Screw tightening device

Abstract

This screw tightening device enhances safety by preventing the driver bit from protruding from the tip of the screw guide in any position other than the normal tightening start position. [Solution] The screw tightening device 10 consists of a screw tightening tool 30 equipped with a driver bit 34 at its tip that rotates in conjunction with the drive of a motor 32, and a robot equipped with a robot arm 21 that supports the screw tightening unit 30 and moves it up and down. The screw tightening tool 30 is configured to move in the upward direction relative to the downward movement of the robot arm 21. With this screw tightening device, even if a worker's hand is caught between the driver bit of the screw tightening tool and the workpiece, excessive load is not placed on the worker's hand, so it does not lead to serious injury and the safety of the work can be improved.

Description

Technical Field

[0001] The present invention relates to a screw tightening device that enhances the safety of workers.

Background Art

[0002] The screw tightening machine shown in Patent Document 1 includes a tip-shaped driver bit that can engage with the head of a screw, a motor that rotationally drives this driver bit, and a cylindrical screw guide that always encloses the driver bit. The screw guide is configured to suck air from its tip and is capable of sucking in a screw prepared at a predetermined position. Also, the screw guide is configured to be able to move forward and backward in the axial direction with respect to the driver bit, and is normally biased by a spring so that its tip protrudes forward from the tip of the driver bit. As a result, the tip of the driver bit is always housed inside the screw guide. During the screw tightening operation, when the screw guide hits the workpiece, thereafter the driver bit advances inside the screw guide. Thereby, it becomes possible to push out the screw from the screw guide and tighten it to the workpiece.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The screw tightening machine described in Patent Document 1 is used by being attached to an articulated robot or the like. In recent years, in particular, it has become increasingly common to use it mounted on collaborative robots that support work in the vicinity of an operator. In environments where such collaborative robots are mounted, unlike fully automated environments, operators often work in the vicinity of the collaborative robot, and unexpected objects may be placed around the collaborative robot. As a result, when the collaborative robot is in operation, the screw guide may come into contact with something other than the workpiece and retract, causing the tip of the screw or driver bit to protrude from the screw guide. Some screws and driver bits have sharp tips, and operators often work in the vicinity of the collaborative robot, so it is unsafe for screws or driver bits to protrude from the screw guide in an unexpected location. Furthermore, if the driver bit protrudes from the screw guide in an unexpected location, the screw may be pushed out of the screw guide and fall out, making it impossible to perform the screw tightening work.

[0005] The present invention aims to provide a screw tightening device that enhances worker safety by reducing the load on the screw tightening tool when a worker's hand or other body part gets caught between the screw tightening tool and the workpiece, thereby preventing serious accidents. [Means for solving the problem]

[0006] The above problem can be solved by a screw tightening device comprising a screw tightening tool having a driver bit at its tip that rotates in conjunction with the drive of a motor, and a robot having a robot arm that supports the screw tightening tool and moves it up and down, wherein the screw tightening tool is supported by the robot arm via a buffer mechanism, and the screw tightening device is configured to be movable relative to the up and down direction of the robot arm. Preferably, the screw tightening tool is covered by a protective case with the driver bit protruding downwards, and this protective case is fixed to the robot arm. Preferably, the buffer mechanism is a first air cylinder, and when a predetermined load is applied to the tip of the screw driver bit of the screw tightening tool, the first air cylinder retracts, causing the screw tightening tool to move upward relative to the downward movement of the robot arm, thereby preventing the load associated with the downward movement of the robot arm from being applied to the screw tightening tool. Furthermore, when tightening a screw, it is preferable that the first air cylinder is fixed in a fully advanced stroke position, and the robot arm and screw tightening tool descend together, so that the load associated with the descent of the robot arm is applied as thrust to the screw that fits into the tip of the driver bit via the screw tightening tool. Furthermore, the above problem can also be solved by a screw tightening device comprising a screw tightening tool having a driver bit at its tip that rotates in conjunction with the drive of a motor, and a robot having a robot arm that supports the screw tightening tool and moves it up and down, wherein the screw tightening tool is equipped with a screw guide that encloses the driver bit and is capable of drawing a screw into it, and this screw guide is always biased toward the tip of the driver bit to enclose the driver bit, and its retraction is always restricted by a second air cylinder, and when the tip of the screw guide comes into contact with an object and reaches a predetermined screw tightening start position, the restriction of the retraction of the screw guide by the second air cylinder is released, and as the screw tightening tool descends, the screw guide retracts against the biasing force toward the driver bit, so that the driver bit protrudes from the tip of the screw guide and screw tightening begins, while if the tip of the screw guide comes into contact with an object at a position other than the predetermined screw tightening start position, the restriction of the retraction of the screw guide by the second air cylinder is continued. [Effects of the Invention]

[0007] According to the present invention, since the screw tightening tool is supported by the robot arm via a buffer mechanism, the screw tightening tool is movable relative to the vertical direction of the robot arm. Therefore, if the driver bit strikes the worker's body or an obstacle, the screw tightening tool moves upward relative to the downward movement of the robot arm, which has advantages such as preventing the load associated with the downward movement of the robot arm from being transmitted to the worker or obstacle via the screw tightening tool. Furthermore, in a configuration where the screw tightening tool includes a screw guide that encloses a driver bit and is capable of drawing the screw in, if the tip of the screw guide comes into contact with an object at a position other than the predetermined screw tightening start position, the driver bit is not configured to protrude from the tip of the screw guide. This has the advantage of preventing the tip of the driver bit from piercing the worker's hand if the worker's hand gets caught between the tip of the screw guide of the screw tightening tool and the workpiece. Based on the above, the screw tightening device of the present invention can enhance safety for workers and surrounding objects even in environments where workers are working nearby, and can reliably carry screws to the designated screw tightening position without dropping them, thereby enabling reliable screw tightening. [Brief explanation of the drawing]

[0008] [Figure 1] This is a side view showing the structure of a screw tightening device according to the present invention. [Figure 2] This is a side view showing the structure of the screw tightening tool according to the present invention. [Figure 3] This is an enlarged side view showing the structure of the screw tightening tool according to the present invention. [Figure 4] This is a partial cross-sectional side view showing the operation of the screw tightening device according to the present invention. [Figure 5] This is a partial cross-sectional side view showing the state after transitioning from Figure 3 to the next operation. [Figure 6] This is a partial cross-sectional side view showing the screw tightening device according to the present invention in contact with a foreign object. [Modes for carrying out the invention]

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In Figure 1, 10 is a screw tightening device for tightening a screw S onto a workpiece W, and includes an articulated robot 20, which is an example of a robot, a screw tightening tool 30 that moves under the drive of the articulated robot 20, and control means (not shown) for controlling the drives of these.

[0010] In this embodiment, the screw S is a general-purpose screw S in which a head with a Phillips-shaped drive hole and a shaft portion with threads on its outer surface are integrally formed, and is configured to be screwed into the female thread formed in the workpiece W.

[0011] The articulated robot 20 has a robot arm 21 comprising a plurality of arm sections 221 and a plurality of joint sections 222 connecting these arm sections 221. The joint sections 22 of the articulated robot 20 are provided with an arm swing drive source (not shown) that swings the arm section 221 around the joint section 222 and an arm rotation drive source (not shown) that rotates the arm section 221 around the joint section 222. These drive sources are connected to the control means, and their drive is controlled by the control means. In addition, a support base 23 that supports the screw tightening tool 30 is connected to the tip of the robot arm 21 of the articulated robot 20. Therefore, by driving the articulated robot 20, the position and orientation of the screw tightening tool 30 supported by the robot arm 21 can be moved arbitrarily, and the screw tightening tool 30 can be raised and lowered in conjunction with the raising and lowering of the robot arm 21.

[0012] The support base 23 is provided with a buffer mechanism 24 that supports the screw tightening tool 30. This buffer mechanism 24 has a first air cylinder fixed to the support base 23, which is a table-type air cylinder 241. This table-type cylinder 241 has a slide table 242 that can reciprocate vertically in conjunction with an internal piston (not shown), and the screw tightening tool 30 is fixed to this slide table 242. Therefore, the screw tightening tool 30 can move relative to the tip of the robot arm 21 by the stroke of the table-type cylinder 241. In addition, the table-type cylinder 241 constantly pulls the slide table 242 upward with a force slightly less than the weight of the screw tightening tool 30. Therefore, as shown in Figure 2, the table-type cylinder 241 is in a full stroke state where the slide table 242 is at the bottom dead center due to the weight of the screw tightening tool 30.

[0013] With the above configuration, a stroke is secured that allows the screw tightening tool 30 to move upward. As shown in Figure 6, the screw tightening tool 30 descends as the robot arm 21 descends, and when the tip of the screw guide (described in detail later) strikes the operator's hand H, etc., and the robot arm 21 is lowered further, the slide table 242 of the table-equipped cylinder 241 moves towards the top dead center, so the screw tightening tool 30 moves relative to the robot arm 21. Therefore, the load associated with the descent of the robot arm 21 is not transmitted to the screw tightening tool 30, so there is no risk of excessive load being placed on the operator's hand H and causing injury. In addition, the weight of the screw tightening tool 30 is offset to some extent by the table-equipped cylinder 241, so the operator hardly feels the weight of the screw tightening tool 30.

[0014] Furthermore, the table-equipped cylinder 241 is provided with a pair of non-contact sensors 251 and 252 capable of detecting the position of the screw tightening tool 30. As shown in Figure 6, the sensors are configured to detect when the screw tightening tool 30 has moved upward relative to the robot arm 21 and to output a stop signal to the control means.

[0015] Furthermore, a protective case 26 for covering the screw tightening tool 30 is fixed to the support base 23. This protective case 26 is composed of a support fitting 261 fixed to the support base 23, an upper cylindrical portion 262 and a lower cylindrical portion 263 fixed to this support fitting 261. These upper cylindrical portion 262 and lower cylindrical portion 263 are each a capsule-shaped hollow member made of resin or the like, and their ends are sealed by a lid portion. Further, a hole through which the screw guide 36 can penetrate is formed in the lid portion of the lower cylindrical portion 263, and the tip of the screw guide 36 protrudes to the outside through this hole. Therefore, the protective case 26 moves integrally with the support base 23 of the multi-joint robot 20.

[0016] Also, a holding plate 271 extending toward the lid portion of the upper cylindrical portion 262 is fixed to the support base 23, and a cable holding means 272 is fixed to this holding plate 271 so as to penetrate the upper cylindrical portion 262. This cable holding means 272 is configured in a cylindrical shape, and cables (not shown) such as electrical wiring connecting the screw tightening tool 30 and the control means and air pipes connected to the intake means and the intake and exhaust means described later penetrate therethrough.

[0017] The screw tightening tool 30 has a housing 31 fixed to the slide table 242 of the cylinder 241 with a table. This housing 31 is a hollow member in which a through hole extending parallel to the sliding direction of the slide table 242 of the cylinder 241 with a table is formed, and an AC servo motor 32 (hereinafter referred to as a tightening motor 32) is placed on its upper surface as shown in FIG. 4.

[0018] As shown in FIG. 3, the output shaft of the tightening motor 32 is provided so as to be inserted into the housing 31, and a shaft coupling 33 is integrally and rotatably mounted on the output shaft. A driver bit 34 that can be fitted to the drive hole of the screw S is connected to this shaft coupling 33. Therefore, when the tightening motor 32 is driven, these shaft coupling 33 and driver bit 34 rotate integrally with the output shaft.

[0019] Further, the screw tightening tool 30 has a holding sleeve 35 fixed to the front surface of the housing 31. A hollow cylindrical screw guide 36 that rotatably houses the driver bit 34 is inserted into the holding sleeve 35 so as to be axially relatively movable. The screw guide 36 is continuous with a hose joint 361. An intake hose (not shown) is connected to the hose joint 361, and an intake means (not shown), such as an external vacuum generator, is connected to the other end of the intake hose. Therefore, when the intake means is driven, the inside of the screw guide 36 becomes negative pressure, and the screw S can be adsorbed and held at the front end opening of the screw guide 36.

[0020] The screw guide 36 is constantly biased forward by a guide spring 362 enclosed therein, and is configured to be axially relatively movable with respect to the holding sleeve 35 and the driver bit 34 while the guide spring 362 is bent.

[0021] Furthermore, the screw tightening tool 30 is provided with a regulating means 37 for regulating the backward movement of the screw guide 36 against the biasing force of the guide spring 362. The regulating means 37 includes a ring-shaped contact portion 371 fixed to the outer periphery of the screw guide 36 and an air cylinder 372 which is a second air cylinder fixed to the housing 31. A pressing portion 373 capable of pressing the contact portion 371 toward the front end side in the front end direction of the driver bit 34 is connected to the tip of the cylinder rod of the air cylinder 372. Therefore, when the cylinder rod of the air cylinder 372 is in the full stroke state, the backward movement of the screw guide 36 is regulated, so that the screw S and the driver bit 34 do not protrude from the tip portion thereof. The air cylinder 372 is fixed in the full stroke state unless the screw tightening can be properly started.

[0022] The control means is connected to the articulated robot 20 and the screw tightening tool 30, as well as intake and exhaust means (not shown) for driving the table-mounted air cylinder 241 and the air cylinder 372, and intake means for drawing air into the screw guide 36, and is configured to control the driving of these components. Furthermore, when the screw tightening tool 30 reaches a predetermined screw tightening start position, the control means is configured to drive the intake and exhaust means, contract the air cylinder 372, and apply high air pressure to the table-mounted cylinder 241, thereby fixing the table-mounted cylinder 241 in a full stroke state.

[0023] Next, the operation of the screw tightening device 10 configured as described above will be explained. The screw tightening device 10, configured as described above, receives a drive from the control means and moves the screw tightening tool 30 back and forth between a predetermined screw supply position and a screw tightening start position. At this time, the air cylinder 372 presses the screw guide 36 in the forward direction, preventing the screw guide 36 from moving backward. As a result, as shown in Figure 6, the screw guide 36 does not move backward even if it comes into contact with a person or a foreign object in the surrounding area, and the driver bit 34 and screw S do not protrude from its tip. This prevents the relatively sharp driver bit 34 and screw S from injuring a person or a surrounding object. In addition, since the screw S does not protrude from the screw guide 36, it is also possible to prevent the screw S from falling out during transport.

[0024] Furthermore, since the screw tightening tool 30 is supported by the table-equipped cylinder 241, if the screw guide 36 comes into contact with a person or surrounding object and is biased upward, the screw tightening tool 30 is retracted upward. This mitigates the impact when the screw guide 36 comes into contact with a person or surrounding object, preventing damage to the device and the object it comes into contact with. Moreover, as the screw tightening tool 30 retracts upward, the distance between the distance sensors 251 and 252 increases, causing the distance sensors 251 and 252 to send a stop signal to the control means. This allows the control means to detect that the screw guide 36 has come into contact with a person or surrounding object and immediately stop the articulated robot 20 from moving. As a result, the articulated robot 20 can be stopped before the screw tightening tool 30 reaches the top dead center of the stroke of the table-equipped cylinder 241. With these configurations, it is possible to prevent the screw guide 36 from being pushed into the object it comes into contact with and damaging that object, allowing workers to work safely even in the vicinity of the screw tightening device 10.

[0025] Furthermore, the screw tightening device 10 has a cylindrical protective case 26 covering the screw tightening tool 30. Therefore, even if the side of the screw tightening tool 30 collides with the worker during movement, the worker is less likely to be injured. Thus, the screw tightening device 10 of the present invention can enhance safety for workers and surrounding objects, even in environments where workers are working nearby.

[0026] As shown in Figure 4, when the screw tightening tool 30 reaches a predetermined screw tightening start position, the control means retracts the air cylinder 372 and fixes the table cylinder 241 in the full stroke position. When the air cylinder 372 retracts in this way, the pressing portion 373 separates from the contact portion 371, and the retraction restriction is released. This allows the screw guide 36 to retract. In addition, when the table cylinder 241 is fixed in the full stroke position, the position of the screw tightening tool 30 relative to the support base 23 of the articulated robot 20 is fixed.

[0027] Subsequently, the control means drives the articulated robot 20 to press the screw tightening tool 30 toward the workpiece W, and drives the tightening motor 32 to rotate the driver bit 34 and start the screw tightening operation. At this time, since the screw guide 36 is retractable, the driver bit 34 and the screw S can advance inside the screw guide 36 and protrude from its tip. As a result, the screw S can be tightened into the workpiece W as shown in Figure 5. Also, since the screw tightening tool 30 is fixed to the support base 23, the articulated robot 20 can apply a predetermined screw tightening load to the screw tightening tool 30. These measures prevent cam-out and deformation of the workpiece due to excessive or insufficient screw tightening load. As a result, high-precision screw tightening becomes possible.

[0028] Furthermore, the specific configuration of each part of the present invention is not limited to those described above, and various modifications are possible without departing from the spirit of the invention. For example, the distance sensors 251 and 252 are not limited to non-contact types, but may be contact-type sensors. Also, the articulated robot 20 may be other robots such as orthogonal robots, as long as it is capable of moving the screw tightening tool 30 in the axial direction of the driver bit 34. The cushioning mechanism 24 may be a regular air cylinder or an air cylinder with a damper function instead of a table-type air cylinder 241, and there is no problem with that. [Explanation of Symbols]

[0029] 10 ... Screw tightening device 20… Articulated robot 23 … Support stand 24 … Buffer mechanism 241… First air cylinder (cylinder with table) 242… Sliding table 251,252… Distance sensors 26… Protective case 30… Screw tightening tool 32… Tightening motor 34… Driver Bit 36… Screw guide 362… Guide spring 37… Regulatory measures 371... Contact part 372... Second air cylinder (air cylinder) 373... Pressing part S... screw

Claims

1. A screw tightening device comprising a screw tightening tool having a driver bit at its tip that rotates in conjunction with the drive of a motor, and a robot equipped with a robotic arm that supports the screw tightening tool and moves it up and down, The screw tightening device is characterized in that the screw tightening tool is supported by the robot arm via a buffer mechanism, thereby enabling the screw tightening tool to move in an upward direction relative to the downward movement of the robot arm.

2. The screw tightening device according to claim 1, characterized in that the screw tightening tool is covered by a protective case with the driver bit protruding downward, and the protective case is fixed to the robot arm.

3. The aforementioned buffer mechanism is a first air cylinder, The screw tightening device according to claim 1 or 2, characterized in that when a predetermined load is applied to the tip of the driver bit of the screw tightening tool, the first air cylinder retracts, and the screw tightening tool moves in an upward direction relative to the downward movement of the robot arm, thereby preventing the load associated with the downward movement of the robot arm from being applied to the screw tightening tool.

4. The screw tightening device according to claim 3, characterized in that when tightening a screw, the first air cylinder is fixed in a fully advanced stroke position, and the robot arm and the screw tightening tool descend together, so that the load accompanying the descent of the robot arm is applied as thrust to the screw fitted to the tip of the driver bit via the screw tightening tool.

5. A screw tightening device comprising a screw tightening tool having a driver bit at its tip that rotates in conjunction with the drive of a motor, and a robot equipped with a robotic arm that supports the screw tightening tool and moves it up and down, The screw tightening tool includes a screw guide that encloses a driver bit and is capable of drawing a screw into it, and this screw guide is always biased toward the tip of the driver bit to enclose the driver bit, and its retraction movement is always restricted by a second air cylinder. When the tip of the screw guide contacts an object and reaches the predetermined screw-tightening start position, the retraction restriction of the screw guide by the second air cylinder is released, and as the screw-tightening tool descends, the screw guide retracts against the biasing force relative to the driver bit, causing the driver bit to protrude from the tip of the screw guide and begin screw-tightening. A screw tightening device characterized in that, if the tip of the screw guide comes into contact with an object at a position other than the predetermined screw tightening start position, the retraction restriction of the screw guide by the second air cylinder is continued.

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