Note: Descriptions are shown in the official language in which they were submitted.
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TITLE: CR~NKPIN GRINDER
This invention relatesgenerally to grindingapparatus
and refers more particularly to a method and apparatus for
grinding the crankpin journals on a crankshaft by abrasive belts.
BACRGROUND
In accordance with present practice, the crankpin
journals of a crankshaft are ground one at a time. The operation
is carried out by rotating the crankshaft about th~ axis of one
of the crankpin journals and grinding the surface of that
crankpin journal with a grinding wheel while the crankshaft
rotates. Before the next journal can be ground, the crankshaft
must be in~e~ed so that the next journal is placed on the axis
of rotation. The indexing of the crankshaft and grinding of the
crankpin journals one at a time is both time-consuming and
cumbersome. Also, rotation of the crankshaft about an offset
journal axis createsan imbalance which causes wear and sometimes
results in imperfectly ground crankpin journals.
SUMMARY
In accordance with the present invention, the
crankshaft is mounted once and once only for rotation about its
own central axis. Then several of the crankpin journals are
ground at the same time by separate abrasive belts~ There is
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no need to index the crankshaft and since the crankshaft turns
about its own central axis, imbalance is eliminated.
In accordance with a specific embodiment about to
be described, a plurality of abrasive belts are supported
adjacent to the crankshaft opposite several crankpin journals
in positions to grind the crankpin journals while the crankshaft
turns about its own central longitudinal axis. Each belt is
individually guided at its point of contact with a crankpin
journal along a variable path as the crankpin journal orbits
around the central longitudinal axis of the crankshaft. The
guiding of the belts is carried out by shoes which engage the
back surfaces of the belts. Each shoe is moved toward and away
from the crankshaft axis independently of the movement of the
other shoes. Preferably, the rotative position of the crankshaft
is monitored, and the shoes which guide the paths of the belts
at their points of contact with the crankpin journals are CNC
controlled so that the belts remain in constant contact with
the crankpin journals as the crankshaft rotates. Each shoe may
be in the form of a thin, flat blade across which the belt
slides, or in some instances it i9 preferably in the form of a
freely rotatable roller whose peripheral sur~ace has a rolling,
substantially frictionless contact with the belt.
An object of this invention is to provide a versatile
and efficient grinding machine having the above features and
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which is also rugged, durable and efficient and of relatively
simple manufacture and ease of operation.
Other objects, advantages and features of the
invention will become more apparent as the following description
proceeds, especially when considered with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a side elevational view of apparatus
constructed in accordance with the inventlon.
Figure 2 i8 a top plan view, with parts broken away,
of the apparatus shown in Figure 1.
Figure 3 is a rear view, with parts broken away.
Figure 4 is a fragmentary side view of a portion of
Figure 1 showing one of the crankpin journals in several positions
around the axis of the crankshaft with the abrasive belt shown
in solid lines in contact with the journal in one such position,
the phantom lines indicating the position of the abrasive belt
when in contact with that ~ame journal in another o~ its
positions.
Figure 5 is a view looking in the direction of the
arrow 5 in Figure 4.
Figure 6 is a vie~ looking in the direction of the
arrow 6 in Figure 5.
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Figure 7 is a fragmentary sectional view taken on the
line 7--7 in Figure 5.
Figure 8 is a fragmentary view similar to portions
of Figures 1 and 4, but showing a modificat:ion.
Figure 9 is a sectional view taken on the line 9--9
in Figure 8.
DETAILED DESCRIPTION
Referring now more particularly to the drawings and
especially to Figures 1 - 7, the numeral 10 designates a grinding
machine having a base 12 on which is mounted a slide assembly
14 for supporting a workpiece which in this instance is a
elongated crankshaft C. The slide assembly comprises a slide
base 16 which is rigidly secured to the grinding machine base
12. Parallel waybars 18 on slide base 16 slidably ~upport a
table 20 for movement along the waybars 18 by a ball screw drive
22 powered by a rever~ible motor 24. A headstock 26 is mounted
on one end of the table 20 by a bracket 28. A tailstock 30 at
the opposite end of the table i5 slidable on ways 32 mounted on
a support 34 rigidly secured to table 20. The ways 32 are
parallel to the waybars 18 to permit the tailstock to be adjusted
toward and away from the headstock 26 by the servo motor 36 and
ball screw drive 38. The ends of the crankshaft C are gripped
by collet chucks 40 and 42 rotatably mounted on the headstock
and tailstock, respectively. A servo motor 44 mounted on the
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headstock drives collet chuck 40 to rotate the crankshaft C
about its central, longitudinal axis.
The crankshaft C is an elongated member having crank
arms 46 equally spaced apart along the length thereof which
extend radially outwardly from the central axis of the crankshaft
at different angles. Each crank arm has parallel side plates
48 which support a cylindrical crankpin journal 50 near the
outer ends thereof. These crankpin journals 50 are cylindrical
members whose axes are parallel to but radially offset from the
central longitudinal axis of the crankshaft.
The base 12 has a lateral extension 52 on which a
plurality, three in this instance, of grinding units 54, 56 and
58 are mounted. The grinding units are provided for the purpose
of grinding the cylindrical surfaces of the crankpin journals
50 of the crankshaft.
Each grinding unit comprises a frame having a pair
of laterally spaced parallel side plates 60 and 62 which are
disposed in planes at right angles to tbe crankshaft C and to
the waybars 18 supporting the table 20 on which the crankshaft C
is mounted. The side plate 60 of each grinding unit is rigidly
mounted on a saddle 64 which moves in ways 66 tha~ are at right
angles to the waybars 18 for the table 20. This saddle 64 is
moved along its ways 66 by a ball screw drive 68 powered by a
servo motor 70. The grinding units 54, 56 and 58 will be seen to
be parallel to one another and to move along parallel paths.
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The side plate 62 of each grinding ullit is secured
to the side plate 60 in the parallel relationship shown by
suitable means including the spacer blocks 72. At the rear end
of the side plates 60 and 62 of each grinding unit there is a
shaft 74 which rotates in the side plates and also in a bearing
block 76 mounted on the side plate 62. A belt pulley 78 is
mounted on the shaft 74 between the side plates for rotation as
a unit with the shaft and is held in place on the shaft by
collars 80. At the upper front of each grinding unit there is
a sha~t 82 which rotates in the side plates 60 and 62 and in a
bearing block 84 on the side plate 62. A belt pulley 86 is
centered on shaft 82 for free rotation between collars 88. A
similar shaft 90 at the lower front portion of each grinding
unit rotates in the side plates 60 and 62 and also in a bearing
block 92. On this shaft 90 is mounted for free rotation a belt
pulley 94 centered between collars 95. ~n endless flexible
abrasive belt 96 extends over the pulleys 78, 86 and 94, having
an abrasive surface on the outer side and a non-abrasive backing
surface on the inner side. The abrasive belt 96 is held under
predetermined tension by a roller 98 mounted on the end of a
leaf spring 100 the opposite end of which is secured to a shaft
102 extending between the side plates 60 and 62. The abrasive
belts are disposed in planes perpend~cular to the crankshaft C
and the belts of the three units 54, 56 and 58 are spaced fro~
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each other a multiple of the distance between crank arms on the
crankshaft, in this instance a multiple of 2.
The power for driving the abrasive belts of the three
grinding units is ~rovided by a motor 104 mounted on the base
extension 52. The motor 104 rotates a shaft 106 supported for
rotation on base extension 52 by the bearing blocks 108. Mounted
at spaced points along the shaft 106 are three timing belt
pulleys 110, 112 and 114 which are secured to the shaft and
rotate as a unit therewith. The shaft 74 of each of the grinding
units has an extension upon which timing belt pulleys 116, 118
and 120 are mounted. A timing belt is provided for each grinding
unit. Thus a timing belt 122 extends over pulleys 110 and 116,
a timing belt 124 extends over pulleys 112 and 118, and a timing
belt 126 extends over pulleys 114 and 120. Associated with
each timing belt is a belt tensioner comprising a roller 128
mounted on an anm 130 carried by the side plate 60 and urged
by spring tension into contact with the timing belt. In this
nn~r, the motor 104 provide~ the power for linearly moving
the abrasive belts of all three grinding units in the direction
of the arrow 131.
A shoe 132 is provided for each grinding unit for
guiding the abrasive belt at the point where it contacts the
crankpin of the crankshaft. This shoe has a mounting portion
134 secured where indicated to the side plate 60 by a key 136
and has a projecting nose portion 138 which bears against the
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back side of the abrasive belt between the idler pulleys 86 and
94.
The nose 138 is in the form of an elongated thin flat
blade or plate which is disposed in the plane of the abrasive
belt which it backs. The length of the nose 138 is greater than
the diameter of the circle traversed by the journal pins when
the crankshaft rotates so that the belt is backed by the nose
138 and held in contact with the journal pin continuously
throughout the orbiting of the journal pin around the crankshaft
axis. The front surface 140 of the nose ~s flat and perpendicular
to the plane of the belt and contacts and guides the belt not
only at its point of contact with the crankpin journal
continuously throughout the orbiting thereof but al30 during
the approach of the belt to the point of contact and its movement
beyond the point of contact. The nose 138 has side surfaces
141 extending from opposite side edges of the front surface 140
which are perpendicular to the front surface and spaced apart
a distance less than the width of the abrasive belt.
Two sets of idler rollers 145 and 147 above nose 138
are provided for each grinding unit to fold the abrasive belt as
it approaches the nose 138 from the normal flat condition to a
generally U-~haped cross-section so that the belt as it traverses
the nose extends over the front surface 140 thereof and its
side edge portions are folded-back over the side surfaces 141
as seen in Figure 7. These rollers 145 and 147 are mounted for
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rotation on the side plates 60 and 62. Rollers 145 and 147 can
be seen in Figures 4 - 6 but have been omitted fro~ Figure 1
for clarity.
It will be observed in Figure 7 that the total width
of the nose plus the folded-back side edge portions of the
abrasive belt is somewhat less than the width of the crankpin
journal. If it is necessary to grind the full length of the
periphery of the crankpin journal, then it may be necessary to
oscillate the table 20 and crankshaft C during grinding.
Oscillating the table 20 also will cause the folded-backportions
of the abrasive belts to grind the inner surfaces of the side
plates 48 of the crank arms 46.
The rollers 145 are set at an angle such that their
peripheries are at about 45~ to the abrasive surface of the belt
as seen in Figure 6 to begin the folding. The rollers 147 are
set at an angle such that their peripheries are at about 90~,
or preferably slightly more than 90~, to the abrasive surface
of the belt, completing the folding in which the side edge
portions of the belt are folded back 90~ or slightly more than
90~ so that when khe belt reaches the nose 138 the side edge
portions of the belt will have a slight gripping action and
hug the sides of the nose.
Two sets of idler rollers 148 and lS0 5also omitted
in Figure 1) below nose 138 are provided for each grinding unit
to engage the abrasive belt after it moves beyond the nose
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138. Rollers 148 and 150 are mounted for rotation on side
plates 60 and 62. Rollers 148 are set at an angle such that
their peripheries are at about 90~ to the abrasive surface o~
the belt. These rollers 148 assist rollers 147 in maintaining
the belt folded over the nose 138. Rollers 150 are set at an
angle such that their peripheries are at about 45~ to partially
unfold the belt so that when the belt reaches roller 94 it will
return to the normal completely flat condition.
The motors 70 for moving the grinding units 54, 56
and 58 toward and away from the crankshaft C are pxeferably
driven and controlled by a CNC numerical control. ~ feed back
device 45 on the motor 44 for rotating the crankshaft feeds
back to the numerical control information regarding rotation
of ball screw drive and hence the rotative position of the
crankshaft, so that the numerical control will make corrections
as necessary and operate the motors 70 of the grinding units
to keep the abrasive belts in continuous contact with the
crankpin journals being ground during crankshaft rotation.
In operation, the table 20 is moved by motor 24 to a
position aligning three crankpin journals with the abrasive
belts of the three grinding units 54, 56 and 58. The three
grinding units are advanced by motors 70 to place the abrasive
belts in contact with the crankpin journals. The crankshaft C
is rotated by motor 44. Device 45 feeds back to the numerical
control information regarding the rotative position of the
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crankshaft C. The numerical control individually drives the
motors 70 of the three grinding units to maintain the abrasive
belts in constant contact with the crankpin journals as the
crankshaft rotates.
Upon completion of the rough or finish grinding of
three crankpin journals, the grinding units are backed off,
the table 20 is shifted to align another three crankpin journals
with the abrasive belts of the three grinding units and the
process is repeated.
If the crankpin journals are longer than the width
of the folded abrasive belt, and it is desired to grind the
full length of the crankpin journal, the table 20 may be
oscillated during grinding.
Figures 8 and 9 show a modification in which tbe shoe
for guiding the abrasive belt 96 of each grinding unit at the
point of contact with the crankpin is a roller 200. Each roller
200 is mounted on a support block 202 which is secured to the
side plate 60 of a grinding unit by a key 204. The roller turns
freely on an axis 206 which is parallel to the crankshaft C
with its periphery engaging the backing 4urface of the abrasive
belt.
The roller 200 is cylindrical and is disposed in the
plane of the abrasive belt which it backs. The axis of rotation
of the roller moves with the frame of the grinding unit on which
it is mounted along a path which intersects the longitudinal
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axis of the crankshaft. The roller is substantially larger in
diameter than the orbit of the crankpin journal contacted by
the belt which it backs. Also, the nose portion of roller 200
projects toward the crankshaft beyond the pulleys 86 and 9~ for
the abrasive belt so that the abrasive belt is wrapped around
a sufficient arcuate part of the nose portion that the beLt is
backed by the roller between points 208 and 210 and held in
contact with the crankpin journal continuously throughout the
orbiting thereof around the crankshaft axis. See dotted line
position of roller and abrasive belt in Figure 8. The thiclcness
of the roller, that is the distance between its side surfaces,
and the width of the belt, are less than the distance between
side plates 48 of the crank arms for the crankpin journals 50
so that the belt and roller can be projected between the crank
arms to enable grinding a full 360~ of the peripheries of the
crankpin journals as the crankshaft rotates 360~.
The rollers 200 are not power driven but are turned
by virtue of their substantially frictionless contact with the
abrasive belts and rotate continuously witb the abrasive belts
without slipping. This is different from the first embodiment
in which each belt slides over the surface of the back-up nose.
The rollers thus serve the back-up function without placing any
appreciable wear on the belts due to rubbing and scraping.
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.
Except as described and illustrated, the embodiment
of Figures 8 and 9 is like the embodiment of Figures l - 7 and
the operation is the same.
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