Abstract:
The invention relates to a centrifuge and to a method for operating the centrifuge. The centrifuge comprises a centrifugal drum, an inflow tube leading into the centrifugal drum for feeding a centrifugal material into the centrifugal drum, and a valve mechanism, which can be acted upon by control fluid, for cooling the centrifugal drum. The control fluid is cooled such that it acts as a cooling medium.

Description:
BACKGROUND AND SUMMARY OF THE INVENTION 
     The invention relates to a centrifuge comprising a centrifugal drum, an inflow tube leading into the centrifugal drum for feeding a centrifugal material into the centrifugal drum, and a device for cooling the centrifugal drum. The invention also relates to a method for operating a centrifuge according to the invention. 
     A centrifuge-of the above-mentioned type is known from German Patent Document DE OS 26 31 110. This document shows a centrifuge with a cylindrical solid-wall centrifugal drum whose shell can be continuously cooled by an insert arranged in the solid-material space by a circulating cooling medium. The insert is supported at several points in the drum shell and is guided in a sealing manner with respect to the separation space of the drum. 
     Although this cooling system is operable, a, problem arises with respect to the constructive expenditures required for achieving a cooling of the centrifugal drum. The expenditures excessively increase the costs for the manufacturing of the centrifuge particularly at lower cooling requirements. 
     German Patent Document DE PS 24 23 319 shows a centrifuge with a cylindrical solid-wall centrifugal drum whose shell can be continuously cooled by a circulating first cooling medium. The cooling medium leaves the drum shell at a radially exterior point and is thrown against a shell which is fixed to the frame and surrounds the drum. The shell fixed to the frame, in turn, can be additionally continuously cooled by a second cooling medium. This cooling system has also been successful but also excessively increases the costs for the manufacturing of the centrifuge in the case of lower cooling requirements. 
     Based on this state of the art, the invention aims at providing a centrifuge and a method for operating the centrifuge by means of which a cooling of the centrifuge can be implemented at low constructive expenditures. 
     In particular, the cooling should also be usable in the case of centrifuges with an automatic valve mechanism. 
     The invention achieves this goal. Accordingly, the cooling device includes and uses an outlet valve mechanism of the centrifugal drum which can be operated by a control fluid. The control fluid is cooled such that it acts as a cooling medium. The invention therefore surprisingly uses the valve mechanism of the centrifugal drum also as a cooling device. A separate cooling device is no longer required. 
     A cooling effect can particularly advantageously be achieved in that cooled sterile air is used as a control fluid. The cooling device, which includes control fluid connections, control fluid paths, an outlet valve mechanism and bores or passages, enables cooled control fluid to pass through the valve mechanism to cool the drum and its collected contents. During the centrifuging operation of the centrifuge, the valve mechanism is acted upon by a first sterile-air flow-through rate and, during an opening of a piston slide valve or control valve mechanism, is acted upon by a second sterile-air flow-through rate which is larger than the first flow-through rate. The first flow-through rate achieves a first cooling effect but does not yet displace the piston slide valve. On the contrary, this displacing is not implemented before the second flow-through rate. 
     Particularly preferably, sterile air is used as the control fluid because it is reasonable in price and can be handled in a particularly uncomplicated manner. As an alternative, other gaseous media can also be selected. 
     From German Patent Document DE 28 22 478, a centrifuge is known which comprises a centrifugal drum which has a piston slide valve to which a closing chamber is assigned which, by way of ducts in a spindle, is connected with a hydraulic system. The inflow of the product takes place from above by a central inflow tube. The spindle is situated on the underside of the centrifugal drum. This construction has been successful but reaches its limit when, for reasons of hygiene, the product range is to be situated separately from the driving range of the centrifuge and the control elements of the drive as well as the control elements of the control fluid supply outside the drum (valves, etc.). 
     This is the start of a further idea of the invention of assigning the feeding duct for the control fluid directly to the inflow tube for the centrifugal material. Because the control fluid feed line and the centrifugal material feed line are thus jointly guided into the centrifugal drum and preferably also extend directly side-by-side, a constructively separate feeding of the control fluid can be avoided. 
     The invention is particularly suitable for a centrifuge, in the case of which the centrifugal drum hangs on a centrifuge frame, the inflow tube for the centrifugal material and the feeding duct for the control fluid extending jointly from above into the centrifugal drum. In the case of centrifuges with hanging centrifugal drums, a separate feeding of the control fluid from below into the drum is not practical because it may be necessary to collect the solids separated during the separation process below the drum in a sterile vessel. This is clearly simplified by feeding the control liquid “from above”. 
     According to a particularly preferred embodiment of the invention, a double wall is constructed on the inflow tube. The interior tube, for example, is used for feeding the centrifugal material and the conically exterior tube section is used as a feeding device for the control fluid. A double-walled tube is particularly space-saving. In addition, the interior inflow tube for the centrifugal material is cooled in the simplest manner by the fluid in the exterior tube section. Another advantage of this solution is the fact that a separate control air feeding device in the manner of a spindle is avoided. 
     Preferably, the control air supply also has the purpose of actuating a displaceable piston slide valve for opening and closing solid-matter removal openings in the centrifugal drum. In this case, an opening chamber and a closing chamber adjoin the piston slide valve. By the pressurization by the control fluid, the piston slide valve is moved, in which case it is also possible to hold the piston slide valve in a spring-tensioned manner in one of its working positions and to move it into the respective other working position by the pressure buildup in the corresponding control chamber. 
     Particularly preferably, according to another variant of the invention, the control and cooling medium is guided through an outlet opening in the drum wall into a solid-matter collecting container in order to cool the collected solids as well as preferably also the rotating drum itself, on which frictional heat is generated by the rotation of the drum. In this case, the control pressure can be selected such that the corresponding working position is maintained despite the “leakage” through the outlet opening. 
     The opening in the drum wall can also be used for draining a cleaning medium guided into the control fluid paths of the centrifuge. 
     Summarizing, the invention also implements a space-saving automatic valve mechanism which can also be used for the cooling. 
     Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The FIGURE is a sectional view of a centrifuge according to the invention having a piston slide valve which, in the left section of the drawing, is illustrated in its opening position and, in the right section, in its closed position. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     It is noted that the terms used in the following, such as “on the bottom”, “on the top”, refer to a centrifuge in the case of which the inflow tube is essentially vertically aligned and the centrifugal drum hangs on the bottom on a centrifuge frame. However, these terms should by no means be interpreted to be limiting. 
     The Figure illustrates a centrifuge which is constructed as a separator and which, in a manner known per se, has a centrifugal drum  2  (which is only outlined and is attached toward the bottom) for the separation of a centrifugal material into various components. The centrifugal material or the centrifugal liquid is guided from above in the downward direction through a central inflow tube  4  into the centrifugal drum  2 . 
     The centrifugal drum  2  is suspended on a centrifuge frame  6  with a lower frame attachment  8 . The driving section  10  of the centrifuge (which is well known and therefore is not illustrated in detail) is arranged above the centrifugal drum  2  and/or on the centrifuge frame  6  and is sealed by a sealing section  12  (which is also not shown in detail) in the frame attachment  8  against the centrifugal drum  2 . The centrifugal drum  2  is therefore clearly separated constructionally from its driving section  10  and its control elements. 
     A container lid  14  is mounted on a flange on the lower end of the frame attachment  8 . The container lid  14  is penetrated in the center by the inflow tube  4 . The container lid  14  has an essentially radially constructed bore  16  which is used as a draining duct for a liquid phase from the centrifugal drum  2  which is diverted by a separating disk  18  from a separating chamber  20 . The bore  16  leads into a drainage tube  22 . 
     An upper container shell  24  surrounds the centrifugal drum  2  in its upper area and is used as an upper end of a conical container  26  for receiving solids. The shell  24  is molded to the container lid  14 , and a lower section  28  of the container  26  can be removed in the downward direction from the centrifuge and stands in a container frame  30 . 
     The actual centrifugal drum  2  has a distributor  32  which surrounds the inflow tube  4 —which in practice is preferably implemented in several parts and is illustrated here in a simplified manner in one piece. The distributor  32  has a plate package  34  attached on the outside on the distributor  32 . The plate package  34  is situated in a centrifugal space  36  which conically narrows toward the top and toward the bottom and which is bounded toward the top by a conically shaped drum lid  38  and toward the bottom by a conically extending centrifugal space bottom  40  molded at the bottom to the distributor  32 . The drum lid  38  is inserted into a drum bottom part  42  and is screwed together with a closing ring  44  in the drum bottom part  42 . 
     Between the centrifugal space bottom  40  and the lower housing wall of the drum bottom part  42 , a displaceably guided, ring-shaped piston slide valve or outlet valve mechanism  46  is arranged. The piston slide valve  46  has an essentially L-shaped wall cross-section which is adjoined in the upward direction by an opening chamber  48  and in the downward direction by a closing chamber  50 . The lower wall of the drum bottom part  42  is used as a lower closing chamber bottom  52 . Between the lower wall of the piston slide valve  46  and the closing chamber bottom  52 —thus, in the closing chamber  50 -, closing springs  54  are arranged. The closing springs  54  hold the piston slide valve  46  in its closed position in which it closes off the solid-matter outlet openings  56  in the outer shell of the bottom part  42  of the drum (right part of the Figure). 
     The opening chamber  48  is constructed between the piston slide valve  46  and the lower wall of the distributor  32  and the centrifugal space bottom  40 . The control fluid supply into the opening chamber  48  is by a control fluid feed line  58  in the distributor  32 . 
     The control fluid feed line  58  leads into a ring-shaped feeding duct  60 , which surrounds the inflow tube  4 , between the interior wall of the distributor  32  and the inflow tube  4  inserted into the distributor  32 . In this case, the interior wall of the distributor  32  and the wall of the inflow tube  4  form a type of “tube with a double wall”. The actual feeding duct  60  for the control fluid concentrically surrounds the inflow tube  4  for the centrifugal material. 
     Above the upper end area of the centrifuge frame  6 , an axial connection  62  permits the feeding of the centrifugal material into the inflow tube  4 . A control fluid feed line connection  64  is used for feeding the control fluid—particularly the feeding of sterile control air—into the feeding duct  60  surrounding the inflow tube. 
     The operation of the centrifuge of the Figure takes place as follows: 
     The feeding of the centrifugal material takes place through the connection  62  and the inflow tube  4  as well as through the axial bore  66  of the distributor  32  and a bore  68 , which extends essentially radially here, in the centrifugal space bottom into the centrifugal space  36 . Solids are removed from the centrifugal space  36  through the openings  56 ; liquid phases are removed through the separating chamber  20  with the separating disk  18 . 
     Control air (or another gas) is guided as a control fluid through the connection  64  into the feeding duct  60  concentrically surrounding the inflow tube  4 . From there, the control air flows into the control fluid feed line  58  and from there into the opening chamber  48 . As a result, in the case of a corresponding large pressure buildup in the opening chamber  48 , the piston slide valve  46  is pressed against the spring force of the closing springs  54  in the downward direction, which opens up the solid-matter outlet openings  56  (left section of the FIGURE). In contrast, a lowering of the pressure in the opening chamber  48 , because of the spring force of the closing springs, results in a displacement of the piston slide valve  46  in the upward direction, which closes the solid-matter outlet openings  56  again. 
     The piston slide valve  46  and the exterior wall of the centrifugal drum  2  have through bores  70 ,  72 , which interact with one another in one of the working positions of the piston slide valve  46  and can be closed off by a stopper  74 . After the removal of the stopper, a simple possibility is created for cleaning the control fluid paths or ducts ( 60 ,  58 ,  48 ) as well as other centrifuge elements, for example, by means of a rinsing liquid or a rinsing gas, for example, for a particularly uncomplicated implementation of a CP (cleaning-inplace) operation. The bores  70 ,  72  may also have a nozzle-type design such that, as a result of the outflow of the cooled control fluid into the container  26 , a cooling of the collected solids as well as of the drum  2  takes place. 
     The cooling effect is achieved in that cooled sterile air is used as the control fluid. The cooling device, which includes the connection  64 , the control fluid paths  60 ,  58 ,  48 , the piston slide valve or outlet valve mechanism  46  and the bores or passages  70 ,  72  enables the cooled control fluid to pass through the valve mechanism to cool drum  2  and its collected contents. During the centrifuging operation, the cooled control fluid is fed in through connection  64 , into duct  60  and then into the ducts or controlled fluid paths  58 ,  60 ,  48  which are acted upon by a first sterile-air flow-through rate. This first flow-through rate achieves a cooling effect, but does not yet displace the piston slide valve  46 . On the contrary, this displacement is only implemented by means of a clearly higher second flow-through rate, which opens the valve  46  and permits the fluid flow through bores  70 ,  72 . 
     Although the present invention has been described and illustrated in detail, it is to be clearly understood that the same is by way of illustration and example only, and is not to be taken by way of limitation. The spirit and scope of the present invention are to be limited only by the terms of the appended claims.