U.S. patent number 3,849,893 [Application Number 05/223,210] was granted by the patent office on 1974-11-26 for rotating machine wear gauging means and method.
This patent grant is currently assigned to Pioneer Centrifuging Company. Invention is credited to George S. Ormsby.
United States Patent |
3,849,893 |
Ormsby |
November 26, 1974 |
ROTATING MACHINE WEAR GAUGING MEANS AND METHOD
Abstract
The present invention relates to detection and measurement of
wear in machines having relatively rotating housings and parts such
as radially extending blades subject to wear which may exceed a
critical degree, and in particular to the measurement and
predetermination of wear and of conveyance capacity of a scroll
type conveyor. The invention includes the use of a measuring device
for measuring the distance between the radially outer edge of a
portion of the conveyor blade and a reference point in the housing
radially and longitudinally fixed with respect to the axis of the
conveyor. This measurement is preferably taken at a predetermined
first portion of the blade such that the measurement at said first
portion is indicative of the wear and/or conveyance capacity of one
or more other portions of the blade.
Inventors: |
Ormsby; George S. (Houston,
TX) |
Assignee: |
Pioneer Centrifuging Company
(Houston, TX)
|
Family
ID: |
22835537 |
Appl.
No.: |
05/223,210 |
Filed: |
February 4, 1972 |
Current U.S.
Class: |
73/7; 33/832;
415/118; 198/657 |
Current CPC
Class: |
B04B
1/20 (20130101); G01N 3/567 (20130101); G01B
5/14 (20130101) |
Current International
Class: |
G01B
5/14 (20060101); G01N 3/56 (20060101); G01b
005/14 () |
Field of
Search: |
;33/18R,181R,185R,169B,125R ;415/118 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
1,009,634 |
|
Nov 1965 |
|
GB |
|
216,494 |
|
Dec 1941 |
|
CH |
|
Primary Examiner: Martin, Jr.; William D.
Attorney, Agent or Firm: Browning & Bushman
Claims
The invention having been thus described, what is claimed is:
1. A method of measuring wear and conveyance capacity of a blade of
a scroll type conveyor at least partially encased in a housing
while retaining the conveyor in assembled condition comprising the
steps of:
a. determining a critical conveyance capacity portion of said
blade;
b. determining a wear portion of said blade distal said critical
conveyance capacity portion having wear characteristics more
conveniently measured than those of said critical conveyance
capacity portion;
c. relating the amount of wear of said wear portion to the amount
of wear of and to the conveyance capacity of said critical
conveyance capacity portion;
d. exposing an aperture in said housing at a location generally
aligned with said wear portion;
e. clearing a path through a bed of sediment interior to said
aperture;
f. aligning a radially outer edge of said wear portion of said
blade with said aperture;
g. measuring the distance from said edge to a reference point
radially and longitudinally fixed with respect to the axis of said
conveyor;
h. combining the measurement obtained in step (g) with the
relationship obtained in step (c) to determine the amount of wear
of and the conveyance capacity of said critical conveyance capacity
portion.
Description
BACKGROUND OF THE INVENTION
The present invention relates to conveyors, detection and
measurement of wear in machines having relatively rotating housings
and parts such as radially extending blades subject to wear which
may exceed a critical degree, and in particular to scroll type
conveyors in which one or more helical blades are carried by a
shaft or the like and at least partially encased in a housing.
In order to convey a substance toward one end of the housing, the
blade or blades may be rotated within the housing, or the housing
may rotate about the blades, or the housing and blades may both
rotate at different speeds so that there is relative rotative
movement between the blade or blades and the housing.
The outermost edges of the blades of such conveyors wear with use,
and while it is desirable to periodically check the degree of wear,
this has hitherto necessitated the troublesome, time consuming, and
sometimes inaccurate procedure of at least partially disassembling
the machine and visually inspecting the blade. The present
invention provides a measuring device which may be inserted into an
aperture in the conveyor housing to measure the distance between
the outer edge of the blade and a fixed reference point. A plug is
used to stop the aperture when the conveyor is in operation.
Blade wear can thus be measured by stopping the machine, removing
the plug, clearing a path through the adjacent bed of sediment,
aligning the blade edge with the aperture, and inserting and
operating the measuring device.
In some types of conveyors it might be possible to have a measuring
device permanently mounted in the housing wall.
It is, therefore, an object of the present invention to provide a
means and method of measuring wear of a conveyor blade while
retaining the conveyor in assembled condition.
Such conveyors often have blade wear characteristics which vary
along their lengths. A blade may exhibit considerable blade wear
along a portion of high wear characteristics while the wear at a
second portion of the same blade having low wear characteristics
may be so slight as to be very difficult to measure. Yet this
second portion of the blade may be of critical conveyance capacity,
i.e., slight wear along this second portion may considerably reduce
the conveyance capacity of the conveyor as a whole. The present
inventor has found that, while wear and conveyance capacity vary
along a blade's length, the wear at a first portion of the blade is
usually related, so as to be indicative of, the wear and conveyance
capacity of other portions. For instance, the wear at various
portions may be mathematical functions of the wear at the first
portion. If the measuring device of the invention is located
adjacent a first portion of the blade, the measurement obtained
there can be used to determine the wear at other portions.
Preferably the measurement is taken at a first portion of high (and
therefore easily measured) wear characteristics, and used to
determine or predetermine the wear and/or conveyance capacity at a
second, less easily measured portion.
It is therefore a further object of the present invention to
provide a means and method for measuring wear at a first portion of
a conveyor blade to determine wear and conveyance capacity at a
second portion of the blade which may be less readily
measurable.
A preferred embodiment of the invention includes a plurality of
apertures in the conveyor housing for receiving a plurality of
measuring devices. These apertures are equally spaced
circumferentially of the housing at a predetermined location along
its length. This arrangement maintains the balance which is needed,
e.g. in centrifuges or other devices in which the housing rotates,
and which might be disturbed by the use of a single aperture. In
the case of a single blade conveyor, the provision of two or more
apertures in the housing reduces the amount of rotation needed to
align the blade edge with an aperture. In the case of a multiple
lead blade, i.e., a plurality of parallel helical blades arranged
about the same shaft, the number of apertures and measuring devices
provided is preferably equal to the number of blades. Then when one
blade edge is aligned with one aperture, the edges of the remaining
blades will be aligned with the other apertures so that all the
blades can be checked with the machine in a single position.
It is therefore a further object of the present invention to
provide a plurality of measuring devices equispaced about a
conveyor housing at a given location along the length of said
housing.
Other objects and advantages of the invention will be made evident
by the following detailed description and drawings wherein:
FIG. 1 is a view, partly in section and partly in elevation of a
centrifuge-conveyor representing a typical application for the
invention.
FIG. 2 is a view, with parts broken away and parts in cross
section, of the conveyor of the centrifuge of FIG. 1 and showing
one embodiment of the measuring device in position for use.
FIG. 3 is a cross sectional view of the portion of the housing
adapted for reception of the measuring device or the plug.
FIG. 4 is an elevational view of the plug of FIG. 1 on a larger
scale with the O-ring shown in cross section.
FIG. 5 is a cross sectional view of the measuring device of FIG. 2
on a larger scale.
FIG. 6 is a cross sectional view of the tip of a conveyor
blade.
FIG. 7 is a view partly in section and partly in elevation of a
second embodiment of the invention.
Referring now to FIG. 1, a centrifuge (represented generally by the
letter C) is shown which affords a typical application for the
invention. The centrifuge comprises a conveyor 2 having a conical
housing or bowl 4. A shaft 6 having a large diameter section 6a and
a small diameter section 6b runs through the housing 4, and a pair
of parallel helical blades 8 and 10 are carried by the shaft 6. The
term "helical" will be used herein to refer to any spiral blade
whether its outer diameter is uniform or varying and whether or not
the pitch is constant, and the term "parallel" will be used to
refer to the blades of multiple lead conveyors regardless of
variation in pitch.
The conveyor shaft 6 is suitably connected to an inner drive shaft
12, which is in turn connected to the output of the speed change
gear assembly 14, which has its input from the rear outer sleeve
shaft 22, to which power is transmitted by the housing 4 from the
front outer sleeve shaft 26, which is driven by a motor belted to
pulley 28. The housing 4 has integral flanges 16 and 18 at its
ends. Flange 16 is connected by bolts 20 to the integral flange of
the rear outer sleeve shaft 22. Flange 18 is connected by bolts 24
to the integral flange of the front outer sleeve shaft 26, which is
driven by pulley 28. A sleeve shaft 13 is secured to the large end
of the conveyor 2 and is rotatably supported in the sleeve 26 to
support the large end of the conveyor. Inner drive shaft 12 is
supported within rear outer sleeve shaft 22 by sleeve bearings
inside shaft 22, and shafts 22 and 26 are supported by suitable
bearings 30 and 32.
In operation, a feed, such as a slurry or suspension having a
liquid component and solid components, is introduced into the
conveyor through feed ports 34 in the shaft 6. The housing 4 is
rotated by pulley 28 and sleeve shaft 26 at a sufficient speed so
that the feed will be thrown against the inner walls of the housing
4 by centrifugal force. At the same time the blades 8 and 10 are
rotated by the gears 14 and drive shaft 12 at a different speed
than that of the housing, e.g. the blades and shaft may make 79
revolutions per 80 revolutions of the housing. Thus there is
relative rotative motion between the blades 8 and 10 and the
housing 4 which causes the blades 8 and 10 of the conveyor 2 to
plow or to scrape solid particles toward the smaller end of housing
4 and the conveyor 2.
The feed 38 enters the conveyor shaft 6 through a pipe 36 and flows
radially outwardly through feed ports 34 near the center of the
conveyor. As the centrifuge rotates, at least the coarser solids
are settled to the side walls of the housing 4, and a bed 40 of
these solids builds up between these walls and the outer edges of
the blades 8 and 10. The fluid component 42 tends to flow into the
larger end of the conveyor, and out through fluid ports 44 in the
front outer sleeve shaft 26. A relatively dry beach 46 thus forms
at the smaller end of the conveyor 2. As more solid particles build
up on top of the bed 40, the blades 8 and 10 push them toward the
smaller end of the conveyor and out through solid ports 48 in the
housing 4.
Because the solids contained in the feed are often of an abrasive
character, the edges of the blades become worn. Such wear reduces
the conveyance capacity of the blades because the conveyance areas
of the blades are reduced and a greater clearance is left between
the housing 4 and the edges of the blades 8 and 10. Thus more of
the solids are left in the bed and less volume of solids can be
conveyed toward the solid ports because the areas of the blades are
reduced.
If blade wear progresses to an extreme degree, it is possible for
the bed 40 to become so thick at the region of maximum wear that it
may form a dam and may interfere with the flow of the liquid toward
the fluid discharge ports 44. When this happens, the dammed fluid
may be forced out of the solids ports 48, which is an extremely
undesirable consequence.
Blade wear is of further concern in connection with maintenance of
the machine. As shown in FIG. 6, the tip 50 of a blade may be
provided with hard surfacing 52. When the hardsurfacing is worn
away from the outer edge 53, the softer material in the tip 50
begins to wear. When this occurs, the blade is much harder to
repair.
It is therefore highly desirable to make frequent checks of blade
wear in order to determine or pre-determine when the blade needs to
be changed or repaired either to increase conveyance capacity or to
save the blade. This is much more easily done by means of the
present invention which eliminates the need for disassembling the
machine and makes possible measurements which are quite
accurate.
Referring to FIGS. 1, 2, and 3, the housing 4 is adapted to receive
either a measuring device or a plug. Housing 4 has a broad annular
rim 54 projecting circumferentially thereof from its outer surface
with radial bores 55 extending through the housing 4 and rim 54. A
cylindrical holder 56 is mounted in the housing 4 within each of
the bores 55 by suitable means such as welds 57. While it is
possible to practice the invention by providing a single holder, it
is preferable in a centrifuge or other machine requiring balance to
provide a plurality of holders equally spaced circumferentially of
the housing at a given location along its length, i.e., a given
distance from one end of the housing. It is also preferable, where
the conveyor has a plurality of blades, to make the number of
holders equal to the number of blades. In the example shown, there
are two blades 8 and 10. Blade 8 has an end 58 (dotted line)
located 180.degree. about shaft 6 from end 60 of blade 10. This
relationship is maintained throughout the lengths of the blades
since they are parallel. Therefore, when one of these blades has
its outer edge aligned with one of the two holders 56, the other
blade will have its edge aligned with the other holder 56 since
holders 56 are located at 180.degree. about the housing from each
other.
Each holder 56 has a central aperture 62 having a threaded portion
64 located radially outermost with respect to the conveyor and a
smooth inner portion 66 of smaller internal diameter than portion
64 and located radially innermost with respect to the conveyor. A
shoulder 68 is located between portions 64 and 66. Shoulder 68 can
be parallel to the conveyor axis as shown, or it can be parallel to
the housing 4 or disposed at any other angle to the conveyor axis
so that a measurement taken normal to shoulder 68 will be
proportional to the distance from the blade edge to the housing
normal to the housing. When the centrifuge is in use, plugs 74 stop
the apertures 62. Each plug 74 has a large externally threaded end
70 for engagement in portion 64 of aperture 62, a small smooth end
72 for engagement in portion 66, and a shoulder 73 for engagement
with shoulder 68. An Allen wrench socket 71 is provided in large
end 70 to accommodate an Allen wrench for screwing plug 74 into or
out of holder 56. A resilient annular O-ring 69 is placed in an
annular groove 67 in small end 72 for forming a seal. When suitable
housing materials and other housing strength requirements can be
met, the geometry of the internal shape of holders 56 can be
machined into the parent metal of the housing 4 and broad rim 54 so
that separate holders are not needed.
When a blade wear measurement is desired, the feed through pipe 36
is shut off. The conveyor continues to run for a time in order to
clear out most of the liquid and solids therein and is sometimes
flushed with a clean fluid. The machine is then stopped and the
plugs 74 are removed. The bed 40 (FIG. 2) of solids usually remains
between the edges of the blades 8 and 10 and the housing 4. Paths
are cleared through the bed 40 directly beneath the apertures 62.
The shaft 6 is then rotated until the outer edges of the blades are
aligned with the apertures 62. A measuring device 82 is inserted in
each of the apertures 62.
Each measuring device 82 comprises a carrier 84 with a central bore
86. The carrier 84 has an upper portion 88 which is externally
threaded, a short mid portion 90 whose external diameter is
slightly less than that of upper portion 88, and a lower portion 92
of even smaller external diameter than that of mid portion 90. An
elongated cylindrical probe 94 is slidably carried in the central
bore 86. Probe 94 is of uniform diameter throughout its length
except for a wide section 96. A scale is provided near the upper
end of probe 94, and the lower end may be provided with
hardsurfacing 85. The central bore 86 of carrier 84 is of uniform
internal diameter, greater than the diameter of wide section 96 of
probe 94, throughout portions 88 and 90 and part of portion 92. At
the lower end 87 of carrier 84 in portion 92 the internal diameter
of bore 86 is reduced so that it is less than the diameter of wide
section 96 but larger than that of the other parts of probe 94. An
internal shoulder 89 is thus formed in bore 86 which cooperates
with wide section 96 to limit radially inward movement of probe 94.
The measuring device 82 also includes an annular cap 91 having an
upper portion 93 whose internal diameter is less than the width of
wide portion 96 but greater than that of the other parts of probe
94. The lower portion 95 of cap 91 is of much larger internal
diameter than portion 93 and is internally threaded so that it can
be screwed onto portion 88 of carrier 84 after probe 94 has been
inserted therein. A shoulder 97 formed between portions 93 and 95
of cap 91 cooperates with wide section 96 of probe 94 to limit
outward movement of probe 94. The straight upper surface 98 of cap
91 provides a reference line against which scale 83 can be
read.
When the measuring device 82 is inserted in aperture 62, the lower
edge 99 of carrier 84 rests on shoulder 68. The probe 94 is usually
sufficient to clear its own path through bed 40 particularly if its
lower end is hard surfaced as at 85 so that it will not become worn
and produce inaccurate measurements. When the probe 94 is pushed
into the conveyor, it contacts the edge of blade 8 or 10. The scale
83 can then be read with respect to upper surface 98 of cap 91. The
reading obtained will be indicative of the distance between the
blade edge and a reference point in the housing 4, such as the
shoulder 68, which is radially and longitudinally fixed with
respect to the conveyor axis. The reading obtained can be compared
with a similar reading taken when the blade was new (or some other
suitable norm) to determine blade wear. If desired, the scale 83
can be designed to indicate the actual amount of blade wear between
successive measurements. To again illustrate a preferred
embodiment, FIG. 5 shows that when wide section 96 of probe 94 is
resting on shoulder 89 of carrier 84, the top line 101 of scale 83
is aligned with edge 98 of cap 91. Thus line 101 represents the
greatest possible extension of probe 94 into the conveyor, and the
device 82 can be designed so that line 101 represents the greatest
amount of wear tolerable before the blades must be repaired.
It is highly desirable, in producing a number of machines, to
arrange the shoulder or shoulders 68 in each machine at given
distances from the end of the conveyor and from the conveyor axis
and at a given angle with respect to that axis so that measurements
taken in the various machines will be standarized regardless of
variations in the individual housings.
In conveyors of the type shown in FIGS. 1 and 2, the conveyance
capacity of the entire conveyor is usually dependent on the
capacity of, and therefore the amount of wear at, portions 100, 102
of the blades nearest the smaller end of the conveyor. Often a
slight amount of wear at these portions 100, 102 can greatly reduce
the conveyance capacity of the conveyor as a whole, and such a
slight amount of wear is often not easily or accurately measurable
with simple gauge means such as the measuring device 82 and the
cooperating features of the housing 4. However, the present
inventor has found that, in many types of conveyors in which
conveyance capacity criticality varies over the blade length, blade
wear and wear rate also vary over blade length. If the blade wear
at a first blade portion can be related as by mathematical
functions to wear, rate of wear, and conveyance capacity at other
portions of the blade, a blade wear measurement can be taken at the
first portion and used to determine amount of wear, rate of wear,
or conveyance capacity at one or more other portions, and in
particular, a blade wear measurement can be taken at a first
portion of high (and therefore easily measured) wear
characteristics and be used to determine blade wear at any other
portion as well as conveyance capacity at that portion at which
conveyance capacity is critical but at which wear characteristics
are low and therefore difficult to measure.
For example, in the type of conveyor shown in FIGS. 1 and 2 in
which the outer diameter of the blade varies so as to fit a conical
housing, and in which feed enters near the center of the conveyor
with liquid traveling toward the larger end and solids toward the
smaller end, it has been found that while portions 100, 102 of
blades 8, 10 have high conveyance capacity criticality and low wear
characteristics portions 104, 106 have high wear and low conveyance
capacity criticality characteristics. Portions 104, 106 wear
rapidly compared to other blade portions, and while this wear is
not usually critical to conveyance capacity of the machine, it is
critical to the life of the blades.
One wishing to produce a particular conveyor of this type can
determine empirically the rates of wear, relative degrees of wear,
amounts of wear critical to conveyance capacity, etc. for the
various portions of the blades. These values can be related by
formulae, curves, charts, graphs, or the like. Then when
measurements are taken at portions 104, 106 where wear is easily
measured, they can be used to determine wear, conveyance capacity,
etc. at portions 100, 102 or any other desired portions. Thus by a
single measurement or set of measurements, depending on the number
of gauge means employed, one could: (a) determine whether the wear
at portions 100, 102 had become sufficient to seriously impair
conveyance capacity; (b) determine whether wear at portions 104,
106 had become sufficient to seriously threaten the life of the
blade; (c) determine the amount of wear which had occured at any
given portion of the blade. It would also be possible, by means of
periodic measurements, to pre-determine the time at which the
blades 8, 10 would need repair either to save the blade or to
increase conveyance capacity of the machine or to prevent the
formation of a dam of solids in the bed. All of these things could
be done without disassembling the conveyor. Thus the wear gauge
means would be of value to a user who wished to maintain high
conveyance capacity as well as to one responsible for maintenance
of the machine and desirous of preventing excessive blade wear.
The measuring device of FIGS. 2 and 5 is considered particularly
suitable for centrifuge conveyors. However, many other types are
possible, and in other types of machines other types of measuring
devices might be preferable. It is only necessary that the
measuring device permit one to determine the distance from the
blade edge at a given portion of the blade length to a fixed
reference point without disassembling the machine. For instance, an
electronic device could be used which could utilize magnetic flux
and electrical current to measure the width of the gap between the
housing and blade, the gap being either more or less conductive
than the housing and blade.
In some types of conveyors, certainly in those having non-rotating
housings, it could be sufficient to provide only one holder and
measuring device, particularly if the conveyor had but a single
blade. However, even in single blade conveyors with nonrotating
housings there is an advantage to the use of several gauges: after
the machine is stopped, it might have to be rotated manually in
order to align the blade edge with the aperture; if several
apertures are provided, less turning of the blade is necessary to
align the blade edge with at least one of them.
A further modification might involve a measuring device permanently
mounted in the housing of a suitable type of machinery. For
instance, as shown in FIG. 7, a housing 108 is provided with an
aperture 110 and an outwardly projecting member 112 at the edge of
aperture 110. A measuring device 114 is slidably mounted in
aperture 110. Measuring device 114 comprises a vertically elongated
slide 116. At the inner end of slide 116 is a horizontally
elongated shoe 118 of sufficient length so that some part thereof
is always aligned with the outer edge of a blade 120. At the outer
end of slide 116 is a shoulder 122. A tension spring 124 engages
housing 108 and shoulder 122 to bias measuring device 114
outwardly. To take a blade wear measurement, measuring device 114
is pushed inwardly until shoe 118 contacts blade 120; a scale 126
on the slide 116 can then be read with reference to outer edge 128
of member 112.
* * * * *