Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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SYSTEM AND METHOD OF SECURING ANNULAR PARTS
This invention deals with the field of machines and
in particular a system and method for securing annular parts
in a fixed location within a machine.
OF TSE INVENTION
A common task in making machines is to secure
annular parts in such fashion that they are held securely in
position, within very close tolerances. Annular parts, such
as bearings, bushings and pressure seals, present a difficulty
in that the part must be held so that it does not move
radially or laterally. Radial movement is prevented by
mounting the annular part in a housing. Lateral movement
along the axis of the annular part is prevented by providing a
radially extending projection on the outer circumference of
the annular part which projection mates with a similar recess
in the inside circumference of the housing. The housing is
commonly in two pieces allowing the annular part to be placed
in position in a groove in the first side of the housing, the
second side then being bolted to the first side, securing the
annular part in place in the housing. The two sides of the
housing may be separated radially, perpendicular to the axis
of the annular part, or laterally, parallel to the a::is of the
annular part.
The crankshaft bearings of an internal combustion
engine are an example of the use of a split two-part housing.
There is a first half of a circular hole cast into the bottom
of the engine block, the second half of the hole being
provided by a bearing cap which is bolted to the engine block,
thereby forming the housing hole which retains the bearing.
The bearing is prevented from moving laterally by a projection
on the bearing which mates with a groove or notch in the
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engine block.
A milling machine is most often used to line bore
the housing. The milling machine has a shaft attached to a
spinning head at one end and an outrigger support bearing at
the opposite end. A cutting tool is mounted a at a mid-point
of the shaft. In the case of the crankshaft example, the
bearing cap is bolted in position to the engine block, forming
the rough hole, with the shaft of the milling machine
extending through the rough bearing holes. The engine block
is moved along the shaft so that the mid-mounted cutting tool
can pass through the axis of all the bearing holes, thereby
finishing the rough holes. Using this method, the shaft of
the milling machine must be twice as long as the engine block.
The set-up for line boring is cumbersome and time consuming as
the two parts of the housing must be assembled in order to
bore the holes. This makes the process expensive. The
machine tool operator using this method must be highly
skilled, as constant measuring and adjustment is necessary in
order to produce satisfactory results. There is always the
risk of human error.
This method is generally satisfactory, however it
presents problems in manufacture, especially when the housing
must be cut and machined at some distance from the head of the
milling machine. The longer the shaft must be, the more
vibration there will be and the accuracy of the cut will be
reduced. Another problem is cutting tool wear. As the cutter
moves along from housing to housing the tool wears and becomes
slightly smaller.
These problems are accentuated when manufacturing
mufti-stage pumps, where the distance from the head of the
milling machine to the cutting tool can be five to ten feet or
more. It is virtually impossible to standardize the housing
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size within the required tolerances. The annular seals must
then be machined to fit the housings between each different
stage. Individual manuals are then needed for each machine
giving the dimensions for each housing and seal, in order to
allow the proper size replacement seals to selected for each
housing. This is a very time consuming and expensive process,
and leads to further expense as replacement parts cannot be
standardized. Again in such multi-stage pumps, the closer the
tolerance of the seals, the more efficient the pump since
there is less leakage between stages. In such pumps, the
central rotating shaft runs inside the seals, with a gap of
approximately six thousandths of an inch between the shaft and
the seal. This gap could be reduced if the tolerances between
the seal and the housing were smaller, and efficiency would be
improved as leakage between the shaft and seal is reduced.
Similarly, leakage between the seal and the housing would also
be reduced, further increasing efficiency. The set-up for
boring these large pumps is particularly cumbersome and time
consuming, as the parts are very large.
Those skilled in the art will recognize that an
improved system and method of securing annular parts would
have applications in many different machines where similar
problems of manufacture occur. Many of the manufacturing
probls~ms noted above could be overcome by a system designed so
that the housing could be machined by a cutting tool having
the driving head located close to the cutter. It Would also
be a particular advantage if the housing parts did not have to
be assembled and then disassembled during the process.
SUMMARY OF THE INVENTION
It is therefore the object of the present invention
_ to provide a system and method for securing annular parts in
machines that a.s faster, easier and cheaper to manufacture
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than present syst~as.
It is the further object of the present invention to
provide such a system and method that provides for increased
accuracy of machining, allowing reduced clearances between
parts of the machine.
It is the further object of the present invention to
provide such a system and method where the housing for the
annular part could be machined by a cutting tool having the
driving head located close to the cutter.
The present invention provides a system for securing
annular parts comprising a two part housing, each said part
having an outer surface integral with, or attachable to, a
machine, and an inner surface for securing an annular member
and each said part defining one half of an annular groove on
the inner surface thereof such that when the two parts are
fastened together, the annular groove is on the inner surface
of the housing; and an annular member having an outer surface
mating with said annular groove; wherein said groove has a
cross-section that is an arc of a circle, said circle having a
radius less than the radius of said annular member.
The present invention further provides a method of
securing annular parts comprising the steps of securing one
part, the first part, of a two part housing to a machine
table; using a ball-nose cutter having a radius less than the
radius of the annular part that is to be secured, said ball-
nose cutter held in the spindle of a computer controlled
milling machine, cutting a first groove in the inner surface
of the first part of the housing, said first groove being one
half of the total groove that will result when the two parts
of the housing are fastened together; repeating the two steps
above for the second part of the housing; machining the outer
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surface of the annular part that is to be secured so that said
outer surface mates with said total groove; placing said
annular part into the groove, being one half of the total
groove, in one part of the housing; and fastening the two
parts of the housing together.
Recent innovations in cutting tools have made
possible this new system. A computer controlled milling
machine may be positioned over a workpiece of essentially any
size. Such a milling machine uses computer control to move
the cutter through any defined path in three dimensions, which
has net previously been possible. The computer control
greatly reduces the possibility of human error.
Thus a cutter may be programmed to travel in a near
perfect circle, or semicircle. A ball-nose cutter travelling
in a semi-circle will leave a groove that has the cross-
section of an arc with a radius equal to the radius of the
ball-nose cutter. Thus the two parts of a split housing may
be grooved separately so that when they are joined, a very
accurate circular groove will be left on the inner surface of
the housing which groove may be mated to an annular part with
a circumferential surface of the same radius.
When the radius of the groove is less than the
radius of the annular part, the annular part will be held
rigidly in place, as the annular part cannot twist. The
improved accuracy allows for reduced tolerances. Thus where
the annular part is a seal, the shaft may pass through the
center hole of the seal without touching the seal, while
leaving a very small gap. This increases the efficiency of
the seal while reducing wear of the seal. Similarly, the
clearance between the housing and the seal may be reduced,
again increasing the efficiency of the seal. If even further
efficiency is desired, a further groove or grooves for an O-
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ring seal may be machined into the outer surface of the seal,
such that the O-ring will bear on the inner surface of the
groove in the housing.
Where a longer annular part, such as a cylinder, is
to be secured in the housing, a series of circular grooves
could be cut in the housing, with the outer surface of the
cylinder machined to mate with the series of grooves.
Alternatively, the ball-nose cutter could be programmed to cut
the series of grooves so close together that a groove is
formed that is substantially flat in the middle portion, with
side-walls having the radius of the ball-nose cutter.
In yet a further embodiment of the invention, there
is provided a system for securing annular parts comprising a
two part housing having an inner surface for securing an
annular component, one half of said inner surface being
defined within one of said parts and the other half of said
inner surface being defined within the other of said parts,
said one half of said inner surface being an out of round
configuration and said other half of said inner surface being
an out of round configuration.
In still yet a further embodiment of the invention,
there is provided a method of securing annular parts within a
housing, said annular parts being used for holding a circular
m~mber rotating within said annular parts, said method
c~prising machining a first out of round configuration on the
outside of said annular parts, machining a second out of round
configuration on the inside of said housing holding said
annular parts, said first out of round surface on said inside
of said housing mating with said second out of round
configuration on said outside of said annular parts.
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DESCRIPTION OF THE DRAWINGS
While~the invention is claimed in the concluding
portions hereof, preferred embodiments are provided in the
accompanying detailed description which may be best understood
in conjunction with the accompanying diagrams where like parts
in each of the several diagrams are labelled with like
numbers, and where:
Figure 1 shows a front and a side plane view of an
embodiment of the invention;
Figure 2 is a perspective view of the embodiment of
the invention of Figure l;
Figure 3 is a cross-section view of an alternate
embodiment of the invention;
Figure 4 is a cross-section view of an embodiment of
the invention for use on long, cylindrical parts;
Figure 5 is a cross-section view of an embodiment of
the invention including O-ring seals;
Figure 6 is an end view showing a preferred method
for making the grooves to secure the annular parts;
Figures 7A and 7B are front and side views of an
annular component according to the invention having a circular
configuration wherein the component may otherwise rotate
within a housing used to hold the component;
Figures 8A, 88 and 8C are front, side and bottom
views of an annular component according to a further aspect of
the invention in which the shape is more elliptical and out of
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round thereby preventing rotation within a housing; and
Figures 9A and 98 are front and side views of a
housing used to hold the annular component of Figures 8A, 88
and 8C thereby preventing rotation of the component within the
housing.
DETAILED DESCRIPTION OF T8E EI~ODII~NT
The invention is a system for securing annular parts
comprising a two part housing, each said part having an outer
surface integral with, or attachable to, a machine, and an
inner surface for securing an annular member and each said
part defining one half of an annular groove on the inner
surface thereof such that when the two parts are fastened
together, the annular groove is on the inner surface of the
housing; and an annular member having an outer surface mating
with said annular groove; wherein said groove has a cross-
section that is an arc of a circle, said circle having a
radius less than the radius of said annular member.
Figures 1 and 2 show one preferred embodiment of the
invention. Top housing 1 and bottom housing 2 are held
together by bolts 3. Groove 4 has a radius R1 which is less
than the radius R2 of the annular part 5. Annular part 5 can
be a bearing, seal or any required part. The outer surface 6
of the annular part 5 is machined to mate with the groove 4.
Figure 3 shows an alternate embodiment where the
housing is split along the perimeter of the groove. Right
housing 7 and left housing 8 are fastened together by bolts 3
to form the groove 4, which has a radius R1 which is less than
the radius R2 of the annular part 5, and which secures the
annular part 5 in the housing.
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There are two critical points to make the system
work. First, for an annular part 5 having a length L less
than twice its radius R2, the radius R1 of the cross-section
of the groove 4 must be less than the radius R2 of the annular
part 5. This feature is what prevents the annular part 5 from
twisting in the groove 4. It is contemplated that, for best
results in most applications, R1 should be less than .75 R2.
For an annular part 5 having a length L greater than twice its
radius R2, this is not a critical factor, as the annular part
will be held as in Figure 4, with a plurality of grooves 4,
and thereby prevented from twisting.
Second, one half of the groove 4 must be defined by
each of the two housing parts. In either the embodiment of
Figure 1 or Figure 2, one half of the groove 9 a.s defined in
each part of the housing. If more of the groove 4 is in one
part than the other, the groove 4 halves will not meet at a
tangent to the groove 4, and the annular part 5 will not go
into the groove in the part of the housing which defines more
than one half of the groove. It will be noted that in the
embodianent of Figure 1, each part of the housing defines a
groove that is a half circle, while in Figure 2, each part of
the housing defines a groove that is a circle and is one half
of the total groove.
Figure 4 shows an embodiment of the invention for
use to secure a long annular part 20. Long top housing 9 and
long bottom housing 10 define a plurality of grooves 4. In
this embodiment the length L of the annular part 5 is greater
than twice the radius R2 of the long annular part 20, and the
radius R2 of the grooves 4 is not critical.
Figure 5 shows an embodiment of the invention
further iacluding two O-rings 11 in O-ring grooves 12, for
increased sealing efficiency.
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The present invention further provides a method of
securing annular parts comprising the steps of securing one
part, the first part, of a two part housing to a machine
table; using a ball-nose cutter having a radius less than the
radius of the annular part that is to be secured, said ball-
s nose cutter held in the spindle of a computer controlled
milling machine, cutting a first groove in the inner surface
of the first part of the housing, said first groove being one
half of the total groove that will result when the two parts
of the housing are fastened together, which total groove has a
cross-section that is an arc of a circle, said circle having a
radius less than the radius of the annular part that is to be
secured; repeating the taro steps above for the second part of
the housing; machining the outer surface of the annular part
that is to be secured so that said outer surface mates with
said total groove; placing said annular part into the groove,
being one half of the total groove, in one part of the
housing; and fastening the two parts of the housing together.
Figure 6 shows this method in use to secure seals in
a multi-stage pump. Pump half 13 is mounted to a machine
table 14, which table 14 is movable in the X-axis as shown,
and which movement is controlled by a computer. Ball-nose
cutter 15 is held in the end of the spindle 16 in the head of
a milling machine 17 which head 17 is movable in the Y-axis as
shown, and which movement is controlled by a computer. The
radius R3 of the ball-nose cutter 15 is substantially leas
than the radius R4 of the bore hole 18 which will be occupied
by the seal. The computer coordinates the movements of the
machine table 14 in the X-axis and head 17 in the Y-axis so
that the ball-nose cutter moves in a semicircle around the
inside of the housing 19 which is as integral part of the pump
half 13, leaving a groove whose cross-section is the arc of a
circle having the same radius as the ball-nose cutter 15.
This process is repeated for all necessary seal housings in
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the first pump half 13.
The same procedure is applied to the opposite pump
half, the seals that have been machined to mate with the
grooves in the pump are placed into the grooves 4 in one pump
half and the two halves are bolted together, securing the
seals.
Figure 6 shows that the cutting tool, the ball nose
cutter 15 is located very close to the workpiece, the pump
half 13, greatly increasing the accuracy by reducing the
vibration that is inherent in line boring, where the milling
machine spindle must be twice as long as the piece being
bored. It is also plain that the cutting tool, the ball-nose
cutter 15, is readily accessible to check for wear and make
any necessary changes. As well, the set-up is simple, as the
two parts of the housing can be cut while apart, doing away
with the assembly and dis-assembly needed for line boring.
The computer control of the custom process greatly reduces the
possibility of human error.
A further embodiment of the invention is
contemplated with regards to Figures 7, 8 and 9. An annular
component generally illustrated at 700 in accordance with the
teachings of the invention has a circular outer circumference
701. The annular component 700 is held within a housing (not
shown) which has a similar circular inside configuration.
Means by way of a protuberance in the housing or similar
restraint device is required to prevent the annular component
from rotating within the housing about its axis.
Reference is now made to Figures 8A through 8C where
the annular component generally illustrated at 800 has an
outer perimeter 801 which is non-circular in configuration,
being more cloaely resembling an ellipsoid type shape although
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other out of round configurations are contemplated. The
annular component may be made in a one-piece configuration or
split along the plane C running through its center line.
The housing to hold the annular component is
generally illustrated at 900 in Figures 9A and 9B. The
housing 900 has a base portion 901 and a top half 902. The
inside 903 of the housing 900 will be formed with the same
configuration as the perimeter of the annular component 800
thereby allowing the annular component 800 to be securely held
within the housing 900.
In operation, as the shaft (not illustrated) or
other circular object passes through the annular component 800
and is rotated, there will be a tendency for the annular
component 800 to rotate within the housing 900 about the axis
of rotation of the shaft. However, the out of round
configuration of the outside of the annular component 800 will
prevent such rotation and contribute to the stability of the
annular component 800 within the housing 900.
Thus it can be seen that the invention accomplishes
all of its stated objectives. The foregoing is considered as
illustrative only of the principles of the invention.
Further, since numerous changes and modifications will readily
occur to those skilled in the art, it is not desired to limit
the invention to the exact construction and operation shown
and described, and accordingly, all such suitable changes or
modifications in structure or operation which may be resorted
to are intended to fall within the scope of the claimed
invention.
