Press machine

A press machine comprising: a slider which reciprocates between its top dead point position and bottom dead point position; a stationary bolster; a position adjusting mechanism for adjusting an up-and-down relative position between the slider and the bolster; a bottom dead point position detecting mechanism for detecting a position of the slider held in the bottom dead point position; a moving body on which the bottom dead point position detecting mechanism is supported and which is movable in the directions in which the slider reciprocates; and a follow-up mechanism connected to the position adjusting mechanism so that the moving body can follow up a position adjustment movement of the slider, the bottom dead point position detecting mechanism being moved so that it can follow up the position adjustment movement of the slider.

FIELD OF THE INVENTION 
The present invention relates to press machines, and more particularly to 
such machines which have the function of adjusting a so-called "die 
height" which is the up-and-down relative position between the slider and 
the bolster. 
DESCRIPTION OF THE PRIOR ART 
In press machines, the position of the slider in its bottom dead point 
tends to change due to the fluctuation in the slider strokes and the 
thermal expansion of the components. Consequently, a so-called "die 
height", that is, the up-and-down relative position between the slider and 
the bolster, changes. It is known that the die height change has an 
adverse effect on final products. It is possible that the die height 
change resulting from the stroke fluctuation is prevented by increasing 
the work accuracy and thus making the stroke fluctuation small. Also, it 
is possible that the die height change resulting from the thermal 
expansion of the components is prevented by circulating a large number of 
oils through the press machine and thus restraining the temperature rise 
to the components. However, in such a case, the circulation of oil and the 
temperature control require substantial power and are expensive. For this 
reason, in order to prevent the die height change in consideration of 
economic aspects, there has been proposed a press machine provided with a 
position adjusting mechanism for adjusting the up-and-down relative 
position between the slider and the bolster, that is, the die height. 
In such a press machine with a position adjusting mechanism, a bottom dead 
point position detector for detecting the position of the slider in its 
bottom dead point is provided to adjust the die height. The bottom dead 
point position detector is supported on an attachment bracket which is 
detachably attached on the frame of the press machine by setscrews. The 
bottom dead point position detector detects the slider position in the 
bottom dead point from the distance change between the position detector 
and a detection body fast on the slider. Since it is necessary to detect 
the position of the bottom dead point in microns, the space between the 
bottom dead point position detector and the detection body on the slider 
in the bottom dead point is held within a microscopic distance of about 1 
mm. 
Also, the position adjusting mechanism is also used for the die height 
adjustment in exchanging the die for a different high one. In that case, 
the die height adjustment is made by the reading value of an additional 
counter instead of the bottom dead point position detector. The adjusting 
amount of the die height adjustment at that time is normally greater than 
the space between the bottom dead point position detector and the 
detection body. For this reason, after the bottom dead point position 
detector has been moved by loosening the setscrews of the attachment 
bracket, the die height is adjusted by the manipulation bottom for 
operating the position adjusting mechanism. After the die height 
adjustment, the bottom dead point position detector is again attached to a 
predetermined position. 
Furthermore, the die height adjustment is needed also when the press 
machine is started again, because the temperature of the press machine 
falls after the stop of the pressing operation. That is, although the 
slider is held in the top dead point position during the stop of the 
pressing operation, the slider position in the top dead point changes 
because of the temperature fall of the components after the stop of the 
operation. If with that condition the press machine is started, the 
position of the bottom dead point will change since the stroke of the 
slider does not change. It is therefore required that a top dead point 
position detector is provided for detecting the position of the slider in 
its top dead point, and that, immediately before the pressing operation is 
started again, the die height adjustment is made in accordance with the 
detection results of the top dead point position detector by the position 
adjusting mechanism. 
However, in the conventional press machine in which the bottom dead point 
position detector is fixed to the frame through the attachment bracket, if 
it is forgotten to loose the setscrews of the attachment bracket and move 
the bottom dead point position detector when the position adjusting 
mechanism is operated, the bottom dead point position detector contacts 
with the detection body and is thus damaged. In addition, since it is 
necessary to attach the bottom dead point position detector to a 
predetermined position after the die height adjustment, there was the 
drawback that the positioning operation is troublesome. Note that, in the 
case where a top dead point position detector is provided, there is the 
possibility that the above described drawbacks also occur in the top dead 
point position detector. 
Accordingly, it is an object of the present invention to provide an 
improved press machine which can eliminate the trouble of the positioning 
of the bottom dead point position detector after the die height adjustment 
and prevent the damage to the bottom dead point position detector caused 
by the error of working process. 
SUMMARY OF THE INVENTION 
In accordance with an important aspect of the present invention, there is 
provided a press machine comprising: a slider which reciprocates between 
its top dead point position and bottom dead point position; a stationary 
bolster; position adjusting means for adjusting an up-and-down relative 
position between the slider and the bolster; bottom dead point position 
detecting means for detecting a position of the slider held in the bottom 
dead point position; a moving body on which the bottom dead point position 
detecting means is supported and which is movable in the directions in 
which the slider reciprocates; and follow-up mean connected to the 
position adjusting means so that the moving body can follow up a position 
adjustment movement of the slider, the bottom dead point position 
detecting means being moved so that it can follow up the position 
adjustment movement of the slider. 
In addition, the bottom dead point position detecting means may be 
detachably supported on the moving body, and a position at which the 
bottom dead point position detecting means is attached to the moving body 
may be changeable. 
In addition, the follow-up means may comprise a worm driven by the position 
adjusting means, a worm wheel meshing with the worm, and a screw shaft 
extending parallel to the reciprocating direction of the slider and 
meshing with an internal screw bore formed in the moving body and 
connected to the worm wheel so as to rotate with the worm wheel. 
Furthermore, the press machine may further comprise top dead point position 
detecting means attached to the moving body for detecting a position of 
the slider held in the top dead point position. 
In the present invention, if the up-and-down relative position between the 
slider and the bolster is adjusted by the position adjusting means, the 
bottom dead point position means, together with the moving body, are then 
moved by the follow-up means, so that the bottom dead point position means 
follows up the position adjustment movement of the slider. 
Consequently, when a die height adjustment is made in exchanging dies, it 
is not necessary to move the bottom dead point position means. As a 
result, since it is not necessary to set the bottom dead point position 
detector to a predetermined position after the die height adjustment is 
complete, the trouble caused by the position adjustment can be eliminated, 
and the damage to the bottom dead point position detector resulting from 
the error of working processes can be prevented. 
In addition, the bottom dead point position detecting means may be 
detachably supported on the moving body, and a position at which the 
bottom dead point position detecting means is attached to the moving body 
may be changeable. Therefore, the present invention can be used even in 
the case where the stroke of the slider is required to be changed when the 
dies are exchanged. 
Furthermore, the follow-up means may comprise a worm driven by the position 
adjusting means, a worm wheel meshing with the worm, and a screw shaft 
extending parallel to the reciprocating direction of the slider and 
meshing with an internal screw bore formed in the moving body and 
connected to the worm wheel so as to rotate with the worm wheel. 
Consequently, the structure of the follow-up mechanism can be made simple, 
thereby reducing the cost of the press machine. 
In addition, even if the top dead point position means is attached to the 
moving body, the present invention can have the above described 
advantages, as in the case of the bottom dead point position means.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
A preferred embodiment of a press machine according to the present 
invention will hereinafter be described in detail in conjunction with the 
accompanying drawings. 
In FIGS. 1 through 6, reference numeral 1 denotes a slider which is 
reciprocated between its top dead point position and bottom dead point 
position by cranks, links and cams (not shown). The reciprocating motion 
of the slider 1 is guided by a guide rod 2, which is inserted through the 
slider 1 and attached to a frame 3. A bolster 5 is fixedly mounted on the 
bed surface 4 of the frame 3 located immediately under the slider 1, and 
has a lower die 6 detachably mounted thereon. An upper die 7 is detachably 
mounted on the lower surface of the slider 1. The upper and lower dies 6 
and 7 are driven to compress and shape a workpiece by the reciprocating 
motion of the slider 1. Reference numerals 8 and 8 are a pair of plungers 
which are connected to cranks (not shown). The lower ends of the plungers 
8 are connected through pins 9 with the upper ends of upper screw rods 10, 
respectively. As shown in FIGS. 1 and 2, lower screw rods 12 are fixedly 
mounted on the upper surface of the slider 1 immediately under the upper 
screw rods 10 by a plurality of bolts 11. That is, the lower screw rods 12 
are arranged coaxially with the upper screw rods 10. As shown in FIG. 2, 
the upper and lower screw rods 10 and 12 are respectively formed at the 
outer surfaces thereof with inverse screws. In the embodiment of FIG. 2, 
the upper screw rods 10 are each formed at their outer surface with a 
right-handed screw 13, and the lower screw rods 12 are each formed at 
their outer surface with a left-handed screw 14. Reference numeral 15 is a 
cylindrical inner race, which is formed at its upper inner surface with a 
right-handed screw 16 and at its lower inner surface with a left-handed 
screw 17. The upper screw rod 10 is inserted in the upper portion of the 
inner race 15 so that the right-handed screws 13 and 16 mesh with each 
other, and the lower screw rod 12 is inserted in the lower portion of the 
inner race 15 so that the left-handed screws 14 and 17 mesh with each 
other. As a result, the upper and lower screw rods 10 and 12 are connected 
through the inner race 15 with each other. The upper screw rod 10, lower 
screw rod 12 and inner race 15 as a whole constitute an adjusting screw 
shaft 18. Reference numerals 19 and 19 are a pair of generally cylindrical 
cases, which are fixedly mounted in the frame 3 by a plurality of bolts 
20. Each case 19 surrounds the inner race 15. Within the cases 19 are 
inserted rotating bodies 21, which are each formed at their upper end 
portion integrally with a worm wheel 22 with its lower face received on 
the upper end face of the case 19. A cover 24 is fixedly mounted on the 
upper end face of the worm wheel 22 by a bolt 23. Reference numeral 25 is 
an outer race which is inserted within the rotating body 21, and the outer 
race 25 is attached through a key 26 to the rotating body 21 so that the 
outer race 25 can rotate with the rotating body 21. Between the inner and 
outer races 15 and 25 there are interposed a plurality of balls 27 which 
are mounted in part in the outer race 25. The balls 27 allow the inner 
race 15 to axially move within the outer race 25. As shown in FIG. 3, the 
inner race 15 is formed at its outer surface with a plurality of 
transmission projections 28 axially extending and spaced apart 
equidistantly in the circumferential direction of the inner race 15. Also, 
a plurality of transmission balls 29, which are mounted in part in the 
outer race 25, contact with the opposite side faces of the transmission 
projections 28. Consequently, the transmission balls 29 transmit the 
rotations of both directions of the rotating body 21 and outer race 25 
accurately to the inner race 15 to rotate the inner race 15. 
As shown in FIG. 4, reference numeral 30 is a transmission shaft which is 
rotatably supported through a bearing 31 on the frame 3. The transmission 
shaft 30 has a bevel gear 32 fixedly mounted on its one end and a bevel 
gear 33 fixedly mounted on its central portion. Also, the transmission 
shaft 30 is provided at the other end with a handle manipulation portion 
34 on which a handle (not shown) is mounted. As shown in FIG. 4, the frame 
3 supports an input shaft 35 and an output shaft 36 through bearings 37 
and 38, respectively. The input and output shafts 35 and 36 are axially 
aligned with each other and are perpendicular to the transmission shaft 
30. Between the input and output shafts 35 and 36 there is interposed a 
clutch 39 which has its input end coupled to the input shaft 35 and its 
output end coupled to the output shaft 36. Between the input and output 
ends of the clutch 39 there are provided a friction plate (not shown) and 
an electromagnetic device (not shown) to connect and disconnect the input 
and output shafts 35 and 36 by operation of the clutch 39. A bevel gear 40 
is fixedly mounted on the end of the output shaft 36 opposite the clutch 
39, and meshes with the bevel gear 33 on the transmission shaft 30. A spur 
gear 41 is fixedly mounted on the end of the input shaft 35 opposite the 
clutch 39, and meshes with a spur gear 43 fixedly mounted on the drive 
shaft of a motor 42, which is fixedly mounted on the frame 3. The motor 42 
is connected to a control part M and driven by the control part M. Two 
bearing cases 44 are mounted on the frame 3 adjacent the cases 19, and 
have a horizontal worm shaft 46 rotatably supported thereon through 
bearings 45. The horizontal worm shaft 46 extends perpendicular to both 
the upper screw rods 10 and the transmission shaft 30. The worm shaft 46 
is provided at its central portion with a bevel gear 47 meshing with the 
bevel gear 32 of the transmission shaft 30. The output shaft 36, 
transmission shaft 30 and horizontal worm shaft 46 as a whole constitute a 
drive shaft 48. The input shaft 35, spur gears 41, 43, and motor 42 as a 
whole constitute a motor driving part 49. The horizontal worm shaft 46 has 
fixedly mounted thereon a pair of worms 00 respectively meshing with the 
worm wheels 22. The worms 50 rotate with the drive shaft 48 by rotation of 
the drive shaft 48. The drive shaft 48 is rotated by the manual 
manipulation of the handle manipulation portion 34 of the transmission 
shaft 30 or by the motor drive of the motor driving part 49. It is 
necessary to switch the clutch 39, depending on the manual manipulation or 
motor drive. The rotations of the worms 50 are reduced with a high ratio 
by the worm wheels 22 meshing with the worms 50, and then transmitted 
through the outer race 22 and transmission balls 29 to the inner race 15 
of the adjusting screw shaft 18. This causes the lower screw rods 12 and 
accordingly the slider 1 to go up and down. Consequently, the up-and-down 
relative position between the slider 1 and the bolster 5, that is, the 
"die height" is adjusted. If, for example, the transmission shaft 30 is 
rotated in the direction A of FIG. 4, then the worm shaft 46 rotates in 
the direction B, the worm wheels 22 rotate in the direction C, the inner 
races 15 rotate in the direction D of FIG. 2 and move down in the 
direction E, and the slider 1 moves down in the direction E. 15 
revolutions of the horizontal worm gear 46 cause the slider 1 to move 1.5 
mm. 
Thus, the above described drive shaft 48, worms 50, worm wheels 22, outer 
races 25, transmission balls 29, adjusting screw shafts 18 and motor 
driving part 49 as a whole constitute a position adjusting mechanism 52 
which adjusts the up-and-down relative position between the slider 1 and 
the bolster 5, that is, the "die height". 
Also, the horizontal worm shaft 46 extends through the bearing case 45 and 
the frame 3, and has its one end connected with a counter 54 which 
indicates the amount of rotation of the worm shaft 46 (amount of die 
height). A pulley 53 is fixedly mounted on the worm shaft 46 between the 
bearing case 45 and the counter 54. 
As shown in FIGS. 1 and 6, reference numeral 55 denotes a bottom dead point 
position detector 55, which is a displacement sensor of the eddy current 
type which detects displacement of several microns and outputs an analog 
signal of several mVs. Reference numeral 56 is a detection body fixed on 
the slider 1 by bolts 57. The bottom dead point position detector 55 is 
provided at a position spaced apart about 1 mm from the detection body 56 
when the slider 1 is in its bottom dead point. The bottom dead point 
position detector 55 detects the position of the slider 1 held in the 
bottom dead point and then outputs an electric signal proportional to the 
detected displacement to the control part M. Reference numeral 58 is a top 
dead point position detector which is the same displacement sensor as the 
bottom dead point position detector 55. The top dead point position 
detector 58 is provided at a position spaced apart about 1 mm from the 
detection body 56 when the slider 1 is in its top dead point. The top dead 
point position detector 58 detects the position of the slider 1 held in 
the top dead point and then outputs an electric signal proportional to the 
detected displacement to the control part M. 
Note that the control part M has a function of automatically adjusting the 
"die height" during the operation or stop of the press machine by driving 
the motor driving part 49 in response to the electric signals from the 
bottom dead point position detector 55 and top dead point position 
detector 58. 
That is, during the pressing operation, the up-and-down relative position 
between the slider 1 and the bolster 5 changes due to the thermal 
expansion of the components and therefore the die height shifts from an 
appropriate value. At this time, the control part M detects the direction 
and amount of displacement of the up-and-down relative position with the 
electric signal from the bottom dead point position detector 55. Based 
upon the detected result, the control part M drives the motor driving part 
49, thereby adjusting the die height to an appropriate value. This 
adjustment of the die height is made every several strokes of the pressing 
operation. 
In addition, during the stop of the pressing operation in which the slider 
1 is in its top dead position, the up-and-down relative position between 
the slider 1 and the bolster 5 changes due to the temperature fall after 
the stop of the pressing operation and therefore the die height shifts 
from an appropriate value. At this time, the control part M detects the 
direction and amount of displacement of the up-and-down relative position 
with the electric signal from the top dead point position detector 58. 
Based upon the detected result, the control part M drives the motor 
driving part 49, thereby adjusting the die height to an appropriate value. 
This adjustment of the die height is made immediately before the pressing 
operation is started again. Note that when the die height adjustment is 
made, the input and output shafts 35 and 36 are coupled together by the 
clutch 39. In addition to the above described die height adjustment 
required during the pressing operation and the stop of operation, the dies 
height adjustment is also required in exchanging dies. In this adjustment 
in exchanging die, the handle manipulation portion 39 and a manipulation 
bottom (not shown) provided in the control part M are used. The drive of 
the motor driving part 49 is also controlled by an ON and OFF of the 
manipulation bottom of the control part M. The processes of this die 
height adjustment will be described later. 
As shown in FIG. 6, the bottom dead point position detector 55 is supported 
through an attachment member 59 on a moving body 61. The moving body 61 is 
disposed so that it can move in the directions in which the slider 1 
reciprocates. That is, a guide rod 62 extending in the up and down 
directions in which the slider 1 reciprocates is inserted in the moving 
body 61 through a thrust bush 63, so that the moving body 61 can move 
along the guide rod 62 in the directions in which the slider 1 
reciprocates. The guide rod 62 has a threaded portion at its lower end, 
and is fixed to a case 64 by a nut 65 meshing with the threaded portion. 
The case 64 is fixedly mounted on the frame 3 by a plurality of bolts 67. 
Also, the attachment member 59 is detachably mounted on the moving body 61 
by a bolt 68, and the moving body 61 is formed with screw bores 69a and 
69b into which the bolt 68 can be screwed. The screw bores 69a and 69b are 
spaced apart in the up and down directions so that the mounting position 
of the bottom dead point position detector 55 on the moving body 61 can be 
changed. A screw shaft 71 extending parallel to the reciprocating 
direction of the slider 1 meshes with the internal screw bore formed in 
the moving body 61, and is supported on the case 64 through bearings 73 
and 74. The screw shaft 71 has a worm wheel 78 mounted on its one end 
through a key 75 and a nut 76 so that the shaft 71 can rotate with the 
worm wheel 78. A spring 79 is interposed between the moving body 61 and 
the case 64 to prevent the backlash between the screw shaft 71 and the 
moving body 61. As shown in FIG. 5, the worm wheel 78 connected with the 
moving body 61 meshes with a worm 80 fast on a worm shaft 81. The worm 
shaft 81 is freely rotatably supported on the case 64 through bearings 82 
and 82. A driven pulley 86 is fixed on one end of the worm shaft 81 by a 
nut 84. As shown in FIGS. 1, 4 and 5, the driven pulley 86 fast on the 
worm shaft 81 and the drive pulley 53 fast on the worm shaft 46 are 
connected together through an endless belt 87 with teeth so that the 
rotation of the worm shaft 46 can be transmitted to the worm shaft 81. The 
rotational speed of the worm shaft 46 is the same as that of the worm 
shaft 81, and the speed reduction ratio between the worm 80 and the worm 
wheel 78 is 1/15. The screw portion of the screw shaft 71 meshing with the 
moving body 61 is a right-handed screw with a pitch of 1.5 mm, and one 
turn of the screw shaft 71 causes the moving body 61 to move 1.5 mm in the 
directions in which the slider 1 reciprocates. If, for example, the worm 
shaft 46 makes 15 revolutions in the direction B of FIG. 4, the moving 
body 61 will move 1.5 mm in the direction G of FIG. 6. The amount and 
direction of the movement of the moving body 61 are the same as those of 
the slider 1 when the worm shaft 46 makes 15 revolutions in the direction 
B of FIG. 4. The same is true of the case that the worms shaft 46 rotates 
in the reverse direction. Thus, the above described guide rod 62, thrust 
bush 63, case 64, screw rod 71, worm wheel 78, worm 80, worm shaft 81 and 
driven pulley 86 as a whole constitute a follow-up mechanism 88 which is 
connected to the position adjusting mechanism 52 so that the moving body 
61 can follow the movement of position adjustment of the slider 1. 
The processes of the die height adjustment at the time the dies are 
exchanged will hereinafter be described. 
When the upper and lower dies 7 and 6 are exchanged for dies of different 
height, it will be necessary to adjust the die height. Since an 
appropriate height has been known from the dimensions of the upper and 
lower dies 7 and 6, the slider 1 is moved in the proximity of an 
appropriate die height by driving the motor driving part 49 with the 
manipulation bottom of the control part M, while confirming the indication 
of the counter 54. The slider 1 is further moved by driving the drive 
shaft 48 by the manual manipulation of the hand manipulation part 34 of 
the transmission shaft 30, and is stopped at the position of the die 
height corresponding to the dies. The amount of the die height at that 
time is indicated in the counter 54, and the die height adjustment is 
complete. Note that, during the die height adjustment, the clutch 39 is 
operated in accordance with a changeover of the motor driving part 49 to 
the handle manipulation portion 34 or a changeover of the handle 
manipulation portion 34 to the motor driving part 49. In addition, the die 
height adjustment operation described above may also be made only by the 
manual manipulation of the handle manipulation portion 34. 
When in the above described die height adjustment operation the slider 1 is 
moved, the moving body 61 is driven by the drive shaft 48 and moves the 
same amount as the movement of the slider 1 in the same direction, thereby 
following up the movement of the slider 1. For this reason, even if the 
slider 1 were moved in what manner, the relative positions between the 
bottom dead point position detector 55 and the detection body 56 and 
between the top dead point position detector 58 and the detection body 56 
would not change. Consequently, the detection body 56 on the slider 1 will 
not contact with the bottom dead point position detector 55 and the top 
dead point position detector 58, and therefore, it will not be necessary 
to move the bottom dead point position detector 55 and the top dead point 
position detector 58 prior to the die height adjustment operation. 
Therefore, damage of the bottom dead point position detector 55 and the top 
dead point position detector 58 resulting from the error of working 
processes such that the moving operation of the bottom dead point position 
detector 55 and the top dead point position detector 58 prior to the die 
height adjustment is forgotten, can be prevented. In addition, since it is 
not necessary to set the bottom dead point position detector 55 and the 
top dead point position detector 58 to a predetermined position after the 
die height adjustment is complete, the trouble caused by the position 
adjustment can be eliminated. 
In addition, in the embodiment described above, the bottom dead point 
position detector 55 is detachable with respect to the moving body 61. The 
attachment member 59 supporting the detector 55 can be attached to the 
moving body 61 by meshing the attachment bolt 68 with the screw bore 69a, 
and the attachment member 59 can also be attached to the moving body 61 by 
meshing the attachment bolt 68 with the screw bore 69b. For example, in 
the case of the attachment member 59 attached in the up side, the stroke 
of the slider 1 is 30 mm. In the case of the attachment member 59 attached 
in the down side, the stroke of the slider 1 is 40 mm. Therefore, the 
present invention can be used even in the case where the stroke of the 
slider 1 is required to be changed when the dies are exchanged. The stroke 
change of the slider 1 can be made by adjusting the amount of eccentric of 
the crank. 
Furthermore, since in the embodiment of the present invention the follow-up 
mechanism 88 comprises the worm 80, the worm wheel 78 and the screw shaft 
71, the structure of the follow-up mechanism 88 can be made simple, 
thereby reducing the cost of the press machine. 
Note that reference numerals 66, 77 and 85 (FIG. 6) are washers for the 
prevention of looseness of nuts, and 72 (FIG. 6) and 83 (FIG. 5) are stop 
rings. Reference numeral 89 (FIG. 6) denotes a stop ring for preventing 
the thrust bush 63 from axially moving with respect to the moving body 61, 
and reference numeral 90 (FIG. 5) denotes a bearing interposed between the 
slider 1 and the guide rod 2. 
In addition, instead of the thrust bush 63, a rolling bearing may be used 
between the moving body 61 and the guide rod 62. Also, the moving body and 
the guide rod 62 may be connected together by a ball spline engagement. 
Furthermore, the structure of the follow-up mechanism 88 is not limited to 
the embodiment of the present invention, but variations and modifications 
may be made.