Pipes and tubular conduits – Flexible – Braided – interlaced – knitted or woven
Reexamination Certificate
2000-10-18
2002-06-25
Hook, James (Department: 3752)
Pipes and tubular conduits
Flexible
Braided, interlaced, knitted or woven
C138S109000, C138S125000, C285S286200, C285S332000
Reexamination Certificate
active
06408890
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention:
This invention relates to a hose connecting structure obtained by press fitting a hard pipe into a flexible hose, such as of rubber, while expanding the latter radially to a certain extent. This type of structure is often employed for connecting, for example, hoses and a branched hard pipe in an automobile engine compartment.
2. Description of the Related Art:
In an assembly in which a hard pipe is simply press fitted into a flexible hose, the hose is likely to slip off easily. Therefore, various proposals have been made to join a hose to a pipe in such a way that the hose may not easily slip off the pipe. For example, an adhesive is employed for bonding the inner surface of a hose to the outer surface of a pipe. According to another proposal, an O-ring is interposed between a flexible hose and a hard pipe. Still another proposal is shown in
FIG. 1
, which relies upon a clip
3
fitted about a hose
2
for holding it against a pipe
1
press fitted in the hose
2
. These methods are, however, generally not satisfactory in working efficiency, and they do not always make a hose connecting structure which is satisfactory in pull-out strength and sealing properties. Moreover, a lug
4
projecting from the clip
3
is an obstacle in, for example, engine compartments of recent automobiles having a high density of installed items.
An assembly proposed more recently to overcome those problems is obtained by press fitting a hard pipe having stoppers projecting from its outer periphery into a flexible hose. For example, Japanese Patent Application Laid-Open No. 331894/1992 discloses a hard pipe
6
having stoppers
5
formed on its outer periphery by exchange mold injection from a soft material, and pressed fitted in a flexible hose
7
, as shown in FIG.
2
. Japanese Patent Application Laid-Open No. 159077/1997 discloses a branched pipe
8
of a hard material having three branches
9
each having formed on its outer periphery stop ridges
10
each having a cross section terminating in a sharp edge, each branch
9
being press fitted in a flexible hose
12
having a reinforcing fiber layer
11
in its wall, as shown in FIG.
3
.
The methods as disclosed in those two Japanese patent applications are better in working efficiency than the previously known ones as described before, since the connecting work is completed merely by press fitting a pipe into a hose. They are, however, still not always satisfactory in pull-out strength and sealing properties. In Japanese Patent Application Laid-Open No. 331894/1992, the stoppers
5
as shown in
FIG. 2
are formed separately from the pipe
6
, and even if the advantages of their exchange mold injection may be taken into account, a strong pull-out force acting upon the assembly is likely to cause the stoppers
5
to come off the pipe
6
or become displaced and thus it is feared that the assembly will not maintain satisfactory pull-out strength and sealing properties. In Japanese Patent Application Laid-Open No. 159077/1997, the ridges
10
as shown in
FIG. 3
form integral parts of the pipe, but their hard and sharp edges are held against the inner surfaces of the hoses
12
so tightly that if there is a strong impact upon the assembly, the hoses
12
may be damaged by the edges of the ridges
10
and lose sealing properties. As each hose is expanded to a greater diameter when fitted about the pipe, the edges of the ridges
10
are held against the wall of the hose
12
more tightly, and are more likely to damage the hose.
SUMMARY OF THE INVENTION
It is, therefore, an object of this invention to overcome all of the various drawbacks as pointed out above with respect to a hose connecting structure obtained by press fitting a hard pipe into a flexible hose while expanding the latter radially.
According to a first aspect of this invention, there is provided a hose connecting structure comprising a flexible hose having a reinforcing fiber layer in its wall, and a hard pipe a portion of which is press fitted in the hose, wherein the pipe has an annular stop projection formed about its press fitted portion, and having a cross sectional contour including a gentle outward slope from the front end of the projection toward the rear end side to a first corner, which makes the angle of the subsequent second corner gentle, and a rear face at this second corner extending inward toward the longitudinal axis of the pipe at right angles thereto, forming an annular depression.
The structure can be made with high working efficiency using a method in which the hard pipe is press fitted into the flexible hose while the hose is radially expanded. Even if a strong pull-out force may act upon the assembly, the stop projection forming an integral part of the pipe does not come off, or become displaced, but the assembly maintains its pull-out strength and sealing properties.
The structure further has the following advantages:
(1) The stop projection
14
having a gentle slope from the front end toward the rear end side in its cross sectional contour, as shown in
FIG. 4A
, facilitates the press fitting of the pipe
13
into the hose
15
.
(2) The stop projection
14
having in its cross sectional contour a rear face
16
extending from the second corner
17
b
toward the central longitudinal axis of the pipe
13
at right angles thereto ensures the high pull-out strength and sealing properties of the structure, since the rear face
16
engaging the inner surface of the hose
15
resists strongly any pull-out force acting upon it, as is obvious from FIG.
4
B. In this connection, the second corner
17
b
is not necessarily required to have a sharp angle which is by far smaller than 90°, but the projection
14
is effective if the second corner
17
b
has an angle of, say, 70° to 110°.
(3) The second corner
17
b
of the stop projection
14
has its angle enlarged by the presence of its first corner
17
a
. It is, therefore, possible to avoid any damaging of the hose by a sharp projection and any resulting lowering of sealing properties as pointed out before in connection with the assembly disclosed in Japanese Patent Application Laid-Open No. 159077/1997.
The hose
15
has a reinforcing fiber layer
18
in its wall. The reinforcing fiber layer
18
does not, however, present any resistance to the press fitting of the pipe
13
, since the hose
15
is radially expanded when the pipe
13
is press fitted therein, as is obvious from (1) above. If a pull-out force acts upon the structure, the hose
15
is caused to contract radially, and the reinforcing fiber layer
18
holds the inner surface of the hose
15
strongly against the stop projection
14
to enhance the pull-out strength of the assembly, as is obvious from (2) above. It is, however, possible to avoid any damaging of the hose
15
, as is obvious from (3) above.
According to a second aspect of this invention, the hose is radially expanded by at least 20% when the pipe is press fitted thereinto. The radial expansion of the hose to such an extent ensures the still higher pull-out strength and sealing properties of the assembly, while it is still possible to avoid any damaging of the hose by the stop projection on the pipe and any resulting lowering of sealing properties, as explained above.
According to a third aspect of this invention, at least an innermost wall layer of the hose is formed from an elastomer having a tear strength of at least 20 N/mm, such as EPDM (an ethylene-propylene-diene terpolymer) or EPM (an ethylene-propylene copolymer). If the hose is radially expanded by a very high percentage (say, 30 to 50%), there is some possibility or other of the hose being damaged by the stop projection on the pipe, even if its second corner may have an enlarged angle as stated before. The elastomer is effective for protecting the hose under such circumstances.
According to a fourth aspect of this invention, the reinforcing fiber layer has a pull-out strength of at least 0.3 N/mm. The radial expansion of the hose by a very high percentage may cause the separa
Hook James
Jacobson & Holman PLLC
Tokai Rubber Industries Ltd.
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