Railway rolling stock – Car framing and structure – End sills
Reexamination Certificate
1999-12-02
2001-07-24
Le, Mark T. (Department: 3617)
Railway rolling stock
Car framing and structure
End sills
C105S396000, C105S402000, C105S410000, C105S422000, C105S413000
Reexamination Certificate
active
06263805
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a box type structural body containing a lap joint to which welding can not be applied from the inner side of the body, and a vehicle end sill which corresponds to such box type structural body.
2. Description of the Related Art
A structural body for a head portion of a (commuter) railway vehicle (rolling stock) is shown in FIG.
4
. In an example in
FIG. 4
, a bone member, which is located at a front end (or rear end) of a vehicle A and is extending along the vehicle width direction, is called an “end sill”. An end sill
1
is provided to bear the load applied when the vehicle A collides with the other vehicle or the object. The end sill
1
is a box type structural body which has, for example, a longitudinal sectional shape as shown in FIG.
5
A.
The end sill
1
′ shown in
FIG. 5A
is formed as a box shape by extending a beam-like end member
11
such as channel member at a front end portion of the vehicle A along the width direction. Upper and lower face plates
12
,
13
are welded to upper and lower surfaces of the end member
11
. The box type structure is a closed (or almost closed) structure and has no inner space into which an operator or a welding machine can enter. Therefore, lap joints W′ between the end member
11
and the upper and lower face plates
12
,
13
are welded merely from the outer side of the box type structure and are not welded from the inner side of the box type structure. A weld seam W′ of the joint W′ extends linearly, as shown in FIG.
5
B. The weld seam Wa′ of the joint W′ is positioned perpendicularly to the direction of the load applied from the left side in
FIG. 5B
, which is caused by a collision of the vehicle A with the other object (such as the other vehicle).
The face plates
12
,
13
at the end sill
1
′ shown in
FIGS. 5A
to
5
C can be deformed in the form of an out-of-plane deformation by low load, and in some cases they are broken off since the bending moment is applied to the joint W′ correspondingly. When the load caused by the collision is applied from the left side of
FIG. 5A
with the result of an application of the bending moment onto the joints W′ (see an arrow shown in FIG.
5
D), such bending moment is received only by a throat thickness of a weld bead of the weld seam Wa′ since the weld seam Wa′ of the joint W′ is formed as a straight line. For this reason, the joint W′ tends to deform as shown in FIG.
5
D and also tends to break of f as shown in FIG.
5
E. In this manner, if the joint W′ is easily deformed and broken off, a collision energy cannot be sufficiently absorbed by the end sill
1
′ which includes the face plates
12
,
13
, etc.
As for the joint W′ in the end sill
1
′ as shown in
FIGS. 5A
to
5
E in the related art,
FIG. 5F
is a graph showing a typical relation between an amount of deformation &dgr; and an reaction P of the joint W′ when the joint W′ is deformed. Since the joint W′ is broken off as shown in
FIG. 5E
at a point x of time when the reaction P is increased, the succeeding reaction P is reduced abruptly. An amount of collision energy which can be absorbed by the joint W′ can be expressed by a shaded area (i.e., ∫Pd &dgr;) in FIG.
5
F. As shown in
FIG. 5F
, the amount of absorbed collision energy is not sufficiently large. If the absorption energy of the joint W′ is small, the energy which can be absorbed by the end sill
1
′ is also small. Therefore, remaining collision energy, which can not be absorbed by the end sill
1
′, acts onto other portions of the vehicle A and thus the considerable damage of the vehicle A is caused.
Although above-mentioned explanation has been made by taking the vehicle end sill into consideration as an example, the similar problem also occurs in other box type structural bodies. In other words, if the box type structural body includes the lap joints which are linearly welded only from the outer side (one side welding) for the structural reason and the direction of the weld seams of the lap joints is set perpendicular (or closely perpendicular) to the direction of the load, the lap joints can be broken off easily when they receive the load. In addition, in the end sill
1
′ in FIG.
5
A and the box type structural body in the related art, another fracture mode may be considered. That is a shear fracture of the weld bead in the form that the end member
11
and the face plates
12
,
13
are shifted in parallel with their lapped faces without the deformation shown in
FIGS. 5D and 5E
.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a box type structural body and a vehicle end sill, of which the abovementioned lap joint welded by one side lap welding cannot be broken off easily.
According to a first aspect of the present invention, a box type structural body comprises: a pair of plate members each having an edge which is formed in a zigzag shape; the plate members facing each other with a clearance therebetween; an intermediate member disposed between the plate members, the intermediate member having a pair of surfaces to which the zigzag edges of the plate members are superposed and attached respectively by lap weldings along the zigzag edges, the lap weldings being conducted outside the structural body, the intermediate member having a longitudinal axis which is substantially perpendicular to a direction along which a load is adapted to be applied to the structural body.
According to such box type structural body, if it receives the load in the direction substantially perpendicular to the direction of the longitudinal axis of the intermediate member, the joint made by the lap welding is never simply broken off unlike the related art shown in FIG.
5
. This is because the weld seam (only one side) of the lap joint is formed as the zigzag shape with the result that not only the throat of the weld bead but also the zigzag weld seam can stand the bending moment unlike related art shown in
FIG. 5
, when the structural body receives the load along the above-mentioned direction. In other words, in the box type structural body, the weld bead can stand the larger shearing load since the sectional area is increased with the increase of the total length and a part of the total length is provided along the depth direction of the zigzag shape. Therefore, when the bending moment is caused like that in
FIG. 5D
, he weld bead can bear the bending moment by the small stress. Since the joint is not easily deformed or ruptured, the energy which can be absorbed by the box type structural body can be considerably increased.
In the box type structural body, a depth and a pitch of the zigzag edge may be set such that a stress caused by the load at a weld bead of the lap welding does not come up to its yield point even if a full plastic bending moment of the plate member is caused in a plane substantially perpendicular to the longitudinal axis of the intermediate member.
The dimensions of the zigzag shape are decided as above, the weld bead of the joint never generates its plastic deformation until the plate member is brought into its full plastic deformation state even if the above-mentioned bending moment is caused by the load. In other words, since the joint can stand such large bending moment, the energy absorbed by the box type structural body can be increased as far as material of respective members are selected appropriately.
In the box type structural body, the zigzag shape may include a rectangular sawtooth shape.
In the box type structural body, the zigzag shape may include a triangular sawtooth shape.
In the box type structural body, the zigzag shape may include a trapezoidal sawtooth shape.
In the box type structural body, the zigzag shape may include a circular-arc sawtooth shape.
According to a second aspect of the present invention, a vehicle end sill comprises: a pair of plate members each having an
Marunaka Toshinori
Taguchi Makoto
Kawasaki Jukogyo Kabushiki Kaisha
Le Mark T.
Oliff & Berridg,e PLC
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