Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Reexamination Certificate
2002-04-26
2003-10-28
Schwartz, Christophaer P. (Department: 3683)
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
Reexamination Certificate
active
06637838
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic booster for use in a brake system of a vehicle.
A tandem pneumatic booster, for example, has a structure as shown in FIG.
6
. The pneumatic booster has a shell body
3
comprising a front shell
1
and a rear shell
2
. The interior of the shell body
3
is divided by a center shell
4
into two chambers, i.e., a front chamber and a rear chamber. The two chambers divided by the center shell
4
are further divided. That is, the front chamber is divided by a power piston
7
having a diaphragm
5
into a constant-pressure chamber
9
, in which a negative pressure is to be introduced, and a variable-pressure chamber
11
, in which atmospheric air is to be introduced. Similarly, the rear chamber is divided by a power piston
8
having a diaphragm
6
into a constant-pressure chamber
10
, in which a negative pressure is to be introduced, and a variable-pressure chamber
12
, in which atmospheric air is to be introduced. The power pistons
7
and
8
are provided with a mutual valve body
13
. The valve body
13
extends air-tightly and slidably through a central portion of the center shell
4
and through a reduced-diameter cylindrical portion
2
a
projecting from the rear of the rear shell
2
. The valve body
13
contains a valve mechanism (not shown). The valve mechanism is operated through an input rod
14
movable in response to the actuation of a brake pedal to produce differential pressures between the constant-pressure chambers
9
and
10
on the one hand and the variable-pressure chambers
11
and
12
on the other. The differential pressures propel the front and rear power pistons
7
and
8
. Thus, a boosted thrust is transmitted to a master cylinder (not shown) through an output rod
15
.
In this type of pneumatic booster, the front shell
1
has a cylindrical portion
1
a
extending rearward to a considerable extent. The outer peripheral edge of the rear shell
2
is joined to an opening edge
1
b
of a cylindrical portion
1
a
of the front shell
1
, and these edges are united together, for example, by caulking to form the shell body
3
. In the above-described tandem pneumatic booster, the center shell
4
also has a cylindrical portion
4
a
extending rearward to a relatively large extent. The opening edge
4
b
of the cylindrical portion
4
a
of the center shell
4
is disposed in the joint between the front shell
1
and the rear shell
2
. Of the two diaphragms
5
and
6
constituting the power pistons
7
and
8
, the rear diaphragm
6
has an outer peripheral bead
6
a
thereof also disposed in the joint between the front and rear shells
1
and
2
. It should be noted that the front diaphragm
5
is supported by the shell body
3
in a state where an outer peripheral bead
5
a
of the diaphragm
5
is disposed between a step portion
1
c
provided on an intermediate part of the cylindrical portion
1
a
of the front shell
1
and a shoulder portion
4
c
at the proximal end of the cylindrical portion
4
a
of the center shell
4
.
In this type of pneumatic booster, the front shell
1
has a cylindrical portion la extending rearward to a considerable extent. The outer peripheral edge of the rear shell
2
is joined to the opening edge
1
b
of the cylindrical portion
1
a
of the front shell
1
, and these edges are united together, for example, by caulking to form the shell body
3
. In the above-described tandem pneumatic booster, the center shell
4
also has a cylindrical portion
4
a
extending rearward to a relatively large extent. The opening edge
4
b
of the cylindrical portion
4
a
of the center shell
4
is disposed in the joint between the front shell
1
and the rear shell
2
. Of the two diaphragms
5
and
6
constituting the power pistons
7
and
8
, the rear diaphragm
6
has an outer peripheral bead
6
a
thereof also disposed in the joint between the front and rear shells
1
and
2
. It should be noted that the front diaphragm
5
is supported by the shell body
3
in a state where an outer peripheral bead
5
a
of the diaphragm
5
is disposed between a step portion
1
c
provided on an intermediate part of the cylindrical portion
1
a
of the front shell
1
and a shoulder portion
4
c
at the proximal end of the cylindrical portion
4
a
of the center shell
4
.
The above-described conventional pneumatic booster suffers, however, from the following problems. The cylindrical portion
1
a
of the front shell
1
and the cylindrical portion
4
a
of the center shell
4
are each formed in a circular straight cylindrical shape. Therefore, when front shells
1
(
1
A,
1
B and
1
C) as constituent parts before assembly are stacked on one another in such a manner that the cylindrical portions
1
a
of the front shells
1
are mounted on each other, as shown in FIG.
7
(A), the stacked condition of the front shells
1
is such that the opening edge
1
b
of each front shell
1
is only slightly engaged with the edge of the shoulder portion (step portion)
1
c
of the underlying front shell
1
. Similarly, the stack of center shells
4
(
4
A,
4
B and
4
C) is, as shown in FIG.
7
(B), such that the opening edge
4
b
of each center shell
4
is only slightly engaged with the edge of the shoulder portion (step portion)
4
c
of the underlying center shell
4
. Regarding the stack of rear shells
2
(
2
A,
2
B and
2
C), as shown in FIG.
7
(C), no overlap is present except that the reduced-diameter cylindrical portions
2
a
thereof butt to each other. Thus, all the stacks of front shells
1
, rear shells
2
and center shells
4
(these will hereinafter be referred to as “shell elements”) lack in balance, so that the stacked condition of shell elements is difficult to maintain stably Accordingly, handling of the stacked shell elements during storage, transport, etc. is extremely troublesome. Further, a large space is formed between each pair of adjacent shell elements when stacked as stated above, resulting in an increase In volume. Consequently, the storage efficiency and the transport efficiency degrade markedly, causing a large economic loss.
SUMMARY OF THE INVENTION
The present invention was made in view of the above-described problems with the prior art.
An object of the present invention is to provide a pneumatic booster designed so that when shell elements as constituent parts before assembly are stacked on one another, an overlap of a predetermined size can be ensured between each pair of adjacent shell elements, thereby making a great contribution to the improvement in handleability and to the improvement in storage efficiency and transport efficiency.
The present invention is applied to a pneumatic booster including a front shell element having a bottom portion and a cylindrical portion (outer cylindrical portion) extending from the edge of the bottom portion. The front shell element further has an inner cylindrical portion projecting in the same direction as the direction of extension of the outer cylindrical portion to receive a master cylinder. The pneumatic booster further includes a rear shell element having a bottom portion and a cylindrical portion (outer cylindrical portion) extending from the edge of the bottom portion. A shell body is formed by uniting together the front shell element and the rear shell element in such a manner that the opening edges of the outer cylindrical portions of the front and rear shell elements on the sides thereof opposite to their respective bottom portions are joined together. A valve body is provided to extend through the rear shell element. The valve body has a valve mechanism therein. A power piston is engaged with the valve body to divide the interior of the shell body into a constant-pressure chamber and a variable-pressure chamber. According to the present Invention, the outer cylindrical portion of the front shell element has at least one reduced-diameter portion smaller in diameter than the opening edge, and the inner cylindrical portion of the front shell element has at least one reduced-diameter portion
Schwartz Christophaer P.
Tokico Ltd.
Wenderoth , Lind & Ponack, L.L.P.
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