US2899131A - Controlling means for rotary machines - Google Patents

Description

Aug. 11, 1959 v. WOHLER 2,899,131

CONTROLLING MEANS FOR ROTARY MACHINES Filed Sept. 6, 1955 O O '2 Sheets-Sheet 1 INVENTOR VIK TOR WOHLER ATTORNEYS g- 11, 5 V.VWOHLER I 2,899,131

CONTROLLING MEANS FOR ROTARY MACHINES Filed Sept. 6, 1955 2 sheets-sheet 2 FIG. 2-

INVENTOR VIKTOR WOHLER ATTORNEYS United States Patent CONTROLLING MEANS FOR ROTARY MACHINES Viktor Wohler, Therwil, Switzerland, assignor to Ciba Limited, Basel, Switzerland, a Swiss firm Application September 6, 1955, Serial No. 532,451

Claims priority, application Switzerland September 3, 1954 7 Claims. 01. 233-1 The present invention relates to controlling means for rotary machines. In many industrial rotary machines, the shafts continue to rotate by inertia after the driving force has been interrupted. Many of these machines have parts, especially covers, which for safety in operation should not be moved, for example opened, until the machines are at a standstill. In the following description and claims the word open as applied to this part is intended to mean the position which is only desired while the shaft of the machine is stopped. The above is a requirement, for eX- ample, with some mixing and grinding machines and especially with centrifuges, in the case of which there is considerable danger of injury if opening of the cover can take placeduring operation. The present invention is of especial advantage for use with relatively large centrifuges, which are of wide application in industry and most of which have a fairly heavy cover which owing to its weight is difficult to open by hand. In the following description the invention will be considered in greater detail as applied to centrifuges.

In the case of centrifuges it is of importance to maintain the cover closed during operation, to preclude the possibility of accidents, and also to prevent spilling of liquids or penetration of foreign bodies or excess of material into the centrifuge during the operation, which would lead to unbalanced distribution of the load, and thus to a possibility of damage to the machine. A further difliculty arises in the case of centrifuges that when the drive is stopped they would take much too long to come to a standstill if left to themselves so that an effective braking must be employed. There is therefore a need in the case of centrifuges for a simple and safe means for rendering largely automatic the necessary operations in starting and stopping.

The present invention provides controlling means for rotary machines, the shafts of which continue to rotate by inertia after the driving force has been interrupted and which have a movable part intended to be closed during rotation of the shaft and opened only when the shaft is stopped, said controlling means comprising a fluid pressure system for opening said part and for maintaining it in the closed position, means operated from the shaft and adapted to interrupt the application of opening fluid pressure while the shaft is rotating, and means enabling fluid pressure used to open said part and fluid pressure produced in closing said part to interrupt the supply of motive power to the machine.

The invention is illustrated diagrammatically in the accompanying drawings in which Fig. 1 shows the lay-out of a centrifuge system with fluid pressure operation, and I Fig. 2 shows the lay-out of a centrifuge system with combined electrical and fluid pressure operation.

Referring to Fig. 1, a centrifuge is shown at 10. Its cover 11 is provided with a rigidly attached lever 12 and can be pivoted about pivot 13. The lever 12 is connected by rod 14 with piston 16 in cylinder 15.

As operating fluid there can be employed for example in the means provided by the present invention, water from a water supply line. A particularly simple modification is provided, however, by the use of compressed air. Since in chemical plants compressed air lines are normally available for various purposes, the use of compressed air is generally possible without additional expense. Fluid pressure may be used for both the control and the drive of the machine.

For driving the centrifuge an electric motor can also be used. In view of the difficulty of protecting the motor against the corrosive influences of the atmosphere and of liquids which may be present, it may be more advantageous to drive the centrifuge with a water turbine, for example of the type of the Pelton turbine. Such turbines can easily be provided with a braking device, which may consist for example of a set of turbine blades adapted to drive in the direction contrary to the normal running direction and on which fluid can impinge from a separate nozzle, or more simply by admission of a pressure fluid to the back of the already existing blades through a separate nozzle, or finally by deflecting the driving water stream so as to impinge on to the back of the blades. These turbines in addition possess the advantage of entailing no additional danger in spaces subject to the occurrence of explosions; they allow alteration of the speed of rotation during the operation and render possible a large number of startings and stoppings within a particular time interval because the heat normally produced in braking is dissipated in the water.

Thus, the drive of the centrifuge 10 in Fig. 1 takes place by means of a turbine 17. This comprises blades 18, the forward driving faces of which are impinged upon by water under pressure from a nozzle-valve 19 and the rear faces 20 are impinged upon by water under pressure from a similar nozzle-valve 21. Driving nozzle 19 is controlled by a piston 25 working in cylinder 22, and the braking nozzle 21 is controlled by piston 26 working in cylinder 23. Springs 24 urge the two pistons into the closed positions of the corresponding nozzle-valves when the air in the cylinders is not under pressure. The water for driving and braking the turbine is supplied through conduits (not shown in Fig. 1).

In conjunction with the means of the present invention, the problem of measuring the number of revolutions per minute of a centrifuge can also be solved advantageously and in a simple manner. Accordingly, a gear pump 27 is also coupled with the driving shaft. When the centrifuge is in operation, this pump pumps oil from oil reservoir 28 through restrictor 29 and back into oil reservoir 28. The restrictor represents a resistance in the oil pumping circuit and the pressure existing in front of this resistance may be measured by manometer 30. By suitable calibration of the manometer the number of revolutions per minute of the centrifuge can be read off directly at any particular moment. i

The nozzles 19 and 21 are operated by compressed air which is supplied to the cylinders 22 and 23, respectively, from a supply line 40 through an air filter 49, a release valve 33, a four-way cock 31, conduits 41 and 42 respectively and restrictors 36.

In a preferred embodiment of the invention, especially in the case of fluid pressure driven centrifuges, the method of operation for starting and stopping can be particularly simply arranged when two coupled four-way cocks are used of which one controls the raising and lowering of the cover and the other the redirection of the driving energy from driving to braking. By a combination of the two control means, the advantage is provided that by simply operating one control element, the centrifuge is shut off, stopped and the cover only opened after the centrifuge has come to a standstill. On the other hand a reversal of the direction of rotation of the centrifuge I is prevented as the braking power is shut 011 by the automatic control once the centrifuge has come to a standstill and the cover is open. v

The opening and closing of the cover 11 is likewise effected by compressed air from the supply line 40, transinitted to cylinder 15 through a four-way cock 32 (which is" coupled to the cock 31), and either a valve 35 (which is controlled as described below), \a restrictor 37 and a conduit 43 or a conduit 44 respectively. A valve 34 is provided which is operated by oil-pressure in the oil line of the manometer 30 by connection with conduit 45. Valves 33, 34 and 35 are of the type wherein fluid pressure is applied to a movable member, such as a piston or a diaphragm. Under the action of this pressure the movable memberactuates a cooperating control element, viz. it'opens or closes a fluid valve in case of valve 35, it sets to one 'of its two positions an escapement valve in case of valve 33, or it moves to orfro a hinged lever in case of valve 34, which lever closes or leavesfree a nozzle 39. Thus valve 34 leaves free nozzle 39 when a sufiicient oil pressure prevails in the manometer oil .line and thus, in conjunction with a variable restrictor 38, prevents opening of the valve 35.

This is due to the fact that the air passing through restrictor 38 may escape freely through the nozzle 39 audits pressure is consequently too low to actuate, i.e. open, valve 35.

i The method of operation of the arrangement shown in Fig.1 is as follows;

7 The indicated. position of all parts, particularly of the four- way cocks 31 and 32, corresponds to a running centrifuge. Compressed air is conveyed to the cylinder 22-and the valveat 19 is open. On the other hand no air pressure is exerted upon the piston in cylinder 23 because passage to the atmosphere is open through the conduit 42 and the cock 31. The cover is kept closed due to its own weight and to the air pressure maintained in the lower part of the cylinder 15. The manometer 30'indieates an oil pressure corresponding to the rate of rotation of pump 27. v

' To stop the centrifuge, the coupled four- way cocks 31 and 32 are turned in clockwise direction through 90. The turning of the cock 31 has the immediate effect that the driving nozzle valve 19 is closed and the braking nozzle valve 21 is opened. On account of the pressure prevailing in the oil line of the manometer, the valve 34 remains open i.e. leaves nozzle 39 free and permits the compressed air to escape freely through this nozzle, as long as the centrifuge is rotating to any appreciable extent. Compressed air passing through the restrictor 38 thus escapes through the nozzle 39. The compressed air passing through cock 32 only proceeds as far as valve 35. Valve 35 thus remains closed and the cover is not yet lifted nor the valve 33 shifted to the out position indicated by a broken line. When, as a result of braking, the centrifuge has practically come to a standstill, the valve 34, now relieved of pressure, closes nozzle 39.

. 4 limits the speed of air issuing from the cylinder. On starting the centrifuge again,- the coupled cocks 31 and 32 are turned into their original positions as illustrated, but again the cover only falls slowly because the air contained in the upper part of the cylinder requires a certain amount of time to escape through the restrictor 37. During the time of closing of the cover, pressurein conduit 43 simultaneously acts upon release valve 33 so that during this time compressed air cannot pass through the cock 31 into the cylinder 22 and therefore rotation of the'centrifuge cannot commence until the coveris-fully closed.

Owing to double control by the valves 34 and 35 on the one hand and the release valve 33 on the other The controlling pressure at valve 35 rises until valve 35 i opens. Compressed air from the supply line 40 through turned cock 32 and restrictor 37 now on the one hand brings release valve 33 to the broken-line position and on the other hand through conduit 43 enters the upper part of the cylinder 15thereby causing opening of the cover 11. The pressure prevailing in conduit 43 also actuates the release valve 33, which is thereby brought to.the position indicated in broken lines, in which compressed air from line 40 is. shut off, but pressure from conduit 42 may escape through cock 31, and valve 33,

It thus releases the compression in the cylinder 23, closes valve 21, and thus interrupts the braking action upon the centrifuge. i

Incase of a sudden fall of pressure in compressed air supply line 40,. the covermay fall under its own weight, but it canonly do so. slowly as restrictor 37 hand, provision is made for a fully automatic stopping procedure, with the guarantee that in spite of the simultaneous turning of the coupled cocks 31 and 32, the opening of the cover can only take place after the centrifuge has come practically to a'standstill and moreover the centrifuge can only be started up again after the cover has closed.

Moreover, owing to the fact that the cover is automatically raised when the machine comes to a standstill, reversal of the rotation by continuation of the braking effect is also prevented, which is only possible with difficulty in the case of hand-operated Pelton nozzles.

The present invention is however also applicable when the drive is effected by means of electric motors using a braking system of known type, for example a mechanical system, or by suitable wiring of the electric motor itself for braking of the centrifuge.

Referring to Fig. 2, the parts 10 to 16, 32, 37, 40, 43, 44, and 49 are analogous to the corresponding parts shown in Fig. 1. In this case, however, the centrifuge itself is operated by an electric motor 60 driven by 380 volt 3-phase current fed through a solenoid switch 61 operated by a 220 volt control line. To the common shaft of centrifuge and motor is mechanically attached an electric switch 52 which is closed while the centrifuge is revolving but which interrupts the electrical connection between conductors 58 and 59 when the centrifuge comes to a standstill. I Instead of the four-way cock 31 shown in Fig. 1, there is used in the case of Fig. 2 an electric hand switch 54 and instead of fluid pressure braking, mechanical braking is used (by means not illustrated). Furthermore the pneumatic valve 35 of Fig. 1 is replaced by a solenoid valve 51, and the release valve 33 of Fig. 1 by a pressure controlled switch 53 which interrupts the 220 volt control current as soon as fluid pressure is exerted in the conduit 43. Finally, Fig. 2 shows another valve 50 which only allows compressed air to pass from the conduit 44 through the conduit 48 to the lower part of the cylinder; 15 when the cover is completely closed. This has the advantage that the cover 11 closes under its own weight ,only, with a corresponding reduction in danger to operatives of being caught by the closing cover.

I The method of operation of the arrangement according to, Fig. 2 is in the main analogous to that of Fig. 1. In this case also thepositions of the parts shown in the drawingcorrespond to running of the centrifuge under power, except for switches 54 and 61 which are shown in open position in order to indicate their switch character better, but whichare actually closed at this moment. To stop the centrifuge, the four-way cock 32 is turned through in an anticlockwise direction and the hand switch 54 thrown off. Until the centrifuge has come to a standstill, the 220 volt control current circuit remains made by way of the solenoid valve 51, the switch 52 and the conductors 58 and 59, and the solenoid valve 51 does not allow compressed air for lifting of the cover to pass into the conduit 43. As soon as the machine has come to a standstill, the solenoid valve 51 is reversed. Simultaneously with the raising of the cover, the pressure controlled switch 53, to which compressed air is now supplied, interrupts the current passing to the hand switch 54. While the cover is open and during the closing of the cover, the electric motor therefore cannot be started up by actuation of the hand switch 54.

It is obvious that the restrictors 37 may be omitted in both Fig. 1 and Fig. 2, if other parts through which the fluid has to pass for example cock 32 are made sufliciently narrow as compared with the area of the piston 16. Furthermore, it appears from Fig. 1 that valve 35 which is closed when the centrifuge is running prevents any opening of the cover 11 by hand because subatmospheric pressure would be produced above piston 16 thus preventing any substantial movement of piston 16 even without superatmospheric pressure being applied to its lower surface. On the other hand the lay-out of Fig. 1 requires a completely tight fitting of piston 16 and valve 35 because otherwise pressure would slowly build up in conduit 43 thus leading to a reversal of valve 33.

In Fig. 2 the same does not apply because conduit 43 is directly connected with the atmosphere while the centrifuge is running and therefore the cover might be opened by hand immediately after reversal of the cock 32, although this can hardly be done in view of the heavy weight of the cover.

What is claimed is:

1. In a rotary machine of great inertia and having a rotary shaft and also having movable parts intended to be closed during rotation of said shaft and opened only when said shaft is stationary, a source of supply of motive power for said machine, automatic control means comprising a fluid pressure system for moving said movable parts to and from open and closed positions, switching means for operating said pressure system, locking means incorporated in the pressure system for reciprocally locking the drive of the machine and of said movable parts, means operated by the rotary shaft of the machine interrupting the application of opening fluid pressure to the control means while the said shaft is rotating, and means operated by the fluid pressure for interrupting the supply of motive power to the machine while the fluid pressure used to open the movable parts persists and also while the fluid pressure existing during closing of the said parts persists.

2. Automatic control means for the cover of a centnifuge having a rotary shaft, a source of supply of motive power for said centrifuge, said control means comprising a fluid pressure system for opening and closing the said cover, first valve means operated by the said shaft interrupting the application of opening fluid pressure to said control means while the shaft is rotating, and second valve means interrupting the supply of motive power to the centrifuge, said second valve means being operated by the fluid pressure serving for opening said cover and also being operated by the fluid pressure existing during the closing of the cover.

3. In a centrifuge provided with a cover intended to be closed during rotation of the centrifuge, a rotary centrifuge shaft, a source of motive power for said centrifuge, a fluid pressure system, two four-way cocks in said system fixedly coupled for common movement, the first cock in one position directing the fluid pressure to maintain the cover closed and the second cock in the corresponding position actuating means for supplying motive power to the centrifuge, and the first cock in a second position thereof directing the fluid pressure to open the cover and the second cock in its position corresponding to said second position actuating means for stopping the centnifuge, first means mechanicmly connected to and operated by the shaft of the centrifuge, and second means operated by the pressure existing in the part of the pressure system serving for opening the said cover, said first means interrupting the application of opening fluid pressure to the cover while the shaft is rotating and said second means interrupting the supply of motive power to the centrifuge.

4. In a rotary machine as claimed in claim 1, the means operating the shaft including an oil circulation system, an oil pump driven by said shaft and supplying pressure oil to said circulation system, a restrictor in said system, and valve means operated by the pressure in the oil circulation system of the machine, said valve means interrupting the fluid pressure for opening the said cover.

5. Controlling means as claimed in claim 4, and a pressure gauge in the oil circulation system serving as a revolution counter for the rotary machine.

6. In a rotary machine as claimed in claim 2, the means operating the shaft including an oil circulation system, an oil pump driven by said shaft and supplying pressure oil to said circulation system, a restrictor in said system, and valve means operated by the pressure in the oil circulation system of the machine, said valve means interrupting the fluid pressure for opening the said cover.

7. In a rotary machine as claimed in claim 3, the means operating the shaft including an oil circulation system, an oil pump driven by said shaft and supplying pressure oil to said circulation system, a restrictor in said system, and valve means operated by the pressure in the oil circulation system of the machine, said valve means interrupting the fluid pressure for opening the said cover.

References Cited in the file of this patent UNITED STATES PATENTS 2,591,317 Tholl Apr. 1, 1952

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