US 3613892 A
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United States Patent Inventor Fritz Ziller Essen, Germany Appl. No. 783,631 Filed Dec. 13, 1968 Patented Oct. 19, 1971 Assignee Alia-Laval Bergedorfer Eisenwake G.m.b.H Hamburg-Bergedort, Germany Priority Dec. 14, 1967 Germany P 16 32 272.8
STROKE CONTROL FOR THE PUSH BOTTOM OF A PUSH CENTRIFUGE 4 Claims, 1 Drawing Fig. US. Cl 210/374, 91/275 Int. Cl F011 25/08, B04b 3/02 Field of Search 91/275;
References Cited UNITED STATES PATENTS 2,462,098 2/1949 l-lertrich 210/374 2,604,079 7/1952 Ray 91/275 2,755,966 7/1956 Linders..... 91/275 2,803,110 8/1957 Chittenden. 91/275 2,904,010 9/1959 Yingst 91/275 Primary Examiner-Paul E. Maslousky AnomeyWalter Becker ABSTRACT: A stroke control device for the push bottom of a push centrifuge having a pressure fluid drive for reciprocating said push bottom, and valve means adapted to reverse the flow of pressure fluid, said stroke control device comprising an electric impulse transmitter mounted for reciprocating movement with said push bottom and adapted for contact-free impulse transfer, two impulse-receiving initiators located along the path of said transmitter and adapted to initiate electric control pulses in response to the approach of said transmitter, and valve control means operating said valve means in response to said control pulses.
STROKE CONTROL FOR THE PUSH BOTTOM OF A PUSH CENTRIFUGE The present invention relates to a stroke control device for the push bottom of a push centrifuge having a pressure fluid drive for reciprocating the push bottom, said pressure fluid drive comprising a cylinder connected to'the centrifugal drum for rotating movement therewith, a piston operatively connected with said push bottom for reciprocating movement within said cylinder and said drum, respectively, a pressure fluid system connected to said cylinder for reciprocating said piston, and valve means adapted to reverse the flow of pressure fluid to and from said cylinder.
Specifically, the present invention concerns a control device for the push bottom stroke, the adjustment of the length of the push bottom stroke, and the adjustment of the position of the push bottom stroke along thelongitudinal axis of the drum. These necessary movements are difficult to control because the cylinder and the piston of the drive rotate with the frequently rather high speed of the centrifuge so that the transmission of the control impulse in a hydraulic or mechanical manner is, in view of the inertia and lack of precision not suitable, since particularly a direct contact between the stationary and rotating control elements must be avoided, and with heretofore known controls the last mentioned possibility of a displacement of the push bottom stroke is impossible without difficult changes within the machine.
As pressure medium for the drive of the push bottom for all practical purposes only pressure fluid is suitable, which means primarily a hydraulic oil. Accordingly, the control member for the driving piston is adjusted for a periodically alternating reverse of the pressure oil flow. It is this type of control which is also used in the present invention.
It is an object of the present invention to provide a stroke control device for the fluid pressure drive for the push bottom of a push centrifuge which will operate at a high speed and at great precision without mechanical transfer of movement between the moving and the stationary elements.
It is another object of this invention to provide a control, as set forth in the preceding paragraph, which will make is possible in a simple manner to adjust the stroke and the location of the reversing point of the driving piston.
These and other objects and advantages of the present invention will appear more clearly from the following specification in connection with the accompanying drawings, in which:
FIG. 1 diagrammatically illustrates in section a first embodiment of an electronic control according to the present invention.
The device according to the present invention is characterized primarily, in that an electric impulse transmitter taking part in the piston movements is arranged between two impulse receiving initiators which at different stroke lengths are located in the path of the impulse transmitter and are operatively connected to valve control means adapted to operate the valve means for reversing the piston movement.
The control pulses may, if desired, be electrically reinforced before they are conveyed to the electromagnetic drive of the valve control means.
The transfer of the impulses is preferably effected by capacitive, inductive, or in particular, electronic means. The electronic means are to be given preference because of their precise and delay-free action. The time wise course of the movements of the push bottom, for instance, its standstill between each two strokes may furthermore be influenced in accordance with the present invention by having the impulse receiving initiators followed by a pulse-storing device which releases the pulses only after a certain adjustable time period to the valve control means.
The electromagnetic valve control means actuated by the impulse receiving initiators, if desired through a pulse amplifier, may directly operate the valve means for reversing the pressure fluid drive of the push bottom piston. In case of greater force requirements the valve control means may actuate servocontrol means for the main valve.
Referring now to the drawing in detail, the centrifugal drum 1 of a push centrifuge is, by means of its hollow shaft 2 which merges with the cylinder 3, joumaled in a stand 4. The push bottom 5 rotating together with drum 1 has its shaft 6 and a piston 7 mounted thereon reciprocably arranged in the hollow shaft 2 or cylinder 3. The end face of the hollow cylinder 3 merges with a narrow cylinder 8 into which the piston 7 or shaft 6 extend with a transmitter element or element 9. With the exception of the stand 4, the parts 2-9 rotate at the same speed as the drum 1.
According to FIG. 1, the push bottom 5 occupies its starting position 1 near the bottom of the drum. When the piston 7 in its pertaining starting position is acted upon by oil under pressure through conduit 10, passages 11 and 12, shaft bore 13, and the openings 14, the piston 7 moves toward the right and displaces the push bottom 5 to its end position e The transmitter element 9 takes part in this displacement and is moved from its first end position until at the end of the stroke it is located in its second end position e opposite an impulsereceiving initiator 15 and produces therein a current control pulse which is conveyed through a pulse-storing device 16 and a transistor amplifier 7 to a magnetic valve control device 18 with the result that a four-way valve 19 which up to said point had, by means of its intercrossing passages, connected the pressure conduit 20 (plus sign in drawing represents pressure and minus sign represents return without pressure) of a pressure-oil system with the conduit l0, is moved into the illustrated position in which said four-way valve 19 through the pressure conduit 21 and the annular chambers 22 and 23 conveys pressure fluid to the right-hand side of piston 7 so that the latter returns to its starting position a and therewith also the push bottom 5. In this starting position, the transmitter element 9 actuates a second impulse-receiving initiator 24 so as to operate said magnetic valve control device 18 to reverse valve 19 with the result that the piston 7 reverses its stroke and also the push bottom 5 moves in the push direction For purposes of adjusting the displacement of the stroke of the push bottom 5, there are provided the two initiators l5 and 24 which are longitudinally displaceable relative to cylinder 8. If the initiator 15 is located in the first end position a and the initiator 24 is located in the second end position e, the transmitter element 9, the drive piston 7 and together with the latter also the push bottom 5 carry out their maximum working stroke which starts from the position a of the bottom 5 and ends in the position g. If the initiator 15 is displaced so as to occupy a medium position m (shown in broken lines in the figure) and if the initiator 24 is left in its position a, the reversing is effected as soon as the transmitter element 9 will be located opposite position m of the initiator 15 which means after a corresponding short-working stroke of the push bottom 5 in reversing position 21.
If, however, the initiator 24 is displaced into the position m (shown in broke lines in the figure) while the initiator 15 is left in its end position e the reversal of the return stroke takes place already when the transmitter element 9 passes into the region of the position 2 of the initiator 24. As a result thereof, the start of the stroke of the push bottom 5 is displaced to the position m and the effective length of the drum 1 is changed. By displacing both initiators, it is possible analogously to displace both reversing positions of the push bottom 5. By means of the pulse storing device 16 it is possible to adjust the time at which the pulses are conveyed to the magnetic valve control device 18. in this way it is possible to control the timewise course of the movement of the push bottom 5.
The electric and in particular electronic control according to the invention makes it possible in view of the contact-free operation by means of members 15, 24, 16, and 17 to adjust the reversing point for the push bottom 5 steplessly in axial direction and to carry out the reversing operation precisely at the predetermined point, and more specifically, independently of the thrust and speed of the drum, and also independently of the viscosity of the oil, the type of material to be centrifuged and independently of thefinishing tolerances. In this way the push centrifuge will be able to operate precisely within the optimum range for the respective product. In view of the adjustment of one or both reversing points by simple means, it is possible to vary the effective length of the drum at any desired time without interrupting the operation of the drum. With the same advantages, the present invention is also applicable for reversing similar reciprocatory piston movements by means of a fluid pressure drive.
As will be evident from the above, the control according to the present invention operates fast and with high precision and without mechanical transfer of the movement between moving members and stationary members. The invention also makes it possible in a simple manner to adjust the stroke and the position of the reversing point of the drive piston by changing the relative position of the impulse receiving initiators.
It is, of course, to be understood that the present invention is, by no means, limited to the particular showing in the drawings, but also comprises modifications within the scope of the appended claims.
What I claim is:
1. A stroke control device for a push bottom of a push centrifuge having a rotatably joumaled hollow shaft, a centrifugal drum mounted on said hollow shaft for rotational movement therewith, an inner shaft axially movable within said hollow shaft, a push bottom mounted on said inner shaft for axial movement within said drum, a cylinder coaxially mounted on said hollow shaft for rotational movement therewith, a piston coaxially mounted on said inner shaft for reciprocating movement within said cylinder, a pressure-fluid system having pressure fluid conduits connected to said cylinder for reciprocating said piston, said inner shaft and said push bottom, and valve means disposed in said pressure fluid conduits and adapted to reverse the flow of pressure fluid to and from said cylinder, said stroke control device comprising in combination: an electric impulse transmitter mounted for rotational and reciprocating axial movement together with said piston between first and second end positions and adapted for contact-free, preferably inductive impulse transfer, two impulsereceiving initiator means located along the path of said transmitter in the end positions thereof and adapted to initiate an electric control pulse in response to said impulse received upon the contact-free approach of said transmitter, and valve control means operatively connected to said initiator means and adapted to operate said valve means responsive to said control pulses, at least one and preferably both of said initiator means being mounted longitudinally displaceable in the direction of the piston stroke.
2. A stroke control device according to claim 1, wherein said initiator means are adapted to initiate an electric control pulse in response to a predetermined axial overlapping length of said transmitter and the respective initiator means.
3. A stroke control device according to claim 1, wherein said initiator means are operatively connected via an amplifying means to electromagnetic valve control means.
4. A stroke control device according to claim 1, wherein said initiator means are operatively connected with said electromagnetic valve control means via adjustable pulse storing means.