GB2320905A - Screwdriver - Google Patents

Abstract

A screwdriver comprises a body 101 having a driver bit 103, a nose portion 102 movable in the axial direction of the driver bit, a coupled screw feed wheel 106 supported on a wheel rod 104, a feed wheel 119 located on one side of the coupled screw feed wheel 106 and a check pawl (130, Fig 5) located on the other side. The feed wheel only engages the coupled screw feed wheel when it rotates in the screw-feeding direction and the check pawl only engages retaining pawls (113, Fig 5) located on the wheel rod when the coupled screw feed wheel rotates opposite to the screw-feeding direction. The wheel rod is normally positioned so that the retaining pawls and check pawl are aligned but it is movable along its own axis so as to cause selective engagement/disengagement of the feed wheel and coupled screw feed wheel and selective alignment/misalignment of the pawls.

Description

SCREW TIGHTENER The present invention relates to a screw tightener for feeding and tightening coupled screws, and more particularly to a mechanism for feeding and reversely extracting screws.

There is a known screw tightener having a feed wheel supported by a nose portion which is relatively movable to the screw tightener body in order to feed coupled screws supplied to the nose portion by having the rotation of the feed wheel interlocked with the movement of the nose portion into the screw tightener body. Where a worker uses such a screw tightener to screw a face material on a prime material on the ceiling, he would hold one side of the face material with one hand and push up the other side thereof with the tip of the screw tightener held by the other hand.

Due to the load of the face material at this time, the nose portion may be forced slightly into the screw tightener body and allow the feed wheel to rotate according to a minute sign (the so-called "clap sign"), so that the screw is pushed out. If it is then attempted to drive in the screw at a predetermined position by separating the screw tightener from the face material, the feed wheel will rotate again when the nose portion is pressed against the face material, thus causing a new screw to be fed. For this reason, the screw initially fed may be wasted and the nose portion will be clogged with the two screws introduced into a narrow space.

Moreover, the screw will not sufficiently be driven in and the screw head will protrude from the face material if the indentation load applied to the nose portion is released before the screw is sufficiently driven in; consequently, it is required to tighten the screw again.

However, the forced-in movement of the nose portion allows the feed wheel to rotate and causes a new screw to be fed.

The screw thus needs tightening again after what has newly been fed is removed and there arise the problem of making troublesome the work of removing the screw that has already been fed and the problem of wasting screws.

Our co-pending case, GB-A-2,291,612, from which the present application is divided discloses and claims a screw tightener including a retaining means so that the feeding of two screws is prevented until the nose piece has been pushed into the body by a predetermined amount corresponding to the drive depth of the screw.

In a screw tightener of the sort mentioned above, there arises the necessity of reversely extracting screws that have been mounted once therein in such a case that the coupled screw needs replacing in the course of the screw-tightening operation, and a mechanism for reversely extracting coupled screws has been employed accordingly. As disclosed in Japanese Unexamined Patent Publication No.

100880/1990, a conventional mechanism for reversely extracting coupled screws has been contrived so as to reversely extract a screw by lowering an operative lever in a screw tightener.

However, the operative lever is known to have damaged a sheet of paper covering the surface of, for example, a plasterboard as a material to be screwed down because the lever projecting from the surface of the screw tightener may strike against the material. Moreover, such an operative lever has been disadvantageous in that it is inferior in not only operability but also design as it is left projecting from the screw tightener, thus giving an unfavourable impression.

According to the present invention, there is provided a screw tightener for tightening coupled screws comprising: a screw tightener body including a driver bit; a nose portion movable in the axial direction of said driver bit at the leading end of said screw tightener body fitted with said driver belt, said nose portion having a concave recess on an outer side thereof; a wheel rod fitted to said nose portion, the wheel rod movably in the axial direction of said wheel rod; a coupled screw feed wheel rotatably supported by said wheel rod; a feed wheel installed on one side of said coupled screw feed wheel and co-axially superposed on said coupled screw feed wheel only when said coupled screw feed wheel rotates in the direction in which the coupled screws are fed by the relative movement of said screw tightener and said nose portion; and a check pawl installed on the other side of said coupled screw feed wheel and capable of retaining one of the continuously formed pawls on the outer peripheral face of said wheel rod only when said coupled screw feed wheel rotates in the direction opposite to the direction in which the coupled screws are fed wherein said wheel rod whose one end is arranged so that it normally protrudes from said concave recess to make the pawls and the check pawl face each other, is placed at a position where said feed wheel is allowed to mate with said coupled screw feed wheel, and the pawl is shifted to a position where it will not correspond to the check pawl by pushing the one end of said wheel rod in the axial direction of said wheel rod, so that said feed wheel is moved to a position where said feed wheel and said coupled screw feed wheel are not allowed to mate with each other.

When the screws that have been mounted once are reversely extracted, the pawl of the wheel rod is moved to a position where it will not correspond to the check pawl by pushing one end of the wheel rod protruded from the concave recess on the outer side of the nose portion in the axial direction, and the feed wheel is simultaneously moved to the position where it does not mate with the coupled-screw feed wheel. Consequently, the coupled-screw feed wheel is set free from being rotated in the direction opposite to the feeding direction. While the coupled-screw feed wheel is reversely rotated, the coupled screw can be extracted in the direction opposite to the direction in which it has been fed.

When the wheel rod is moved to the original position, the pawl faces the check pawl again and returns to the position where the feed wheel mates with the coupled-screw feed wheel.

Examples of the present invention will now be described with reference to the accompanying drawings, in which: Fig. 1 is a top view of a mechanism for reversely extracting coupled screws in a screw tightener for coupled screws according to the present invention; Fig. 2 is a side view of the mechanism for reversely extracting coupled screws in a screw tightener for coupled screws according to the present invention; Fig. 3 is a diagram illustrating a mode in which the wheel rod is geared to operational requirements; Fig. 4 is a perspective view of the feed wheels; Figs. 5(a) and 5(b) show a diagram illustrating a mode in which the mating pawl and the mating groove are engaged and disengaged; Fig. 6 is a diagram illustrating a mode in which the check pawl is used to prevent reverse rotation; Fig. 7 is a top view illustrating the feeding of the screw; Fig. 8 is a side view at the time the mechanism for reversely extracting coupled screws is operated; Fig. 9 is a top view of a screw tightener according to the present invention; Fig. 10 is a diagram illustrating a mode in which a screw is driven in by the screw tightener according to the present invention; Figs. ll(a), ll(b) and ll(c) is respectively, an elevational, a top and a rear elevational view of a protective cover of the screw tightener; Fig. 12 is an enlarged sectional view taken on line X - X of Fig. ll(c); and Fig. 13 is a diagram illustrating a mode in which a screw is driven in a slanted material.

A screw tightener which includes a mechanism for reversely extracting coupled screw according to the present invention will be described below.

Figs. 1 and 2 show the front portion of a screw tightener, wherein reference numeral 101 denotes a screw tightener body and 102, a nose portion. The screw tightener body 101 is fitted with a driver bit 103 and a mechanism (not shown) for driving the driver bit 103 to rotate. The nose portion 102 is movable in the axial direction of the driver bit 103, and a feed wheel 106 for feeding coupled screws 105 upward from below is rotatably mounted on a wheel rod 104 supported with both left- and right-hand side parts.

The nose portion 102 is always urged by a spring 107 to move forward, that is, in the direction in which it moves away from the screw tightener body 101. A feed passageway 108 through which the coupled screws 105 are vertically fed is formed through the front part of the nose portion 102, and the coupled screws 105 are inserted into the feed passage 108 upwardly from below so as to be mounted therein.

The central part of the wheel rod 104 has a large diameter, whereas both end-parts thereof have a small diameter. A keyway 109 is formed at the end of one smalldiameter part 104a of the wheel rod 104. The other smalldiameter part 104b of the wheel rod 104 passes through the side of the nose portion 102 and projects from a concave recess 110 formed in its outer side part. As shown in Fig.

3, the end on the side of the keyway 109 is fitted into a bearing 111 on the side part of the nose portion 102, and the keyway 109 mates with a protruded channel 112.

Consequently, the wheel rod 104 is made movable in the axial direction, though it is not rotatable. Moreover, a rachet-like pawl 113 is circumferentially and continuously formed on one peripheral face of the large-diameter part 104c.

The feed wheel 106 is rotatably supported by the large-diameter part 104c of the wheel rod 104, and mating pawls 114 mating with a coupling belt 105a for the coupled screws 105 are formed on the outer peripheral faces on both sides of the feed wheel 106. Moreover, it has been arranged that the side face of the feed wheel 106 and a shoulder 115 between the large and small-diameter parts 104c, 104b of the wheel rod 104 are on the same plane. Further, a recess 116 is formed in the central part of one side face of the feed wheel 106, and a wheel plate 117 is secured to the recess.

As shown in Fig. 4, there are formed nine mating grooves 118 at equal intervals in the outer side face of the wheel plate 117. Each mating groove 118 is formed so that one end in the circumferential direction is right angled and the other end is sloped.

A discoid feed wheel 119 is superposed on one side face of the feed wheel 106. The feed wheel 119 is rotatably supported on the small-diameter part 104a at one end of the wheel rod 104, and normally urged by a spring 120 so as to be pressed against the shoulder 115 of the wheel rod 104.

Consequently, the feed wheel 119 is made to move away from the wheel plate 117 by moving the wheel rod 104 in the axial direction against the force of the spring 120.

As shown in Fig. 4, moreover, three mating pawls 121 corresponding to the mating grooves 118 of the wheel plate 117 are formed on the inner side face of the feed wheel 119. One circumferential end of the mating pawl 21 is right-angled and the other end is sloped as shown in Fig.

5(b) . Consequently, the mating pawls 121 mate with the mating grooves 118 of the wheel plate 117 and drive the wheel plate 117 (together with the feed wheel 106) as shown in Fig. 5(a) when the feed wheel 119 rotates in the direction in which the coupled screws 105 are fed. When, however, the feed wheel 119 reversely rotates, the mating pawls 21 are released from the mating grooves 118 of the wheel plate 117 as shown in Fig. 5(b).

Further, a mating hole 122 is bored in the feed wheel 119, and a feed rod 127 formed at one end of a feed plate 123 fits into the mating hole 122. The feed plate 123 is placed between the screw tightener body 101 and the nose portion 102. A roller 124 is pivotally fitted to the other end of the feed plate 123 and is movable along a first roller guide groove formed in the side part of the screw tightener body 101 and a second groove 126 formed in the side part of the nose portion 102. Subsequently, as shown in Figs. 1 and 6, a recess 128 is formed in the opposite side face of the feed wheel 106, and a support shaft 129 is provided in the recess 128, a check pawl 130 being rotatably fitted to the support shaft 129. The check pawl 130 is placed at a position corresponding to the pawls 113 of the wheel rod 104 and is urged by a spring 131 provided in the recess 128 to be retained by the pawls 113 of the wheel rod 104. The check pawl 130 is arranged so that only when the feed wheel 106 rotates in the direction opposite to the direction in which the coupled screws 105 are fed, it is retained by the pawl 113; when the wheel rod 104 is moved in the axial direction, however, the pawl 113 is moved to the position where it does not face the check pawl 130. In this case, a cover plate 132 for pressing down the check pawl 130 is superposed on the side face of the feed wheel 106.

With the arrangement above, normally the end part 104b of the wheel rod 104 is projected from the concave recess 110 formed in the outer side face of the nose portion 102, and the pawl 113 and the check pawl 130 face each other, the mating grooves 118 of the feed wheel 119 being kept mating with the mating pawls 121. When the screw tightener body 101 is pushed forward to press the front end of the nose portion 102 against a material to be screwed down during the screw-tightening operation, the nose portion 102 relatively moves back as shown in Fig. 9 and the movement of the feed plate 123 is interlocked with the relative movement of the nose portion 102 in that the roller 124 at one end of the feed plate 123 is guided along the second roller guide groove 126 of the nose portion 102 and the tilted short groove 125a of the first roller guide groove 125 of the screw tightener body 101. As the movement in the moving direction of the feed plate 123 is smaller than the movement of the nose portion 102, the feed rod 27 at the other end of the feed plate 23 presses the feed wheel 119 against the side opposite to the direction in which the nose portion 102 moves in such a state that the feed rod 127 is kept in the mating hole 122 of the feed wheel 119.

Consequently, the feed wheel 119 rotates at a constant angle of rotation in the direction in which the coupled screws 105 are fed. As the mating groove 118 of the feed wheel 119 has mated with the mating pawl 121 of the wheel plate 117, the wheel plate 117 also rotates only by the same quantity of rotation, whereby the feed wheel 106 simultaneously rotates by an angle of rotation corresponding to the feeding of one of the coupled screws 105 in the feeding direction. When the screw tightener body 101 is pushed forward further, the driver bit 103 mates with the screw thus fed and while rotating the screw, the driver bit 103 drives it into the material. Then the roller 124 of the feed plate 123 moves along the long groove part 125b of the roller guide groove.

When the screw tightener is separated from the screw on the termination of the screw-driving operation, the spring 107 allows the nose portion 102 to return to the original reset position, and the roller 124 of the feed plate 123 is finally moved along the second roller guide groove 126 of the nose portion 102 and the tilted short groove 125a of the first roller guide groove 125 of the screw tightener body 101. Since the movement of the roller 124 is smaller than that of the nose portion 102 in its moving direction, however, the feed rod 127 of the feed plate 123 is, as shown in Figs. 1 and 2, moved in the opposite direction this time, so that the feed wheel 119 reversely rotates in the direction opposite to the screw-feeding direction. On the other hand, the check pawl 130 is kept being retained by the pawl 113 of the wheel rod 104 and consequently the feed wheel 106 as well as the wheel plate 117 does not rotate reversely. The next screw-feeding is thus prepared.

In accordance with the screw-tightening operation in which the nose portion 102 is forced into the screw tightener body and put back, the feed wheel 106 intermittently revolves in the direction in which the coupled screws 105 are fed so as to feed the coupled screws 105 successively to the nose portion 102 one after another.

In a case where the screw 105 that has been mounted once is extracted, the wheel rod 104 projecting from the concave recess 110 is axially pushed against the force of the spring 120 as shown in Fig. 8. The pawl 113 then moves to the position where it does not face the check pawl 130, and the feed wheel 119 together with the wheel rod 104 simultaneously moves back to the position where it does not mate with the wheel plate 117 of the feed wheel 106. Thus the feed wheel 106 does not rotate in the feeding direction and what is opposite thereto. While the feed wheel 106 is kept rotating reversely, the screw 105 can be extracted in the direction opposite to the direction in which the coupled screws 105 are mounted therein (in the direction shown by an arrow A of Fig. 1).

When the force applied to the wheel rod 104 is released, the resilient force of the spring 120 causes the wheel rod 104 to return to the original position, thus making the pawl 113 face the check pawl 130. At the same time, the mating pawls 121 of the feed wheel 119 are reset to the position where they can mate with the respective grooves 118 of the wheel plate 117.

In the present invention, the rotation of the feed wheel released only by axially pushing the wheel rod so as to extract a screw reversely. The operation can thus be simplified.

While the pawls and the mating pawls are moved together with the wheel rod, the check pawl and the mating grooves formed on the feed wheel side makes it possible to engage and disengage the pawls and the check pawl, and to engage and disengage the mating grooves and mating pawls simultaneously only by moving the wheel rod in the axial direction. This mechanism is simple in construction, and therefore contributes to decreasing the number of parts and implementing an attempt to reduce the manufacturing cost.

Since the end part of the wheel rod projects from the concave recess in the outer side of the nose portion, it can be arranged without projecting from the side face of the nose portion. It is therefore possible to prevent effectively an unexpected accident resulting from allowing the wheel rod to bump against a material to be screwed down and so forth during the screw-tightening operation.

Moreover, the whole design will not be impaired as the end part of the wheel rod is only to project from the concave recess and therefore unobtrusive.

Fig. 12 shows to employ a screw tightener for tightening a screw 222 in a face material 221 having a slanted surface.

As shown in Fig. 12, part of a protective cover 220 is consequently caused to abut against the surface of the face material 221, and the screw tends to become turned insufficiently because of the large diameter of the screw 222. Hence there often arises nonconformity in that while one side of a screw head 222a sinks below the surface of the face material 221, the other side protrudes therefrom.

In actual operation, the frequency of driving screws slantwise is extremely high and besides cloth is usually stretched on the face material 221 to finish the work. The screw head 222a protruding from the surface of the face material 221 results in poor surface finish, which makes it necessary to tighten the screw 222 again, and this adds complication to the screw-driving operation.

A protective cover at the tip of a screw tightener is capable of tightening screws so as to prevent the protrusion of screw heads from a face material even when the screws are driven into the material slantwise is designated.

The protective cover applied to a screw tightener according to the invention described below.

In Fig. 9, reference numeral 201 denotes a screw tightener body; 202, a nose portion at the leading end of the screw tightener body 201; and 203, a driver bit. The screw tightener body 1, the nose portion 202 and the driver bit may be provided according to the embodiments described above.

A protective cover 205 is made of urethane resin and mounted at the front end of the nose portion 202. As shown in Figs. 11(a), 11(b), ll(c) and Fig. 12, a hole 206 for passing a screw and the driver bit 203 is made in the centre of the protective cover 205. Further, the protective cover 205 has a rear opening, and a recessed portion 207 therein which mates with the front end part 202b of the nose portion 202. A grooved opening 208 communicating with the hole 206 is formed in the lower part of the protective cover 205, whereas a grooved opening 209 is also formed on the upper base end side of the protective cover 205.

The front (tip) of the protective cover 205 has a spherical surface, which includes a non-slip arrangement in the form of a plurality of concentric circular grooved channels 210 around the top part 205a of the spherical surface. Both sidewalls 211 of the grooved channel 210 for the non-slip arrangement are formed so that they are parallel to the axis of the protective cover 205.

The protective cover 205 is mounted by fitting the front part 202b of the nose portion 2 into the recessed portion 207. At this time, the axis of the driver bit 203 conforms to the centre of the hole 206 of the protective cover 205.

The coupled screws 204 are prepared by coupling a number of screws 204b to a coupling belt 204a of synthetic resin or the like, and the coupled screw 204 is mounted so as to pass through the grooved through-hole 202a of the nose portion 202 upward from below. Then the forefront screw 204b is set so that it stays on the central axis of the driver bit 203 of the screw tightener body 201 and faces the hole 206 of the protective cover 205.

When the coupled screws 204 are mounted, the forefront screw 204b is passed through the grooved opening 208 on the lower side of the protective cover 5 before being set in position. In case the forefront screw 204b has been driven in unsatisfactorily, it will be discharged from the protective cover 205 through its upper grooved opening 209.

When the screw tightener thus constructed is used, the front of the protective cover 205 in the nose portion 202 is pressed against a face material 213a to push the nose portion 202 in. While rotating relatively, the driver bit 203 of the screw tightener body 201 moves forward and pushes out the screw 4b in the nose portion 202. The rotating screw 204b is then forced out and driven into the face material 213a. When the screw tightener is separated from the face material 213a after the screw-tightening operation is completed, the nose portion 202 is also separated from the screw tightener, and the driver bit 203 retracts. The relative movement of the nose portion 202 causes the screw feeding mechanism to operate, thus effecting the feeding of the coupled screws 204.

In a case where a screw is driven into a face material 213 slantwise, screw-driving operation is carried out likewise. Since the screw tightener is tilted as shown in Fig. 10 in this case, the region deflected from the centre of the protective cover 205 toward the tilted side is pressed against the face material 213. The spherical surface at the front of the protective cover 205 is not separated much from the face material 213 even when the screw tightener is tilted. Therefore, the screw 204b is sufficiently deeply driven into the face material 213 as shown in Fig. 10 and its head 212 is never protruded from the surface of the face material 213. The operation of additionally tightening the screw can thus be dispensed with.

Moreover, the non-slip arrangement on the outer face of the protective cover 205 prevents the protective cover 205 from slipping off the screw-driving position when the screw tightener is pressed against the face material 213 slantwise to ensure that owing to the absence of such nonconformity as slipping off the screw-driving position, reliable screwdriving work is carried out at all times.

Since both sidewalls of the grooved channel 210 for the non-slip arrangement are set parallel to the axis of the protective cover 205, one sidewall 211 of the grooved channel 210 abuts against the face material 213 at an acute angle as shown in Fig. 12. Consequently, resistance originating from the edge increases and this strengthens the non-slip effect further.

The grooved channels constituting the non-slip arrangement need not necessarily be concentric but may be formed spirally from the top part of the spherical surface of the protective cover.

In place of the aforementioned grooved channels, protruded channels may be formed on the outer face of the protective cover.

Claims (6)

1. A screw tightener for tightening coupled screws comprising: a screw tightener body including a driver bit; a nose portion movable in the axial direction of said driver bit at the leading end of said screw tightener body fitted with said driver belt, said nose portion having a concave recess on an outer side thereof; a wheel rod fitted to said nose portion, the wheel rod movably in the axial direction of said wheel rod; a coupled screw feed wheel rotatably supported by said wheel rod; a feed wheel installed on one side of said coupled screw feed wheel and co-axially superposed on said coupled screw feed wheel only when said coupled screw feed wheel rotates in the direction in which the coupled screws are fed by the relative movement of said screw tightener and said nose portion; and a check pawl installed on the other side of said coupled screw feed wheel and capable of retaining one of the continuously formed pawls on the outer peripheral face of said wheel rod only when said coupled screw feed wheel rotates in the direction opposite to the direction in which the coupled screws are fed wherein said wheel rod whose one end is arranged so that it normally protrudes from said concave recess to make the pawls and the check pawl face each other, is placed at a position where said feed wheel is allowed to mate with said coupled screw feed wheel, and the pawl is shifted to a position where it will not correspond to the check pawl by pushing the one end of said wheel rod in the axial direction of said wheel rod, so that said feed wheel is moved to a position where said feed wheel and said coupled screw feed wheel are not allowed to mate with each other.

2. A screw tightener according to claim 1, wherein said wheel rod has a length which does not project from the side face of said nose portion.

3. A screw tightener according to claim 1 or 2, further comprising a protective cover at the tip of said screw tightener, the front of said protective cover having a spherical surface including a plurality of concentric circular grooved channels around the top part of said spherical surface serving as a non-slip arrangement.

4. A screw tightener according to claim 1 or 2, further comprising a protective cover at the tip of said screw tightener, the front of said protective cover having a spherical surface including a spiral grooved channel extending from the top part of said spherical surface serving as a non-slip arrangement.

5. A screw tightener according to claim 1 or 2, further comprising a protective cover at the tip of said screw tightener, the front of said protective cover having a spherical surface including a plurality of concentric circular protruded channels serving as a non-slip arrangement.

6. A screw tightener substantially as shown in and described with reference to the accompanying drawings.