Note: Descriptions are shown in the official language in which they were submitted.
BACKGROUND OF THE INVENTION
The present invention is related to hydro-pneumatic
brake cylinder devices for vehicles requiring a spring-applied
parking brake function.
The recognized advantage of a spring-applied parking
brake is its ability to provide a hydro-pneumatic brake unit
with an effective bra~e force over an extended period of time,
thus alleviating loss of braking due to dissipation of pneumatic
pressure. Consequently, spring-applied brakes are typically
employed in conventional air brake systems either ~or parking
brake purposes or as an auxiliary back-up type emergency brake.
~lowever, in combining the air and spring-applied brakes, the
latter has been installed as a separate structure so that the
combined braking apparatus is complicated by extensive lever
arrangements between the separate st.ructures and re~uires
considerable space.
SUMMARY OF THE INVENTION
The object of the present invention is to provi~e a
; ~ ~ hydro-pneumatic brake cylinder device that incorporates a springbrake in a unitary structure to obtain a simplified compact
brake apparatus.
Briefly, this objective is achieved by providin~ a
brake cylinder device comprising:
(a) a pneumatic cylinder portion;
(b~ an annular sleeve disposed within said pneumatic
cylinder portion, said sleeve having at one end thereof an
outturned flange in an abutting relationship with one end wall
thereof, and forming an annular space between the adjacent
cylindrical walls of said pneumatic cylinder portion and said
sleeve;
(c) a primary piston movably disposed within said
pneumatic cylinder portion independently of said sleeve and
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forming in conjunction with an end wall of said cylinder
opposite said one end wall and with the cylindrical surface of
said cylinder a first pressure chamber in which fluid pressure
acts on said primary piston in a brake release direction;
(d) a secondary piston movably disposed within said
sleeve and forming in conjunction with said one end wall and
said sleeve a second pressure chamber in which fluid pressure
acts on said secondary piston in a brake application direction;
(e) a piston rod on said secondary piston projecting
through a bore in said primary piston to permit movement of said
secondary piston in said brake application direction independent
; of said primary piston;
(~) a stop on said piston rod;
(g) a first spring disposed in said annular space
between said flange and said primary piston to exert a force on
said primary piston to effect movement thereof into engagement
with said stop to accordingly move said piston rod in said brake `
application direction in the absence of fluid pressure in said
:~ first pressure chamber; `~
(h) a h~draulic cylinder in which said piston rod ~;
is movably disposed; and ~-
(i) hydraulic brake means to which hydraulic fluid
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is connected from said hydraulic cylinder to said hydraulic
brake unit, when said piston rod is moved in said brake applica-
tion direction, ~or effecting a brake application.
Engagement of the primary piston with the stop member
actuates the piston rod in the hydraulic cylinder, thus convert
ing the spring-applied force into hydraulic pressure to operate
a typical hydraulic brake unit. Similarly, pneumatic pressure `~
acting on the secondary piston actuates the piston rod indepen-
dently of the primary piston to convert the pneumatic pressure
into hydraulic brake PXessure~
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BRIEF DESCRIPTION OF THE DRAWINGS
In the following more detailed description of the
invention, reference may be made to the accompanying drawings in
which:
Figure 1 is a sectional assembly view of the brake
cylinder device of the invention with the hydro-pneumatic and
spring-applied brake components shown in their release position;
Figure 2 is a similar view in which the spring-applied
brake components are shown in their release position and the
hydro-pneumatic brake components are shown in thelr actuated .
position; and ::
Figure 3 is a similar view with the hydro-pneumatic
brake components shown in their release position and the spring~
applied brake components shown in their applied position.
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DESCRIPTIO~ ~D OPERATIO~
Referring now to tha drawings, there is shown a cylin-
drical brake cylindex body comprisln~ a pneumatic cylinder
portion 1 and a hydraulic cylinder portisn 2. Pneumatic
portion 1 compri6es a primary cylinder portion 4 having a
primary piston 3, and a secondary cylinder portion 7 having
a secondary pi5ton 5 and a piston rod 6 that is integral with
piston 5. A spring 8 iB arranged between the brake cylinder
body and primary.piston 3 to urge the piston in the direction
of the righ~ hand in opposition to the æluid pr~sAure fvrce . -
exerted on the piston by pneumatic preCsure in a chamber 9
formed by piston 3 and primary~cylinder portion 4. This
pneumatic pressure effective at chamber 9 is supplied and
released via a pipe 10.
Forming the secondary ~ylinder portion 7 is an annular
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: sleeve 11 arranged within spring 8 to receive secondary piston
5. Piston rod 6 passe3 through a bore in primary piston 3
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~; and passes ~hrough chamber 9 into hydraulic cylinder portion
2. Disposed b2~ween secondary piston 5 and primary piston 3
:`: 20 is a return spring 12 that actæ on piston 5 in the direction
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o~ the let hand in opposition to the force of ~luid pressure
ef~ective in a chamber 13 formed by the piston 5 and secondary
cylinder poxtion 7. This pneumatic preæsure ef~ective at
: chamber 13 i~ supplied and released via a pipe 14.
A sto~ member 15 is formed on piston rod 6 on the right~
hand side o~ piston 3, ~o as to be engaged thereby when piston
3 is actuated rightwardly. Extending into chamber 9 from the
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side wall of the brake cylinder body are projections 16, which
sexve to limit rightward movement of piston 3. Leftward move-
ment of piston 3 is limited by engagement with the end of
annular sleeve 11.
~ydxaulic portion 2 comprises a hydraulic re~ervoir 17
and a hydraulic cylinder 18 into which the end of piston rod
6 is inserted for rec~procation therein. A passage 19 is
provided between reservoir 17 and cylinder 18 to supply
hydraulic fluid from the reservoir to cylinder 18 when piston
rod 6 is in its leftward-mosk position. A hyclraulic brake
apparatus 20, as for example a conventional disc brake unit,
comprises a hydraulic brake cylinder 21 to which a pipe 22 is
connected from hydraulic cylinder 18, a return spring 23
between a pair of brake tongs 24 t:hat are connected, respec-
tively, to cylinder 21 and to a piston o~ the cylinder 21.
Di~c brake pads 25 are connected t:o the ends of tongs 24 for
engagement with a brake disc 26.
In the case o~ Fi~. 1, L~ which both the hydro-pneumatic
and spring-applied brake components are released, pneumatic
pre~sure is supplied to chamber 9 via pipe lQ, while chamber
13 is vented ~ia pipe 14. The pneumatic pressure pxesent in
cha~ber 9 is ~ffective to force piston 3 left~ard against
spring 3 until its movement is ~topped by engagement with the
end of sleeve 11. This mo~ement of piston 3 compresses return
spring 12, which is effective in the absence of pneumatic
pressure in chamber 13, to force piston 5 to its leftward-most
position corresponding to brake release position of piston rod
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6O In this position of piston rod 6, the hydraulic fluid is
drawn from brake cylinder 21 to cylinder 18 via pipe 22, thus
allowing return ~pri~g 23 to contract brake cylinder 21 and
thereby expand brake pad~ 25 out of braking engagement with
disc 26 via tongs 24. Ac~ordingly, the brake is released.
In the ca~e of Fig. 2, the hydro-pneumatic brake com-
ponents are applied by supplying pneumatic pressure to chamber
13 via pipe 14 ~uf~icient to actuate piston 5 against the
force exerted by return spring 12. Accordingly, piston rod 6
is foxced into hydraulic cylinder 18, closing passage 19~ and
thereby transmitting hydraulic fluid under pressure to brake
cylinder 21 to overcome spring 23 and force braka pads 2S into
brake engagement with disc 26 via brake tongs 24 to apply the
brake. During this rightward mov,ement of pi~ton 5, push rod
6 move3 through the bore in pi ton 3, which remains stationary
in its release position against the end of sleeve 11. In
order to subse~uently release this brake application~ the
pneumatic pressure in chamber 13 is relea6ed via pipe 14, so
that piston 5 is able to be moved leftward by return spring 12,
~ 20 and at the same time retract push rod 6 in cylinder 18 to with-
::; draw hydraulic ~luid from brake cylinder 21 and all~w spring23 to rotate tongs 24, so that brake pads 25 are moved out of
engagement with brake di~c 26 to rlease the brake.
In the event the brake is to be applied for an extended
: 25 duration, as when parking the ~ehicle, the pneumatic pressure ::
in chamber 9 is released via pipe 10, thus allowing spring 8
to actuate primary pi~ton 3 in a rightward direction. As
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pi~ton 3 moves righ~ward~ it engages 6top 15 on push rod 6 to
pull the push rod in a righ~ward direction, al~o. As piston
rod 6 move~ right~ard, pa6~ge 19 in cylinder 18 is covexed
to effect the buildup o~ hydraulic pr~sure in cylinder 18.
Thi~ hydraulic pressure is tran~mitted to brake ~ylinder 21
via pipe 22, ~uch that brake tongs 24 mDve brake pads 25 into
engagement with brake disc 26 to apply the brake. In order to
sub~equently relea~e this ~pring-applied parking brake, pneu-
matic pre~ure is restored to chamber 9 via pipe 10 to force
piston 3 l~ftward against the forca of spring 8. Concurrently,
the secondary pi~on 5 is al90 moved leftward by the action of
; its return spring 12, to in turn move piston rod 6 leftward.
As piston rod 6 is xetracted in cylinder 18, hydraulic fluid
is drawn from braXe ylinder 21 via pipe 22, to allow spring
23 to operate brake tongs 24 ln a direction to move brake pads
25 out of engagement with brake disc 26 to relea~e the brake.
From the oregoing, it will now be apparent that the brake
; cylinder device of the present invention operates, in the case
of a hydro-pneumatic braka, by supplying pneumatic pressure to
~econda~y piston 5 to actuate piston rod 6, and m the case of
a ~pring-applied brake, k~ di charging pneumatic pressuxe from
primary piston 3 to allow spring 8 to actuate piston 3j which
: in turn actuates push rod 6 through stop 15. Consequently,
piston rod 6 is actuated, in the case o either a h~dro-
pneumatic or a spring-applied brake, to generate hydraulic
pressure in cylinder 18 for operating the hy~raulic brake
apparatus 70. .
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Moreover, the ~rake cylindex device of the present inven-
tion i8 adapted for reduction i~,~ize and lends itself to a
æimplified brake arrangement, by rea60n of unifying its hydro-
pneumatic and spring-applied brake unc~ions to eliminate
complex lever arrangements.
