Mechanism for locking angular movement of suction pad

Disclosed herein is a mechanism for locking the angular movement of a suction pad. The mechanism comprises a tubular body fitted to a root part of the suction pad and having a flange; a cover member attached to a moving assembly for displacing the suction pad; a first bush having a slide resistance lower than the tubular body and fitted to the flange of the tubular body; and a second bush having a slide resistance lower than the cover member and fitted to the inside of the cover member. The first bush and second bush are engaged with each other in such a manner that alternating concavities and convexities of the first bush are meshed with alternating convexities and concavities of the second bush, respectively, whereby the displacement of the suction pad in its axial direction is guided, and the angular movement of the suction pad is prevented.

FIELD OF THE INVENTION 
The present invention relates to a mechanism for locking the angular 
movement of a suction pad suitable for use in holding a work by suction to 
convey it. 
DESCRIPTION OF THE PRIOR ART 
In order to convey, for example, works in the form of a thin plate, there 
has heretofore been used suction pads connected to a vacuum and suction 
source. A suction pad of this kind is generally installed on an arm of a 
robot and utilized for the conveyance of works. 
A suction pad according to the prior art will be described. To convey a 
work by the suction pad, the edge of a skirt part, which is thin and 
flexible, of the suction pad is first of all brought into contact with the 
work. A vacuum and suction source is then energized to suck air in the 
skirt part through a root part, a tubular body and a tube. Since the 
suction pad holds the work by suction under a pressure reducing effect 
within the skirt part, the work can be conveyed so long as an arm of a 
robot is displaced. Thereafter, compressed air is fed within the skirt 
part to release the negative pressure condition, thereby releasing the 
work from the suction pad. 
In this case, the tube, which connects the vacuum and suction source and 
the tubular body to each other, is twisted due to the moving operation of 
the robot arm upon the conveyance, resulting in the angular movement of 
the tubular body, skirt part and work. However, such angular movement of 
the work is accompanied by disadvantages that difficulties are encountered 
on positioning of the work to a desired site in a desired posture, and the 
tube itself is damaged due to its torsion. 
SUMMARY OF THE INVENTION 
It is a general object of this invention to provide a mechanism for locking 
the angular movement of a suction pad, which can displace the suction pad 
smoothly toward a work, conduct its replacing operation with extreme ease 
and be easily produced. 
It is a principal object of this invention to provide a mechanism for 
locking the angular movement of a suction pad, which has a tubular body 
engaging with the suction pad, smoothly guides and displaces the tubular 
body in its axial direction, and prevents the angular movement of the 
suction pad through the tubular body, thereby permitting the exact 
positioning of a work. 
Another object of this invention is to provide a mechanism for locking the 
angular movement of a suction pad, in which a bush low in slide resistance 
is installed to a tubular body to which the suction pad is attached, while 
another bush, which is fitted on the first bush and is low in slide 
resistance, is installed to a cover member surrounding the tubular body, 
the bushes being engaged with each other so that the tubular body can be 
smoothly guided and displaced in its axial direction upon the holding of a 
work by suction and moreover, the work can be locked so as not to 
angularly move upon its conveyance, thereby permitting exact conveyance of 
the work to a target position without changing its posture and release of 
the work there. 
A further object of this invention is to provide a mechanism for locking 
the angular movement of a suction pad, which comprises a tubular body 
fitted to a root part of the suction pad; a cover member attached to a 
moving means for displacing the suction pad; a first bush which has a 
slide resistance lower than the tubular body and is fitted to the tubular 
body; and a second bush which has a slide resistance lower than the cover 
member and is fitted to the inside of the cover member, the first bush and 
second bush being engaged with each other in such a manner that 
alternating concavities and convexities of the first bush are meshed with 
alternating convexities and concavities of the second bush, respectively, 
whereby the displacement of the suction pad in its axial direction is 
guided, and the angular movement of the suction pad is prevented. 
Still a further object of this invention is to provide a mechanism for 
locking the angular movement of a suction pad, which comprises a tubular 
body fitted to a root part of the suction pad and having a flange; an 
annular body; and a member for the prevention of slipping-out, which is 
fitted to the tubular body and regulates the displacement range of the 
annular body, said tubular member being formed in the shape of a polygon 
in section, the annular body being formed by a synthetic resin in such a 
manner that its inner wall surface has a polygonal shape corresponding to 
the sectional form of the tubular body, and the tubular body being 
inserted through the annular body to mesh their polygonal portions with 
each other, whereby the displacement of the tubular body in the axial 
direction relative to the annular body is guided, and the angular movement 
of the suction pad is prevented. 
Yet still a further object of this invention is to provide a mechanism for 
locking the angular movement of a suction pad, wherein a cushioning 
material is fitted to the annular body or at least part of the member for 
the prevention of slipping-out. 
Yet still a further object of this invention is to provide a mechanism for 
locking the angular movement of a suction pad, which comprises a 
connecting part fitted to the suction pad and having a passage 
communicating with a suction source; and a sleeve fitted over the 
connecting part and serving to couple the connecting part to a moving 
mechanism for displacing the suction pad, the connecting part having a 
first engaging part at the outer peripheral surface thereof, and the 
sleeve having a second engaging part, which engages with the first 
engaging part, at the inner peripheral surface thereof, and a threaded 
part, which is connected to the moving mechanism, at the outer peripheral 
surface thereof. 
Yet still a further object of this invention is to provide a mechanism for 
locking the angular movement of a suction pad, wherein the first and 
second engaging parts are composed respectively of grooves and projecting 
parts, which extend in the axial and circumferential directions of the 
connecting part. 
Yet still a further object of this invention is to provide a mechanism for 
locking the angular movement of a suction pad, wherein the sleeve has a 
cutout over the whole length in its axial direction. 
Other objects and advantages of the present invention will be readily 
appreciated from the preferred embodiments of this invention, which will 
be described subsequently in detail with reference to the accompanying 
drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 illustrates a mechanism 12 for locking the angular movement of a 
suction pad 10 (hereinafter called "locking mechanism") according to the 
first embodiment of this invention. This suction pad 10 comprises a root 
part 16 having a hole 14 connected to a vacuum and suction source (not 
illustrated), and a skirt part 18 integrally extending from the root part 
16. The locking mechanism 12 joined to the suction pad 10 basically 
comprises a cover member 20, a tubular body 22, a coil spring 24, a first 
bush 26 on the side of the tubular body 22 and a second bush 28 on the 
side of the cover member 20. 
The tubular body 22, in which a through-hole 22a extending in its axial 
direction has been defined, has a flange 30 integrally formed at a 
somewhat upper portion from its lower end. The first bush 26 composed of a 
thermoplastic resin is fitted over this flange 30. As understood from FIG. 
2, the first bush 26 is in the form of a circle having alternating 
concavities and convexities in vertical section. 
The cover member 20 substantially in the form of a cylinder is formed so as 
to have a wide opening on its lower side and to be closed on its upper 
side. The closed upper end has a hole 20a for receiving the upper end of 
the tubular body 22 in its center. Into the lower opening of the cover 
member 20, is fitted the second bush 28 in the form of a circle having 
alternating convexities and concavities corresponding to the concave 
convex form of the first bush 26. As with the first bush, the second bush 
28 is also formed by a thermoplastic resin, preferably, a plastic. In view 
of the fact that the tubular body 22 and the cover member 20 are made of a 
metal, it is readily understood that both the first bush 26 and the second 
bush 28 are lower in slide resistance than the tubular body 22 and the 
cover member 20. 
The coil spring 24 wounded around the tubular body 22 is seated on the 
cover member 20 at one end thereof and is engaged with the first bush 26 
at the other end. Accordingly, the tubular body 22 is always biased 
through the first bush 26 in the direction illustrated by an arrow in FIG. 
1. In this case, the upper end of the coil spring 24 in FIG. 1 is held by 
a ring member 29. 
An annular body 33 is then fitted over the cover member 20. On an external 
thread 34 cut in the annular body 33, are screwed nuts 36a, 36b which 
fasten tightly an attaching plate 40 fitted to a cylinder rod 39 extending 
from a cylinder. 
The locking mechanism 12 according to the first embodiment of the present 
invention is basically constructed as described above. Its operation and 
effects will now be described with reference to FIGS. 1 through 3. 
When the suction pad 10 is used in conveying operation, the cover member 20 
is held by, for example, a robot hand (not illustrated). In this case, the 
through-hole 22a communicating with the hole 14 cut in the suction pad 10 
is connected to a tube 32 communicating with a vacuum and suction source 
(not illustrated), and the vacuum and suction source is energized. When 
the cylinder 38 is then energized to hold a work by suction, the skirt 
part 18 is brought into contact with the work to suck air in the skirt 
part 18. The suction pad 10 holds the work by suction under a pressure 
reducing effect within the skirt part 18. 
When the suction pad 10 comes into contact with the work, the coil spring 
24 contracts owing to its cushioning effect. Therefore, the first bush 26 
and the second bush 28 relatively slidable with respect to each other. In 
this embodiment, the bushes 26, 28 are composed of, for example, a 
thermoplastic resin molding having a smooth surface, a thermoplastic resin 
molding impregnated with an oil or a polytetrafluoroethylene-coated bush, 
and are thus highly slidable with respect to each other. Accordingly, it 
is not necessary to coat them with, for example, grease suitable for use 
in ensuring smooth displacement operation in the axial direction. 
Thereafter, the work is conveyed under the displacement operation of the 
robot hand (not illustrated) which holds the cylinder 38. However, the 
tube 32 connecting the vacuum and suction source to the tubular body 22 is 
twisted by the moving operation of the hand, thereby forcing the angular 
movement of the tubular body 22 and the work. Alternately, the momental 
movement of the work itself, which is caused by the moving operation of 
the hand or arm, forces the work to turn. In this embodiment, as described 
above, the locking mechanism is however achieved upon the conveyance of 
the work by providing the first bush 26 on the tubular body 22 using the 
flange 30 and disposing the second bush 28 in the cover member 20 to mesh 
these bushes 26, 28 with each other. Therefore, it is possible to exactly 
convey the work and release it without changing its posture. 
The second embodiment of this invention is illustrated in FIGS. 4 and 5. 
The, the same reference characters are given to the same constituent parts 
as those in the above-described embodiment, and their detailed description 
will be omitted. 
A locking mechanism 50 for the suction pad according to this embodiment 
basically comprises a tubular body 54, a coil spring 58 wound up around 
the tubular body 54 from the top part of a flange 56 formed integrally 
with the tubular body 54, and an annular body 33, which is positioned 
above the coil spring 58 and on which one end of the coil spring 58 is 
seated. The root part 16 of the suction pad 10 is fitted to one end of the 
tubular body 54 by a means known per se in the art. 
Namely, the tubular body 54, in which a through-hole 54a extending in its 
axial direction has been defined, has the flange 56 integrally formed at a 
somewhat upper portion from its lower end. As understood from FIG. 5, the 
tubular body 54 is formed into a polygon, in this embodiment, a hexagon in 
cross section. 
In this embodiment, the annular body 33 is formed in such a manner that its 
inner wall surface is in a shape corresponding to the cross section of the 
tubular body 54, and is composed of a plastic. 
To prevent the annular body 33 from slipping out of the tubular body 54, a 
member for the prevention of slipping-out 55, in which a hole 55a is 
defined, is fitted to the top of the tubular body 54, and a pipe joint 60 
for connecting a tube 32 communicating with a vacuum and suction source is 
installed to the upper part of the member for the prevention of 
slipping-out 55. 
Incidentally, the coil spring 58 wound around the tubular body 54 is 
engaged with the annular body 33 at one end thereof and with the flange 56 
at the other end. 
In the above-described construction, there is a potential problem that the 
tube 32 connecting the vacuum and suction source to the tubular body 54 is 
twisted by the moving operation of a cylinder 38 upon the conveyance of a 
work, thereby forcing the angular movement of a work through the tubular 
body 54 and the skirt part 18. Alternately, there is also a potential 
problem that the momental movement of the work itself, which is caused by 
the moving operation of the cylinder 38, forces the work to turn. 
In this embodiment, however, since the cross sections of the tubular body 
54 and the hole defined within the annular member 33 substantially 
correspond to each other, and there is hence little space therebetween, it 
is possible to prevent the angular movement, thereby exactly releasing the 
work from the suction pad 10 to a desired position without changing its 
posture. 
Other embodiments of this invention are illustrated in FIGS. 6 and 7. 
In the third embodiment illustrated in FIG. 6, a ring-like groove is 
defined in the upper portion of a tubular body 54, and a ring 64 is 
inserted therein, thereby preventing an annular body 33 from slipping out 
of the tubular body 54. As a result, the structure of the mechanism can be 
made more simpler compared with those in the above-described embodiments. 
In the fourth embodiment illustrated in FIG. 7, the upper part of a tubular 
body 54 is formed into a cylindrical shape thinner by one rank to cut an 
external thread 54b in its outer wall surface. Two nuts 66a, 66b are 
screwed on the external thread 54b, thereby preventing an annular body 33 
from slipping out of the tubular body 54. In order to prevent the 
destruction of the annular body 33 made of a plastic due to a shock upon a 
collision of the nuts 66a, 66b against the annular body 33, a cushioning 
material 68 composed of a ring-like synthetic rubber is fitted to the top 
of the annular body 33. 
This embodiment has an advantageous effect that the displacing length of 
the tubular body 54 can be controlled by, shifting the positions of the 
nuts 66a, 66b. It is also possible to fit the cushioning material 68 under 
the nuts 66a, 66b. 
The tubular body 54 and the annular body 33 have been formed by a common 
plastic in a series of the embodiments described above. However, the use 
of those obtained by, for example, using a material impregnated with an 
oil or coating them with polytetrafluoroethylene has the effect of 
reducing the slide resistance upon the displacement of the tubular body 54 
in its axial direction. 
In addition to a series of the embodiments described above, it is also 
embraced in the present invention to form the annular body 33 by a 
conventional material and then insert a bush composed of a plastic inside 
such an annular body. 
Then, the fifth embodiment of this invention is illustrated in FIGS. 8 
through 11. 
In this embodiment, a cover member 20 has, in its outer periphery, a groove 
71 provided in its axial direction and grooves 72a, 72b, 72c provided in 
its circumferential direction. 
As illustrated in FIGS. 8 and 10, an annular body 33 is fitted over the 
cover member 20 at a portion near the top thereof. A thread is cut in the 
outer peripheral surface of the annular body 33. On the inner peripheral 
surface thereof, projecting parts 74 and 76 are formed respectively in its 
axial and circumferential directions. The annular body 33 is further 
provided with a cutout 77 over the whole length in its axial direction. 
After this annular body 33 is fitted over the cover member 20 in a state 
that the space of the cutout 77 has been widened (see FIG. 8), the 
projecting part 74 is fitted into the groove 71 by angularly moving the 
annular body 33, and the projecting part 76 is fitted into a desired 
groove 72a, 72b or 72c. 
In this embodiment, the groove 71 in the cover member 20 is engaged with 
the projecting part 74 of the annular body 33, whereby relative turning in 
the circumferential direction is prevented. One of the grooves 72a through 
72c is engaged with the projecting part 76, whereby the displacement in 
the axial direction is prevented. 
The annular body 33 can be expanded by widening the space of the cutout 77, 
thereby permitting the displacement thereof in the axial direction to fit 
the projecting part 76 into a desired groove 72a, 72b or 72c. Therefore, 
it is not necessary to cut a thread in the whole surface of the cover 
member 20, so that the processing becomes easy. 
Even when the replacement of parts are required due to difference in pitch 
of thread, or the like, it is only necessary to replace the annular body 
33. Therefore, the material cost becomes cheap and the replacing operation 
is simplified. 
An annular body 82 having partial cutouts 81 as illustrated in FIG. 11 may 
be used in place of the annular body 33. In this embodiment, it is 
desirable to use a flexible material such as a resin as a material for the 
annular bodies 33, 82. 
According to the present invention, it is possible to achieve the function 
of locking the angular movement of the suction pad with ease by forming 
the annular body and the tubular body in such a manner that their 
sectional configurations correspond to each other. It is therefore 
possible to very accurately release the work through the suction pad to a 
desired position without changing a posture of the work upon its 
conveyance. For this reason, the reliability on the conveyance of works in 
an automated factory can be enhanced. 
Since the annular bodies according to the present invention are formed by a 
plastic, it is possible to achieve lowering in cost and reduction in 
weight compared with the case where the annular bodies are made up of a 
metallic material. 
According to this invention, in addition, the first bush lower in slide 
resistance than the tubular body is fitted on the tubular body, while the 
second bush lower in slide resistance than the cover material is also 
fitted into the cover member so as to mesh the first and second bushes 
with each other, thereby permitting the displacement of the tubular body 
in the axial direction thereof. It is therefore possible to carry out the 
conveying operation of the work with good responsibility. With respect to 
these bushes, the use of those formed by, for example, using a 
thermoplastic resin impregnated with an oil or coating them with 
polytetrafluoroethylene, i.e., those formed by using a material having a 
lower slide resistance, also has a practical effect that there is no 
necessity of coating the contact surfaces of the bushes with grease or the 
like. 
Furthermore, according to this invention, the annular body can be fitted to 
an optional position of the cover member. Even when pitches of threads and 
sizes of screws are different, it is only necessary to replace the annular 
body. Therefore, the material cost becomes cheap and the replacing 
operation is also simplified.