Workpiece transfer apparatus

In a workpiece transfer apparatus for a plurality of serially arranged machine tools, a horizontally extending transfer bar which forms a part of a parallel motion mechanism is provided alongside work tables of the machine tools and is vertically movable. A plurality of linear motion members is mounted on said transfer bar at the same interval as the machine tools and is connected to be bodily movable along the transfer bar. Each of the linear motion members carries a plurality of arm members each pivotable about a vertical axis for horizontal swing motion. A transfer jig for supporting a workpiece thereon is secured to each of the arm members. A feed cylinder device is provided to move the linear motion members along the transfer bar so as to transfer each workpiece from a position facing one machine tool to another position facing another machine tool successive thereto. A loading cylinder device is provided to horizontally swing all or a corresponding one of the arm members so as to load workpieces onto the work tables and unload the same therefrom. Further, an elevation cylinder device is provided to vertically move the transfer bar so as to seat the workpieces on the work tables and lift up the same therefrom.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates generally to a transfer apparatus for 
simultaneously transferring a plurality of workpieces to machining 
stations of machine tools and more particularly, to such a transfer 
apparatus suitable for use in constructing a flexible transfer line. 
2. Discussion of the Prior Art 
A known transfer machine is provided with a transfer apparatus for 
transferring workpieces from a machining station of a machining unit to 
that of another machining unit next thereto one after another. Typically, 
such a transfer apparatus is constructed as of a lift-and-carry type which 
is provided with a transfer bar movable in a vertical direction and a 
horizontal axial direction. The transfer bar has fixed thereto a plurality 
of transfer jigs each for supporting and positioning a workpiece thereon. 
In each of the machining stations, a pair of upstanding support plates are 
provided at opposite sides of the transfer bar, and a set of machining 
station jigs are respectively fixed on the tops of the upstanding support 
plates. 
However, because the jigs on each machining station are provided fixed, 
there is raised such a problem that a workpiece on each machining station 
cannot be machined at any other surface than that facing a machining unit. 
If an attempt were made to design machining station jigs angularly 
indexable on each machining station, a special arrangement would have to 
be made to avoid the interferences of the jigs and upstanding support 
plates with the transfer bar, thereby resulting in a complicated 
configuration of each machining station. This make it impossible the use 
of the known transfer apparatus of the lift-and-carry type in a flexible 
transfer line wherein a plurality of machine tools each controllable in 
accordance with a numerical control program are arranged to make a line 
each for a limited step of various machinings to be effected on each 
workpiece. 
In another method of transferring workpieces between work tables of a 
plurality of machine tools, there can be used transfer carts. However, 
such a method disadvantageously results in an increased cost because many 
transfer carts are required, and also results in a longer transfer time 
because the traveling speed of the transfer carts are generally slow. 
SUMMARY OF THE INVENTION 
Accordingly, it is a primary object of the present invention to provide an 
improved workpiece transfer apparatus which is not only capable of 
effectively utilizing advantages of the aforementioned lift-and-carry 
type, but also capable of coexisting with machining stations each 
incorporating a rotary work table. 
Another object of the present invention is to provide an improved workpiece 
transfer apparatus which is suitable for use in a flexible transfer line. 
Briefly, in a workpiece transfer apparatus according to the present 
invention, a transfer unit is disposed alongside work tables of a 
plurality of machine tools arranged to make a line in a first horizontal 
direction and is reciprocatively movable in the first horizontal direction 
and a vertical direction. A plurality of transfer jigs each capable of 
carrying a workpiece to be loaded onto one of the work tables are provided 
on the transfer unit at the same interval as the machine tools. The 
transfer jigs are respectively carried by transfer jig supports to be 
movable in a second horizontal direction which extends substantially 
across said first horizontal direction. The transfer unit is moved by a 
first feed device in the first horizontal direction so as to transfer each 
of the transfer jigs from one of the machine tools to another successive 
thereto. A second feed device operates to move all or a corresponding one 
of the transfer jigs in the second horizontal direction so as to present 
each transfer jig to the work table before which it stands and retract the 
same therefrom. A third feed device operates to vertically move the 
transfer unit, so that each transfer jig at the presented position puts 
the workpiece carried thereby on the work table for loading and removes 
the same therefrom for unloading. 
With this configuration, since the transfer unit for simultaneously 
transferring a plurality of workpieces is provided separately from the 
work tables, no modification is required with respect to the machine 
tools, so that the machine tools can be composed by general-purpose, 
numerically control machine tools known as, for example, machining 
centers. Moreover, since the transfer jigs are moved along a fixed path, 
the positioning of each transfer jig is reliable and precise, so that the 
transfer speed can be increased.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to the drawings and particularly to FIGS. 1 and 2 thereof, 
reference numerals 10a, 10b denote first and second numerical control 
machine tools each having a tool turret 12. Each of the machine tools 10a, 
10b is provided at a front portion of a bed 60a thereof with a rotary 
table 20 which is angularly indexable about a vertical axis. Each of the 
machine tools 10a, 10b is also provided with a clamping device 30 for 
clamping a workpiece W on the rotary table 20 from the above. At the front 
sides of the rotary tables 20 and alongside the same, there is disposed a 
transfer apparatus 40 for simultaneously transferring a plurality of 
workpieces W one after another to the rotary tables 20 constituting 
machining stations for the machine tools 10a, 10b. It is to be noted that 
although only two machine tools 10a, 10b are illustrated for the sake of 
brevity, there may be provided three or more machine tools which are of 
the same or different configurations. 
Each of the machine tools 10a, 10b is further provided with a column 11 
which is horizontally movable on the bed 60a in an orthogonal directions, 
namely in a left-right direction and a front-rear direction. A spindle 
head 12a is mounted on the front side of each column 11 for vertical 
movement. Each tool turret 12 is provided with a plurality of tool 
spindles 13 (only one shown in the figure) each carrying a cutting tool T. 
Each tool turret 12 is angularly indexable to horizontally present one of 
the tool spindles 13 before the workpiece W on the rotary table 20. 
Each of the rotary tables 20 is formed at its top with a depression 20a 
which permits a transfer jig described later of the transfer apparatus 40 
to enter, as shown in FIG. 3. A table jig (not shown) for supporting and 
positioning the workpiece W is fixed on the top portion except for the 
depression 20a of the rotary table 20. Each rotary table 20 is angularly 
indexable by an indexing motor 21. 
As best shown in FIG. 2, each of the clamping devices 30, 30 comprises a 
cross beam 32 which is secured to the top ends of a pair of supporting 
posts 31 mounted on the bed 60a, and a cylinder device 33 is attached to 
the cross beam 32 for clamping the workpiece W on the rotary table 20. A 
piston rod 34 of the cylinder device 33 is vertically movable toward and 
from the rotary table 20 and has attached to its lower end a clamping 
member 35 which is rotatable about the rotational axis of the rotary table 
20. 
A bridge member 61a is secured at opposite ends thereof to the beds 60a, 
60a of the machine tools 10a, 10b for connection therebetween. Another 
bridge member 61b is also secured at opposite ends thereof to one of the 
beds 60a and a base 60b of a loading station LS for connection 
therebetween. The transfer apparatus 40 is mounted on the bridge members 
61a and 61b. 
The transfer apparatus 40 comprises a plurality of links 41, each of which 
is pivotably carried on one of the bridge members 61a, 61b at its lower 
end. A transfer bar 42 is pivotably carried at the upper ends of the links 
41 to extend horizontally. Thus, the transfer bar 42 constitutes a 
parallel motion mechanism together with the bridge members 61a, 61b and 
the links 41. The loading station base 60b carries through a bracket (not 
numbered) a lift cylinder device 43 which is swingable within a vertical 
plane. A piston rod 44 of the lift cylinder device 43 is pivotably 
connected to the transfer bar 42 at one end thereof. 
As also shown in FIGS. 3, 4 and 5, the transfer bar 42 slidably guides 
through rollers 46 first and third linear motion members 45a-45c, which 
are connected in series by a number of connecting rods 47 at the same 
interval as the machine tools 10a, 10b. The linear motion members 45a-45c, 
together with the transfer bar 42, constitutes a transfer unit 56. 
Alongside the transfer bar 42, a feed cylinder device 48 is provided with 
its opposite ends being fixed on the beds 60a, 60a through a pair of 
brackets (not numbered). A piston rod 49 of the feed cylinder device 48 is 
engaged with an engaging block 50 secured to the third linear motion 
member 45c and is movable relative to the engaging block 50 only in a 
vertical direction. More specifically, as shown in detail in FIG. 4, the 
piston rod 49 rotatably carries at its one end a roll 49a, which is 
accommodated in a vertical guiding groove 50a formed in the engaging block 
50. 
The linear motion members 45a-45c respectively carry first to third 
transfer jigs 51a-51c each swingable about a vertical pivot shaft 63 
within a horizontal plane. Each of the transfer jigs 51a-51c is composed 
of a horizontally swingable arm portion 51m, one or two positioning pins 
and several seat members (not numbered) which are secured to the free end 
of the arm portions 51m. Each of the transfer jigs 51a-51c is bodily 
formed with a lever 57. As shown in FIG. 6, a cylinder device 52 for 
swinging the transfer jigs 51a-51c is attached to the first linear motion 
member 45a which is movable between the loading station LS and the first 
machine tool 10a next thereto. A piston rod 53 of the cylinder device 52 
is pivotably connected to one end of a drive link 54, the other end of 
which is pivotably connected to the lever 57 of the first transfer jig 
51a. A connecting rod 55 is provided between the levers 57 of the first 
and second transfer jigs 51a, 51b for pivotal connection therebetween, 
and similarly, another connecting rod 55 is provided between the levers 57 
of the second and third transfer jigs 51b, 51c. 
Operation of the apparatus as constructed above will be described 
hereafter. In the original state of operation shown in FIG. 1, the linear 
motion members 45a-45c are at the right or retracted stroke end, and each 
of the transfer jigs 51a-51c is also at the retracted end where the 
substantial part thereof is over the transfer bar 42, as indicated by the 
phantom line in FIG. 3. When a transfer command is given in the original 
state, the cylinder device 52 is operated to pivotally advance the 
transfer jigs 51a-51c. At the advanced end, the first transfer jigs 51a is 
placed under a new workpiece W supported on a support stand SS located at 
the loading station LS, while each of the second and third transfer jigs 
51b and 51c is entered into the depression 20a formed on each rotary table 
20 to be placed under the workpiece W on the rotary table 20. 
Subsequently, the cylinder device 43 is operated to lift up the transfer 
bar 42, whereby each of the transfer jigs 51a-51c carries the workpiece W 
in the mid course of such lift-up motion. When the transfer bar 42 reaches 
its upper end, the cylinder device 52 is adversely operated to retract the 
transfer jigs 51a-51c, whereby the workpieces W on the transfer jigs 
51a-51c are held over the transfer bar 42. The cylinder device 48 is then 
operated to advance the transfer bar 42. This causes the new workpiece W 
on the first transfer jig 51a to be moved before the rotary table 20 of 
the first machine tool 10a and also causes the workpieces W on the second 
and third transfer jigs 51b, 51c to be respectively moved before the 
rotary table 20 of the second machine tool 10b and before a support stand 
of an unloading station (not shown). Thereafter, the cylinder device 52 is 
again operated to advance the transfer jigs 51a-51c, so that the new 
workpiece W is brought over the rotary table 20 of the first machine tool 
10a, while the workpieces W on the second and third transfer jigs 51b, 51c 
are brought over the rotary table 20 of the second machine tool 10b and 
the support stand of the unloading station, respectively. The cylinder 
device 43 is then adversely operated to lower the transfer bar 42, whereby 
the workpieces W are seated on the rotary tables 20 of the first and 
second machine tools 10a, 10b and the support stand of the unloading 
station. The adverse operation of the cylinder device 52 then follows to 
retract the transfer jigs 51a-51c over the transfer bar 42, which is 
thereafter retracted by the adverse operation of the cylinder device 48 to 
complete one transfer cycle of the transfer apparatus 40. 
The workpieces W now mounted on the rotary tables 20 are then clamped 
thereon by the operation of the clamping devices 30. The columns 11 of the 
machine tools 10a and 10b are subsequently advanced with the tool spindles 
13 rotating, so as to machine one surface of each workpiece W. Other 
surfaces of each workpiece W can be machined by rotationally indexing the 
rotary table 20 carrying such each workpiece W. By the repetition of the 
aforementioned transfer cycle, each workpiece W which has been machined by 
one of the machine tools 10a, 10b is transferred onto the rotary table 20 
of the second machine tool 10b or onto the support stand of the unloading 
station. 
Being able to simultaneously transfer a plurality of workpieces W by the 
three cylinder devices 43, 48 and 52 for lift, advance/retract and swing 
motions as described above, the transfer apparatus of the first embodiment 
is low in manufacturing cost and speedy in transfer operation. 
FIG. 7 shows another embodiment of the transfer apparatus according to the 
present invention. In this embodiment, a cylinder device 70 for swing 
motion is provided at each of the machining, loading and unloading 
stations. More specifically, a piston rod 71 of each cylinder device 70 is 
provided with an engaging member 72 having a groove 77 extending in 
parallel relation with the transfer bar 42, and each of the levers 57 
which are bodily swingable with the respective transfer jigs 51a-51c is 
provided with a roller 76 fittable in the groove 77. The cylinder device 
70 is disposed so that when the linear motion members 45a-45c are moved to 
one of the stroke ends, the roller 76 of each lever 57 is accommodated in 
the groove 77 of the engaging member 72 of one of the cylinder devices 70 
respectively disposed at the two stations between which the transfer jig 
51a (51b, 51c) integral with each such lever 57 is movable. When the 
linear motion members 45a-45c reach one of the stroke ends, each cylinder 
device 70 for the associated station is operated, whereby the workpiece W 
is loaded onto the rotary table 20 of the associated station or is 
unloaded therefrom. 
In a modified form of the present invention, the linear motion members 
45a-45c may be omitted by enabling the transfer bar 42 per se to move in a 
vertical direction and a horizontal axial direction and by pivotably 
providing the transfer jigs 51a-51c directly on the transfer bar 42. 
It is to be noted that the transfer apparatus according to the present 
invention may be used for machine tools each having a non-rotatable work 
table, and that the machine tools for which the transfer apparatus 
according to the present invention is used may be numerical control 
machine tools designed for general purposes though they have been 
described as those for limited purposes in the embodiments. 
Obviously, numerous modifications and variations of the present invention 
are possible in light of the above teachings. It is therefore to be 
understood that within the scope of the appended claims, the present 
invention may be practiced otherwise than as specifically described 
herein.