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Патент USA US3072460

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Jan. 8, 1963
Filed Jan. 12, 1959
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United States Patent O?ice
Patented Jan. 8, 1963'
"In further accord with conventional practice, wheel cyl
Carroll D. Hobson, Goshen, Ind., assignor to Goshen
Rubber co, Inc, Gosheu, Indi, a corporation of- In
Filed Jan. 12, 19589, Ser. No. 786,229
2 Claims. (Cl. 309-53)
This invention relates generally to hydraulic piston cups
inder 18 encloses the hydraulic pistons 22 which are con.
nected to the linkages 24, piston return spring 26 pro
viding proper'bias‘ to the pistons 22. In order to seal
off the hydraulic chamber de?ned between the pistons
22, piston cups 28 are disposed between return spring 26
and the pistons 22.
As is better shown in FIGS. 2' and 5, hydraulic piston
cup 28 is comprised of a plate or disc portion 28a which
and more particularly to piston cups for use in the hy 10 closes off one end of the throat portion 28b. The open
draulic brakes of automobiles.
end of throat‘ portion 28b‘ terminates in a rounded, or
Heretofore, hydraulic piston cups have been provided
more speci?cally a toroidal sealing portion 280. Plate
with a sharp feather-edge which prevents hydraulic ?uid
28a is. preferably rigid while the- throat portion‘ 28b and
from escaping. between the piston: a‘ndits cylinder; Ac
the sealing portion 28c are‘ desirably somewhat ?exible
cording to conventional. practice, this feather-edge is 15 in order that the portion 280 may elongate to its own
formed by grinding or machining. the previously molded
longitudinal axis or dilate into uniform and intimate
piston cup. The. resulting. structure has‘proved dif?cult
contact with the internal surface of cylinder 18. The
to insert into the hydraulic cylinder; and more impor
desirable characteristics "of the'several portions of cup
tantly, any inaccuraciesv in, the .grinding or machining
.28‘ have advantageously been obtained by molding the
operation result. in. cuts or. serrations along the feather 20 cup 28 from a suitable‘ rubber compound.
edge, which‘ cuts .or serrations are permissive‘ of ?uid
According to an important feature of the invention,
leakage. Furthermore, these prior art piston cups can
the sealing portion 280 displays a substantially circular
be predisposed to failure by rough_handling,,nicks or
cross section. This contour plus the requisite ability to
other like damage to the feather-edgemaking the cups
deform under mild pressure enables the piston cup of the
susceptible to leakage.
25 present invention to provide a relatively large sealing sur
Therefore, a general object of the present invention is
face in contact with the cylinder 18. This combination of
to provide an improved hydraulic piston cup.
attributes also tends to minimize any leakage difficulties
Another object of the present invention is to provide a
which might arise due to small cuts or imperfections in
molded hydraulic piston cup which requires no grinding
the outer surface of the sealing portion 280.
or machining of the sealing surface.
Although sealing portion 28c is inherently capable of
Yet another object of the invention is to provide a
compensating for small imperfections, it is advantageous
hydraulic piston cup having increased contact area at the
to manufacture cup 28 so as to eliminate, insofar as
sealing surface.
possible, any hazards to its successful functioning. For
A further object of the invention is to provide a hy
example, when the piston cup of the invention is molded,
draulic piston cup which is easier to assemble and which
the molding dies are desirably arranged to dispose the
has a longer use-life.
?ash away from the primary sealing surface of sealing
A still further object of the present invention is to
portion 280. FIG. 3 shows ?ash 30 located in such an
provide a hydraulic piston cup which is resistant to failure
unobtrusive location.
resulting from nicking the sealing surface.
One embodiment of mold apparatus suitable for pro
Additional objects and features of 'the invention per 40 ducing piston cups having suitably disposed ?ash is
tain to the particular structure and arrangements where
shown in FIG. 4. The compression mold apparatus
by the above objects are attained.
The structure in accordance with the invention includes
' a piston cup having a disc portion, a ?rst annular portion
of substantial circular cross section, and a second an
nular portion ?exibly connecting the disc portion and
the ?rst annular portion.
The invention, bothto its structure and mode of op
shown generally at 32 includes a plunger 34 which co
operates with a base 36 in de?ning a mold cavity 38.
As shown, plunger 34 and base 36 have tapering sides
which facilitate disposition of the mold parting lines at
unobtrusive locations on the molded article.
tageously, base 36 may be provided with a ?ash groove 40.
According to conventional modes, depressing the brake
eration, will be better understood by reference to the
pedal forces ?uid out of the master cylinder. This ?uid
following disclosure and drawings forming a part thereof, 50 flows through the hydraulic line 20 to the wheel cylinder
18 forcing the pistons 22 outwardly and expanding the
lFIG. 1 is a schematic view in partial section of an
shoes 14 against drum 12 in order to a?t'ect braking.
automotive brake assembly incorporating hydraulic pis
Releasing the brake pedal affects a return of ?uid from
ton cups in accordance with the present invention;
‘ the wheel cylinder 18 to the master cylinder. The brake
FIG. 2 is an enlarged, fragmentary view showing the 55 shoe return springs 16' force the wheel cylinder pistons 22
piston and the piston cup;
to return to the release position, thereby forcing ?uid out
FIG. 3 is a fragmentary view insection of a piston
of the wheel cylinder. The check valve of the master
cup in accordance with the invention illustrating the ?ash
cylinder closes when the pressure in line 20 is reduced to
incurred during molding;
a small positive value. This minimum positive pressure
FIG. 4 is a sectional view of the molding apparatus
acts against the throat portion 28b and the sealing portion
for producing piston cups in accordance with the present 60 280 to dilate the portion 280 against the wheel cylinder
invention; and
FIG. 5 is a perspective view of the piston cup of the
Referring now in detail to the drawings and speci?cally
18. Thus, cup 28 is prevented from leaking hydraulic
?uid and the hydraulic system is sealed against the pos
sibility of air entering therein. Of course, when the
65 brakes are being applied, the additional pressure in the
to FIG. 1, there is generally shown an automotive wheel
system encourages cup 28 to form an even tighter seal.
brake assembly 10 including a brake drum 12, a brake
Although the art of automotive wheel brake assem
shoe 14, brake shoe return springs 16, a wheel cylinder
has been used for purposes of explanation and il
18 and a hydraulic line 20 communicating with the master
lustration, it should be noted that the construction of
cylinder of the hydraulic brake system. Since these cle—
ments comprise no part of the present invention, they will 70 .the piston cup of the invention is useful for master cyl
inder piston cups and other hydraulicpiston cups as well.
not be described in detail.
It will be understood, therefore, that the invention is not
limited to the particular embodiment described since many
modi?cations may be made.
and having a substantial extent between said sealing
portion and said disk portion for enabling said sealing
Consequently, it is contem
portion to respond to the pressure of said ?uid by elon
gating relative to its own longitudinal axis whereby ag
gressively and deformably to engage the walls of said
bore to seal said ?uid from escape into the region of said
plated to cover by the appended claims any such modi
?cations as fall within the true spirit and scope of the
The invention is claimed as follows:
1. A piston cup of elastomeric material adapted to
form a ?uid seal in a cylindrical bore, said cup compris
ing: a disk portion adapted to abut a piston operative in
said bore and having a diameter which is smaller than
the diameter of said bore whereby said'disk portion is
spaced apart from the walls thereof; a resiliently de
2. A piston cup according to claim 1 wherein said
sealing portion confronts the walls of said bore with a
molded surface and wherein said sealing portion exhibits
?ash extending outwardly therefrom in a position gen
erally oppositely from said annular throat portion and
out of contactable relationship with the walls of said bore.
formable, toroidal sealing portion spaced apart from said
disk portion in a direction away from said piston, said 15
sealing portion having an outside diameter normally ap
proximating the diameter of said bore; and a ?exible, an
nular throat portion spaced apart from the walls of said
vbore and disposed between said disk portion and said
sealing portion in integrally interconnecting relationship
therewith, said throat portion and said sealing portion
cooperating with said disk portion in de?ning a cavity
for receiving and retaining ?uid, said throat portion ?ex
ibly connecting said sealing portion to said disk portion
References Cited in the ?le of this patent
20 2,336,578
Gottlieb ____________ __ Mar. 31,
Waterbury __________ __ June 8,
Skoning _____________ __ Dec. 14,
Dick _______________ _._ Sept. 4,
Dick _______________ __ July 22,
Martin _____________ __ May 24,
Youngv ______________ .__ Dec. 10,
Jernander ___________ _._ June 21,
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