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Nov.v 19, 1946.
_
J. H. PRATT
2,411,229
SEALING MEANS FOR PISTON SUBJECTTO FLUID PRESSURE
Filed June 5, 1945
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2 Sheets-Sheet 1
Nov. 19, 1946.
2,411,229
J. H. PRATT
SEALING MEANS FOR PISTON SUBJECT TO FLUID PRESSURE
Fi1__ed June 5, 1945
2 Sheets-Sheet 2
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2,411,229
Patented Nov. 19, 1946‘
UNITED STATES-9 PATENT OFFICE
_ SEALING MEANS FOR PISTONS SUBJECT
TO FLUID PRESSURE
James Henry Pratt, Birmingham, England
Application June 5, 1945, Serial No. 597,676
In Great Britain June 22, 1944
' 6 Claims. (01. 309-4)
1
2
,
This invention has reference to improvements
in sealing means for pistons subject to ?uid pres
sure and has for its object to provide a sealing
means which for all practical purposes is leak
the piston 5 and the front end of the sealing
proof, which entails less wear on the resilient v
pressible piston rings;
cup 8; The periphery of the piston 6 is furnished a
with a plurality of grooves 61) and if preferred
provision may be made for the ?tment of com
.
element of the sealing means and which is readily
In use any liquid passing between the piston
adaptable to ?uid pressure piston and cylinder
6 and the wall of the cylinder 1 leaks into the
annular space 9 between the rear end or the
piston 6 and the forward end of the sealing cup
10 8 and the displaced air is caused to accumulate in
mechanisms without involving any material
changes in the normal construction of. such
mechanisms.
-
.
the annular re-entrant groove 6a in the rear end
of the piston 5 so that when the liquid in the an
nular space 9 comes under pressure on an acting
stroke of the piston 6 the air trapped in the an- ‘
to the rear of the acting face of a piston is asso
elated with a space within which is trapped and 15 nular re-entrant groove Ba is compressed and
Accordingly the invention consists of an im
proved sealing means for pistons subject to ?uid
pressure in which a resilient sealing means located
caused to react through the liquid column in the
compressed air which may be further compressed
by ?uid passing betweenlthe piston and the wall
of a substantially vertically arranged cylinder and
annular space 9 on the lips of the sealing cup 8
thus effecting an e?ective leak proof seal without
entailing the pressure and the consequent degree
which on compression reacts‘ on the resilient
sealing means to effect a leak proof seal with a 20 of wear of the sealing cup 8 which obtains in
the more usual system in which the lips of the pressure which is less than that built up on the
sealing cup are forced into sealing contact by a
acting face of the piston with a consequential
relatively incompressible liquid column and since
reduction in the wear of the sealing surface of
the pressure of the liquid in the annular space 9 i
the said resilient sealing means.
The invention will now he described with par 26 will not attain to that built‘ up on the acting
face of the piston 6 on a pressure stroke as liquid
ticular reference to the accompanying drawings
cannot leak past the piston 6 at a rate com
wherein
mensurate with the relatively rapid displacement
Figure 1 is a fragmentary sectional view of the
of the piston 6 which takes place on the initiationv
invention as embodied in a master cylinder unit
_
‘
such as is employed in conjunction with hydrau 30 of an acting stroke. 7
Describing now the invention as applied to a
lically actuated mechanisms.
Figure 21s a sectional View of the invention as -
embodied in a pneumatic suspension means for
vehicles and
'
pneumatic suspension means for vehicles as illus
trated in Figure 2 using where desirable the refer
ence numerals employed in conjunction with the
Figure 3 is a fragmentary view illustrating a 35 description of‘Figure 1 to denote analogous parts:
The frame of a vehicle (not shown) is pivotally
modi?cation of the invention as illustrated in
Figures 1 and 2.
connected to ‘a lug Illa carried at the upper end
‘
of a'vertically arranged cylinder 10 within which
Describing ?rst the embodiment of the inven
tion as illustrated in Figure 1 a plunger ii to
is disposed a plunger 4 the under portion of which
which the operational effort is applied by way of
.40 has a ball and socket association with "the upper
the rod 5 has mounted on a shouldered portion 4a
thereof a piston 6 which is a close working ?t in
the bore of the vertically arranged master cylin°~
der], said shouideredportion la being of lesser
di’i'meter than the bore of the cylinder '1. This
piston B is formed in the end thereof opposite to
the acting face with an annular re-entrant
groove 6a which is disposed oppositely to the re- ‘
end of a piston rod II the lower end of which in;
turn has a ball and socket association with a
bracket l:2 carried by an axle of a vehicle.
- The bore of the cylinder Ill is of two-diameters
with the bore of the upper portion of the greater
diameter. At the junction of the bores there is
disposed a solid partition’ wall l3 having in the
centre thereof a vertically drilled -hole within
which is screwed a vertical tubular housing II
entrant gap?a in a resilient sealing cup 8 of the
normal U-shape in cross section, said sealing cup 60 which is provided with a seating fora one way
ball valve Iii, said ball valve l5 having an opening
8 abutting a ?ange lb formed at the rear end of
movement towards the closed end of the cylinder
the plunger 4 with the plane containing the for
in the degree of which however is restrained by a‘
ward rim of the sealing cup 8 spaced from the
' transverse peg lid.
rear end of the piston‘ 5 ‘so that an annular
chamber 9 is formed between the rear end of 55 The partition, 13 is provided with a lateral bore
2,411,229
.
from the outside of the cylinder III.
A
n
4
-
,
space 9 comes under pressure on an acting stroke
l3a within which is disposed a needle valve‘ l8
which tends to remain continually 011 its seating
l3b under the in?uence of a compression spring
II the degree of compression of which may be
adjusted by means of a screw plug is accessible
of the piston 6 the air trapped in the annular
re-entrant groove 6a is compressed and caused
to react through the accumulated oil on the lips
of the annular sealing cup 8-,,thus effecting an"
effective leak proof seal without entailing‘ the
'
The seating I31) for this needle valve I6 is
pressure and the consequent degree of wear of v
the sealing cup which. obtains in the more usual _7
‘system as has been referred to hereinbefore.
in the tubula-rhousing I 4 below the ‘seating _for
the ball valve l5 and the partition i3 is formed 10 - It will be appreciated that academically the
same e?'ect will be attained by the use of a com
with a hole 530 which places the upper part of
formed adjacent to the end of a passage Na
the cylinder it in communication with the lateral
bore I 31: within'which the needle valve is contained.
pressed gas alone although in most applications
- it will generally be necessary to usev a lubricant.
Further, it will. be appreciated that if desired
'
Thus there is always a permanently open leak 15 the adjustable needle valve l6 may be dispensed . ‘
with and a simple leak passage employed.
. passage between the upper and lower portions
of the cylinder iii.
In the modi?cation illustrated‘ in Figure 3 the '
plunger 2| is a working ?t in the complementary
Secured to the side of the upper portion of» the
master cylinder 22 and may move through a
cylinder i ii is an in?ation valve is byway of
which air may be compressed initially in the 20 stationary resilient sealing cup 23 of U-shape in a
upper portion of the cylinder and subsequently
cross section which is located in an enlarged
cylindrical section 2212 adjacent to the. outer end
of the master cylinder 22 the re-entrant gap 23a
The piston plunger 4 (as is illustratedalso in
.Figure 1) is of a stepped formation with a
in the sealing cup 23 being located opposite an
, shouldered portion 13a of lesser diameter than the 25 annular re-entrant groove 22b formed in the presented end of the enlarged section 220: with an
lower bore of the cylinder at the acting end. and
annular space 24 between the plane containing
an annular ?ange db‘ of substantially the same
replenished.
'
,
_
v
'
the forward rim of the sealing cup 23 and the
presented end of the enlarged section 220. The
diameter as the said bore at the opposite end.
Mounted on ‘the shouldered portion ta, is a
‘piston 6 which is a close'working ?t in’. the lower 30 sealing cup 23 abuts the upper face of an annular .
‘portion of the cylinder ill and which is formed in - screwed closure member 25 which closes the lower 7
the end thereof opposite to the acting face with
end of the enlarged section.
- This re
In this embodiment of 'the invention also'liquid
entrant groove 5a is disposed oppositely to the re
leaking between the plunger 2| and the wall of
an annular rte-entrant
groove =6a.
entrant gap 8min a resilient annular sealing cup 35 the cylinder 22 accumulates in the annular space
8 of the normal U-shape in cross section, said
2d‘, and traps the‘ displaced air in the annular
sealing cup 8 which conveniently is made of I re-entrant groove 22b so that this air is com
synthetic rubber or of a rubber like plastic being
pressed on an acting stroke and caused to react
disposed around the intermediate portion of
through the liquid column in ‘the’ annular space
the plunger 1i and in abutment with the annular
25 to force the lips of the sealing cup 23 into seal
?ange lib at the lower end thereof. Theannular “ ing contact with the plunger 2! and with the wall
sealing cup t is of a depth such that the plane
of the enlarged section 22a again without sub
containing the forward rim of the sealing cup a is .
jecting the sealing cup 23 to the pressure and
spaced from the rear end of the piston head so
consequent wear incidental to the normal prac
tice in which the sealing cup 23 is ' expanded
that an annular chamber 9 is formed between the
into sealing contact by a relatively non-compres
rear end or the piston 6 and the adjacent end of
the sealing cup 8.
1
-
sible liquid column.
_
The periphery of the piston b is formed with a
A plurality of'shallow groovest’b in which lubricant
may collect.
>
-
The lower portion of the cylinder it and the
projecting portion of therpiston rod H and its
lower ball and socket mounting are enclosed by
This embodiment of the invention can ‘be
adapted also to a pneumatic suspension'system
50 as described with reference to Figure 2.
I
V
Iclaim:
.
.
l
n l. Sealing means for pistons comprising ‘a
substantially vertically arranged cylinder, a pis
a bellows 20. one end of which is secured t6 the
- ton i’or reciprocation within said cylinder, a
periphery of the power portion of the wall of ‘the 55 resilient sealing meanshaving a space withinits
cylinder l0, whereas the other end is secured to
body and located to the rear of'the acting face
the bracket 52.
of the piston and a space open to the cylinder '
-
-
-
-'
\A supply of lubricating oil is charged into the
cylinder Ill and this tends to collect in- a shallow
column 2 I > on top of the piston 6.
'
> and partially bounded by the said resilient means
and in communication with the space within the
60 body of said resilient means and into which any
In operation, ‘when the piston 6 moves up
?uid leaking past the ‘piston can accumulatean'd
wardly the ball valve I5 is lifted off its seat and
e?'ect a compression of air within the space which
further compression of air takes place in the
is caused to react on the resilient sealing means
upper portion of the cylinder ill, and upon a
to effect a leak proof seal by expanding the said
downward movement the pressure thus generated 65 .resilient means tightly against the inner ‘wall of
is dissipated at‘ a controlled rate of way of the
said cylinder with a pressure which is less than
hole I30, bore i312 and the needle valve controlled
leak passage I la.
that built, up on the acting face vof the piston.
_
2. Sealing means for pistons comprising a
‘ Any-tendency to leakage around the piston
substantially vertically arranged cylinder, a~
6 causes lubricating oil to pass into the annular 70 piston for reciprocation within said cylinder, a
space‘ 8 between the‘ rear end of the piston 8
resilient ‘sealing means incorporating a re-en
and the adjacent end of the sealing cup 8 and
the displaced ‘air is caused to accumulate in the
trant groove located to the rear of the acting
face of the piston, a complementary re-entrant
annular re-entrant groove 6a in the rear end
groove oppositely disposed to the re-entrant
"of the piston 6 so that when the oil in the annular 75 ‘groove 01' the resilient sealingmeans and a v _
2,411,229
6
,,
.
space which is open ‘both to the said re-entrant
grooves and to the cylinder and into which any
?uid leaking past the piston can accumulate and
effect a compression of the air which becomes
lent sealing means which effects a leak proof
seal with a pressure which is less than that built
up on the acting .face of the piston.
trapped in the re-entrant groove at'the rear of
substantially vertically arranged cylinder, a
plunger for reciprocation within said cylinder
the acting face of the piston and which entails
a reaction in the re-‘entrant, groove of the resil
ient sealing‘ means which effects a leak proof
5. Sealing means for pistons comprising a ~
and having at its rear end a ?ange'which is a
working fit within the cylinder, a piston mount
ed on the forward end of the plunger which is a
10 close working fit within the cylinder, a re-en
up on the acting face of the piston.
trant groove in the rear end of the piston, a
3. Sealing means for pistons comprising a
substantially vertically arranged cylinder. a
resilient sealing means which is in abutment
with the said ?ange and which has a re-entrant
piston for reciprocation within said cylinder, a
groove which is oppositely disposed relatively to
resilient sealing means having a re-entrant
groove and which is movable with the piston and 15 the re-entrant groove in the rear end of the
seal with a pressure which is less than that built
which is located to the rear of the acting face
of the piston, a complementary re-entrant
groove in the rear end of the piston which is
oppositely disposed relatively to the re-entrant
piston and a ‘space between the rear end of the .
piston and the resilient sealing means which is ,
open to both the re-entrant grooves and to the
cylinder and into which any ?uid leaking past
groove of the resilient sealing means and a space 20 the piston‘can accumulate and effect a com
pression of the air which becomes trapped in the
which is open both to the re-entrant grooves
re-entrant groove at the rear of the acting face
and to the cylinder and into which any ?uid
of they piston and which entails a reaction in
leaking past the piston can accumulate and
the re-entrant groove of the resilient sealing
effect a compression of the air which becomes
trapped in the re-entrant groove at the rear 25 means which effects a leak proof seal with a
pressure which is less than that built upon the
of the acting face_of the piston and which en-,
acting .face of the piston.
tails a reaction in the re-entrant groove of the
6. Sealing means for pistons comprising’ a
resilient sealing means which effects a leak
substantially vertically arranged cylinder, a
proof seal with a pressure which is less thanv
30 plunger for reciprocation within said cylinder,
that built up on the acting face of the piston.
an enlarged space located at the lower end of
4. Sealing means for pistons comprising a
the cylinder, a stationary resilient sealing means
substantially vertically arranged cylinder, a
which surroundsthe plunger and which has a
piston for reciprocation within said cylinder. a
re-entrant groove and which is located in the
stationary resilient means which is located to
the rear of the acting face of the piston and 35 bottom of the said enlarged space and a sta
tionary ‘re-entrant groove which is oppositely
which has a re-entrant groove, a complementary
disposed relatively to the .re-entrant groove of
stationary re-entrant groove which is‘oppositely
the resilient means so that any fluid leaking past
disposed relatively to the re-entrant groove of
the plunger can accumulate in the said space and
the resilientsealin'g means and a space which is
open both to the re-entrant grooves ‘and to the 40 effect a compression of air within the space ‘
which is caused to react on the resilient sealing
cylinder and into which any ?uid leaking past
means to e?ect a leak proof seal with a pressure
the piston can accumulate and effect a com
pression of the air which becomes trapped in the ' p which is less than that built up on the acting
face of the piston.
re-entrant groove adjacent to the rear of the
acting face of the piston and which entails a ‘5 k
reaction in the re-entrant groove of the resil
it
JAMES HENRY PRA'I'I‘.
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