Apparatus for conveying lead frame

A lead frame conveying apparatus comprises a driving force converting unit for transmitting to a frame receiving arm a horizontal reciprocating linear motion of an elliptic motion of a timing belt placed over two timing pulleys between the centers of the timing pulleys and converting semicircular motions at both ends of the horizontal reciprocating linear motion into vertical reciprocating linear motions by employing rolling contact for absorbing the horizontal component thereof and transmitting the vertical reciprocating linear motion to the frame receiving arm so as to put the frame receiving arm into a rectangular motion. The apparatus thus requires only one induction motor as a driving device.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a lead frame conveying apparatus for 
conveying a lead frame between guide rails which are extended parallel. 
The present invention also includes a transverse conveying mechanism used 
in the lead frame conveying apparatus and a method of converting an 
elliptic motion performed in the transverse conveying mechanism into a 
rectangular motion. 
2. Description of the Related Art 
FIG. 5 is a perspective view showing a conventional apparatus for conveying 
a lead frame. In the drawing, a lead frame 1 is transferred between two 
guide rails 2 and 3 by a frame receiving arm 4. For example, when the lead 
frame 1 is transferred from the guide rail 2 to the guide rail 3, the 
frame receiving arm 4 is moved in the order of A-B-C-D shown by arrows in 
the drawing. The guide rails 2 and 3 comprise two rails 2a, 2b and 3a, 3b, 
respectively, which are extended parallel. A linear guide bearing 11a is 
slidably mounted on a liner guide rail 11 on a base block 21, a bearing 
block 20 being fixed to the linear guide bearing 11a through a holder 5. A 
shaft 6 is passed through a bearing hole (not shown) in the bearing block 
20 so as to connect the frame receiving arm 4 and a plate 7 and is fitted 
in the bearing hole so as to be axially slidable. The shaft 6 is provided 
at either side of the linear guide rail 11. The plate 7 has a lower end 
member 8 which is downwardly extended and on which a rolling bearing 9 is 
provided. An extension coil spring 10 interposed between the bearing block 
20 and the plate 7 produces the force to upwardly move a portion 
comprising the frame receiving arm 4, the shafts 6, the plate 7, the 
member 8 and the rolling bearing 9. A guide plate 13 is attached to two 
linear guide bearings 12a, 12b which are vertically slidable and which are 
provided on the base block 21 so that the guide plate 13 contacts with the 
rolling bearing 9 which is upwardly moved by the coil spring 10. Extension 
coil springs 10a, 10b are respectively provided between the guide plate 13 
and the base block 21 at both ends of the guide plate 13 so as to 
constantly generate the force to upwardly move the guide plate 12 (the 
coil spring 10a is not shown in FIG. 5). A rolling bearing 13a in rolling 
contact with a vertically moving cam 14 is provided at the center on the 
side of the guide plate 13, which is opposite to the side thereof engaged 
with the linear guide bearings 12a, 12b. The vertically moving cam 14 is 
eccentrically provided on the rotational shaft of a motor 16. A timing 
belt 18 placed over timing pulleys 19a , 19b is driven by a pulse motor 
17. The connecting member 20a provided on the bearing block 20 holds the 
timing belt 8 therein so as to connect the bearing block 20 and the timing 
belt 18. The base block 21 is fixed to a base plate 22. FIG. 6 is a side 
view showing the basic operation of the frame receiving arm 4 of the 
conventional frame conveying apparatus in the case where the lead frame 1 
is transferred from the guide rail 2 to the guide rail 3. When the lead 
frame 1 is conveyed to the guide rail 2 by an external apparatus (not 
shown), the frame receiving arm 4 positioned below the guide rail 2 is 
upwardly moved for scooping up the lead frame 1. The frame receiving arm 4 
is transversely moved from a position above the guide rail 2 to a position 
above the guide rail 3 while holding the lead frame 1. The frame receiving 
arm 4 is downwardly moved for placing the lead frame 1 on the guide rail 
3. The frame receiving arm 4 is then transversely moved from a position 
below the guide rail 3 to a position below the guide rail 2. The frame 
receiving arm 4 performs such a one-cycle motion. Each of the guide rails 
2 and 3 is partially cut off to form a space which allows the frame 
receiving arm 4 to scoop up the lead frame 1 on the guide rail and place 
the lead frame on the guide rail, as shown in FIG. 5. 
The operation of the conventional apparatus for conveying a lead frame is 
described below with reference to FIGS. 5 and 6. The frame receiving arm 4 
waits for the lead frame 1 at point A. When the lead frame 1 is fed to the 
guide rail 2, the motor 16 is driven, and the vertically moving cam 14 
eccentrically provided on the rotational shaft of the motor 16 is thus 
rotated. The rolling bearing 13a provided on the guide plate 13 is 
vertically moved while making rolling contact with the periphery of the 
vertically moving cam 14 by virtue of the coil springs 10, 10a, 10b in 
accordance with the distance between the portion of contact with the 
periphery of the vertically moving cam 14 and the rotational shaft. This 
causes the whole guide plate 13 to be vertically moved. When the motor is 
driven, and when the guide plate 13 is upwardly moved according to the 
rotation of the vertically moving cam 14, a portion comprising the rolling 
bearing 9, the lower end member 8 and the plate 7 is upwardly moved. The 
frame receiving arm 4 connected to the plate 7 by the shaft 6 is thus 
upwardly moved to point B so as to scoop up the lead frame 1 from the 
guide rail 2. The motor 16 is stopped at half rotation. A predetermined 
number of pulses are then applied to the pulse motor 17 from an external 
pulse generator (pulse motor driver) according to the distance between the 
guide rails 2 and 3 so that the pulse motor 17 is driven. When the timing 
pulleys 19a, 19b are rotated by driving the pulse motor 17, the timing 
belt 18 is rotated following the rotation of the pulleys 19a, 19b. The 
rotation of the timing belt 18 is converted into a transverse horizontal 
linear motion of the bearing block 20 through the connecting member 20a. 
The portion comprising the frame receiving arm 4, the bearing block 20, 
the connecting member 20a, the shaft 6, the plate 7, the lower end member 
8 and the rolling bearing 9 is thus horizontally moved from point B to 
point C in the transverse direction. When the motor 16 for driving the 
vertically moving cam 14 is then half rotated, the guide plate 13 is 
downwardly pushed by the vertically moving cam 14, and at the same time, 
the rolling bearing 9 is also dowwnwardly pushed. The frame receiving arm 
14 is consequently downwardly moved to point D so as to place the lead 
frame 1 on the guide rail 3. When the pulse motor 17 is driven to rotate 
in the reverse direction, the frame receiving arm 4 is returned to point A 
to complete one cycle. 
In the conventional apparatus for conveying a lead frame configured as 
described above, since the frame receiving arm must be horizontally 
positioned with high accuracy according to the positions of the guide 
rails, the pulse motor is used. However, the pulse motor driver is 
required as an external apparatus for driving the pulse motor. The 
conventional apparatus thus has the problem that the need for two motors 
for vertical and horizontal motion increases the cost of the apparatus. 
SUMMARY OF THE INVENTION 
The present invention has been achieved for solving the above problem, and 
it is an object of the present invention to provide an apparatus for 
conveying a lead frame which comprises a single motor used for performing 
a sequence of operations (referred to as "rectangular motion" hereinafter) 
comprising vertical operations and horizontal operations and describing a 
rectangle. 
It is another object of the present invention to provide a transverse 
conveying unit used in the lead frame conveying apparatus and a method of 
converting an elliptic motion into a rectangular motion. 
In order to achieve the objects, the present invention provides a lead 
frame conveying apparatus for transferring a lead frame sent to one of two 
guide rails between the two guide rails by scooping up the lead frame in a 
space formed by partially cutting off each of the guide rails, the 
apparatus comprising frame receiving means for carrying the lead frame, 
moving block means holding said frame receiving means so that the frame 
receiving means vertically slides so as to be elastically balanced at a 
predetermined neutral position thereof in the horizontal direction along 
the transfer direction, horizontal linear guide means extended between the 
two guide rails in order to horizontally guide the moving block means 
along the transfer direction of the lead frame, stopper means for 
horizontally positioning the frame receiving means corresponding to the 
positions of the two guide rails, driving force transmitting means for 
making an elliptic motion which describes an ellipse and which comprises a 
horizontal reciprocating linear motion between the two guide rails and 
semi-circular motions at both ends of the reciprocating motion, driving 
means for giving a driving force to the driving force transmitting means, 
driving force converting means which is provided on the moving block means 
and which is connected to the driving force transmitting means and the 
frame receiving means so as to transmit the horizontal reciprocating 
linear motion in the elliptic motion of the driving force transmitting 
means to the frame receiving means and convert the semi-circular motions 
at both ends of the reciprocating linear motion into vertical 
reciprocating linear motions by employing rolling contact for absorbing 
the horizontal component thereof and transmit the vertical reciprocating 
linear motions to the frame receiving means so that the frame receiving 
means performs a rectangular motion. 
The present invention further includes a transverse conveying mechanism 
used in the lead frame conveying apparatus and a method of converting an 
elliptic motion into a rectangular motion. 
In the present invention, the elliptic motion of the driving force 
transmitting means driven by single driving means is converted into the 
rectangular motion which describes a rectangle by the driving force 
converting means which employs rolling contact, and transmitted to the 
frame receiving means.

DESCRIPTION OF PREFERRED EMBODIMENTS 
An embodiment of the present invention is described below with reference to 
the drawings. FIG. 1 is a schematic perspective view of a lead frame 
conveying apparatus in accordance with an embodiment of the present 
invention, FIG. 2 is a partially sectional top view, FIG. 3 is a front 
view without showing a timing pulley portion, and FIG. 4 is a partially 
sectional side view of a principal portion. In each of the drawings, the 
portions which are the same as or correspond to those of the conventional 
apparatus shown in FIGS. 5 and 6 are denoted by the same reference 
numerals. The arrangement of a lead frame conveying apparatus according to 
the present invention is outlined below. The elliptic motion of timing 
pulleys 19a, 19b and a timing belt 18 placed over the pulleys 19a, 19b, 
which serve as driving force transmitting means, is converted into a 
rectangular motion, which comprises vertical motions and horizontal 
motions so as to described a rectangle, by a moving block 100 serving as 
moving block means and the driving force converting means described below 
which is loaded on the moving block 100. The rectangular motion is then 
transmitted to a frame receiving arm 4 serving as frame receiving means. 
In the perspective view of FIG. 1, a base plate 22 is a base on which the 
lead frame conveying apparatus is installed. A horizontal linear guide 
rail 11 fixed on the base plate 22 so as to serve as horizontal linear 
guide means horizontally guides the moving block 100. An induction motor 
17 serving as driving means rotates the timing pulley 19b through gears 
15a, 15b so that the timing belt 18 placed over the timing pulleys 19a, 
19b performs an elliptic motion. The elliptic motion of the timing belt 18 
comprises the horizontal reciprocating rectilinear motion within the 
distance between the centers of the timing pulleys 19a, 19b and the 
semi-circular motions at both ends of the reciprocating rectilinear 
motion, i.e., outside the distance between the centers of the timing 
pulleys 19a, 19b. Stoppers 25a, 25b serving as stopper means horizontally 
position the frame receiving arm 4 according to the positions of the guide 
rails 2, 3 and abut, at predetermined positions at both ends of the 
horizontal motion, against the slide block 23 of the moving block 100 to 
which the lower end member 4a of the arm 4 is attached so as to stop the 
slide block 23. The slide block 23 is slidably provided on two parallel 
shafts 30 supported by the bearing block 24. A first eccentric shaft 26a 
provided on the side of a first disc 26 opposite to the moving block 100 
is fixed at a predetermined position of the timing belt 18, the first disc 
26 being rotatably provided on the moving block 100. The horizontal motion 
of the elliptic motion of the timing belt 18 between the centers of the 
timing pulleys 19a, 19b is transmitted through the first disc 26 to the 
whole moving block 100 to which the frame receiving arm 4 is attached so 
that the moving block 100 is moved on the linear guide rail 11. The 
semi-circulation motion at each of the timing pulleys 19a, 19 b is 
converted into a vertical motion and then transmitted to the frame 
receiving arm 4 through the first disc 26, the rotation shaft 35 of the 
first disc 26 which is extended through the moving block 100 (refer to 
FIG. 4), a second disc 28 provided at the opposite end of the rotational 
shaft 35, the second eccentric shaft 28a of the second disc 28 and the 
rolling bearing 9 fitted to the second eccentric shaft 28a. 
In FIGS. 2 to 4, FIGS. 2 and 4 are partially sectional views showing the 
peripheral portion of the timing pulley 19a and the portion including the 
rotational shafts and bearings, respectively. FIG. 3 does not show the 
portion corresponding to the timing pulleys. As shown in FIGS. 3 and 4, 
the slide block 23 is slidably provided on the two shafts 30 through 
rolling bearings 31. The two shafts 30 are supported at both ends thereof 
by the bearing block 24. As shown in FIGS. 2 and 4, extension spring coils 
27a, 27b are respectively interposed between the side block 23 and the 
both sides of the bearing block 24. If no external force is applied to the 
slide block 23, the slide block 23 is placed at the neutral position 
(generally at the center of the block 24) between the forces of the coil 
springs 27a, 27b. For example, when the slide block 23 abuts the stopper 
25a or 25b at one end of the horizontal motion thereof and is subjected to 
a force, the slide block 23 is slid along the shafts 30 against the force 
of the coil spring 27a or 27b and returned to the neutral position as 
external force is decreased. The vertical linear guide rail 12 vertically 
extended and provided on the lower end member 4a of the frame receiving 
arm 4 is slidably fitted to the vertical linear guide bearing 12a provided 
on the slide block 23 through a holder 5a. Supporting portions 19c and 19d 
support the timing pulleys 19a and 19b, respectively. Supporting portions 
25c and 25d support the stoppers 25a and 25b, respectively. 
As shown in FIG. 4, the moving block 100 serving as moving block means 
basically comprises the bearings block 24 which supports the slide block 
23 and which is fixed through the holder 5 on the linear guide bearing 11a 
slidably fitted to the linear guide rail 11. The driving force converting 
means comprising the rotational shaft, 35, the bearing 29 thereof and so 
on and the frame receiving means comprising the frame receiving arm 4 and 
so on are mounted on the moving block 100. The frame receiving arm 4 has a 
bottom portion (lower surface) 4b which is formed in the lower portion 
thereof and which has a horizontal surface in rolling contact with the 
rolling bearing 9 provided on the second eccentric shaft 28a of the second 
disc 28. The rolling contact between the bottom portion 4b and the rolling 
bearing 9 absorbs the horizontal component of the semi-circular motion at 
each of the timing pulleys 19a, 19b so that the vertical component only is 
transmitted to the frame receiving arm 4. The semi-circular motion at each 
of the timing pulleys 19a, 19b is thus converted into the vertical motion 
and transmitted to the arm 4. Assuming that the distance between the 
centers of the rotational shaft 35 and the second eccentric shaft 28a is 
R, the width of the bottom portion 4b in the direction of rolling of the 
rolling bearing 9 must be thus at least 2R. The driving force converting 
means comprises that first disc 26, the first eccentric shaft 26a, the 
rotational shaft 35, the bearing 29, the second disc 28, the second 
eccentric shaft 28a and the rolling bearing 9. A connecting pin 20 
connects the timing belt 18 and the first eccentric shaft 26a. The 
mounting portion 26b of the first eccentric shaft 26a has a plane portion 
26c formed for mounting the connecting pin 20. The connecting pin 20 is 
passed through the timing belt 18 and buried at the tip thereof in the 
mounting portion 26b so as to be fixed to the first eccentric shaft 26a, 
with the timing belt 18 held between the pin 20 and the mounting portion 
26b. Each of the timing pulleys 19a, 19b has a clearance groove 19e for 
the connecting pin 20 formed along the central portion of the periphery 
thereof. 
The operation of the apparatus is described below. The frame receiving arm 
4 is waits for the lead frame 1 at point A. In this state, the slide block 
23 abuts against the stopper 25a, and the frame receiving arm 4 is placed 
at a lower position. When the motor 17 is driven, the timing belt 18 is 
rotated through the gears 15a, 15b and the timing pulley 19b to make an 
elliptic motion. Since the first eccentric shaft 26a attached to the 
timing belt 18 by the connecting pin 20 is thus upwardly moved along the 
outer periphery of the timing pulley 19a so as to described a semi-circle, 
the first disc 26 is rotated. The rotation of the first disc 26 causes the 
second eccentric shaft 28a to be rotated around the center of the 
rotatioal shaft 35 along a circle with a radius of R. Since the rolling 
bearing 9 is in rolling contact with the lower surface 4b of the frame 
receiving arm 4, the rotation with a radius of R is converted into an 
upward movement and transmitted to the frame receiving arm 4. The frame 
receiving arm 4 is thus upwardly moved to point B while being guided by 
the linear guide rail 12 fixed to the slide block 23 so as to scoop up the 
lead frame 1 conveyed from an external apparatus (not shown) to the guide 
rail 2 comprising two rails 2a, 2b. When the motor 17 is further 
continuously driven, the timing belt 18 continues an elliptic motion, and 
the first eccentric shaft 26a makes a horizontal motion along the upper 
portion of the timing belt 18. At this time, the slide block 23 to which 
the frame receiving arm 4 is attached is at the neutral position in the 
bearing block 24 by virtue of the two extension coil springs 27a, 27b 
interposed between the slide block 23 and the bearing block 24. The moving 
block 100 comprising the bearing 29, the arm 4 and the like is moved from 
point B to point C by the horizontal movement of the first eccentric shaft 
26a while being guided the linear guide rail 11. When the moving block 100 
reaches point C, the slide block 23 abuts against the stopper 25b so that 
the frame receiving arm 4 is positioned between the rails 3a, 3b of the 
guide rail 3. When the timing belt 18 is further rotated, the portion of 
the moving block 100 except the slide block 23 and the frame receiving arm 
4 continues a horizontal movement. After the first eccentric shaft 26a is 
passed through an upper contact point on the outer periphery of the timing 
pulley 19b, the first eccentric shaft 26a performs a downward semicircular 
motion along the outer periphery of the timing pulley 19b. The 
semi-circular motion of the first eccentric shaft 26a is converted into a 
downward rectilinear motion through the rotational shaft 35, the second 
disc 28, the second eccentric shaft 28a and the rolling bearing 9 and 
transmitted to the frame receiving arm 4. The arm 4 thus lowers the lead 
frame 1 to the guide rail 3 and reaches point D. When the timing belt 18 
is further rotated, the first eccentric shaft 26a performs a horizontal 
motion after being passed through a lower contact point on the outer 
periphery of the timing pulley 19b so that the moving block 100 including 
the frame receiving arm 4 starts to horizontally move. At this time, if 
the slide block 23 is separated from the stopper 25b, the slide block 23 
is moved to a position (generally at the center of the bearing block 24) 
where the spring forces of the two coil springs 27a, 27b are balanced. The 
moving block 100 then continues the horizontal movement. When the slide 
block 23 abuts against the stopper 25a and reaches point A, a sequence of 
operations are completed in one cycle. Thus the lead frame 1 is completely 
transferred from the guide rail 2 to the guide rail 3. 
When the lead frame 1 is transferred from the guide rail 3 to the guide 
rail 2, the motor 17 is reversed so that the timing belt 18 makes an 
elliptic motion in the reverse direction. 
As described above, in the present invention, the timing belt placed over 
the two timing pulleys makes an elliptic motion in which the horizontal 
reciprocating rectilinear motion between the centers of the timing 
pulleys, or between the stoppers provided at both ends of the conveyance 
direction, is transmitted to the frame receiving arm as it was, and the 
remaining rectilinear motion and subsequent semi-circular motion along 
each of the pulleys at both ends of the reciprocating rectilinear motion 
outside of the distance between the centers of the timing pulleys, or 
outside the stoppers at both ends of the conveyance direction, is 
converted into a vertical reciprocating rectilinear motion by employing 
rolling contact and slidably attaching the frame receiving arm to the 
moving block with horizontal elasticity so as to absorb the horizontal 
component thereof and then transmitted to the frame receiving arm. The 
invention thus requires only one induction motor as driving means and has 
the effect of obtaining a method of converting an elliptic motion to a 
rectangular motion at very low cost, a horizontal conveying mechanism 
which employs the method, and a lead frame conveying apparatus which 
employs the conveying mechanism.