Nut runner system

Nut runner system which includes holder table having tightening point at one end and coupling part at other end, and configured to hold plurality of bits, and nut runner main body including carrier coupled to wrist part of robotic arm, spindle supported by carrier, and bit changer coupled to spindle and which one of plurality of bits is attached. Coupling part of each of plurality of bits has an engaging hole coaxial with tightening point, and annular protrusion that continues in circumferential directions is formed in inner circumferential surface of engaging hole. Bit changer includes actuator, actuator made of engaging shaft to be inserted into engaging hole and operating pieces formed in engaging shaft, operating pieces moving between engaging position wherein operating pieces protrude radially outward from inner circumferential edge of annular protrusion and retracted position wherein operating pieces are retracted radially inward from inner circumferential edge of annular protrusion.

TECHNICAL FIELD

The present disclosure relates to a nut runner system for tightening a screw.

BACKGROUND ART

Conventionally, screws are tightened using a robot in, for example, an automated assembly line of various devices. For example, Patent Document 1 discloses a nut runner system in which a nut runner main body attached to a wrist part of a robotic arm is capable of mechanically equipped with one of a plurality of bits.

In more detail, as illustrated inFIG. 10, a nut runner main body100of the nut runner system disclosed in Patent Document 1 includes a bit changer110to which one of a plurality of bits160held by a holder table170(seeFIG. 11) is attached.

The bit changer110includes a hollow shaft120, an inner slide member130disposed inside the hollow shaft120, and an outside slide member140disposed outside the hollow shaft120. A plurality of notches121are formed at suitable locations of the hollow shaft120, and balls150are disposed inside the notches121, respectively. Moreover, recesses141into which the balls150fit are formed in the outside slide member140.

A recess161which opens radially outward is formed in an upper part of each bit160. When the upper part of the bit160is inserted into the hollow shaft120of the bit changer110, the inner slide member130is pushed by the bit160to move upwardly. Then, the balls150fit into the recess161and the outside slide member140moves downwardly. Therefore, the bit160is attached to the bit changer110.

In order to remove the bit160from the bit changer110, the outside slide member140is moved upwardly. Then, the balls150fit into the recesses141of the outside slide member140, and the bit160is able to be slipped out from the hollow shaft120. As illustrated inFIG. 11, a projection171is formed in the holder table170in order to move the outside slide member140upwardly.

REFERENCE DOCUMENT OF CONVENTIONAL ART

Patent Document

DESCRIPTION OF THE DISCLOSURE

Problems to be Solved by the Disclosure

However, in the nut runner system disclosed in Patent Document 1, as illustrated inFIG. 11, a position without the projection171of the holder table170is an attaching position P1of the bit160, and a position with the projection171is a removal position P2of the bit160. Therefore, in order to repeatedly use the same bit160, it is necessary to move the bit160from the removal position P2to the attaching position P1while maintaining by the robot in the state where the bit160is able to be slipped out from the hollow shaft120when removing the bit160from the bit changer110.

Therefore, the purpose of the present disclosure is to provide a nut runner system, which can attach and remove a bit at the same location of a holder table.

Summary of the Disclosure

In order to solve the above problem, according to one aspect of the present disclosure, a nut runner system is provided, which includes a holder table having a tightening point at one end and a coupling part at the other end, and configured to hold a plurality of bits, and a nut runner main body including a carrier coupled to a wrist part of a robotic arm, a spindle supported by the carrier, and a bit changer coupled to the spindle and to which one of the plurality of bits is to be attached. The coupling part of each of the plurality of bits has an engaging hole coaxial with the tightening point, and an annular protrusion that continues in circumferential directions is formed in an inner circumferential surface of the engaging hole. The bit changer includes an actuator, the actuator being comprised of an engaging shaft to be inserted into the engaging hole and operating pieces formed in the engaging shaft, the operating pieces moving between an engaging position at which the operating pieces protrude radially outward from an inner circumferential edge of the annular protrusion and a retracted position at which the operating pieces are retracted radially inward from the inner circumferential edge of the annular protrusion.

According to this structure, when the operating pieces are moved radially outward in a state where the engaging shaft of the actuator included in the bit changer is inserted into the engaging hole of the bit, the bit can be attached to the bit changer. On the other hand, when the operating pieces are moved radially inward, the bit can be removed from the bit changer. Therefore, the bit can be attached to and removed from the holder table at the same location.

The actuator may be driven by hydraulic pressure. The spindle may be of a tubular shape, and a tube through which the hydraulic pressure is supplied to the actuator may be routed inside the spindle. According to this structure, the tube for the actuator which is driven by the hydraulic pressure can be hidden inside the spindle near the bit changer.

The actuator may maintain the operating pieces at the engaging position when the hydraulic pressure is not supplied to the actuator through the tube, while the actuator may move the operating pieces to the retracted position when the hydraulic pressure is supplied to the actuator through the tube. According to this structure, a fall of the bit from the bit changer can be prevented even if the hydraulic pressure is no longer supplied to the actuator due to power failure etc.

The nut runner main body may include a guide that unrotatably fits to the spindle and supports the spindle so as to be axially slidable, a driven gear fixed to the guide, a drive gear that meshes with the driven gear, and a spring that biases the spindle toward the bit changer. According to this structure, it can prevent that the tightening point of the bit is pushed by an excessive force against a target screw to be tightened.

For example, a stop member may be fixed to an end of the spindle opposite from the bit changer. The nut runner main body may include a sleeve fixed to the carrier and fitted onto the spindle, and a collar that is rotatably supported by the sleeve through a bearing and contacts the stop member.

The coupling part of each of the plurality of bits may have a rotation-stop hole parallel to the engaging hole. The bit changer may have a rotation-stop pin to be inserted into the rotation-stop hole. According to this structure, the bit changer and the coupling part of the bit can be formed in simple shapes in which they contact each other with flat surfaces.

The holder table may have holder holes into which the plurality of bits are inserted, and the holder table may be constructed so that the coupling parts of the plurality of bits are placed on the holder table. The coupling parts of the plurality of bits may be of a disk shape, and at least two positioning slots may be formed in perimeter surfaces of the coupling parts at mutually different locations, respectively. The holder table may be provided, for each of the plurality of bits, with at least two positioning pins to be fitted into the at least two positioning slots. According to this structure, a faulty insertion of the bit into the holder hole by a worker is prevented.

Effect of the Disclosure

According to the present disclosure, the bit can be attached and removed at the same location of the holder table.

MODE FOR CARRYING OUT THE DISCLOSURE

FIG. 1illustrates a nut runner system1according to one embodiment of the present disclosure. This nut runner system1is for tightening a screw (e.g., a bolt with a hexagon socket), and includes a holder table6which holds a plurality of bits5and a nut runner main body11. Note that, inFIG. 1, although the holder table6is drawn directly under a wrist part10of the robotic arm for convenience of drawing, the exact location of the holder table6is below a bit changer4(described later).

The nut runner main body11includes a carrier2coupled to the wrist part10of the robotic arm, a spindle3which is supported by the carrier2and extends in vertical directions, and the bit changer4coupled to the spindle3. One of the plurality of bits5is to be attached to the bit changer4.

As illustrated inFIGS. 1 to 3, the carrier2includes a top plate21having a substantially rectangular shape parallel to a horizontal plane, a pedestal22for connecting with the wrist part10of the robotic arm, which is fixed to an upper surface on one end side of the top plate21(right side inFIGS. 1 and 2), and a housing23fixed to an undersurface on the other side of the top plate21. The spindle3penetrates the housing23and the top plate21.

A motor12which rotates the spindle3is attached to the top plate21through a transmission13. An output shaft14of the transmission13is located inside the housing23, and a drive gear15is fixed to the output shaft14.

In this embodiment, the spindle3is configured to be axially movable with respect to the carrier2. Specifically, a guide31is disposed inside the housing23. The guide31fits onto the spindle3so as not to be rotatable and supports the spindle3so as to be axially slidable. The spindle3and the guide31are, for example, a ball-spline mechanism.

A driven gear16which meshes with the drive gear15described above is disposed above the guide31. The driven gear16is fixed to the guide31by pinching the guide31with a cylindrical fixing member32which accommodates the guide31. The fixing member32is rotatably supported by the housing23through a pair of bearings33.

Furthermore, in this embodiment, the spindle3is biased toward the bit changer4by a spring85disposed at the side of the motor12. As illustrated inFIG. 4, a stop member75is fixed to an end of the spindle3opposite from the bit changer4. An upper part of the stop member75is rotatably supported by a cylindrical member82through a pair of bearings81. A spring receiving plate83is fixed to an upper end of the cylindrical member82, and a projection84which guides the spring85is formed in the spring receiving plate83. On the other hand, a spring receiving plate86is disposed above the spring85. The spring receiving plate86is fixed to the top plate21with four pillars87. Note that, although illustration is omitted, a projection which guides the spring85is also formed in the spring receiving plate86.

The stop member75normally contacts, by a biasing force of the spring85, a collar74of which a relative position with respect the top plate21of the carrier2remains unchanged. A sleeve71which is fitted onto the spindle3is fixed to the top plate21. A cylindrical member72is fixed to the sleeve71so as to extend upwardly from a perimeter edge portion of the sleeve71. A bearing73is disposed between the cylindrical member72and the collar74. In other words, the collar74is rotatably supported by the sleeve71through the bearing73and the cylindrical member72.

As illustrated inFIGS. 5 and 6, the bit changer4described above includes a vertically-extending cylindrical bit changer main body41, and an actuator9attached to an undersurface of the bit changer main body41. A recess46is formed in an upper surface of the bit changer main body41, and a lower part of the spindle3is inserted into the recess46.

The actuator9includes a main body91embedded into the bit changer main body41, an engaging shaft92projecting downwardly from the main body91, and a plurality of operating pieces93(although three pieces in the illustrated example, two or four or more pieces are also possible) formed in the engaging shaft92. In this embodiment, the actuator9is hydraulically driven (may be pneumatically driven or may be driven by the hydraulic oil). Thus, the spindle3is tubular, and a tube35which supplies hydraulic pressure to the actuator9is routed inside the spindle3.

A channel42for operating fluid having the hydraulic pressure described above is formed in the bit changer main body41so that the channel42extends from the actuator9to the bottom of the recess46. A connector43is provided to an upper end of the channel42. A lower end of the tube35is connected to the connector43.

As illustrated inFIG. 4, a channel76for operating fluid is also formed in the stop member75, on the centerline of the stop member75, and connectors77and78are provided to a lower end and an upper end of the channel76, respectively. An upper end of the tube35is connected to the lower connector77, and a tube (not illustrated) which penetrates the cylindrical member82is connected to the upper connector78.

Returning toFIGS. 5 and 6, the operating pieces93are balls in this embodiment. Note that the actuator9may have only one ring-shaped operating piece.

The operating pieces93radially move between a retracted position where the operating pieces93are accommodated in the engaging shaft92and an engaging position where the operating pieces93protrude from the engaging shaft92. In this embodiment, the actuator9maintains the operating pieces93at the engaging position when the hydraulic pressure is not supplied to the actuator9through the tube35, while the operating pieces93are moved to the retracted position when the hydraulic pressure is supplied to the actuator9through the tube35.

Specifically, as illustrated inFIG. 7, the main body91and the engaging shaft92are hollow, and a pressure-receiving member94is disposed inside the main body91and the engaging shaft92. The pressure-receiving member94includes a tip-end part94afor maintaining the operating pieces93at the engaging position, and a recess94bfor moving the operating pieces93to the retracted position. The pressure-receiving member94is normally pushed against the bit changer main body41by a spring95so that the tip-end part94acontacts the operating pieces93. On the other hand, when the hydraulic pressure acts on the back side of the pressure-receiving member94through the channel42, the pressure-receiving member94goes up and the operating pieces93fits into the recess94b.

As illustrated inFIG. 1, each bit5described above has a tightening point51at one end (lower end), a coupling part52at the other end (upper end), and a main body58at the center. In this embodiment, as illustrated inFIGS. 8 and 9, the coupling part52is of a disk shape having a diameter larger than that of the main body58.

Holder holes61are formed in the holder table6described above, into which the plurality of bits5are inserted, respectively. Diameter of the holder hole61is smaller than the diameter of the coupling part52. Thus, the coupling parts52of the plurality of bits5are placed on the holder table6.

At least two positioning slots56(three slots in the illustrated example) are formed at mutually different locations of a perimeter surface of the coupling part52of each of the plurality of bits5. On the other hand, at least two positioning pins62(three pins in the illustrated example) which fit into the positioning slots56are formed in the holder table6, corresponding to each bit5. Thus, a faulty insertion of the bit5into the holder hole61by a worker is prevented. Note that, since the positioning pin62is shared by the adjacent bits5, the total number of positioning pins62are not nine but seven.

An engaging hole53is formed in the coupling part52of each bit5so as to be coaxial with the tightening point51. An annular protrusion54which continues in circumferential directions is formed in an inner circumferential surface of the engaging hole53. The engaging shaft92of the actuator9described above is inserted into the engaging hole53. Moreover, the engaging position of the operating pieces93described above is a position at which the operating pieces93protrude radially outward from the inner circumferential edge of the annular protrusion54, while the retracted position described above is a position at which the operating pieces93are retracted radially inward from the inner circumferential edge of the annular protrusion54.

Furthermore, two rotation-stop holes55parallel to the engaging hole53are formed in the coupling part52of each bit5. Note that only one rotation-stop hole55may be formed. On the other hand, as illustrated inFIGS. 5 and 6, two rotation-stop pins45which are inserted into the rotation-stop holes55, respectively, are formed in the undersurface of the bit changer main body41.

Note that, as illustrated inFIG. 9, a screw stud57is integrally formed with the coupling part52of each bit5, and the main body58threadedly engages with the screw stud57. Furthermore, a fixing nut59which fixes the main body58threadedly engages with the screw stud57.

According to the structure of this embodiment, when the operating pieces93are moved radially outward in a state where the engaging shaft92of the actuator9included in the bit changer4is inserted into the engaging hole53of the bit5, the bit5can be attached to the bit changer4. On the other hand, when the operating pieces93are moved radially inward, the bit5can be removed from the bit changer4. Therefore, the bit5can be attached to and removed from the holder table6at the same location.

Moreover, in this embodiment, since the tube35is routed inside the tubular spindle3, the tube35for the actuator9which is driven by the hydraulic pressure can be hidden inside the spindle3near the bit changer4.

Furthermore, in this embodiment, since the operating pieces93move from the engaging position to the retracted position when the hydraulic pressure is supplied to the actuator9, a fall of the bit5from the bit changer4can be prevented even if the hydraulic pressure is no longer supplied to the actuator9due to power failure etc.

Moreover, in this embodiment, since the spindle3capable of moving axially is biased toward the bit changer4, it can prevent that the tightening point51of the bit5is pushed by an excessive force against a target screw to be tightened.

MODIFICATION

The present disclosure is not limited to the embodiment described above but various modifications are possible without departing from the spirit of the present disclosure.

For example, the spindle3is not necessarily constructed so as to be axially movable with respect to the carrier2, but a relative position between the spindle3and the carrier2in the axial directions of the spindle3may be fixed.

Moreover, the rotation-stop structure of the bit5with respect to the bit changer4is not necessary to be the rotation-stop holes55and the rotation-stop pins45. For example, an upper surface of the coupling part52of the bit5and an undersurface of the bit changer main body41may be formed so as to be unrotatably engaged with each other. Note that, if the rotation-stop holes55and the rotation-stop pins45are used like the embodiment, the bit changer main body41and the coupling part52of the bit5can be formed in simple shapes in which they contact each other with flat surfaces.

Moreover, the actuator9is not necessary to be driven by the hydraulic pressure but it may be driven by a solenoid, for example.

DESCRIPTION OF REFERENCE CHARACTERS