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Патент USA US2110345

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March 8, 1938.
Filed July 3l, 1954
' S22
'24 23
Patented Mar. 8, 1,938
Ralph R. Teetor, Hagerstown, In ., assignor Ato
The Perfect Circle Company, Hagerstown, Ind.,
a corporation of Indiana
Application July 31, 1934, Serial No. 737,800
6 Claims. (Cl. 309-13)
This inventionr relates to pistons for internal of the piston while Vthe piston is being rotated.
combustion engines and the like.
The skirt after the sizing operation and while the
The principal object of my invention is to provide a piston so constructed that the desired
5 clearances between the skirt and cylinder Wall at
right angles to the piston pin may be maintained
throughout the operating range of the engine. I
provide> a piston of aluminum alloy or the like
which is simple in structure and cheap to manu-
piston head is hot is round or cylindrical. Upon
cooling of the piston, the head shrinks more than
the skirt and the hangers, being connected rigidly 5
and directly to the top of the' skirt, pull in the
portions of the skirt in line with the pin bosses so
that the skirt becomes elliptical with the major
axis at right angles to the axis of the pin bosses.
10 facture, while at the same timefthe piston is free
from the objectionable> defects present in the
slotted skirt type of aluminum pistons now on the
Using this cooled’piston as a pattern, I form a 10
cam to be used in a machine which will form
turn or grind the skirts of `other pistons in pro
The above and further objects of my invention
_15 will appear more fully from the following description, reference being had to the accompanyin'g drawing in which:
Fig. 1 is a vertical sectional view through `a
piston embodying the preferred form of my in20 vention;
Fig. 2 is a vertical sectional view through the
piston, the section being at 90° -to that of Fig. 1;
Fig. 3 is a cross sectional view through the
piston, taken~ on line 3-3 of Fig. 1;_ and
25 Figs. 4 and 5 are plan and side views, respec-
duction to the desired elliptical form.
With the piston in the cylinder, when _the en
gine is cold there is the correct clearance between l5
the cylinder wall and the bearing surfaces of the
piston skirt which are midway between the piston
pin bosses. As the engine becomes heated in
operation, the piston head is heated to a much
higher temperature than the skirt with the result 2o
that the head tends to expand twice‘as muchas
the skirt or thereabout. The expansion of the
head separates the hangers and thus increases the
diameter of the top of the skirt in the plane of
the axis of the pin bosses, the hangers being 25
tively, of one of the cross struts.
Thepistoncomprises ahead I6 separated from
the skirt I1 by the slot I8. 'I'he skirt is provided with piston pin bosses I8 and the head,
30 upper portion of the skirt and the bosses are connected together by integral hangers or webs 20.
'I‘he piston is formed of the usual aluminum alloy
or the like.
Near the bottom of the skirt are two cross
_struts 22, formed of metal known as Invar, or
fsb Gil _ steel or some other suitable metal having a lesser
coemcient of expansionthan the head and skirt.
As illustrated in Figs. 4 and 5, one form o! each
strut may be L-shaped in cross section and have
40 inclined end ears 23 provided with apertures 24'.
As best shown in Fig. 3, the end portions of the
struts‘ including the apertured ears 23 are embedded in thickened portions 25 of the skirt.
In.` casting the piston, above described, the
45 cross struts are mounted in arnold and the piston
is then cast so that the ends of the struts are embodied in the thickened portions of the piston
skirt. In order to impart to the skirt the desired
elliptical or out of round shape or form, I pref50 erably take a piston after it has been cast, heat
the head _to approximately the temperature to
which the head would be heated under normal
operating conditions in an engine and then while
the piston is in this heated condition size it by
55 a tool brought into engagement with the skirt
inflexible and connected directly to the upper
portion of the skirt. In other words the expan
sion of the head tends to change the upper por
tion of the skirt from its elliptical form to one
approaching a round form by increasing the 30
diameter in the plane of the pin bosses so that it
approaches the diameter at right angles thereto.
'I'his tends to decrease the latter diameter. At
the same time, however, the aluminum of the
skirt expands circumferentially due to the heat, 35
so that -while the expansion of the head may
tend to reduce the major axis which is at right
angles to the pin bosses, yet the inherent expan
sion of the skirt slightly more than compensates
for this with the result that the desired clear- 40
ance at the top of the skirt bearing faces is main
tained. In other words, the distance between
the bearing, faces increases slightly as the diam
eter oi' theengine cylinder increases.
The struts 22 also perform the function of 45
maintaining this desired clearance at the bottom
of the bearing faces. After the piston is cast the
aluminum cools so, of course, the struts are al- _
ways in compression and they tend4 to maintain
the diameter of the lower ends of the bearing 50
faces about the same when'the piston is cold as
when it is hot. As the skirt becomes heated dur
ing operation of the engine, the aluminum ex
pands circumferentially but the expansion nec
essarily takes place for the most part- on the 55
minor axisof the skirt. This may tend to flatten
'out the bottom portions of the bearing faces be
tween the ends of the struts but this tendency
is slightly more than compensated for by the
circumferential~ expansion ci’ the skirt, so'that
as the diameter of the engine cylinder increases,
to tend to satten out during thermarerpshsinnf
of the piston skirt, said struts each being so
shaped and constructed that they are iniiexibie
and are of such length that they are held under
constant compression by said skirt, the force of i
compression being suiiiciently‘great
it will
not be‘released by the thermal expamion of said
bearing faces increasesand the correct clearance skirt
during operation in an engine.
between the cylinder wallvand these portions oi?v
the bearing faces is maintained.
It will thus beseen -thai; the diameter‘of the'KV
'the distance between the bottom portions of the ,
piston> skirt from top to bottom is'properly con
. trolled during the operating range oi' the engine
so that the desired clearance between the bearing
faces and cylinderwallis maintained throughout
therebetweenv extending substantially through
out the circumference of the piston,
bosses integral with the skirt and on the minor
axis of the latter, hangers integral with the head
their length, thediameter of the skirt in line with ' and upper- portionl ot the skirt, the hangers
the pin bosses being permitted vto change without >in_g
inflexible so that the expansion of the I..
4impairing the emciency of the engine. and with
upon beingiheated in anengine tends to
out danger of scoring and the like.
the upper portion of the skirt fromI its elliptical
It is understood that my invention is not lim vform to one approaching a round form,
ited to the details of construction shown and that struts having a lower coemcient of expansion
other forms may be used without departing i’romV than said skirt and arranged parallel to the
the scope. of my invention.
major axis of the’skirt in the lower portion of
I claim:
l.’1n~a piston'V formed of metal having‘a high
coeiiicient `of expansion, ahead.. a continuous
skirt of elliptical form'in rcross-section from one
„ end thereof to the other, the upperedge of said
' skirt being separated from said headby a slot ex
tending substantiaily throughout the circum
ferenceof the piston. rlgid'hangers connecting
the skirt, the struts
having their ends imbedded'
with the skirt and being of such length that they
are held under constant compression by the
skirt so that the circumferential expansion ofthe
skirt upon becoming heated in an engine tends to
change the lower portion ofthe skirt from its
` elliptical 'form to one'approaching a round form.
the length of the major axis remaining substan
l'together said head and the upper end of said tially
skirt, piston 1 pin bosses on
skirt and on the
4. In a piston formed of metal having a high
minoraxis o'f the ellipse of saidskirt, and a pair
-of struts eachformed of a material _having a' coemcient of expansion, `al. head. a continuous
walled skirt having an“` elliptical cross-sectional
much'lower'ccemcient of expansion than Vsaid shape
with the bearing face portions on the
skirt and disposed within said" skirt- belo'w. Said ~ major axis,
bosses'on the minor. axis
pin bosses‘and parallel to the major axis of the. ofthe ellipsepisto?fpin
oi' the skirt, and two spaced
ellipse of said skirt with their ends Vembedded in struts having-a
lower coemeient `ofgexmimicn» l
jthewalirof-said skirt'at points substantially than said skirt and’dlsposed
within 'said‘ lkii't
spaced apart.v said vstruts eachbeingsoshaped».
and sub
and constructed that they are iniiexible and are stantially parallel to the maior bosses
axis of said el
~ of such length that they are held under constantl
compression by said skirt, the force of compres
lipse'. the struts being inflexible and the
hearing `
sion. being sutli'ciently great that it will not be ` face'portions between the ends of the struts be
ing flexible, whereby said bearing face portions
released by; thermal expansion'ot said skirt dur
ing operation ln an engine.
tend to‘ilatten >out during thermal expansion of \
coeiiiclent 'of expansion, a head, a continuouswalled skirtr having an elliptical cross-sectional
`of theskirtincreasess
2. In s piston formed ormetsi having a high'> the piston‘skirt and the V'lengthof the minor axis
shapefrom one endto'the otheryop'posed rigid
hangers integral with and depending from said
"head and integrally connected to the upper end
- of said‘skirt von the rminor axis ofthe 'ellipse of
the latter, said headbeing` separated from the
_ 5. In a plston'fonned oi'i‘metal having a high
4coeiilcient of expansion, a continuous ' walled
skirt having. an elliptical cross-sectional shape
from one endtto the, other with the
portions on` the major
opposed hangers rig-`
idly connecting the upper end of the/skirt to the
upper end of said skirt atÍall .points except at
head on the Vminor axis of the ellipse of the skirt.
ton adjacent .the »lower ends of sait'l'> hangers 'with
the'remainder of the upper wall portion of said
and two spaced apart struts having 'a 'lower co
eiiicient of ‘expansion thanv said 'skirt and di»
>said hangers whereby said head is i'reeto expand the skirt ,being separated from the head vbetween
.and contract in a uniform manner and without rthe hangers, piston pin `bosses within the' skirt
distortion, piston pin bosses formed on said pis~. ' and on the minor axis’of the kellipse of the mrt.
" posed Hwithin'said skirt'below and-spaced from
kßk‘li'l: ’free and ‘ unrestrained
.whereby expansion
and contraction‘movements of said‘head acuate » said pin bosses, and substantially parallel tothe
seid 'hangers to-expandzand contract said skirt major axis of said ellipse.'v the struts being inf
along the'minor axisïof its el1ipse’to~.produce, ilexible and the. bearing face'portions between
uponl expansion, a -substantially circular skirt the ends of the struts being ¿dexible whereby said4
and, upon contraction, an ‘elliptical skirt, ,and a ~ lbearing face portions tend Vto'tiatten out during
pair of struts each formed of la material having a. y 'rthermal expansion of ythepiston ùirt and the
mulch lower .coeiiicien y,of expansionl than- said length vof the minor axis of the'skirt increases.r
6. A piston comprising "a head,~rigid hangers
70 skirt and disposed within said skirt »below said
pin bosses and parallel to themajor axis/of the depending lfrom said ,head` yand carrying pin 70
ellipse of said'skirt with their ends l integrally vskirtv directly connected to
secured inthe wall of said skirt at points sub, stantially spaced apart whereby the skirt ma'
"terial between adjacent ends of said struts is free
bosses,v all formed of a metal
a high
and co
efficient of expansion; said head and skirt being
txiailyspacea from each other throughout theirl 75
entire circumference by a circumferentially ex
tending air gap and being maintained in such
relation by said rigid hangers. the entire exterior
surface of said skirt being generally elliptical in
contour with the minor axis thereof substantial
ly parallel to the axis Iof said pin bosses and the
continuity of said skirt being' interrupted only
by the pin boss aperturea‘and a pair of rigid
struts having a lower coemcient. of expansion
than that of the metal of said skirt disposed be
low and spaced from said pin bosses, the ends of l
said struts being embedded in the metal of said 5
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