Screw fastening machine

Abstract

To make it possible to suppress operation of a force greater than usual to a zipper.SOLUTION: A screw fastening machine includes: a body having a guide hole guiding a supplied screw; a zipper supported by the body, supplied with a screw from the guide hole, and whose end part opens / closes around a supporting point of the body; an energization member imparting an energizing force in a closing direction where an end of the zipper closes; and a fastening rod which push-sends the screw in an end direction of the zipper while opening the closed zipper and capable of forming the state that the screw head is held at the end part of the zipper. The energization member has a first energization member and a second energization member. In an area where an angle of aperture of the zipper opening as the push-sent screw moves is a prescribed angle or smaller, only the first energization member energizes the zipper in the closing direction; in an area where the angle of aperture is beyond the prescribed angle, the first energization member and the second energization member energize the zipper in the closing direction.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a screw fastener. [Background technology]

[0002] Patent Document 1 discloses a bolt tightening machine. The bolt tightening mechanism includes a chuck that clamps the bolt to be tightened. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-113171 Summary of the Invention [Problem to be solved by the invention]

[0004] In the bolt tightening machine of Patent Document 1, the supplied bolt may be clamped in a fallen state by the chuck. In this state, when the socket tries to push the bolt out of the chuck, stress is concentrated on the chuck, and a force greater than normal acts on the chuck.

[0005] The present invention has been made in consideration of the above-mentioned problems, and has an object to make it possible to prevent a force greater than normal from acting on a chuck. [Means for solving the problem]

[0006] According to one aspect of the present invention, there is provided a screw fastening tool comprising: a main body having a guide hole that guides a supplied screw; a chuck that is supported by the main body, into which the screw is supplied through the guide hole, and whose tip opens and closes around a support point with respect to the main body; a biasing member that applies a biasing force in a closing direction that closes the tip of the chuck; and a fastening rod that pushes the screw toward the tip of the chuck while opening the chuck in a closed state, and is capable of forming a state in which the head of the screw is held in the tip of the chuck, wherein the biasing member has a first biasing member and a second biasing member, and in a region where an opening angle of the chuck that opens as the screw being pushed forward is equal to or smaller than a predetermined angle, only the first biasing member biases the chuck in the closing direction, and in a region where the opening angle exceeds the predetermined angle, both the first biasing member and the second biasing member bias the chuck in the closing direction. [Effects of the Invention]

[0007] According to one aspect of the present invention, when the opening angle of the chuck is equal to or smaller than a predetermined angle, only the first biasing member biases the chuck in the closing direction, and when the opening angle exceeds the predetermined angle, both the first biasing member and the second biasing member bias the chuck in the closing direction. As a result, the biasing force applied to the chuck in the closing direction is greater when the opening angle exceeds the predetermined angle than when the opening angle is equal to or smaller than the predetermined angle.

[0008] Therefore, even if the screw inserted into the chuck is tilted, the strong biasing force of the first biasing member and the second biasing member biases the chuck in the closing direction, preventing the chuck from opening beyond a predetermined angle and preventing the screw from tipping over inside the chuck.

[0009] On the other hand, when the clamping rod pushes out a screw that has fallen over inside the chuck, the force applied from the clamping rod is input to the chuck via the screw, and the chuck, which is biased by the first and second biasing members, opens beyond the predetermined angle, so that the fallen screw is pushed out from the chuck.

[0010] Therefore, the screw tightening machine can suppress the tilting of the screw inserted into the chuck under normal circumstances, while widening the movable range of the chuck so that the fallen screw can be pushed out in the event of an abnormal situation in which the screw falls over.

[0011] Therefore, the screw tightening machine can perform normal operation to prevent the inserted screw from tilting, while also preventing a force greater than normal from acting on the chuck even in an abnormal situation where the screw has fallen over. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a cross-sectional view showing a screw fastener according to this embodiment. [Figure 2] FIG. 2 is a cross-sectional view of the tip of the chuck showing a state in which the screw is clamped by the chuck in a fallen state. [Figure 3] FIG. 3 is a cross-sectional view showing the base end of the grip portion. [Figure 4] FIG. 4 is a cross-sectional view of the tip of the chuck showing the chuck in an open state. DETAILED DESCRIPTION OF THE INVENTION

[0013] A screw fastener 10 according to an embodiment of the present invention will now be described with reference to the accompanying drawings.

[0014] Fig. 1 is a cross-sectional view showing a screw fastening tool 10 according to this embodiment. Fig. 2 is a cross-sectional view of the tip of the chuck 24 showing a state in which a screw 12 is clamped by the chuck 24 in a fallen state. Fig. 3 is a cross-sectional view showing the base end of the gripping portions (50, 52), and shows the base end of one gripping portion 50 as an example of the gripping portions (50, 52). Fig. 4 is a cross-sectional view of the tip of the chuck 24 showing the chuck 24 in an open state.

[0015] 1 and 2, the screw fastening machine 10 is a device that threads and fastens a screw 12 into a target location. The screw fastening machine 10 is used, for example, in an assembly device (not shown) that assembles a workpiece by fastening the screw 12 into a threaded hole in the workpiece. The main body 22 of the screw fastening machine 10 is attached to a mounting hole 42 of a slide plate 40 that moves back and forth between the workpiece and a screw supply device provided in the assembly device, for example.

[0016] The screw 12 is composed of a bolt having a head 14 and a threaded portion 16 that extends from the head 14 and has a smaller diameter than the head 14. The head 14 is formed in a cylindrical shape. A hexagonal hole 18, for example, having a hexagonal shape, is formed in a top surface 14A of the head 14.

[0017] In this embodiment, the screw 12 is described as a bolt, but the screw 12 is not limited to a bolt. The screw 12 may be, for example, a wood screw that is screwed into a target location and tightened.

[0018] In addition, in this embodiment, the screw 12 having a hexagonal hole 18 formed in the head 14 is described as an example, but this embodiment is not limited to this configuration. The screw 12 may also be a screw 12 having a "-" or "+" groove formed in the head 14. In addition, the shape of the head 14 of the screw 12 is not limited to a cylindrical shape, and may be, for example, a hexagonal column shape.

[0019] The screw fastening tool 10 includes a main body 22 having a guide hole 20 that guides the supplied screw 12. The screw fastening tool 10 is supported by the main body 22, and includes a chuck 24 into which the screw 12 is supplied through the guide hole 20 and whose tip opens and closes around a support point (66, 106) with the main body 22. The screw fastening tool 10 includes a biasing member (72, 112, 214, 264) that applies a biasing force in a closing direction that closes the tip of the chuck 24. The screw fastening tool 10 includes a clamping rod 26 that can push the screw 12 toward the tip of the chuck 24 while opening the chuck 24 in a closed state, thereby holding the head 14 of the screw 12 in place at the tip of the chuck 24.

[0020] (Main body) The main body 22 has a cylindrical portion 30 that surrounds the guide hole 20, and one-side support portions 32 and other-side support portions 34 that support the chuck 24. The tip of the cylindrical portion 30 extends further toward the tip side than the one-side support portion 32 and the other-side support portion 34. The one-side support portion 32 extends further toward one side than the cylindrical portion 30. The other-side support portion 34 extends further toward the other side than the cylindrical portion 30.

[0021] A base portion 36 that protrudes laterally is provided at the base end of the main body 22. A one-side extending piece 37 extends from the base portion 36, extending along the tubular portion 30 on the one-side support portion 32 side. In addition, a other-side extending piece 38 extends from the base portion 36, extending along the tubular portion 30 on the other-side support portion 34 side.

[0022] The guide hole 20 penetrates the main body 22 from the base end to the tip. A supply portion 46 having a larger diameter than the guide hole 20 is formed at the base end of the guide hole 20. The supply portion 46 forms a supply port for the screw 12. The guide hole 20 guides the screw 12 supplied from the supply portion 46 toward the tip side.

[0023] (Zipper) The chuck 24 is configured to include a one-side gripping portion 50 and an other-side gripping portion 52 that are arranged to sandwich the tubular portion 30 having the guide hole 20. As a result, the chuck 24 is supported by the main body 22 and has a plurality of gripping portions (50, 52) that can grip the head 14 of the screw 12.

[0024] In this embodiment, the chuck 24 is described as being composed of a pair of one-side gripping portion 50 and the other-side gripping portion 52, but the chuck 24 is not limited to this configuration. The chuck 24 may be composed of, for example, three or more gripping portions.

[0025] (One side grip part) The one-side grip portion 50 has a one-side lever portion 60 extending along the tubular portion 30 and a one-side holding portion 62 provided at the tip of the one-side lever portion 60.

[0026] The one-side lever portion 60 has a central portion in the longitudinal direction supported by the one-side support portion 32 of the main body 22 by the one-side shaft portion 64. This allows the one-side grip portion 50 to tilt around the one-side support point 66, which is the center of the one-side support portion 32.

[0027] The one-side lever portion 60 has a one-side opposing surface 60A that faces the tubular portion side surface 30A, which is closer to the base portion 36 of the main body 22 than the one-side support point 66. The one-side opposing surface 60A inclines in a direction away from the tubular portion side surface 30A as it moves from the one-side support point 66 toward the base end. This allows the one-side lever portion 60 to incline around the one-side support point 66 until the one-side opposing surface 60A comes into contact with the tubular portion side surface 30A.

[0028] (One-side first biasing member) The one-side lever portion 60 has a one-side spring hole 70 at the base end portion on the base portion 36 side of the main body 22. A one-side first biasing member 72 made of a coil spring is housed in the one-side spring hole 70. The one-side first biasing member 72 constitutes one of a pair of first biasing members (72, 112).

[0029] (One-side second biasing member) A bottomed one-side mounting hole 200 that opens toward the one-side lever portion 60 is formed in the portion of the one-side extension piece 37 that faces the one-side outer surface 60B of the one-side lever portion 60. The one-side mounting hole 200 slopes from the bottom toward the opening toward the tip of the screw fastener 10.

[0030] A first-side ball plunger 210 is attached to the first-side mounting hole 200. For example, when a first-side ball plunger 210 having a male thread formed on its outer circumferential surface is used, a female thread is formed on the inner circumferential surface of the first-side mounting hole 200. Then, the first-side ball plunger 210 is attached to the first-side mounting hole 200 by being screwed into the first-side mounting hole 200.

[0031] The one-side ball plunger 210 comprises a one-side casing 212 formed in a cylindrical shape with a bottom, a one-side second biasing member 214 composed of a coil spring inside the one-side casing 212, and a spherical one-side ball member 216 biased by the one-side second biasing member 214.

[0032] The one-side ball member 216 is biased in the protruding direction. The one-side ball member 216 can abut against a portion of the one-side outer surface 60B of the one-side lever portion 60 that is closer to the tip end than the one-side support point 66, and the one-side second biasing member 214 applies a biasing force to the chuck 24 via the one-side ball member 216. In addition, the one-side ball member 216 can retract into the one-side casing 212, allowing the one-side lever portion 60 to tilt.

[0033] When the chuck 24 is in the closed state, the one-side ball member 216 of the one-side ball plunger 210 is separated from the one-side outer surface 60B of the one-side lever portion 60 of the one-side grip portion 50. The one-side ball member 216 of the one-side ball plunger 210 comes into contact with the one-side outer surface 60B of the one-side lever portion 60 of the one-side grip portion 50 at an opening angle in which the head 14 of the screw 12 is held by the tip portion of the chuck 24.

[0034] When the chuck 24 is further opened from the state in which the one-side ball member 216 of the one-side ball plunger 210 is in contact with the one-side outer surface 60B of the one-side lever portion 60, the one-side ball member 216 of the one-side ball plunger 210 moves backward while rolling along the one-side outer surface 60B of the one-side lever portion 60. The one-side ball member 216 of the one-side ball plunger 210 moves backward to an opening angle at which the screw 12 that has fallen inside the chuck 24 can be pushed out of the chuck 24 by the tightening rod 26.

[0035] The one-side lever portion 60 has a one-side screw hole 76 at its tip. A one-side setscrew 78 is threaded into the one-side screw hole 76, and the amount by which the one-side setscrew 78 protrudes from the one-side lever portion 60 can be adjusted. This allows the one-side lever portion 60 to tilt around the one-side support point 66 as the center until the one-side setscrew 78 comes into contact with the cylindrical portion side surface 30A and reaches a closed state.

[0036] (One side holding part) The outer surface of the one-side holding portion 62 is inclined toward the central axis C of the screw fastener 10 as it approaches the tip. The inner surface of the one-side holding portion 62 is configured as an elliptical arc-shaped curved surface.

[0037] The inner surface of the one-side retaining portion 62 has an arc-shaped one-side surrounding surface 80 that faces the tubular portion 30 of the main body 22 and suppresses interference with the tubular portion 30, and a one-side step portion 82 that extends from the one-side surrounding surface 80 and extends along the end face of the tubular portion 30 in the closed state.

[0038] The inner surface of the one-side holding portion 62 has a one-side guide surface 84 that is inclined toward the central axis C from the one-side step portion 82 toward the tip side, and a one-side arcuate surface 86 that extends toward the tip side from the one-side guide surface 84. The inner surface of the one-side holding portion 62 also has a one-side inclined surface 88 that is inclined toward the central axis C from the one-side arcuate surface 86 toward the tip side.

[0039] (Other side gripping part) The other-side grip portion 52 has a other-side lever portion 100 extending along the tubular portion 30 and a other-side holding portion 102 provided at the tip of the other-side lever portion 100.

[0040] The other-side lever portion 100 has a central portion in the longitudinal direction supported by the other-side support portion 34 of the main body 22 via an other-side shaft portion 104. The other-side grip portion 52 is tiltable around an other-side support point 106, which is the center of the other-side shaft portion 104.

[0041] The other-side lever portion 100 has a other-side opposing surface 100A that faces the tubular portion side surface 30A and is located closer to the base portion 36 of the main body 22 than the other-side support point 106. The other-side opposing surface 100A inclines in a direction away from the tubular portion side surface 30A as it extends from the other-side support point 106 toward the base end. This allows the other-side lever portion 100 to incline around the other-side support point 106 until the other-side opposing surface 100A comes into contact with the tubular portion side surface 30A.

[0042] (Other-side first biasing member) The other-side lever portion 100 has a other-side spring hole 110 at the base end portion on the base portion 36 side of the main body 22. A other-side first biasing member 112 made of a coil spring is housed in the other-side spring hole 110. The other-side first biasing member 112 constitutes the other of the pair of first biasing members (72, 112).

[0043] (Other-side second biasing member) A bottomed other-side mounting hole 250 that opens toward the other-side lever portion 100 is formed in the portion of the other-side extension piece 38 that faces the other-side outer surface 100B of the other-side lever portion 100. The other-side mounting hole 250 is inclined toward the tip of the screw fastener 10 as it extends from the bottom toward the opening.

[0044] A second-side ball plunger 260 is attached to the second-side mounting hole 250. For example, when a second-side ball plunger 260 having a male thread formed on its outer circumferential surface is used, a female thread is formed on the inner circumferential surface of the second-side mounting hole 250. Then, the second-side ball plunger 260 is attached to the second-side mounting hole 250 by being screwed into the second-side mounting hole 250.

[0045] The other-side ball plunger 260 comprises a other-side casing 262 formed in a cylindrical shape with a bottom, a second other-side biasing member 264 composed of a coil spring inside the other-side casing 262, and a spherical other-side ball member 266 biased by the second other-side biasing member 264.

[0046] The other-side ball member 266 is biased in the protruding direction. The other-side ball member 266 can abut against a portion of the other-side outer surface 100B of the other-side lever portion 100 that is closer to the tip end than the other-side support point 106, and the other-side second biasing member 264 applies a biasing force to the chuck 24 via the other-side ball member 266. In addition, the other-side ball member 266 can retract into the other-side casing 262, allowing the other-side lever portion 100 to tilt.

[0047] When the chuck 24 is in the closed state, the other-side ball member 266 of the other-side ball plunger 260 moves away from the other-side outer surface 100B of the other-side lever portion 100 of the other-side gripping portion 52. The other-side ball member 266 of the other-side ball plunger 260 comes into contact with the other-side outer surface 100B of the other-side lever portion 100 of the other-side gripping portion 52 at an opening angle in which the head 14 of the screw 12 is held by the tip portion of the chuck 24.

[0048] When the chuck 24 is further opened from the state in which the other-side ball member 266 of the other-side ball plunger 260 is in contact with the other-side outer surface 100B of the other-side lever portion 100, the other-side ball member 266 of the other-side ball plunger 260 moves backward while rolling along the other-side outer surface 100B of the other-side lever portion 100. The other-side ball member 266 of the other-side ball plunger 260 moves backward to an opening angle at which the screw 12 that has fallen inside the chuck 24 can be pushed out of the chuck 24 by the tightening rod 26.

[0049] The other-side lever portion 100 has an other-side screw hole 116 at its tip. An other-side setscrew 118 is threaded into the other-side screw hole 116, and the amount of protrusion of the other-side setscrew 118 from the other-side lever portion 100 can be adjusted. This allows the other-side lever portion 100 to tilt around the other-side support point 106 to a closed state in which the other-side setscrew 118 contacts the tubular portion side surface 30A.

[0050] In this embodiment, both the one-side gripping portion 50 and the other-side gripping portion 52 that make up the chuck 24 are configured to be tiltable, but the chuck 24 is not limited to this configuration. For example, the chuck 24 may be configured so that one of the one-side gripping portion 50 and the other-side gripping portion 52 is fixed and the other is tiltable.

[0051] (Other side holding part) The outer surface of the other-side holding portion 102 is inclined toward the central axis C of the screw fastener 10 as it approaches the tip. The inner surface of the other-side holding portion 102 is configured as an elliptical arc-shaped curved surface.

[0052] The inner surface of the other side holding portion 102 has an arc-shaped other side surrounding surface 120 that faces the tubular portion 30 of the main body 22 and suppresses interference with the tubular portion 30, and an other side step portion 122 that extends from the other side surrounding surface 120 and extends along the end face of the tubular portion 30 when closed.

[0053] The inner surface of the other-side holding portion 102 has an other-side guide surface 124 that is inclined toward the central axis C from the other-side step portion 122 toward the tip side, and an other-side arcuate surface 126 that extends toward the tip side from the other-side guide surface 124. The inner surface of the other-side holding portion 102 also has an other-side inclined surface 128 that is inclined toward the central axis C from the other-side arcuate surface 126 toward the tip side.

[0054] (Opening and closing operation) The one-side holding portion 62 of the one-side holding portion 50 and the other-side holding portion 102 of the other-side holding portion 52 constitute the tip of the chuck 24 that can hold the head 14 of the screw 12. The one-side holding portion 50 tilts about the one-side support point 66 and the other-side holding portion 52 tilts about the other-side support point 106, thereby opening and closing the tip of the chuck 24.

[0055] The gripping portions 50, 52 of the chuck 24 are biased by the first biasing members 72, 112, and form a closed state in which the gripping portions 50, 52 are tilted until the setscrews 78, 118 contact the cylindrical side surface 30A.

[0056] The chuck 24 also forms an open state in which the gripping portions 50, 52 are inclined until the tip ends of the inclined surfaces 88, 128 of the holding portions 62, 102 reach an opening angle that holds the head 14 of the screw 12 (see FIG. 1).

[0057] Furthermore, the chuck 24 is in a fully open state in which the gripping portions 50, 52 are tilted until the opposing surfaces 60A, 100A of the lever portions 60, 100 contact the cylindrical side surface 30A (see FIG. 2).

[0058] As shown in Fig. 3, in the screw fastening tool 10, the opposing surfaces 60A (100A) of the lever portions 60 (100) of the gripping portions 50 (52) constituting the chuck 24 are inclined at an inclination angle α with respect to the inner surfaces 60C (100C) of the lever portions 60 (100). Note that Fig. 3 shows only one gripping portion 50 as an example of a gripping portion.

[0059] As shown in Figures 2 to 4, the inclination angle α is set so that in the fully open state where each opposing surface 60A (100A) is in contact with the cylindrical side surface 30A (see Figures 2 and 4), the separation distance D between each inclined surface 88 (128) is longer than the longest distance L over which the horizontal length of the screw 12 that has fallen inside the chuck 24 is longest (see Figure 4).

[0060] (biasing member) 1, the one-side first biasing member 72 as a first biasing member is disposed in a compressed state between the end face of the one-side spring hole 70 of the one-side gripping portion 50 and the tubular portion side surface 30A of the main body 22. The one-side first biasing member 72 biases the one-side gripping portion 50 of the chuck 24 so that the one-side opposing surface 60A of the one-side lever portion 60 moves away from the tubular portion side surface 30A.

[0061] The other-side first biasing member 112 constituting the first biasing member is arranged in a compressed state between the end face of the other-side spring hole 110 of the other-side gripping portion 52 and the cylindrical portion side surface 30A of the main body 22. The other-side first biasing member 112 biases the other-side gripping portion 52 of the chuck 24 so that the other-side opposing surface 100A of the other-side lever portion 100 moves away from the cylindrical portion side surface 30A.

[0062] As a result, the one-side first biasing member 72 and the other-side first biasing member 112 that constitute the biasing member apply a biasing force in the closing direction so that the tip of the chuck 24, which is composed of the one-side holding portion 62 of the one-side gripping portion 50 and the other-side holding portion 102 of the other-side gripping portion 52, closes.

[0063] The one-side second biasing member 214 as a second biasing member is disposed between the bottom surface of the one-side casing 212 of the one-side ball plunger 210 provided on the one-side extension piece 37 of the main body 22 and the one-side outer surface 60B of the one-side grip portion 50. The one-side second biasing member 214 can bias the one-side outer surface 60B of the one-side lever portion 60 via the one-side ball member 216 of the one-side ball plunger 210.

[0064] The other-side second biasing member 264 as a second biasing member is disposed between the bottom surface of the other-side casing 262 of the other-side ball plunger 260 provided on the other-side extending piece 38 of the main body 22 and the other-side outer surface 100B of the other-side grip portion 52. The other-side second biasing member 264 can bias the other-side outer surface 100B of the other-side lever portion 100 via the other-side ball member 266 of the other-side ball plunger 260.

[0065] The one-side second biasing member 214 and the other-side second biasing member 264 that constitute the second biasing member apply a biasing force to the chuck 24 in the closing direction so that the tip of the chuck 24 closes, when each ball member 216, 266 abuts against each outer surface 60B, 100B of each lever portion 60, 100.

[0066] In a region where the opening angle of the chuck 24, which opens in response to the movement of the screw 12 pushed forward by the tightening rod 26, is equal to or smaller than a predetermined angle, only the first biasing members 72, 112 bias the chuck 24 in the closing direction. In a region where the opening angle exceeds the predetermined angle, the first biasing members 72, 112 and the second biasing members 214, 264 bias the chuck 24 in the closing direction (see, for example, FIG. 2).

[0067] Here, the predetermined angle is the opening angle when the head 14 of the screw 12 is held at the tip of the chuck 24 (see FIG. 1).

[0068] In this embodiment, the opening angle when the head 14 of the screw 12 is held by the tip of the chuck 24 is set to a predetermined angle, but the predetermined angle is not limited to this angle.

[0069] The specified angle may be, for example, an opening angle smaller than the opening angle of the chuck 24 holding the head 14 of the screw 12 at its tip. In this case, it is possible to increase the closing force before the head 14 of the screw 12 is held at the tip of the chuck 24.

[0070] The one-side first biasing member 72 and the other-side first biasing member 112 have approximately the same spring constant. The one-side second biasing member 214 and the other-side second biasing member 264 have approximately the same spring constant. The spring constant of each second biasing member 214, 264 is greater than the spring constant of each first biasing member 72, 112, and the biasing force of each second biasing member 214, 264 is greater than the biasing force of each first biasing member 72, 112.

[0071] (Tightening rod) The clamping rod 26 extends from a drive device (not shown) that is provided, for example, above the workpiece setting position of the assembly device. The drive device includes a rotation mechanism that rotates the clamping rod 26 and an elevator that raises and lowers the clamping rod 26 together with the rotation mechanism.

[0072] The fastening rod 26 has an engagement structure in which its tip engages with the head 14 of the screw 12. In this embodiment, which uses a screw 12 having a hexagonal hole 18 in its head 14, the fastening rod 26 is formed in the shape of a hexagonal column that can fit into the hexagonal hole 18 in the head 14 of the screw 12. The fastening rod 26 rotates and lowers the screw 12 engaged at its tip, thereby threading the screw 12 into the threaded hole in the workpiece and tightening it.

[0073] (Operation description) When the screw fastening tool 10 is used to fasten the screws 12 to the workpiece, the screw feeder of the assembly device feeds the screws 12 from the feeder 46 of the screw fastening tool 10 set on the slide plate 40 into the guide hole 20. The screws 12 are then guided along the guide hole 20 into the chuck 24.

[0074] The head 14 of the screw 12 guided into the chuck 24 is guided to the center of the chuck 24 along the guide surfaces 84, 124 of the gripping portions 50, 52 that constitute the chuck 24. As a result, the screw 12 is temporarily held in the chuck 24 with the head 14 housed inside the arcuate surfaces 86, 126 of the holding portions 62, 102 (not shown).

[0075] In this state, the assembly device slides the slide plate 40 to move the screw fastening tool 10 above the target location of the workpiece.

[0076] The assembly device also uses the drive unit to rotate and lower the fastening rod 26, inserting the fastening rod 26 into the guide hole 20. Then, the tip of the fastening rod 26 engages with the head 14 of the screw 12 while being inserted into the hexagonal hole 18 of the head 14 of the screw 12.

[0077] The driving device then further lowers the fastening rod 26, causing the lower edge of the head 14 of the screw 12 to abut against the inclined surfaces 88, 128, spreading apart the holding portions 62, 102. As a result, the holding portions 62, 102 tilt about the support points 66, 106, and the chuck 24 operates in the opening direction, opening the tip portions.

[0078] Then, when the head 14 reaches the tip of each inclined surface 88, 128 of each holding portion 62, 102, the screw 12 is held at the tip of the chuck 24 with the outer surface 14B of the head 14 being clamped from the side by each inclined surface 88, 128.

[0079] In this state, the threaded portion 16 of the screw 12 is aligned with the threaded hole of the target location, and then screwed into the threaded hole and tightened into the target location.

[0080] (Action and effect) The main functions and effects of the screw fastening device 10 configured as above will now be described.

[0081] (1) The screw fastening tool 10 includes a main body 22 having a guide hole 20 that guides the supplied screw 12. The screw fastening tool 10 is supported by the main body 22, and the screw 12 is supplied through the guide hole 20. The screw fastening tool 10 includes a chuck 24 whose tip opens and closes around a support point (66, 106) with the main body 22. The screw fastening tool 10 includes a biasing member (72, 112, 214, 264) that applies a biasing force in a closing direction that closes the tip of the chuck 24. The screw fastening tool 10 includes a clamping rod 26 that can push the screw 12 toward the tip of the chuck 24 while opening the chuck 24 in a closed state, thereby holding the head 14 of the screw 12 in place at the tip of the chuck 24. The biasing member (72, 112, 214, 264) has a first biasing member (72, 112) and a second biasing member (214, 264). In a region where the opening angle of the chuck 24, which opens in response to the movement of the screw 12 being pushed forward, is equal to or smaller than a predetermined angle, only the first biasing member (72, 112) biases the chuck 24 in the closing direction. In a region where the opening angle exceeds the predetermined angle, the first biasing member (72, 112) and the second biasing member (214, 264) bias the chuck 24 in the closing direction.

[0082] According to this embodiment, in a region where the opening angle of the chuck 24 is equal to or smaller than a predetermined angle, only the first biasing member (72, 112) biases the chuck 24 in the closing direction. In a region where the opening angle exceeds the predetermined angle, the first biasing member (72, 112) and the second biasing member (214, 264) bias the chuck 24 in the closing direction. As a result, the biasing force applied to the chuck 24 in the closing direction is greater in a region where the opening angle exceeds the predetermined angle than in a region where the opening angle is equal to or smaller than the predetermined angle.

[0083] Therefore, even if the screw 12 inserted into the chuck 24 is tilted, the screw fastening device 10 can urge the chuck 24 in the closing direction by a strong urging force obtained by adding the urging force of the second urging member (214, 264) to the urging force of the first urging member (72, 112). As a result, the screw fastening device 10 prevents the chuck 24 from opening beyond a predetermined angle, and prevents the screw 12 from tipping over inside the chuck 24.

[0084] On the other hand, when the tightening rod 26 pushes out the screw 12 that has fallen inside the chuck 24, the force applied from the tightening rod 26 is input to the chuck 24 via the screw 12. As a result, the chuck 24, which is biased by the first biasing member (72, 112) and the second biasing member (214, 264), opens beyond the predetermined angle, and the fallen screw 12 is pushed out from the chuck 24.

[0085] Therefore, the screw tightening device 10 can suppress the inclination of the screw 12 inserted into the chuck 24 under normal circumstances, while widening the movable range of the chuck 24 so that the fallen screw 12 can be pushed out in the abnormal event that the screw 12 falls.

[0086] Therefore, the screw tightening machine 10 can perform normal operation to suppress the tilt of the inserted screw 12, while also suppressing the application of a force greater than normal to the chuck 24 even in an abnormal situation where the screw 12 falls over.

[0087] This reduces the need to replace the chuck 24, which has received a force greater than normal, and the need to stop the line due to the replacement work, thereby improving production efficiency.

[0088] If a single biasing member with a small biasing force is used to bias the fallen screw 12 over the entire range up to the opening angle at which it can be pushed out, it becomes difficult to correct the inclination of the inserted screw 12. In addition, the tip of the chuck 24 cannot hold the head 14 of the screw 12, and there is a risk that the screw 12 will fall off.

[0089] On the other hand, if a single biasing member with a large biasing force is used to bias the fallen screw 12 over the entire range up to the opening angle at which it can be pushed out, the frictional resistance between the screw 12 and the chuck 24 that contacts the screw 12 will increase. This means that it is necessary to increase the force that pushes out the screw 12 from the chuck 24 and the rotational force that rotates the screw 12, which results in an increase in the size of the drive device.

[0090] In contrast to this, the screw fastening tool 10 of this embodiment has a function for correcting the inclination of the inserted screw 12, and also allows the drive device that rotates and raises and lowers the fastening rod 26 to be made smaller.

[0091] (2) In the screw fastening tool 10, the predetermined angle is the opening angle when the head 14 of the screw 12 is held at the tip of the chuck 24.

[0092] In this embodiment, when the opening angle of the chuck 24 becomes larger than the opening angle when the head 14 of the screw 12 is held at the tip of the chuck 24, the force urging the chuck 24 in the closing direction becomes larger.

[0093] Therefore, compared to when the force in the closing direction is greater at an opening angle greater than the opening angle at which the head 14 of the screw 12 is held in the chuck 24, it is possible to improve the effect of suppressing tilting of the inserted screw 12 and preventing the screw 12 from falling.

[0094] In addition, compared to when the force in the closing direction is large at an opening angle smaller than the opening angle at which the head 14 of the screw 12 is held in the chuck 24, it is possible to reduce the frictional resistance that occurs when the screw 12 is fed out of the chuck 24 during tightening.

[0095] (3) In the screw fastener 10, the second biasing members (214, 264) apply a biasing force to the chuck 24 via the ball members (216, 266).

[0096] In this embodiment, frictional resistance occurring between the chuck 24 and the ball members (216, 266) in contact with the chuck 24 is suppressed, thereby enabling the chuck 24 to perform smooth opening and closing operations.

[0097] (4) In the screw fastener 10, the biasing force of the second biasing member (214, 264) is greater than the biasing force of the first biasing member (72, 112).

[0098] In this embodiment, the change in the closing force that occurs when the opening angle of the chuck 24 exceeds a predetermined angle increases. This allows the screw fastening tool 10 to improve the effect of preventing the screw 12 inserted into the chuck 24 from falling over.

[0099] (5) In the screw fastening tool 10, the chuck 24 has a plurality of gripping portions (50, 52) supported by the main body 22 and capable of gripping the head 14 of the screw 12. The biasing members (72, 112, 214, 264) have first biasing members (72, 112) and second biasing members (214, 264) disposed between the main body 22 and each of the gripping portions (50, 52).

[0100] In this embodiment, the screw 12 can be held in a clamped state by a plurality of gripping portions (50, 52) and first biasing members (72, 112) and second biasing members (214, 264) arranged between each gripping portion (50, 52).

[0101] This makes it possible to hold the screw 12 at the center position to be tightened, thereby making it possible to prevent tightening errors.

[0102] Although the embodiments of the present invention have been described above, the above embodiments merely illustrate some of the application examples of the present invention, and it is not intended that the technical scope of the present invention be limited to the specific configurations of the above embodiments.

[0103] In the above embodiment, the screw fastening device 10 is described as being used in an assembly device, but the method of using the screw fastening device 10 is not limited to this. For example, the screw fastening device 10 may be used alone. [Explanation of symbols]

[0104] 10 Screw tightening machine 12 screws 14 Head 22 Main Unit 24 Zipper 26 Clamping rod 50 One side grip part 52 Other side grip part 66 One-side support point 72 one-side first biasing member 106 Other side support point 112 other side first biasing member 214 One-side second biasing member 216 One side ball member 264 other side second biasing member 266 Other side ball member

Claims

1. A screw tightening machine, a main body having a guide hole for guiding the supplied screw; a chuck supported by the main body, into which the screw is supplied through the guide hole, and whose tip opens and closes around a support point with the main body; a biasing member that applies a biasing force in a closing direction in which the tip end of the chuck closes; a clamping rod that pushes the screw toward the tip of the chuck while opening the chuck from a closed state, thereby forming a state in which the head of the screw is held at the tip of the chuck; Equipped with the biasing member includes a first biasing member and a second biasing member, In a region where the opening angle of the chuck that opens in accordance with the movement of the screw being pushed forward is equal to or smaller than a predetermined angle, only the first biasing member biases the chuck in the closing direction, In a region where the opening angle exceeds the predetermined angle, the first biasing member and the second biasing member bias the zipper in the closing direction. Screw tightening machine.

2. The screw fastener according to claim 1, the predetermined angle is the opening angle in a state in which the head of the screw is held by the tip portion of the chuck. Screw tightening machine.

3. The screw fastening tool according to claim 1 or 2, The second biasing member applies a biasing force to the chuck via a ball member. Screw tightening machine.

4. The screw fastening tool according to claim 1 or 2, The biasing force of the second biasing member is greater than the biasing force of the first biasing member. Screw tightening machine.

5. The screw fastener according to claim 1, the chuck has a plurality of gripping portions supported by the main body and capable of gripping the head of the screw, the biasing member includes the first biasing member and the second biasing member disposed between the main body and each of the gripping portions; Screw tightening machine.

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