Screw tightening machine

Abstract

To provide a screw fastening machine capable of fastening a plurality of kinds of screws without tool exchange.SOLUTION: A screw fastening machine 10 includes a driver bit 38 which is configured so as to be capable of rotation by receiving a drive of a rotating drive source 34 and a box bit 39 which is configured so as to be capable of rotation integrally with the driver bit 38 and so as to be relatively movable in an axial direction with respect to the driver bit 38. Thereby, both of a screw N1 having a drive hole and a screw N2 having a drive part can be fastened without tool exchange. Further, the box bit 39 is suspended and supported by the driver bit 38 and is preferably provided with a fitting hole 391 having such a depth that a lower end of the driver bit 38 can be contained.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a screw driving machine for fastening screws into a workpiece. [Background technology]

[0002] Conventionally, screw driving machines equipped with a box bit or a driver bit as a fastening tool that fits into a screw are known, as shown in Patent Documents 1 and 2. The fastening tool of these screw driving machines is connected to a rotary drive source and is configured to be able to fasten a screw into a workpiece with a predetermined torque. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 09-174351 [Patent Document 2] JP 10-328946 Public Relations Summary of the Invention [Problem to be solved by the invention]

[0004] However, conventional screwdrivers can only be equipped with either a box bit or a driver bit, which means that when tightening screws with different head shapes, it is necessary to either change the fastening tool or prepare another screwdriver. [Means for solving the problem]

[0005] The present invention was conceived in consideration of the above-mentioned problems, and aims to provide a screw driver capable of fastening multiple screws with a single unit. To achieve this objective, the present invention features a driver bit configured to rotate when driven by a rotary drive source, and a box bit configured to rotate integrally with the driver bit and move axially relative to the driver bit. The box bit is preferably suspended from the driver bit and has a fitting hole of a predetermined depth that can accommodate the lower end of the driver bit. The present invention also includes a screw guide that accommodates the driver bit and box bit, and an air intake means is preferably connected to the screw guide. The box bit preferably has an outer diameter approximately equal to the inner diameter of the screw guide, and the bottom surface of the fitting hole is preferably formed with an air intake path that extends to the end face on the air intake means side. The end face of the box bit on the air intake means side is preferably formed with a tapered surface that gradually decreases in diameter toward the drive hole. The present invention also preferably includes a lifting means for lifting the screw guide toward the rotary drive source. [Effects of the Invention]

[0006] The screw driver of the present invention includes both a driver bit and a box bit that can rotate integrally with the driver bit and move axially relative to the driver bit. This allows for the fastening of both screws with drive holes formed in the head and screws with drive parts on the outer surface of the head. This reduces the need for screw driver replacement and improves work efficiency. The lower end of the driver bit is enclosed within the box bit, providing surface contact between the screw and the box bit, thereby reducing the likelihood of tilting of the held screw. Furthermore, the driver bit and box bit are enclosed within a screw guide, allowing the screw guide to hold any screw with a head shape that can be held by suction, thereby enabling the fastening of a larger number of screws. Furthermore, the outer diameter of the box bit is approximately the same as the inner diameter of the screw guide, thereby enabling the fastening of screws with diameters smaller than the screw guide. Furthermore, the tapered surface of the box bit prevents increased friction between the box bit and the screw guide due to dust and other particles being sucked in during screw suction, thereby preventing tightening failures. Furthermore, the provision of the pulling means has the advantage that it is possible to fasten the fastener in a narrow space. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a partially cross-sectional side view showing the structure of a screw driver according to the present invention. [Figure 2] (a) is an enlarged, partially cross-sectional side view of a key portion showing the surrounding structure of a driver bit in a standby state, and (b) is an enlarged, partially cross-sectional side view of a key portion showing the surrounding structure of a driver bit in a state in which the driver bit has moved axially relative to the box bit. [Figure 3] 2. (a) is a cross-sectional view taken along line AA in FIG. 2, (b) is a cross-sectional view taken along line BB in FIG. 2, and (c) is a bottom view of (a) in FIG. [Figure 4]An explanatory diagram of the operation of the screw fastening machine of the present invention, where (a) is an enlarged, partially cutaway, cross-sectional side view of the main part showing the state in which the first screw is held by suction, and (b) is an enlarged, partially cutaway, cross-sectional side view of the main part showing the state in which the first screw has been fastened to the workpiece W. [Figure 5] An explanatory diagram of the operation of the screw fastening machine of the present invention, where (a) is an enlarged, partially cutaway, cross-sectional side view of the main part showing the state in which the second screw is held by suction, and (b) is an enlarged, partially cutaway, cross-sectional side view of the main part showing the state in which the second screw has been fastened to the workpiece W. [Figure 6] 1A and 1B are explanatory diagrams illustrating the operation of the screw driving machine according to the present invention, in which (a) is an enlarged, partially cutaway, cross-sectional side view of the main part showing the state in which the third screw is held by suction, and (b) is an enlarged, partially cutaway, cross-sectional side view of the main part showing the state in which the fourth screw is held by suction. [Figure 7] 10A and 10B are partially cutaway side views showing another embodiment of the screw fastener of the present invention, where (a) is a partially cutaway side view showing the standby state, and (b) is a partially cutaway side view showing the state in which the lifting means is driven. DETAILED DESCRIPTION OF THE INVENTION

[0008] An embodiment of the present invention will now be described with reference to the drawings. In Fig. 1, reference numeral 10 denotes a screw driver that fastens a screw N1, which is an example of a fastening part, into a workpiece W (not shown). This screw driver 10 comprises a position control mechanism 20 that moves horizontally when driven by a horizontal articulated robot (not shown), and a driver unit 30 that moves up and down when driven by this position control mechanism 20.

[0009] As shown in FIG. 1 , the position control mechanism 20 includes a frame 21 extending vertically, with an upper plate 22 and a lower plate 23 extending horizontally integrally fixed to the upper and lower ends of the frame 21. A guide rod 24 extending parallel to the frame 21 is provided between the upper plate 22 and the lower plate 23. A driver table 25 configured to slide freely is attached to the guide rod 24 so as to be able to move up and down. An AC servo motor 26 (hereinafter referred to as the lift motor 26), which is an example of a lift drive source, is mounted on the upper plate 22, and a ball screw 27 is integrally and rotatably connected to the output shaft of the lift motor 26. The ball screw 27 is provided between the upper plate 22 and the lower plate 23, and the driver table 25 is connected to the ball screw 27 via a drive nut (not shown) that moves up and down due to the rotation of the ball screw 27. The driver unit 30 is connected to the driver table 25. Therefore, when the lift motor 26 is rotated, the driver stand 25 and the driver unit 30 connected thereto are raised and lowered.

[0010] The driver unit 30 has a connecting plate 31 fixed to the driver base 25, and a hollow cylindrical housing 311 is fixed to the underside of the connecting plate 31. A guide holder 32 is suspended from the housing 311 so as to be movable relatively up and down, and a screw guide 33 having a generally hollow cylindrical shape is fixed to the lower end of the guide holder 32. A hose joint 321 is attached to the guide holder 32, one end of which is connected to the screw guide 33, and the other end of the hose joint 321 is connected to an intake hose (not shown) that is connected to an intake means such as an external vacuum generator. Therefore, when the intake means is driven, a negative pressure is created inside the screw guide 33, and the screw N1 can be sucked and held at the opening at the lower end of the screw guide 33. The guide holder 32 is constantly biased downward by a guide spring 322 enclosed inside the housing 311, and when the guide spring 322 flexes, the guide holder 32 and the screw guide 33 can move axially relative to the housing 311.

[0011] Furthermore, a motor base 312 is placed on the connecting plate 31, and an AC servo motor 34 (hereinafter referred to as the fastening motor 34), which is an example of a rotary drive source that fastens the screw N1, is installed above the motor base 312. The fastening motor 34 is fixed to the motor base 312 with its output shaft facing downward, and a bit shaft 37 is connected to the output shaft of the fastening motor 34 via a connection joint 35 that rotatably passes through the motor base 312 and the driver base 25.

[0012] The connecting joint 35 is formed with a blind hole 351 into which the bit shaft 37 is inserted, and an elongated hole 352 is formed in the blind hole 351, perpendicular to the blind hole 351 and extending in the axial direction of the bit shaft 37. A connecting pin 361 is inserted into the elongated hole 352 so as to be able to move up and down along the elongated hole 352, and the connecting pin 361 is fixed to and supports the bit shaft 37 inserted into the blind hole 351. This allows the bit shaft 37 to rotate integrally with the output shaft of the fastening motor 34 and to move relative to the fastening motor 34 in the axial direction of the bit shaft 37. A cushion spring 362, an example of a biasing member, is enclosed in the blind hole 351, and the cushion spring 362 constantly biases the bit shaft 37 downward. The dimensions of the elongated hole 352 are set within a range that allows the cushion spring 362 to constantly bias the bit shaft 37 and that does not cause the cushion spring 362 to collapse when the bit shaft 37 rises relative to the connecting joint 35.

[0013] The bit shaft 37 is a cylindrical member configured to be rotatable and relatively movable in the axial direction within the screw guide 33, and a driver bit 38 is connected to its lower end. As shown in FIG. 2(a), the driver bit 38 is a rod-shaped member that is inserted into the screw guide 33 so as to be rotatable and relatively movable in the axial direction. The driver bit 38 has an engaging portion 381 configured in a substantially rectangular prism shape, a suspending portion 382 that is continuous with the lower end of the engaging portion 381 and has a larger area than the engaging portion 381 in a plan view, and a fitting portion 383 that is continuous with the lower surface of the suspending portion 382 and has a hexagonal prism shape. As shown in FIG. 3(a), the engaging portion 381 has a corner that is arc-shaped so that it can slide along the inner surface of the screw guide 33. This prevents the bit shaft 37 and the driver bit 38 from swinging within the screw guide 33, and creates a gap between the engaging portion 381 and the inner surface of the screw guide 33 through which air can pass, allowing the screw N1 to be attracted and held at the lower end of the screw guide 33.

[0014] A box bit 39 configured to rotate integrally with the driver bit 38 is suspended and supported by the driver bit 38. As shown in FIG. 3(b), the diameter of the box bit 39 is approximately the same as the hole diameter of the screw guide 33, and the box bit 39 is always housed inside the screw guide 33. A fitting hole 391 that can fit with the head of a screw N2 (described later) is formed in the underside of the box bit 39, and an engagement hole 392 having the same shape as the engagement portion 381 of the driver bit 38 penetrates the bottom of the fitting hole 391 to the top surface of the box bit 39. The box bit 39 configured as described above is suspended and supported with the engagement portion 381 of the driver bit 38 inserted into the engagement hole 392 and the bottom surface of the fitting hole 391 abutting against the hanging portion 382, ​​so that the box bit 39 can rotate integrally with the driver bit 38 and can move axially relative to the driver bit 38, as shown in FIG. 2(b). The fitting hole 391 is configured to be deeper than the axial dimensions of the hanging portion 382 and the fitting portion 383 of the driver bit 38, and is configured to be able to normally accommodate the hanging portion 382 and the fitting portion 383 within the fitting hole 391. Furthermore, a plurality of vent holes 393 are formed in the fitting hole 391, penetrating through to the upper surface of the box bit 39. Furthermore, the box bit 39 is normally biased by a biasing spring 384 attached to the driver bit 38. Moreover, as shown in FIG. 2, a tapered surface 394 is formed on the upper surface of the box bit 39, the diameter of which gradually decreases as it extends downward.

[0015] 3(c), the fitting hole 391 is configured in a generally petal-like shape, with six fitting recesses 3911 in an arc shape centered on the axis of the box bit 39 and six fitting protrusions 3912 that are continuous with the fitting recesses 3911 and protrude radially inward, alternately arranged in the circumferential direction. Furthermore, a lead-in surface 3913 is formed at one end of the box bit 39, as shown in . The lead-in surface 3913 is configured to slope and decrease in diameter as it extends from the opening edge of the fitting hole 391 toward the back, with its maximum diameter set to the same diameter as the arc-shaped fitting recesses 3911. Six vent holes 393 are formed at equal intervals in the circumferential direction for each fitting recess 3911.

[0016] The screw N1 is a fastening component in which the head and shank are integrally formed, and each head has a different shape. The screw N1 has a drive hole (not shown) that is hexagonal in plan view formed in the head, and an enlarged diameter portion that protrudes toward the outer periphery is formed on the head seating surface. This enlarged diameter portion is configured to have approximately the same diameter as the hole diameter of the screw guide 33, and is designed to be held by suction with the top surface of the head abutting against the bottom surface of the box bit 39, as shown in Figure 4(a).

[0017] Next, the operation of the screw driving tool 10 configured as above will be described. When the workpiece W is transported to a predetermined screw fastening point by an external transport means (not shown), the control unit outputs a drive signal to the screw fastening machine 10. Upon receiving this drive signal, the screw fastening machine 10 drives the horizontal articulated robot to move the driver unit 30 above an external supply device (not shown). Thereafter, when the driver bit 38 reaches the axis of the screw N1 waiting on the supply device, the position control mechanism 20 is driven to lower the driver unit 30 toward the screw N1.

[0018] As described above, when the screw guide 33 of the driver unit 30 descending toward the screw N1 abuts against the seating surface of the screw N3 or the component supply device, the suction means is driven to suck and hold the screw N1 as shown in Figure 4(a). Once the screw N1 is sucked and held, the position control mechanism 20 and the horizontal articulated robot are driven to move the driver bit 38 and screw N1 onto the axis of the pilot hole W1 formed in the workpiece W. When the screw N1 reaches the axis of the pilot hole W1, the position control mechanism 20 is driven again to lower the driver unit 30 toward the pilot hole W1 and to drive the fastening motor 34 to rotate the driver bit 38 and box bit 39.

[0019] During this screw tightening process, when the screw N1 abuts against the workpiece W, the descent of the screw N1 and the box bit 39 abutting therewith stops. However, the driver bit 38 receives a downward thrust from the position control mechanism 20 and descends while deflecting the biasing spring 384, so that the fitting portion 383 of the driver bit 38 protrudes from the box bit 39 and fits into the drive hole of the screw N1, as shown in FIG. 4(b). Thereafter, when the fastening motor 34 outputs a predetermined tightening torque, the screw tightening machine 10 ends the screw tightening process and returns to its initial position. Note that, during this screw tightening process, when the lower end of the screw guide 33 abuts against the workpiece W, the driver bit 38 moves relative to the screw guide 33 while deflecting the guide spring 322 in the same manner, and the screw N1 and the driver bit 38 fit together.

[0020] Furthermore, when the above-described screw tightening process is completed, the suction means stops. This causes impurities, such as dust, in the air sucked into the screw guide 33 to fall onto the box bit 39. At this time, the tapered surface 394 is formed on the upper surface of the box bit 39, and the impurities that fall onto the box bit 39 fall along the tapered surface 394 to the bottom side, i.e., radially inward, preventing the impurities from entering between the box bit 39 and the screw guide 33. This prevents an increase in friction between the box bit 39 and the screw guide 33, which in turn prevents torque loss caused by the friction and prevents the appropriate tightening torque from being transmitted to the screw N1. As a result, screw tightening failures and other problems are less likely to occur.

[0021] Next, the fastening of the second screw N2 will be described. This screw N2 is a fastening component having a hexagonal column-shaped drive part at its head, and an enlarged diameter part that protrudes outward is formed on the head seating surface. The enlarged diameter part of this screw N2 is configured to have approximately the same diameter as the hole diameter of the screw guide 33, and is designed so that the head is held by suction when fitted into the fitting hole 391, as shown in Figure 5(a).

[0022] The screw N2 held by suction as described above is fastened to a predetermined workpiece W as shown in FIG. 5(b) by the rotation of the box bit 39 during the screw tightening process. During the screw tightening process, the box bit 39 retracts until the lower end of the driver bit 38 abuts against the top surface of the head of the screw N2, and the screw N2 receives a screw tightening thrust from the driver bit 38. By providing the driver bit 38 and the box bit 39 configured to rotate integrally with the driver bit 38 and to be movable axially relative to the driver bit 38, the screw tightening tool 10 can tighten both the screw N1, which has a drive hole (not shown) formed in the head, and the screw N2, which has a drive portion formed on the outer surface of the head. As a result, there is no need to change bits when tightening different screws, improving work efficiency.

[0023] Next, we will explain the case of fastening a third screw N3. This screw N3 is a fastening component with a drive hole (not shown) of the same shape as N1 formed in its head, and an enlarged diameter portion protruding outward from the head seating surface. The enlarged diameter portion of this screw N3 is configured to have a diameter smaller than the hole diameter of the screw guide 33. As shown in FIG. 6(a), the screw N3 is held by suction with the upper edge of its head abutting against the lead-in surface 3913 formed on the underside of the box bit 39. At this time, the outer diameter of the box bit 39 is configured to be approximately the same as the hole diameter of the screw guide 33. Therefore, little air can pass through the minute gap between the outer peripheral surface of the box bit 39 and the inner peripheral surface of the screw guide 33. Most of the sucked air passes through the fitting hole 391 of the box bit 39. Therefore, even if there is a gap between the screw N3 and the screw guide 33, the screw N3 is held by suction in the screw guide 33 with approximately the same suction force as the screw N1.

[0024] Next, we will explain the case of fastening the fourth screw N4. This screw N4 is also a fastening part with a drive hole (not shown) that is hexagonal in plan view formed in the head, and an enlarged diameter portion that protrudes toward the outer periphery is formed on the head seating surface. The enlarged diameter portion of the screw N4 is configured to have a diameter larger than the hole diameter of the screw guide 33, and is designed to be held by suction with the enlarged diameter portion abutting against the underside of the screw guide 33, as shown in Figure 6(b).

[0025] The screws N3 and N4 held by suction as described above are tightened into a predetermined workpiece W by fitting the fitting portion 383 of the driver bit 38 protruding from the box bit 39 into the drive hole formed in the head, just like the screw N1. As described above, the screw guide 33 containing the driver bit 38 and box bit 39 is provided, and the screw is sucked into the screw guide 33, so that any screw that can be held by suction in the screw guide 33 can be sucked, held, and tightened. As a result, it becomes possible to tighten a larger number of screws, further improving work efficiency.

[0026] As a second embodiment, a lifting means 40 may be provided to lift the guide holder 32 upward. As shown in FIG. 7(a), the lifting means 40 includes a lifting cylinder 41, which is an example of a lifting drive source, and a lifting plate 42 connected to the drive unit of the lifting cylinder 41 and abutting against the lower surface of the guide holder 32. The lifting plate 42 has a U-shaped groove 43 formed therein so as to avoid the screw guide 33. When the lifting means 40 configured in this manner is driven, the guide holder 32 and the screw guide 33, which are lifted by the lifting plate 42, rise relative to the driver bit 38 and box bit 39, as shown in FIG. 7(b), so that the box bit 39 protrudes from the lower end of the screw guide 33. As a result, the screw guide 33 does not abut against the workpiece W during the screw tightening process. As a result, the outer diameter of the tip of the driver unit 30 is reduced, allowing it to be fastened in a relatively narrow space, and since the repulsive force of the guide spring 322 that urges the screw guide 33 downward is not applied to the workpiece W, there are advantages such as a reduction in the downward thrust acting on the workpiece W.

[0027] The screw driver 10 according to the present invention is not limited to the above-described configuration, and various modifications are possible without departing from the spirit of the invention. For example, the shapes of the fitting portion 383 of the driver bit 38 and the fitting hole 391 of the box bit 39 are preferably modified appropriately to match the head shape of the screw being used. A hexagonal shape is acceptable as long as the shape is non-circular. Furthermore, the cross-sectional shapes of the engaging portion 381 and the engaging hole 392 are not limited to a substantially rectangular prism shape, and other shapes are acceptable. Furthermore, the screw driver 10 may be used as a temporary tightening tool that temporarily tightens screws at high speed and low torque, and may be applied to the upstream process of a retightening tool that tightens screws at low speed and high torque. [Explanation of symbols]

[0028] 10...Screw tightening machine 33...Screw guide 38... Driver bit 39...Box Bit 391 ... fitting hole 393... Intake path 394 ... Tapered surface 40... Raising means

Claims

1. A screw driving machine comprising a driver bit configured to be rotatable by receiving drive from a rotary drive source, and a box bit configured to be rotatable integrally with the driver bit and to be movable axially relative to the driver bit, and further comprising a screw guide containing the driver bit and box bit, and an air intake means connected to the screw guide.

2. The screw driving machine described in Claim 1, characterized in that the box bit is suspended and supported by the driver bit, has a fitting hole of a predetermined depth that can accommodate the lower end of the driver bit, the outer diameter of the box bit is configured to be approximately the same as the inner diameter of the screw guide, and the bottom surface of the fitting hole of the box bit has an intake path formed that penetrates to the end face on the intake means side.

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