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Патент USA US2114040

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April 12,1938.
V
2,114,040
M. A. BECKMANN
EVEN PRESSURE PISTON
Filed May 12, 1956
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April 12, 1938. ‘
M. A. BECKMANN
2,114,040
EVEN PRESSURE PISTON
Filed May 12, 1936
2 Sheets-Sheet 2
Patented Apr. 12, 1938
2,114,040
UNITED STATES PATENT OFFICE
2,114,040
EVEN PRESSURE PISTON
Melbourne A. Beckmann, Cincinnati, Ohio, as
signor to Aluminum Industries, Incorporated,
Cincinnati, Ohio, a corporation of Ohio
Application May 12, 1936, Serial No. 79,309
5 Claims. (Cl. 309-11)
This invention relates to a piston for internal
combustion engines especially those of automo
biles, and is especially adapted for those made
from aluminum alloys. Other metals may be
5 used however.
The general object of the invention is to pro
vide a piston that will bear evenly on the cylinder
wall at substantially all points of the piston's sur
face and at substantially all times and tempera
10 tures.
Another'object is to provide a construction in
which the flow of heat from one part of the piston
to another is unhampered altho a slot in the skirt
is provided, which ordinarily would be a bar 'to
heat ?ow.
Another object is to provide a piston in which
the skirt is reinforced against collapse in such a
way that the reinforcement has the greatest
strength where it is the most needed. Converse
20 ly, the greatest amount of diameter adjustment is
obtained where it is most necessary.
Another object is to provide a piston which is
stabilized against rocking.
Brie?y stated, the invention resides in the com
grinding of the piston is exaggerated for purposes
of illustration.
Fig. 3 is a transverse sectional view taken along‘
the line 3-3 of Fig. 1.
Fig. 4 is an elevation of that side of the piston
on which the slot and bridge are located.
As shown, i0 is the hollow head, H the skirt of
the piston and I2 the usual ring grooves. Below
the grooves. 90° away from the pin bosses l3 there
is a T-slot comprising a short horizontal slot I4 . g
and a relatively longer, slightly slanted, almost
vertical slot l5. The pin bosses have the usual.
hole l8. Straddling the slot l5 there is‘a hairpin
bridge I6 which extends vertically from a point
just under the head Hi to a distance of 1/4" to %”
5
from the bottom of the skirt on an ordinary
passenger automobile piston. At the top, the
bridge is considerably narrower than at the bot
tom, altho its angle of dehiscence remains the
same. This implies that the back ridge ll of the 20
bridge is not vertical and in fact, it slants toward
the lower part of the vertical middle axis of the
piston. The bridge is cast integrally with the
p‘ston. It is cut by the slot M which severs the
tip from the skirt portion. The upper tip 2
a “hairpin” or segment-enclosing bridge or gusset upper
is solid.
'
across the slot, the bridge being integral with the ,
By the hairpin bridge I mean a bridge having a
piston body. The height of the hairpin bridge
increases progressively toward the bottom of the cross-section shaped‘like the connecting portion
25 bination'of a cam ground slotted skirt piston with
30 skirt so as to obtain a gusset function of progres
sive rigidity, increasing toward the piston head.
Last but not least, an object of the invention is
to provide these advantages in a form that will
be commercially successful because it is well
adapted to production by the permanent mold
process.
-
Heretofore it has been attempted to reinforce
the skirts of slotted ‘pistons with steel springs of
various shapes, commonly called “expanders”.
40 These‘ press the skirt against the cylinder wall
between the two arms of a conventional hairpin. ‘
The angle of dehiscence of the bridge from its
ridge to the skirt is preferably 15 degrees (in
cluded angle) but may range from 10° to 50°.
When a 15° angle is employed, the piston is cam
ground as shown in Figs. 2 and 3. That is to say, 1
the diameter thru the pin bosses is from three to
ten thousandths of an inch shorter than the di
ameter at 90 degrees to said pin boss. This grind—
ing is employed because the piston has a greater
expansion along the pin bosses than in a direction l
when the piston is cold, making starting dii?cult
90° from them.
and when the piston becomes hot they do not
cam-grinding per se', but in combination with the
No originality is claimed for
promote even heat'distribution in an aluminum ‘ bridge. even pressure on the cylinder walls is pro
duced over the entire piston. which is not the
piston because their heat conductivity is so much
less than that of aluminum. My reinforcement
has no spring action nor does it diminish heat
?ow, yet it strengthens the skirt and holds it in
proper working position. 'Because the skirt is so
held, the piston has less tendency to rock.
In the drawings, Fig. 1 is an elevation, partly in
section, of my piston, the sectional part being
case with a cam-ground piston that lacks my .
bridge. On the other hand my bridge on a round
piston produces a result that in certain cases
eliminates the need for a cam-grinding to‘ obtain
substantially even pressure. Such construction
is disclosed in my co-pending application Serial
No. 79,310 ?led May 12, 1936.
Nevertheless, 'it
taken along the vertical part of the slot.
lies within the scope of the present invention to
Fig. 2 is a plan view of the piston with portions employ the bridge of increasing height herein dis
of the piston head broken away and the bridge‘ closed on a round piston because a round piston
and pin bosses shown in dotted line. The cam even with no special features except the bridge 4
2
Cl
2,114,040
and slot, will give better results than any round
It is of course, necessary to adopt different
piston without them or with only a slot.
In operation the superior e?'ects occur as will
now be described in the case of the construction
clearances in cam-grinding when an alloy of a
shown, applied to an automobile piston 31/2" di
ameter by 4" long. This piston is cam-ground to
six thousandths diameter differential and has a
15° bridge. The piston alloy runs:
-
Per cent
10 Copper ________________________ __
0.5 to 1.5
Silicon _________________________ __ 12.5 to 14.5v
Magnesium ____________________ __
0.75 to
Iron ____________ __, ________ _.______
1.00
Nickel _________________________ __
2.00 to
Zinc ___________________________ __
1.05
Manganese ____________________ __
0.05
Aluminum.a ___________________ __
1.00
3.00
Balance
This alloy has a coe?icient of expansion of
0.000011 inch per inch per degree Fahrenheit up
to 500° Fahrenheit.
As the engine heats, the piston expands on both
diametrical axes simultaneously and reaches even
pressure in both directions simultaneously. The
bridge has no tendency to push the skirt against
the cylinder wall as occurs in the case of steel
expanders, since the bridge is made of the same
metal as the skirt. A steel spring expander
makes an engine hard to start and this is not the
different coe?‘icient of expansion is used than the
one mentioned. This is however, a matter that
any competent piston designer can solve if he is
acquainted with the principles herein disclosed.
The operating temperatures in the engine also
have some eifect but the principles are operative
up to the incipient fusing points of the metals
employed.
10
In the construction here shown it is easy to pull
out the iron core used in the permanent mold to
make the hairpin bridge hollow. This is be
cause of ample draft since the bottom of the core
is smaller than the top. The facility of produc
ing the entire piston by the permanent mold pro
cess is shown‘ in my co-pending application Se
rial No. 85,946, ?led June 18, 1936. No machin
ing of the bridge is required.
20
I claim as my invention:—
1. A piston for internal combustion engines
which comprises a head, a skirt attached thereto,
piston pin bosses within said skirt, a T slot in
said skirt at substantially 90° from the axis of
said bosses and an integral hairpin bridge adapt 25
ed to act as a gusset, said bridge joining the ends
of the skirt across said slot, the height of said
bridge increasing progressively toward the bot
tom of the skirt.
case with my bridge because it does not act as a
2. A piston for internal combustion engines 30
spring, but as a gusset. Some steel expanders which comprises a head, a skirt attached thereto,
interrupt heat ?ow. The function of my bridge . a pair of piston pin bosses within said skirt,,a
is to stabilize the piston and to keep the skirt T slot in said skirt at substantially 90° from the
from collapsing. In an automobile engine, the axis of said bosses, an integral hairpin bridge
greatest pressure on the piston is exerted on that adapted to act as a gusset, said bridge joining the 35
side which is on the right from the driver's seat. ends of the skirt across said slot having an angle
That is the side here shown uncut vertically and
experience has shown that it is the side which
should so remain. The opposite side therefore is
the one which should have the function of adjust
'40 ing itself to the cylinder and this is the one se
lected for my bridge.
As is well known, the head of a'piston is the
end which grows hottest in use. Since the skirt
does not grow so hot, it is necessary to have small
er clearances at the bottom of the skirt when the
piston is put into service, than would be necessary
if the piston attained the same heat all the way
down. In the present invention, close attention
need be paid only to head clearances because the‘
skirt will adjust itself. This is because the bridge
16 is progressively higher at the bottom of the
skirt than at the top. Consequently, the skirt
can be more easily compressed at the bottom
while at the top it is held with greater rigidity
against heat expansion.
1
The net result is that a piston built according
to this invention adapts itself according to its
temperature to bear on the cylinder walls with
substantially equal pressure top and bottom, left
and right. The bridge limits the "accordion” ac
tion of the split skirt, thereby avoiding metal
fatigue due to long repeated bending during op
eration.
At the same time, a close enough ?t of the
skirt in the cylinder is maintained so that the pis
ton has little or no tendency to rock’end for end.
This is what'I call stabilizing action. The clear
ance is always substantially the same, hot or cold
in a diametrical direction across the piston pin
axis. When the piston heats in operation, the
diameter along the piston pin axis becomes the
same as the diameter across it.
So the piston is
entirely round when hot due to practically com
plete closing of slot l5 but both stabilized and
reinforced whether hot or cold. '
of dehiscence of about 15° and increasing in
height toward the bottom of the skirt.
3. A piston for internal combustion engines
which comprises a head, a skirt attached there 40
to and a pair of pin bosses within the skirt; said
piston being from 3 to 10 thousandths of an inch
shorter across that diameter which coincides with
the piston pin boss axis than that diameter which
lies at 90° therefrom, a-T slot in said skirt 90° 45
from the axis of said bosses and an integral hair
pin bridge joining the ends of said skirt across
said slot the height of said bridge increasing to
ward the bottom of the skirt.
4. A piston for internal combustion engines 50
which comprises a head, a skirt attached‘ thereto
and a pair of pin bosses within the skirt, said
piston being from 3 to 10 thousandths of an inch
shorter across that diameter which coincides
with the piston pin boss axis than that diameter 55
which lies at 90° therefrom, a T slot in said skirt
90° from the axis of said bosses and an integral
hairpin bridge joining the ends of said skirt
across said slot the height of said bridge increas
ing toward the bottom of the skirt, the metal of 60
the piston having a coefficient of expansion of
substantially 0.000011 inch per inch per degree
Fahrenheit.
‘
5. A piston for internal combustion engines
which comprises a head, a skirt attached there 65
to, piston pin bosses in said skirt, a T-slot in said
skirt at substantially 90° from the axis of said
bosses and an integral bridge acting as a gus
set and joining the ends of a skirt across said slot,
said bridge comprising relatively thin and rela 70
tively high walls converging at a dihedral angle
in the vicinity of 15° to a rounded connecting por
tion, and said bridge increasing in height toward
the bottom‘ of the skirt.
MELBOURNE A. BECKMANN.
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