Abstract:
A solid waste material comminuting system having a  an electric motor for providing rotary motion, a pair of cutter stacks with cutter elements of one stack interleaved with cutter elements of the other, and gear means to transmit the rotary motion of the electric motor to counter-rotate cutter elements of one stack with cutter elements of the other. Each of the cutter stacks comprises a central shaft journaled for rotation and a seal-bearing assembly/module at each end of the central shafts. Each bearing  assembly/module comprises an end housing, and a pair of insertable pre-assembled seal-bearing elements/assemblies mountable in each of said end housings. One seal-bearing element/assembly has a thru-hole for journaling a first shaft for rotation and a second seal-bearing element/assembly has a thru-hole for journaling a second shaft for rotation.

Description:
This is a continuation of application Ser. No. 08/077,106 filed Jun. 16, 1993 now U.S. Pat. No. 5,354,004. 
    
    
     BACKGROUND OF INVENTION 
     This invention relates to a solid waste comminuting apparatus. Such devices have been established in the art and are now widely used in a variety of industrial applications, such as municipal waste treatment and industrial applications. Reference is made to U.S. Pat. No. 4,046,324, which discloses such a basic system that has achieved commercial success. 
     By definition, comminution is the reduction of particle size of solid waste material to minute particles. It is generally performed by shearing, shredding and crushing of the waste material. As set forth in the &#39;324 patent, comminution occurs by utilizing a pair of counter-rotating intermeshed cutting members. 
     The solid waste material is fed into the interface between cutting elements, typically utilizing a fluid carrier medium, and shearing action occurs because the two cutters overlap each other such that opposing forces of counter-rotation of the cutting elements on the different stacks act on the solid material as it passes through the device. 
     In practice, such devices are generally used in an enfluent path. That is, the solid material is generally entrained in a liquid and the device is placed directly in the liquid stream. By having the solid material entrained in a liquid stream transportation of the material to and from the unit occurs. Further, by softening the solid particles, a greater degree of comminution is achieved. Devices of the type disclosed in the &#39;324 patent have found commercial success and are widely used in waste treatment facilities, shipboard use and the like. As can be appreciated, the environment of use is very harsh for the equipment and as such, routine maintenance is required in both a preventative sense and also to immediately repair break downs when they occur thus minimizing system down-time. 
     An important aspect of such maintenance and repair is the integrity of the seals which provide the cutter stacks to rotate while minimizing friction. Given the mass of the cutter stacks together with high motor torque, loads on the seals are large and thus seal integrity is a primary consideration. In the past, two-shafted machines such as the &#39;324 device required that the seal assembly be an integral part of the device. Such is illustrated in  FIG. 1  of the &#39;324 patent. As a result, if there was a seal failure other critical components of the device were likely to be effected. This failure of a seal could thus mean that bearings could fail and seize up the cutter stack. 
     Importantly, to repair the seal assembly, in the prior art, there was a requirement that the device be disassembled and completely reassembled. In the context of a unit which is used in fluid waste treatment that down-time, in some cases as long as a day could have detrimental effects in the ability of a plant to process waste. Such would require rerouting solid waste, shutting down a portion of the facility and otherwise result in an inefficient operation. 
     Moreover, in prior art two-shafted machines, the cutter stack and the various seal components were integral and in-line with a fixed geometry. Consequently, tightening of the cutter stack, by compression, resulted in compression of the seals. Again, such is illustrated in  FIG. 1  of the &#39;324 patnet. It has been recognized however, that under normal operating conditions the cutter thickness experiences wear and thus the overall thickness of the stack tends to reduce over time. The result is an effective reduction in the overall stack height and the stack therefore tends to become loose. As a consequence, initial compression of various seal components is lost and the seal faces tend to separate. The result is leakage across the seal with the subsequent result of bearing failure. 
     Another deficiency in the prior art was the use of a labyrinth between the main fluid chamber and the seal faces. The labyrinth was generally incorporated into the seal components as sacrificial component. Because such devices are used in applications which include a high grit content, the labyrinth tended to be a relatively high wear component. As a consequence, seal components had to be removed to replace the labyrinth with the potential for seal damage upon reassembly. 
     SUMMARY OF THE INVENTION 
     Given these deficiencies in the prior art, it is an object of this invention to provide an improved solid waste comminutor that overcomes the operational and assembly problems of prior devices. 
     It is a further object of this invention to provide a solid waste comminutor which employs a cartridge with a balanced seal-bearing design to produce a constant seal face pressure. 
     A further object of this invention is to provide a solid waste comminutor of improved seal and bearing life by improved seal effectiveness which is independent of stack tightness. 
     Yet another object of this invention is to provide a seal cartridge for a solid waste comminutor which has an independent labyrinth that can be replaced without disassembly of the seal-bearing structure. 
     Another object of this invention is to provide an improved solid waste comminutor that utilizes a separate wear piece independent of the seal cartridge which itself may be pre-loaded to provide a spring force for the cutter stack. 
     These and other objects of this invention are achieved by a dual stack solid waste comminutor having preassembled bearing-sealed elements that are replaceable individually. That modular assembly improves system life while minimizing down-time. In accordance with this invention a cartridge type seal is employed utilizing two modular assemblies, one on each end of the cutter stack. Each of the modular bearing-seal assemblies comprises a pair of identical bearing-seal cartridges. Two identical bearing-seal cartridges are assembled into the end housing to thus form top and bottom modular pairs. 
     Further, in accordance with this invention the bearing-seal cartridges float within the housing to provide movement with shaft movement thereby reducing the stress on the shafts and bearings. 
     A quick exchange of the mechanical subassembly, which includes bearings, O-ring seals and cartridge housing itself can be effectuated. As a result of this modular assembly, an individual seal cartridge can be installed quickly without the need to disassemble the entire subassembly. 
     Another advantage of this technique is that the bearing-seal cartridge is identical for the top and bottom of the cutter stack. As a consequence, a deficiency in the prior art which used two different assemblies has been eliminated. The bearing-seal cartridge is an item which is pre-assembled and installed as received. Thus, there is no requirement that the individual items, the various races bearings and the like be assembled at the job site. Rather, the cartridge is interchangeable as a unit and is inserted into the end housing. 
     Further, in accordance with this invention by re-torquing of the cutter stack can be accomplished while the unit is still in-line and installed. It has been demonstrated that in practice, the most common preventative maintenance function is re-torquing the cutter stack to maintain stack compression for maximum cutting efficiency. 
     Prior to this invention a loss of stack compressibility lead directly to premature seal and bearing failure, primarily of the bottom seal assembly. In accordance with this invention, the tightness of the seal assembly is independent of total stack height, since it is designed as a self contained unit no disassembly is required. 
     Another advantage of this invention is an early warning seal failure detection system which can be used to prevent premature bearing failure. The invention provides for a drain port and/or weep holes in the shafts that allow fluid permeating from the seal to escape to the exterior. This can thus be viewed by maintenance personnel during routine checks of the system. 
     These and other objects of this invention will become apparent by a review of the attached drawing and the description of the preferred embodiment which follows. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         FIG. 1  is a cut-away side view of the overall comminution system of this invention; and 
         FIG. 2  is a schematic view illustrating the seal  cartridges and their assembly to form a dual seal cartridge . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to  FIG. 1 , a cut-away side view of the overall system is depicted. In  FIG. 1  the housing  1  has an inlet and outlet, not illustrated. At the bottom of the housing, a pair of access cut-outs  4  are provided to permit stack tightening, to be described herein, without disassembly of the device. The unit employs, three essential subsystems, which comprise a complete comminution apparatus  10 . These are a drive subsystem  11  with a motor  24  and speed reducer  12 , a gearing subsystem  14 , and a cutting subsystem  16 . The housing  26  for the speed reducer  12  is mounted to the gear and cutter system  14 ,  16  by a pair of conforming flange elements  18 ,  20 , which are clamped together by means of bolts  22 . The motor is typically an electric drive motor  24 , the details of which need not be discussed in detail. It will be recognized by those skilled that a suitable motor and drive system can be employed consistent with the scope of intended use. The speed reducer is contained in a housing  26  and employs an input shaft  30  and an output shaft  28 . The input shaft  30  is journaled for rotation using a coupling  32  to the motor  24 . This provides axial and radial alignment of the motor unit  24  with the speed reducer  12 . 
     The output shaft  28  of the speed reducer  12  passes through a transition piece  34  in which the output shaft  28  is keyed to a drive shaft  36  of one cutter stack by means of a coupling  35 . The drive shaft  36  carries a gear  38 . The drive shaft  37  of the other cutter stack carries a gear  40 . Both gears  38  and  40  are housed in housing  42  of the gear unit  14 . The two gears provide counter-rotation to a pair of cutter stacks  44 ,  46 . That is, shaft  36  is the drive shaft and shaft  37  is the driven shaft which counter-rotates due to gears  38 ,  40 . 
     Each of the cutter stacks  44 ,  46  comprises an alternating sequence of cutting elements  48  and spacers  50 . As illustrated in  FIG. 1 , the interface is such that by beginning the stack  44  with a cutter element and stack  46  with a spacer element the cutter elements interleave with each other in the area between the two cutter stacks, which has been denoted by numeral  52 . It is this interactive pair of stacks in zone  52  which provides the shredding of material as it passes through the cutter elements. 
     The cutter elements themselves may be either the same on each stack or differ from stack to stack. For example, it has been found that having eleven teeth on one cutter element and five on the opposing element improves the clean-out efficiency of the unit. Moreover, the geometry of the cutter elements may also be different in addition to the variations in the number of teeth. 
     As illustrated in  FIG. 1 , the cutter stack  16  is supported top and bottom by means of a pair of bearing-seal assemblies/modules  54 ,  56 .  FIG. 2  illustrated in greater detail those two subassemblies. 
     Referring now to  FIG. 2 , the assemblies/modules  54  and  56  are explained in greater detail. It will be understood from reference to  FIG. 1  that the assembly on top  54  is the same as the assembly on the bottom  56 , the unit simply being inverted.  FIG. 2  illustrates the seal bearing assembly  56 . The units are assembled into respective end housings,  58  and  60 .  FIG. 2  illustrates the end housing  60 . As illustrated, two identical bearing-seal cartridges are employed in the end housing.  FIG. 2  illustrates on seal  one element/assembly  62  in place with a second seal  element/assembly  64  being inserted into the end housing  60 . 
     Illustrated in phantom line in  FIG. 2  are the ends  66 ,  68  of the shafts  36  and  37  for the respective cutter assemblies  44  and  46 . It will be understood that the shaft ends  66  and  68  protrude through the respective seal cartridges but are held in place by end nuts  69 . Stack tightness is achieved by tightening the end nuts  69 . Access is via the cut-outs  4  so that an individual stack may be tightened. O-rings  70 , and  72  are employed to provide a fluid tight seal for each shaft. 
     As illustrated in  FIG. 2 , the bearing-seal cartridge comprises a cartridge housing  74  with an outer flange  76  and an inner tubular portion  78 . A spring  80  is inserted between the flange portion  76  and the cylindrical portion  78 . A dynamic race  82  sealed by means of an O-ring  84  is placed relative to the spring  80  and the cylindrical portion  78 . This spring provides a means by which the race  82  is provided with float. 
     A static race  86  with an O-ring  84  forms the dual race structure. The race is held in place by means of the bearing cartridge  88  having a flange element  91  to cage the static race into position and to also limit axial travel of the dynamic race. The dynamic race  82  has a face in contact with a confronting face of static race  86 . A bearing structure  90  is housed inside the bearing cartridge and is held in place by means of a retaining ring, such as a snap ring illustrated as element  92 . 
     A second spring  87  may optionally be used to allow the races  82  and  86  to axially float. The advantage is prevention of potential skew of the faces of the races relative to each other. 
     As illustrated in  FIG. 2 , the second seal cartridge  element/assembly has an identical construction of its elements. The units are held in place and are biased by means of springs  94 ,  96 . Those springs provide float for the bearing-seal cartridges  62 ,  64 ,  66  . 
     Sealing occurs by means of O-rings  98 ,  100 . It will be appreciated that with respect to the seal  cartridge illustrated in its installed position on the right hand side of  FIG. 2  the same elements are present. They have been denoted with prime numbers to connote the same numbering sequence. 
     While not illustrated, it is apparent from  FIG. 1  that the upper end housing, inverted having a pair of identical seal  cartridges is employed. The upper end seal-bearing module may be provided with an upper spacer  103 . This spacer rests on the outer race to preload the top bearing stack as the housing  42  is mounted on the housing  58  via bolts  104 . 
     Importantly, in accordance with this invention the labyrinth illustrated by dotted lines with numeral  102  is not a part of the seal- bearing  assembly. Rather, the labyrinth is considered to be a part of the stack assembly and is separated from the seal  cartridge assembly  itself. The labyrinth  102  protrudes to the enfluent  effluent stream where it is subjected to particles and the like while the device is in operation. Hence, it is a component that wears and must, from time to time be replaced. In accordance with this invention, the labyrinth  102  can be replaced as a single component since it is merely placed into the annular groove  108  of the housing  60 . It is compressed into position by a force applied through annular raised surface  110  that loads the labyrinth on surface  111 , and causes it to slightly deflect. This deflection serves to compensate for wear in the cutter stack. 
     As is apparent from  FIGS. 1 and 2 , this construction offers a number of important advantages. First, given the fact that the seal-bearing-seal  assemblies are a  include modular cartridge assembly  cartridges, repair of a seal assembly  requires only that a pre-assembled cartridge  64  be installed in place of the defective unit. Thus, the seal and bearing components and the bearing elements  are combined into a single cartridge assembly   64 . This allows for important advantages over the prior art in that the individual components do not have to be disassembled at a job site. 
     Secondly, by this invention stack tightening occurs independent of compression forces on the seal components. This occurs because, in accordance with this invention, the cartridges themselves are positioned and loaded independent of the cutter stack. That is the housing  58  is attached to gear housing  42  by means of the bolts  104 . Tightening the cutter stacks by means of the nuts  69  does not increase the forces on the bearings or seals. Rather, the force is a function of the spring force of the spring  80 . 
     In the case of the upper assembly, axial positioning is obtained by the spacer  103  which opposed by spring  94  as the unit is bolted by means of bolts  104 . The bottom assembly is allowed to float. The bottom assembly is mounted by means the mounting bolts  106 . The use of a spacer is eliminated. It is understood that the cover plates and mounting structure of the housing  1  have been eliminated. 
     This invention also includes a provision of leak detection by means of a leak detection plug  108 . Thus, an upper seal failure can be ascertained by fluid in the upper housing via the leak detection plug  108 . If there is any water in the warea, it will alert personnel that there is a potential failure in the upper bearing-seal. 
     Additionally, a leakage path can be provided in each of the shafts  36 ,  37 . To the extent that fluid permeates the seal it will thus escape to the exterior where it can be viewed during routine maintenance checks. 
     As set forth in this invention, in accordance with this invention a cartridge type bearing-seal  64  allows for replacement of units on an individual basis as opposed to replacement of the entire seal pair at the top or bottom of the cutter stack. Additionally, the entire assembly with the bearings intact can be removed from the housing for servicing. Given the construction of those cartridge elements tightening of the cutter stack can be accomplished without impairing the effectiveness of the seal. That is, compression of the seal components themselves occurs during the assembly of each of the seals cartridge units illustrated in FIG.  2 . Thus, the integrity of those units is accomplished independent of the tightness of the cutter stack. 
     Moreover, as illustrated in  FIGS. 1 and 2  the labyrinth  102  is placed between the main fluid chamber and either of the seal faces. In this invention the labyrinth  102  is distinct and separate from each of the seal cartridges. To the extent that the labyrinth requires replacement, it can be done by removing the cartridge, inserting a new labyrinth and then reinstallation of the cartridge  56 ,  60  without any disassembly of the seal components. 
     It will be apparent to those of skill in this technology that modifications of this invention can be made without departing from the essential scope thereof.