JP2629905B2 - Automatic screw tightening device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an automatic screw tightening device for tightening a screw fed through a screw feed hole to a work by pushing down and moving a bit.

(Prior Art) A conventional screw tightening device (for example, Japanese Utility Model Publication No. 62-31222)
No. JP-A-57-54039, U.S. Pat. No. 2,998,996) discloses a screw feeding hole for feeding a screw, a retainer for holding a screw, a bit for turning a screw, a driving source for rotating the bit, and the like. It has. When tightening the screw, press the tip of the bit against the screw head while holding the screw head with the retainer, rotate the bit, turn the screw, and tighten the screw to the work.

For example, as shown in FIGS. 4 (A) and 4 (B), a screw 5 inserted through a screw feed hole 3 formed in the guide cylinder 2 of the holder 1
The bit 6 is pressed against the screw head 5a, and the bit 6 is rotated and screwed to tighten the screw 5 to the work. At this time, the screw head 5a is held by a pair of jaw-shaped holders 8, 9.

(Problems to be Solved by the Invention) However, according to the conventional screw tightening device, since the screw head is in contact with the retainer from the start of screw tightening to the completion of tightening, the screw head has a non-round shape. When the bit rotates, the cage that comes in contact with the screw head vibrates, and this vibration not only generates noise, but also easily damages the screw head, and the screw tightening torque is not stable. There are problems such as shortening of the life of the device.

Further, according to the screw tightening device of the type described in JP-A-57-54039, in which the retainer is opened by the operating rod immediately before the bit pushes the screw, the timing for releasing the retaining of the screw by the retainer is determined. Difficult to take. For example, if the release timing is too late, the above-mentioned various adverse effects accompanied by the vibration of the retainer will occur. If the release timing is too fast, the screw will fall down, making it impossible to tighten.

The present invention has been made in order to solve such a problem, and the time required for the screw head to come into contact with the retainer can be set by appropriately setting the dissociation timing of the retainer from the screw when tightening the screw. It is an object of the present invention to provide an automatic screw tightening apparatus which can reduce the above-mentioned problem and solve the above-mentioned problem caused by vibration caused by long-time rotational contact.

(Means for Solving the Problems) For that purpose, an automatic screw tightening device of the present invention holds a guide cylinder having a screw feed hole for inserting a screw, and a screw head fed to one end of the guide cylinder. A pair of catchers, and a bit inserted into the guide cylinder, which presses the screw head of the screw to turn the screw, and wherein the screw held by the catcher is tightened to the work by pushing and rotating the bit. In the attaching device, the catcher is gradually moved from the closed position to the open position while being in contact with the lower end of the screw head as the screw is pushed into the work by rotating and pushing the bit, and the linking means for interlocking the pair of catchers with each other. When the catcher reaches a predetermined opening during the tightening of the screw and the inclined surface of the catcher to be opened, the catcher does not interlock with the lowering operation of the bit, and A cam means for causing the roller abutting on the cam interlocking with the engaging means to climb over the top dead center of the cam surface and rapidly opening the catcher by the urging force of a spring; and pressing the catcher inclined surface by pressing the screw head. A force point, a rotation center of the cam as a fulcrum, and the cam surface as an action point to open the catcher, and after completion of screw tightening, release the cam means to close the catcher. I do.

(Operation) According to the automatic screw tightening device of the present invention, when the bit is pressed against the screw head of the screw supplied from the screw feed hole and rotation starts, the screw whose screw head is held by the catcher is tightened to the work. Be included. At this time, as the screw tightens, the inclined surface of the catcher is pushed open by the screw head of the screw, and the catcher is gradually expanded. When the opening of the catcher reaches a predetermined opening, the roller contacting the cam of the cam means via the linking means interlocking with the catcher passes over the top dead center of the cam, and the displacement of the roller causes the urging force of the spring to move the linking means. The catcher suddenly opens via the, and the catcher previously holding the screw is separated from the screw. Thereafter, the screw is tightened to the work by rotation of the bit with the screw head being disengaged from the catcher.

(Example) An example of the present invention will be described with reference to the drawings.

As shown in FIGS. 1 and 2, an air cylinder 11 for driving a cam mechanism described later to a return state is attached to a side wall of the guide cylinder 10. A screw feed hole 10a is provided for feeding the screw by freely dropping the screw through the inside of the guide tube 10,
The screw feed hole 10a also serves as a loose insertion hole through which the bit 12 is inserted. The tip of the bit 12 is formed with a cross tip 12a for pushing a screw and turning the screw.

The guide portion 10b extending to the lower end of the guide tube 10 also has a role of a guide plate for setting a screw tightening position for a work to be tightened. Holder 15 fixed to the side wall of guide tube 10
The arm portion 15a extends in the horizontal direction, and a lever support portion 15b rises upward in an L-shape at the tip. A lever 17 is swingably provided on an inner fixing pin 16a fixed to the side wall of the lever support portion 15b. A torsion coil spring 18 is attached to an outer fixing pin 16b fixed to the side wall of the lever support portion 15b, and one end 18a of the torsion coil spring 18 contacts the upper protrusion 17a of the lever 17 and urges the upper protrusion 17a in a direction away from the guide cylinder 10. doing. The other end 18b is fixed to the lever support 15b.
A roller 21 that is rotatable with respect to the fixed shaft 20 is provided at the tip of the lower projection 17b of the lever 17.

A retainer 26 that is rotatably provided on fixing pins 23 and 24 that protrude in an L shape from the lower end side wall of the guide cylinder 10 includes a fixing pin.
A pair of synchronous gears 3 that mesh with each other with the center axes 23 and 24
0, 31, a pair of catchers 28, 29 extending from the synchronous gears 30, 31, respectively, and these catchers 28, 29
The spring supporting portions 32 and 33 for attaching the tension springs 38 for urging in the closing direction are formed integrally with each other.

The plate cam 35 provided integrally with the catcher 29 and the synchronous gear 31 has a cam surface 35a on its cam surface 35a.
The roller 21 is in contact with the urging force of. In the state shown in FIG. 2 before the screw tightening is started, the catcher
The lower ends of the screw heads 25a of the catcher inclined surfaces 28a, 29a formed on the inner walls of 28, 29 are seated.

When the screw head 25a advances while rotating downward in FIG. 2 by the pushing rotation of the bit 12, the screw head 25a becomes inclined surfaces 28a, 29.
a and push the catcher 2 around the fixing pins 23 and 24
8, 29 are expanded. When the opening of the catchers 28 and 29 reaches a predetermined opening, the roller 21 abutting on the cam 35 descends on the cam surface 35a, and the lever 1 is pressed by the urging force of the torsion coil spring 18.
The pressing force of the roller 21 presses the cam 35 via 7, and the catchers 28 and 29 are rapidly opened about the shafts 23 and 24.

When the catchers 28 and 29 are returned to the closed side positions, the drive return cam 40 is lowered in FIG. 2 by the extension of the air cylinder 11 serving as the drive source, and the slope 17 d of the upper protrusion 17 a is opposed to the torsion coil spring 18. Press down and rotate the lever 17 counterclockwise about the inner fixing pin 16a as the center axis to
Release the pressing force to 35, and the tension spring
The catchers 28 and 29 are closed in the state shown in FIG.

 Next, the operation of the above-described embodiment will be described.

First, a screw is inserted through the screw feed hole 10a of the guide cylinder 10, and the screw head 25a is locked to the catcher inclined surfaces 28a, 29a. Then, the state shown in FIG. 2 is obtained. Then, the bit 12 is lowered, and as shown in FIG. 3 (A), the cross tip 12a of the bit 12 is pressed against the screw head 25a.

Next, the bit 12 is rotated while being pressed against the screw 25, and the screw 25 is screwed into the screw hole of the work W. Then the screw
As the 25 is tightened to the work W, the lower end of the screw head 25a gradually pushes out the inclined surfaces 28a, 29a, and the catchers 28, 29 are gradually opened in the direction of the arrow as shown in FIG. 3 (B). When the catchers 28 and 29 further increase the opening, the cam surface 35a of the cam 35 that rotates around the fixing pin 24
The roller 20 starts to descend on the cam surface from the cam surface 35b, and the catcher 28 and the catcher 29 integrated with the cam 35 are rapidly rotated in the direction of arrow A shown in FIG. Move. At this time, the contact of the screw head 25a with the catchers 28 and 29 is released. At this time, the speed at which the catchers 28, 29 open rapidly is much faster than the speed at which the screw 25 descends. That is, the catchers 28 and 29 advance in the direction indicated by the arrow with respect to the screwing speed of the screw 25.

Thereafter, with the screw 25 being released from the catchers 28 and 29,
25 is tightened while being gradually screwed to the work W. When the screw 25 is completely fastened to the work W by the pressing rotation of the bit 25, the state shown in FIG. In this state, the rotation of the bit 12 is stopped, and screw tightening is completed.

When returning the catchers 28 and 29 to the original closed side positions, the drive return cam 40 is driven by the driving force of the air cylinder 11.
Is lowered, the inclined surface 17 contacting the drive return cam 40
The lever 17 having d is rotated in the direction of arrow B in FIG. 3C around the inner fixing pin 16b, and the roller 21 at the tip of the lever support 17b is disengaged from the cam 35. Then, the spring supporting portions 32 and 33 are pulled toward each other by the tensile force of the tension spring 38, and the catchers 28 and 29 are closed at the positions shown in FIG. 3 (A). This allows the catcher
28 and 29 are returned to their original positions.

According to the above-described embodiment, the catcher is pushed open using the thrust in the traveling direction of the screw while the screw is being tightened, and the catchers 28 and 29 are disengaged from the screw head 25a on the way. Therefore, the time for pressing the catchers 28 and 29 against the screw head 25a can be reduced to a minimum by setting the cam profile and the like of the cam 35, and the vibration of the catcher at the time of contact due to the rotation of the screw can be minimized. Thus, noise is reduced, screw head scratches are reduced, breakage and destruction of the catcher due to wear, fatigue and the like are avoided, and the life of the catcher is improved. Further, since the catcher separates from the screw head while the screw is being tightened, there is an effect that the tightening torque by the bit is considerably more stable than before.

In the case of the conventional screw tightening device, the screw head is easily damaged by the vibration of the portion in contact with the screw head, and there are disadvantages such as the tightening torque and the like being unstable, but according to this embodiment,
Such disadvantages are eliminated, and since the time for holding the screw head by the catcher is short, various adverse effects due to vibration are eliminated. In particular, even if the screw has a non-round screw head, the screw can be tightened while minimizing vibration and the like.

In the above-described embodiment, the pair of catchers is driven using the synchronization gear. However, the synchronization mechanism for driving the catcher is not limited to this, and a lever, a cam, or the like may be used. The means for pulling the pair of catchers together is not limited to a tension spring, and a compression spring leaf spring may be used. The driving means of the lever is not limited to the torsion coil spring, and other driving means may be used. The driving means for the lever returning operation is not limited to the air cylinder, but may be another driving means.

(Effects of the Invention) As described above, according to the automatic screw tightening device of the present invention, the linking means for interlocking the catchers holding the screws with each other and the screw being pushed into the work by the rotary extrusion of the bit. Accordingly, a catcher inclined surface for gradually moving the catcher from the closed position to the open position while being in contact with the lower end of the screw head, and a cam interlocking with the linking means when the catcher reaches a predetermined opening during the tightening of the screw. And the cam means for rapidly opening the catcher by the biasing force of the spring when the roller abutting on the cam surface passes over the top dead center of the cam surface, so that the catcher is quickly dissociated from the screw head while the screw is being tightened. Vibration, noise transmitted to the catcher is minimized, damage to the screw head, catcher, etc. is reduced to a minimum, and screws with non-round screw heads In this case, there is an effect that the screw can be tightened with a stable tightening torque.

[Brief description of the drawings]

FIG. 1 is a partially cutaway perspective view showing an embodiment of the present invention, and FIG.
The figure is a sectional view of the embodiment shown in FIG. 1, and FIGS. 3 (A) and 3 (B).
(C) is an explanatory diagram showing the operation of the embodiment of the present invention over time, and FIG. 4 is a schematic partial configuration diagram for explaining a conventional example. 10 ... guide cylinder, 10a ... screw feed hole, 11 ... air cylinder, 12 ... bit, 17 ... lever, 18 ... torsion coil spring (spring), 25 ... screw, 26 ... retainer , 28, 29… Catcher, 28a, 29a… Catcher slope, 30, 31… Synchronous gear, 35… Plate cam, 38… Extension spring.

Claims (1)

(57) [Claims] 1. A guide cylinder having a screw feed hole for inserting a screw, a pair of catchers for holding a screw head fed to one end of the guide cylinder, and a screw of the screw inserted into the guide cylinder. An automatic tightening device comprising a bit for pressing a head and turning a screw, wherein the screw held by the catcher is tightened to a work by pushing and rotating the bit, wherein a linking means for interlocking the pair of catchers with each other; As the screw is pushed into the work by rotary extrusion of the bit, a catcher inclined surface for gradually moving the catcher from the closed position to the open position while contacting the lower end of the screw head, and the catcher in the middle of tightening the screw When a predetermined degree of opening is reached, the roller that abuts on the cam that is not linked to the lowering operation of the bit and that is linked to the linking means is the cam. A cam means for jumping over the top dead center and rapidly opening the catcher by the urging force of a spring, wherein the inclined surface of the catcher is a force point by pressing the screw head, the rotation center of the cam is a fulcrum, and the cam surface An automatic screw tightening device characterized in that the catcher is opened by setting the action point as a point of action, and the catcher is closed by releasing the cam means after the screw tightening is completed.