it may bear against the end face of the closure member while the annular surface is subjected to the pressure of the incoming air from the supply or the pressure of the exhaust air on the motor exhaust side. The same change-over can apply to the spool of the control element, i.e., the annular surface is subjected to the pressure of the incoming air from the supply while the end face of the spool is subjected to the pressure at the motor intake side.

The speed controller is preferably connected to a continuous-transfer 2/2 directional control valve connected to the line containing a throttle and leading to that control face of the spool controller which is adapted to be subjected to the removable incoming air pressure.

This is a kind of bypass arrangement the object of which is to remove the supply incoming air pressure from the end face or annular face of the spool when the nominal motor speed is exceeded. The continuoustransfer of the 2/2 directional control valve also provides sensitive control in this case.

The object of the throttle is to ensure that the incoming air cannot immediately flow in fully if the nominal speed is exceeded when the control spool is relieved of load.

Advantageously, a pressure limiting valve is connected to the line leading to the end control face of the spool. This pressure limiting valve enables the maximum pneumatic motor speed to be controlled externally. If operational reasons dictate a maximum speed below the pneumatic motor nominal speed determined by the centrifugal governor, appropriate manipulation can reduce the pressure at the spool end face.

The same effect can be achieved if the circular annular control face of the closure member is connected to the supply via a pressure reducing valve. In this way, a pressure is built up additionally at this control surface of the closure member. The pressure reducing valve can, for example, be disposed in a line connected to the pressure line leading to the two-way valve.

Advantageously, the lines between the spool controller and the line sections connecting the motor actuating valve to the motor contain a 4/2 directional control valve which is adapted to be actuated against a restoring spring together with the motor actuating valve. A 4-quadrant operation can be maintained as a result by means of this 4/2 valve.

In this type of operation it is possible both to change the direction of rotation of the pneumatic motor and apply the load to either side of the pneumatic motor. This is important, for example, in underground gallery transportation systems in which inclines and gradients have to be overcome in alternate and irregular sequence. The 4/2 directional control valve is so coupled to the motor actuating valve that when the latter is in the neutral position and in one of the two actuating positions the 4/2 directional control valve is held in the initial position by the return spring. The 4/2 directional control valve does not change over abruptly until the actuating valve is shifted into the other actuating position.

The motor exhaust air can be discharged to atmosphere via the spool controller. Alternatively, exhaust air which has been compressed to a pressure of above the pressure of the incoming air in the supply can be recycled to the supply. To this end, the exhaust air side of the spool controller may be adapted to be connected to the supply via a 3/2 directional control valve adapted to be actuated by the pressure of the motor exhaust air against the pressure in the supply and, if required, via a return spring, the connection also being via a non-return valve. In the initial position, the pressure of the incoming air from the supply, possibly assisted by a return spring holds the 3/2 directional control valve in an actuating position in which the motor exhaust air fed via the spool controller can be discharged to atmosphere.When the motor exhaust air pressure exceeds the pressure of the incoming air from the supply the 3/2 directional control valve is actuated and the motor exhaust can pass into the supply via the non-return valve.

In a preferred embodiment of the invention in its second aspect, the line between the twoway valve and the piston end face contains a 3/2 directional control valve adapted to be actuated together with the motor actuating valve against a return spring. This arrangement is used when only 2-quadrant operation is required, in which although the direction of rotation of the motor can change the load is applied only to one side of the motor. This is the case, for example, in hoisting winches in off-shore installations, cranes, or underground mining pit-heads without a counterweight. In this embodiment, in the neutral position of the motor actuating valve, the 3/2 directional control valve is held by a return spring in a position in which either the pressure of the incoming air from the supply or the pressure of the motor exhaust air is applied to the differential piston end face.The same position is held by appropriately coupling the 3/2 directional control valve to the motor actuating valve when, for example, it is required to lower a load. Only when a load is to be lifted is the 3/2 directional control valve abruptly changed over in addition to the changeover of the motor actuating valve, the pressure at the piston end face being discharged to atmosphere, the controller opening, so that the exhaust air can pass unobstructed to atmosphere.

In another embodiment of the invention it is second aspect, the lines connecting the controller annular space, on the one hand, and the two-way valve, on the other hand, to the line sections between the motor and the motor actuating valve contain a 4/2 directional control valve which is adapted to be actuated against a return spring. This 4/2 directional control valve again allows 4-quadrant operation, in which it is possible both to change the direction of rotation of the motor and apply the load to either side thereof. The coupling of the 4/2 directional control valve with the motor actuating valve corresponds to the coupling in the above embodiments.

In another embodiment of the invention in said second aspect, the speed controller is disposed in the incoming air line to the motor actuating valve. This speed controller consequently monitors the motor speed and automatically closes the incoming air line if the nominal speed is exceeded.

Finally, advantageously, the motor actuating valve is in the form of a continuous-transfer 4/3 directional control valve which is adapted to be actuated against a return spring in both directions of actuation.

Embodiments of the invention are described below, by way of example, with reference to accompanying drawings, wherein: Figure 1 is a diagram showing an arrangement for controlling a pneumatic motor and constituting a first embodiment of the invention.

Figure 2 and 3 are similar diagrams showing two other embodiments.

For purposes of illustration, the embodiment of Fig. 1 will be considered as applied to a hoist or lift in which the pneumatic motor drives a winch or pulley to raise or lower a load.

Referring to Fig. 1, reference 1 denotes a pneumatic motor with two directions of flow.

A continuous-transfer 4/3 directional control valve 2 is associated with motor 1, the latter being fed with compressed air from the supply N.

In Fig. 1, the valve 2 is in the neutral middle position. The incoming air from the supply N cannot reach the motor 1. Both sides of the motor 1, however, are connected to a spool controller 4 via the 4/3 directional control valve 2 and a line 3, the latter either being connected to or separated from a 3/2 directional control valve 7, depending upon the position of the control element consisting of the spool 5 and the closure member 6. In the control member position illustrated, it is impossible for air to pass through the controller 4. If the brakes (not shown) associated with the motor 1 were released in this condition, and if the motor 1 were subjected to a load, e.g. if a hoist driven by the motor were loaded, downward movement of the load can occur only to an amount determined by the leakage losses of the motor 1.

In the starting position illustrated, the end face 8 of the closure member 6 is subjected to the pressure of the incoming air from the supply N via the line 9 and a two-way valve 10. This pressure is also present at the end face 1 3 of the spool 5 via a throttle 11 and a line 1 2. In this way the control member is biased towards the closed position illustrated by the pressure at the end face 8 and by the closure spring 1 5 which bears against the annular surface 14 of the closure member 6.

If compressed air is now fed to the motor 1 by a slight movement of the 4/3 directional contol valve 2 in the direction of arrow P by means of lever 16, the throttle effect in the 4/3 directional control valve 2 results in a differential pressure in the supply line 1 7 relative to the section of line 18 between the valve 2 and the motor 1. The reduced pressure in section 18 is then applied, via line 1 9 and a 4/2 directional control valve 20, to the annular face 21 of the spool 5 in the spool controller 4. The pressure of the outgoing motor air in the line section 22 between the 4/3 directional control valve 2 and the motor 1 is also present at the two-way valve 10 via the line 23 and at the control head 25 of the 3/2 directional control valve 7 (which will be explained hereinafter) via line 24.

Appropriate dimensioning of the control surfaces 8, 13, 14 21 at the spool controller 4 causes the pressures available from the line sections 1 8 and 22 between the valve 2 and the motor 1 and from the lines 9, 12 to open the spool controller 4 only to an extent predetermined by the displacement of the valve 2.

There is consequently a direct proportionality between the load on the motor 1 and the displacement of the control member 5, 6 in the spool controller 4.

The exhaust air leaving the spool controller 4 flows via line 26 to the 3/2 directional control valve 7 and through the latter to atmosphere. This position of the valve 7 is ensured by the pressure of the incoming air from the supply N' at the control head 28 of the valve 7 via line 27. As a safety precaution, valve 7 also has a return spring 29 which also holds it in that position in the event of absence of the pressure. It will also be seen that the non-return valve 30 is disposed between the supply N' and the 3/2 directional control valve 7, said valve 30 opening towards the supply N'.

When the compression pressure in line section 3 between valve 2 and spool controller 4 reaches a.value in excess of the pressure of the incoming air in line 9 or 27, the two-way valve 10 changes over so that the end face 8 of the closure member 6 then receives this exhaust air pressure and at the same time the 3/2 directional control valve 7 changes over.

The exhaust air then flows via 3/2 directional control valve 7 and non-return valve 30 to the supply N'.

When the motor 1 monitored by the controller R reaches the nominal speed and if it exceeds this nominal speed slightly, controller R automatically shifts its associated 2/2 directional control valve 31 into the open position so that the end face 13 of the spool 5 is connected to atmosphere via line 32. As a result the pressure at spool 5 decreases and the pressure at closure member 6 predominates so that the exhaust air line 3 is closed.

The speed of motor 1 decreases as a result of the high compression pressure counteracting the load on the motor. Throttle 11 prevents excessively fast inflow of air to the end face 13 of spool 5.

If the motor 1 is to be actuated in the other direction of rotation, the 4/3 directional control valve 2 is changed over by means of lever 16. The latter is moved in the direction P1, the 4/2 directional control valve 20 simultaneously being abruptly changed over into the other position of the sector disc S against the restoring force of spring 33. In this way line section 1 8 is now connected to the two-way valve 10 and the line section 22 is connected to the control face 21.

Fig. 1 shows another arrangement which must, however, be regarded as present only in a variant. In this variant a pressure limiting valve 46 is connected to line 12. By means of this valve 46, the speed of the motor 1 can be controlled from outside to any value below the maximum speed predetermined by the centrifugal governor R.

In another variant the chamber in which is exposed the annular face 14 of closure member 6 is connected to line 9 via a pressure reducing valve 47 so that the annular face 14 is not subjected directly to atmosphere. Speed control is therefore also possible with the pressure reducing valve 47 just as with the pressure limiting valve 46.

In the embodiment shown in Fig. 2, the pneumatic motor is again denoted by reference 1, and has two directions of flow with an associated 4/3 directional control valve 2 as in the embodiment shown in Fig. 4. The incoming air from the supply N is fed to the 4/3 directional control valve 2 via a speed controller R which is initially in the neutral middle position. The incoming air is also fed via line 34 to a two-way valve 10 and flows, via a 3/2 directional control valve 35 which can be actuated together with the 4/3 directional control valve 2, and a line 36, to the end face 37 of differential piston 38 forming part of a spool controller 4'. The end face 37 of piston 38 is also biased by a closure spring 39.

The pressure of the incoming air holds a closure member 40 connected to piston 38 in the closed position, so that the motor 1 is supported on both sides without being subjected to loading.

The annular face 41 of differential piston 38 is connected via a line 42 to the line section 18 between the 4/3 directional control valve 2 and the pneumatic motor 1. The other line section 22 between the 4/3 directional control valve 2 and the pneumatic motor 1 is connected to the two-way valve 10 via a line 45.

If the 4/3 directional control valve 2 is moved to the right in the direction of arrow P by means of lever 16, it allows the incoming air to flow to the line section 18 so that there is again a differential pressure between the supply line 1 7 and the line section 1 8. This differential pressure plus the pressure from the exhaust air line 43 shifts the differential piston 38 and the closure member 40 in opposition to the pressure at the end face 37 of the differential piston 38 plus the closure spring 39 if the latter pressure is higher, so that the closure member 40 allows the exhaust air to escape to atmosphere. The same situation occurs when the pressure in the line section 22 between the 4/3 directional control valve 2 and the motor 1 exceeds the incoming air pressure at the two-way valve 10, so that the latter changes over.

The speed controller R again ensures that the incoming air is shut off in the event of the nominal speed being exceeded, so that the spool controller 4' closes and the acceleration energy of the motor 1 drops so as to reduce the speed, as a result of the compression pressure increasing in these circumstances.

If the motor 1 is reversed, i.e. by the 4/3 directional control valve 2 being moved in the direction of the arrow P1, the 3/2 directional control valve 35 is also actuated simultaneously so that the pressure at the end face 37 of the differential piston 38 is removed. The pressure of the exhaust air in line section 1 8 between the 4/3 directional control valve 2 and the pneumatic motor 1 is present at the closure member 40 and at the annular face 41 and shifts the differential piston 38 to the right so that the pneumatic motor 1 can rotate freely.

This embodiment therefore relates to an arrangement in which the motor 1 has two directions of flow but the load can be applied only in one direction of operation of the valve 2.

The embodiment in Fig. 3 is substantially the same as that in Fig. 2 except for the fact that a 4-quadrant operation is possible by incorporating a 4/2 directional control valve 44 which is controllable by the 4/3 directional control valve 2. In this type of operation, the direction of rotation of the motor 1 can vary and the load can also be applied in both directions of operation of the valve 2.

To this end, the two-way valve 10 is directly associated with the end face 37 of the differential piston 38. On one side it is subject to the pressure of the incoming air from the supply N and on the other side to the pressure of the exhaust air from the line sections 18, 22 respectively disposed on the exhaust side of the motor 1.

The operation is otherwise the same as that of the arrangement shown in Fig. 2.

Claims

1. An arrangement for controlling a pneumatic motor in which, for the purpose of braking rotation of the motor under a torque applied thereto, a controller is provided in the motor exhaust air line, said controller being actuated in dependence on the motor speed and having a closure member for closing the exhaust air line, and in which the motor inlet and outlet sides are connected to a continuous-transfer motor actuating valve and the controller has a spool connected to the closure member, and three control surfaces, one of which surfaces is adapted to receive either the pressure of the incoming air from a supply or the pressure of the motor exhaust air via a two-way valve, the second of which surfaces is adapted to be subjected to the input pressure of the incoming air at the motor while the third said surface is adapted to be subjected to the incoming air pressure which, when the motor nominal speed is reached, is adapted to be removed via a speed controller.

2. An arrangement according to claim 1, in which both the spool and the closure member of the spool controller are in the form of stepped pistons having annular surfaces and end faces which are each separately adapted to be subjected to pressure.

3. An arrangement according to claim 1 or 2, in which the closure member is biased in the direction of its closing position by means of a closure spring.

4. An arrangement according to claim 1, in which the speed controller is connected to a continuous-transfer 2/2 directional control valve connected to a line containing a throttle and leading to that control face of the spool controller which is adapted to be subjected to the removable incoming air pressure.

5. An arrangement according to claim 4, in which a pressure limiting valve is connected to said line leading to the said control face of the spool which is adapted to be subjected to the removable incoming air pressure.

6. An arrangement according to claim 2 or 3, in which the circular annular control face of the closure member of the spool controller is connected to the supply via a pressure reducing valve.

7. An arrangement according to any preceding claim in which the lines between the spool controller and the line section connecting the motor actuating valve to the motor contain a 4/2 directional control valve which is adapted to be actuated against a restoring spring together with the motor actuating valve.

8. An arrangement according to any preceding claim in which the exhaust air side of the spool controller is adapted to be connected to a further supply via a 3/2 directional control valve adapted to be actuated by the pressure of the motor exhaust air against the pressure in the first mentioned supply and, if required, via a return spring, the connection also being via a non-return valve.

9. An arrangement for controlling a pneumatic motor, in which, for the purpose of braking rotation of the motor under a torque applied thereto, a controller is provided in the motor exhaust air line, said controller being actuated in dependence on the motor speed and having a closure member for closing the exhaust air line, and in which the controller has a piston connected to the closure member in the form of a differential piston, of which the end face is adapted to be subjected, via a two-way valve, either directly to the pressure of the incoming air from the supply or the pressure of the exhaust air in the line section between the outlet side of the motor and a continuous-transfer motor actuating valve and the annular face of which is adapted to be subjected to the pressure of the incoming air in the line section between the motor actuating valve and the inlet side of the motor.

10. An arrangement according to claim 9 wherein said end face of the differential piston is also acted on by a closing spring.

11. An arrangement according to claim 9 or claim 10, in which the line between the two-way valve and the piston end face contains a 3/2 directional control valve adapted to be actuated together with the motor actuating valve against a return spring.

1 2. An arrangement according to claim 9 or claim 10, in which the lines connecting the controller annular space, on the one hand, and the two-way valve, on the other hand, to the line sections between the motor and the motor actuating valve contain a 4/2 directional control valve which is adapted to be actuated against a return spring.

1 3. An arrangement according to any preceding claim in which the motor actuating valve is in the form of a continuous-transfer 4/3 directional control valve which is adapted to be actuated against a return spring in both directions of actuation.

14. An arrangement for controlling a pneumatic motor, substantially as hereinbefore described with reference to, and as shown in, Fig. 1 of the accompanying drawings.

1 5. An arrangement for controlling a pneumatic motor, substantially as hereinbefore described with reference to, and as shown in, Fig. 2 of the accompanying drawings.

1 6. An arrangement for controlling a pneumatic motor, substantially as hereinbefore described with reference to, and as shown in, Fig. 3 of the accompanying drawings.

17. Any novel feature or combination of features described herein.