BACKGROUND OF THE INVENTION
[0001] This invention refers to a drive apparatus having a rotatable working arm, used for
example in the motor vehicle manufacturing field for assembling parts of the bodywork;
in particular the invention refers to an apparatus for clamping work pieces, or for
positioning a work piece or a tool, for example for arc welding or for other similar
applications, by means of which it is possible to continuously adjust the opening
angle of the working arm.
[0002] Drive apparatuses of the aforementioned kind, capable of enabling the adjustment
of the opening angle of a working arm, are known for example from
US-A-6,220,588 and
WO-A 2005/044517; according to these documents, the pneumatic actuator comprises two pistons movable
with respect to each other, disposed in such a way as to vary the working stroke by
appropriately regulating their distance, in relation to the required opening angle.
[0003] In particular, in
US-A-6,220,588 a first working piston is provided, having a non-extensible rod of a preestablished
length, connected to the working arm by a toggle-lever device, in a per se known way;
the actuator comprises a second stop and brake piston whose position may be changed
to vary the stroke of the working piston, and consequently to vary the angle of rotation
upon the opening of the working arm by acting on an adjusting screw.
[0004] WO-A-2005/044517 in turn proposes a drive apparatus again comprising two jointly movable pistons connected
to the working arm by means of a non-extensible rod and a toggle-lever device; the
reciprocal distance between the two pistons may be varied also by acting on an adjusting
screw connecting the pistons. Also in this case the adjustment of the opening angle
of the working arm is obtained by simply varying the working stroke of the actuator,
by adjusting the reciprocal position of the pistons.
[0005] US-A-6,416,045 and
US-A-6,616,133, illustrate two clamping apparatuses of the aforementioned kind, in which the adjustment
of the opening angle of the working arm is carried out by steps, by adjusting the
axial length of the rod of the actuator.
[0006] According to
US-A-6,416,045, the rod comprises two coaxial rods, sliding one inside the other, in which the internal
rod is provided with a plurality of cross holes which can be aligned with corresponding
cross holes in the external rod, for the insertion of a locking pin, thereby enabling
the step-by-step adjustment of the length of the rod of the actuator, and consequently
the discontinuous variation of the angle of rotation of the working arm, a fine or
continuous adjustment being not obtainable.
[0007] US-A-6, 616, 133, in turn, suggests the use of an actuator again comprising a step-by-step extensible
rod, in which the internal rod has a plurality of circular slots, and in which use
is made of a cam device selectively engageable in the slots in the internal rod to
adjust the length of the rod step by step.
[0008] These documents also propose complex and costly solutions, with which it is only
possible to obtain a discontinuous adjustment of the length of the rod of the actuator,
and consequently of the opening angle of the working arm. Moreover, for both these
solutions it is necessary to open the apparatus to adjust the length of the rod, which
is not always possible or is complicated and time-consuming when apparatuses of this
kind are installed along a processing line.
[0009] All this results in a complexity of the system due to the need to make use of and
operate different types of apparatuses, with differentiated working strokes, to satisfy
the different operative requirements of the users.
[0010] Lastly,
EP-A-0908272 illustrates a clamping apparatus of the aforementioned kind, in which the pneumatic
actuator comprises an axially extensible rod, substantially composed of a first threaded
element rigidly connected to the rod of the piston, which engages by screwing with
a second threaded element connected to the working arm by means of a toggle-lever
device.
[0011] This document, which represents the closest prior art to this invention, in accordance
with the preamble of claim 1, again proposes a somewhat unpractical and complex solution,
in that, in order to adjust the length of the rod, it is necessary to separate the
actuator from the box-shaped body of the device, and then rotate it by the desired
degree.
[0012] An adjustment of the rod, by rotating the actuator, can be difficultly carried out
after the apparatus has been installed along a processing line; moreover, it is not
practically possible to achieve a continuous adjustment due to the need to align the
stay bolts of the actuator with the threaded holes in the box-shaped body of the toggle-lever
device which transforms the linear movement of the actuator into a rotary movement
of the working arm.
OBJECTS OF THE INVENTION
[0013] The main object of the invention is to provide a drive apparatus of the aforementioned
kind, which is structurally simple, highly reliable and which at the same time enables
the adjustment of the opening angle of the working arm within a wide range of values,
without having to open or remove the apparatus itself, once installed along a processing
line, also when operated with compressed air; conversely, the operator should manually
position the working arm in the required position.
[0014] A still further object of the invention is to provide a drive apparatus, as mentioned
previously, which is practically an universal apparatus in that it offers the possibility
of continuously adjusting the opening angle of the working arm, within a field of
values ranging for example from 0° to 135°, making use of a normal ISO cylinder, without
requiring special actuators.
[0015] A still further object is to provide a drive apparatus for the aforementioned uses,
provided with an automatic system for sensing the angular positions of the working
arm, capable of allowing the self-learning of any chosen position, for example as
described in
EP-A-1,623,795, incorporated herein for reference.
BRIEF DESCRIPTION OF THE INVENTION
[0016] These and further objects of the invention can be achieved by means of a drive apparatus
with adjustable angular opening position of a working arm, according to claim 1.
[0017] In particular, according to the invention, a drive apparatus for clamping a work
piece and/or positioning a work piece or a tool, comprising:
a box-shaped body having a longitudinal axis;
a working arm rotatably supported by the box-shaped body, to rotate between a first
angular opening position and a second angular closing position for clamping a work
piece and/or positioning a work piece or tool;
a linear pneumatic actuator secured at one end of the box-shaped body, said pneumatic
actuator comprising a single piston member reciprocable in a piston chamber, said
piston member having an axially extensible rod comprising a first threaded element
connected to the piston member, and a second threaded element having a front end hingedly
connected to a toggle-lever system operatively connected to the working arm, said
first threaded element being threadingly engageable with the second threaded element
to selectively change the axial space between the piston member and the hinged connection;
and
sensing means for detecting opening positions of the working arm,
characterised in that the first threaded element is rotatably secured to the piston
member of the actuator, the second threaded element extending into the piston chamber
with a rear end axially spaced apart from the piston member;
externally operable rod-length adjusting means being provided, said rod-length adjusting
means comprising a drive member rotatably supported at one end of the actuator, said
drive member being selectively engageable with and disengageable from the first threaded
element to rotate the same first threaded element of the piston rod;
work-arm stop means being arranged inside the box-shaped body for stopping the working
arm in the closing position; and
in that said sensing means comprise a plurality of sensors actuated by the piston
rod, said sensor being parallely arranged to the longitudinal axis inside the box-shaped
body to detect the work arm in a plurality of angularly spaced apart positions of
the same working arm.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] These and further features of the apparatus according to the invention, will be more
clearly evident from the following description with reference to the drawings, in
which:
Fig. 1 shows a longitudinal cross-sectional view of the apparatus according to the
invention;
Fig. 2 shows a cross-sectional view along the line 2-2 of Fig. 1;
Fig. 3 shows an enlarged detail of Fig. 1;
Fig. 4 shows an enlarged detail of the damping system and of the adjusting system
for adjusting the length of the piston rod.
DETAILED DESCRIPTION OF THE INVENTION
[0019] As shown in figure 1, the drive apparatus comprises a working arm 10 connected to
a shaft 11 rotatably supported by a box-shaped body 12 having a longitudinal axis;
the apparatus also comprises a toggle-lever drive device or system 13 inside the box
shaped body 12 and a linear pneumatic actuator 14, operatively connected to the working
arm 10 by means of the same toggle-lever device 13 to transform the linear movement
of the piston of the actuator 14, into a rotating movement of the working arm 10 between
a first suitably adjustable opening position A and a second closing position B in
which the working arm B positions a work piece, or a tool, not shown, against a work
piece, or clamps the latter against a supporting surface, along a processing line.
[0020] The toggle-lever device 13 comprises a crank 15, connected to the work-arm shaft
11, and an intermediate connecting link 16, which in turn is hingedly connected to
a rod 18 of the actuator 14 by a hinge pin 17' provided between the same link 16 and
a connecting element 17 arranged at a front end of the rod 18.
[0021] The reference number 19 in figure 1 has been used to indicate one of the two guide
rollers coaxially arranged onto the hinge pin 17' between the connecting link 16 and
the connecting element 17; the roller 19 is movable along a raceway parallel to the
rod of the actuator 14, the raceway extending with a cam 20 having a linear, or appropriately
arched, profile to provide the reaction necessary to generate the force for closing
the arm 10 in the position B.
[0022] Lastly, in Fig. 1 the reference number 21 has been used to indicate a work-arm stop
element for stopping the crank 15, defining the exact closing position B of the working
arm 10. The reference number 22 has been used to indicate an elastic pad secured to
a second stop element 23 axially aligned with the actuator 14, whose absence or presence
makes the system reversible or irreversible, under the action of external forces,
according to need.
[0023] The linear pneumatic actuator 14 is of the double-acting type; it comprises a cylinder
24 having an oval-shaped chamber 25, in which reciprocates a single piston member
26; compressed air can be fed and, respectively, discharged on the two sides of the
chamber 25 of the cylinder 24, through inlet/discharge apertures 27, 28 made in the
two heads 29 and 30 which close the cylinder 24 at the two ends.
[0024] As mentioned previously, the pneumatic actuator 14 comprises a rod 18 which extends
axially into the box-shaped body 12 for an operative connection with the toggle-lever
drive device 13.
[0025] According to this invention, in order to allow a continuous variation and adjustment
of the angular opening position A of the working arm 10 within a wide range of values,
ranging for example from 0° to 135°, by means of a simple, highly reliable and fail-safe
solution, in combination with a linear pneumatic actuator of the conventional type,
use has been made of a rod 18 made in such a way as to be axially extensible simply
by screwing, so as to allow it to be adjusted in length acting from the outside without
having to open or remove the actuator.
[0026] According to the example of Fig. 1, the rod 18 comprises a first threaded element
18A which threadingly engages with a second threaded element 18B in order to selectively
change the axial space between the piston 26 and the hinge pin 17'; both the elements
18A and 18B are provided with a screw thread having a pitch capable of allowing a
fine adjustment of the axial length of the rod 18, and an irreversible coupling between
the screw threads under the action of axial thrusts of the piston 26 and of external
forces.
[0027] In particular, the first threaded element 18A is secured to the piston 26 in such
a way as to be able to rotate around its own longitudinal axis, by acting from the
outside of the actuator, as explained further on with reference to Fig. 4.
[0028] The second threaded element 18B, as previously mentioned, has a front end hingedly
connected to the toggle-lever system 13; furthermore, the same element 18B tightly
extends from the box-shaped body 12 into the piston chamber 25 with a rear end axially
spaced apart from the piston 26.
[0029] In the example shown, the first threaded element 18A and the second threaded element
18B are threadingly engaged with each others, since the threaded element 18A is screwed
into an internally threaded hole in the second threaded element 18B.
[0030] As shown in Fig. 1 and in the enlarged detail of Fig. 3, in order to prevent any
accidental rotations of the threaded element 18A, with respect to the threaded element
18B, caused for example by vibrations to which the entire apparatus may be subjected
during operation, use has been made of a suitable friction means, for example consisting
of a cylindrical plug 31, made of plastic material or other suitable material, housed
in a cross hole 32 near to the front end of the threaded element 18A; the plug 31
has an axial length slightly greater than the diameter of the internal threaded element
18A so as to frictionally interfere with the screw thread of the threaded element
18B.
[0031] As previously mentioned, the invention is directed to a drive apparatus comprising
a toggle-lever device and a linear pneumatic actuator provided with means capable
of allowing the continuous adjustment of the opening angle of the working arm 10,
within a wide range of values, for positioning and/or clamping work pieces, for welding
operations and/or for other applications in the motor vehicle manufacturing field,
or in other fields.
[0032] Consequently, according to a further feature of the invention, the apparatus is provided
with sensing means 33 capable of continuously detecting, both the closed angular position
of the working arm 10, indicated by reference B in Fig. 1, and all the angularly spaced-apart
opening positions possible for the working arm 10, one of which has been indicated
by reference A.
[0033] In the case shown, the sensing means for detecting the angular positions of the working
arm 10 comprise, for example, a plurality of optical sensors 33' or of any other type,
disposed side by side inside the box-shaped body 12, parallely to the longitudinal
axis of the same body 12; the sensors 33' are selectively activated or actuated by
a lug 34 laterally secured to the part 18B of the piston rod 18.
[0034] The sensors 33' are secured and connected to an electronic circuit card 35 programmed
to allow a self-learning of the desired angular opening position, when the working
arm 10 remains stationary for a few instants, as described in
EP-A-1,623,795, introduced herein for reference.
[0035] The apparatus also comprises means for adjusting the opening angle of rotation of
the working arm 10, which can be operated from the outside; according to the invention,
the adjustment of the opening angle is obtained by simply screwing, to change and
adjust the length of the rod 18 of the piston, in relation to the desired opening
position of the working arm 10.
[0036] The means for adjusting the opening angle comprise a drive member 36 which can be
manually operated to rotate the threaded element 18A by acting from the bottom of
the actuator, with respect to the piston 26 and the threaded element 18B; the threaded
element 18A can be screwed or unscrewed to change the axial extension of the entire
rod 18. In this connection, the drive member 36 comprises a piston 36' rotatably supported
in a hole 37 of the head 30 at the bottom end of the actuator 14; a shank 38 of the
piston 36' ends with a hexagonal head 39 selectively engageable with and disengageable
from a hexagonal hole 40 made in a rear-end extension 41 of the rod element 18A, onto
which is secured a bush 42.
[0037] The hole 37 is of such dimensions as to allow the rotation and brief axial displacement
of the drive member 36, so as to engage the hexagonal head 39 in the hexagonal hole
40; in this way the rod 18 of the actuator 14 can be lengthened and shortened, and
its length finely and continuously adjusted, to make the working arm 10 rotate to
the desired opening position.
[0038] Therefore, whenever it is required to adjust the opening position of the arm 10,
an operator simply inserts a key into the hexagonal hole 36A of the piston 36', through
a hole in the head 30, then pushes the piston 36' upwards to engage the hexagonal
head 39 in the hole 40; subsequently, by means of the same key he rotates the piston
36' and consequently the threaded element 18A to adjust the length of the rod 18,
changing the distance between the piston 26 and the hinge pin 17'. The box-shaped
body 12, in correspondence with the axis 11 of rotation of the working arm 10, is
provided with a graduated indication of the opening angle set by adjusting the length
of the rod 18 of the actuator.
[0039] When the compressed air is fed into the actuator 14 through the aperture 28, the
same air, through suitable passages, is automatically fed into the hole 37 causing
the drive member 36, to shift backwards and disengaging it from the rod 18.
[0040] Lastly, the apparatus further comprises a pneumatic damping and braking device for
the piston 26, as illustrated hereunder with reference to Fig. 4; the pneumatic damping
and braking device are provided for damping and braking the piston 26 on the final
portion of its return stroke, during the opening movement of the working arm 10.
[0041] In particular, the damping device comprises the bush 42 integral with the piston
26; the bush 42 has a slightly conical outer surface, of a diameter smaller than the
internal diameter of an axial extension of the hole 37, to form an annular chamber
43 in communication with the compressed air inlet/discharge aperture 28. During the
last portion of the return stroke of the piston 26, the bush 42 passes through an
annular airtight seal 44 capable of performing a brief axial movement; in this way
the compressed air that remains between the piston 26 and the head 30 is forced out
along the branched off path or duct 45, comprising an adjustable throttling valve
46. The path 45 is branched off between the chamber 25 of the cylinder 24 and the
annular chamber 43 of the damper. It should be pointed out that the seal 44 is able
to shift slightly in an axial direction against a stop washer 47 to allow a passage
of compressed air at the beginning of the working stroke, until the bush 42 has slipped
off completely.
[0042] From what has been described and shown, it will be clear that a drive apparatus is
provided for operating a working arm, by means of which it is possible to substantially
continuously vary and adjust the angular opening position of the arm itself, within
a wide range of values, by means of a mechanically simple, extremely reliable solution,
capable of enabling the reduction of the overall dimensions of the apparatus itself.
[0043] Lastly, Fig. 1 shows a second possible solution of the means for stopping the arm
10 in the working position B, in place of or in combination with the stopping means
21; in fact, it is possible to provide a stop member 48, at the lower end of the rod
element 18B, or otherwise secured, which penetrates completely into a seat 49 in the
front head 29. In both cases the stroke of the piston 26 and the length of the cylinder
24 remain substantially unchanged and are not critical in that the arm 10 stops in
the working position B anyway, regardless of the length of the rod 18.
[0044] Other modifications or variations may be made, to the toggle-lever drive device,
the pneumatic actuator and/or the device for adjusting the length of the rod 18 and/or
to the pneumatic damping device, without thereby deviating from the scope of the invention,
as defined by the claims.
1. A drive apparatus for clamping a work piece and/or positioning a work piece or a tool,
comprising:
a box-shaped body (12) having a longitudinal axis;
a working arm (10) rotatably supported by the box-shaped body (12), to rotate between
a first angular opening position (A) and a second angular closing position (B) for
clamping a work piece and/or positioning a work piece or tool;
a linear pneumatic actuator (14) secured at one end of the box-shaped body (12), said
pneumatic actuator (14) comprising a single piston member (26) reciprocable in a piston
chamber (25), said piston member (26) having an axially extensible rod (18) comprising
a first threaded element (18A) connected to the piston member (26), and a second threaded
element (18B) having a front end hingedly connected to a toggle-lever system (13)
operatively connected to the working arm (10), said first threaded element (18A) being
threadingly engageable with the second threaded element (18B) to selectively change
the axial space between the piston member (26) and the hinged connection (17'); and
sensing means (33) for detecting opening positions of the working arm (10),
characterised in that the first threaded element (18A) is rotatably secured to the piston member (26) of
the actuator (14), the second threaded element (18B) extending into the piston chamber
(25) with a rear end axially spaced apart from the piston member (26);
externally operable rod-length adjusting means (36) being provided, said rod-length
adjusting means comprising a drive member (36) rotatably supported at one end of the
actuator (14), said drive member (36) being selectively engageable with and disengageable
from the first threaded element (18A) to rotate the same first threaded element (18A)
of the piston rod (18);
work-arm stop means (21; 48) being arranged inside the box-shaped body (12) for stopping
the working arm (10) in the closing position (B); and
in that said sensing means (33) comprise a plurality of sensors (33') actuated by the piston
rod (18), said sensor (33') being parallely arranged to the longitudinal axis inside
the box-shaped body (12) to detect the work arm (10) in a plurality of angularly spaced
apart positions of the same working arm (10).
2. The apparatus according to claim 1, characterised in that the first threaded element (18A) engages in an internally threaded hole in the second
element (18B) of the rod (18) of the piston (26).
3. The apparatus according to claim 1, characterised in that the stop means (21) are disposed inside the box-shaped body (12) enclosing the toggle-lever
system (13) which connects the piston rod (18) to the working arm (10).
4. The apparatus according to claim 1, characterised in that the stop means (48) are secured to the piston rod (18), and in that a closing head (29) of the actuator (14) comprises a seat (49) for housing the stop
means (48), in the closed position (B) of the working arm (10).
5. The apparatus according to claim 1, characterised in that said drive member (36) comprises a second piston (36') rotatably fitted and axially
sliding in a hole (37) in a head (30) of the actuator (14), said piston (36') having
a shank (38) shaped to removably engage with a hole (39) in the piston rod (18) of
the actuator (14).
6. The apparatus according to claim 5, characterised in that the hole (37) for housing the drive member (36), is connected with an inlet/discharge
aperture (28) for compressed air for the actuator (14).
7. The apparatus according to claim 1, characterised in that the drive member (36) is manually operatable from the outside of the linear actuator
(14).
8. The apparatus according to claim 1, characterised by comprising pneumatic damping means (42, 44, 45, 46) for braking the movement of the
piston (26) of the actuator (14) in the final portion of the return stroke towards
the open position (A) of the working arm (10).
9. The apparatus according to claim 8, characterised in that said pneumatic damping means (42, 44, 45, 46) comprise a branched off duct (45),
between the chamber (25) of the actuator (14) and an air inlet/outlet aperture (28),
said branched off duct (45) comprising a throttle valve (46).
10. The apparatus according to claim 1, characterised in that said plurality of sensors (33') are connected to an electronic circuit (35) programmed
for self-learning the opening position (A) of the working arm (10).