Machine tools abstract
A tool changer for machine tools is capable of transferring a tool
transfer pot with a stroke smaller than the transfer distance of
the tool transfer pot. The tool changer for a combined machining
lathe includes a tool magazine having a multiplicity of tools and
serving for transferring and indexing a next-process tool to a specified
tool takeout position. A tool transfer mechanism transfers the next-process
tool positioned in the tool takeout position or the tool delivery
position to a tool changing position. A tool changing mechanism
changes a process-completed tool loaded on a tool post body with
the next-process tool positioned in the tool changing position.
The tool transfer mechanism comprises a transfer arm pivotally disposed
between the tool delivery position and the tool changing position.
A tool transfer pot is coupled to a front-end portion of the transfer
arm and serves to support the next-process tool.
Machine tools claims
What is claimed is:
1. The tool changer for machine tools comprising:
a tool magazine having a multiplicity of tools, said tool magazine
transferring and indexing a next-process tool to a predetermined
tool takeout position;
a tool transfer mechanism for taking out and transferring the next-process
tool positioned in the tool takeout position to a tool changing
position;
a tool changing mechanism for changing a tool loaded on a tool
post with the next-process tool positioned in the tool changing
position; and
a tool transfer pot for holding one of the tools, said transfer
pot having an engaging groove extending in a linear direction,
wherein said tool transfer mechanism comprises:
a transfer arm pivotably disposed so as to have a front end portion
of said transfer arm move between the tool takeout position and
the tool changing position,
a tool holding member coupled to said front end portion of said
transfer arm, said tool holding member supporting the next-process
tool and having a guide pin that engages with said engaging groove
to thereby position and support the tool transfer pot in axial and
circumferential directions; and
a cylinder mechanism coupled to said transfer arm for driving said
transfer arm.
2. The tool changer as claimed in claim 1 wherein said tool changing
mechanism is rotationally mounted on a shaft so as to allow the
tool loaded in the tool post and the next-process tool to be rotated
180 degrees.
3. The tool changer for machine tools comprising:
a tool magazine having a multiplicity of tools, said tool magazine
transferring and indexing a next-process tool to a predetermined
tool takeout position;
a turning/transfer mechanism for taking out and transferring the
next-process tool positioned in the tool takeout position to a tool
delivery position;
a tool transfer mechanism for transferring the next-process tool
positioned in the tool delivery position to a tool changing position;
a tool changing mechanism for changing a tool loaded on a tool
post with the next-process tool positioned in the tool changing
position; and
a tool transfer pot for holding one of the tools, said transfer
pot having an engaging groove extending in a linear direction,
wherein said tool transfer mechanism comprises:
a transfer arm pivotably disposed so as to have a front end portion
of said transfer arm move between the tool delivery position and
the tool changing position,
a tool holding member coupled to said front end portion of said
transfer arm, said tool holding member supporting the next-process
tool and having a guide pin that engages with said engaging groove
to thereby position and support the tool transfer pot in axial and
circumferential directions; and
a cylinder mechanism coupled to said transfer arm for driving said
transfer arm.
4. The tool changer as claimed in claim 3 wherein said tool changing
mechanism is rotationally mounted on a shaft so as to allow the
tool loaded in the tool post and the next-process tool to be rotated
180 degrees during movement of said tool changing mechanism.
5. The tool changer as claimed in claim 3 wherein said turning/transfer
mechanism comprises a cylinder mechanism capable of reciprocal and
rotational movement.
Machine tools description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a tool changer for machine tools.
In particular, the tool changer is equipped with a tool transfer
mechanism that transfers a next-process tool, which has been transferred
to a specified tool takeout position by a tool magazine, between
the tool takeout position and a tool changing position.
2. Discussion of the Related Art
In some tool changers, there is a distance between the tool changing
position set near the tool spindle and the tool takeout position
for the next-process tool, which is set to the tool magazine. In
such a case, generally, the tool changer is equipped with a tool
transfer mechanism for transferring the next-process tool from the
tool takeout position to the tool changing position.
An example of such a tool transfer mechanism is a tool transfer
mechanism having an air cylinder mechanism that moves back and forth
over a range from the tool takeout position to the tool changing
position. In this device, a piston rod of the air cylinder mechanism
is equipped with a tool pot for holding the next-process tool. The
tool pot is linearly transferred between the tool takeout position
and the tool changing position by the piston rod.
However, this conventional tool transfer mechanism requires a large-scale
air cylinder mechanism having a stroke equal to or larger than the
transfer distance of the tool pot. This poses the problem of increased
installation space.
SUMMARY OF THE INVENTION
The present invention has been accomplished in view of these and
other problems. Therefore, an object of the invention is to provide
a tool changer for machine tools that is capable of transferring
the tool pot with a stroke smaller than the transfer distance of
the tool pot.
In order to achieve the above and other objects, the present invention
provides a tool changer for machine tools comprising: a tool magazine
having a multiplicity of tools, the tool magazine transferring and
indexing a next-process tool to a predetermined tool takeout position;
a tool transfer mechanism for taking out and transferring the next-process
tool positioned in the tool takeout position to a tool changing
position; and a tool changing mechanism for changing a tool loaded
on a tool post with the next-process tool positioned in the tool
changing position. The tool transfer mechanism comprises a transfer
arm pivotably disposed so as to have a front end portion of the
transfer arm move between the tool takeout position and the tool
changing position, a tool holding member coupled to the front end
portion of the transfer arm, the tool holding member supporting
the next-process tool; and a cylinder mechanism coupled to the transfer
arm for driving the transfer arm.
In an embodiment, the present invention provides a tool changer
for machine tools as described above, further comprising a tool
transfer pot for holding one of the tools, the transfer pot having
an engaging groove extending in a tangential direction, and the
tool holding member having a guide pin that engages with the engaging
groove to thereby position and support the tool transfer pot axially
and circumferentially.
According to the tool changer of the present invention, the transfer
arm is pivotably provided between the tool takeout position and
the tool changing position. The tool holding member is provided
at the front end portion of the transfer arm. The cylinder mechanism
for pivotally driving the transfer arm is coupled to the transfer
arm. Therefore, the tool holding member can be transferred from
the tool takeout position to the tool changing position with a stroke
smaller than the travel distance of the tool holding member. As
a result, the cylinder mechanism can be downsized proportionally.
Consequently, the installation space can be reduced.
In an embodiment, an engaging groove is formed in the tool transfer
pot and the tool holding member is provided with the guide pin to
engage with the engaging groove. Therefore, when holding the tool
transfer pot by the tool holding member, the tool transfer pot can
be positioned in the axial and circumferential directions with reliability.
Moreover, the tool transfer pot can be transferred to the tool changing
position with the proper orientation. Thus the positioning accuracy
of the cutting tool can be ensured in loading the next-process tool
onto the tool spindle.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other objects and features of the present invention
will be clearly understood from the following description with respect
to the preferred embodiment thereof when considered in conjunction
with the accompanying drawings and diagrams, in which:
FIG. 1 is a right side view of a combined machining lathe equipped
with the tool changer according to an embodiment of the present
invention;
FIG. 2 is an enlarged partial front view of the combined machining
lathe according to an embodiment of the present invention;
FIG. 3 is a right side view of the tool post of the combined machining
lathe according to an embodiment of the present invention;
FIG. 4 is a front view of the tool changer according to an embodiment
of the present invention;
FIG. 5 is a right side view showing the overall construction of
the tool changer and the rotation of the cylinder mechanism according
to an embodiment of the present invention;
FIG. 6 is a schematic rear view of the turn and transfer mechanism
of the tool changer according to an embodiment of the present invention;
FIG. 7 is a plan view showing the positioning state of the tool
transfer pot of the tool changer according to an embodiment of the
present invention;
FIG. 8 is a cross sectional view showing the positioning state
of the tool transfer pot according to an embodiment of the present
invention; and
FIG. 9 is a side view showing a tool changer according to another
embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
An embodiment of the present invention is described below with
reference to the accompanying drawings.
Referring to the figures, combined machining lathe 1 is capable
of performing both turning and rotating-tool machining. On top of
a fixed bed 2 a headstock 7 is fixedly disposed at a left side
end portion as viewed from the front. A saddle 4 is disposed on
the right side as viewed on the right side face so as to be movable
in a Z-axis (a direction vertical to the sheet of FIG. 1) parallel
to the axis of the headstock 7 via two linear guides 3a. A column
5 is disposed on top of the saddle 4 so as to be movable in a direction
within a horizontal plane and perpendicular to the axis of the headstock
7 via two linear guides 3b. Moreover, a tool post 6 with a tool
T fitted thereto is disposed on the column 5 so as to be movable
within a plane along a sloping surface 5a of the column 5 and in
an X-axis direction perpendicular to the axis of the headstock 7.
A main spindle (not shown) equipped with a chuck 8 for gripping
a workpiece is provided on the headstock 7. This main spindle is
rotationally driven by a spindle motor (not shown). In addition,
a door 1a for opening and closing an access opening is formed in
a cover (not shown).
Regarding the structure of the tool post 6 a support base 9 is
disposed on the forwardly-declined sloping surface 5a of the column
5 so as to be slidable in the X-axis direction. Although it is not
particularly limited, the slope angle shown in the figures is approximately
60 degrees. A tool post body 11 is supported on the support base
9 so as to be rotationally indexable and clampable about a turning
axis A, so that the movement is perpendicular to the sloping surface
5a, by means of a rotational indexing device 10.
The tool post body 11 comprises a tool spindle 14 in which the
tool T is removably fitted at its front end portion and a tool spindle
head 12 for rotatably supporting the tool spindle 14. A tool spindle
motor 13 is placed within the tool spindle head 12 and drives the
rotation of the tool spindle 14.
The rotational indexing device 10 comprises a rotating table 16
fixedly bolted to the tool post body 11. A fixing table 17 is disposed
within the rotating table 16 so as to be coaxial therewith and is
fixedly bolted to the support base 9. The rotational indexing device
10 further comprises a rotation driving mechanism 18 for rotationally
driving the rotating table 16 to a specified indexing angular position
about the turning axis A. The rotational indexing device 10 also
comprises a coupling mechanism 19 which fixes the rotating table
16 to the indexing angular position of the fixing table 17. With
the tool post body 11 fixed in the indexing angular position, lathe
turning or milling can be performed.
The combined machining lathe 1 has a tool exchanger 20. This tool
exchanger 20 on which a multiplicity of tools T are loaded, comprises:
a tool magazine 21 for transferring, indexing and positioning a
next-process tool T1 in a tool takeout position P1; and a tool turning/transferring
mechanism 22 for taking out the next-process tool T1 positioned
to the tool takeout position P1 and turning and transferring it
to a delivery position P2. The tool exchanger 20 further comprises:
a tool transfer mechanism 23 for transferring the next-process tool
T1 which has been transferred to the delivery position P2 to a
tool changing position P3; and a tool changing mechanism 24 for
replacing a process-completed tool T0 loaded on the tool spindle
14 with the next-process tool T1 transferred to the tool changing
position P3. It is noted that during a tool change, the process-completed
tool T0 is positioned in the changing position by turning the tool
post body 11 in the direction vertical to the sheet of FIG. 1 about
the turning axis A by the rotational indexing device 10.
The tool magazine 21 is located on the fixed bed 2 and behind or
rearward of the tool post 6. The tool magazine 21 is supported by
a magazine support base 25 fixedly bolted to a rear side wall 2a
of the fixed bed 2. This tool magazine 21 is constructed so that
a multiplicity of tool transfer pots 26 for holding the tool T1
on an endless transfer chain 21b wound around a driving sprocket
21a are removably attached at a specified pitch. The endless transfer
chain 21b is driven by a turn driving motor (not shown). The tool
takeout position P1 is set so as to be positioned on a line that
connects the tool delivery position P2 the tool changing position
P3 and the process-completed tool T0 indexed to the changing position,
as viewed in FIG. 1. These positions P1 to P3 are set generally
flush with one another. As a result, the transfer amount of the
next-process tool T1 is reduced.
The tools T are removably fitted to the individual tool transfer
pots 26 of the tool magazine 21. Each tool T is placed so as to
be positioned within a horizontal plane and toward a direction perpendicular
to the axis of the headstock 7 (Z-axis direction). As seen in FIG.
5 the tool T has a cutting tool 28 fitted to a cylindrical-shaped
tool holder 27 which is held by the tool transfer pot 26.
The tool changing mechanism 24 is constructed so that a changing
shaft 31 is axially movable and rotatably supported by a support
member 30 provided at a left end portion of the saddle 4 as viewed
from the front. A changing arm 32 is fixed to a front end portion
of the changing shaft 31. In this changing arm 32 cutouts 32a for
holding the tool holder 27 are formed at both ends of a band-shaped
plate. In the support member 30 a drive mechanism 30a is provided
which drives the changing shaft 31 into rotation and into reciprocation
in the axial direction.
The changing shaft 31 is constructed so that an axially moving
cylinder 31b is integrally fitted to a rotating shaft 31a so as
to be axially movable and rotatable therewith. The changing arm
32 is fixed to a front end portion of the axially moving cylinder
31b. As shown in FIG. 4 a portion of the changing shaft 31 above
the axis B shows a state that the changing shaft 31 has moved forward
so that a tool is fitted to the tool spindle 14. Further, the lower
portion shows a state that the changing shaft 31 has moved backward
so that a tool is pulled out from the tool spindle 14.
The tool turning/transferring mechanism 22 has the following structure.
A takeout opening 25b is formed at a portion of an upper wall 25a
of the magazine support base 25 adjacent to the tool takeout position
P1. A piston rod 36 of a cylinder mechanism 35 is advanceably and
retractably opposed to the takeout opening 25b. This cylinder mechanism
35 is rotatably held between a position adjacent to the tool takeout
position P1 and a position rotated 90 degrees from the position
about a turning axis C, by means of a bracket 38 mounted on the
top of the upper wall 25a. The bracket 38 is provided with an unshown
turn driving mechanism.
The piston rod 36 is equipped with a generally U-shaped gripping
member 37 and a presser pin 39. The presser pin 39 is biased axially
downward with an unshown spring. By pressing the upper part of the
tool transfer pot 26 with the presser pin 39 the tool transfer
pot 26 is gripped in cooperation with the gripping member 37.
When the piston rod 36 goes down, the gripping member 37 and the
presser pin 39 move to a position where a tool transfer pot 26 of
the next-process tool T1 is to be gripped. In this state, the tool
transfer pot 26 is indexed to the tool takeout position P1. With
the tool transfer pot 26 held by the gripping member 37 and the
presser pin 39 the piston rod 36 goes up. At the upper end position
of this upward movement, the cylinder member 35 turns 90 degrees
about the turning axis C, and subsequently the piston rod 36 goes
down. As a result, the next-process tool T1 is turned and transferred
to the tool delivery position P2 so as to be parallel to the axis
of the headstock 7.
The tool transfer mechanism 23 is constructed as follows. A transfer
support base 45 is vertically provided and fixed between the column
5 on top of the saddle 4 and the changing arm 32.
This transfer support base 45 is formed into a generally box shape
which extends upward while bending rightward as shown in FIG. 4.
The transfer support base 45 has a side wall portion 45b integrally
formed at a peripheral edge portion of its vertical wall portion
45a so that it is wide in the back-and-forth direction when viewed
from the front. A guide plate 46 is fixedly bolted at an upper end
portion of the vertical wall portion 45a. This guide plate 46 is
formed into a band shape extending horizontally over a range from
the tool delivery position P2 to the tool changing position P3.
On the left side face of the guide plate 46 a rail 47a of a linear
guide 47 is fixed and extends linearly between the two positions
P2 P3 where a block 47b is slidably engaged with the rail 47a
with balls (not shown) interposed between them.
A pivot shaft 48 is fixedly bolted at a lower end portion of the
vertical wall portion 45a. A boss 51 fixed at the lower end of a
transfer arm 49 is pivotably fitted to the pivot shaft 48 via a
bearing 50. This transfer arm 49 is constructed so that a band-shaped
upper half portion 49b is fixedly bolted to a generally rectangular-cylindrical
lower half portion 49a. The upper end of the upper half portion
49b is fixed to the block 47b via a cam mechanism 53.
The cam mechanism 53 is constructed so that a cam plate 54 with
a cam groove (not shown) formed therein is fixed to the block 47b.
A cam follower 55 to be engaged with the cam groove of the cam plate
54 is attached to the upper half portion 49b. Pivotal motion of
the transfer arm 49 is transformed into linear motion of the linear
guide 47 by the cam mechanism 53.
Further, a piston rod 57 of an air cylinder 56 disposed with its
axis directed along the back-and-forth and horizontal direction
is coupled in proximity to the pivot shaft 48 of the transfer arm
49. The transfer arm 49 is pivotally driven between the delivery
position P2 and the tool changing position P3 by the expansion and
contraction of the piston rod 57. The air cylinder 56 is up-and-down
swingably supported by a bracket 59 via a pivot shaft 58 and the
bracket 59 is secured to the side wall portion 45b. The air cylinder
56 swings up and down on a fulcrum of this pivot shaft 58 thereby
allowing the piston rod 57 to move linearly.
A pot holding member (tool holding member) 60 is fixedly connected
to an upper end portion of the block 47b. In FIGS. 7 and 8 this
pot holding member 60 generally has a structure such that four guide
pins 62 are implanted on a support plate 61. Each of these guide
pins 62 is structured so that a sloping guide portion 62c is formed
at an upper end portion of a prismatic pin body 62a.
One set of engaging grooves 26a, 26b are cut out at each of the
front and rear places of the outer peripheral surface of each tool
transfer pot 26 and the guide pin 62 is engaged with the engaging
grooves 26a, 26b. In this way, the tool transfer pots 26 and therefore
the tools T, are positioned and supported in the axial and circumferential
directions.
Next, operation of the tool exchanger 20 of this embodiment is
explained. When the process of turning or rotating the tool T loaded
on the tool post body 11 has been completed, the rotational indexing
device 10 turns the tool post body 11 through 90 degrees about the
turning axis A. In this way, the process-completed tool T0 is indexed
and positioned to the tool changing position that is parallel to
the axis of the headstock 7.
During the machining process, the piston rod 36 of the cylinder
mechanism 35 moves down so that the gripping member 37 and the presser
pin 39 are positioned in the tool takeout position P1. When the
tool magazine 21 transfers, indexes and positions a tool transfer
pot 26 in which the next-process tool T1 is accommodated therein,
to the tool takeout position P1 the gripping member 37 and the
presser pin 39 grip the tool transfer pot 26. In this state the
piston rod 36 goes up and then turns 90 degrees about the turning
axis C. As a result, the next-process tool T1 is turned to a spindle-parallel
position parallel to the headstock 7 and to the process-completed
tool T0. In this state the piston rod 36 then goes down again. Then,
the guide pins 62 of the pot holding member 60 are engaged with
the engaging grooves 26a, 26b of the tool transfer pot 26 in which
the next-process tool T1 is accommodated. In this way, the next-process
tool T1 (tool transfer pot) is positioned and supported to the pot
holding member 60 at the delivery position P2.
Subsequently, the piston rod 57 of the air cylinder 56 retreats,
and the transfer arm 49 transfers the pot holding member 60 linearly
from the delivery position P2 to the tool changing position P3.
In this case, the relative motion of the front end of the transfer
arm 49 with respect to the block 47b due to the pivoting of the
transfer arm 49 is absorbed by the cam follower 55 and the cam groove,
and the swing of the air cylinder 56 due to the pivoting of the
transfer arm 49 is absorbed by the pivot shaft 58.
Then, the changing shaft 31 turns, and the changing arm 32 grips
the process-completed tool T0 of the tool post body 11 and the next-process
tool T1 in the tool changing position P3. In this state, the changing
shaft 31 retreats, and pulls out the process-completed tool T0 from
the tool spindle 14 and also pulls out the next-process tool T1
from the tool transfer pot 26. Subsequently, the changing arm 32
turns 180 degrees and advances. Then, the next-process tool T1 is
gripped by the tool spindle 14 and the process-completed tool T0
is gripped by the tool transfer pot 26 supported by the pot holding
member 60. This process-completed tool T0 is returned to a specified
pot position of the tool magazine 21 via the tool transfer mechanism
23 and the tool turning/transferring mechanism 22.
According to this embodiment, the tool magazine 21 is disposed
so that each tool T is directed perpendicular to the axis of the
headstock 7. The next-process tool T1 is taken out from the tool
takeout position P1 and turned and transferred to the tool delivery
position P2 parallel to the process-completed tool T0 of the tool
post body 11 in the spindle-parallel position by the tool turning/transferring
mechanism 22. This tool turning/transferring mechanism 22 is comprised
of the cylinder mechanism 35 and an unshown turning mechanism. Therefore,
in the case where the tool magazine 21 in multi-tool specifications
is mounted, the switch to the next-process tool T1 can be achieved
with a simple structure. Thus, the tool changer for machine tools
of this embodiment is applicable for use in flexible manufacturing
systems for the production of many items in low volumes as well
as for automatic continuous operation.
In this embodiment, since the tool magazine 21 is structured so
that an endless transfer chain 21b is provided in the rear of the
tool post 6 on the fixed bed 2 so as to run along the rear face
of the machine, a large number of tools T, for example as many as
60 to 180 pieces, can be mounted without requiring much space. This
allows for use in flexible manufacturing systems for the production
of many items in low volumes as well as for automatic continuous
operation.
Further, the tool takeout position P1 is in alignment with the
delivery position P2 and the tool changing position P3. The next-process
tool T1 in the tool takeout position P1 is taken out vertically
upward in the unit of the tool transfer pot 26 turned 90 degrees
at the upper end position and thereafter moved down, turned and
transferred to the delivery position P2. Therefore, the next-process
tool T1 can be transferred from the takeout position P1 to the delivery
position P2 smoothly with less up-and-down and turning motions.
According to this embodiment, the transfer arm 49 is provided pivotable
between the tool delivery position P2 and the tool changing position
P3. The piston rod 57 of the air cylinder 56 is coupled in proximity
to the pivot shaft 48 of the transfer arm 49. Moreover, the pot
holding member 60 is coupled to the front end portion of the transfer
arm 49. Therefore, as shown in FIG. 5 the length of stroke L2 of
the piston rod 57 can be shortened relative to the amount of linear
travel L1 of the pot holding member 60. In this way, the axial length
of the air cylinder 56 can be shortened when compared to the conventional
case where the air cylinder has a stroke equal to or more than the
length of travel of the tool pot. Thus, proportionally to this reduction,
the cost and installation space for the air cylinder 56 can be reduced.
Further, engaging grooves 26a, 26b extending in the tangential
direction are cut out in the tool transfer pots 26 for holding the
tool holder 27. The pot holding members 60 are provided with four
guide pins 62 to be engaged with the engaging grooves 26a, 26b.
Therefore, the next-process tool T1 can be positioned and supported
with a simple structure and transferred to the tool changing position
P3 in the positioned state. This allows for improved positioning
accuracy during the tool change.
The above embodiment has been described for a case where tools
T are placed in the tool magazine 21 so as to be directed perpendicular
to the axis of the headstock 7 and the next-process tool T1 is
turned and transferred to the delivery position P2 by the tool turning/transferring
mechanism 22. However, the tool magazine of the present invention
is not limited to this arrangement.
FIG. 9 shows a tool changer according to another embodiment of
the invention where the same reference numerals as in FIG. 5 designate
the same or corresponding component parts.
In this tool changer 70 a tool magazine 71 is provided in a longitudinally
longer elliptical form. Tools T are set in the tool magazine 71
so as to be parallel to the tool spindle 14 positioned in the tool
changing position, i.e., parallel to the process-completed tool
T0. Therefore, the tool takeout position P1 in the tool magazine
71 is coincident with the delivery position P2.
The piston rod 57 of the air cylinder 56 is coupled to the transfer
arm 49 forming part of the tool transfer mechanism in a proximity
of the pivot shaft 48. A pot holding member 72 is coupled to an
upper end portion of the transfer arm 49 via a cam mechanism. Further,
a gripping member 73 for gripping the tool holder 27 is provided
in the pot holding member 72. Also, a guide plate 74 is fixed to
an upper wall of the transfer support base 45 and a U-shaped guide
member 75 for guiding the pot holding member 72 in contact with
its lower and upper faces is fixed to the guide plate 74.
According to this tool changer 70 since the air cylinder 56 is
coupled to a proximity of the pivot shaft 48 of the transfer arm
49 the stroke length of the piston rod.57 can be made smaller than
the travel distance of the pot holding member 72 so that the same
effects as in the foregoing embodiment can be obtained. Also, since
the tools T in the tool magazine 71 are placed so as to be directed
parallel to the headstock, the aforementioned tool turning/transferring
mechanism can be eliminated. Further, since the guide member 75
is provided to contact the lower and upper faces of the pot holding
member 72 the pot holding member 72 can be transferred smoothly.
It is to be understood that although the present invention has
been described with regard to preferred embodiments thereof, various
other embodiments and variants may occur to those skilled in the
art, which are within the scope and spirit of the invention, and
such other embodiments and variants are intended to be covered by
the following claims. |