GB2064689A

GB2064689A - Pneumatic servo booster

Info

Publication number: GB2064689A
Application number: GB8034294A
Authority: GB
Original assignee: Tokico Ltd
Current assignee: Tokico Ltd
Priority date: 1979-10-27
Filing date: 1980-10-24
Publication date: 1981-06-17
Also published as: JPS5669562U; FR2468777A1; DE3040475A1

Abstract

The booster includes a shell housing which is formed by oppositely disposing and connecting respective open end portions of generally cup-shaped front and rear shells (1, 2), and a flexible diaphragm (4) partitioning the shell housing into front and rear chambers (5, 6), and sealingly clamped at its periphery between the open end portions of the front and rear shells. At least two sets of axially spaced and radially inwardly projecting first and second retaining portions (7, 8) are formed on the open end portion of one of the front and rear shells, and a respective flange (2a) formed on the open end portion of the other shell is located between the first and second retaining portions of a set thereof thereby preventing the relative displacement between the first and second shells in the axial direction. <IMAGE>

Description

SPECIFICATION Pneumatic servo booster This invention relates to a pneumatic servo booster for use in, e.g. a braking system of a vehicle, and particularly to a pneumatic servo booster of the kind including a shell housing which is formed by oppositely disposing and connecting open end portions of generally cup-shaped front and rear shells, and a flexible diaphragm partitioning the interior of the shell housing into front and rear chamber with the outer circumference thereof being sealingly clamped between open end portions of the shells.

The pneumatic servo booster of the aforesaid kind further includes a valve mechanism for controlling the pressure difference between the front and rear chambers, an input shaft actuating the valve mechanism, a power piston connected to the diaphragm and receiving differential pressure force acting across the diaphragm, and an output shaft connected to the power piston. The shell housing receives the force generated by the pressure difference between the front and rear chambers, the reaction force of the output shaft, and the force acting on related parts such as a master cylinder which is secured to the front shell, thus, it has been required to rigidly connect the front and rear shells so as to prevent the relative displacement therebetween in the front and rear direction.

Conventionally, the open end portion of one of the shells is enlarged so as to define a radial step which faces with a flanged end portion of the other shell thereby restricting the relative displacement of the shells in the approaching direction. The relative displacement in the separating direction is prevented by inserting in the radial direction a projection formed on the outer circumference of the flanged end portion of the other shell into a retaining opening formed in the increased diameter portion of the one shell.

However, the pneumatic servo booster is usually installed in a restricted space in an engine compartment of the vehicle, thus it is disadvantageous to increase the overall diameter of the shell housing.

An object of the invention is to provide a pneumatic servo booster avoiding the shortcomings described as above and, according to the invention, at least two sets of radially inwardly projecting first and second retaining portions are formed on the open end portion of the front or rear shell, which retaining portions are spaced from each other in the front and rear direction, and a respective flange is formed on the open end portion of the other shell and is located between the first and second retaining portions of a set thereof thereby preventing the relative displacement of the shells in the front and rear direction.

The invention will now be explained with reference to the accompanying drawings exemplifying some embodiments of the invention.

In the drawings: Figure 1 is a partial sectional side view of a pneumatic servo booster according to the invention; Figure 2 is an enlarged partial perspective view of a front shell of the servo booster of Fig. 1; Figure 3 is an enlarged partial view of a portion of Fig. 1 which is surrounded by a circle, and Figure 4 is a view similar to Fig. 3 but showing a modified form.

The pneumatic servo booster illustrated in Fig. 1 comprises a shell housing 3 consisting of a front shell 1 and a rear shell 2. An annular flexible diaphragm 4 divides the interior of the shell housing 3 into a front chamber 5 and a rear chamber 6. The front and rear shells 1 and 2 have generally cup-shaped form and the open end portions of the cups are opposingly disposed to each other and are sealingly connected with the outer circumferential portion of the diaphragm 4 being clamped therebetween.

Figs. 2 and 3 show the connection between the front and rear shells 1 and 2. There are provided on the open end portion (the righthand end portion as viewed in the drawings) of the front shell 1 a plurality of sets of first and second retaining portions 7 and 8 in which the portions of each set are spaced in the front and rear or axial direction, and in the circumferential direction and in which the portions project in the radially inward direction.

In the drawings, short cuts 9, 10 and 11 are formed in the front shell 1 to extend respectively in the direction of the circumference of the front shell 1 and which are spaced from each other in the front and rear direction, and the portions defined between cut lines 9 and 10 are deformed radially inwardly to form, the first retaining portions 7; second retaining portions 8 being formed by deforming radially inwardly the portions defined between the cuts 11 and the open end of the front shell 1.

There is provided a radially outwardly extending annular flange 2a on the rear shell 2 and the thickness of the annular flange 2a corresponds to the space between the cuts 10 and 11. The front and rear shells 1 and 2 are connected to each other by inserting the annular flange 2a of the rear shell 2 into the space between the first and second retaining portions 7 and 8, thereby the relative displacement between the first and second shells in the front and rear direction is prevented.

Preferably, the annular flange 2a is formed on the rear end of an annular rearwardly extending bent portion 2b formed on the open end portion of the rear shell 2 as shown in Fig. 3. An annular thick portion 4a of the diaphragm 4 is sealingly clamped between the front shell 1 and the bent portion 2b of the rear shell 2.

In the embodiment, there is formed a plurality of sets of first and second retaining portions 7 and 8 on the outer shell 1, as shown in Fig. 1, in which the portions in each set are aligned with each other in the front and rear direction, but the first and second retaining portions may be displaced in the circumferential direction.

The pneumatic servo booster of Fig. 1 is of a conventional type and further includes an input shaft 12, an output shaft 1 3 and conventional internal elements (not shown) such as a valve mechanism actuated by the input shaft 1 2 for controlling the pressure difference between the front and rear chambers 5 and 6, and a power piston associated with the diaphragm 4 for receiving the differential pressure force and transmitting the output force to the output shaft 1 3. However, since they are conventional, the detailed explanation relating to the construction of the internal elements and the functions thereof are omitted.

Fig. 4 shows a modified form, wherein a first retaining portion 7' is defined by a radially inwardly projecting indentation formed on the front shell 1 and a second retaining portion 8' is formed by radially inwardly deforming the edge portion of the open end of the front shell 1. In this embodiment, the first retaining portion 7' is annular to extend around the entire circumference of the front shell 1 as is formed by such as a beading process, and a plurality of circumferentially spaced second retaining portions 8' is formed by such as a cutting and bending process: however, both retaining portions 7' and 8' may have a continuous annular form or a circumferentially spaced arrangement i.e. an intermittent annular form.

Alternatively, the first and second retaining portions may be formed on the rear shell 2 and the complementary flange on the front shell.

As described heretofore, the diameter of the shell housing can be reduced according to the invention, and the front and rear shells can be connected with each other easily and reliably.

Claims

1. A pneumatic servo booster including a shell housing which is formed by oppositely disposing and connecting respective open end portions of generally cup-shaped front and rear shells, and a flexible diaphragm partitioning the interior of the shell housing into front and rear chambers, with the outer circumference thereof being sealingly clamped between the open end portions of the front and rear shells, wherein at least two sets of radially inwardly projecting first and second retaining portions are formed on the open end portion of one of the front and rear shells, said first and second retaining portions being spaced from each other in the front and rear direction, and a respective flange is formed on the open end portion of the other shell and is located between the first and second retaining portions of a set thereof thereby preventing the relative displacement of the shells in the front and rear direction.

2. A booster as claimed in claim 1, wherein a plurality of sets of circumferentially extending and axially spaced first, second and third cuts are formed in the outer end portion of the one shell, said respective sets being spaced circumferentially; and portions defined between the first and second cuts are deformed radially inwards to constitute the first retaining portion, and portions defined between the third cuts and the open end of said one shell are deformed radially inwards to constitute the second retaining portion.

3. A booster as claimed in claim 1, wherein said first portions are formed by a continuous or intermittent annular indentation of the shell, and said second portions by a continuous or intermittent radially inwardly bent edge portion of the shell.