Metal deforming – Tool and/or tool holder – Having unitary tool-face
Reexamination Certificate
2000-08-18
2001-11-20
Jones, David (Department: 3725)
Metal deforming
Tool and/or tool holder
Having unitary tool-face
C072S478000, C072S466000
Reexamination Certificate
active
06318145
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a tube expanding bullet and a method of expanding a tube. More particularly, the present invention relates to a tube expanding bullet capable of expanding a tube that is pierced through collared fin holes of heat exchanging fins so as to expand the fin holes and integrate the tube with the heat exchanging fins, and a method of expanding a tube with the tube expanding bullet.
2. Description of the Background Art
In heat exchangers of air conditioners, etc., a plurality of heat exchanging fins are integrated with tubes, through which cooling fluid passes, so as to effectively facilitate heat transfer. A plurality of heat exchanging fins, each of which has a plurality of fin holes, are piled to form a heat exchanging body to integrate the heat exchanging fins with the tubes. The tubes are pierced through the fin holes of the piled heat exchanging fins. Next, the tubes are expanded to integrate the heat exchanging fins with the tubes.
Conventionally, a tube expanding bullet
100
(see
FIG. 6
) is used to expand the heat exchanging tubes. The bullet
100
is formed having a columnar shape, and a maximum outer diameter is equal to an inner diameter of an expanded tube. The bullet
100
is fixed to a front end of a mandrel
102
by a cone-shaped member
106
.
A male screw section
104
, which is upwardly extended from the cone-shaped member
106
, is pierced through the bullet
100
. The male screw section
104
is screwed with the mandrel
102
to fix the bullet
100
to the mandrel
102
.
A through-hole
108
is formed in the cone-shaped member
106
. A front end of a screw driver can be inserted into the through-hole
108
so as to easily detach the bullet
100
.
The tube
120
(see
FIG. 7
) is expanded by the bullet
100
shown in FIG.
6
. The tube
120
is pierced through fin holes
116
of heat exchanging fins
110
as shown in
FIG. 7. A
collar
112
, whose lower end is bent to form a flange section
114
, is extended from an edge of each fin hole
116
.
As shown in
FIG. 7
, the bullet
100
, which has a circular projected section whose maximum outer diameter is “D”, is inserted into the tube
120
which has already been pierced through the fin holes
116
. By inserting the bullet
100
, an inner diameter T of the tube
120
is extended to an expanded inner diameter T′, which is equal to the maximum outer diameter D of the bullet
100
.
Conventionally, the bullet
100
has the circular projected section whose maximum outer diameter is D to expand the tube
120
and the fin holes
116
and integrate the fins
110
with the tube
120
. Inner circumferential faces of the collars
112
can be tightly fitted to an outer circumferential face of the tube
120
.
However, in
FIG. 7
, some fins
110
are moved as shown by dotted lines
110
′ when the bullet
100
is passed through the tube
120
. Accordingly, the moved fin
110
′ tightly contacts the adjacent fin
110
. If some fins are moved and tightly contact adjacent fins, heat exchanging efficiency of the heat exchanger is lowered.
In order to avoid the tight contact of the fins which occurs by sudden expansion of the tube, the inventor of Japanese Patent Gazette No. 7-124670 invented an improved tube expanding bullet which was disclosed in Japanese Patent Gazette No. 7-124670. The improved bullet
200
is shown in FIG.
8
.
The bullet
200
shown in
FIG. 8
expands the tube
120
in two stages. Accordingly, the bullet
200
has a front part
202
, in which a circular projected section having a maximum outer diameter A is formed; and a rear part
204
, in which another circular projected section having a maximum outer diameter B is formed. The relationship between the maximum diameters A, B and an inner diameter T of the unexpanded tube is T<A<B.
By employing the bullet
200
shown in
FIG. 8
, the tube
120
is expanded by at least two stages, so that the force expanding the tube
120
can be dispersed evenly along the tube wall. With this dispersion, unlike the case of expanding the tube
120
with the bullet
100
shown in
FIG. 7
, the resulting tight contact of the heat exchanging fins
110
can be decreased.
However, even if the tube is expanded by the bullet
200
, the tight contact of the heat exchanging fins cannot be perfectly prevented. In the case of using very thin and light heat exchanging fins, the fins are even more apt to become tightly contacted and displaced.
In an embodiment of Japanese Patent Gazette 7-124670, a small expanding force works to an inner face of the collar when the tube is firstly expanded and an outer face of the expanded tube lightly contacts the inner face of the collar. With such a small expanding force, the firstly-expanded tube cannot expand the fin hole, and the collar cannot be integrated with the firstly expanded tube. In the second expanding stage, the firstly-expanded tube is further expanded and finally integrated with the collar. As described hereinabove, the fin whose collar is expanded by the secondly-expanded tube is displaced and therefore tightly contacts the adjacent fin whose collar has not yet been expanded.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a tube expanding bullet and a method of expanding a tube that are capable of preventing thin heat exchanging fins from becoming displaced and positioned with unfavorably tight contact.
The inventor of the present invention has studied the origin of the tight contact. The present inventor has found that the resulting tight contact of adjacent fins occurs at a non-expanded portion of the tube as well.
It appeared that the collar of the fin hole, which is expanded by the expanded tube, is extended so that the fin is moved and the undesirable tight contact of the adjacent fins occurs.
In the piled fins, as shown in
FIG. 7
, the flange
114
of each collar
112
contacts the lower adjacent fin
110
. With this structure, the expanded and extended collar
112
pushes the lower adjacent fin
110
in which the nonexpanded part of the tube is pierced through the fin hole. The lower fin is not integrated with the tube, so the lower fin is easily moved by the extended collar
112
of the upper fin and the adjacent fins are moved into tight contact.
In order to prevent the tight contact of the fins, the present inventor found that the tube can be properly expanded with a tube expanding bullet such as the two-stage bullet
200
shown in FIG.
8
. These and other objects of the present invention are accomplished by the steps of: firstly expanding the fin hole by the firstly-expanded tube so as to tightly fit the heat exchanging fin to the tube and further expanding the firstly-expanded tube.
The tube expanding bullet of the present invention is inserted into and expands a tube which has been pierced through a collared fin hole of a heat exchanging fin so as to expand the fin hole and integrate the tube with the heat exchanging fin. The tube expanding bullet comprises a first part being formed at a front part of the tube expanding bullet; and a second part, whose maximum outer diameter is greater than that of the first part, being formed at a rear part of the tube expanding bullet.
The fin hole is firstly expanded by passing the first part of the bullet through the tube and firstly expanding the tube, and the fin hole is secondly expanded by passing the second part of the bullet through the tube and secondly expanding the tube. The rate of expanding the fin hole by the first part is less than rate of expanding the same by the second part.
These and other objects of the present invention are accomplished by a method comprising the steps of: piercing a tube through collared fin holes of a plurality of heat exchanging fins which have been piled; and inserting a tube expanding bullet into the tube so as to expand the tube, whereby the fin holes are expanded by the expanded tube and the tube is integrated with the heat exchanging fins; expanding the tube by inserting the tube expanding bullet so as to
Birch & Stewart Kolasch & Birch, LLP
Hidaka Seiki Kabushiki Kaisha
Jones David
LandOfFree
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