Metal deforming – Process – Tube making or reshaping
Reexamination Certificate
2000-01-10
2001-09-18
Larson, Lowell A. (Department: 3725)
Metal deforming
Process
Tube making or reshaping
C072S356000
Reexamination Certificate
active
06289710
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method of manufacturing a hollow rack bar, wherein a flat portion is formed in a steel pipe and rack teeth are formed in the flat portion.
BACKGROUND OF THE INVENTION
In a conventional rack-and-pinion steering system for motor vehicles and the like, a rack bar has been employed. Recently, it has been tried to hollow the rack bar so as to make it more lightweight. In a method of manufacturing such a hollow rack bar, as disclosed in Publication of Examined Japanese Utility Model Application No. Hei 1-87335, an electric resistance welded tube or an extrusion molded steel pipe is employed and rack teeth are formed in the periphery of the tube or the steel pipe by press working. In the press working, as shown in
FIG. 7
, a steel pipe
50
into which a core
52
is inserted is placed between an upper and a lower metal dies and another upper metal die
58
having a rack teeth configuration is pressed on the periphery of the steel pipe
50
, and thereby the rack teeth are formed.
However, such a conventional method has a problem that since the core has a central flat portion and downward slopes on both sides thereof, the diameter of a corner
60
becomes large, so that an enough thickness of a flat portion
62
cannot be obtained. Furthermore, deformation of the inner periphery of the steel pipe
50
during the press working results in close contact of the core
52
with the inner periphery of the steel pipe
50
and prevents the core
52
from being removed from the steel pipe
50
.
SUMMARY OF THE INVENTION
Wherefore, an object of the present invention is to provide a manufacturing method of a hollow rack bar provided with a flat portion having an enough thickness, which prevents difficulty in removing a core inserted during press working.
This and other objects of the invention are achieved in a manufacturing method of a hollow rack bar by flattening a steel pipe to form a flat portion and forming rack teeth in the flat portion, wherein the flat portion is formed by inserting a core having an approximately central depression in the longitudinal direction into the steel pipe and pressing the steel pipe from the outside using metal dies.
Preferably, after forming the flat portion, the rack teeth are formed by placing the steel pipe in a tooth profile forming die and forcibly inserting a mandrel into the steel pipe. Furthermore, the flat portion is preferably made thick.
Advantages of this manufacturing method are that an enough thickness of the flat portion can be obtained, that the core can easily be pulled out after the formation of the flat portion, and that the endurance of the core is improved.
REFERENCES:
patent: 1983584 (1934-12-01), Urschel
patent: 3670555 (1972-06-01), Fredericks
patent: 4598451 (1986-07-01), Ohki
patent: 137335 (1989-11-01), None
patent: 35892 (1991-02-01), None
Larson Lowell A.
Tarolli, Sundheim, Covell Tummino & Szabo L.L.P.
TRW Automotive Japan Co., Ltd.
LandOfFree
Method of manufacturing a hollow rack bar does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of manufacturing a hollow rack bar, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of manufacturing a hollow rack bar will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2499911