JP7776996B2 - Screw tightening device - Google Patents

Description

The present invention relates to a screw tightening device equipped with a component supply device that can inspect the overall length of fastening components.

Conventionally, screw tightening devices equipped with a driver unit that engages with the screw and a component supply device that supplies the screw to the driver unit are known. Patent Document 1 in particular discloses a component supply device capable of measuring the overall length of a screw. This component supply device has a hanging member that suspends and supports the screw, and a pair of photoelectric sensors positioned to sandwich the legs of the screw suspended and supported by the hanging member. One of the photoelectric sensors emits laser light, which the other receives, and the length of the fastening part is determined to be good or bad based on the amount of light received. Furthermore, after the photoelectric sensors determine whether the screw is good or bad, this component supply device is able to pressure-feed good screws to the driver unit through the screw supply hose.

Japanese Patent Application Laid-Open No. 2000-95328

However, conventional screw tightening devices are designed so that the parts supply device pressure-feeds screws to the driver unit. Therefore, while good screws could be removed by pressure-feeding them to the driver unit as described above, defective screws had to be removed individually by the operator. As a result, the next stage of screws could not be supplied until the operator removed the defective screws, resulting in problems such as long downtime and reduced work efficiency. Furthermore, because the parts supply device pressure-feeds screws, there are also problems such as the inability to use some screws, such as short screws that tend to reverse inside the supply hose connecting the parts supply device and the chuck unit, and plastic screws that are damaged by the impact of colliding with the chuck unit.

The present invention was created in consideration of the above-mentioned problems, and aims to provide a screw tightening device with high work efficiency. To achieve this objective, the present invention features a component supply device equipped with a measuring means for measuring the length of a fastening component and configured to keep the fastening component waiting at a predetermined waiting position after length measurement by the measuring means; a driver unit for removing the fastening component from the waiting position and fastening it to a workpiece; a position control mechanism for moving the driver unit; and a control unit configured to compare the measurement value of the measuring means with a preset value to determine whether the length of the fastening component is good or bad, and to control the drive of the position control mechanism based on the determination result. Preferably, the control unit controls the drive of the position control mechanism to move the driver unit to a predetermined fastening position if the length of the fastening component is good, and to move the driver unit to a predetermined ejection position if the length of the fastening component is bad.

The component supply device preferably includes a suspension member that suspends and supports the fastening component, a push-up means that pushes the fastening component suspended from the suspension member upward from below, and a restriction lid that is fixed above the push-up means and restricts the fastening component pushed up by the push-up means from being pushed up beyond a predetermined height, and the measuring means measures a dimension equivalent to the overall length of the fastening component restricted by the restriction lid, and the suspension member is configured to wait at a predetermined standby position while suspending and supporting the fastening component after the measuring means measures the length of the fastening component. It is also preferable that the device include a detection sensor that detects fastening components that have reached the standby position, and a reciprocating drive source that moves the suspension member based on a signal from the detection sensor.

According to the above invention, the driver unit is configured to retrieve fastening components transported by the component supply device to a standby position and move them to a predetermined position. Because the screws are not pressure-fed, it has the advantage of being usable for supplying short screws, plastic screws, and other screws that are difficult to pressure-fed. Furthermore, the control unit determines whether the length of the fastening component is good or bad and controls the drive of the position control mechanism based on the determination result. This eliminates the need for the screw tightening device to wait until the worker removes the screw, thereby improving work efficiency. Furthermore, the control unit is configured to transport good screws to a predetermined fastening position while ejecting defective screws to a predetermined ejection position, which has the advantage of allowing defective screws to be smoothly removed even if they are mixed in.

In addition, because the measuring means is configured to measure the overall length of the fastening part, it has the advantage of being able to detect foreign products with different head heights. Furthermore, because it is equipped with a detection sensor that can detect when the screw has reached a specified standby position, it is possible to immediately detect when the screw is not supported by the hanging member, which also has the advantage of shortening the cycle time.

1 is a side view showing a screw fastening device according to the present invention; 1 is a plan view showing a screw fastening device according to the present invention; 1A and 1B are enlarged views of essential parts showing the operation of the component supply device according to the present invention, in which (a) is a plan view showing a state in which the hanging member is located at a receiving position, (b) is a plan view showing a state in which the hanging member is located at an inspection position, and (c) is a plan view showing a state in which the hanging member is located at a standby position. 4A and 4B are enlarged views of essential parts showing the operation of the component supply device according to the present invention, in which (a) is a cross-sectional side view taken along line A-A in FIG. 3, (b) is a cross-sectional side view taken along line B-B in FIG. 3, and (c) is a cross-sectional side view taken along line B-B in FIG. 3 for explaining the operation of transitioning from the state in (b) to the next state.

Embodiments of the present invention will now be described with reference to the drawings. In Figures 1 to 4, reference numeral 10 denotes a screw tightening device that tightens a screw N, an example of a fastening component, into a predetermined workpiece. The device includes a driver unit 20 that tightens the screw N, a position control mechanism 24 that moves the driver unit 20, a component supply device 30 that supplies the screw N to the driver unit 20, and a control unit 50 that controls the driving of these components.

As shown in FIG. 1, the driver unit 20 includes a driver bit 21 that can be fitted with a screw N, a tightening motor 22 that rotates the driver bit 21, and a screw guide 23 that houses the driver bit 21 and allows it to move back and forth in the axial direction. The screw guide 23 is biased toward the workpiece by a cushion spring (not shown), and is configured to move axially relative to the driver bit 21 and tightening motor 22 when the cushion spring flexes. Furthermore, an air suction means such as a vacuum generator is connected to the screw guide 23, and when this air suction means is activated, the screw N can be sucked and held at its lower end opening.

The position control mechanism 24 is composed of a linear arm 25 that can move linearly in the forward and backward directions, a swivel arm 26 that is rotatably attached to the linear arm 25, and an elevation drive unit 27 attached to the tip of the swivel arm 26. The elevation drive unit 27 includes a ball screw 271 that extends in the vertical direction, an elevation motor 272 that rotates the ball screw 271, and a drive nut 273 that threads onto the ball screw 271, and the driver unit 20 is connected to the drive nut 273. By driving the position control mechanism 24, the driver unit 20 can move up and down as shown by the two-dot chain line in Figure 1 and can move within the range of motion 201 shown in Figure 2.

The component supply device 30 comprises a chute rail 31 that transports the screws N forward, and a feed unit 32 that receives the front screw N on the chute rail 31. The feed unit 32 comprises a frame 33, a hanging member 36 disposed within the frame 33, and a push-up means 40 that pushes upward the screw N supported by the hanging member 36.

The chute rail 31 is composed of two plates extending in the front-to-rear direction, and these plates are installed with a predetermined gap between them that is slightly wider than the outer diameter of the shank of the screw N but narrower than the outer diameter of the head. This allows the chute rail 31 to support the screw N in a suspended state with the head seat abutting against its upper surface. A vibrator (not shown) is also connected to the chute rail 31, and the suspended screw N is transported forward by the vibrations of this vibrator. A storage section (not shown) capable of storing a large number of screws N is connected to the rear of the chute rail 31, and this storage section is configured to supply the screws N in a single row onto the chute rail 31.

As shown in Figures 3 and 4, the frame 33 is formed with a supply port 331 that opens to the rear. The chute rail 31 enters this supply port 331, and a notched groove 332 extending perpendicular to the chute rail 31 (hereinafter referred to as the lateral direction) is continuous in front of it. This notched groove 332 is closed on both lateral sides by side walls 334, 335. An inspection hole 333 that penetrates vertically is formed in the bottom surface of the notched groove 332, located closer to the side wall 334 than the supply port 331. Meanwhile, a fixed regulating lid 34 disposed above the inspection hole 333 and a detection sensor 35 disposed closer to the side wall 334 than the regulating lid 34 are fixed to the top surface of the frame 33. The restricting cover 34 is a plate that prevents the screw N from rising above a predetermined height when the push-up means 40 (described later) pushes up the screw N. A passage groove 341 is formed through its underside, allowing the head of the screw N to pass through. Furthermore, the detection sensor 35 is a pair of optical sensors that emit detection light from a light-emitting portion to a light-receiving portion. As shown in FIG. 3C, the detection sensor 35 is disposed at a predetermined height where the detection light is blocked by the head of the screw N that has reached the gap between the light-emitting portion and the light-receiving portion. The detection sensor 35 is connected to the control unit 50 and is configured to output a detection signal for the screw N to the control unit 50 when the light from the detection sensor 35 is blocked by the screw N, as described above. The passage groove 341 of the restricting cover 34 is sized so that the gap between the upper end of the head and the passage groove 341 is shorter than the length of the screw's leg. Therefore, when the screw N is pushed up by the push-up means 40 during operation (described later), the lower end of the leg of the screw N is prevented from slipping out of the hanging groove 361.

The hanging member 36 is disposed within the notched groove 332, and its thickness in the front-to-rear direction is configured to be approximately the same dimension as the groove width of the notched groove 332. A roughly U-shaped hanging groove 361 that penetrates vertically is cut out on the rear surface of the hanging member 36, and the groove width of this hanging groove 361, like the chute rail 31, is configured to be slightly wider than the outer diameter of the shank of the screw N but narrower than the outer diameter of the head. This allows the hanging member 36 to slide freely along the notched groove 332 and to suspend and support the screw N received from the chute rail 31.

Furthermore, reciprocating cylinders 371, 372 are attached to side walls 334, 335, causing suspending member 36 to reciprocate along notched groove 332. Reciprocating cylinder 371 is an air cylinder fixed to side wall 334, and its piston rod is connected to suspending member 36. The stroke of this reciprocating cylinder 371 is designed so that when the piston rod is retracted, suspending groove 361 of suspending member 36 connects to chute rail 31 as shown in FIG. 3(a), while when the piston rod is extended, suspending groove 361 is positioned between detection sensors 35 as shown in FIG. 3(c). In other words, the suspending member is configured to reciprocate, driven by reciprocating cylinder 371, between a position where suspending groove 361 connects to chute rail 31 (hereinafter referred to as the receiving position) and a position where suspending groove 361 is positioned between the light-receiving unit and light-emitting unit of detection sensor 35 (hereinafter referred to as the standby position).

On the other hand, reciprocating cylinder 372 is an air cylinder fixed to side wall 335, and its piston rod is arranged so that it can abut against the hanging member 36. This reciprocating cylinder 372 has a larger cylinder diameter than reciprocating cylinder 371, and its stroke is shorter than that of reciprocating cylinder 371. As a result, when both reciprocating cylinders 371 and 372 extend their piston rods, the hanging member is pressed down by reciprocating cylinder 372 and stops at a predetermined position (hereinafter referred to as the inspection position) between the receiving position and the standby position, as shown in Figure 3(b). Furthermore, inspection hole 333 of frame 33 is positioned so as to communicate with hanging groove 361 of hanging member 36 that has reached the inspection position, as shown in Figures 4(b) and 4(c).

As described above, the suspending member 36 is driven by the reciprocating cylinders 371 and 372 to be positioned at one of three positions: the receiving position, the standby position, and the inspection position. Furthermore, the component supply device 30 is positioned so that, as shown in Figure 3(c), at least the suspending groove 361 of the suspending member 36 that has reached the standby position is positioned within the range of motion 201 of the driver unit 20.

Furthermore, as shown in FIG. 4(a), a push-up means 40 for pushing up the screw N is provided on the underside of the frame 33. This push-up means 40 is equipped with a push-up cylinder 41, an example of a push-up drive source, fixed to the frame 33. The drive unit 411 of this push-up cylinder 41 is connected to a push-up rod 42 located directly below the inspection hole 333 and a measuring unit 43 that operates in conjunction with this push-up rod 42. This push-up rod 42 is configured to have approximately the same diameter as the inspection hole 333 and is set to a length that allows it to abut against the lower end of the screw N suspended from the hanging member 36 when the drive unit 411 of the push-up cylinder 41 is raised, as shown in FIG. 4(c). Meanwhile, the measuring unit 43 is a contact sensor equipped with a contact 431 that contracts in a contracting direction upon contact with the frame 33, and is configured to output the amount of contraction of this contact 431 to the control unit 50.

The control unit 50 is connected to the driver unit 20, the position control mechanism 24, the component supply device 30, and external devices such as suction means, and is configured to be able to control various drives. The control unit 50 is also configured to be able to switch the target position of the driver unit 20 set by the position control mechanism 24 based on a signal from the measurement means 43. If the length of the screw N is appropriate, the target position is set above a predetermined screw tightening point, but if the length of the screw N is inappropriate, the target position is switched to above a predetermined external ejection position.

Next, the operation of the screw fastening device 10 configured as above will be described.
When a drive signal is input, the control unit 50 drives the vibrator of the component supply device 30 and retracts the piston rods of the reciprocating cylinders 371 and 372 as shown in FIG. 3A. This vibrates the chute rail 31, and the screw N suspended and supported on the chute rail 31 is vibrated and conveyed forward. At the same time, the hanging groove 361 of the hanging member 36 that has reached the receiving position connects to the terminal end of the chute rail 31. As a result, the leading screw N is transferred from the terminal end of the chute rail 31 to the hanging groove 361. When the screw N is suspended and supported in the hanging groove 361, the control unit 50 drives the reciprocating cylinders 371 and 372 to extend these piston rods. As a result, the hanging member 36 is driven by the reciprocating cylinder 371 and moves toward the side wall 334. At this time, since the piston rod of the reciprocating cylinder 372 is also extended, the suspension member 36 comes into contact with the piston rod of the reciprocating cylinder 372 as shown in FIG. 3(b) and stops at the inspection position.

When the hanging member 36 reaches the inspection position as described above and the hanging groove 361 connects to the inspection hole 333 as shown in Figure 4(b), the control unit 50 retracts the push-up cylinder 41, raising the push-up rod 42 and measuring means 43. As a result, the upper end of the push-up rod 42 abuts against the lower end of the screw N suspended from the hanging member 36, pushing it upward. As a result, the screw N is pushed upward until its top surface abuts the restricting cover 34, as shown in Figure 4(c). At this time, the measuring means 43 also rises in conjunction with the push-up rod 42, pressing its contact 431 against the underside of the frame 33 and contracting it. As a result, the measuring means 43 measures the contracted dimension of the contact 431 and outputs the result to the control unit 50. The control unit 50 compares the contracted dimension of the contact 431 output by the measuring means 43 with a preset appropriate value, and if the contracted dimension of the contact 431 is the appropriate value, it is determined to be a good product, but if it is outside the appropriate value, it is determined to be defective.

As described above, the control unit 50 receives a signal from the measuring means 43 and extends the push-up cylinder 41, causing the push-up rod 42 to move out of the hanging groove 361. It then retracts the reciprocating cylinder 372. As a result, the hanging member 36, which has been held down by the piston rod of the reciprocating cylinder 372, moves from the inspection position toward the standby position. As shown in Figure 3(c), when the hanging member 36 reaches the standby position, the head of the screw N suspended and supported in the hanging groove 361 blocks the detection light of the detection sensor 35.

When the detection light of the detection sensor 35 is blocked as described above, the control unit 50 drives the linear arm 25 and the pivot arm 26 of the position control mechanism 24 to move the driver unit 20 above the standby position. Because the position control mechanism 24 is driven when the detection sensor 35 detects the screw N, the position control mechanism 24 can be prevented from being driven even if the driver unit 20 reaches the standby position without the screw N being supported by the suspension member 36, resulting in high efficiency. Furthermore, when the driver unit 20 reaches above the standby position, the control unit 50 drives the lift drive unit 27 to lower the driver unit 20 toward the screw N and drives the suction means to draw air from the lower end of the screw guide 23. Therefore, when the screw guide 23 descends to the suspension member 36, the screw N suspended and supported in the suspension groove 361 is suction-held within the screw guide 23. When the screw guide 23 adsorbs and holds the screw N in this manner, the control unit 50 drives the lifting drive unit 27, linear arm 25, and swivel arm 26 to move the driver unit 20 to a predetermined target position. At this time, if the screw N is a good product, as described above, the control unit 50 sets the target position to a predetermined screw fastening point on the workpiece and fastens the screw N into the workpiece. On the other hand, if the screw N is defective, the target position is switched to an external ejection position and the screw N is ejected. In this way, both good and defective screws N can be ejected from the component supply device 30.

Furthermore, as described above, when the screw N is removed from the hanging member 36 by the screw guide 23, the detection light of the detection sensor 35 is once again able to pass through. When the detection light is once again able to pass through, the control unit 50 retracts the reciprocating cylinders 371 and 372. This returns the hanging member 36 to the receiving position, and the hanging groove 361 reconnects with the chute rail 31, making it possible to receive the next row of screws N. Because the driver unit 20 is configured to remove the screw N from the hanging groove 361, there is no need to wait for the operator to remove the defective screw N, even if the screw N is defective. This extends the operating time of the screw fastening device 10 and improves work efficiency.

Furthermore, because the screw tightening device 10 is designed so that the driver unit 20 retrieves the screw N from the component supply device 30 as described above, there is no need to perform a process of pressurizing the screw N after measuring its length using the push-up means 40. This makes it possible to deliver to the driver unit 20 even screws that are difficult to pressurize, such as short screws that reverse inside the pressurized feed hose or plastic screws that may be damaged by the impact of being pressed. In particular, the control unit 50 is configured to switch and move the target point between the screw tightening point or an external discharge position based on the results of measuring the length of the screw N using the push-up means 40. This prevents screws of different lengths from being tightened even if they are mixed in, and also makes it possible to smoothly discharge any mixed screws.

The screw fastening device 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 position control mechanism 24 that moves the driver unit 20 is not limited to the linear arm 25, the swivel arm 26, and the lift drive unit 27 as in the present application, and other means may be used. Furthermore, while the screw fastening device 10 described above is configured to switch the target point between a predetermined screw fastening point or an external discharge position based on the length measurement results of the screw N, this is not limited to this configuration. It may also be configured to switch between a first screw fastening point and a second screw fastening point for each screw length, or to discharge mixed screws to different discharge positions depending on the length of the mixed screws. Furthermore, the reciprocating cylinders 371 and 372 are one example of a reciprocating drive source that reciprocates the hanging member 36 along the notch groove 332, and a ball screw mechanism or other reciprocating drive source may also be used. Similarly, the detection sensor 35 is not limited to an optical sensor, and may also be a proximity sensor or other sensor.

DESCRIPTION OF SYMBOLS 10 ... screw tightening device 20 ... driver unit 24 ... position control mechanism 30 ... component supply device 31 ... alignment conveying means 32 ... cutting unit 33 ... frame 34 ... regulating lid 35 ... detection sensor 36 ... hanging member 361 ... hanging groove 371, 372 ... reciprocating means 40 ... push-up means 41 ... push-up drive source 42 ... push-up rod 43 ... measuring means 50 ... control unit N ... fastening part

Claims (3)

a component supply device including a measuring means for measuring the length of a fastening component, and configured to make the fastening component wait at a predetermined waiting position after the length is measured by the measuring means; a driver unit for taking out the fastening component from the waiting position and fastening it to a workpiece; a position control mechanism for moving the driver unit; and a control unit configured to compare the measurement value of the measuring means with a preset value to determine whether the length of the fastening component is good or bad, and to control the drive of the position control mechanism based on the determination result;
A screw tightening device comprising : a detection sensor that detects a fastening component that has reached the standby position; and a reciprocating drive source that moves the hanging member based on a signal from the detection sensor . The screw tightening device described in claim 1, characterized in that the control unit controls the drive of the position control mechanism so as to move the driver unit to a predetermined fastening position when the length of the fastening part is good, and to move the driver unit to a predetermined ejection position when the length of the fastening part is bad. The screw tightening device described in claim 1 or 2, characterized in that the component supply device includes a hanging member that suspends and supports the fastening component, a push-up means that pushes the fastening component suspended from the hanging member from below upward, and a restricting lid that is fixed above the push-up means and restricts the fastening component pushed up by the push-up means from being pushed up beyond a predetermined height, the measuring means measures a dimension corresponding to the overall length of the fastening component restricted by the restricting lid, and the hanging member waits in a predetermined waiting position while supporting the fastening component in a suspended state after the measuring means measures the length of the fastening component.