Screw-driving device

Abstract: A screw-driving device, which can drive screws continuously one by one, comprises a casing coupled to a screwdriver, a slide member slidably moved in reciprocating movement in the casing and a mechanism for feeding a screw-holding tape by one-step pitches corresponding to the distances between the adjacent screws on the tape. The tape feeding mechanism includes a guide slot provided in the casing, and a two-arm lever pivotally connected to the slide member and pivotally moved to perform indexing of the screws to a position aligned with the screwdriver by a pin fitted into the inclined section of the guide slot. A pawl member with a pawl fitted into one of the grooves at one lateral edge of the tape is pivotally connected to the end of the other arm of the two-arm lever and is biased toward the tape by a spring. At the same time, a further pawl member entering one of the grooves at the opposite side of the tape is pivotally connected to the slide member and is biased toward the tape.

Description: The present invention relates to a screw-driving device which is adapted to be coupled to a screwdriver and continuously drive screws held in a screw-holding tape in line one by one during a pressure stroke, which comprises a tubular casing coupled to the forward end of said screwdriver; a slide member slidably fitted for reciprocating movement in the casing; a return spring for returning said slide member to its initial extended position during a return stroke; and a mechanism provided in the slide member for feeding the screw-holding tape by one-step pitches, said tape-feeding mechanism including a guide slot provided in the casing, a two-arm lever having a pin fitted into the guide slot at the end of one arm of the two-arm lever and pivotably connected to said slide member, said two-arm lever having at the end of the other arm thereof a pawl member which is engageable in one of grooves or apertures at one lateral edge of the screw-holding tape guided along a guide passage traversing the slide member BACKGROUND OF THE INVENTION A screw driving device of this kind is known in the art from DE-U- 92 07 847. In the device of prior art, a two-arm lever is pivotably connected to the slide member, and a pin at one end of the two-arm lever is fitted into the guide slot of the casing with the sprockets being rotatably mounted on the other end of the two-arm lever. The sprockets are provided with an additional means for disconnecting the interlick between the sprockets and the two-arm lever during a return stroke in that the two opposite sprockets are each provided on the circumferential surface thereof with a number of radial grooves arranged at equal distances and a traverse through-hole is provided on the two-arm lever at a position opposite the grooves of the sprockets. Two locking bars, energized toward the respective sprockets at both sides of the two-arm lever by a spring between the locking bars, are inserted and fitted into the through-hole of the two-arm lever. The end surfaces of the locking bars directed to the sprockets are bevelled. The device of DE-U-92 07 847 has a complicated construction with excessive additional means such as the locking bars, spring means, sprocket grooves and the like being required in addition to the sprockets. Moreover, since the diameter of the sprocket is determined by the pitch of the grooves in the tape and the number of teeth, a large space is generally required for pivotal movement of the two-arm lever. As a result, the sliding member and the casing must be enlarged, resulting in increased cost and decreased handiness. In addition, the pivotal motion of the two-arm lever with its two sprockets induces large inertial force so that when the pin of the two-arm lever abuts with the surface of the guide slot at the end of a return stroke, a substantial shock is produced, whereby the surface of the guide slot and of the control pin are damaged. Another type of screw-driving device is known in the art from US 4,059,034 which comprises a tubular casing coupled to the front end of the screwdriver, a slide member slidably fitted into the casing through a return spring, and a mechanism provided within the slide member to feed a screw-holding tape by one-pitch steps corresponding to the intervals between the adjacent screws on the tape. In such a tape feeding mechanism, a pin is provided on one side surface of a sprocket having a number of projections on both side edges of the outer periphery thereof, and the pin is fitted into a guide slot provided on one side surface of the tubular casing and extending obliquely and then parallel relative to the longitudinal direction of the casing. When the slide member is pressed against a workpiece, the slide member is forced into the casing and the pin is moved along the guide slot to thereby rotate the sprocket by one-pitch steps corresponding to the distance between the adjacent screws on the tape, so that the screw-holding tape having the grooves fitted onto the sprocket is fed by one pitch. However, after the screw on the screw-holding tape is driven into the workpiece by the screwdriver being rotated, the pin of the sprocket is returned through the rectilinear section of the guide slot by the return spring within the casing and, then, passed through the inclined section of the guide slot; therefore, the sprocket will be rotated in the opposite direction by one pitch and returned to the original position. For this purpose, a wide variety of complicated mechanisms have hitherto been used to disconnect the interlock between the sprocket and the guide slot near the end of the return stroke. BRIEF SUMMARY OF THE INVENTION It is therefore the object of the present invention to provide a screw-driving device having a mechanism for feeding a screw-holding tape, which eliminates the above-mentioned disadvantages of sprocket devices of prior art and which is simple in construction. This object is achieved in accordance with the invention with a device characterized in that said pawl member is pivotably connected to said other arm and is biased by means of a spring so that the pawl on the pawl member is pivotably urged toward the screw-holding tape and simultaneously, a further pawl member with a further pawl is pivotably connected to the slide member and engageable in one of further grooves or apertures of the screw-holding tape by another spring, said pawls of the pawl members each having a first surface oriented in the feed direction of the screw-holding tape and extending substantially perpendicular to the surface of the screw-holding tape when the respective pawls engage in one of the grooves or apertures of the screw-holding tape, and a second surface oriented opposite the feed direction of the screw-holding tape and inclined so as to form an acute angle with the respective first surface. In further accordance with the invention, there is provided a screw-driving device further comprising a mechanism provided in said slide member for pulling back said screw-holding tape in the direction opposite the tape feeding direction, said tape pulling-back mechanism including projections extending toward each other and provided on both said pawl member pivotably connected to said two-arm lever and said further pawl member pivotably connected to said slide member at the ends of both said pawl members away from the pawls thereof, and a two-arm lever pivotally connected to said slide member and adapted to engage said opposite projections for pulling back said pawls of both pawl members in the direction away from the groove or aperture of the screw-holding tape. According to a further aspect of the invention, there is provided a screw-driving device further comprising a tape-holding means provided on the back portion of the side of said casing at the side of said slide member provided with a tape-inserting opening, said tape-holding means including a mount secured to the back portion of said casing and a tape-holding member pivotably supported by a pivotal shaft secured to said mount in a parallel manner to the plane of said casing, said tape holding member being supported on said pivotal shaft so that the guide groove thereof is obliquely inclined upwardly toward the tape-inserting opening of said slide member. BRIEF DESCRIPTION OF THE DRAWINGS These and other objects, features and advantages of the invention will become more apparent upon a reading of the following detailed specification and drawings, in which: Fig. 1 is a side view showing a first embodiment of a screw-driving device according to the present invention, with parts partially broken away, and with the position where indexing of a screw is completed (the driving operation is commenced). Fig. 1a is a fragmentary view of a pawl member pivotally secured to a two-arm lever. Fig. 2 is a longitudinal sectional view taken along Line II-II in Fig. 1. Fig. 3 is a side view similar to Fig. 1, showing the device with the position where indexing of a screw is commenced during the return stroke. Fig. 4 is a fragmentary plan view showing an example of a screw-holding tape having grooves opening outwardly along both lateral edges thereof. Fig. 5 is a side view showing a second embodiment of a screw-driving device according to the invention, with parts partially broken away, and with the position where indexing of the screw is completed (the driving operation is commenced). Fig. 6 is a longitudinal sectional view taken along Line VI-VI in Fig. 5. Fig. 7 is a side view similar to Fig. 5, showing the device with the position where indexing of the screw is commenced during the return stroke. Fig. 8 is a perspective view of a tape-holding device according to the invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS Now, the invention will be explained in detail by way of embodiments shown in the drawings. Referring to Figs. 1 to 3, a screw-driving device according to the invention comprises a tubular casing 1 and a slide member 2 slidably fitted into the casing 1. In using the screw-driving device, a cylinder part 3 extending out of the back end of the casing 1 is connected to a screwdriver. As shown in Fig. 2, a driver bit 4 at the front end of the screwdriver enters into a through-hole 2c within the slide member 2, which is normally energized forwardly by a return spring 5. In Figs. 1 to 3, according to the invention, the slide member 2 is provided therein with a mechanism for feeding a screw-holding tape 7, on which screws 6 are held in line at equal intervals, by one-step pitches corresponding to the distances between the adjacent screws. As the screw-holding tape, two types can be used, one having grooves 7a and 7b opening outwardly along both lateral edges of the tape at a constant pitch, as shown in Fig. 4, and the other having apertures along both lateral edges of the tape at a constant pitch (not shown). The mechanism for feeding the screw-holding tape includes a guide slot 8 for a pin described later and provided to pass through one side wall 1a of the casing 1, as shown in Fig. 1. The guide slot 8 comprises a rectilinear section 8b extending longitudinally along the casing; an inclined section 8a inclined downwardly and forwardly with respect to the rectlinear section 8b, and a short rectlinear section 8c extending longitudinally along the casing 1 and in front of the inclined section 8a in a continuous manner therewith. On the other hand, a two-arm lever 9 is pivotally connected by a pin 10 at one side parallel to the axis B of the driver bit 4 within the slide member 2, as viewed in the sectional plan view of Fig. 2, and a cylinder member 12, which is rotatably fitted onto a pin 11 provided at the end of one arm 9a of the two-arm lever 9, is fitted into the short rectlinear section 8c (Fig. 1) of the guide slot 8 of the casing 1. Accordingly, even when a screw-holding tape 7 extending out of the slide member 2 is pulled suddenly in either direction, the two-arm lever 9 which engages with the screw-holding tape 7 through a pawl 13a of a pawl member 13 (Fig. 1a) can not be pivotally moved, so that the screw 6 at the position where indexing of the screw has been completed is not forced out by the driver bit 4, and, therefore, safety is ensured. A plate-like pawl member 13 is pivotally connected to the front end of the other arm 9b of the two-arm lever 9 for pivotal motion about a pin 14 and is energized toward the screw-holding tape 7 by a spring 15, which, as apparent from Fig. 1, is hooked at one end to a projection 16 on the side wall of the pawl member 13 and at the other end to a projection 17 provided on the pawl member 13. The pawl 13a of the pawl member 13 is normally energized by the spring 15 to thereby be inserted into one of the grooves 7a (Fig. 4) provided at one lateral edge of the screw-holding tape 7 at equal pitches. The screw-holding tape 7 is guided through the guide passage, which is defined by a screw-holding tape guiding wall 18 vertically passed through the slide member 2 transversely to the longitudinal direction thereof in Fig. 1 and by a screw-holding tape guiding member 19 of a channel-shaped cross-section (Fig. 2) secured to the slide member 2 opposite the screw-holding tape guide wall 18. Further, the cylinder member 12 at the end of one arm 9a of the two-arm lever 9 is passed through the circular arc-like slot 20 in the side wall of the slide member 2 and extends into the guide slot 8 of the casing 1, as shown in Fig. 2. In the maximum extended position of the slide member 2, as shown in Fig. 2, a stopper 30 secured to the front end portion of the casing 1 on the side surface 1b opposite the guide slot 8 so as to extend inwardly of the casing 1 is brought into abutting engagement with the inner end of a slot 31 extending longitudinally of the slide member 2 biased by the spring 5. In a pressure stroke where the slide member 2 is to be pressed into the casing 1, the cylinder member 12 in the completed position of indexing shown in Fig. 1 is slightly moved backwards along the short rectilinear section 8c of the guide slot 8 of the casing 1, and then, obliquely and upwardly along the inclined section 8a, so that one arm 9a of the two-arm lever 9 is pivotally moved about the pin 10 counterclockwise while the other arm 9b is pivotally moved downwardly, to thereby return the pawl 13a of the pawl member 13 downwardly by one pitch corresponding to the distance between the adjacent screws on the tape. In this case, the pawl 13a of the pawl member 13 is pushed back from the groove 7a by one of the lateral edges of the screw-holding tape 7 against the biasing force of the spring 15 and is returned to the position shown in Fig. 3 sliding over the screw-holding tape 7. In order to prevent the screw-holding tape 9 from being returned together with the pawl 13a during the pressure stroke, a further T-shaped pawl member 21 (shown by the dotted lines in Figs. 1 and 3) is pivotally connected by a pin 22 at the side opposite the pawl member 13 parallel to the axis B of the driver bit 4, as viewed in the plan sectional view of Fig. 2. The pawl member 21 is normally biased toward the screw-holding tape 7 by a torsion spring 24 which engages at one end thereof the inner wall of the slide member 2 and at the other end a projection 23 provided on the lower horizontal portion of the pawl member 21 at the end opposite the pawl 21a (Fig. 3), so that the pawl 21a at the front end of the pawl member 21 is brought into engagement with the groove 7b (Fig. 4) at the other lateral edge of the screw-holding tape 7. In a portion of the end of the return stroke (Fig. 3), the pawl member 13 of the other arm 9b of the two-arm lever 9 is forcibly pushed up by the inclined section 8a of the guide slot of the casing 1, and, at that time, the pawl 13a of the pawl member 13 pushes the screw-holding tape 7 up by one-step pitch corresponding to the distance between the adjacent screws on the tape until the tape is restored to the position where indexing of the screw is completed and it is aligned with the axis B of the driver bit 4, as shown in Fig. 1. In this embodiment, the further pawl member 21 is provided at the side opposite the space from the pawl member 13; however, these pawl members may be provided at the same side if they can be arranged so as not to interfere with each other. In this case, the grooves or apertures in which the pawls of both pawl members engage must be provided along the same lateral edge of the screw-holding tape 7, with the pitches thereof being offset from each other. Further, the slide member 2 is provided with a mechanism for freely pulling back the screw-holding tape 7 in the direction opposite the tape feeding direction A (Figs. 1 and 3). In addition to the above-mentioned projection 23 (Figs. 2 and 3) provided at the end opposite the pawl 21a of the further T-shaped pawl member 21, the pulling-back mechanism includes a projection 25 (Figs. 2 and 3) provided at the end opposite the pawl 13a of the pawl member 13 and extending inwardly. Particularly referring to Fig. 3, a further two-arm lever 26 is pivotally connected at a pin 27 to the interior of the slide member 2, one arm 26a of the other two-arm lever 26 extending into the opening 2a on the upper surface of the slide member 2 and the other arm 26b extending forwardly of the respective projections 25 and 23 of both pawl members 13 and 21 with a slight distance left between it and the pawls. The other arm 26b is normally biased to be brought into abutting engagement with the back surface of the tape guide member 19 by a torsion spring 28 wound around the pin 27. With the construction of this pawl pulling-back mechanism, when the front end of the one arm 26a of the two-arm lever 26 which exists in the opening 2a is pressed forward, the other arm 26b is pivotally moved backwardly about the pin 27 until it pushes the projections 23 and 25 of both pawl members 13 and 21, so that the pawls 13a and 21a disengage the grooves 7a and 7b at both lateral edges of the screw-holding tape 7, respectively. Accordingly, the screw-holding tape 7 can be freely pulled back. This allows the screws to be replaced by different screws midway during the screw-driving operation, and further allows any screws which have been fed by mistake to be returned to the condition where the screws are to be driven. Moreover, the casing 1 is provided with a tape holding device at the back portion of the side surface corresponding to a tape inserting side. Referring to Figs. 1, 3 and 8, the tape-holding device comprises a mount 40 attached to the back portion of the casing 1, and a tape-holding member 42 supported on the mount 40 for pivotal motion about a shaft 41 parallel to-the plane of the casing 1. The tape holding member 42 has a guide groove 43 for holding the tape, and the guide groove 43 is supported by the shaft 41 so that it is inclined obliquely and upwardly toward the tape-inserting opening of the slide member 2 at the front of the casing 1, as is apparent from Figs. 1, 3 and 8. With this tape-holding device, the tape-holding member 42 is supported at the front end by a short leg 45 and at the back end by a long leg 44, and therefore, has a different radius of pivotal motion at the two ends. Accordingly, during pivotal motion of the tape-holding member 42, the front end of the guide groove 43 describes the path of a small circular arc, and simultaneously, the back end thereof describes the path of a great circular arc, thereby enlarging the range of angle of pivotal motion to guide the tape and smoothly feed the tape. Next, a second embodiment of the present invention is explained with reference to Figs. 5 to 7. In the drawing, the same reference characters are affixed to the parts similar to those in the first embodiment, and the explanation thereof is omitted, only the different points being explained. In a screw-driving device according the second embodiment, as is apparent from Figs. 5 and 6, an auxially torsion spring 34 is provided around the outer periphery of a cylinder portion 33 enclosing a pin 10 in the center of the pivotal motion of the two-arm lever 9 in the slide member 2. One end 34a of the auxially torsion spring 34 is in abutting engagement with a recess of the slide member 2, as shown in Fig. 5, and the other end 34b thereof is in abutting engagement with the stepped portion of the other arm 9b of the two-arm lever 9, as is apparent from Figs. 5 and 6, so that the two-arm lever 9 is normally biased clockwise. Consequently, even when the screw-holding tape 7 has suddenly been pulled down by an external force in the position of stoppage in Fig. 5 where indexing of the screw is completed, such a sudden pivotal motion of the two-arm lever 9 during a stoppage of the device can be more surely prevented than in the first emobodiment, since the two-arm lever 9 is normally in abutting engagement with the guide wall of the short rectilinear section 8c of the guide slot 8 by the force of the auxiliary spring 34 actuating through the pawl 13a of the pawl member 13 in the direction opposite that of the external force. Now, operation of the screw-driving device of the first embodiment according to the invention will be briefly explained. When the front end of the slide member 2 is pressed against the member or workpiece into which screws are to be driven, the cylinder member 12 around the pin 11 of the two-arm lever 9 is moved back along the short rectilinear section 8c of the guide slot 8 of the casing 1, and then, the two-arm lever 9 is pivotally moved counterclockwise as viewed in Fig. 1 by the inclined section 8a, while the pawl 13a is pushed out of the groove 7a or aperture at one lateral edge of the tape against the force of the spring 15 and is moved down, sliding over the screw-holding tape 7, until it comes to fit into the following groove or aperture of the tape again after movement of the screw-holding tape by the step of one pitch. During such a downward movement of the pawl 13a, the pawl 21a of the other pawl member 21 remains engaged with the groove 7b (Fig. 4) or aperture at the lateral edge opposite the one lateral edge of the tape by the biasing force of the spring 24, so that the tape can not be returned and maintains its position. When the slide member 2 is further pressed while the cylinder member 12 of the two-arm lever 9 is moved along the rectilinear section 8b of the guide slot 8, the front end of the driver bit 4 is passed through the through-hole 2c (Fig. 2) of the slide member 2 and engages the head of the screw 6, thereby driving the screw 6 into the workpiece by the driver bit 4 driven in rotation by a screwdriver. In a return stroke, the cylinder member 12 of the two-arm lever 9 is moved back passing through the rectilinear section 8b by the return spring 5 and comes to the position shown in Fig. 3. Then, when the cylinder member 12 enters the inclined section 8a, the two-arm lever 9 begins to be pivotally moved clockwise and the tape 7 is fed by one pitch in the direction A by the pawl 13a of the pawl member 13 of the other arm 9b, which engages the tape 7, and comes to the position shown in Fig. 1. During such a feed of the tape, the pawl 21a of the further pawl member 21 is pushed out of the groove 7b or aperture against the spring 24 and slides over the tape 7 being fed by one pitch until the pawl 21a fits into the following groove 7b or aperture of the tape again. The screw-holding tape-feeding mechanism as set forth in claim 1 is considerably simple in construction and cheap to produce. With the construction as set forth in claim 2, even when the screw-holding tape extending out of the screw-driving device is suddenly pulled, the two-arm lever engaging the screw-holding tape through the pawl of the pawl member can not be pivotally moved, and therefore, a danger of the screw, which is already at the indexed position, being pushed out by the driver bit at the end of the screwdriver can be avoided. With the construction as set forth in claim 3, even when the screw-holding tape is suddenly pulled down by an external force, the auxiliary spring exerts a force in the direction opposite to the direction of the two-arm lever being pivotally moved by such an external force, and therefore, any sudden pivotal movement of the two-arm lever during stoppage of the device can be more surely prevented. The construction of the tape-pulling back mechanism as set forth in claim 4 enables the tape to be freely pulled back by an operation of a lever, and therefore, the tape can be replaced by a screw-holding tape with a different type of screws during operation as occasion demands. The construction of the screw holding mechanism as set forth in claim 5 has a wide range of angles of pivotal motion to guide the tape as compared with that in the prior art, and enables the tape to be smoothly fed. It is understood by those skilled in the art that the foregoing descriptions are preferred embodiments of the disclosed device and that various changes and modifications may be made in the invention without departing from the scope of the appended claims.

Claims: A screw-driving device which is adapted to be coupled to a screwdriver and continuously drive screws held in a screw-holding tape (7) in line one by one during a pressure stroke, which comprises a tubular casing (1) coupled to the forward end of said screwdriver; a slide member (2) slidably fitted for reciprocating movement in the casing (1); a return spring (5) for returning said slide member (2) to its initial extended position during a return stroke; and a mechanism provided in the slide member (2) for feeding the screw-holding tape (7) by one-step pitches, said tape-feeding mechanism including a guide slot (8) provided in the casing (1), a two-arm lever (9) having a pin (11, 12) fitted into the guide slot (8) at the end of one arm (9a) of the two-arm lever (9) and pivotably connected to said slide member (2), said two-arm lever (9) having at the end of the other arm (9b) thereof a pawl member (13) which is engageable in one of grooves or apertures at one lateral edge of the screw-holding tape (7) guided along a guide passage (18, 19) traversing the slide member (2), characterized in that said pawl member (13) is pivotably connected to said other arm (9b) and is biased by means of a spring (15) so that the pawl (13a) on the pawl member (13) is pivotably urged toward the screw-holding tape (7) and simultaneously, a further pawl member (21) with a further pawl (21a) is pivotably connected to the slide member (2) and engageable in one of further grooves (7a, 7b) or apertures (7a', 7b') of the screw-holding tape (7) by another spring (24), said pawls (13a, 21a) of the pawl members (13, 21) each having a first surface oriented in the feed direction of the screw-holding tape (7) and extending substantially perpendicular to the surface of the screw-holding tape (7) when the respective pawls (13a, 21a) engage in one of the grooves or apertures of the screw-holding tape (7), and a second surface oriented opposite the feed direction of the screw-holding tape and inclined so as to form an acute angle with the respective first surface. A screw-driving device as claimed in claim 1, wherein said guide slot (8) includes a short rectilinear section (8c) in front of said inclined section (8a) thereof extending continuously therewith in the longitudinal direction of said casing (1), whereby said pin (11, 12) at the end of one arm (9a) of said two-arm lever (9) is fitted into said short rectilinear section (8c) in the position of stoppage of the device where said slide member (2) is extended out of said casing (1) to the maximum by said return spring means (5). A screw-driving device as claimed in claim 1, further including an auxiliary spring means (34) for biasing said two-arm lever (9) in the direction opposite the direction of said two-arm lever (9) being pivotably moved when said pin (11, 12) at the end of one arm (9a) of said two-arm lever (9) is moved along said inclined section (8a) of said guide slot (8) during said pressure stroke. A screw-driving device as claimed in claim 1, further comprising a mechanism (26) provided in said slide member (2) for pulling back said screw-holding tape (7) in the direction opposite the tape-feeding direction, said tape pulling-back mechanism including projections (23, 25) extending toward each other and provided on both said pawl member (13) pivotably connected to said two-arm lever (9) and said further pawl member (21) pivotably connected to said slide member (2) at the ends of both said pawl members (13, 21) away from the pawls (13a, 21a) thereof, and a two-arm lever (26) pivotably connected to said slide member (2) and adapted to engage said opposite projections (23, 25) for pulling back said pawls (13a, 21a) of both pawl members (13, 21) in the direction away from the groove (7a, 7b) or aperture (7a', 7b') of the screw-holding tape (7). A screw-driving device as claimed in claim 1, further comprising a tape-holding means provided on the back portion of the side of said casing (1) at the side of said slide member (2) provided with a tape inserting opening, said tape bolding means including a mount secured to the back portion of said casing and a tape holding member pivotably supported by a pivotal shaft (41) secured to said mount in a manner parallel to the plane of said casing (1), said tape-holding member being supported on said pivotal shaft (41) so that the guide groove (43) thereof is inclined obliquely and upwardly toward the tape-inserting opening of said slide member (2).

Inventors: TAKAGI HARUO, TAKAGI, HARUO
Applicants: TOYO TECHNO CO LTD, TOYO TECHNO CO., LTD.
Application year: 1993
Main classification: B25B23
IPC codes: B25B23