EP3342540B1

EP3342540B1 - Autofeed automatic screwdriver

Info

Publication number: EP3342540B1
Application number: EP17210698.1A
Authority: EP
Inventors: Luca CORRADINA; Marco Valle; Claudio CORADAZZI
Original assignee: Marelli Automotive Lighting Italy SpA
Current assignee: Marelli Automotive Lighting Italy SpA
Priority date: 2016-12-27
Filing date: 2017-12-27
Publication date: 2020-11-18
Anticipated expiration: 2037-12-27
Also published as: EP3342540A1; IT201600131235A1; PL3342540T3; ES2834029T3

Description

This application claims priority from Italian Patent Application No. 10216000131235 filed on December 27, 2016 .
The present invention relates to an autofeed automatic screwdriver.
More in detail, the present invention relates to the bit-holding rod of an electrically- or pneumatically-operated autofeed automatic screwdriver, to which the following disclosure will make explicit reference without however losing in generality.
As it is known, autofeed automatic screwdrivers are electrically- or pneumatically-operated devices that receive at input a succession of screws, usually of the self-tapping type, and are adapted to screw the screws into a generic support in a completely automatic manner.
Autofeed automatic screwdrivers usually comprise: a bit-holding head that houses inside itself the screw bit, receives at input the screws to be screwed, and is adapted to place in succession each screw in front of the screw bit, locally coaxial to the same screw bit; and an electric or pneumatic servo-motor that is able to drive into rotation the screw bit around its longitudinal axis and, optionally, also to axially move the screw bit back and forth inside the bit-holding head, so as to cyclically bring the screw bit in abutment against the head of the screw and then push the screw against the support stationary beneath the bit-holding head.
More in detail, the bit-holding head is usually provided with an outer rigid casing which is oblong in shape and is provided with a straight main duct from which the single screws come out in succession and which houses the screw bit in axially slidable and rotatable manner, and with a straight secondary duct that branches off from the straight main duct with an inclination angle of about 45° and is dimensioned so as to convey the screws to be screwed in succession in the straight main duct, immediately beneath the screw bit.
The bit-holding head additionally also comprises: a bit-holding rod that extends coaxial to the longitudinal axis of the straight main duct, is inserted in axially slidable and rotatable manner inside the outer casing so as to partially project into the upper portion of the main straight duct where the screw bit is located, and finally carries firmly fixed at its lower end the screw bit; a contrast spring which is adapted to elastically counteract the descent of the bit-holding rod and of the screw bit along the main straight duct towards the bottom mouth of the duct; and a screw-stop device which is arranged along the lower portion of the straight main duct, immediately downstream of the joining/connecting point with the straight secondary duct, and is adapted to stop each screw descending along the straight main duct towards the bottom opening, until the moment when the screw bit reaches and the engages the head of the screw.
The electric or pneumatic servo-motor is adapted to rotate the bit-holding rod around its longitudinal axis and usually also to axially move the bit-holding rod with respect to the outer casing, so as to cyclically move the screw bit back and forth inside the straight main duct.
US patent US4294142 discloses an autofeed automatic screwdriver of the type described above.
Unfortunately, the automatic screwdrivers described above tend to jam with a particularly high frequency when they are used to screw self-tapping screws with a small-sized stem, such as the ones that are typically used to fix the boards of electronic printed circuit boards.
Problem that leads to a significant decrease in the productivity of the assembly line that installs the boards on the relative supports.
More in detail, experimental tests have revealed that this particular type of self-tapping screws often does not arrange itself at the screw-stop device, perfectly coaxial to the longitudinal axis of the screw bit. Incorrect position that the self-tapping screw usually keeps even when it is pushed by the screw bit along the main straight duct, up to the bottom mouth of the duct.
As a consequence, when it reaches the board stationary beneath the straight main duct, the self-tapping screw tends to get stuck in the terminal board and then to bend and/or break due to the thrust of the screw bit, with all the problems that this entails. When breaks, in fact, the screw tends to obstruct the mouth of the straight main duct, thus preventing other screws from coming Documents EP 0 131 851 A1 and US 2011/089218 A1 also disclose automatic screwdrivers according to the state of the art.
Aim of the present invention is to provide an electrically- or pneumatically-operated autofeed automatic screwdriver that does not jam in presence of self-tapping screws with a small-sized stem.
In compliance with the above aims, according to the present invention there is provided an autofeed automatic screwdriver as defined in Claim 1 and preferably, though not necessarily, according to any one of the claims depending on it.
Furthermore, according to the present invention there is provided an operating method of an autofeed automatic screwdriver as defined in Claim 16.
The invention will now be described with reference to the accompanying drawings, which show a non-limiting embodiment thereof, wherein:

Figure 1 is a perspective view of an autofeed automatic screwdriver realized according to the teachings of the present invention;
Figure 2 is a side view of the bottom part of the automatic screwdriver shown in Figure 1, sectioned along the midplane and with parts removed for clarity;
Figure 3 is a sectional view of the lower axial end of the bit-holding rod shown in Figure 2, with parts removed for clarity;
Figure 4 is an exploded perspective view of the bit-holding rod shown in Figures 2 and 3, with parts removed for clarity; whereas
Figures 5, 6, 7 and 8 depicts the operation of the automatic screwdriver subject of the preceding figures.

With reference to figures 1, 2, 3 and 4, number 1 denotes as a whole an autofeed automatic screwdriver which is adapted to screw, into a generic support and in automatic manner, a succession of screws 100 preferably made of metal material and preferably of the self-tapping type.
More in detail, the automatic screwdriver 1 can be advantageously used to screw a succession of screws with a small-sized stem, preferably made of metal material and preferably of the self-tapping type, into a generic board for electronic printed circuit boards or other support.
In other words, the automatic screwdriver 1 is adapted to receive at input a succession of screws, preferably made of metal material and preferably of the self-tapping type, and to screw the single screws in sequence and in automatic manner into a generic board for electronic printed circuit boards or other support.
The automatic screwdriver 1 comprises: a bit-holding head 2 which houses inside itself a rotatable screw bit 3 of know type and is adapted to receive at input a succession of screws 100 that it arranges in sequence in front of the screw bit 3, locally substantially coaxial to the same screw bit 3; and a motor assembly 4, preferably of the electric or pneumatic type, which is preferably rigidly fixed/connected to the bit-holding head 2 via a straight sleeve 5 and is adapted to drive into rotation the screw bit 3 around its longitudinal axis and, optionally, also to axially move the screw bit 3 inside the bit-holding head 2, so as to bring the screw bit 3 in abutment against the head of the 100 and then push the screw 100 out of the bit-holding head 2, against the board or other support stationary beneath the bit-holding head 2.
With reference to Figures 1 and 2, the bit-holding head 2 firstly comprises a preferably substantially V-shaped or Y-shaped, outer casing 6 which is preferably made of metal material and is internally provided with a substantially straight main duct 7 preferably having a circular cross section, which is open at one end 7a and is dimensioned so as to accommodate the screw bit 3 with its shaped tip 3a turned towards the open end 7a of the same duct; and with a substantially straight secondary duct 8 preferably having a circular cross section, that branches off obliquely from the main duct 7.
The main duct 7 is dimensioned so as to be engaged in axially rotatable and axially slidable manner by the screw bit 3 and by the single screws 100 to be screwed, substantially up to the open end 7a. The secondary duct 8, on the other hand, is dimensioned for conveying a succession of screws to the main duct 7, immediately beneath the screw bit 3.
More in detail, the longitudinal axis B of secondary duct 8 is inclined with respect to the longitudinal axis A of main duct 7 by and angle α lower than 75° and preferably, though not necessarily, ranging between 35° and 45°.
Preferably, longitudinal axes A and B moreover lie on the midplane of outer casing 6.
With particular reference to Figure 2, the secondary duct 8 thus divides the main duct 7 into an upper portion and a lower portion, both substantially straight and coaxial to one another.
The upper portion of main duct 7 houses the screw bit 3 with the shaped tip 3a turned towards the joining/ connecting point with the secondary duct 8. The lower portion of main duct 7, on the other hand, ends at the open end 7a of main duct 7 and is adapted to be engaged in axially slidable and rotatable manner by the screw bit 3 and by the single screws 100 to be screwed.
In other words, the screw bit 3 is housed inside the portion of the main duct 7 located above the joining/ connecting point with the secondary duct 8, and is capable of axially moving inside the main duct 7 from and to the open end 7a, going beyond the joining/connecting point with the secondary duct 8.
In the example shown, in particular, the outer casing 6 is preferably substantially Y-shaped and preferably comprises: a central block 10 preferably with a monolithic structure, which is substantially V-shaped, with an inclination angle of the two straight branches preferably lower than 75° and preferably ranging between 35° and 45°; and a straight tubular segment 11 preferably with a circular cross section, which projects from the central block 10 starting from the bottom vertex of the V, while remaining substantially coaxial to a first straight branch of the central block 10.
The axial cavity of straight tubular segment 11 is dimensioned to be engaged in axially slidable and axially rotatable manner by the screw bit 3 and by the screws 100 to be screwed; whereas the central block 10 is provided with a circular cross section, first straight hole that extends in pass-through manner inside the first straight branch of central block 10, while remaining coaxial to the longitudinal axis of the straight tubular segment 11, and is dimensioned to form an extension of the axial cavity of the straight tubular segment 11.
The central hole 10 is moreover provided with a circular cross section, second straight hole that branches off obliquely from the first straight hole, extends in pass-through manner inside the second straight branch of central block 10 and is dimensioned to be engaged in axially slidable manner by the screws 100 to be screwed.
The axial cavity of straight tubular segment 11 and the first straight hole of central block 10 form the main duct 7. The longitudinal axis of straight tubular segment 11, therefore, coincides with the longitudinal axis A of main duct 7.
The second through hole of the central block 10, on the other hand, forms the secondary duct 8.
In other words, the upper portion of main duct 7 and the entire secondary duct 8 are preferably entirely contained in the central block 10.
In addition, the joining/connecting point between the secondary duct 8 and the main duct 7 is preferably located inside the central block 10, immediately above the junction with the straight tubular segment 11.
Preferably, the outer casing 6 furthermore includes a second straight tubular segment 12 preferably with a circular cross section, which projects from the central block 10 on the opposite side with respect to the straight tubular segment 11, while remaining substantially coaxial to the longitudinal axis A of main duct 7, so as to form an extension of main duct 7.
In other words, the straight tubular segment 12 projects from the distal end of the first straight branch of central block 10, while remaining locally coaxial to the first straight hole of central block 10 and to the straight tubular segment 11.
Preferably, the central block 10, the straight tubular segment 11 and/or the straight tubular segment 12 is/are made of metal material.
With reference to Figures 2, 3 and 4, in addition the bit-holding head 2 also comprises a straight bit-holding rod 14 preferably made of a metal material, which extends substantially coaxial to the longitudinal axis A of main duct 7 and is inserted in the outer casing 6 in axially slidable and rotatable manner, so as to partially project into the upper portion of the main duct 7.
The bit-holding rod 14, in addition, is rigidly integral to the screw bit 3 and is mechanically connected to the motor assembly 4, so as to be driven into rotation around its longitudinal axis, i.e. around the longitudinal axis A of main duct 7.
More in detail, the bit-holding rod 14 partially projects into the upper portion of main duct 7 while remaining locally coaxial to the screw bit 3, and is firmly fixed to the rear shank 3b of the screw bit 3 preferably in a rigid and stable, though manually removable manner.
Preferably the upper end of the bit-holding rod 14, on the other hand, is provided with a coupling shank (not shown in the figures) which is specifically structured to rigidly couple with the motor assembly 4.
Preferably the motor assembly 4 is furthermore adapted to move axially the bit-holding rod 14 inside the outer casing 6, so as to be able to move the screw bit 3 along the main duct 7, towards the open end 7a.
With reference to Figures 3 and 4, the bit-holing rod 14 in particular comprises: a straight stem 15 preferably made of metal material, which has an axial end 15a firmly connected to the screw bit 3; and a hollow movable piston 16 preferably made of metal material and preferably substantially cylindrical in shape, which is inserted in axially slidable manner into the main duct 7 and is furthermore engaged in pass-through and axially slidable manner jointly by the straight stem 15 and by the screw bit 3 integral thereto, so as to freely move back and forth astride the straight stem 15 and the screw bit 3.
More in detail, the straight stem 15 extends coaxial to the longitudinal axis A of main duct 7 while protruding into the main duct 7, and has the axial end 15a located inside of main duct 7 firmly connected to the rear shank 3b of screw bit 3.
Preferably the screw bit 3, or rather the rear shank 3b of screw bit 3, is furthermore fixed to the axial end 15a of straight stem 15 in easily detachable manner.
The movable piston 16, on the other hand, has a cross section preferably substantially complementary to the one of main duct 7, so as to engage in axially slidable manner the main duct 7, and is furthermore provided with a pass-through central hole 16a having a cross section preferably substantially complementary to the one of straight stem 15 and of screw bit 3, so as to be engaged in axially slidable manner by the straight stem 15 and by the screw bit 3.
In addition, the movable piston 16 also has, on its front face, i.e. on the face of the piston turned towards the shaped tip 3a of screw bit 3, a central concave recess or seat 16b which has a shape substantially complementary to the one of the head of the screws 100 that enter in succession into the main duct 7, and is able to accommodate the head of the screw 100 to be screwed stationary or anyway present inside the main duct 7, while arranging at same time the same screw 100 locally substantially coaxial to the longitudinal axis of the screw bit 3, i.e. coaxial to the longitudinal axis A of main duct 7.
More in detail, the concave recess or seat 16b is preferably substantially coaxial to the pass-through central hole 16a of movable piston 16 and directly communicates with the pass-through central hole 16a.
Preferably, the concave recess or seat 16b is furthermore realized on a removable portion of the movable piston 16, so as to be easily replaceable.
With reference to Figures 3 and 4, furthermore the bit-holding rod 14 additionally comprises a contrast spring 17 that is preferably arranged inside the movable piston 16 and is adapted to axially push and elastically hold the movable piston 16 in a covering position in which the movable piston 16 is located at the shaped tip 3a of screw bit 3 and internally accommodates/contains the shaped tip 3a, upstream of the concave recess or seat 16b.
More in detail, when the movable piston 16 is in the covering position, the shaped tip 3a of screw bit 3 is entirely housed inside the pass-through central hole 16a upstream of the concave recess or seat 16b.
In other words, the contrast spring 17 is adapted to elastically counteract any axial movement of the movable piston 16 away from a covering position in which the movable piston 16 is located at the shaped tip 3a of screw bit 3 and the shaped tip 3a is retracted inside the body of moveable piston 16, beyond the bottom of the concave recess or seat 16b, so as not to project from the bottom of concave recess or seat 16b.
Preferably, the bit-holding rod 14 is furthermore provided with a stop member 18 which is preferably arranged on the straight stem 15 or on the screw bit 3, and is adapted to prevent the movable piston 16 from moving beyond the covering position and from completely slipping off the straight stem 15 and the screw bit 3.
The contrast spring 17 is therefore adapted to elastically keep the movable piston 16 in abutment against the stop member 18, in the covering position.
With reference to Figures 2, 3 and 4, in the example shown, in particular, the bottom axial end 15a of the straight stem 15 is preferably provided with an axial dead hole, where the rear shank 3b of screw bit 3 is screwed in or otherwise fixed in manually removable manner.
Preferably the axial top end of the straight stem 15 (not shown in the figures), on the other hand, is provided with a coupling shank, which is specifically structured to rigidly couple with the motor assembly 4.
The movable piston 16, in turn, preferably consists of a cup-shaped body 20 and of a bushing 21 firmly fixed to one another, preferably in manually detachable manner.
The cup-shaped body 20 is preferably substantially ogival cylindrical in shape, is provided with a pass-through central hole, and is fitted in axially slidable manner on the straight stem 15 with the concavity facing the screw bit 3 fixed to the axial end 15a of the same stem. The bushing 21, on the other hand, is substantially tubular cylindrical in shape, is fitted in axially slidable manner on the screw bit 3, and is finally screwed in or otherwise fixed in manually removable manner to the mouth of the cup-shaped body 20.
The concave recess or seat 16b of movable piston 16 is preferably formed on the front or outer face of bushing 21, i.e. on the face of bushing 21 arranged opposite to the cup-shaped body 20.
With particular reference to Figures 3 and 4, on the other hand, the contrast spring 17 preferably consists of a helical spring which is fitted on the screw bit 3 fixed to the axial end 15a of straight stem 15, inside the cup-shaped body 20, so as to have a first axial end in abutment against the rear face of bushing 21 and a second axial end in abutment against a washer 22 or other stop member which is trapped between the axial end 15a of the straight stem 15 and the collar connecting the central trunk/stalk of the screw bit 3 to the rear shank 3b.
Preferably, the washing 22 or other stop member is furthermore dimensioned to protrude radially and arrive in abutment against the inner cavity of the movable piston 16, so as to limit the axial stroke of the movable piston 16 and prevent the contrast spring 17 from pushing the movable piston 16 beyond the screw bit 3, thus completely removing it from the straight stem 15.
More in detail, the washing 22 or other stop member is preferably arranged so that a limit of the axial stroke of the movable piston 16 coincides with the covering position.
In other words, the stop member 18 preferably coincides with the washing 22 or other stop member against which the second end of the helical spring 17 abuts.
Alternatively, the second end of the helical spring could be arranged in abutment against an annular shoulder formed on the straight stem 15 or on the screw bit 3.
Obviously, also the annular shoulder could be dimensioned to radially project and abut against the inner cavity of movable piston 16, so as to limit the axial stroke of the movable piston 16 and act as a stop member 18 for the movable piston 16.
The cup-shaped body 20, the bushing 21, the washing 22 and the helical spring 17 are preferably made of metal material.
With reference to Figures 1 and 2, additionally the bit-hold head 2 also comprises: a second contrast spring 25 which is preferably interposed between the outer casing 6 and the bit-holding rod 14 and is adapted to elastically counteract the advancing/descent of the bit-holding rod 14 along the main duct 7, towards the open end 7a; and preferably also a screw-stop device 26 which is arranged along the lower portion of main duct 7, preferably immediately downstream of the joining/connecting point with the secondary duct 8, and is adapted to stop each screw 100 descending along the main duct 7 towards the open end 7a, preferably until the moment when the screw bit 3 reaches and engages the head of the screw 100.
More in detail, the contrast spring 25 is adapted to elastically hold the ensemble of the screw bit 3 and of the bit-holding rod 14 above the joining/connecting point between the main duct 7 and the secondary duct 8.
The motor assembly 4 is thus adapted to axially move the bit-holding rod 14 and the screw bit 3 inside the main duct 7 of bit-holding head 2 overcoming the resistance of the contrast spring 25, so as to bring the ensemble of screw bit 3 and of bit-holding rod 14 in abutment against the head of the screw 100 stationary at the screw-stop device 26 and then push the screw 100 along the lower portion of main duct 7, towards the open end 7a of main duct 7.
With reference to Figure 2, in the example shown, in particular, the screw bit 3 is preferably located inside the central block 10 with the shaped tip 3a facing the straight tubular segment 11; whereas the bit-holding rod 14, or rather the straight stem 15, projects from the central block 10 and extends inside the straight tubular segment 12, preferably for the whole length of the sleeve, so as to also project from the distal end of the straight tubular segment 12.
In addition the bit-holding rod 14, or rather the straight stem 15, is preferably dimensioned to also project into the straight sleeve 5, up to reach and stably couple with the motor assembly 4.
Preferably the contrast spring 25, on the other hand, is fitted onto the bit-holding rod 14, or rather onto the straight stem 15, so as to have a first end in abutment against the central block 10, inside the straight tubular segment 12, and a second end in abutment against a cup, disk or other stop organ (not shown in the figures), which is firmly fixed on the bit-holding rod 14, or rather on the straight stem 15, preferably close to the top end of the same bit-holding rod 14.
More in detail, in the example shown the contrast spring 25 preferably consists of a helical spring preferably made of metal material.
With reference to Figures 1, 2, 5, 6, 7 and 8, the screw-stop device 26, on the other hand, is adapted to stop each single screw 100 descending along the lower portion of the main duct 7, while arranging the screw 100 with the tip facing the open end 7a of main duct 7 and with the head facing the screw bit 3, and is preferably also adapted to elastically counteract any further movement of the screw 100 inside the main duct 7 towards the open end 7a.
In the example show, in particular, the screw-stop device 26 is preferably located on the straight tubular segment 11, close to the junction with central block 10.
Preferably the screw-stop device 26 moreover comprises: at least one and preferably a plurality of radially movable latches 27 that lie on a same reference plane substantially perpendicular to the longitudinal axis A of straight tubular segment 11, are arranged inside the axial cavity of straight tubular segment 11 spaced apart around the longitudinal axis A of the sleeve, and are finally inserted in axially slidable manner inside a series of radial seats realized in the lateral wall of straight tubular segment 11; and an elastic member 28 which is adapted to elastically keep the crown of latches 27 in a locking position (see Figure 2, 5, 6), in which all latches 27 slightly protrude into the straight tubular segment 11 so as to prevent the passage of the head of the screw 100.
More in detail, the latches 27 are preferably at least three in number (four in the example shown) and are preferably angularly equally spaced around the longitudinal axis A of the straight tubular segment 11. Preferably the latches 27 furthermore are spherical in shape, and are preferably finally inserted in axially slidable manner into a series of radial through holes realized in the lateral wall of straight tubular segment 11, equally angularly spaced around the longitudinal axis A of the segment.
Preferably, the movable latches 27 furthermore have a diameter such as to protrude out of the lateral wall of the straight tubular segment 11, on opposite sides of the same wall.
On the other hand, the elastic member 28 preferably consists of an elastic annular body preferably made of elastomeric material, which is fitted on the straight tubular segment 11 substantially coplanar to the crown of latches 27, so as to surround the crown of latches 27 and be able to elastically push all latches 27 towards the centre of the straight tubular segment 11.
More in detail, in the example shown, the screw-stop device 26 preferably comprises two crowns of movable latches 27 arranged along the straight tubular segment 11, one above the other; and two elastic members 28 each adapted to elastically keep a respective crown of movable latches 27 in the locking position.
With reference to Figures 1, 2, 5, 6, 7 and 8, finally the bit-holding head 2 is preferably also provided with a deflector assembly 30 which is located substantially at the joining/connecting point between the main duct 7 and the secondary duct 8, and is adapted to selectively channel the screws 100 coming out of the secondary duct 8 towards the lower portion of the main duct 7, with the tip turned towards the open end 7a of the same main duct 7.
The deflector assembly 30 preferably comprises: a movable shutter 31 preferably with a plate-like structure, which is inserted in slidable manner into the outer casing 6, or rather into the central bock 10, so as to move in a guillotine-like manner on a sliding plane P oblique/ inclined with respect to the longitudinal axis A of main duct 7, between a first operating position (see Figure 5) in which the movable shutter 31 obliquely intersects the main duct 7 at the joining/connecting point with the secondary duct 8, and a second operating position (see Figures 2, 6 and 7) in which the movable shutter 31 does not protrude into the main duct 7; and a preferably electrically- or pneumatically- operated, moving device 32 which preferably is firmly fixed on the outer casing 6, or rather on the central block 10, beside the movable shutter 31 and is adapted to move the movable shutter 31 with respect to the outer casing 6 so as to alternatively place the movable shutter 31 in the first or in the second operating position.
More in detail, when arranged in the first operating position (see Figure 5), the movable shutter 31 is adapted to form an extension of the upper wall of secondary duct 8 that obliquely and preferably entirely crosses the main duct 7, and is capable of deflecting/directing the screws 100 coming out of the second secondary 8 towards the lower portion of main duct 7.
In other words, when arranged in the first operating position (see figure 5), the movable shutter 31 is adapted to form an extension of the top wall of the secondary duct 8 which entirely crosses the main duct 7 up to reach and preferably also engage the area of the lateral wall of the main duct 7 that is located on the opposite side of the mouth of secondary duct 8.
The moving device 32, on the other hand, is preferably adapted to automatically move the movable shutter 31 from the first to the second operating position (see Figures 2, 6 and 7) when the screw bit 3 starts its descent along the main duct 7, so as to allow the screw bit 3 to freely descend in the lower portion of main duct 7; and to automatically move the movable shutter 31 from the second to the first operating position (see Figure 5), when the screw bit 3 returns inside the upper portion of main duct 7.
Preferably the moving device 32 is furthermore an electrically- or pneumatically- operated linear actuator adapted to move the movable shutter 31 back and forth in the outer casing 6.
In addition, the movable shutter 31 is preferably inserted in the outer casing 6 so as to slide on the oblique sliding plane P in a given direction d which is substantially coplanar to the longitudinal axes A and B of main duct 7 and of secondary duct 8.
With reference to Figures 2 and 5, in particular, the sliding plane P of movable shutter 31 is preferably substantially orthogonal to the midplane of outer casing 6, i.e. to the lying plane of main duct 7 and of secondary duct 8, and is furthermore inclined with respect to the longitudinal axis A of main duct 7 by an angle β preferably lower than 75° and preferably, though not necessarily, ranging between 35° and 45°.
Preferably the inclination angle β of the sliding plane P of movable shutter 31 with respect to the longitudinal axis A of main duct 7 is moreover smaller than or equal to the inclination angle α of the longitudinal axis B of secondary duct 8 with respect to the longitudinal axis A of main duct 7.
Therefore, with reference to Figure 5, when it is in the first operating position, the movable shutter 31 forms an extension of the upper wall of secondary duct 8 that is preferably inclined by some degrees with respect to the longitudinal axis B of secondary duct 8, so as to more effectively deflect the screws 100 coming out of the secondary duct 8 towards the lower portion of main duct 7.
With reference to Figures 1, 2, 5, 6 and 7, in the example shown, in particular, the movable shutter 31 preferably consists of an oblong plate or blade substantially rectangular in shape, which is preferably made of metal material and is inserted in axially slidable manner inside a slit which is preferably realized in the outer casing 6, or rather in the central block 10, immediately above the bifurcation of the two diverging branches of the Y.
In addition the oblong plate is preferably arranged astride the midplane of the outer casing 6, i.e. astride the lying plane of longitudinal axes A and B, and preferably extends substantially skimming the branch of outer casing 6 housing the secondary duct 8.
With reference to Figure 2, on the other hand, the moving device 32 is preferably accommodated between the two diverging branches of the V- or Y- shaped outer casing 6 that respectively house the main duct 7 and the secondary duct 8.
More in detail, the moving device 32 preferably comprises: a double-acting pneumatic cylinder 33 which is firmly fixed on the branch of the outer casing 6 housing the secondary duct 8, with the movable stem 34 arranged parallel and integral to an axial end of the movable shutter 31; and optionally also an electro-pneumatic control unit (not shown), which is adapted to control the flowing of pressurized air into the two chambers of the pneumatic cylinder 33, so as to be able to axially move, on command, the movable stem 34 and the movable shutter 31 integral thereto.
Preferably, electro-pneumatic control unit is additionally adapted to synchronize the movements of the movable shutter 31 with the movements of the screw bit 3.
Finally, with reference to Figures 1 and 2, the autofeed automatic screwdriver 1 is preferably moreover provided with an in-feed pipe 35 preferably of flexible type, which is adapted to connect the mouth of the secondary duct 8 to a screw feeding apparatus (not shown in the figures) which, in turn, is capable of automatically feeding a succession of screws 100 at inlet of the secondary duct 8 of the bit-holding head 2 via the in-feed pipe 35.
The screw feeding apparatus is a machinery already widely known in the field of autofeed automatic screwdrivers, and therefore won't be further described.
General operation of autofeed automatic screwdriver 1 is easily inferable from the description above, and therefore does not require further explanations.
With reference to Figure 5, operation of the bit holding head 2 will be hereinafter described assuming that the screw 100 is already stationary immediately downstream of the joining/connecting point between main duct 7 and secondary duct 8, at the screw-stop device 26.
When the autofeed automatic screwdriver 1 is activated, the moving device 32 of deflector assembly 30 moves the movable shutter 31 from the first operating position (see Figure 5) to the second operating position (see Figure 6), thus allowing the bit-holding rod 14 to descend along the main duct 7, up to arrange the movable piston 16 in abutment against the screw 100.
With reference to Figure 6, when the movable piston 16 of bit-holding rod 14 abuts against the head of the screw 100, the concave recess or seat 16b present on the front face of the piston accommodates the head of the screw 100 and simultaneously forces the screw 100 to arrange itself substantially coaxial to the longitudinal axis A of the screw bit 3.
The elastic resistance exerted by the screw-stop device 26 with every further movement of the screw 100, furthermore, facilitates the positioning of the head of the screw 100 inside the concave recess or seat 16b of the movable piston 16 and the possible centring and straightening up of the screw 100.
With reference to Figures 7 and 8, after having reached the screw 100 stationary at the screw-stop device 26, the bit-holding rod 14 continues its descent along the main duct 7 and brings the screw 100 in abutment against the board 200 or other support.
During the descent, the presence of the concave recess or seat 16b on the front face of movable piston 16 keeps the screw 100 substantially coaxial to the longitudinal axis A of the screw bit 3.
With reference to Figure 7, furthermore, during the descent, the contrast spring 17 of the bit-holding rod 14 prevents the movable piston 16 from stepping back with respect to the screw bit 3, thus preventing the shaped tip 3a of the screw bit 3 from coming out of the bottom of the concave recess or seat 16b and engage the head of the screw 100.
With reference to Figure 8, when the bit-holding rod 14 brings the tip of the screw 100 in abutment against the board 200 or other support, the contrast spring 17 is subjected to the thrust of the bit-holding rod 14 and allows the movable piston 16 to step back with respect to the screw bit 3, thus allowing the shaped tip 3a of the screw bit 3 to come out of the bottom of the concave recess or seat 16b and engage the head of the screw 100.
When the shaped tip 3a of screw bit 3 engages the head of the screw 100, the screw 100 becomes angularly integral to the screw bit 3 and, therefore, is forced to rotate around its longitudinal axis together with the bit-holding rod 14, thus getting progressively screwed into the board 200 or other support.
In other words, the operating mode of the automatic screwdriver 1 comprises the following steps:

placing the screw 100 to be screwed within a straight duct 7 which is open at the bottom and houses in axially slidable and rotatable manner a bit-holding rod 14 that holds a screw bit 3;
axially moving the bit-holding rod 14 towards the to-be-screwed screw 100 present or stationary inside the straight duct 7, so as to bring the bit-holding rod 14 in abutment against the head of the screw 100 and the screw bit 3 spaced in front of the head of the screw 100;
forcing the head of the screw 100 to engage a concave recess or seat 16b which is realized on the bit-holding rod 14 and is adapted to arrange the to-be-screwed screw 100 locally substantially coaxial to the longitudinal axis of the screw bit 3;
axially moving the bit-holding rod 14 towards the open end 7a of the straight duct 7 so as to push the screw 100 to be screwed in abutment against the support 200 held stationary at the open end 7a of the straight duct 7, while keeping the screw bit 3 spaced in front of the head of the screw 100;
axially pushing the bit-holding rod 14 against the support 200 so as to force the screw bit 3 to engage the head of the underneath screw 100 and make the screw 100 angularly integral to the bit-holding rod 14; and finally
rotating the bit-holding rod 14 about its longitudinal axis in order to screw on the screw 100 into the support 200.

The advantages connected to the particular structure of the bit-holding rod 14 are remarkable.
First of all, experimental tests have shown that the presence of the concave recess or seat 16b on the front face of the movable piston 16 significantly reduces the number of screws 100 that, after having been reached by the bit-holding rod 14, descend inside the lower portion of the main duct 7 slanted with respect to the longitudinal axis A of the screw bit 3. As a consequence, there is a remarkable reduction in the number of screws 100 that bend or break while being screwed into the board 200 or other support.
Thanks to the presence of the concave recess or seat 16b on the movable piston 16 that is able to automatically straighten the screw 100 during the movement of the latter inside the main duct 7, before reaching the support 200, it is possible to automate the screwing process virtually reducing to zero the risk of braking of the screws 100 when, at the open end 7a of the duct, the shaped tip 3a of screw bit 3 engages the head of the screw 100 and pushes the screw into the support 200.
In other words, in this case, the shaped tip 3a of screw bit 3 engages the head of the screw 100 only when the screw 100 is already perfectly coaxial to the longitudinal axis A of the screw bit 3 and, therefore, cannot break.
Furthermore, creation of the concave recess or seat 16b on a detachable portion of the movable piston 16, i.e. on the bushing 21, allows the bit-holding rod 14 to be easily adjusted to screws 100 with heads with different shapes.
In addition, the automatic movement of the movable shutter 31 prevents the movable piston 16 and the screw bit 3 from being subjected to wear.
Furthermore, experimental test have shown that the guillotine-like movement of the movable shutter 31 along a sliding plane P inclined with respect to the longitudinal axis B of secondary duct 8, and so as to form an extension of the upper wall of the secondary duct 8, allows the screws 100 to be more effectively deflected/directed towards the lower portion of the main duct 7.
Last but not least, the autofeed automatic screwdriver 1 is more compact than the ones currently known and, in addition, does not have movable parts that, during normal operation, can change the outer shape of the nose or oblong lower section of the automatic screwdriver 1.

Claims

An autofeed automatic screwdriver (1) comprising: a bit-holding head (2) that internally houses a rotatable screw bit (3), and is adapted to receive at inlet a succession of screws (100) which are arranged in sequence in front of the screw bit (3); and a motor assembly (4) which is adapted to drive into rotation the screw bit (3) about its longitudinal axis;
the bit-holding head (2) comprising: an outer casing (6) internally provided with a substantially straight, main duct (7) open at the bottom and which accommodates said screw bit (3) within an upper portion of the duct; and a bit-holding rod (14) which extends substantially coaxial to the longitudinal axis (A) of the main duct (7), is inserted in an axially slidable and rotatable manner in the outer casing (6) so as to partially protrude inside of the upper portion of the main duct (7), and is integral with the screw bit (3);
whereby the bit-holding rod (14) is mechanically connected to the motor assembly (4) so as to be driven into rotation about its longitudinal axis, characterized in that it further comprises a straight stem (15) having an axial end (15a) firmly connected to the screw bit (3) ; and a hollow movable piston (16) which is engaged in a pass-through and axially slidable manner by the straight stem (15) and by the screw bit (3), so as to be able to move forward and backward astride the straight stem (15) and the screw bit (3); the movable piston (16) being provided, at its face turned towards the shaped tip (3a) of the screw bit (3), with a concave recess or seat (16b) which has a shape substantially complementary to that of the head of the screws (100) to be screwed, and is adapted to receive the head of the screw (100) to be screwed located inside the main duct (7), while at same time arranging the same screw (100) substantially coaxial to the longitudinal axis of the screw bit (3).
Automatic screwdriver according to claim 1, characterized in that the bit-holding rod (14) moreover comprises a contrast spring (17) which is adapted to push and hold in elastic manner the movable piston (16) in a covering position in which said mobile piston (16) is located at the shaped tip (3a) of the screw bit (3) and internally accommodates the shaped tip (3a) upstream of the concave recess or seat (16b).
Automatic screwdriver according to claim 2, characterized in that the movable piston (16) is provided with a pass-through central hole (16a) which is engaged in axially sliding manner by the straight stem (15) and by the screw bit (3), and which communicates with the bottom of the concave recess or seat (16b); when the movable piston (16) is located in the covering position, the shaped tip (3a) of the screw bit (3) being entirely housed within said pass-through central hole (16a).
Automatic screwdriver according to claim 2 or 3, characterized in that the contrast spring (17) is located inside the movable piston (16).
Automatic screwdriver according to claim 2, 3 or 4, characterized in that the bit-holding rod (14) moreover comprises a stop member (18, 20) which is adapted to prevent the movable piston (16) from going beyond said covering position.
Automatic screwdriver according to any one of the preceding claims, characterized in that the concave recess or seat (16b) is realized on a removable portion (21) of the movable piston (16).
Automatic screwdriver according to claim 6, characterized in that the movable piston (16) consists of a cup-shaped body (20) and of a bushing (21) firmly fixed to one another preferably in manually detachable manner; the concave recess or seat (16b) being realized on said bushing (21) .
Automatic screwdriver according to any one of the preceding claims, characterized in that the screw bit (3) is fixed to the axial end (15a) of the straight stem (15) in detachable manner.
Automatic screwdriver according to any one of the preceding claims, characterized in that the bit-holding head (2) moreover comprises a substantially straight, secondary duct (8) that branches off obliquely from the main duct (7) and is dimensioned so as to convey a succession of screws (100) into the main duct (7), below the screw bit (3); the longitudinal axis (B) of the secondary duct (8) being preferably inclined with respect to the longitudinal axis (A) of the main duct (7) by an angle (α) of less than 75°.
Automatic screwdriver according to claim 9, characterized in that the bit-holding head (2) moreover comprises a screw-stop device (26) which is arranged along the lower portion of the main duct (7), downstream of the joining/connecting point with the secondary duct (8), and is adapted to stop each screw (100) descending along the main duct (7) towards the open end (7a) of the same main duct (7).
Automatic screwdriver according to any one of the preceding claims, characterized in that the bit-holding head (2) moreover comprises a second contrast spring (15) which is interposed between the outer casing (6) and the bit-holding rod (14), and is adapted to elastically counteract the advancing/descent of the bit-holding rod (14) within the main duct (7), towards the open end (7a) of the same main duct (7).
Automatic screwdriver according to any one of the preceding claims, characterized in that the bit-holding head (2) moreover comprises a deflector assembly (30) which is located substantially at the joining/connecting point between the main duct (7) and the secondary duct (8), and is adapted to channel the screws (100) coming out from the secondary duct (8) towards the lower portion of the main duct (7).
Automatic screwdriver according to claim 12, characterized in that the deflector assembly (17) comprises: a plate-like movable shutter (31) which is inserted in an axially sliding manner in the outer casing (6) so as to be able to move in a guillotine-like manner on a sliding plane (P) inclined with respect to the longitudinal axis (a) of the main duct (7), between a first operating position in which the movable shutter (20) obliquely intersects the main duct (7), at the joining/ connecting point with the secondary duct (8), and a second operating position in which the movable shutter (20) does not protrude inside the main duct (7); and a moving device (21) adapted to place the movable shutter (20) alternately in the first or in the second operating position.
Automatic screwdriver according to claim 13, characterized in that the sliding plane (P) of the movable shutter (31) is substantially orthogonal to the lying plane of the main (7) and secondary (8) ducts.
Automatic screwdriver according to any one of the preceding claims, characterized in that the motor assembly (4) is moreover adapted to move axially the bit-holding rod (14), so as to move the screw bit (3) along the main duct (7), from and towards the open end (7a) of the main duct (7) .
An operating method of an autofeed automatic screwdriver (1) characterized by comprising the steps of:
- placing the screw (100) to be screwed within a straight duct (7) which is open at the bottom and houses in axially-sliding and rotatable manner a bit-holding rod (14) that holds a screw bit (3);

- axially moving the bit-holding rod (14) towards the to-be-screwed screw (100) present or stationary inside the straight duct (7), so as to bring the bit-holding rod (14) in abutment against the head of the screw (100) and the screw bit (3) spaced in front of the head of the screw (100);

- forcing the head of the screw (100) to engage a concave recess or seat (16b) which is realized on the bit-holding rod (14) and is adapted to arrange the to-be-screwed screw (100) locally substantially coaxial to the longitudinal axis of the screw bit (3) ;

- axially moving the bit-holding rod (14) towards the open end (7a) of the straight duct (7) so as to push the to-be-screwed screw (100) in abutment against the support (200) held stationary at the open end (7a) of the straight duct (7), while keeping the screw bit (3) spaced in front of the head of the screw (100);

- axially pushing the bit-holding rod (14) against the support (200) so as to force the screw bit (3) to engage the head of the underneath screw (100) and make the screw (100) angularly integral with the bit-holding rod (14); and finally

- rotating the bit-holding rod (14) about its longitudinal axis in order to screw on the screw (100) into the support (200).