[0001] The device this invention relates to consists in a uncomplicated automatic mechanism
for feeding blind rivets of the type which include a rivet body or head portion, an
annular flange or washer and a removable stem or pin, and which are designed for being
arranged in the opening of a standard oil-pneumatic or pneumatic riveting machine
usually marketed, with a head section which embodies a chuck which includes a gripping
mechanism to lock the rivet pin or stem positioned within it, and a dynamic fluid
cylinder for closing the said gripping mechanism and applying a backward tensile stress
in order to deform the rivet head portion until the said stem is detached, which is
being removed by suction through an duct axial to the said heat section, embodying
likewise in general, means for individual feeding of the said rivets, for example
by pneumatic conveyance, in a predetermined position toward the riveting gun.
[0002] The device according to the invention was devised to constitute a set together with
a pistol-type riveting machine which allows its use as self fed hand riveting pistol,
to be incorporated to robot arms or, using suitable supports, work as a machine or
static unit of automatic riveting, having access only by one of the sides of the two
pieces to connect.
[0003] As backgrounds of the invention, we can mention patents EP 285739, EP 491193, US
4205547, US 4027520, US 5042131, FR 7012434 and FR 8613059.
[0004] The European patent EP 285739 discloses a device for positioning blind rivets, which
is associated to a pistol body to which the blind rivets are fed, one by one, with
the pin or stem in back position, comprising a collet which, through a set of levers
moves to position the pin of related rivet in the interior of the front opening or
mouth of the riveting head. The device proposed is complex, it takes a significant
place, namely close to the front part of the riveting tool, which limits the operation
freedom and when moving the rivet outside the said riveting tool, there exists the
risk of causing accidents when handling the set. In addition, with this device a certain
number of cycles could fail, due to a poor pointing of the rivet pin in the mouth
of the riveting head, because of lack of guide.
[0005] In the European patent EP 491193, it is disclosed an apparatus for feeding rivets
to the front section of a riveting machine, where the rivets are presented and fed
joined in a tape or support feeder, which moves forward on a slide, and by means of
a lever which moves externally to the riveting tool, they are taken one by one and
positioned in front of the riveting tool. A rivet positioning device embodying a tape
or rivet feeder is likewise disclosed in above patent FR 7012434. These devices have
the main drawback of requiring the said rivet tape (preparation and feeding), with
subsequent incremental cost and manoeuvrability loss of the set, in addition to imply
a significant structural complexity due to the support and forward movement means
of the said slide in coordination with the own means of the riveting tool. In addition,
rivets evacuation is performed directly down the floor or in an auxiliary deposit
and in addition the scraps of the bearing tape have to be picked up.
[0006] Patent US 4205547 proposes a rivet positioning device, which includes likewise a
set of levers and collet outside the riveting tool for positioning the rivet pin or
stem in the interior of the front opening of the riveting head. The said levers are
mounted on a slide external to the body of the riveting tool for its displacement
from a rivet collection point up to another one for conveying it to the said collet.
This device likewise means a significant structural complexity and is very bulky,
therefore it affects the tool manoeuvrability. French patent FR 8613059 discloses
a device having similar characteristics, designed for a robot unit with guiding means
for mentioned positioning levers.
[0007] Patent US 5042131 discloses a device to feed rivets to a riveting tool, comprising
a duct which leads to a recess, coaxial to and in the front of the riveting head ,
the end portion of the said duct being pivoting with respect to the grips of that
riveting head, which, when moving forward takes the said tube sideward until catching
the rivet by its pin , and when it goes backward, the tube returns to its feeding
position. This device has the drawback of an irregular positioning of the rivets due
to a poor orientation of the pivoting tube, which, in addition, sustains a wear because
of the friction with the riveting head, compelling to use specially resistant and
expensive materials, or to replace the said tube from time to time. The evacuation
of the pins detached from the rivet requires that an auxiliary deposit is coupled
to the riveting tool with subsequent increase of weight and limitation in the manoeuvre
of the set. In this device, the collets which lock the rivet must be exaggeratedly
opened (with subsequent over-effort on the retraction spring) to let the riveting
head passes.
[0008] As for patent US 4027520, it does not disclose a device that can be associated to
a riveting tool, but a special gun in which the rivet is conveyed by pneumatic conveyance
close to the front end of the said gun, having access to the interior of a recess
frontally delimited by means of flexible collet, being thereafter held by a grip which
is moving forward toward the said recess, and pushed until the rivet head portion
protrudes externally to the gun and is ready for the riveting operation. The said
structure is not applicable to a conventional riveting gun or tool, as in above disclosed
devices, and, in addition, the initial position of the rivets in the said recess is
critical, as they are conveyed to the said point by fluid dynamic means and at a certain
speed, which may produce an incorrect arrangement of the rivet in the said recess
which gives rise to problems, and requires that means for a temporary retention of
the rivet in that recess are provided, until the rivet is held by the grip of the
riveting tool. In addition, the expelling of rivet pins after the riveting operation,
is performed directly outside, or it requires that a collecting container associated
to the gun is provided, which, once more, means a restriction of the manoeuvrability.
[0009] The device this invention is referring to tries to overcome above problems, and proposes
for such purpose means and a methodology for positioning the rivets in the front section
of a quite simple riveting tool, constituting a set applicable to any conventional
tool such as a riveting gun or similar, which means a minimum volume increase and
which virtually does not affect the working front section, involving only a slight
increase of weight and therefore an optimum manoeuvrability of the set with evacuation
of the rivet pins axially to the riveting tool, backwardly and up to a collection
point at a distance from the working point, and a very safe positioning of the rivets
allowing them to be held by the grips. The device is, in addition easily adaptable
to any riveting tool and, namely, it is applicable as it has been said to riveting
guns.
[0010] For such aim, the device involved comprises a support associated to the riveting
tool body dealt with, on which side pneumatic cylinders are fasten to, the said cylinders
causing that an external casing which surrounds the gripping mechanism front end of
the said riveting tool moves forward or backward, in due time, and which telescopically
slides on itself. This casing incorporates at its end a plurality of collet fingers,
in radial arrangement around an axis coaxial to the gripping mechanism axis, hinged
by its back end to the casing, and which may be opened, defining a front central opening
for the rivet passing, or to remain closed, locking the said rivet pin, an external
elastic ring having been provided which tends to keep the said collet fingers in a
closed position and a collar which encloses the back ends of the said collet fingers,
with a small play. The casing possesses in addition an inlet side duct for the rivets
conveyed by compressed air, according to conventional art, in a predetermined position.
[0011] The device is following disclosed together with its methodology illustrated by means
of its operation cycle:
When the external casing is fully taken far from the gripholder, forwardly, a recess
is formed between the gripholder and the collet fingers located at the end of the
said casing, in whose interior comes the rivet through a side manifold connected to
the inlet duct and coming from an automatic dosing vibrator located in a self-contained
piece of furniture which incorporates the electro-pneumatic installation.
[0012] When the external pneumatic cylinders makes the casing goes backward, the chamber
existing between the fingers in radial arrangement and the pistol gripholder becomes
shorter; this provokes that by means of some internal conicities performed on the
internal face of the said fingers and an exchangeable guiding nozzle, superposed to
the gripholder, the rivet is centered, its pin goes into a duct central to riveting
grips and thanks to a retractable pivot incorporated in the gripholder which at a
certain time obturates the said central duct, the rivet is outwardly pushed forcing
in opening the collet fingers and remaining finally held by their pin, by the said
fingers, ready for the riveting operation.
[0013] Once riveting is performed, the pin detached from the rivet head portion remains
locked by the riveting grips. The two external cylinders make the casing moves forward,
the retractable pivot is taken apart releasing the central duct, at same time that
the riveting grips release the pin which is sucked backward by a vacuum pump and conducted
through a tube toward a collector located in a self-contained piece of furniture.
At same time these operations are performed, the following rivet is automatically
introduced in the recess.
[0014] The displacement of the said retractable pivot is performed by means of a cam shape
which operates it in correspondence with the forward movement of the casing toward
the grip mechanism, or by a lever mechanism, driven by a pneumatic cylinder, controlled
by a sequentially programmed electronic device to push the said pivot toward a position
of interference with the central duct of the grip mechanism in due moment and regardless
of the casing movement. A spring coaxial to the said retractable pivot tends to keep
it apart from its position of intercepting the axial duct of the grip mechanism.
[0015] The above and other objects, features and advantages of the invention will become
more readily apparent from the following description, reference being made to the
accompanying drawings in which :
Fig. 1 is a top plan view of a riveting pistol incorporating a device according to
the invention, in whose upper half, located above the lengthwise symmetry axis, the
cylinder with the stem which operates the casing is shown in a retracted position;
in the half located under the said symmetry axis, the said stem appears extended.
Fig. 2 shows a longitudinal view partially in section, of the set of Fig. 1, by the
plane of section II - II, with the casing in advanced position, the recess which is
formed in its interior in the front of the grips of the riveting tool, lodging a blind
rivet.
Fig. 3 is a part section view, at larger scale, of the end portion of the casing,
with detail of the assembly of one of the collet finger it embodies.
Fig. 4 corresponds to a lengthwise view partially in section, of the set of Fig. 1,
by the section taken along the plane IV - IV, with the casing in retracted position
and the rivet located at the grip of the tool in a position ready for riveting.
Fig. 5 is a front view of the tip of the moveable casing, which allows to see the
three collet fingers it embodies, in the disclosed example.
Figs. 6, 7 and 8 show three views in side elevation and part lengthwise section, of
a pistol equipped with a device for feeding rivets, according to the invention, provided
with means alternative to those of the drawings of the three first figures to displace
the retractable pivot to a position of interference (a situation which is shown in
Fig. 7), designed to intercept the central duct of the grip mechanism.
[0016] The device according to the invention is applicable to the positioning of blind rivets
formed by a rivet 2 body or head portion -2-, a flange or washer -3- and a pin or
stem -4-, removable (see Fig. 2), in a riveting machine such as a fluid dynamic riveting
pistol -10-, with a section of head which embodies a chuck -17- fed with a spring
-7-, the said chuck comprises a gripping mechanism -25- designed for holding the pin
-4- of the rivet positioned within thereof, and an internal fluid dynamic cylinder
to close the said gripping mechanism and to apply a tensile stress with the purpose
of deforming the rivet head portion -2- until detaching the said pin -4-, which is
evacuated through a duct -9- axial to the said head section, which likewise embodies
means for individual feeding of the said rivets such as a pneumatic conveyance, at
a predetermined position, toward the said riveting pistol.
[0017] The device, according to the invention, is characterized in that it includes:
- a casing as a sleeve -12-, which surrounds the front end of the gripping mechanism
-25- of the riveting pistol, in coaxial arrangement thereof, the said casing -12-
internally defines a recess -32- and is finished a- its front section by a collet
-1- with a central hole -33- which, in its internal face, has a conic profile;
- a manifold -5- in a side of the casing -12- defining a passageway to supply rivets
to the interior of the said recess -32- conducted by the said pneumatic conveyance
means through a duct -35-, coupled to the said manifold -5-.
- a nozzle -13-, exchangeable, placed in superposition and alignment with the end of
the duct -34- central to the gripping mechanism -25-, the said nozzle offers a conical
profile oriented facing the distal end, provided with the said collet -1-, of the
casing -12-;
- means to displace in a predetermined distance the said casing, lengthwise and telescopically
with respect to the end of the chuck, co-aligned with the central duct -34- of the
gripping mechanism -25-, to place the rivet pin --4-, guided by the nozzle -13-within
the said duct -34-;
- means to intercept the axial duct -34- of the gripping mechanism -25- constituting
a stop limiting the insertion for the rivet pin -4-, determining when ending the displacement
of the said casing -12- a positioning of the said rivet such that the flange -3-thereof
protrudes from the elastic collets -1- and the rivet head portion -2- remains outside
the set ready for its insertion in a hole of a workpiece.
[0018] In the embodiment given as example in the drawings, the said manifold -5- supplying
the rivets, has an inclined orientation with respect to the lengthwise axis of the
chamber -32- and has connected a flexible duct -35- to feed the rivets, the manifold
-5- remaining in opposition with respect to the riveting pistol -10- handle or to
a supporting element of the riveting tool involved.
[0019] The means for displacing the casing -12, telescopically with respect to the chuck
of the riveting pistol, comprise external pneumatic cylinders supported on a support
-22- secured to the riveting pistol -10- body, and drawn in their two positions of
retraction and extension in the two semi-halves of figure 1. The stems --14- which
are oriented in parallelism to the duct axis -34-, are connected by their ends to
some appendages -18- solid with the casing -12- as it is shown in figures 1, 7 and
8. Fig. 1 likewise details an elastic stop -20-, coaxial to the said stems -14- designed
to limit the displacement in retraction of the casing -12-. And a part -18- or coupling
nipple of the pistol axial duct -9- (Fig. 2) is shown with a vacuum pump --11- for
evacuating the pins detached from the rivets, which are advantageously conducted to
a far collection point, by a flexible tubular duct -23-.
[0020] As it can be seen in figures 3 and 5, the collet -1-, in the front part of the casing
-12-, comprises a plurality of collet fingers -36- in radial arrangement around a
coaxial axis with the central duct -34-, of the gripping mechanism -25-, hinged by
their back end, which may be opened forming a front central opening having a diameter
slightly larger than the washer -3- and body -2- of the rivet, or may remain closed
defining a central front hole - 33-, suitable to lock the pin -4- of the same rivet,
an external elastic ring -37- having been designed which tends to keep the said fingers
-36- in closed position, and a collar -39- attached to the casing -12- which encloses
the said back ends of the fingers -36-, with a small play. The articulation of the
fingers -36- of the collet comprises an offset -38- of the said fingers back end,
which is supported on an annular element -41- socketed in an annular groove -42- of
the casing -12- external surface.
[0021] As it can be seen in figures 2 and 6, a sleeve -24-connects the casing -12- to the
body -10- front end of the riveting pistol, acting as guard.
[0022] The means to intercept the duct -34- during the displacement of the casing -12- in
order to constitute a penetration stop for the rivet pin -4-, in its access within
the said duct, comprises a pivot -15- inserted in a drilled hole -8- lateral to the
duct -34- which flows at a predetermined distance of the front end of the said duct,
the said pivot -15- is retractable thanks to a coaxial spring -16-, which tends to
displace it outwardly of the said drilled hole -8-, in such a way that its end does
not intercept the duct -34-, means having been designed to displace the said pivot
-15-, compressing the said spring - 16-, in a way that its end interferes the duct
-34- and acts as insertion limiting stop of the pin -4- in the said duct -34-.
[0023] The means to provoke a displacement of the pivot -15-comprise an offset with a regular
profile bottom ending in a ramp -31- at the casing -12- internal face, the said offset
remains facing like a sliding track with the external end of the said pivot -15-,
in a way that the interposition of the pivot in the duct -34- occurs in coordination
with the linear backward run of the casing - 12-.
[0024] As stated above in figures 6 to 8, alternative means have been represented, on the
ground of the same principle of the invention, to provoke a displacement of the pivot
- 15- comprising a set of levers, -26-, -27-, -28- driven by a pneumatic cylinder
-29- and coupled thereto by the part - 30- controlled by a sequentially programmed
electronic device, to actuate , through an electrovalve the cylinder - 29- and to
displace the pivot -15- to a position of interception of the duct -34-, at any moment,
and regardless the casing -12- movement. With that it is achieved that the pistol
may work in any orientation and namely in upright position, upwardly riveted, avoiding
that the pin -4- could accidentally penetrate within the duct - 34-, without this
later being intercepted by the pivot -15.
[0025] The method to feed rivets according to above explanation comprises following phases:
- conveyance of a blind rivet comprising a rivet head portion or body (2), a flange
or washer -3- and a stem or pin -4-, removable, in a predetermined position within
the recess -32- of the casing -12- enclosing the front end of the gripping mechanism
-25- of the riveting tool;
- telescopic linear displacement, of predetermined length, of the said casing -12- coaxially
and approaching the end of the said gripping mechanism -25-, to place the pin -4-,
of the rivet within the central axial duct -34- of the said mechanism -25-;
- obturation of the axial duct -34- of the gripping mechanism forming a penetration
stop of the said pin in the said duct, in coordination with the displacement of the
casing -12- or independently thereof, at any time of the cycle, to oblige the portions
-2- and -3- of the rivet to protrude from the said casing -12- by a distal end, provided
with elastic collets -1-;
- evacuation of the pin detached from the rivet after riveting, performed according
to conventional art, by the riveting tool or pistol to which the device is applied,
through the duct -34- of the gripping mechanism and an axial canal -9- which is connected
with an evacuation area located far from the riveting tool.
- feeding of a new rivet which remains retained against the front external wall of the
riveting tool, until the casing -12- returns to its initial feeding position, of maximum
remote place with respect to the gripping mechanism -25-, a moment in which, as a
passageway through the manifold -5- lateral to the casing -12- becomes free, the rivet
has access to the recess -32- impelled by compressed air.
[0026] The last mentioned step, guarantees that the rivet has access to the recess -32-
at low speed, because of the short distance to run from the bottom of the manifold
--5-, where it has been impelled by pressurized air through the tube -35-, avoiding
this way rebounds and in general incorrect positioning, as those which may be produced
in the event of above mentioned patent US 4027520.
[0027] It is stated that other variants can be conceived, inspired in the essentiality of
the invention which is summarized in following claims.
1. Device for a front automatic rivet feeding of a riveting machine particularly applicable
to the positioning of blind rivets formed by a rivet body or head portion (2), a flange
or washer (3) and a removable pin or stem (4), in a riveting machine such as a fluid
dynamic riveting pistol (10), with a section of head which embodies a chuck (17) which
comprises a gripping mechanism (25) designed for holding the pin (4) or stem of the
rivet positioned within thereof, and some fluid dynamic cylinders to close said gripping
mechanism and to apply a tensile stress with the purpose of deforming the rivet head
portion (2) until detaching the said pin (4), which is evacuated through a duct (9)
axial to said head section, the device also comprising means for an individual feeding
of the said rivets, such as a pneumatic conveyance, at a predetermined position, toward
the said riveting pistol,
characterized in that it comprises:
a) a casing as sleeve (12), which surrounds the front end of the gripping mechanism
(25) of the riveting pistol, in coaxial arrangement, the said casing (12) internally
defining a recess (32) and is finished at its front section by a collet (1) with a
central hole (33) which, in its internal face, has a conic profile;
b) a manifold (5) in a side of the casing (12) defining a passageway to supply rivets
to the interior of the said recess (32), supplied by the said conveyance means through
a duct (35), coupled to the said manifold (5).
c) a nozzle (13), exchangeable, placed in superposition and alignment with the end
of the duct (34) central to the gripping mechanism (25), the said nozzle having a
conical profile oriented facing the distal end, provided with the said collet (1),
of the casing (12);
d) means to displace a predetermined distance said casing, lengthwise and telescopically
with respect to the end of the chuck, co-aligned with the central duct (34) of the
gripping mechanism (25), to place the rivet pin (4), guided by the nozzle (13) within
the said duct (34);
e) means to intercept the axial duct (34) of the gripping mechanism (25) constituting
a stop limiting the insertion for the rivet pin (4), determining when ending the displacement
of the said casing (12) a positioning of the said rivet such that the flange (3) thereof
protrudes from the elastic collets (1) and the rivet head portion (2) remains outside
the set ready for its insertion in a hole of a workpiece.
2. Device according to claim 1, characterized in that said manifold (5) supplying the
rivets, has an inclined orientation with respect to the lengthwise axis of the chamber
(32) co-aligned with the duct (34) of the gripping mechanisms (25) and to said manifold
(5) a flexible duct (35) to feed the rivets is connected, the manifold (5) remaining
in opposition with respect to the riveting pistol (10) handle or to a supporting element
of the riveting tool involved.
3. Device according to claim 1, characterized in that the means for displacing the casing
(12, telescopically with respect to the chuck of the riveting pistol, comprise external
pneumatic cylinders (21) sustained on a support (22) secured to the riveting pistol
(10) body, and which stems (14), which are oriented in parallelism to the axis of
the duct (34), are connected by their ends through some appendages (19), to the casing
(12).
4. Device according to claim 1, characterized in that the collet (l), comprises a plurality
of collet fingers (36) in radial arrangement around an axis coaxial with the central
duct (34), of the gripping mechanism (25), hinged by their back end, which may be
opened forming a front central opening having a diameter slightly larger than the
washer (3) and body (2) of the rivet, or may remain closed defining a central front
hole (33), suitable to hold the pin (4) of the same rivet, an external elastic ring
(37) having been designed which tends to keep the said fingers (36) in closed position,
and a collar (39) attached to the casing (12) which encloses the said back ends of
the fingers (36), with a small play.
5. Device, according to claim 4, characterized in that the articulation of the fingers
(36) of the collet comprises an offset (38) of the said fingers back end, which is
supported on an annular element (41) socketed in an annular groove (42) of the casing
(12) external surface.
6. Device, according to claim 1, characterized in that a sleeve (24) connects the casing
(12) to the body (10) front end of the riveting pistol, acting as guard.
7. Device, according to claim 1, characterized in that the means to intercept the duct
(34) during the displacement of the casing (12) in order to place the rivet pin (4)
within the said duct, comprises a pivot (15) inserted in a drilled hole (8) lateral
to the duct (34) which flows at predetermined distance of the front end of the said
duct, said pivot (15) being retractable thanks to a coaxial spring (16), which tends
to displace it outwardly of said drilled hole (8), in such a way that its end does
not intercept the duct (34), having been designed means to displace said pivot (15),
compressing said spring (16), so that its end interferes the duct (34) and acts as
insertion limiting stop of the pin (4) in the said duct (34).
8. Device, according to claim 7, characterized in that the means to provoke a displacement
of the pivot (15) comprise an offset with a regular profile bottom ending in a ramp
(31) at the casing (12) internal face, the said offset remaining facing like a sliding
track with the external end of the said pivot (15), so that the interposition of the
pivot in the duct (34) occurs in coordination with the linear backward run of the
casing (12)
9. Device, according to claim 7, characterized in that the means to cause a displacement
of the pivot (15) comprise a set of levers, (26), (27), (28) driven by a pneumatic
cylinder (29) controlled by a sequentially programmed electronic device, to actuate,
through an electrovalve the cylinder (29) and to displace the pivot (15) to a position
of interception of the duct (34), at any moment, and regardless the casing (12) movement.
10. Method for a front automatic rivet feeding to a riveting machine characterized in
that it comprises following phases:
a) conveyance of a blind rivet comprising a rivet head portion or body (2), a flange
or washer (3) and a stem or pin (4), removable, in a predetermined position within
the recess (32) of a casing (12) enclosing the front end of a gripping mechanism (25)
of a riveting tool;
b) telescopic linear displacement, of predetermined length, of said casing (12) coaxially
and approaching the end of the said gripping mechanism (25), to place the pin (4),
of the rivet within the central axial duct (34) of said mechanism (25);
c) obturation of the axial duct (34) of the gripping mechanism forming a penetration
stop of the said pin in the said duct, in coordination with the displacement of the
casing (12) or independently thereof, at any time of the cycle, to compel the portions
(2) and (3) of the rivet to protrude from said casing (12) by a distal end, provided
with elastic collets (1);
d) evacuation of the pin detached from the rivet after riveting, through an axial
duct (34) of the gripping mechanism and an axial canal (9) which is connected with
an evacuation area located far from the riveting tool.
e) feeding of a new rivet which remains retained against the front external wall of
the riveting tool, until the casing (12) returns to its initial feeding position,
of maximum remote place with respect to the gripping mechanism (25), a moment in which,
as a passageway through the manifold (5) lateral to the casing (12) becomes free,
the rivet has access to the recess (32) impelled by compressed air.