Pipes and tubular conduits – Flexible – Braided – interlaced – knitted or woven
Reexamination Certificate
1999-07-30
2001-04-24
Hook, James (Department: 3752)
Pipes and tubular conduits
Flexible
Braided, interlaced, knitted or woven
C138S141000, C138S146000
Reexamination Certificate
active
06220304
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a brake hose, such as an oil pressure hose, or the like, having reinforcing thread layers braided intermediately for use in a flow path for a pressure fluid.
The present application is based on Japanese Patent Application No. Hei. 10-230341, which is incorporated herein by reference.
2. Description of the Related Art
Heretofore, for example, a brake hose shown in
FIG. 8
is known as brake hose of this type.
FIG. 8
is a sectional view showing a brake hose
100
. The brake hose
100
is constituted by lamination of an inner tube layer
102
, a lower thread layer
104
, an intermediate rubber layer
106
, an upper thread layer
108
and a skin rubber layer
110
successively in outward order from a flow path
101
for making an operating fluid flow. To produce the brake hose
100
, first, an EPDM rubber material is extrusion-molded annularly to form the inner tube layer
102
. Lower threads are then braided by a braider to form the lower thread layer
104
. A sheet-like rubber material is then wound on the lower thread layer
104
. Upper threads are then braided to form the upper thread layer
108
. A dipping process is then carried out so that an adhesive agent is applied onto the upper thread layer
108
. After the adhesive layer is dried, a rubber material is extruded onto the upper thread layer
108
to thereby laminate the skin rubber layer
110
on the upper thread layer
108
. Further, a vulcanizing process and a predetermined after-process are carried out to thereby complete the brake hose
100
. In the brake hose
100
, the two layers, that is, the lower and upper thread layers
104
and
108
are buried in a rubber base in order to enhance pressure resistance. Furthermore, the adhesive agent layer
109
is applied onto the upper thread layer
108
to thereby enhance the bonding strength between the upper thread layer
108
and the skin rubber layer
110
to thereby enhance the pressure resistance.
Although the adhesive agent layer
109
has an effect of enhancing the bonding strength of the upper thread layer
108
, etc. on one hand, the adhesive agent layer
109
makes the stiffness of the brake hose
100
per se high on the other hand. If the stiffness of the brake hose
100
is made high, it becomes difficult to bend the brake hose
100
smoothly in response to the motion of a tire. There was a problem that durability was spoiled.
In the case where the amount of application of the adhesive agent layer is reduced to decrease the stiffness to cope with the aforementioned problem, the amount of volume expansion of the brake hose
100
increases to spoil the brake feeling when the pressure of an operating fluid is applied to the inside of the brake hose
100
. Thus, durability decreases as the stiffness of the brake hose
100
increases, while the amount of volume expansion of the brake hose
100
increases to spoil the brake feeling as the stiffness decreases. There was therefore a problem that it was difficult to make the two consistent with each other.
SUMMARY OF THE INVENTION
The present invention is designed to solve the problems in the background art and it is an object thereof to provide a brake hose in which both enhancement of durability and reduction of the amount of volume expansion are made consistent with each other.
In order to achieve the foregoing object, according to the present invention, a brake hose is provided, which comprises an inner tube layer which is made from a rubber material for forming a flow path for making a pressure fluid flow, a lower thread layer formed on the inner tube layer by braiding lower threads, an intermediate rubber layer made from a rubber material and laminated on the lower thread layer, an upper thread layer formed on the intermediate rubber layer by braiding upper threads, and a skin rubber layer laminated on the upper thread layer. The lower thread layer is made from lower threads each having a first adhesive thin film adhesively bonded to the inner tube layer and to the intermediate rubber layer, and the upper thread layer is made from upper threads each having a second adhesive thin film adhesively bonded to the intermediate rubber layer and to the skin rubber layer.
In the brake hose according to the present invention, the lower thread layer formed between the inner tube layer and the intermediate rubber layer and the upper thread layer formed between the intermediate rubber layer and the skin rubber layer form two reinforcing thread layers in a rubber base so that strength to withstand the high pressure of a pressure fluid flowing in the flow path is given to the brake hose per se. Further, each of lower threads constituting the lower thread layer has a first adhesive thin film. The first adhesive thin films are adhesively bonded to the inner tube layer and to the intermediate rubber layer to thereby prevent thread displacement. At the same time, the first adhesive thin films are adhesively bonded to one another in lower thread-overlap portions to thereby enhance the integration of the lower thread layer to suppress the expansion of the inner tube layer caused by the inner pressure. Accordingly, the amount of volume expansion of the brake hose per se is suppressed to thereby improve the brake feeling.
On the other hand, each of upper threads constituting the upper thread layer has a second adhesive thin film. The second adhesive thin films are adhesively bonded to the intermediate rubber layer and to the skin rubber layer to thereby prevent thread displacement. Furthermore, the upper threads are adhesively bonded to one another through the second adhesive thin films to thereby enhance the integration of the upper thread layer. Accordingly, a pressure fluid leaked out of an end portion of the brake hose is prevented from penetrating in between the intermediate rubber layer and the skin rubber layer. Furthermore, the upper thread layer is formed so that the upper threads are adhesively bonded to one another through the second adhesive thin films. Accordingly, the upper thread layer per se is prevented from becoming hard unlike the adhesive layer formed by the dipping process as described in the background art. Accordingly, the stiffness of the brake hose per se can be reduced to thereby improve both fatigue resistance and durability.
Further, as a preferred mode of the lower threads, each of the lower threads has a filament bundle constituted by a plurality of first filament threads tied up in a bundle, and the lower thread can be achieved by the formation of the first adhesive thin film on the outer surface of the filament bundle. For example, each of the lower threads can be prepared by the steps of: tying up about 200 to about 400 filament threads in a bundle; applying an undercoat layer onto the bundle; and applying an RFL process to the bundle. The lower threads are braided on the inner tube layer to thereby form the lower thread layer. In this case, the lower threads are adhesively bonded to one another through the first adhesive thin films. Accordingly, there is a large force for suppressing the expansion of the diameter of the inner tube layer due to the pressure of an operating fluid in the flow path.
Here, as the first adhesive thin film, a film having a large adhesive force to EPDM can be formed by an RFL process. The RFL process used herein means a process in which adhesive thin film acting as an adhesive agent containing resorcin-formaldehyde-latex resin and rubber latex as main components is applied on a surface of thread. That is, with respect to each of the lower threads, an adhesive thin film having a large adhesive force to a rubber material can be formed by the RFL process, so that a large adhesive force to the inner tube layer and to the intermediate rubber layer can be obtained by the adhesive thin film.
Further, as a preferred mode of the upper threads, each of the upper threads can be achieved by the steps of: forming adhesive thread having a second adhesive thin film obtained by applying an undercoat layer
Horiba Ryuichi
Kawai Etsuko
Hook James
Pillsbury & Winthrop LLP
Toyoda Gosei Co,., Ltd.
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