Canted, spring-loaded feed screw support

A feed screw housing support includes a support pedestal (46), a spring loaded tie rod assembly (76), and a bearing assembly including pedestal bearing blocks (62) cooperating with mating bearing blocks (66) connected directly or indirectly to the housing. The tie rod assembly provides a resilient hold down force between the housing (32) and the pedestal (46). The interfacing surfaces (74) of the blocks are angled in such a manner that, when viewed from the ends, a line extending from each planar interface of the blocks passes directly through the axis (54) of the feed screw rotor (28).

BACKGROUND OF THE INVENTION 
The present invention relates generally to disc type attrition mills and 
more particularly to a disc type refiner having a refiner casing and an 
attached feed screw housing. 
Disc refiners of this type are widely used in paper pulp processing and are 
characterized by a rotor supporting a concentric disc. A set of refining 
plates is mounted on one or both axial faces of the disc. The refining 
plates are available in a variety of patterns and plate faces typically 
are in a ribbed or toothed pattern. A stationary set of refiner plates is 
disposed in juxtaposed relation to the plates of the disc on the rotor, 
and the material to be refined is introduced near the rotor axis between 
the opposing plate surfaces. The relative rotation of the plates 
centrifugally advances the material radially across the plate surfaces and 
the relatively close spacing of the plates breaks down the material 
fibers. In a common embodiment of such disc type refiner, a screw or 
ribbon feeder is associated with the rotor, and extends in a housing which 
is rigidly connected to the refiner casing. Typically, another screw 
arrangement is connected to the feed screw housing to supply raw material 
from a storage bin. 
The spacing between the rotating, or rotating and stationary plates, is 
typically in the range of 0.04 to 0.10 inches during the refining 
operation. A recurring problem with refiner of this type, is that external 
loads developed by thermal expansion of connecting pieces and pressure 
forces developed by flexible expansion joints associated with the housing 
and casing, have not been well isolated from the refiner casing. If such 
external loads on the feed screw housing are not isolated from the refiner 
casing, they can adversely effect the operation of the refiner by causing 
distortion of the refining surfaces and causing the refiner to go out of 
tram, i.e., base parallelism of the refining plates. 
Conventional techniques for accommodating these external loads do not fully 
compensate for all directions of thermal expansion and externally applied 
piping loads. A typical prior art arrangement is shown in U.S. Pat. No. 
3,847,359 (Holmes et al), "Disc Type Refiner With Automatic Plate Spacing 
Control", which discloses a rotor mounted in a bearing set, which in turn 
is mounted in a member that is slidably disposed within the housing to 
permit axial displacement of the bearing without changing the position of 
the rotor with respect to the base of the refiner. Although this 
arrangement can accommodate horizontal stresses, it can not readily 
accommodate vertical stresses. 
U.S. Pat. No. 4,688,732 (Jackson), "Refiner With Improved Bearing Retainer 
Construction", also disclosed a bearing assembly which can accommodate 
displacement between a rotor and its enclosure, but, as with the 
previously mentioned patent, only in the axial, i.e., horizontal, 
direction. 
SUMMARY OF THE INVENTION 
It is thus an object of the present invention to provide support for a 
refiner feed screw, which will allow for expansion of the feed screw 
housing in all directions, and isolate a connected refiner both 
horizontally and vertically from external thermal expansion and piping 
loads applied to the feed screw housing. 
It is a further object to provide such a support in a manner whereby the 
inlet feed conveyor can be positioned on either side or the top of the 
feed screw housing. This allows complete flexibility for equipment 
installations. 
In accordance with the invention, the feed screw support includes a support 
pedestal, a spring loaded tie rod assembly, and a bearing assembly 
including pedestal bearing blocks cooperating with mating bearing blocks 
connected directly or indirectly to the housing. The tie rod assembly 
provides a resilient hold down force between the housing and the pedestal. 
The interfacing surfaces of the blocks are angled in such a manner that, 
when viewed from the ends, a line extending from each planar interface of 
the blocks passes directly through the axis of the feed screw rotor. This 
positioning of the sliding bearing surfaces allows the screw housing to 
move or expand axially and radially, due to thermal and pressure expansion 
of the housing, without displacing the center line of the feed screw. An 
important feature of the present invention is that by having a line 
projecting from the sliding bearing interface directly through the feed 
screw center line, any amount of radial expansion of the screw housing can 
take place without distorting the feed screw center. 
Without the sliding surfaces oriented in this angled arrangement, the 
slides would have to be positioned directly on the horizontal center line 
of the feed screw housing to compensate for any expansion from the feed 
screw horizontal center line to the base or bottom of the feed screw 
housing. If the slides were thus positioned on the horizontal center line, 
as has been the conventional practice, then a side inlet screw or ribbon 
feeder could not be economically built and still compensate for all 
expansion of the screw housing.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 shows a typical disc refiner system 10 used in the paper pulp 
processing industries and the like. In such systems, a refiner casing 12 
encloses a rotating disc 14, to which may be fitted specially patterned 
disc plates 15, which are maintained in spaced relation from an adjacent 
set of annularly disposed, stationary plates 16. The material to be 
refined is introduced near the axis of the rotating disc between the 
opposing plate surfaces, as at 18. The relative rotation of the plates 
centrifugally advances the material radially across the plate surfaces and 
the relatively close spacing of the plates breaks down the material 
fibers. The processed fibers are then extracted through a conduit 22 
located at the circumference of the casing 12. The rotating disc 14 
concentrically extends from the disc rotor 25, which is supported within a 
refiner bearing assembly 26 by roller bearings 27 and thrust bearing 30. 
Typically, the casing 12 is rigidly connected to the refiner base 31 and 
the bearing assembly 26 is supported by the refiner base on pads 33 that 
enable the bearing assembly to slide axially for the purpose of adjusting 
the plate separation. The overall arrangement of the refiner is 
exemplified by U.S. Pat. No. 4,725,336 (Fisher) "Refiner Apparatus With 
Integral Steam Separators", the disclosure of which is hereby incorporated 
by reference. 
In the illustrated refiner system, a pulp feeder rotor 28 penetrates the 
casing and is centrally disposed within an elongated, substantially 
cylindrical feeder housing 32 coaxially extending opposite the refiner 
rotor 25. The housing is bolted to the casing through flange connection 
52. At its end 34 opposite the disc 14, the rotor 28 is supported in a 
bearing assembly 36 that is connected to housing 32, and is rotated by 
means of a drive motor assembly shown generally at 38, the drive assembly 
including a motor, gearing, and the like, which, for purposes of the 
present invention, is conventional. The other end 40 of rotor 28 is 
cantilevered in the housing 32 to a position substantially adjacent to the 
center of the rotating disc 14 in the casing 12. The rotor 28 has 
connected thereto, a pattern of ribbon screw projections 42 for conveying 
pulp to the center of the rotating disc 14 in the casing. An infeed stock 
conveyor 44 is connected to the housing 32 to supply feed pulp to the 
ribbon feed screw 42. A pedestal 46 is secured to floor 24 to support the 
weight of the housing 32, rotor 28, bearing assembly 36, and motor 
assembly 38. Thus, in the illustrated embodiment, the weight of the 
refiner casing 12 is suspended between the feeder support pedestal 46 and 
the refiner base assembly 31. 
Those familiar with this technology can appreciate that a major objective 
assuring safe and trouble free operation of the system is the maintenance 
of the desired spacing 48 between the plates 15 on rotating disc 14, and 
the stationary plates 16. At least two operating conditions can adversely 
affect spacing. First, the differential expansion of the housing 32 
relative to the casing 12, due to differences in operating temperature and 
pressure, can impose stresses on the casing through the rigid connection 
52, that can affect the spacing. Secondly, stresses can arise from a 
variety of loads originating with the piping and other connections to the 
refiner system, e.g., from the infeed stock conveyor 44, the refiner 
discharge conduit 22, and from various lines which are fluidly connected 
to the system for various purposes known to those skilled in this art. 
In accordance with the present invention the feed housing pedestal 46 is 
designed to permit relative horizontal (axial) movement of the housing 32 
with respect to the casing 12. Differential stresses or loads on the 
housing and casing, are substantially accommodated by the pedestal and 
thus minimize the differential effect of the loads on the spacing between 
the rotating disc plates 15 and the stationary plates 16 in the refiner 
casing 12. 
FIGS. 2 and 3 illustrate the preferred embodiment of the invention. The 
pedestal 46 for the housing 32 is centrally positioned, substantially 
vertically below the rotor axis 54, and preferably has a shape resembling 
the letter "M" when viewed in section. Thus, the left and right side walls 
56, 58 as shown in FIG. 2, are preferably angled at about 30.degree. from 
the vertical. Near the upper portion of the side walls, are attached a 
respective pair of pedestal blocks 62a, 62b, each having a flat, planar 
surface which, if extended upwardly, would intersect and form an 
intersection line, substantially coincident with the rotor axis 54. The 
pedestal blocks 62a, 62b are preferably removably secured by means of 
bolts 64 or the like to the pedestal side walls, to facilitate replacement 
or refinishing of the planar surfaces. A second pair of blocks 66a, 66b, 
having flat, planar surfaces which are substantially coextensive with the 
first planar surfaces, are oriented downwardly and rigidly secured 
directly or indirectly to the housing 32, for transferring all of the 
weight associated with the housing 32 to the pedestal, through the 
pedestal blocks 62. The housing blocks 66 are preferably detachably 
connected, as by bolts 68, to a housing bracket 72, which is in turn 
secured to the housing. 
The mating surfaces 74 of the pedestal and housing blocks are preferably 
made of material which is rigid, yet permits a relative sliding between 
the surfaces, despite the considerable weight transmitted therethrough. It 
has been found that the preferred included angle of the sliding interfaces 
between the left and right pair of blocks 62a, 66a, and 62b, 66b, spans 
60.degree. and is vertically centered on the rotor axis. The choice of 
materials for the block contacting surfaces, and the vertical and 
horizontal dimensions of the contacting surfaces, can be optimized by the 
practitioner in accordance with the diameter of the feed housing 32, the 
available clearance between the feed housing and the floor 24, and the 
weight to be supported. For example, the interfacing surfaces could be of 
the type described in U.S. Pat. No. 4,688,732, mentioned above, wherein 
one surface is made of chrome plated steel, while the other surface would 
be produced of steel having a teflon coating. Other options include glass 
reinforced teflon material with steel backing, or simply greased metal 
plates. 
It should be appreciated that the support arrangement provided by these 
blocks permits horizontal movement of the housing 32 relative to the 
pedestal 46. Furthermore, as the housing may expand or contract, the 
dimensional change influences the effective radius of the housing, which 
is accommodated by the sliding of the blocks in a direction radially 
toward or away from the rotor axis 54. Ideally the housing 32 expands 
radially at the same rate as the casing 12. 
As an additional feature of the present invention, two spring loaded tie 
rod assemblies 76a, 76b are positioned in the center of the pedestal 46, 
spaced apart vertically below the rotor axis 54. One end 78 of each rod is 
attached to the bottom of the housing, or the bracket 72, by a clevis 
joint 82, and the other end 84 extends vertically through the pedestal and 
is attached thereto to produce a resilient, tensioned force tending to 
maintain the housing blocks 66 in contact with the pedestal blocks 62. In 
the illustrated embodiment, the pedestal 46 has two vertically oriented 
chambers 86a, 86b through which the intermediate portions 88a, 88b of the 
tie rods pass, respectively. The lower end 92 of each chamber includes a 
spring seat 94 which cooperates with a washer 96 and nut 98 arrangement 
outside the chamber, for maintaining a coil spring 102 in compression to 
provide the tension bias on the tie rod 76. 
The tension force supplied to the tie rods resists any moment loading 
caused by any expansion forces applied to the side inlet conveyor nozzle 
44 (the opening of which is shown at 104), or any other side forces 
applied to the feed screw housing 32 which would have a tendency to rotate 
the housing 32 about the bearing pedestal blocks 62a, 62b. The tie rod 
assemblies 76a, 76b also resist any moment loading produced by frictional 
resistance of the sliding blocks 62, 66 as the screw housing 62 moves 
axially.