US3753351A - Energy regaining apparatus and method for accelerating and decelerating centrifuges - Google Patents

Energy regaining apparatus and method for accelerating and decelerating centrifuges Download PDF

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Publication number
US3753351A
US3753351A US00229093A US3753351DA US3753351A US 3753351 A US3753351 A US 3753351A US 00229093 A US00229093 A US 00229093A US 3753351D A US3753351D A US 3753351DA US 3753351 A US3753351 A US 3753351A
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Prior art keywords
pump
centrifuge
energy
motor
pumps
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US00229093A
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English (en)
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K Pause
W Steprath
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BWS Technologie GmbH
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Maschinenfabrik Buckau R Wolf AG
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B04—CENTRIFUGAL APPARATUS OR MACHINES FOR CARRYING-OUT PHYSICAL OR CHEMICAL PROCESSES
    • B04B—CENTRIFUGES
    • B04B9/00—Drives specially designed for centrifuges; Arrangement or disposition of transmission gearing; Suspending or balancing rotary bowls
    • B04B9/06—Fluid drive

Definitions

  • centrifuges In modern sugar factories it is the rule to provide several centrifuges for the treating of one product. Each centrifuge is individually driven by an electric motor. Centrifuges, particularly when used for separating sugar crystal and syrup, operate periodically, which means that they fill and empty at low rotary speed, but are accelerated to a high rotary speed, for example about 1,450 revolutions per minute for the purpose of separating, washing and drying the sugar mass, whereupon they are again decelerated to the filling and discharging speed of 60 revolutions per minute.
  • Modern large centrifuges have moments of inertia of 2,000 kg m or even greater, which are produced by the mass of the centrifuge drum and by the mass of sugar in the ratio of l l. Acceleration time from the discharge and filling speed to the maximum speed is about 60 seconds, so that the electric motor must have a power of over 100 kW.
  • Induction motors with squirrel rotors havebeen used for a long time, and since in standard induction motors, the rotor losses, disregarding bearing friction, air friction and stator losses, practically correspond to the energy which is stored in the centrifuge at a maximum speed, with corresponding high temperatures of the motor, already years ago special squin'elrotor motors were developed for driving centrifuges.
  • the new special motor can return 0.1 17 kW h to the power supply when braked and acting as a generator.
  • Each motor in a centrifuge station has to provide lost energy for the following purposes:
  • Another object of the invention is to mechanically utilize the kinetic energy released upon deceleration of a discontinuously operating centrifuge.
  • Another object of the invention is to provide a drive for accelerated and decelerated centrifuges in which the disadvantages of electric braking by using the drive motor as generator, are avoided.
  • every centrifuge of a set of centrifuges is individually driven by a hydraulic motor which is driven by a hydraulic pump, and all hydraulic pumps of the thus formed hydrostatic transmissions are mechanically coupled and connected for rotation and driven from a common motor, preferably an electro-motor, such as a slide ring or squirrel cage motor.
  • a common motor preferably an electro-motor, such as a slide ring or squirrel cage motor.
  • the arrangement according to the invention obtains the result that energy, released during deceleration of a discontinuously operating centrifuge is directly supplied to another centrifuge which is to be accelerated, while the electric drive motor varies its rotary speed only slightly, and within the thermally favorable and consequently economical range of the highest rotary speed. Due to the mechanical exchange of energy, the total efficiency of a station with several centrifuges is improved, and not only energy, but also initial investment cost are saved.
  • the method of the invention comprises accelerating and decelerating at least two centrifuges, or other rotary masses, by hydrostatic transmissions including hydraulic pumps driven by a common drive motor; and decelerating one centrifuge while the other centrifuge is accelerated so that the energy regained by deceleration of one centrifuge causes operation of the respective hydraulic pump as a hydraulic motor, reducing the load on the common drive motor during acceleration of the other centrifuge.
  • An embodiment of the invention comprises a set of hydrostatic transmissions, each including a hydraulic motor, and an adjustable pump driving the respective hydraulic motor, and having regulating means for varying the flow to the respective hydraulic motor; means mechanically connecting the drive means with the adjustable pumps for rotation together; and a set of centrifuges individually driven by the hydraulic motors, respectively, to accelerate and decelerate depending on the adjustment of the respective hydraulic pump by the regulating means.
  • the drive means preferably include an electric motor such as a-squirrel cage motor, a slip clutch and a flywheel.
  • the mechanical connection between the pumps of the hydrostatic trammissions may be obtained by a common shaft, or by a gear train.
  • This arrangement prevents a feeding back of electric energy to the electric drive motor and to its power supply.
  • the driving part of the slip clutch runs synchronously with the electric drive motor, while the driven part of the slip clutch runs at a different speed as compared with the electric drive motor.
  • the respective flywheel which is mechanically coupled for rotation with all hydraulic pumps, can, upon a variation of the rotary speed, store energy and release energy within the speed difference of the slip clutch. The mass inertia moment that the fly-wheel can store the remaining energy within the range of the differences in the rotary speed. This obtains the result that the load variations of the electric drive motor are so small that the motor has to produce only the energy required for the losses, while no feed back of electric energy to the power supply takes place.
  • the electric drive motor runs at almost constant rotary speed, and there is connected by the slip clutch, which may be a hydraulic, or magnetic slip clutch, with the input shaft of a distributor transmission which connects the pumps of all hydrostatic transmissions for synchronous rotation.
  • the slip clutch which may be a hydraulic, or magnetic slip clutch
  • Each pump is hydraulically connected with a hydraulic motor which drives a centrifuges, and the pumps are adjustable for acceleration or deceleration of the centrifuges at constant pressure, so that the variation of the pumped volume within a time unit, corresponds to the required variation of the rotary speed. Due to the fact that pumps of hydrostatic transmissions are mechanically interconnected for rotation, the regained and released energy of a braking centrifuge can be transmitted to a centrifuge which is to be accelerated.
  • the fly-wheel acting as a mechanical storage accumulates the available excess energy by increasing its rotary speed and then again provides energy, when more energy is required, by reducing its rotary speed. Since the fly-wheel is positively coupled for rotation with all pumps, variations of the rotary speed of the fly-wheel are transmitted to the pumps without modification. Due to the fact that the pumps are adjusted within the operational range of accelerations and decelerations to a constant pressure, corresponding to a constant output torque of the hydraulic motors, their energy supplies to the variations of the rotary speed are automatically corrected, In operational ranges with constant rotary speed, the variations of the rotary speed of the drive means are corrected by a variation of the pumped volume of the hydraulic pump.
  • the pumps of the hydraulic transmissions have regulating means operated by cylinder and piston means which are operated by pressure fluid supplied from an auxiliary pump in accordance with the position of an electromagnetically controlled valve.
  • the cylinder and piston means is provided with pressure limiting valves for acceleration and deceleration, and both pressure limiting valves are connected with the connecting conduits between the respective pump and hydraulic motor of a hydrostatic transmission, and respond to the pressure in the same.
  • FIG. 1 is a diagram illustrating the variation of the energy of the centrifuge over the acceleration and deceleration time
  • FIG. 2 is a diagram illustrating the energy exchange between four centrifuges in accordance with the invention.
  • FIG. 3 is a schematic view illustrating an embodiment of the invention.
  • FIG. 4 is a schematic view illustrating a modified embodiment of the invention.
  • FIG. 4 illustrates a modification of the apparatus, the fly wheel and the slip clutch being omitted for the sake of simplicity.
  • An electric motor is shown which has two coaxial output shafts 2 on opposite sides each of which drives a pair of adjustable pumps 22 which are parts of hydrostatic transmissions to 13 including hydraulic motors 24' having output shafts 14, 15, 16 and 17, respectively connected with centrifuges 18 to 21, as shown in FIG. 3.
  • the aligned shafts 2' provide a positive coupling and interconnection of the adjustable pumps 22 so that all pumps rotate at the same speed, which is equal to the speed of the shaft means 2'.
  • F IG. 5 illustrates a control device provided for each hydrostatic transmission 10 to 13, only one hydrostatic transmission including an adjustable pump 22 and a hydraulic motor 24 with an output shaft 14 being shown in FIG. 5. Corresponding control devices are provided for the other hydrostatic transmissions.
  • the centrifuge 18, which is connected to output shaft 14, the distributing means 5, the electric motor 1 and the slip clutch 3 and fly wheel 4 are not shown in FIG. 5.
  • the control device of FIG. 5 includes an auxiliary pump 23 which is connected with the shaft of the pump 22 and rotates with the same.
  • the discharge flow of the auxiliary pump 23, or other source of pressure fluid flows through a conduit 31 to a control valve 30 which is also connected to a conduit 30 sucking from an open container 32 with which also the inlet of the auxiliary pump 23 is connected.
  • shaft 6 is driven from the electric motor 1 the adjustable pump 22 and the auxiliary pump 23 are driven.
  • the fluid pumped by the adjustable pump 22 flows through connecting conduit 25 to the hydraulic motor 24 and through a conduit 26 back to the adjustable pump 22 of the hydrostatic transmission 10.
  • the fluid pumped by adjustable pump 22 drives the hydraulic motor 24, and thereby the respective centrifuge 18.
  • the pumped volume of adjustable pump 22 is regulated by a servo motor 27 including a piston 27a forming two chambers 27b and 27c in the cylinder of the servo motor 27, and being connected with the regulating means of the respective adjustable pump 22, as schematically indicated by a slanted arrow.
  • control valve 37 whose valve slide is connected to two electromagnetic means 33 and 34 for placing control valve 37 is three different positions, which are schematically shown in FIG. 5.
  • conduit 31 no fluid can flow from conduit 31 to conduit 28a, which is connected with chamber 27-so that the pump 22 is not adjusted by the'regulating means 27.
  • the pressure conduit 31 is connected to its conduit 29a so that the pressure fluid flows into the other chamber 270 and the piston 27a is moved to the right as viewed in FIG. 5, so that the pump 22 is adjusted in the opposite sense so that the speed of motor 24 is reduced, and the centrifuge 18 is decelerated.
  • pressure limiting valves 28 and 29 are provided which are also connected to the connecting conduits 25, 26, between pump 22 and hydraulic motor 24 and respond to the pressures in conduits 25 and 26.
  • Pressure limiting valve 28 measures the pressure in connecting conduit 25 and maintains the same constant so that the hydraulic motor 24 and the centrifuge 18 are accelerated at a constant torque. From program control means, not shown, a pulse signal deceleration arrives at electromagnet 34, control valve 30 assumes the position 36 so that the fluid from conduit 31 flows to the pressure limiting valve 29, and starts the deceleration. The inertia and energy stored in the mass of the centrifuge, drives the hydraulic motor 24 now as a pump so that fluid is pressed into pump 22, which starts operating as a hydraulic motor.
  • the torque of the pump 22 acting as hydraulic motor is transmitted to all other pumps by the positive mechanical connection 5 or 2', so that an other centrifuge, which is accelerated at this time, is also driven by the pump 22 acting as hydraulic motor, whereby the load on the electric motor 1 is reduced.
  • the rotary speed of the centrifuge is proportional to the piston stroke of piston 27a of the regulating means 27.
  • the acceleration of the centrifuge is proportional to the speed of movement of piston 27a, and to the amount of oil supplied thereto in the time unit.
  • the pressure regulating valve 29 regulates by means of the oil in the cylinder of regulating means 27, and in accordance with the speed of piston 27a, the pressures in connecting conduits 25 and 26.
  • the pressure acting on the hydraulic motor 24 is thus maintained constant during acceleration and deceleration which has the effect that the centrifuge is accelerated by a constant turning moment or torque, or decelerated, respectively.
  • the speed of the centrifuge is measured and monitored, and if required, corrected by control valve 30.
  • FIG. 1 illustrates the variation of the energy of a centrifuge 18 to 21 over the time required for acceleration i and again filled.
  • One charge and braking The graphs N on the right side of FIG. 1 indicates the effective energy required for acceleration of the mass of the centrifuge drum in-filled condition.
  • the graph N represents the energy losses due to air friction and bearing friction and the graph Np indicates the energy to be delivered by the pump 22 considering the hydraulic efficiency.
  • the left side of FIG. 1 shows graphs indicating a decelerating or braking. Since during deceleration the conditions are reversed, the losses have to be deducted from the energy stored in the centrifuge drum, and the energy return is consequently reduced.
  • FIG. 2 The basic conditions in the transformation of energy by a centrifuge as shown in FIG. 1, are illustrated in FIG. 2 for a group of four centrifuges 18 to 21, assuming 18 charges per hour, wherein each centrifuge operates 32 seconds at the highest speed, and then runs 60 revolutions per minute for 55 seconds until emptied takes 200 seconds, and the intervals between the beginning of charges are constant and 50 seconds.
  • the energy variations of the four centrifuges over the time are illustrated by four graphs a, b, c, d, the energy for acceleration being positively illustrated, and the energy for braking and decelerating being illustrated as negative.
  • the heavy graph e results from the addition of the values of the graphs a, b, c, d.
  • the areas fl and f2, hatched in the negative lower section of the diagram, represent regained energy which are used for increase of the rotary speed of the fly wheel, and reduce the load of the electric induction motor 1 whose squirrel cage rotor operates at a reduced speed, whereby automatically the energy and power peaks of motor 1 are reduced, since the rotor must first reach a slip speed which permits the motor to produce a torque corresponding to the required load.
  • the slip speed of rotation is only reached when the rotary of the fly wheel has been reduced, and the fly wheel has delivered kinetic energy.
  • Energy regaining apparatus for accelerating and decelerating centrifuges and other rotary masses, comprising drive means; a set of hydrostatic transmissions, each including a hydraulic motor, and an adjustable pump driving the respective hydraulic motor, and having regulating means for varying the flow to the respective hydraulic motor; distributing means mechanically connecting said drive means with said adjustable pumps for rotation together; and a set of centrifuges individually driven by said hydraulic motors, respectively, to accelerate and decelerate depending on the adjustment of the respective hydraulic pump by said regulating means so that energy, regained during deceleration of a centrifuge, causes the respective hydraulic motor to pump fluid to the respective pump so as to operate the same as a hydraulic motor supplying the regained energy to said distributing means and thereby to an other centrifuge which is being accelerated.
  • each of said pumps has a pump shaft; wherein said distributing means include a transmission connecting said pump shafts for rotation together, said transmission having an input shaft; wherein said drive means include a fly wheel on said input shaft, one drive motor driving said input shaft, and a slip clutch between said drive motor and said fly wheel.
  • said drive means include a drive motor having an axis; wherein said pumps have axes aligned with said axis; and wherein said distributor means include shaft means connecting said drive motor with said pumps and having an axis coinciding with said axes.
  • Apparatus as claimed in claim 5 wherein at least one pump is located on either side of said drive motor; and wherein said drive motor has two output shafts on opposite sides for driving said pumps.
  • Apparatus as claimed in claim 1 comprising a set of control devices respectively associated with said hydrostatic transmissions, each control device including a cylinder, and a piston in said cylinder connected with said regulating means for operating the latter, a source of pressure fluid, conduit means connecting said source with said cylinder, and control valve means in said con-. duit means operable for controlling the flow of fluid into said cylinder so that said piston and thereby said regulating means can be moved in opposite directions.
  • said piston forms two end chambers in said cylinder; wherein said source includes an auxiliary pump driven from said drive means by said distributing means; wherein said conduit means include a high pressure conduit and a low pressure conduit connecting said auxiliary pump with said chambers, respectively; and wherein said control valve means controls said conduits, and has first and third positions for reversing the pressure acting in said chambers, and an intermediate second position for holding said piston.

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US00229093A 1971-03-06 1972-02-24 Energy regaining apparatus and method for accelerating and decelerating centrifuges Expired - Lifetime US3753351A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE19712110736 DE2110736B1 (de) 1971-03-06 1971-03-06 Vorrichtung zum gemeinsamen antreiben mehrerer zentrifugen

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US (1) US3753351A (enExample)
AT (1) AT321226B (enExample)
CS (1) CS161146B2 (enExample)
DE (1) DE2110736B1 (enExample)
FR (1) FR2128308A1 (enExample)
IT (1) IT946155B (enExample)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3932992A (en) * 1973-11-21 1976-01-20 Poclain Pressurized fluid supply power control means
EP3280913A4 (en) * 2015-04-10 2018-06-06 Abbasszadeh, Mohammad Taghi Hydro-motors system with variable combination units
US20210178404A1 (en) * 2017-11-16 2021-06-17 Dynamic Extractions Limited Centrifuge Apparatus

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2465613A1 (de) * 2010-12-16 2012-06-20 Ferrum AG Zentrifugenanordnung, Verfahren zum Betreiben einer Zentrifugenanordnung, sowie Zentrifuge

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2846849A (en) * 1954-09-06 1958-08-12 Keelavite Co Ltd Apparatus for maintaining a predetermined relationship between the speeds of two independently driven members
US3279172A (en) * 1964-06-06 1966-10-18 Komatsu Mfg Co Ltd Hydraulic drive speed changing and transmitting unit

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2846849A (en) * 1954-09-06 1958-08-12 Keelavite Co Ltd Apparatus for maintaining a predetermined relationship between the speeds of two independently driven members
US3279172A (en) * 1964-06-06 1966-10-18 Komatsu Mfg Co Ltd Hydraulic drive speed changing and transmitting unit

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3932992A (en) * 1973-11-21 1976-01-20 Poclain Pressurized fluid supply power control means
EP3280913A4 (en) * 2015-04-10 2018-06-06 Abbasszadeh, Mohammad Taghi Hydro-motors system with variable combination units
US20210178404A1 (en) * 2017-11-16 2021-06-17 Dynamic Extractions Limited Centrifuge Apparatus
US11865552B2 (en) * 2017-11-16 2024-01-09 Dynamic Extractions Limited Centrifuge apparatus with flying leads

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Publication number Publication date
IT946155B (it) 1973-05-21
FR2128308A1 (enExample) 1972-10-20
AT321226B (de) 1975-03-25
CS161146B2 (enExample) 1975-05-04
DE2110736B1 (de) 1972-05-25

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