Forming press of crankshafts

Details Forming press of crankshafts Forming press of crankshafts

1999-11-30

2001-04-24

Crane, Daniel C. (Department: 3725)

Metal deforming

By use of non-deforming work-gripping clamp and relatively...

By individually non-deforming clamps

C029S006010

Reexamination Certificate

active

06220072

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a forming press of crankshafts.
A one-piece crankshaft is forged in stages of closed die forging, twisting, and reshaping. Although the stage of closed die forging consists of the substages of preforming, rough closed die forging, finishing closed die forging, and trimming, all the four substages are being performed with a single forging press since it is required in all the four substages to apply pressure to the workpiece in only the downward direction. On the other hand, because the twisting stage and the reshaping stage require different pressing modes, the two stages were being performed with two different forging presses. However, because using two different forging presses for the two stages is disadvantageous in terms of equipment cost and man-hours, forming presses have recently been developed which, in a single unit, are capable of performing both the twisting and reshaping stages. The present invention relates to such a forming press.
A forming press of crankshafts is disclosed in the Japanese Examined Patent Publication No. 4640/H7 (1995), which is shown in FIG.
25
.
In the above forming press, a slide
106
is secured to the lower ends of the piston rods of piston cylinders
108
, which are mounted on the crown. An upper die holder
151
is secured to the bottom of the slide
106
. The upper section of a twisting die
101
and the upper section of a reshaping die
102
are fixed to the bottom of the upper die holder
151
. On the other hand, the lower sections of the twisting die
101
and the reshaping die
102
are mounted on a lower die holder
152
, which is mounted on the base of the forming press. The twisting die
101
and the reshaping die
102
are built in so that the upper and lower sections of the twisting die
101
and those of the reshaping die
102
join at one and the same height when the slide
106
comes down. When the slide
106
descends, a workpiece is caught between the upper and lower sections of the twisting die
101
and, at the same time, another workpiece in the reshaping die is pressed and reshaped. While the slide
106
is in its bottom position, the twisting oil-hydraulic cylinder
109
provided in the slide
106
contracts to lower push rods
171
penetrating the slide
106
and twist the workpiece in the twisting die
101
.
In this way, a workpiece can be reshaped in the reshaping die
102
and, at the same time, another workpiece can be caught between the upper and lower sections of the twisting die
101
. Then, the workpiece in the twisting die
101
can be twisted by contracting the twisting oil-hydraulic cylinder
109
, pushing down the push rods
171
, and thereby turning parts of the twisting die
101
anticlockwise and the other parts of the twisting die
101
clockwise.
In case of the above forming press, because the twisting oil-hydraulic cylinder
109
is disposed in the slide
106
, it is necessary for feeding hydraulic oil to the twisting oil -hydraulic cylinder
109
to use long flexible hoses
100
which cover the stroke of the slide
106
. Such configuration is not desirable for a high-speed production machine which requires a large flow of hydraulic oil, posing a large danger of hydraulic oil leaking from the long flexible hoses
100
, igniting from the heat of the hot forging, and causing a fire.
Besides, to bring the lower ends of the push rods
171
to the push-down arms
104
of movable retainers holding the twisting die
101
, the slide
106
has to allow the push rods
171
to penetrate itself. In this configuration, the following shortcomings occur.
(1) The adjustment and maintenance of the guiding parts of the push rods are difficult.
(2) Because the slide
106
is divided into three by the push rods
171
, its strength is reduced. To solve this problem, the height of the slide
106
has to be increased to recover its strength.
(3) Accordingly, the slide system (moving section) becomes heavy. Its large force of inertia impedes the control of high-speed cyclic operation.
One of the main objects of developing a forming press which performs both the twisting and reshaping stages is to achieve a high-speed operation. In case of the above forming press of the prior art, the object is difficult to achieve due to the reasons described in the above paragraphs (2) and (3). If the forming press achieves the object, it would present problems in forming precision and maintenance.
On the other hand, the twisting angle of such a forming press has to be changed in accordance with the types of crankshafts. The twisting angle varies depending on the numbers of cylinders, etc. of engines.
In conventional means for setting the twisting angle, stoppers are set, below the push rods, on the top of the bed to regulate the twisting angle. To shift the production from one type of crankshaft to another, stoppers have to be changed and adjusted to attain the twisting angle required by the latter.
Such stoppers have to be changed and adjusted by workers in accordance with twisting angles required by various types of crankshafts. Besides, because the space in the forming press is limited, the upper and lower die holders are usually taken out of the press in order to make fine adjustment of the stoppers. Accordingly, working efficiency is low.
Under the circumstances, another forming press is disclosed [Japanese Unexamined Utility Model Publication 104215/H4 (1992)]. The forming press has, under its bed, a driving mechanism which moves threaded shafts up and down to adjust the height of the stoppers.
However, because the driving mechanism is disposed under the bed, die lubricant and scale stick to the driving mechanism and hence it is liable to develop trouble. Besides, because the forming press has four stoppers, they require fine height adjustment among them. Therefore, the driving mechanism for adjusting the height of stoppers is very complex and expensive.
In accordance with the above, an object of the present invention is to provide a forming press of crankshafts of which the safety is high, of which the slide has large strength ensuring high precision, and which is capable of high-speed operation and inexpensive.
Another object of the present invention is to provide a forming press of crankshafts of which the twisting angle can be set freely and precisely, of which the construction is simple, and which is inexpensive to make and is capable of high-precision forming.
SUMMARY OF THE INVENTION
According to the first aspect of the present invention, there is provided a forming press of the crankshafts having a crown, a slide, a forging unit for twisting with a twisting die, and a forging unit for reshaping, wherein (i) a pressing oil-hydraulic cylinder and a lift-up oil-hydraulic cylinder for lowering and raising the slide and a twisting oil-hydraulic cylinder for twisting a workpiece in the forging unit for twisting are mounted on the crown, (ii) the piston rod of the twisting oil-hydraulic cylinder is connected to a pressing block, (iii) a twisting push rod is secured to each of the four corners of the pressing block, two of the four twisting push rods being disposed in front and back of the slide on the right side of the twisting die, the other two being disposed in front and back of the slide on the left side of the twisting die, and (iv) the lower ends of the two twisting push rods on each side of the twisting die are connected to each other by a twisting-down beam and an untwisting beam below the slide.
According to the second aspect of the present invention, there is provided the forming press of the first aspect, wherein the slide is of inverted T-form in section, the pressing block is of inverted U-form as seen from one side, and the slide and the pressing block are so disposed to each other that the former can enter the latter.
According to the third aspect of the present invention, there is provided the forming press of the second aspect, wherein (i) the pressing block comprises a guide shoe and a pair of block members secured to the front and the back o

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