Screw tightening machine

Abstract

To provide a screw fastener which can be installed even in a narrow place.SOLUTION: This device is composed of a driver unit 30 having a motor 32 for rotationally driving a bit shaft 33 fittable to a screw S, an elevating unit 20 for elevating the driver unit 30, and a clamp unit 40 for fixing a workpiece W screwed to the screw S below the bit shaft 33. The screw fastening machine is characterized in that a clamp unit (40) has a pressing member (47) for pressing a work (W) conveyed to a predetermined receiving position downward of a bit shaft (33), a positioning jig (46) arranged to face the pressing member (47) and guiding the work (W) downward of the bit shaft (33), and a discharge section (49) provided below the positioning jig (46), and the work (W) is fixed by the pressing member (47) pressing the work (W) against the positioning jig (46), while the work (W) falls toward the discharge section (49) when the pressure applied by the pressing member (47) is released.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] A conventional screw fastener for fastening screws to workpieces such as nuts is disclosed in Patent Document 1. This screw fastener includes a driver unit for fastening the screws, a moving unit for raising and lowering the driver unit, and a work transport mechanism for positioning the workpiece on the axis of the driver unit. The work transport mechanism of this screw fastener includes a supply rail, a rotary table for moving the workpiece on the supply rail onto the axis of the driver unit, and a discharge section for discharging the workpiece after the driver unit has completed fastening the screw. With this structure, this screw fastener can automatically fasten screws to nuts supplied onto the axis of the driver unit by the work transport mechanism and discharge the threaded screws and nuts to the outside. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-123036 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the above-mentioned screw driving machine has a problem that the entire screw driving machine is large because the workpiece is transported by a rotary table, and it can only be installed in a large space.

[0005] Therefore, an object of the present invention is to provide a screw driver that can be installed even in a narrow space. [Means for solving the problem]

[0006] In order to achieve this object, the present invention comprises a driver unit having a motor that rotates a bit shaft that can be engaged with a screw, an elevating unit that raises and lowers the driver unit, and a clamping unit that secures a workpiece that can be threaded with the screw, wherein the clamping unit has a pressing member that presses the workpiece transported to the predetermined receiving position downward toward the bit shaft, a positioning jig that is arranged opposite the pressing member and guides the workpiece downward toward the bit shaft, and a discharge section that is provided below the positioning jig, wherein the pressing member secures the workpiece by pressing it against the positioning jig, and when the pressure from the pressing member is released, the workpiece falls toward the discharge section. It is preferable that the positioning jig has an arc-shaped guide surface facing the pressing member, and is configured to guide the abutted workpiece along the arc of the guide surface to below the bit shaft. Furthermore, it is preferable that the clamp unit has a transport mechanism that transports the work supplied from an external parts feeder to the receiving position, and that the transport mechanism has a slide block having a holding portion on which the work is placed, and a reciprocating drive source that receives the slide block at the receiving position and moves it back and forth horizontally, and that the pressing member abuts against the side of the work placed on the holding portion. [Effects of the Invention]

[0007] According to the above invention, a workpiece transported to a receiving position is positioned and fixed by a positioning jig and a pressing member that presses the workpiece toward the positioning jig. Because the pressing member is only driven linearly, the size of the screw fastener can be relatively small. This has the advantage of allowing installation in a small space. Furthermore, because the pressing member only moves back and forth between two positions, an advanced position and a retracted position, it is easier to control than conventional screw fasteners that require angular control of a rotary table. Furthermore, by clamping the workpiece between the pressing member and the positioning jig, screws can be fastened even if the workpiece is cylindrical. Furthermore, because a discharge section is provided below the positioning jig, the workpiece passes through the discharge section and is ejected when the pressure from the pressing member is released. In this way, the driving of the pressing member allows three operations: positioning, fixing, and ejecting the workpiece. In addition, since the positioning jig has an arc-shaped guide surface, it has the advantage that the abutted workpiece can be guided to a predetermined fastening position. Furthermore, because the transport mechanism has a slide block that supports the workpiece from below and the pressing member is configured to abut the side of the workpiece on the slide block, there are advantages such as preventing interference and collision between the slide block and the pressing member. Furthermore, because the slide block can be retracted after the workpiece is clamped between the positioning jig and the pressing member, there are also advantages such as making it possible to place the next workpiece on the slide block while the screws are being tightened. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a side view showing the structure of a screw driver according to the present invention. [Figure 2] 3 is an enlarged, partially cutaway, cross-sectional side view of a main portion showing the structure of a work supply unit according to the present invention. FIG. [Figure 3] 3 is an enlarged, partially cutaway, cross-sectional side view of a main portion showing a transition from the state of FIG. 2 to the next state. [Figure 4] FIG. 2 is an enlarged plan view of a main part showing the structure of a work supply unit according to the present invention. [Figure 5]5 is an enlarged plan view of a main part showing a state transitioning from the state of FIG. 4 to the next state. DETAILED DESCRIPTION OF THE INVENTION

[0009] An embodiment of the present invention will be described below with reference to the drawings. In Fig. 1, reference numeral 10 denotes a screw driving machine that drives a screw S into a cylindrical workpiece W. This screw driving machine 10 has a lifting unit 20, a driver unit 30 that drives the screw S, a clamp unit 40 that fixes the workpiece W below the driver unit 30, and a control unit that controls the driving of these units.

[0010] As shown in FIG. 1, the lifting unit 20 includes a base 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 base 21. A guide rod 24 extending parallel to the base 21 is provided between the upper plate 22 and the lower plate 23, and 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 for lifting (hereinafter referred to as the lift motor 26), which is an example of a lifting 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 driver table 25 includes a drive nut that is threadedly engaged with the ball screw 27 and moves up and down as the ball screw 27 rotates. Therefore, the driver table 25 moves up and down when the lift motor 26 is rotationally driven.

[0011] As shown in FIG. 1 , the driver unit 30 has a hollow cylindrical housing 31 connected to the driver stand 25 of the lifting unit 20. An AC servo motor 32 (hereinafter referred to as the bit rotation motor 32) is fixed to the housing 31 with its output shaft (not shown) inserted into the housing 31. A bit shaft 33 that can rotate integrally with the output shaft of the bit rotation motor 32 is suspended from the output shaft of the bit rotation motor 32, and the lower end of the bit shaft 33 is configured to be engageable with the head of the screw S. With this structure, the bit shaft 33 moves up and down in the axial direction when driven by the lifting unit 20 and rotates when driven by the bit rotation motor 32. The bit shaft 33 is hollow and has a hose joint 34 at its upper end to which an air suction hose is connected. The hose joint 34 is connected to an external negative pressure generating means. As a result, when the negative pressure generating means is driven, a negative pressure is generated inside the bit shaft 33, allowing the screw S to be attracted and held at the lower end opening of the bit shaft 33.

[0012] A chuck unit 35 for holding screws S that have been pressure-fed from an external screw parts feeder (not shown) is fixed to the lower plate 23 on the ascending / descending path of the bit shaft 33. The chuck unit 35 has a chuck body 36 through which the bit shaft 33 passes, and a pair of chuck jaws 37 that are attached to the chuck body 36 so as to be able to swing freely and that receive the screws S.

[0013] The clamp unit 40 includes a conveying mechanism 41 that separates and supplies the workpieces W supplied from an external work parts feeder (not shown) one by one, and a holding mechanism 45 that fixes the workpieces W received from the conveying mechanism 41 at a predetermined clamping position set on an extension line of the bit shaft 33 of the driver unit 30.

[0014] The transport mechanism 41 includes a supply rail 42 that aligns and transports the workpieces W, and a slide block 43 that separates and supplies the workpieces W on the supply rail 42 one by one to the holding mechanism 45. The supply rail 42 is configured so that the workpieces W supplied from the work part feeder can be placed on its upper surface, and is configured to transport the workpieces W in a line by driving a vibration drive source (not shown). A slide block 43 that reciprocates in a direction perpendicular to the supply rail 42 is provided at the front of the supply rail 42. A piston rod of a moving cylinder 44 that reciprocates the slide block 43 toward the front is attached to the base end of the slide block 43, and a holding portion 431 that can be connected to the supply rail 42 is provided at the front end of the slide block 43. When the piston rod of the moving cylinder 44 retracts, the holding portion 431 receives the leading workpiece W placed on the supply rail 42 continuously from the top surface of the supply rail 42, and when the piston rod extends, the holding portion 431 transports the workpiece W to the holding mechanism 45. Furthermore, the base end side of the holding portion 431 of the slide block 43 is higher than the upper surface of the supply rail 42, and is configured to hinder the forward movement of the workpiece W. As a result, the workpiece W is transferred from the supply rail 42 to the slide block 43 only when the holding portion 431 of the slide block 43 is continuous with the tip of the supply rail 42.

[0015] The holding mechanism 45 includes a positioning jig 46 that guides the workpiece W to the clamping position, and a pressing member 47 that presses the workpiece W on the holding portion 431 of the slide block 43 against the positioning jig 46. The positioning jig 46 has an arc-shaped guide surface 461 facing the pressing member 47, and is configured to guide the workpiece that contacts it to the clamping position according to the arc of the guide surface 461. Meanwhile, the pressing member 47 is configured to reciprocate in a direction perpendicular to the slide block 43 when driven by a pressing drive unit 48, and is positioned at a height at which it abuts against the side of the workpiece W placed on the holding portion 431. The stroke of the pressing drive unit 48 is set so that the pressing member 47 reciprocates between two points: a retreated position that is set behind the receiving position so as not to obstruct the entry of the workpiece W into the receiving position, as shown in FIG. 4, and an advanced position at which the workpiece W can be pressed against the positioning jig 46, as shown in FIG. 5.

[0016] The pressing drive unit 48 has a pressing cylinder 481, which is a driving source, and a connecting shaft 482 arranged between the pressing cylinder 481 and the pressing member 47. As shown in FIGS. 2 and 3 , the connecting shaft 482 is configured to be swingable about a support shaft 483, and its ends are connected to the piston rod of the pressing cylinder 481 and the pressing member 47, respectively. The connecting shaft 482 is configured so that the distance from the support shaft 483 to a connecting portion 485 with the pressing cylinder 481 is longer than the distance from the support shaft 483 to a connecting portion 484 with the pressing member 47, and is configured so that the workpiece W is pressed against the positioning jig 46 with a force equal to or greater than the force output by the pressing cylinder 481. In this embodiment, the distance from the support shaft 483 to the connecting portion 485 with the pressing cylinder 481 is set to be five times longer than the distance from the support shaft 483 to the connecting portion 484 with the pressing member 47.

[0017] The holding mechanism 45 also has a discharge section 49 below the clamping position. This discharge section 49 has a tapered hole 491 directly below the clamping position that gradually narrows from its upper opening toward its bottom, and a guide hose 492 that continues to a predetermined discharge container is connected to the bottom of this tapered hole 491. The bottom of the tapered hole 491 and the guide hose 492 are set to a size that allows the screw S and workpiece W to pass through. Therefore, when the pressure from the pressing member 47 is released, the workpiece W falls into the discharge section 49 due to gravity, and is guided to the discharge container through the tapered hole 491 and the guide hose 492.

[0018] The control unit is connected to the lifting unit 20, the driver unit 30, and the clamp unit 40, and is configured to be able to control the driving of these units. The control unit also includes a sensor 51 (hereinafter referred to as the arrival detection sensor 51) that detects that the workpiece W has been placed on the holding unit 431 of the clamp unit 40, and a sensor 52 (hereinafter referred to as the position detection sensor 52) that detects whether the workpiece W is present at the receiving position or the fastening position. These sensors are optical sensors in which a light-emitting unit emits detection light toward a light-receiving unit, and detects the workpiece W when this detection light is blocked. The arrival detection sensor 51 is configured to emit two detection lights and detect that the workpiece W has reached the holding unit 431 when both of the lights are blocked.

[0019] Next, the operation of the screw driver 10 configured as above will be described. When a drive signal is input, the control unit drives the screw parts feeder to supply screws S to the chuck unit 35 and drives the moving cylinder 44 to move the slide block 43 backward. As a result, as shown in FIG. 4 , the holding portion 431 of the slide block 43 connects to the tip of the supply rail 42, and the workpiece W is vibrated and transported from the supply rail 42 toward the holding portion 431. When the workpiece W blocks the detection light of the arrival detection sensor 51, the control unit drives the moving cylinder 44 again to move the slide block 43 forward. At this time, the arrival detection sensor 51 emits two detection lights, so it can detect that the workpiece W has begun to be placed on the holding portion 431 and that the workpiece W has been transported to the back of the holding portion 431. This prevents the workpiece W from entering too shallowly, causing it to fall while the slide block 43 is moving, or preventing the next workpiece W from entering the holding portion 431. As a result, when the slide block 43 moves, it is possible to prevent the workpiece W from getting caught between the slide block 43 and the tip of the supply rail 42, and the workpiece W can be transported stably to the receiving position.

[0020] As described above, when the holder 431 of the slide block 43 and the workpiece W reach the receiving position by driving the moving cylinder 44, the position detection sensor 52 is interrupted by the workpiece W. When the position detection sensor 52 is interrupted, the control unit drives the pressing cylinder 481 to move the pressing member 47 toward the positioning jig 46. As a result, the pressing member 47 comes into contact with the side of the workpiece W on the holder 431, and the workpiece W is clamped between the positioning jig 46 and the pressing member 47, as shown in FIG. 5.

[0021] When the workpiece W is clamped between the pressing member 47 and the positioning jig 46, the control unit drives the lifting unit 20 and the driver unit 30 to rotate and lower the bit shaft 33 toward the workpiece W. During this descent, the bit shaft 33 engages with the screw S supplied to the chuck unit 35. The screw S is then tightened into the workpiece W. At this time, the pressing member 47 is pressed against the positioning jig 46 by the connecting shaft 482 with a force five times the force output by the pressing cylinder 481, firmly holding the workpiece W. This prevents the workpiece W from rotating together with the screw S when the screw S is screwed into the workpiece W. Therefore, the screw S can be tightened into the workpiece W with a predetermined tightening torque. The control unit also drives the moving cylinder 44 simultaneously with the lifting unit 20 and the driver unit 30 to retract the slide block 43 until the holding portion 431 connects with the tip of the supply rail 41. This allows the next workpiece W to be supplied onto the holder 431 while the screw S is being fastened to the workpiece W, thereby improving the cycle time.

[0022] When the screw S is fastened to the workpiece W as described above, the control unit stops the rotation of the bit shaft 33 and drives the lifting unit 20 to raise the driver unit 30 to the initial position. Thereafter, the control unit drives the pressing cylinder 481 to reduce the pressing force of the pressing member 47, causing the workpiece W to fall downward. The fallen workpiece W passes through the discharge unit 49 and is discharged into a discharge container. In addition, because a tapered hole 491 is provided below the fastening position, even if the workpiece W is slightly misaligned, it will slide down to the guide hose 492 without any problems.

[0023] The screw driving machine 10 configured as described above has the advantage of being relatively inexpensive and easy to manufacture, since it can move, fix, and eject the workpiece W using only two linear drive sources, the moving cylinder 44 and the pressure cylinder 481. In addition, since it does not have a rotation mechanism like conventional screw driving machines, it has the advantage of being space-saving and can be installed in narrow locations.

[0024] The screw driving tool 10 according to the present invention is not limited to the above-described one, and various modifications are possible without departing from the spirit of the invention. For example, the workpiece W is not limited to a cylindrical shape, and may be a hexagonal or rectangular prism shape, etc. In this case, it is preferable that the contact surface 461 of the positioning shaft is set to match the shape of the workpiece W. The bit shaft 33 is an example of a fastening tool that can be fitted with a screw, and there is no problem in appropriately changing the shape of its tip to a conventionally known shape to match the shape of the screw. [Explanation of symbols]

[0025] 10...Screw tightening machine 20... Lifting unit 21... Foundation 22 ... Upper board 23 … Lower plate 24... Guide rod 25... Driver's stand 26... Lifting motor 27... Ball screw 30...Driver unit 31 … Housing 32... Bit rotation motor 33... Bit shaft 34... Hose fitting 35...Chuck unit 36...Chuck body 37...Chuck jaws 40... Clamp unit 41 ... Transfer mechanism 42 ... supply rail 43... Slide block 44...Transfer cylinder 45 … Holding mechanism 46 ... Positioning jig 47 ... Pressing member 48 ... Pressing drive unit 49...Discharge unit 51 ... Arrival detection sensor 52... Position detection sensor S...screw W... Work

Claims

1. a driver unit having a motor that rotates a bit shaft that can be fitted with a screw; a lifting unit that lifts and lowers the driver unit; and a clamp unit for fixing a workpiece that can be screwed with the screw. The clamp unit includes: a pressing member that presses the workpiece conveyed to a predetermined receiving position downwardly of the bit shaft; a positioning jig disposed opposite the pressing member and guiding the workpiece below the bit shaft; a discharge portion provided below the positioning jig; A screw driving machine characterized in that the pressing member fixes the workpiece by pressing the workpiece against the positioning jig, and when the pressure from the pressing member is released, the workpiece falls toward the discharge section.

2. The screw driving machine according to claim 1, characterized in that the positioning jig has an arc-shaped guide surface facing the pressing member, and is configured to guide the abutted workpiece along the arc of the guide surface to below the bit shaft.

3. the clamp unit has a transport mechanism that transports a workpiece supplied from an external parts feeder to the receiving position, The transport mechanism includes a slide block having a holder on which the workpiece is placed; a reciprocating drive source that receives the slide block at the receiving position and moves it reciprocally in a horizontal direction, The screw driving tool according to claim 1, wherein the pressing member abuts against a side surface of the workpiece placed on the holding portion.

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