Rocking press machine

Details Rocking press machine Rocking press machine

1999-06-08

2002-10-01

Larson, Lowell A. (Department: 3725)

Metal deforming

By use of tool acting during relative rotation between tool...

C072S406000

Reexamination Certificate

active

06457339

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to rocking press machines having rocking shafts that are capable of various swinging motions.
The rocking press machine is a machine that forges metal by means of a combination of a rocking shaft and a metal die. The lower segment of the rocking press comprises a hydraulic press that supports the pressure exerted by the rocking shaft and carries a metal stock to be forged and other devices.
The basic principle of the rocking press machine is to allow the rocking shaft
1
to swing about the central axis thereof with an adjustable angle of eccentricity and an adjustable orbital angular velocity, as shown in FIG.
2
. Then, the metal die
2
integral with the rocking shaft
1
swings and thereby forges the metal placed therebelow into a desired shape.
Various swinging motions are attained by varying the angle of eccentricity and orbital angular velocity of the rocking shaft about its own central axis, whereby the metal stock pressed by the metal die
2
is formed into various shapes.
With conventional rocking press machines, the rocking shaft
1
and the metal die
2
therebelow are in one piece. Furthermore, the metal die
2
is shaped like a truncated cone having vertex O at the bottom end thereof, as shown in FIG.
1
.
When the working face of the metal die
2
of conventional rocking press machines of this type has line contact with the metal stock or, in other words, the angle of eccentricity &thgr; the central axis of the rocking shaft
1
is equal to the angle of inclination a of the metal die
2
shaped like a truncated cone as shown in
FIG. 1
, the metal die rolls over the surface of the metal stock about vertex O as the central axis of the rocking shaft
1
moves in orbit.
If the angular velocity of the orbiting central axis of the rocking shaft
1
with respect to the vertical axis is &ohgr; and the angular velocity of the central axis of the metal die
2
rotating on its own axis is &ohgr;′ in
FIG. 1
, the vertical and horizontal components of the angular velocity &ohgr;′ are &ohgr;′ cos &agr; and &ohgr;′ sin &agr;, respectively.
If the distance between a specific point P of the metal die
2
that is rolling in contact with the metal stock and vertex O is r and the intersection point between a line perpendicular to the horizontal surface at point P and the central axis of the metal die
2
is S in
FIG. 1
, SP=rcot &agr;.
The orbital speed at point P is &ohgr;r.
When the metal die
2
that rolls as described before rotates on its own axis about vertex O, the rotating speed of the horizontal component &ohgr;′ sin &agr; of the angular velocity &ohgr;′ at point X and with the orbital speed at point P given above, which can be expressed as SP &ohgr;′ sin &agr;=r&ohgr;′ cos &agr; where SP is the radius, is equal to &ohgr;r described earlier.
Therefore, equations or &ohgr;r=&ohgr;′r cos &agr; and &ohgr;′=&ohgr;/cos &agr; hold.
However, the rotation of the metal die on its own axis, resulting from its rolling, produces considerable interference in forming a desired pattern on the metal stock by various swinging motions.
To explain the above fact,
FIG. 2
shows a view that is more generalized than FIG.
1
. That is,
FIG. 2
shows a case in which the angle of eccentricity &thgr; of the central axis of the rocking shaft
1
is not equal to the angle of inclination &agr; of the metal die
2
or, in other words, the metal die shaped like a truncated cone is not in contact with the surface of the metal stock being worked. Here, a normal line extending from point P on the surface of the conically shaped lower part of the metal die intersects the central axis thereof at point Q, and OQ=a and PQ=b. (Unlike
FIG. 1
,
FIG. 2
shows a case in which the conically shaped part of the metal die is away from the horizontal plane.)
When the metal die rotates on its own axis, point P will become separated from the surface of the metal stock in some instances. P′ and Q′ in
FIGS. 2 and 3
are projections of points P and Q on the abscissa and ordinate in a horizontal plane centered at vertex O. OP′ and OQ can be expressed as follows:
OQ′=a
sin &thgr;(
t
) and
P′Q′=b
cos &thgr;(
t
)
(A functional form &thgr;(t) is used because &thgr; can change with time.)
In
FIG. 2
, point Q rotates about a vertical line passing through vertex O with angular velocity &ohgr;, whereas point P rotates not only about the same vertical line passing, through vertex O with angular velocity &ohgr; but also in the opposite direction about a vertical line passing through point Q with an angular velocity equal to the vertical component of angular velocity &ohgr;′ of the rotation of the rocking shaft on its own central axis.
When &thgr;=&agr;, &ohgr;′=&ohgr;/cos &agr; as described earlier by reference to FIG.
1
. The inclined surface of the metal die shaped like a truncated cone is away from the surface of the metal stock as shown in FIG.
2
. However, &ohgr;′ is not always equal to &ohgr;/cos &agr; because of the rotation on its own axis due to the inertia effect of the rolling motion.
The vertical component of angular velocity &ohgr;′ of the rotation of the rocking shaft on its own central axis is equal to &ohgr;′ cos &thgr;(t), as is evident from FIG.
2
.
Therefore, the velocity of angular motion in the vertical direction at point Q represents a value obtained by deducting the vertical component of angular velocity due to the rotation on its own axis &ohgr;′ cos &thgr;(t) from angular velocity &ohgr; of the orbiting central axis.
Thus, coordinates x and y of point P′ in
FIG. 3
can be expressed by the following equations:
x=a
sin &thgr;(
t
)cos &ohgr;
t+b
cos &thgr;(
t
)cos(&ohgr;−&ohgr;′ cos &thgr;(
t
))
t
y=a
sin &thgr;(
t
)sin &ohgr;
t+b
cos &thgr;(
t
)sin(&ohgr;−&ohgr;′ cos &thgr;(
t
))
t
The following equation can be derived from equation (1):
x
2
+y
2
=a
2
+b
2
+ab
sin 2&thgr;(
t
)cos(cos&thgr;(
t
))
t
  (2)
x
2
+y
2
cannot be kept constant because cos (−&ohgr;′ cos &thgr;(t)) t in equation (2) changes successively even if &thgr;(t) remains constant.
This means that accurate control required in producing a circular motion that is, the most basic motion in swinging motions is impossible to achieve, let alone accurate control to ensure accurate production of more complex spiral or daisy motion.
FIG. 1
shows a condition in which the inclined surface of the metal die rolls in contact with the surface of the metal stock. If it is assumed that the time for point P to start rolling from a condition in which it is in contact with the metal stock being worked and come in contact with the same metal stock again is t
0
, equation &ohgr;′t
0
=2&pgr; holds. Then, the angle of rotation of point P in a horizontal plane is &ohgr;′t
0
=2&pgr;cos &agr;. Therefore, it is impossible to hold the surface of the metal stock within an angular limit of 2&pgr;(1−cos &agr;).
Even if an attempt is made to obtain a desired pattern by pressing the surface of the metal stock with point P at intervals of t
0
, it is impossible to accurately form the desired pattern because of the shift mentioned earlier.
The object of this invention is to provide rocking press machines whose metal dies do not rotate on their own axes by eliminating the shortcomings of conventional rocking press machines whose metal dies rotate on their own axes.
SUMMARY OF THE INVENTION
This invention eliminates the shortcomings of conventional rocking press machines described earlier by providing the following improvement:
(1) In a rocking press machine comprising a metal die adapted to swing about a vertex at a lower end thereof and a rocking shaft mounted above the metal die and transmitting a swinging motion to the metal die, with an angle of eccentricity of the central axis

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