Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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"Roller hemming head having a replaceable roller-carrying unit"
*..
Field of the invention
The present invention relates to roller hemming heads, of the type
comprising:
- an upper head portion, having a flange for connection to a robot
wrist or other movable supporting equipment, and
- a lower head portion, carrying at least a hemming roller.
Prior art
A roller hemming head of the above indicated type is disclosed for
example in WO 2012/160512 of the same Applicant. In this known
solution, the head has a lower portion comprising an outer cylindrical body
slidably mounted on an inner cylindrical body forming part of the upper
head portion. The lower head portion directly and freely rotatably supports
a pair of hemming rollers projecting from opposite sides of the head and
adapted to be used selectively during a hemming operation. The hemming
rollers have a common axis orthogonal to the common axis of the two
outer and inner cylindrical bodies of the head.
The exemplary embodiment shown in the above cited document
WO 2012/160512 provides for the hemming head to operate both
according to a "push" mode, i.e. with one of the two hemming rollers being
pushed with its lower side (with reference to a vertical orientation of the
head) against a piece to be hemmed, and according to a "pull" mode, i.e.
with the head being subjected to a pulling action, so that the upper side of
one of the hemming rollers (again with reference to a vertical orientation of
the head) is engaged against the piece to be hemmed.
The known hemming head comprises an upper helical spring and a
lower helical spring arranged aligned along the common axis of the outer
and inner cylindrical bodies of the head.
The ends of the upper and lower springs which are more remote
from each other are supported against end elements of the inner
cylindrical body, whereas the ends of the two springs which are closer to
each other rest on opposite faces of an intermediate support element
which is rigidly connected to the outer cylindrical body. In this manner,
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during the operation according to a "push" mode, it is the upper spring
which opposes the force tending to compress the head, whereas in the
"pull" mode, it is the lower spring which opposes the pulling force applied
to the head.
In the above mentioned known solution, a quick-release device is
also provided for uncoupling a single hemming roller from the head lower
portion. The release of the roller can be activated by any operating
member located outside of the head, which is engaged against a release
member provided adjacent to each hemming roller.
Solutions are also known of hemming heads which include a quick-
connection device at their upper end, through which the entire hemming
head carried by the robot can be quickly replaced. These solutions are
however uselessly complicated and expensive, in cases where only the
hemming rollers would need to be replaced. Moreover, the quick-
connection devices used in this case require providing the robot with
electric cables and hoses for supplying fluid under pressure, which are
necessary for controlling the operation of the quick-connection device.
Apart from their intrinsic cost, these cables and hoses have the drawback
to be subjected to continuous deformations during the operative life of the
robot, so that they must be periodically replaced due to wear thereof, thus
giving rise to additional costs and productivity losses caused by the
maintenance stops. Wear of cables and hoses is particularly high in the
case of a hemming head, since this head is often used for performing
hemming operations along the entire periphery of a component, which
implies that the head rotates by 360 on itself, which therefore subjects
cables and supply hoses of the quick-connection device to very high
torsional deformations.
Objects of the invention
The main object of the present invention is that of providing a roller
hemming head which enables the hemming rollers to be replaced and yet
has a simple and inexpensive structure, which does not require the
provision of additional electric cables and/or supply hoses on the robot
carrying the hemming head.
A further object is that of providing a hemming head which achieves
the above mentioned purpose through a new and advantageous head
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architecture, while not involving substantial increases in cost with respect
to the conventional hemming heads.
A further preferred object is that of providing a hemming head
which is more efficient and less complicated in use with respect to the
known solutions.
Summary of the invention
In view of achieving these objects, the invention provides a roller
hemming head comprising:
- an upper head portion, having a flange for connection to a robot
wrist or other movable supporting equipment, and
- a lower head portion, carrying one or more hemming rollers,
characterized in that said head further includes:
- a roller-carrying unit carrying the hemming rollers and adapted to
be separated as a whole from said head lower portion, and
- a quick-connection device which rigidly and removably connects
said roller-carrying unit to the head lower portion,
- said quick-connection device comprising:
- spring means tending to hold said device in a connected
condition,
- an actuating member movable against the action of said spring
means for releasing the connection, and adapted to be operated by an
engagement member, said engagement member being provided at a fixed
station adjacent to said robot or adjacent to said other movable equipment
supporting the head and being adapted to be received within a
cooperating seat of the head,
- in such a way that said quick-connection device does not require
the provision of cables and/or supply hoses on said robot or on said other
supporting movable equipment.
Therefore, in the present invention the hemming rollers of the head
are all carried by a single roller-carrying unit which can be separated as a
whole from the lower head portion and thus quickly replaced. This
represents an important difference with respect to the solution known from
WO 2012/0160512, in which the possibility of quick change of each single
roller was provided, and also with respect to conventional solutions in
which quick change of the entire hemming head is provided due to the use
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of a quick-connection device interposed between the hemming head and
the robot wrist.
Furthermore, in the hemming head according to the invention the
device for quick change of the roller-carrying unit does not require the
provision of electric cables and/or additional supply hoses on the robot,
which simplifies and lowers the cost of the robot structure. The elimination
of cables and the hoses on the robot is two-fold advantageous, since
these cables and hoses are subjected to continuous deformations during
the operative life of the robot, with the result that they must be
periodically
replaced, with additional costs and productivity losses due to maintenance
stops.
The present invention also provides a hemming fixed station,
comprising a robot or other supporting movable equipment, and a
hemming head having the above indicated features, carried by said robot
or by said other movable supporting equipment.
According to a further feature, the hemming head according to the
invention further comprises a fixed station adjacent to said robot or to said
movable equipment supporting the head, said fixed station including an
engagement member which can be engaged within a cooperating seat of
the head when said robot or said movable supporting equipment brings
the head to a position adjacent to said fixed station, in order to activate
the
actuating member for release of the connection between the lower portion
of the hemming head and the roller-carrying unit.
Preferably, at said fixed station there is provided also a movable
magazine for roller-carrying units, comprising a plurality of structures for
receiving the roller-carrying units, which can be moved along an open or
closed path, so that an empty receiving structure can be provided at a
position for receiving a roller-carrying unit when the latter is uncoupled
from the hemming head, and a receiving structure occupied by a new
roller-carrying unit can therefore be brought to said position for coupling
the new roller-carrying unit with the hemming head.
In the hemming head according to the invention, the quick-
connection device connecting the roller-carrying unit to the head lower
portion can be made according to any conventional technique.
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However, in one exemplary embodiment, this device is made
according to the teachings of document EP 1 810 777 Al, assigned to
Pascal Engineering Corporation. The quick-connection device disclosed in
this document is for connection of piece-carrying pallets onto pallet-
5 carrying structures provided along a pallet conveyor device. However, the
Applicant has found that this connection device can be advantageously
used also for the purposes of the present invention.
In the case of this known device, the actuating member which
causes release of the connection is operated by hydraulic means.
Therefore, in case the present invention makes use of this known device,
the above mentioned engagement member provided at the fixed station is
adapted to establish a hydraulic communication between a hydraulic
chamber provided within the connection device and a source of
pressurized hydraulic fluid. However, operation of the actuating member
for release of the connection could be obtained in any other way, such as
by means of pressurized air or also by mechanical means. In this latter
case, the engagement member which is received within the cooperating
seat on the hemming head comprises for example a pushing member
which engages a corresponding actuating member provided within the
seat of the head in order to cause release of the connection. Whatever is
the solution which is adopted, when the engagement member is retracted
from the corresponding seat in the head, the spring means provided in the
connection device automatically cause return of this device to a condition
of rigid connection between the new roller-carrying unit and the lower
portion of the hemming head.
Moreover, the head according to the invention preferably has the
further features which are indicated in the annexed dependent claims.
Brief description of the drawings
The invention will be now described with reference to the annexed
drawings, given purely by way of non- limiting example, in which:
figure 1 is a lateral diagrammatic view of a hemming head
according to the prior art, carried on the terminal portion of a multi-axis
industrial robot,
figure 2 is a view in cross-section and at an enlarged scale of the
hemming head of figure 1,
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figure 3 is a perspective view which shows a further known solution,
in which a device is provided for quick replacement of the hemming head
carried by a robot,
figures 3A, 3B are diagrammatic lateral views which show a
hemming head with the conventional head change device which is shown
in figure 3, compared with a head which is not provided with this device,
figure 4 is a perspective view of one embodiment of the hemming
head according to the invention,
figure 5 is a diagrammatic cross-sectional view of the hemming
head of figure 4,
figure 5A shows a detail of figure 5 at an enlarged scale,
figure 6 is a diagrammatic view in cross-section of a quick-
connection device known per se, which can be used in the hemming head
of the invention, and
figure 7 shows an exemplary embodiment of a hemming fixed
station according to the invention.
Detailed description of the invention
Prior art
Figure 1 shows one example of hemming head according to the
prior art known from WO 2012/160512. In this figure, reference numeral
10 generally designates a hemming head carried by a multi axis industrial
robot R, of which only the terminal part is visible, having a wrist 14 able to
move and orient the head 10 in a three-dimensional space. In an
exemplary application, robot R is electronically connected to a controller
(not shown) which is programmed for moving and orienting the hemming
head 10 along a predetermined path for performing a hemming operation,
according to what will be described more in detail in the following with
reference to figure 7 of the annexed drawings.
The head 10 according to the prior art includes an upper portion 20
rigidly connected to an universal connecting flange 22, of circular shape,
for connection to the robot wrist. The flange has a plurality of holes for
engagement of connecting bolts (not shown) for connection to the robot
wrist, according to a technique which is conventional per se. The hemming
head 10 further comprises a lower portion 24 which freely rotatably
supports two hemming rollers 26, 27 around a common axis 28 which is
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orthogonal with respect to the longitudinal axis 100 of the hemming head
10.
As shown in detail, in figure 2, in the head 10 according to the prior
art the lower head portion 24 comprises an outer cylindrical body 240
slidably mounted on an inner cylindrical body 200 forming part of the
upper portion 20 of the head, which is connected to the connection flange
22. The head 10 according to the prior art further comprises two helical
springs 30A, 30B aligned along the head axis 100. The ends of springs
30A, 30B which are more remote from each other rest against end
elements of the inner cylindrical body 20, whereas the ends of springs
30A, 30B which are closer to each other rest against opposite faces of an
intermediate element 32 which is rigidly connected to the outer cylindrical
body 240, through diametrically opposite slots formed in the inner
cylindrical body 200.
The hemming head 10 shown in figures 1, 2 can be used both
according to a "push" mode and according to a "pull" mode. In the "push"
mode, the robot 10 pushes the hemming head 10 against a piece so as to
use one of the two hemming rollers 26, 27 for performing the hemming
operation with the portion of the roller which faces downwardly (with
reference to figures 1, 2). In the "pull" mode the robot 12 pulls the
hemming head 10 towards the flange 22, i.e. upwardly with reference to
figures 1, 2, so as to use the upwardly facing side (with reference to the
figures) of one of the hemming rollers 26, 27 for performing the hemming
operation. In the "push" mode, the inner cylindrical body 200 which is
rigidly connected to the connection flange 22 tends to move downwardly
(with reference to figures 1, 2) with respect to the outer cylindrical body
240 carrying the hemming rollers, thus causing a compression of the
upper helical spring 30A. In the "pull" mode, the inner cylindrical body 200
tends to move upwardly (again with reference to the figures) with respect
to the outer cylindrical body 240, causing a compression of the lower
helical spring 30B.
According to what is indicated in document WO 2012/160512, each
of the hemming rollers 26, 27 can be quickly replaced by means of a
quick-connection device which can be operated by a robot or any other
automatic or manual mechanism adapted to engage a release device
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provided on the head. However there is nothing in this document which
anticipates or suggests the idea which is at the basis of the present
invention, i.e. the provision of a unit carrying the hemming rollers which
can be uncoupled, as a whole, with respect to the lower portion of the
hemming head.
Figure 3 of the annexed drawings shows a further known solution
used by the same Applicant, in which a hemming head similar to that of
figures 1, 2 can be quickly uncoupled from the robot by which it is carried
with the use of a quick-connection device 30 interposed between the
connection flange 22 located at the upper end of the hemming head 10,
and the robot wrist (not shown in figure 3). In this known solution, the
quick-connection device 34 is of a type which requires the provision on the
robot of electric cables 36 and hoses 37 for supplying pressurized air,
which are necessary for controlling the operation of the quick-connection
device 34.
Apart from the intrinsic cost, these cables and hoses have the
drawback of being subjected to continuous deformations during the
operative life of the robot, with the result that they must be periodically
replaced because of wear thereof, thus giving rise to additional costs and
productivity losses caused by maintenance stops. Wear of cables and
hoses is particularly high in the case of a hemming head, since the head
is often used for performing hemming operations along the entire
periphery of a component, which implies that the head performs a 360
rotation on itself, subjecting cables and supply hoses of the quick-
connection device to very high torsional deformations.
Figure 3A of the annexed drawings also shows a conventional
solution of the type of that of figure 3, in which the hemming head 10 is
provided with the quick-connection device 34 and therefore requires the
provision of cables and hoses for supplying the device 34. The
comparison with figure 3B, which shows the head without device 34,
makes the disadvantage clear, also in terms of a greater bulk deriving
from the large size of device 34. Moreover, the cables and supply hoses
of device 34 must be arranged inside the robot, so that they require the
provision of corresponding supports on the robot, which generates further
bulk and complications. Moreover, the provision of cables outside the
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robot is a possible source of problems due to interference with foreign
bodies which may be located at the work fixed station. Starting from this
state of the art, the invention has the object of finding a solution which
overcomes the above indicated drawbacks.
Description of the preferred embodiment
Figures 4-6 of the annexed drawings show an exemplary
embodiment of the hemming head according to the present invention. In
these figures, the parts in common to those of figures 1, 2 have been
designated by the same reference numerals.
As indicated in the foregoing, a main feature of the hemming head
according to the present invention is that in this head the hemming rollers
26, 27 are freely rotatably supported by a roller-carrying unit 40 which can
be separated as a whole from the lower portion 24 of the hemming head
10. To this end, between the roller-carrying unit 40 and the outer
cylindrical body 240 forming part of the lower portion 24 of the head there
is interposed a quick-connection device 50 of any known type, which
connects a circular flange 42 provided on the roller-carrying unit 40 to a
circular flange 242 secured to the lower end of the outer cylindrical body
240. In the case of the illustrated example, the connection device 50 is
provided according to the teachings of document EP 1 810 777 Al in the
name of Pascal Engineering Corporation. The above mentioned document
shows this quick-connection device with reference to connection of a
piece-carrying pallet to pallet-carrying structures of a pallet conveyor.
However, the applicant has found that this device can be advantageously
used also in the application illustrated herein.
In view of that the device 50 shown in the drawings is known per se,
it is described herein only with reference to its general features.
As shown in figure 6, device 50 comprises a first coupling member
51 which is rigidly connected to the roller-carrying unit 40 and a second
coupling member 52 constituted by a piston movable inside member 51.
Inside device 50 there is provided a hydraulic chamber 53 which can be
fed with fluid under pressure for moving piston 52 downwardly (with
reference to figure 6) against the action of a group of Belleville springs 54.
Springs 54 are interposed between an end head 52a connected to piston
52 by a stem 52b, and the body of the coupling member 51. Between the
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coupling member 51 and piston 52 there are interposed ball elements 55.
The Belleville springs 54 normally hold piston 52 in a raised position (with
reference to figure 6) in which the ball elements 55 axially hold the
coupling member 51 with respect to piston 52. When fluid under pressure
5 is fed to
chamber 53, piston 52 moves downwardly (with reference to
figure 6) against the action of the Belleville springs 54, reaching a position
in which the ball elements 55 enable axial uncoupling of member 51. In
the coupled condition, the device comprises also further coupling
elements (not shown in figure 6) for locking the two coupling members
10 with respect to relative rotations. As indicated above, a detailed
description of the device 50 is anyhow provided in document EP 1 810
777 Al, which forms part of the state of the art.
The supply of fluid under pressure to chamber 53 of connection
device 50 is performed at a fixed station for change of the roller-carrying
unit, shown by way of example in figure 7 and designated therein by
reference S. At station S there is provided an engagement member 60
which is to be received within a cooperating seat (not shown in the
drawings) of the connection device 50 for providing a hydraulic
communication between chamber 53 of the connection device 50 and an
outer source of fluid under pressure.
The connection device illustrated herein is however provided purely
by way of non-limiting example, it would be possible to use a similar
device in which operation of the piston element 52, which acts as
actuating member for release of the device, is obtained for example by
supply of air under pressure, or by a mechanical action. In this latter case,
the engagement member 60 is a pushing member adapted to be received
within the cooperating seat of the connection device and to operate the
movable member of the connection device 50 connected in any known
way to the release actuating member of the device.
It is also possible to use a quick-connection device of any
conventional type, also different from that described above purely by way
of example.
Figure 7 of the annexed drawings shows, purely by way of example,
the application of the invention to a hemming fixed station provided in a
plant for production of motor-vehicle doors, for performing a hemming
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operation on two sheet-metal panels which form the structure of the door,
along the periphery of the door.
According to a technique known per se, the door structure D is
placed in a horizontal position above a cradle C carried by a basement B.
The door structure D is pressed above cradle C by a pressing member P
carried at the lower end of a column P1 which is vertically movable. The
hemming operation is carried out by means of a hemming head 10
according to the invention. The head is mounted on the wrist 14 of a multi-
axis articulated robot R of any known type. The robot comprises a base
structure R and a plurality of robot elements mutually articulated to each
other, which connect a base structure R1 to the robot wrist 14. As already
indicated in the foregoing, the operation of the robot is controlled, in a way
known per se, by a controller of any known type programmed for moving
the hemming head 10 according to a predetermined path in a
predetermined way. During the hemming operation, one or the other of the
two hemming rollers 26, 27 is used, depending upon the required
operation.
When it becomes necessary to replace the roller-carrying unit 40, the
robot carries the hemming head 10 to the fixed station S, where there is
provided a movable magazine M for structures 70 adapted to receive.and
support roller-carrying units 40. In the case of the example
diagrammatically shown in figure 7, structures 70 are movable along a
predetermined path by means of a conveyor 80 of any known type. In the
preferred embodiment, conveyor 80 has an arrangement in the form of a
horizontal carousel (only a portion of which is visible in figure 7) along
which structures 70 are movable, in one direction or in the other. In this
manner, when it is necessary to replace the roller-carrying unit 40 carried
by the hemming head 10 which is mounted on robot R, at station S there
is provided an empty structure 70, which is for receiving the worn roller-
carrying unit. Once robot R has brought the hemming head 10 above this
empty structure 70, the engagement member 60 is automatically extended
for engaging a cooperating seat on the quick-connection device of the
hemming head 10. In this manner, release of the connection is activated
and the roller-carrying unit 40 is deposited on the correspondent structure
70. Conveyor 80 is then moved for bringing a structure 70 carrying a new
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roller-carrying unit 40 to station S, so that the new unit can be engaged
rapidly by the hemming head 10 and then connected rigidly to the latter by
disengagement of the engagement member 60, so as to bring the quick-
connection device to the rigid connection condition, due to the action of
springs 54. Once this operation has been performed, the robot can bring
the hemming head back to a piece to be hemmed, for performing a new
hemming cycle.
With reference to figures 5, 5A, the preferred embodiment of the
hemming head according to the invention has further advantageous
differences with respect to the known hemming head shown in figures 1,
2, which will be discussed in the following. However, it is well understood
that the present invention includes providing a roller-carrying unit
separable, through a connection device, from the lower portion of the
hemming head in a hemming head of any known type, including also the
head of figures 1, 2.
A first additional difference of the preferred embodiment with respect
to the head of figures 1, 2 lies in that the two springs 30A, 30B are guided
by a spring-guiding stem 31 arranged axially through the two springs and
through the intermediate supporting element 32.
Moreover, in the preferred embodiment the load applied to the
hemming head during the hemming operation is monitored both during an
operation according to a "pull" mode and in an operation according to a
"push" mode, by means of two respective force sensors (load cells) 33
which are interposed between the ends of springs 30A, 30B which are
more remote from each other, and the respective end elements of the
inner cylindrical body 200.
The lower end of a spring-guiding stem 31 is connected to a disk 39
(figure 5A) on which the lower end of the lower spring 30B rests, by
means of a bayonet coupling, including a transverse pin 35 carried by
stem 31 and a shaped slot 37 formed in a cylindrical skirt projecting from
disk 39 and engaged by one end of the transverse pin 35.
The shape of slot 37 is such that the mounting operation is carried
out in the conventional manner used for bayonet couplings, i.e. by a first
axial movement of disk 39, which causes a compression of lower spring
30B, followed by a rotation of disk 39 and subsequent axial release, under
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the action of the lower spring 30B, towards a final locked position. The
locking of the coupling is therefore ensured by the lower spring 30B itself.
Due to this arrangement, the mounting of the unit can be carried out in a
simple and quick manner.
According to a further important difference, the load of the two
springs 30A, 30B, can be adjusted by acting, at each of the two ends of
the springs which are more remote from each other, on a screw 220
(figure 5A) which engages an internally threaded bush 230 which is
prevented from rotation with respect to the inner cylindrical body 200 by
means of a key 250 and which further engages a threaded portion 260
projecting from the body of the respective sensor 33. A rotation of screw
220 modifies the axial position of the threaded bush 230 with respect to
the inner cylindrical body 200 of the head. The body of sensor 37 has a
threaded portion 260 also on the side facing towards disk 39, which is
received within a threaded axial hole of disk 39.
During the registering operation of the load of springs 30A, 30B, the
axial relative position of the outer cylindrical body 240 and the inner
cylindrical body 200 is locked by inserting a locking pin through aligned
holes (not shown in the drawings) of these cylindrical bodies.
The above described system for adjustment of the load of springs
30A, 30B represents a substantial step forward with respect to what has
been provided today in systems of the type shown in WO 2012/160512. In
these known systems, in order to control the load of a spring it is
necessary to measure the length of the spring in an undeformed condition,
to measure the actual length of the space in which the spring is mounted,
and then to insert a number of shims or washers which ensure the desired
compression. Also in these known systems, if the spring is broken before
it can be replaced it is necessary to measure a new spring, to check the
measure of the length of the mounting space and to provide the required
shims for reproducing the same value of load.
With the new above described adjustment system, it is possible to
finally adjust the load value, by reproducing exactly the same load value
even upon changing the spring (the tolerance on the spring length being
large) since by screw 220 it is possible to recover the clearances and to
reproduce the desired load. In this manner, it is possible to reproduce
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identical adjustments between different hemming heads exactly,
independently from the manufacturing tolerance of the systems.
Furthermore, with sensor 33 it is possible to evaluate the integrity of the
spring during the use of the head.
In the case of the present invention, the above described mounting
and adjustment operations can be performed easily in a condition in which
the roller-carrying unit 40 is removed from the head.
Naturally, while the principle of the invention remains the same, the
details of construction and the embodiments may widely vary with respect
to what has been described and illustrated purely by way of example,
without departing from the scope of the present invention.
In particular, as already indicated in the foregoing, the basic feature
of the invention, lying in the provision of a separable roller-carrying unit
can be adopted in a roller hemming head of any type.
Also the arrangement of the fixed station S for change of the roller-
carrying unit can be different from that which has been disclosed herein
purely by way of example.
