Crank press

Details Crank press Crank press

1999-03-04

2001-01-30

Butler, Rodney A. (Department: 3725)

Metal deforming

With means to drive tool

With means to selectably control movement of tool

Reexamination Certificate

active

06178803

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates generally to a crank press, and more particularly to a crank press for forging and sheet metal processing.
FIG. 6
is an illustration of the basic structure of the so-called crank press. A crankshaft
1
is driven by an electric motor or the like and connected to a slider
3
by a connecting rod
2
. An upper metal mold is fixed to the bottom of the slider
3
, and a lower metal mold is fixed onto a bed (not shown). A work is put between the upper and lower metal molds and the slider
3
is lowered to forge or form the work into a certain shape.
Connected to the slider
3
are the piston rods
4
a
of a pair of balance cylinders
4
, and the cylinders
4
b
of the balance cylinders
4
are fed with compressed air from an accumulator
5
, to always exert upward force to the crankshaft
1
through the media of the slider
3
and connecting rod
2
. Under the condition, the crankshaft
1
is driven to move the slider
3
up and down through the medium of the connecting rod
2
.
In case of the general-purpose hot-forging crank press, the crankshaft
1
is stopped at its top dead center at the end of each cycle. To accomplish this, the conventional crank press is given a mechanism shown in FIG.
7
.
Coupled to an end of the crankshaft
1
is a brake
6
, which is controlled pneumatically by a brake control valve SV
1
and switched between the working and nonworking states. Besides, coupled to the other end of the crankshaft
1
are a clutch
7
and a flywheel
8
. The flywheel
8
is rotated by an electric motor
9
through the medium of a belt. The clutch
7
is controlled pneumatically by a clutch control valve SV
2
and switched between the states of engagement and disengagement.
Referring to
FIG. 6
,
7
and
8
, the operation of the above conventional crank press will now be described.
Now the slider
3
is at a stop at its top dead point. When a signal to initiate a pressing cycle is given, the brake control valve SV
1
releases the brake
6
, and then the clutch control valve SV
2
engages the clutch
7
. The electric motor
9
drives the crankshaft
1
, and the slider
3
begins to move down. When the slider
3
reaches its bottom dead point, the clutch control valve SV
2
disengages the clutch
7
, and the slider
3
moves upward by the inertia force of the turning parts. While the slider
3
is moving upward, the brake control valve SV
1
activates the brake
6
to stop and keep the slider
3
at its top dead point until the next pressing cycle is initiated.
By repeating the above process, the crank press operates continually, stopping the slider
3
at its top dead point at the end of every cycle.
In case of the above conventional crank press, a large capacity is required of the brake
6
in order to absorb instantaneously the large energy of the slider
3
, etc. and the pulling-up force of the balance cylinders
4
and stop the slider
3
at its top dead point. Besides, a large capacity is required of the electric motor
9
in order to cause the crankshaft
1
, etc. to begin to turn or move. Thus, in the conventional crank press, large energy has to be exerted and absorbed, or consumed, at the beginning and end of each pressing cycle, respectively.
In accordance with the above, the object of the present invention is to provide a crank press wherein energy is utilized effectively and, thereby, the load on the brake, the required capacity of the electric motor, and the overall noise level are reduced.
SUMMARY OF THE INVENTION
According to the first aspect of the present invention, there is provided a crank press, wherein the power of an electric motor is transmitted to a crankshaft and a connecting rod connected thereto through a clutch to lower a slider and a brake coupled to the crankshaft slows down and stops the ascending slider at its top dead point at the end of each cycle, comprising an energy absorbing/releasing means which (i) transforms part of the kinetic energy during the ascent of the slider into hydraulic energy and absorbs the transformed energy and (ii) releases and transforms the hydraulic energy into kinetic energy of the slider during the descent of the slider.
According to the second aspect of the present invention, there is provided a crank press according to the first aspect wherein the energy absorbing/releasing means comprises (i) an oil-hydraulic pump/motor which is coupled to the crankshaft through gears and receives and gives torque from and to the crankshaft, (ii) an accumulator which is connected to the oil-hydraulic pump/motor by an oil-hydraulic circuit, and (iii) a switching means which switches the energy absorbing/releasing means between an energy-absorbing mode to feed hydraulic oil to the accumulator through the oil-hydraulic pump/motor and an energy-releasing mode to feed hydraulic oil from the accumulator to the oil-hydraulic pump/motor.
According to the third aspect of the present invention, there is provided a crank press according to the second aspect wherein the switching means comprises a first switching valve and a second switching valve, both put in the oil-hydraulic circuit, each switchable between a first position to allow the accumulator and the oil-hydraulic pump/motor to communicate with each other and a second position to allow an oil tank and the oil-hydraulic pump/motor to communicate with each other.
According to the fourth aspect of the present invention, there is provided a crank press according to the first aspect wherein the energy absorbing/releasing means comprises (i) an oil-hydraulic pump/cylinder which receives and gives driving force from and to the crankshaft or the connecting rod, the piston rod of the oil-hydraulic pump/cylinder coupled to the crank pin of the crankshaft, or a portion, near the crank pin, of the crankshaft, or a portion, near the crank pin, of the connecting rod, (ii) an accumulator which is connected to the chambers of the oil-hydraulic pump/cylinder and a pair of balance cylinders by oil-hydraulic circuits, each chamber on the opposite side of the piston rod, and (iii) a switching means which switches the energy absorbing/releasing means between an energy-absorbing mode to feed hydraulic oil from the oil-hydraulic pump/cylinder to the accumulator and an energy-releasing mode to feed hydraulic oil from the accumulator to the oil-hydraulic pump/cylinder.
According to the fifth aspect of the present invention, there is provided a crank press, wherein the power of an electric motor is transmitted to a crankshaft and a connecting rod connected thereto through a clutch to lower a slider and a brake coupled to the crankshaft slows down and stops the ascending slider at its top dead point at the end of each cycle, comprising (i) an energy absorbing/releasing means which transforms part of the kinetic energy during the ascent of the slider into hydraulic energy and absorbs the transformed energy and releases and transforms the hydraulic energy into kinetic energy of the slider during the descent of the slider, and (ii) an oil-hydraulic circuit for the clutch, the oil-hydraulic circuit connected to the oil-hydraulic circuit constituting the energy absorbing/releasing means.
According to the sixth aspect of the present invention, there is provided a crank press, wherein the power of an electric motor is transmitted to a crankshaft and a connecting rod connected thereto through a clutch to lower a slider and a brake coupled to the crankshaft slows down and stops the ascending slider at its top dead point at the end of each cycle, comprising (i) an energy absorbing/releasing means which transforms part of the kinetic energy during the ascent of the slider into hydraulic energy and absorbs the transformed energy and releases and transforms the hydraulic energy into kinetic energy of the slider during the descent of the slider, and (ii) an oil-hydraulic circuit for a bottom knockout cylinder, the oil-hydraulic circuit connected to the oil-hydraulic circuit constituting the energy absorbing/releasing means.
The advantages offered by the first a

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