U.S. patent application number 11/306435 was filed with the patent office on 2007-11-29 for method for forming a cam-engaged rocker arm.
This patent application is currently assigned to GENTEK TECHNOLOGIES MARKETING INC.. Invention is credited to Dan Mills, Scott P. Smith.
Application Number | 20070271985 11/306435 |
Document ID | / |
Family ID | 38748267 |
Filed Date | 2007-11-29 |
United States Patent
Application |
20070271985 |
Kind Code |
A1 |
Smith; Scott P. ; et
al. |
November 29, 2007 |
Method for Forming a Cam-Engaged Rocker Arm
Abstract
Valve guides are formed on a U-shaped sheet metal rocker arm by
the horizontal displacement inwardly of surface metal from the
outboard portion of the rocker arm. A rocker arm body made by
forming a steel flat blank into a U-shape cross-section comprising
sidewalls that connect a pad end and an opposite socket end. The
pad end is defined by a central section and two outboard surfaces.
The valve guide walls are formed by displacing material from the
outboard surface portions of the pad end and forcing it centrally.
This changes, i.e., diminishes, the thickness of the outboard
portions of the pad end of the rocker arm which are not aligned
with valve contact central surface. The valve contact area defined
by horizontal surface and by the vertical sides of the formed guide
extensions is created by a tool having a width to accept a known
valve stem diameter. The valve guide extensions are parallel to and
offset from the pad end rocker arm sidewalls and are created to
have the proper thickness as well as suitable height to survive in
the rocker arm application. The surface extremity, i.e., height as
well as the thickness of the valve guide wall, is determined by the
amount of material displaced from surfaces of the outboard portion
of the pad end of the rocker arm. Valve guide extension height and
thickness dimensions can be achieved that were not attainable by
known prior art methods.
Inventors: |
Smith; Scott P.;
(Temperance, MI) ; Mills; Dan; (Maumee,
OH) |
Correspondence
Address: |
ARTHUR J. PLANTAMURA;GENERAL CHEMICAL PERFORMANCE PRODUCTS LLC.
90 EAST HALSEY ROAD
PARSIPPANY
NJ
07054
US
|
Assignee: |
GENTEK TECHNOLOGIES MARKETING
INC.
90 East Halsey Road
Parsippany
NJ
|
Family ID: |
38748267 |
Appl. No.: |
11/306435 |
Filed: |
December 28, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10927372 |
Aug 26, 2004 |
|
|
|
11306435 |
Dec 28, 2005 |
|
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Current U.S.
Class: |
72/362 |
Current CPC
Class: |
F01L 1/185 20130101;
B21K 1/205 20130101 |
Class at
Publication: |
072/362 |
International
Class: |
B21D 31/00 20060101
B21D031/00 |
Claims
1. A method of forming guide elements on a rocker arm formed by
bending a sheet metal blank into a U-shaped intermediate having a
pad end, a mid-portion and a socket end comprising the steps: (a)
displacing material laterally from the surfaces of the outboard
portions at the bottom of the pad end and forcing controlled
portions of the displaced material laterally inwardly to form valve
guides and thereby diminishing the thickness of said outboard
portions while essentially retaining the thickness of the central
pad section contained within said outboard portion; (b) maintaining
the lateral displacement of material such that guides that extend
substantially perpendicularly from the pad end surface and have a
width conforming to the desired valve stem diameter are formed; and
(c) continuing the displacement of said displaced material from the
outer sections of the pad end to create valve guides of the desired
height.
2. The method of claim 1 applied to form valve guides for a roller
follower rocker arm.
3. The method of claim 1 applied to form valve guides for a flat
rocker arm.
4. The method of claim 1 applied to for valve guides for a center
pivot rocker arm.
Description
[0001] This application is a continuation-in-part application of
application Ser. No. 10/927,372, filed on Aug. 20, 2004, and claims
the benefit of Provisional Application No. 60/498,076, filed on
Aug. 27, 2003, the contents of which are hereby incorporated herein
in their entirety.
TECHNICAL FIELD
[0002] The present invention relates to a method of forming a
rocker arm by stamping metal blanks. More particularly, the
invention relates to a novel method of forming finished valve
guides for the rocker arm by the horizontal displacement inwardly
of metal from the outer sides at the bottom of the bent U-shaped
rocker arm at the pad end of the rocker arm.
BACKGROUND OF THE INVENTION
[0003] In automotive and other applications, an overhead cam engine
typically utilizes a plurality of cam engaged rocker arms which
function to open valves. These rocker arms pivot at one end,
contact the valve at an opposite end, and support a roller between
the two ends. The roller engages the cam and the cam rotates to
move the roller, thereby causing the rocker arm to pivot at the
pivot end, and push the valve open.
[0004] Rocker arms can be manufactured by casting metals, blanking
and forming, ceramic molding, and other methods. Stamping a metal
blank to form a rocker arm including a valve stem guide is common
in the art. The valve stem guides of the rocker arms are typically
formed using a punch and cavity, folding or coining process. During
the coining process, an upper die and a lower die punch an area of
the metal blank to plastically deform the metal blank. To form the
valve guide, the area of the metal blank being coined has a
thickness greater than the remaining metal blank, thereby providing
additional material to use in forming the valve guides. This
deformation of the metal blank typically displaces material from
nearby areas of the blank to create a valve guide. In this forming
operation, a deficiency may occur when the thickness of the blank
area that lost material (used to create the guide) may be below
required minimum thickness. It is important that the minimum
thickness for a rocker arm be maintained for purposes of strength
and durability notwithstanding that some of the material of the
blank is used to form valve guides.
[0005] The method for forming similar types of stamped rocker arms
is known such as that of Ammon (U.S. Pat. No. 6,615,635) (col. 3,
lines 40-59 and FIGS. 1 and 2) and Motohashi (U.S. Pat. No.
6,425,361) (col. 4, lines 13-38 and FIGS. 5A-5D) (col. 5, lines
1-19 and FIG. 6). These references describe in general how the
guide walls are formed in the blank by applying vertical forces to
the upper and lower surfaces of the blank allowing material to
plastically flow into cavities. The sidewalls are then bent to form
the U-shape cross-section. Process of this kind have the
disadvantage of requiring excessive pressure and frequently yields
loss of strength which results in crazing and lowering of strength
as a result of the pressure needed to create a plastic flow.
Additional work is required to finish the guide walls but no
description for such needed finishing operation is provided by
these patent disclosures.
SUMMARY OF THE INVENTION
[0006] The present invention provides a unique method for providing
finished valve pad side walls and affords a substantial improvement
over the known prior art because the forming of the valve guide
walls are shaped after the rocker arm is formed into a U-shaped
cross-section and because the quantity of material displaced to
form the guide elements is accurately controllable. Material from
outside the valve pad area of the U-shaped metal blank is displaced
laterally by a tool which moves horizontally to transition the
desired quantity of metal to create without further work the
finished valve guide. Forming of the valve guide elements is
effected by displacing material from the outer surface portion of
the bottom of the U-shaped metal sheet and forcing it inwardly.
This creates new outer surfaces which are thinner, i.e., not
aligned with the central pad surface, the thickness of which
remains substantially unchanged. The valve contact area surfaces
are created by a tool having a width to accept a known valve stem
diameter. The valve guide extensions are parallel and offset to the
outer rocker arm sidewalls surfaces and by controlling displacement
of the appropriate amount of metal, create guides having the proper
thickness to survive in the assigned application. The height of the
valve guide elements is essentially determined by the amount of
material displaced horizontally inwardly by the laterally
converging guide forming tool.
[0007] The method of the invention employs less cumbersome
equipment and affords better control in metal displacement when
forming guide elements on sheet metal rocker arms formed by bending
a sheet metal blank into a U-shaped intermediate having a pad end,
a mid-portion and a socket end. The steps involved include
displacing material laterally from the surfaces of the outboard
portions at the bottom of the pad end and forcing controlled
portions of the displaced material laterally inwardly to form the
valve guides. The metal displacement diminishes the thickness of
the outboard portions at the bottom of the U-shaped rocker arm
intermediate while essentially retaining the thickness of the
central pad section contained within said outboard portion.
[0008] The lateral displacement of metal at the bottom of the
U-shaped sheet metal is effected such that the guides formed by the
lateral displacement of metal extend substantially perpendicularly
from the pad end surface and have a width conforming to the desired
valve stem diameter.
[0009] The displacement of the metal from the outer sections of the
pad end is also maintained until valve guides of the desired height
are formed. Valve guide height and thickness dimensions and control
are achievable which have not been attainable by prior art
methods.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a perspective view of a cam engaged roller
follower U-shaped rocker arm intermediate formed from sheet metal
that has been bent to a U-shape cross-section and prior to the
creation thereon of the guide walls.
[0011] FIG. 2 is a cross-section taken along line A-A of FIG.
1.
[0012] FIG. 3 is a perspective view of a cam engaged roller
follower rocker arm in which valve guide extensions have been
created by displacing metal from the outboard portion of the bottom
of the U-shaped rocker arm of FIG. 1 inwardly in accordance with
the method of the invention.
[0013] FIG. 4 is a cross-sectional view taken along line B-B of
FIG. 3.
[0014] FIG. 5 is a cross-sectional illustration of a typical die
tool used to horizontally displace metal inwardly at the bottom of
the U-shaped rocker arm prior to the formation on the bottom of the
rocker arm of the valve guides.
[0015] FIG. 6 is a view similar to that of FIG. 5 illustrating the
die following formation of the valve guides by the horizontal
inward displacement of the metal at the bottom of the pad end
U-shape rocker arm intermediate of the kind illustrated by FIG.
1.
[0016] FIG. 7 is a perspective view of an alternative rocker arm
type, i.e., a flat rocker arm, for which guide walls can be created
in accordance with the invention.
[0017] FIG. 8 is a perspective view of yet another form of rocker
arm, a center pivot rocker arm, for which guide walls can be
created in accordance with the method of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0018] A rocker arm body 10 made by forming a steel flat blank into
a U-shape cross-section comprising sidewalls 12 and 13 connected by
a pad end 14 and a socket end 15. As illustrated, the pad end 14 is
defined by a central section 16 and two outer surfaces 17 and 18
(FIG. 2) FIG. 4 is effected. The formation of the valve guide walls
22 by displacing material from the outer pad end surfaces 17 and 18
and forcing it inwardly or centrally towards surface 16. This
creates new surfaces 17a and 18a which are not aligned with valve
contact central surface 16. The valve contact area defined by
surface 16 and sides 20 of the formed valve guides 22 is created by
a tool having a width to accept a known valve stem diameter. The
valve guide walls 22 are parallel and offset to the sidewalls 23
and 24 and are defined by outer and inner surfaces 19 and 20,
respectively, and are formed so as to have a proper thickness to
survive in its application. The top, i.e., height, 21 of the valve
guide wall 22, as well as the thickness (measured from 19 to 20),
is determined by the amount of material displaced inwardly from
surfaces 17 and 18.
[0019] Referring now to FIGS. 5 and 6, an embodiment of a stamping
die 40 for forming valve guides 42 (FIG. 6) is illustrated to
include a center post tool of a size to accommodate the desired
valve size. A pair of metal displacing cams 46 having an edge
devised to displace metal inwardly from the outer surfaces of the
pad end of the rocker arm. Center post 44 is illustrated to include
a valve guide forming surface 48.
[0020] As shown in FIG. 6, stamping die 40 has the rocker arm 10
positioned therein after the metal displacement operation has
formed valve guides 42. In accordance with the method of the
invention, a U-shaped rocker arm intermediate (without valve
guides) is shaped from a metal blank. The pad end of the U-shaped
intermediate is then subjected to the valve guide creating method
of the invention.
[0021] In the valve guide formation (FIGS. 5 and 6) projections 42
are formed by displacing the adjacent lower surfaces inwardly from
the outboard portion of the pad end of the U-shaped rocker arm
intermediate metal blank 10 while minimizing any change to the
cross-sectional thickness of the intermediate 16 (FIG. 4) of the
pad and that doesn't include projections.
[0022] At the completion of this stamping step, the valve guide
projections 22 (shown as 42 in FIG. 6) are formed due to the
displacement of material from the outboard portion of the rocker
arm pad end by the lateral converging arms at end 43 of the rod 40,
FIGS. 5 and 6.
[0023] According to the invention, as illustrated in FIG. 7, the
creation of the valve guides 73 and 74 on the flat rocker arm 70 is
performed by displacing material from the lower outboard surface
toward the center post 44 (FIG. 5). As the material is displaced it
is deformed to create the valve guide projections 73 and 74. The
displacement of material at the bottom outboard area at the pad end
of the U-shaped rocker arm continues until sufficient quantity of
material flows to form the guides 73 and 74 of desired height and
thickness. The process creates displaced surfaces 17a and 18a (FIG.
4).
[0024] As best seen in FIG. 5, distance X, between projection
forming recesses used in working the intermediate article, is
greater than the width of center post 44 used to determine the
desired valve dimension.
[0025] The pad end metal displacement process of the invention
results in a minimum of approximately 65% of the sheet metal stock
thickness being maintained across the displaced pad end areas 17a
and 18a so as not to create a through harden heat treat condition
in the displaced areas. The stock thickness is the original
thickness of the sheet metal blank as measured from upper surface
16 to lower surface 16a (FIG. 2). It is desired to maintain a
minimum thickness of the resulting rocker arm in the displace areas
17a and 18a. The minimum required thickness for the rocker arm in
the displaced areas 17a and 18a is determined by the depth of
hardening experienced by rocker arm 10 in a post-forming hardening
treatment and the desired soft core thickness. A rocker arm with a
hardened surface and soft core is typically desired for purposes of
durability and wear resistance. In the embodiment shown, the
post-forming hardening treatment will harden the rocker arm to a
depth of about 0.02 inches measured from all surfaces.
[0026] In the rocker arm 70, illustrated in FIG. 7, the method of
the invention is adaptable to form valve guides 73 and 74 at the
pad end 72 of the rocker arm 70.
[0027] Similarly, with reference to FIG. 8, which illustrates a
center pivot type of rocker arm 80, the invention is generally
applicable in forming valve guides 83 and 84 at the pad end 82 of
rocker arm 80.
[0028] While the invention has been described with respect to
specific examples including preferred modes of carrying out the
invention, those skilled in the art will appreciate that there are
numerous variations and permutations of the above described systems
and techniques that fall within the spirit and scope of the
invention as set forth in the appended claims. For example, while
valve guide walls are illustrated, another form of the guides may
also be useful at the pivot end.
* * * * *