Patent Application
20190061154
This application relates generally to linear actuators and in particular to high-speed linear actuator and thruster systems. More specifically, the application is directed to high-speed, rod-style linear actuators, suitable for use in parts handling, manufacturing, and other industrial processes.
Linear actuator and thruster systems include both rod-type actuators and rodless designs, utilizing a range of different pneumatic cylinders, electric motors and magnetically coupled drives to provide the desired load capacity and actuation speed. A variety of bearing styles are also known, which can be adopted to light, moderate and heavy loading applications, accordingly.
Rod-style actuator implementations include, but are not limited to, short-stroke devices for use in welding, machining, and other manufacturing processes. Pneumatic cylinder and screw-driven rod-type actuators can also be configured with guide rods and mounting blocks, for increased load weight and extension. Rodless (e.g., rail and carriage) systems can be provided in longer-stroke configurations, or where space savings is a concern.
Actuator weight and complexity are important design considerations, across a wide range of system configurations. Cost concerns are also relevant, and there are constant demands for improved actuator speed and precision automated control, which are not met by existing actuator system designs.
An actuator and part placement system is adapted to position parts at one or more selected locations. Depending on application, the part placement system can includes a linear actuator with a probe or similar placement tool connected to or integrated onto the end of an output rod. The part placement system disposes parts with respect to one or more part receiving fixtures; e.g., by placing the parts onto a tapered weld pin or post adapted to receive a weld nut or similar mechanical element, or into a cavity or recess feature adapted to accept the part. The part can then be attached to the desired location on a sheet metal component or other workpiece, for example by resistance welding or other machine process.
The actuator can include a controller adapted to modulate the acceleration of the output rod and probe toward the positioning fixture, together with one or more parts, so that the acceleration is greater than the gravitational acceleration acting on the part, and the part remains on the probe. To dispense the part from the probe to the receiving element, the actuator can decelerate the rod or reduce the acceleration to a suitably low value (below the longitudinal component of the gravitational acceleration), so the part is released from the probe and engaged with the weld pin or other receiving fixture.
This application is also directed to a high-speed, belt-driven, rod-style linear actuator system, which is adapted for part placement. The actuator system can include a belt drive and piston member disposed within a housing, and configured to position the output rod for placing a part with respect to a workpiece. For example, the output rod can be provided with a part placement tool or probe adapted to position a weld nut on a weld pin, for resistance welding to a sheet metal component.
FIG.12 is a block diagram illustrating a method for part placement.
This disclosure relates to linear actuators and part placement systems that include actuator devices. Suitable part placement systems can be configured with an actuator rod adapted to position parts with respect to a weld electrode or locating fixture; e.g., for attachment to a selected location on a workpiece. In some embodiments, the part placement system includes a probe or similar part placement tool connected to or integrated onto the end of the output rod, and configured for cyclical engagement and placement of such parts.
The part placement system can be adapted to dispense parts onto one or weld pins for resistance spot welding, projection welding, and other machine processes. For example, the actuator may accelerate the output rod and probe together with one or more parts toward the weld pin or part-receiving fixture, so that the acceleration of the part is greater than the gravitational acceleration acting along the rod direction, maintaining the part on the end of the output rod. To release the part from the probe to the fixture, the actuator can decelerate the output rod or reduce its acceleration to a suitably low value, below the longitudinal component of the gravitational acceleration, so that the part continues to move along the rod axis and off the end of the probe to engage the locating fixture. In practice the output rod can decelerate to a momentary stop for placing and releasing the part, and then change direction to engage another part and repeat the placement cycle.
Suitable implementations include belt-driven linear actuator systems. Some of these embodiments relate to U.S. patent application Ser. No. 15/552,855, HIGH SPEED ROD-STYLE LINEAR ACTUATOR, filed Aug. 23, 2017, which is incorporated by reference herein, in the entirety and for all purposes.
More generally, the system can position and dispense a number of suitable part types and components, of different sizes and shapes. For example, the system may dispense generally round, hollow parts, such as nuts or other resistance spot welding components. In some embodiments, the weld pin may include a tapered top projection configured to receive the nut or other hollow part, and a probe or similar part placement tool can be operably connected to the actuator to carry the part. A controller can be configured to operate the actuator to position the probe near a weld pin or other placement fixture, in a manner that facilitates sliding movement of the part relative to the probe to release the part and position the part in engagement with the weld pin or other fixture.
Actuator housing 14 extends from motor mount 16 at proximal end 17 to distal end 18, axially or longitudinally opposite proximal end 17. The external part of thrust rod or output rod 20 extends outward from distal end 18 of actuator housing 14, and can be provided with a tooling interface for positioning a part or workpiece, as described herein.
A piston-type coupling member 30 is disposed within actuator housing 14 along longitudinal axis or centerline CL. Drive belt 24 is configured to drive piston member 30 in reciprocal motion along axis CL, with output rod 20 having a first end 21 coupled to piston member 30, opposite second end 22. The second (exterior) end 22 of output rod 20 is selectively positionable outside the distal (front) end 18 of actuator housing 14, in response to the reciprocal motion of output rod 20 along axis CL. Drive belt 24 is coupled to drive pulley 26 at the back (proximal) end 17 of actuator housing 14, and to idler pulley 28 in the front end 18, opposite drive pulley 26.
More generally, any suitable belt drive system can be configured to reciprocally drive piston coupling 30 along longitudinal axis CL of actuator housing 14 according to any of the embodiments herein; e.g., with piston 30 coupled to a selectively positionable off-axis output rod 20, as described above. In one design, a continuous timing belt 24 is operated by a drive pulley 26 rotationally coupled to an electric servomotor, DC motor or stepper motor 12, which is configured to selectively position distal end 22 of output rod 20 with respect to front end 18 of actuator housing 14. For example, timing belt 24 can be coupled to and between a drive pulley 26 and idler pulley 28 disposed along longitudinal axis CL of housing 14, with output rod 20 positioned above timing belt 24, in a generally parallel off-axis configuration.
The output rod 20 is coupled to drive belt 24 via a piston-type coupling member 30, for example by seating first (proximal) end 21 into an axial cavity in the upper portion of coupling member (drive member or piston) 30, using a screw or other mechanical coupling for thrust rod attachment 32. A toothed timing belt or drive belt 24 can be utilized in the drive system; e.g., with a plurality of inwardly or outwardly-projecting teeth configured for engagement with complementary features on belt clamp 34. Belt clamp 34 is mechanically fastened to or within the body of coupling member 30, for example attaching the top or upper portion of drive belt 24 to the inner surface of coupling member 30, as shown in
Wear rings or other sliding engagement members 36 are provided between the outer radius (or other outer surface) of coupling member 30 and the inner radius (or inner surface) of the actuator main body (e.g., tube or cylinder) housing 14. Suitable materials for wear rings 36 include durable polymers, metals, and composite materials, selected for providing a sliding engagement between piston or coupling member 30 and the inner surface of actuator housing 14. Alternatively, discrete wear members 36 can be provided on the outer circumference of the piston or other coupling member 30, or on the inner surface of actuator housing 14 (e.g., in rail form).
In operation, drive belt 24 is engaged to urge or move coupling member 30 and output rod 20 back and forth in an axial or longitudinal fashion within the actuator housing or tube 14, when drive belt 24 is engaged in corresponding back-and-forth motion between drive pulley 26 and idler pulley 28. A tapped hole or other tooling engagement feature 38 is provided in or on the distal end of output rod 20, in order to position a tool or workpiece longitudinally with respect to linear actuator housing 14.
In the configuration of
Alternatively, output rod 20 can be positioned above, below, or to either side of drive belt 24. In addition, either the top or bottom portion of drive belt 24 can be engaged with coupling member 30, and the back-and-forth motion of output rod 20 can be reversed with respect to the corresponding clockwise and counter-clockwise rotation of pulleys 26 and 28.
In some designs, actuator housing 14 is formed as a cylinder, or has a cylindrical or elliptical bore having a substantially circular or oval cross section, with a similarly-shaped piston (or piston coupling) 30 disposed about longitudinal axis CL, perpendicular to the cross section. Alternatively, actuator system 10 may utilize a square, rectangular, polygonal, or other configuration for housing 14, with coupling member 30 being adapted accordingly. In each of these designs, one or more wear members 36 can be disposed in sliding engagement between piston 30 and the inner surface of actuator housing 14; e.g., with one or more wear rings 36 disposed about piston 30, as shown in
A bushing 40 can be provided in front end 18 of actuator housing 14, disposed in sliding engagement with output rod 20 proximate distal end 22. For example, a ring-type bushing or bearing 40 can be disposed about output rod 20 in end cap 56, with rod axis A generally parallel to and offset from (e.g., above) longitudinal axis CL of actuator housing 14.
Drive pulley assembly 46 includes a drive pulley supported in rotation about axis RA on shaft bearings 44, within motor mount 16 at the back end of actuator housing 14 (proximal end 17). Idler pulley assembly 48 includes an idler pulley supported in rotation about axis RB on a needle bearing (or other bearing) 49, at the front end of actuator housing 14 (distal end 18). In this particular example, the drive and idler pulley rotational axes RA and RB are oriented generally parallel to one another, and generally perpendicular to the longitudinal dimension of actuator housing 14.
Motor 12 is rotationally coupled to drive pulley assembly 46, for example in a perpendicular mount configuration with the motor shaft rotational axis aligned along the drive pulley rotational axis (RA), as shown in
In additional to servo type electric motors 12, stepping motors, DC motors, AC motors and other motor drive systems can be utilized to rotate drive pulley assembly 46. Motor 12 can be also be mounted with the motor shaft and motor rotational axis in a transverse orientation as shown, or a generally parallel orientation with respect to longitudinal axis CL of actuator housing 14 (for example, using a gearbox or separate belt drive to couple motor 12 to drive pulley assembly 14).
Suitable materials for continuous drive belt 24 include metal reinforced polymers and rubberized plastics, with inwardly-projecting teeth configured to engage drive pulley assembly 46 and idler pulley assembly 48. Alternatively, continuous drive belt 24 can be provided in the form of a metal drive chain, or a substantially smooth or toothless drive belt.
Motor 12 is rotationally coupled to drive pulley assembly 46, and configured to selectively position drive member 30 along longitudinal axis CL by driving belt 24 in response to the rotation of pulley assembly 46. Drive member 30 is coupled to the upper or lower portion of belt 24, and disposed in reciprocal engagement with the interior surface of actuator housing 14.
For example, a piston-type drive member 30 may be disposed about belt drive 24 along longitudinal axis CL of actuator housing 14, as shown in
Generally, continuous belt 24 operates as a linear timing belt or timing chain, driven by motor 12 between drive pulley 26 and idler pulley 28. More specifically, drive belt 24 is configured to position piston coupling 30 along longitudinal axis CL of actuator housing 14, between drive pulley 26 in proximal end 17 of housing 14 and idler pulley 28 in distal end 18, respectively. Piston coupling 30 is attached to off-axis output rod 20, which moves back and forth along with piston coupling 30.
Electric motor-type, belt-driven linear actuator systems 10 can combine the functionality of screw-driven linear actuators and pneumatic rod type cylinders, utilizing a precision belt drive system. In particular, timing belt 24 can be driven at high speed to precisely position coupling 30 within actuator housing 14, extending tooling engagement 38 on distal end 22 of output rod 20 to one or more extended positions with respect to the front of housing 14, and then returning tooling engagement 38 to one or more retracted positions, in reciprocal fashion. Belt-driven actuator system 10 thus provides high-speed functionality of a pneumatic device, and also provides precision positional control characteristics of a screw-type linear actuator.
Actuator system 10 operates with a piston coupling or other drive member 30 disposed in reciprocal engagement within actuator housing 14, along longitudinal axis CL. The output rod 20 is coupled to drive member 30 at first (interior) end 21, within housing 14, and extends to second (exterior) end 22, outside housing 14 and opposite first end 21. Belt drive 24 is coupled to drive member 30 within housing 14, and configured to selectively position drive member 30 and first end 21 of output rod 20 along (or adjacent to) longitudinal axis CL. Thus, second end 22 of output rod 20 is selectively positioned outside housing 14 with respect to front end 18, in response to the reciprocal motion of drive member 30 along axis CL inside housing 14.
More specifically, actuator system 10 can be configured to position output rod 20 at speeds of at least 80 inches per second (that is, with a linear velocity of 200 cm/s or more). Lead screw and ball screw actuators are not easily configured for this form of motion, as the power screw typically reaches its critical (rotational) speed at a lower maximum linear velocity. That is, typical screw-driven actuators are not able to spin fast enough to achieve the desired linear velocity. Pneumatic actuators, on the other hand, require a compressed air source, and may not provide the same precision in positioning the output rod (e.g., at intermediate locations between the farthest extended and most retracted positions).
Depending upon application, the belt drive system may include a timing belt 24 coupled to drive member 30 between drive pulley 26 and idler 28, each disposed within actuator housing 14; e.g., along longitudinal axis CL as shown in
In contrast to typical pneumatic piston actuators, output rod 20 is disposed in an offset configuration within actuator housing 14, with rod axis A positioned parallel to and radially offset from centerline CL. In the particular configuration of
In off-axis actuator configurations, output rod 20 is offset within actuator housing 14, generally parallel to and spaced from drive belt 24 along longitudinal axis CL. Drive belt 24 may be provided in the form of a timing belt, with inwardly-projecting teeth 25 configured to engage a complementary sprocket structure on one or both of drive pulley 26 and idler pulley 28. A belt clamp 34 can be configured to attach piston 30 to timing belt 24, for example by engaging inwardly-projecting teeth 25 on top portion 24A, with output rod 20 disposed above belt 24 and in off-axis relationship with respect to centerline CL of actuator housing 14.
Piston coupling 30 is closely fitted to the inner surface of cylindrical tube or housing 14 using sliding wear rings 36, and is reciprocally driven through its travel length within actuator cylinder or housing 14 using timing belt (or transmission) 24. The output rod 20 is fastened off-axis with respect to centerline CL of housing 14 and piston coupling 30, with rod axis A located over drive belt 24 as described above.
This configuration provides space to attach timing belt 24 to piston coupling 30 via a belt clamp 34 or other mechanical attachment. For example, belt clamp 34 can be configured to engage one or more inwardly-protruding teeth or other features 25 on timing belt 24, which is centered about the main axis of motion of piston 30, along centerline CL of piston 30 and actuator housing 14.
In this particular design, actuator system 10 utilizes an “endless” timing belt 24. Other configurations may be constructed using a bulk belt material, for example with the ends joined together at belt clamp 34, or within piston coupling 30 (or at another location along top portion 24A or bottom portion 24B of timing belt 24). Similarly, belt 24 may be toothed or smooth, with belt clamp or coupling 34 configured accordingly. Belt 24 may also incorporate alternate timing features, e.g., optical or electromagnetic.
Front end cap or head 56 of actuator housing 14 also contains yoke tensioner assembly 50, disposed about idler pulley 28 along the piston axis or centerline CL of actuator housing 14. Yoke assembly 50 includes a front plate 58 and arms 60 on either side of drive belt 24, supporting idler pulley 28 in rotation about needle bearing 49. Yoke assembly 50 can also include a screw adjustment or other tensioning mechanism 62 to provide precision positioning of idler pulley 28 along centerline CL of actuator housing 14, and to provide the desired tension along timing belt 24.
Yoke (or yoke assembly) 50 has at least one arm 60 configured to rotationally support idler pulley (or idler) 28, and is selectively positionable along axis CL to tension drive belt 24 between drive pulley 26 and idler 28. For example, yoke 50 may include a front plate 58, which is selectively positionable along axis CL with respect to front end cap 56. In this particular configuration, two arms 60 extend from front plate 58 along longitudinal axis CL, in order to rotationally support idler pulley 56 on either side.
In these various examples, actuator system 10 includes an output rod 20 coupled at one (inner) end 21 to a belt-driven piston coupling 30, which is disposed within an actuator housing or cylinder 14. A drive belt 24 is configured to urge or drive piston coupling 30 in reciprocal motion along longitudinal axis or centerline CL of actuator housing 14, so that the other (outer) end 22 of output rod 20 is selectively positionable with respect to front end 18 of actuator housing 14, outside end cap 56 in the axial direction.
Alternatively, actuator system 10 comprises a piston 30 disposed within actuator housing 14. Drive belt 24 is configured to urge or drive piston 30 in reciprocal motion along longitudinal axis CL of housing 14. Output rod 20 has one end 21 coupled to piston 30 and another opposite end 22 selectively positionable outside the front end of housing 14, according to the reciprocal motion of piston 30 along centerline CL. Drive belt 24 can be coupled between a drive pulley 26 in back end 17 of housing 14 and an idler pulley 28 in front end 18; e.g., with idler pulley 28 positioned opposite drive pulley 26 along longitudinal axis CL.
The yoke (or yoke assembly) 50 can be configured with at least one arm 60 to rotationally support idler pulley 28 in a selected position along longitudinal axis CL of actuator housing 14, in order to provide a desired tension to drive belt 24 between drive pulley 26 and idler pulley 28. For example, yoke 50 may include a front plate 58 selectively positionable with respect to end cap 56 on front end 18 of actuator housing 14 via a screw or other adjustment mechanism 62. Two opposing arms 60 can extend from front plate 58 within actuator housing 14, supporting idler pulley 28 in rotation at the selected position along longitudinal axis CL.
A stepper motor, DC motor, servomotor or other motor 12 can also be used; e.g., coupled to actuator housing 14 via motor mount 16 at back end 17 of housing 14. In transverse mount configurations, as described herein, motor shaft 64 can be directly coupled to drive pulley 26, so that motor 12, drive pulley 26 and idler pulley 28 all have generally parallel rotational axes, each of which is disposed generally transverse or perpendicular to longitudinal axis CL of actuator housing 14.
For example, motor 12 can be rotationally coupled to drive pulley 26 along a motor axis RA, substantially transverse to longitudinal axis of housing 14. Bearings (e.g., ball bearings) 44 support drive pulley 26 in rotation about drive pulley axis RA, for example using a split bore and clamp or locking collar 65 to couple drive pulley shaft 68 and motor shaft 64. Drive pulley 26 and pulley shaft 68 can be rotationally locked using a transverse or radial pin 70, or similar mechanism.
The position of drive pulley 26 and timing belt 24 is precision controlled to extend and retract the output rod in a longitudinal direction with respect to actuator housing 14, as described above. For example, a high speed motor 12 may include a rotary encoder or controller 72 within the motor housing, as shown in
For example, a motor 12 can be provided to drive actuator system 10 by rotationally coupling motor 12 to drive pulley 26. A motor controller or encoder system 72 can then be provided to selectively position the far end 22 of output rod 20 outside front end 18 of actuator housing 14, based on the rotational position of motor 12.
Methods of operating linear actuator system 10 are also encompassed by the present disclosure, according to any of the examples and embodiments herein. For example, an electric motor 12 can be rotationally coupled to drive belt 24 via drive pulley 26, and controlled using an encoder or other motor controller 72 to selectively position distal end 22 of output rod 20 based on the rotational position of motor 12, drive pulley 26, and idler pulley 28.
An exemplary actuator system includes an actuator housing having a longitudinal axis, a piston member disposed within the actuator housing along the longitudinal axis, and a drive belt coupled to the piston member. The drive belt is configured to drive the piston member in reciprocal motion along the longitudinal axis, with an output rod having a first end coupled to the piston member and second end selectively positionable outside the actuator housing, in response to the reciprocal motion of the piston member within the actuator housing.
In these systems the drive belt can be coupled to a drive pulley in the back end of the actuator housing, with an idler pulley in the front end, disposed opposite the drive pulley along the longitudinal axis. A yoke can be provided with at least one arm configured to rotationally support the idler pulley, where the yoke is selectively positionable along the longitudinal axis of the actuator housing to tension the drive belt between the drive pulley and the idler pulley. For example, the yoke may have a front plate selectively positionable with respect to the front end of the actuator housing, and two arms extending along the longitudinal axis to rotationally support the idler pulley between them.
Additional features may include an electric motor rotationally coupled to the drive pulley and a motor controller configured for selective rotation of the motor, where the second end of the output rod is positioned outside the actuator housing based on the selective rotation. Suitable motors include a stepper motor, a DC motor, or an electric servomotor; e.g., transversely mounted to the actuator housing in the back end, where the electric motor, the drive pulley and the idler pulley each has a rotational axis disposed generally transverse to the longitudinal axis of the actuator housing.
The output rod can be disposed off-axis within the actuator housing, generally parallel to and spaced from the drive belt along the longitudinal axis. The drive belt can include a plurality of projecting teeth; e.g., configured for engagement with the drive pulley, with a clamp attachment configured to attach the piston member about the drive belt by engagement with one or more of the teeth.
The piston member can also be disposed about the drive belt, along the longitudinal axis of the actuator housing, and configured in reciprocal engagement with the inner housing surface. Where the actuator housing is a cylinder or has a cylinder or elliptical bore with a substantially circular or oval cross section, the piston member can be disposed about the longitudinal axis, with one or more wear members or rings disposed in sliding engagement between the piston member and the inner surface of the actuator housing. A bushing can also be disposed in sliding engagement about the distal end of the output rod, in the front end of the actuator housing.
The linear actuator apparatus may also have a drive member in reciprocal engagement within a housing, disposed along the longitudinal axis. The output rod has a first end coupled to the drive member within the housing, and a second end positionable exterior to the housing, opposite the first end. A belt drive is configured to selectively position the drive member within the housing, along the longitudinal axis, with the belt drive disposed within the housing and coupled to the drive member so that the second end of the output rod is selectively positioned outside (or exterior to) the housing.
Suitable belt drives include a timing belt coupled to the drive member; e.g., between a drive pulley and an idler disposed within the housing along the longitudinal axis. A motor can be rotationally coupled to the drive pulley, and configured to selectively position the drive member along the longitudinal axis by rotation thereof. Where the motor is rotationally coupled to the drive pulley along a motor axis, the axis can be substantially transverse (perpendicular or orthogonal) to, or substantial along (parallel to) the longitudinal axis of the housing.
Suitable drive members include a piston coupled to an upper or lower portion of the belt drive, and disposed in reciprocal engagement with an interior surface of the housing; e.g., where the piston member is disposed about the belt drive along the longitudinal axis of the housing. The output rod can be generally parallel to and offset from the belt drive (e.g., with respect to the longitudinal axis), with a bushing disposed about output rod, in sliding engagement proximate the second end.
Methods of operating such an actuator system or apparatus include supporting the output rod in sliding engagement within the actuator housing, where the output rod has a first end attached to the drive member and a second end selectively positionable exterior to the actuator housing, opposite the first end. Additional method steps include positioning the drive member in reciprocal motion within the actuator housing, along the longitudinal axis, and selectively controlling the reciprocal motion with a belt drive system; e.g., with a timing belt disposed between a drive pulley and an idler, along the longitudinal axis within the housing.
Where the drive member is coupled to the timing belt between the drive pulley and the idler, the second end of the output rod can be selectively positioned based on the rotational position of the drive pulley. Where the drive member comprises a piston disposed about the timing belt and coupled to its upper or lower portion, the method can include positioning the piston in reciprocal sliding engagement with the inner surface of the actuator housing. The method can also include supporting the output rod in sliding engagement at or proximate the second end, parallel to and offset from the longitudinal axis of the actuator housing.
Generally, the controller 200 generates electric signals or pulses that are received by the motor 12. The actuator subsystem 10 can also include or be operably connected to an encoder (e.g., a digital or analog encoder), which generates signals for the controller 200 to determine the position of the output rod 20. For example, signals from the encoder may correspond to the rotational position of the motor 12, and the rotational position of the motor 12 may determine the axial position of the output rod 20. Depending on embodiment, a screw drive or high-speed belt drive can be employed to position the output rod 20, as described herein.
For example, the part placement system 100 can include a linear actuator 10 with an electric motor configured for positioning a tool or probe member 110 on the end of the output rod 20, or a similar engagement mechanism 110 adapted for positioning parts. For example, a suitable probe 110 can be provided in the form of a tapered shaft with a tip 112 and shoulder or stop 114 attached to or incorporated onto the end of the output rod 20. Other tools and probes 110 can have a range of sizes, shapes and configurations, and the tip portion 112 can be configured to accept and secure parts with configurations that vary from one embodiment to the next.
In the illustrated example of
Depending on embodiment, the controller 200 directs the actuator system 10 to advance the output rod 20 at a suitable acceleration from the first part engagement position toward the second part placement position, where the part is released from the probe for engagement with the weld pin or other locating fixture. The acceleration may be greater than the corresponding component of the gravity vector, so that acceleration of the output rod 20 maintains the part secured to the probe 110.
In some embodiments, the probe 110 is integrally connected to or fixed onto the output rod 20. Alternatively, the probe 110 may be provides as a generally separate component, separable from the rod 20, for example using a threaded fastening or similar mechanical engagement.
IAs shown in
The actuator system 10 can have any number of suitable orientations relative to the gravity vector along the vertical axis V. For example, the actuator system 10 may be oriented at an angle θ relative to the vertical axis V, and angle θ may be acute, with output rod 20 and probe or fixture 110 oriented in a downward direction. Alternatively, angle θ may be obtuse, with output rod 20 and probe 110 oriented in an upward direction, or the angle θ may be approximately ninety degrees, with output rod 20 and probe 110 oriented in a generally horizontal direction, perpendicular to the vertical direction.
Gravity acts on the part with force component F1 in a longitudinal direction along the probe 110 (e.g., acting to move the part toward the end 112 of the probe 110, in the illustrated downward orientation). The gravitational force component F1=mp×g×cos θ, where mp is the mass of the part positioned on the end of the probe fixture 110, and g is the gravitational acceleration.
Friction acts on the part in a manner that tends to oppose sliding motion. For a stationary rod and part system, friction produces a force component F2 in a direction opposite the gravitational component F1, and with a maximum magnitude F2=μ×mp×sin θ, where μ is the coefficient of friction (or friction coefficient) between the part and the probe 110. If the gravitational component is high enough, a net force FL=F1−F2 can act longitudinally on the part, tending to move the part off the probe 110. More generally, under some operating conditions (e.g., depending on angle θ), the gravitational component F1 may be greater in magnitude than the frictional component F2, and in the absence of other forces a positive net force FL may tend to move the part toward the tip 112 of the probe 110, in the direction away from the output rod 20.
The output rod 20 can be driven at an acceleration selected to retain the part on the probe 110; e.g., at an acceleration ar suitable to overcome the tendency of the part to fall of the probe tip. For example, the acceleration ar may be greater than the magnitude of the net acceleration |FL/mp|. The acceleration ar may be associated with a constraint Fr, as defined in the (accelerating) frame of the output rod 20, which would appear to act on the part in a manner opposite the gravitational acceleration, in order to retain the part on the probe 110. Further, reducing the acceleration ar of the probe to a lower value ad can allow the part to move off the probe 110, for engagement with a locating fixture. Hence the acceleration of the probe 110 can be decreased over a transition region; e.g., from acceleration ar to a lower value ad (referred to as either acceleration or deceleration, depending on sign), at which the part moves longitudinally relative to the stop 114 and along the probe 110 to be released from the probe tip 112.
At acceleration ad, the part may have a suitable velocity to move off the probe 110 and onto the locating fixture. For example, the output rod 20 can be decelerated toward stop (zero velocity) at or near the part placement position, so that the probe 110 is substantially stationary for releasing the part onto a weld pin, before retracting the rod 20 back toward the first position to engage another part on the probe 110.
This contrasts with traditional pneumatic actuator designs, where the output rod is driven by compressed air and the probe accelerates continuously from the first (part engagement) position through to the second (part positioning) position, where the rod typically hits a hard stop defined by an elastic bumper or cushioning member. As described here, the acceleration of the output rod 20 can be modulated over the entire part placement stroke, including an extended transition region defined between the first (part engagement) position of the output rod, and the second (placement or release) position of the output rod. More generally, the controller 200 can be adapted for the linear actuator 10 to accelerate the output rod 20 from the first (part engagement) position to the transition region, and to reduce the acceleration of the output rod through the transition region to the second (placement) position, for releasing of the part from the probe tip 112 onto a weld pin or other locating fixture.
For example, the controller 200 may initially direct the actuator system 10 to move the output rod 20 together with the probe 110 at a first acceleration ar suitable to retain the part in motion from a first part engagement position toward a second part placement position, in order to sequentially engage, place and release a number of individual parts. When the probe 110 reaches the transition region defined between the first and second positions, the controller 200 can operate the actuator system 10 to reduce the acceleration of the output rod 20 and probe 110 to a lower (or negative) value ad, allowing the part to move off the tip 112 of the probe 110 and onto the weld pin or similar locating fixture. For example, in a transition region defined between the first (engagement) and second (placement) position of the output rod, the controller 200 can operate the actuator system 10 to decelerate the output rod 20 and probe 110 toward a stop in the placement position, for placement of the part in a desired location with respect to a workpiece; e.g., releasing the part onto a weld pin or placing the part with respect to a locating fixture.
Generally, the controller 200 can be configured to determine and modify the part engagement position, and the part placement and releasing positions. Depending on embodiment, the controller 200 can be configured to determine the part placement position based on the location of the output rod 20 when the probe 110 contacts the locating fixture. When the probe 110 contacts the locating fixture, the current demand to the motor 12 of the actuator system 10 may increase, while the position of the probe 110 remains substantially unchanged, or the motor current may change disproportionately relative to the change in position, as compared to free movement of the output rod 20 before the probe 110 contacts the locating fixture. The controller 200 can be adapted to correlate the change in motor current with the observed generally static or unchanged position of the output rod 20, when there is contact between the probe 110 and the weld pin or similar locating feature.
This calibration (or recalibration) process can be iterated for improved accuracy, and can proceed independently of the part placement cycle, without engaging a part on either the probe or the locating fixture. The speed of the output rod can also be substantially reduced during calibration to avoid damage to the placement fixture, so that the contact cycle may take a substantial fraction of a second or a few seconds or more, as compared to part placement cycles that may take place over a few tenths of a second or less.
Generally, controller 200 provides for precision calibration of the actuator 10, in order to position the output rod 20 with the tip of the probe 110 more precisely located with respect to the weld pin or other machine fixture than in other designs, such as designs using a pneumatic actuator. Further, the controller 200 can be configured to automatically determine the part placement position based on a test contact between the probe 110 and the weld pin, and to adjust the position of the probe 110 adjacent the weld pin for placing a nut or similar part, without direct contact between the weld pin and probe 110. This contrasts with other designs, where the probe 110 contacts the weld pin during every placement cycle, or where the end position of the probe 110 is determined by input from an operator, in a time consuming manual calibration process. The controller 200 can also determine a suitable transition region for the output rod 20, over which the controller 200 directs the actuator system 10 to reduce the acceleration of the output rod 20 so that the tip of the probe 110 comes to a stop with the output rod in the selected part placement position, adjacent the weld pin or other locating fixture.
Specifically, the controller 200 can direct the actuator system 10 to decelerate the output rod 20 as the probe 110 moves to the placement position at or adjacent the weld pin, where the part moves from the probe 110 to the locating fixture. When the probe 110 stops in the part placement position, the gap between the tip of the probe 110 and the tip 325 of the weld pin or other locating fixture 320 can be selected to ensure engagement of the part 80 with the pin 320, for example about 15 mil to about 30 mil (0.38 mm to 0.76 mm), or about 1 mm (about 40 mil) or less.
More generally, the gap between the tip 112 of the probe or similar part placement tool 110 and the top 325 of the weld pin or fixture 320 can be selected to ensure proper part placement, with less risk of the part dropping off the end of the probe 110 and not properly engaging the locating fixture or feature 320. The selected gap may also be larger or smaller, depending on the dimensions of the part 80, for example less than about 10 mil (0.25 mm) or up to about 40-50 mil (about 1.0 mm to 1.2 mm), or up to about 1 mm to 2 mm (40 mil to 80 mil), or up to about a tenth of an inch (2.5 mm), or more.
Suitable materials for probe 110 include hardened steel and other metals and metal alloys with properties selected for durability and service life in welding and machine tool applications. Suitable materials for weld pins 320 include copper, brass, and other high-conductivity metals and metal alloys. More generally, and depending on machining application, the locating fixture 320 can also be made of hardened steel and other metal alloys, or from composite materials.
Generally, the part 80 can be slidably engaged on the probe 110; e.g., near the tip 112 of the probe 110. As the probe 110 is advanced by the actuator system 10 to the first position, the probe 110 engages the part 80. For example, the probe 110 may be formed as tapered shaft, with a pointed tip 112 and a shoulder or stop 114 adjacent the output rod 20, so that the part 80 rests against the tapered shoulder or stop 114 when fully engaged. The probe 110 can then be moved to the part placement position, at a suitable acceleration to retain the part 80 on the probe 110, and the controller 200 can be configured to direct the actuator system 10 to advance the output rod 20 and probe 110 along longitudinal rod axis A, toward a weld pin or similar part placement structure 320.
The size, shape and structure of the locating feature 320 will also vary from one embodiment to the next, based on the configuration of the corresponding machine fixture 300. In the illustrated embodiment, a welding fixture 300 is provided with a metal lower table 310 and weld pin 320. The tip 325 of the pin 320 is sized and configured to accept the part; e.g., the pin 320 may include a generally tapered tip portion 325 that is sized configured to receive a weld nut or similar part 80.
The part 80 may be welded to another component such as to a steel plate or other sheet metal workpiece 90, as shown in
In
As the part 80 is positioned (e.g., with the controller 200 directing the actuator system 10 to extend the output rod 20 with the part 80 engaged on the probe 110), the actuator system 10 can reduce the acceleration of the output rod 20, thereby releasing the part 80 from the probe 110. Specifically, the controller 200 can operate the actuator system 10 to decelerate the output rod 20 toward a stop, so that the part 80 moves off the probe 110 in a direction along the rod axis A, and onto a weld pin or similar part receiving fixture 320 oriented along a different axis B.
It should be appreciated that the part locating fixture 320 can be sized, configured and positioned to receive a variety of parts 80 by advancement of the output rod and probe to the part placement position adjacent the fixture 320, releasing the part for engagement therewith. For example, the weld pin 320 of a welding table 310 can be oriented and positioned to engage the part 80 onto the tip 325 of the weld pin 320 as the output rod is advanced to the placement position, releasing the part 80 from the probe and onto the pin 320 without direct contact between the probe tip and pin 320.
As shown in
In particular embodiments, the controller can be configured to determine the position of the output rod 20 at the point of contact between the probe 110 and the tip 325 of the weld pin 320. For example, the controller can be programmed to monitor the motor current as the probe 110 approaches the weld pin 320, and to determine the probe stop position in response to an increase in the motor current required to drive the output rod 20 when the probe tip 112 contacts the weld pin or other locating fixture 320.
Over the course of repeated part placement cycles, the tip 325 of the weld pin 320 will erode due to contact with the weld nut or other part 80, so that the gap between the weld pin 320 and probe tip 112 tends to increase over time. In welding applications, where the pin member 320 is commonly formed of copper, brass or other conductive materials that may be relatively soft as compared to the material of the weld nut or other part 80, the gap between the tip 112 of the probe 110 and the tip 325 of the pin 320 may increase to the point where the part 80 does not properly and consistently engage with the pin 325. To address this problem, the controller can be configured to periodically determine or recalibrate of the probe position, in order to adjust the part placement position to maintain the desired spacing between the end 112 of the probe 110 and the tip 325 of the pin 320, when placing the part 80. This reduces the risk of dropping or misplacing the part 80, even if the geometry of the weld pin or fixture 320 changes over time.
The part placement system can also include alternative mechanisms for detecting contact between the probe 110 and weld pin 320. For example, where the weld pin 320 and probe 110 are formed of conductive materials such as steel, copper, brass, etc., an ohmmeter can be operably coupled with the controller, in order to detect contact between probe end 112 and the tip 325 of the weld pin 320 based on a change in resistance across the probe 110 and the weld pin 320 on the lower table 310 of the machine fixture 300. Analogously, a voltmeter or ammeter cam be operably coupled between the weld pin 320 and the probe 110, so the controller can detect a change in voltage or current when the probe end 112 contacts the tip 325 of the weld pin 320. Alternatively, the controller can be operably coupled to an optical sensor system configured to detect the top edge or end 325 of the locating fixture 320 along longitudinal axis B, relative to the tip 112 of the probe 110, in order to determine the point of contact between probe 110 and pin 320, and the desired spacing between the probe tip 112 and the tip 325 of the pin 320.
In some embodiments, the controller can operate the actuator to advance the output rod 20 to contact the probe 110 against the weld pin 320 without dispensing a part 80 (e.g., during a calibration cycle of the part placement system 100). Additionally or alternatively, the controller can operate the actuator to advance the output rod 20 and position the probe 110 adjacent the weld pin 320, so that the part 80 is dispensed from the probe tip 112 onto the top end 325 of the weld pin 320 without the probe 110 contacting the weld pin 320. In some embodiments, the controller can be configured to operate the actuator to further advance the probe 110 to contact the weld pin 320 and determine the position of the output rod 20 when the probe tip 112 contacts the tip 325 of the weld pin 320.
Generally, the controller directs the actuator to advance the output rod 20 so the probe 110 contacts the weld pin 320 a suitable number of times during calibration of the part dispensing system. For example, the controller may periodically or intermittently calibrate the probe tip/pin spacing at preset or selected intervals, by operating the actuator to advance the output rod 20 to contact the tip 112 of the probe 110 with the tip 325 of the weld pin 320. As described herein, the controller can then adjust or change to the location of the part placement position, based on the determined probe stop position where the probe 110 contacts the weld pin 320, in order to position the output rod 20 so that the probe tip 112 maintains the desired spacing from the weld pin tip 325 when placing the part 80 on the pin member 320.
Generally, the controller can recalibrate the part placement and release positions by directing the actuator to advance the output rod 20 to contact the probe 110 with the weld pin 320, and adjusting the position at suitable intervals. For example, the controller may recalibrate the part placement and release positions after a selected number of part placement cycles (e.g., after every 10, 100, 1000 or 10,000 part placement cycles, or another suitable number of cycles). Additionally or alternatively, the controller can recalibrate the part placement and release positions after a selected operational time period (e.g., every 60 or 100 minutes, or on an hourly, daily or weekly schedule, or at another suitable interval).
The controller adjusts the location of the part placement position to that the probe 110 maintains a selected distance from the weld pin 320. Under some operating conditions, one or more portions of the weld pin 320 may wear during operation (e.g., at the tip 325), changing the geometry of the pin member 320, or the pin 320 may be replaced. The controller can update the location of the output rod 20 in order to accommodate wear or replacement of the pin 320, to maintain the selected spacing of the probe 110 from the point of actual physical contact between the probe tip 112 and the tip 325 of the weld pin 320. Thus, the spacing remains approximately or substantially the same during operation, even if the tip 325 of the weld pin 320 wears substantially, for example by adapting the controller to advance the probe 110 longitudinally along actuator rod axis A, closer to the weld pin tip 325 along the longitudinal axis B.
Similarly, as both the tip 325 of the weld pin 320 and the tip 112 of the probe 110 may experience wear from contact with the part 80, the controller can update the location of the part placement position along the rod axis A, relative to the longitudinal axis B of the weld pin 320. The controller can be adapted to change the part placement position of the output rod 20 as one or both of the pin 320 and probe 110 wears, so the selected distance is maintained between the probe tip 112 and the end 325 of the weld pin 320. Depending on embodiment, the controller can determine the part placement position so the tip 112 of the probe 110 maintains a suitable spacing from the tip 325 of the weld pin 320; e.g., where the tip 112 of the probe 110 is spaced from the nearest location on the top surface 325 of the weld pin 320 at a distance between about 0.005 inch (5 mil) and about 0.050 inch (50 mil), or about 0.125 mm to about 1.25 mm. Further, continuously or intermittently adjusting the part placement position of the output rod 20 can facilitate repeatable placement of the part 80 with respect to the weld pin tip 325, and consistent engagement of the part 80 onto the weld pin 320 adjacent the workpiece 90, thereby avoiding or minimizing dropping or misplacement of the part 80 relative to the workpiece 90 and weld table 310, or other machine fixture 300.
As shown in
In welding applications, the electrode 400 can be operably coupled to a power source configured to pass electrical current from the electrode 400 to the weld table 310 via the part 80; e.g., for resistance welding of the part 80 to the workpiece 90. The welding table 310 can also be disposed in electrical contact with the workpiece 90 and part 80, so that the current passes through the projections on the part 80 and into the workpiece 90, to provide suitable resistive heating for forming a weld connection. In some of embodiments, the electrode 400 is moveable to engage the part 80 about the weld pin 320, and to compress the part 80 and workpiece 90 together between the lower table 310 and electrode 400. Alternatively, a mechanical attachment such as riveting can be employed to fix part 80 to workpiece 90, or another machine process can be used.
As shown in
In some embodiments, the part loader 500 includes a trap-door access 520 adapted to retain the parts 80 in the magazine 510, until selected for placement. For example, the access door 520 can be biased (e.g., spring-loaded) toward the closed position, as shown in
The controller also operates the actuator to retract the output rod 20 toward the first position, for the probe 110 to engage and secure additional parts 80. For example, the controller may control the motor current supplied to the actuator motor to rotate the motor in a direction opposite the direction of rotation for advancing the output rod 20 toward the locating fixture (e.g., in either a clockwise or counterclockwise direction). As the probe 110 is retrieved into the part loader 500, the access door 520 can close to prevent any of the parts 80 from falling out of the magazine 510.
The engagement position of the output rod 20 can also be recalibrated and adjusted; e.g., based on the change in the motor current as the probe tip 112 contacts the access door 520, and as the probe 110 engages the part 80. This provides for further modulation of the acceleration of the output rod 20 during the part placement cycle, for example to limit the speed of the output rod 20 during engagement with the part 80 in the magazine 510, and then increasing the acceleration as the output rod 20 advances from the part loader 500 toward the machine fixture.
These operations can also be performed in a loop or continuous cycle, in order position a plurality of parts 80 relative to one or more workpieces, and to weld or mechanically fasten the parts thereto. In contrast to traditional pneumatic actuator designs, the modulated acceleration can be coded into the control cycle software or firmware, so that operations are more resistant to change based on environmental conditions (e.g., due to changes in temperature or pneumatic pressure), or due to unauthorized attempts to modify the system cycle.
Method 600 can also include one or more steps of calibrating the part engagement position, and the part placement and release positions (step 650). Calibration can be performed, e.g., by slowly extending the output rod until the tip of the probe engages the part within a magazine, or until the probe contacts the locating fixture, and then determining the engagement or placement position based on the probe location. The engagement and placement positions can also be adjusted to accommodate the part size and to maintain a selected spacing, as described above.
In some embodiments, calibration (step 650) is performed periodically, in order to accommodate wear on the locating fixture or probe, so that part engagement and placement accuracy can be maintained over an extended service lifetime. For example, calibration (step 650) may be performed on a periodic schedule; e.g., every two hours, every four hours, every six or eight hours, every twelve hours, or on a daily, two-day, three-day, or weekly or monthly schedule, or at a selected period therebetween. Alternatively, calibration (step 650) can be performed after a number of part placement cycles, for example 10 cycles, 100 cycles, 1,000 cycles, 5,000 cycles, 10,000 cycles, or more, or at a suitable number of cycles therebetween.
Suitable methods 600 for placing parts can thus include one or more steps of: positioning a part placement tool with respect to a part (step 610), e.g., with the placement tool or probe disposed on the output rod of a linear actuator; engaging the part with the probe (step 620), e.g., with the output rod in a first (part engagement) position; and placing the part with respect to a locating fixture (step 630), e.g., with the output rod in a second (part placement) position. Depending on application, method 600 may also include releasing the part for engaging with the locating fixture (step 640), and attaching the part (step 645), e.g., by resistance welding or another machine process.
The end placement or part release position can be determined by a controller operably coupled with the linear actuator; e.g., with the controller adapted for the linear actuator to drive the output rod between the first and second positions for engagement and placement of the part with respect to a locating fixture. The part placement tool or probe can be spaced from the locating fixture with the output rod in the second position, or the probe can approximately abut the locating fixture; e.g., at the tip of the weld pin. The controller can be configured to determine the end position of the output rod responsive to the calibration process (step 650); e.g., by carefully contacting the locating fixture with the probe, and sensing the change in the motor current when the contact occurs.
Determining the second position can comprise the controller operating the linear actuator to contact the placement fixture with a tip of the locating fixture, absent the part. Thus, the second position calibration can be an independent operational step, performed iteratively and periodically, separate from placing the part. The controller can determine a change in the motor current provided to the linear actuator, with the placement fixture contacting the tip of the locating fixture, where the second position is determined responsive to the change in the motor current. A similar process can be used to calibrate the engagement position; e.g., by sensing a change in the motor current when the probe engages the part in a part loader or magazine.
The controller can also change the first and second positions of the output rod responsive to the change in the motor current; e.g., where the change in the motor current is responsive to a change in geometry of the tip of the locating fixture or the probe. For example, after repeated part placement cycles, the tip of the weld pin or other placement fixture may be worn by contact with the inner threaded section of a welding nut type part, changing the length, width, or other geometry of the locating fixture. Changes in geometry can also be accommodated when replacing the weld pin, by an additional automated calibration process.
Similar effects can also occur on the placement fixture. The first “engagement” position and the second “release” position of the output rod can thus be recalibrated in response to changes in geometry of either the locating fixture or the probe, so that the part is accurately and consistently engaged and placed over many operational cycles, without dropping or misplacing parts due to an unexpected or undetermined gap between the placement fixture and the locating fixture.
In some examples, the part placement method is performed iteratively to place a number of parts with respect to the locating fixture, for example over many hours, days, weeks, or months of operation. In these embodiments, the method may include the controller changing the second position responsive to operating the linear actuator to iteratively contact the placement fixture with the locating fixture, absent the part. Thus the calibration or recalibration can take place independently of the part placement function, at predetermined time intervals, after a predetermined number of part placement cycles, or as needed based on user input (e.g., when either the probe or the locating fixture is replaced).
Where the output rod has a first end coupled to a piston member and a second end coupled to the placement fixture, opposite the first end, the method can further comprise driving the piston member in reciprocal motion along a longitudinal axis of the linear actuator to move the output rod between the first and second positions, for engagement and placement of the part with respect to the locating fixture. For example, a belt drive can be coupled to an electric motor, and adapted to reciprocate the piston member along the longitudinal axis of the linear actuator, with the output rod coupled to the piston member.
Suitable methods can also include accelerating the output rod from the first position to a transition region defined between the first position and the second position, and reducing the acceleration of the output rod from the transition region to the second position for releasing the part onto the locating fixture. The weld pin or other locating fixture can comprise a projection, tab, datum, indent, hole, channel, or other structural feature, for example a weld pin or other placement fixture for a welding electrode. In these embodiments, the method can include disposing the part on the positioning pin, and welding the part to a workpiece adjacent thereto.
A suitable part placement system can comprise one or more of: a linear actuator operably coupled to an output rod; e.g., with the linear actuator adapted to drive the output rod between a first position and a second position; a part placement tool or probe on an end of the output rod; e.g., with the probe adapted to engage the part at the first position of the output rod and to place the part with respect to a locating fixture at the second position of the output rod; and a controller operably coupled with the linear actuator; e.g., with the controller adapted for the linear actuator to drive the output rod between the first and second positions for engagement of the part with the locating fixture. The controller can also be configured to determine the second position of the output rod responsive to contacting the locating fixture with the probe.
In some examples, the linear actuator comprises an actuator housing having a longitudinal axis; a piston member disposed within the actuator housing along the longitudinal axis; and a drive belt coupled to the piston member, with the drive belt configured to drive the piston member in reciprocal motion along the longitudinal axis. For example, the output rod may have a first end coupled to the piston member and second end opposite the first end; e.g., with the second end coupled to the probe for selective positioning outside the actuator housing, in response to the reciprocal motion of the piston member within the actuator housing. A rotatable shaft can be operably connected to an electric motor and the drive belt, e.g. where rotation of the shaft in a first direction drives the rod from the first position toward the second position and rotation of the shaft in a second direction opposite the first direction drives the rod from part second position toward the first position.
Depending on application, the controller can be configured to determine the second position by directing the linear actuator to move the output rod to contact the weld pin or other locating fixture with a tip of the probe, and then to where the tip of the probe is selectively spaced from the locating fixture with the output rod in the second position, for release of the part onto the locating fixture. The controller can be configured to determine a contact position of the output rod based on a change in a motor current provided to the linear actuator with the probe contacting the locating fixture, and the controller can be further configured to change the second position responsive to a change in the contact position of the output rod; e.g., with the change in contact position responsive to a change in geometry of the locating fixture.
The controller can also be configured to determine the change in contact position by iterative contact of the probe with the locating fixture, absent the part. In these examples the second (part placement or release) position of the output rod can be recalibrated to account for wear or other changes in the geometry of the locating fixture or placement fixture (or both), independently of the part placement cycle. The contact can be repeated with the output rod moving substantially more slowly than during a part placement cycle; e.g., over a period of a few seconds or more, in order to determine an average or best-fit part placement position for the output rod, with the probe adjacent to but not necessarily contacting the weld pin (or other positioning feature).
In some embodiments, the controller is configured for the linear actuator to accelerate the output rod from the first position to a transition region defined between the first position and the second position, and to reduce the acceleration of the output rod from the transition region to the second position for releasing the part onto the locating fixture. For example, the probe may comprise a tapered portion adapted to engage the part by entering an opening therein, with the output rod in the first position, and the locating fixture may comprise a locating post or pin member having a tip section adapted to engage the same opening in the part, when the part is released from the placement fixture with the output rod in the second position. A magazine can be configured to provide a plurality of such parts for sequential engagement with the placement fixture and the locating fixture, respectively, in response to reciprocal motion of the output rod between the first and second positions.
A suitable part placement apparatus can comprise one or more of: a linear actuator operably coupled to an output rod at a first end thereof; e.g., with the linear actuator comprising a piston member disposed within an actuator housing and a drive belt coupled to the piston member, the drive belt configured to drive the piston member in reciprocal motion along a longitudinal axis of the actuator housing; and a part placement tool or probe member on a second end of the output rod, opposite the piston member coupled to the first end; e.g., with the probe adapted to engage a part at the first position of the output rod and to place the part with respect to a locating fixture at the second position of the output rod.
A controller can be operably coupled with the linear actuator; e.g., with the controller adapted for the linear actuator to drive the output rod between the first and second positions for engagement of the part with the locating fixture. The controller can also be configured to determine the second position of the output rod responsive to contacting the locating fixture with the probe, absent the part and independent of the part placement cycle.
The locating fixture may comprise a weld pin for a welding electrode. The apparatus can further comprise a magazine configured to provide a plurality of parts for sequential engagement with the part placement tool and the weld pin, respectively, in response to reciprocal motion of the output rod between the first and second positions.
In any of these examples, the actuator can include an actuator housing having a longitudinal axis; a piston member disposed within the actuator housing along the longitudinal axis; a drive belt coupled to the piston member, the drive belt configured to drive the piston member in reciprocal motion along the longitudinal axis; and an output rod having a first end coupled to the piston member and second end opposite the first end. The second end of the output rod can be selectively positionable outside the actuator housing; e.g., in response to the reciprocal motion of the piston member within the actuator housing.
The drive belt can be coupled to a drive pulley in a back end of the actuator housing and an idler pulley in a front end of the actuator housing, the idler pulley disposed opposite the drive pulley along the longitudinal axis. A yoke can be configured with at least one arm to rotationally support the idler pulley, where the yoke is selectively positionable along the longitudinal axis of the actuator housing to tension the drive belt between the drive pulley and the idler pulley. For example, the yoke can comprise a front plate selectively positionable with respect to the front end of the actuator housing and two arms extending along the longitudinal axis to rotationally support the idler pulley therebetween.
An electric motor can be rotationally coupled to the drive pulley; e.g., with a motor controller configured for selective rotation of the electric motor; and where the second end of the output rod is positioned outside the actuator housing in response to the selective rotation. In various embodiments, the electric motor comprises a stepper motor, a DC motor or an electric servomotor transversely mounted to the actuator housing in the back end thereof; e.g., where the electric motor, the drive pulley and the idler pulley each has a rotational axis disposed generally transverse to the longitudinal axis of the actuator housing.
The output rod can be disposed off-axis within the actuator housing, generally parallel to and spaced from the drive belt along the longitudinal axis. The drive belt can comprise a plurality of projecting teeth configured for engagement with the drive pulley, with a clamp attachment configured to attach the piston member about the drive belt by engagement with one or more of the teeth. The piston member can be disposed about the drive belt along the longitudinal axis of the actuator housing, and configured in reciprocal engagement with an inner surface thereof.
Depending on application, the actuator housing can comprise a cylinder or cylinder bore having a substantially circular cross section, with the piston member disposed about the longitudinal axis thereof. One or more wear members or rings can be disposed in sliding engagement between the piston member and an inner surface of the actuator housing; e.g., with a bushing disposed in sliding engagement about the distal end of the output rod in the front end of the actuator housing.
Other suitable linear actuator systems can be provided, comprising: a housing having a longitudinal axis; a drive member in reciprocal engagement within the housing and disposed along the longitudinal axis thereof; an output rod having a first end coupled to the drive member within the housing and a second end positionable exterior to the housing, opposite the first end; and a belt drive configured to selectively position the drive member within the housing along the longitudinal axis; e.g., where the belt drive is disposed within the housing and coupled to the drive member so that the second end of the output rod is selectively positioned exterior to the housing. For example, the belt drive can comprise a timing belt coupled to the drive member between a drive pulley and an idler disposed within the housing along the longitudinal axis, with a motor rotationally coupled to the drive pulley and configured to selectively position the drive member along the longitudinal axis by rotation thereof, and where the motor is rotationally coupled to the drive pulley along a motor axis substantially transverse to the longitudinal axis of the housing.
The drive member can comprise a piston member coupled to an upper or lower portion of the belt drive and disposed in reciprocal engagement with an interior surface of the housing, e.g. where the piston member is disposed about the belt drive along the longitudinal axis of the housing. The output rod can be generally parallel to and offset from the belt drive with respect to the longitudinal axis of the housing, with a bushing disposed about the output rod in sliding engagement proximate the second end.
Suitable methods of operating a linear actuator include one or more steps of: supporting an output rod in sliding engagement within an actuator housing, where the output rod comprises a first end attached to a drive member and a second end selectively positionable exterior to the actuator housing, opposite the first end; positioning the drive member in reciprocal motion within the actuator housing, along a longitudinal axis thereof; and selectively controlling the reciprocal motion of the drive member with a belt drive system comprising a timing belt disposed between a drive pulley and an idler along the longitudinal axis within the housing.
The drive member can be coupled to the timing belt between the drive pulley and the idler so that the second end of the output rod is selectively positioned based on a rotational position of the drive pulley. For example, the drive member can comprise a piston disposed about the timing belt and coupled to an upper or lower portion thereof, in combination with one or both of: positioning the piston in reciprocal sliding engagement with an inner surface of the actuator housing; and supporting the output rod in sliding engagement proximate the second end, parallel to and offset from the longitudinal axis of the actuator housing.
Depending on application, the method can include selectively positioning the second end of the output rod outside the actuator housing based on a rotational position of an electric motor rotationally coupled to the drive pulley along a motor axis substantially transverse to the longitudinal axis of the housing. The timing belt itself can comprise a plurality of inwardly or outwardly-projecting teeth configured for engagement with complementary features on a belt clamp mechanically fastened to or within a body of a coupling member for attaching a top or upper portion of the drive belt to an inner surface of the piston.
A sliding engagement can be provided between the piston and the inner surface of the actuator housing; e.g., with a wear ring or sliding engagement member disposed between an outer radius or outer surface of the drive member and the inner surface of the actuator housing. Suitable materials for the wear ring or sliding engagement member include a durable polymer, metal, or composite material.
The output rod can be coupled to the drive belt via the piston member by seating the first end into an axial cavity in the piston member using a mechanical coupling. The output rod can be disposed above the drive belt; e.g., with a longitudinal axis of the output rod between an inner surface of the actuator housing and a top portion of the drive belt, opposite a bottom portion of the drive belt. The output rod can be coupled to the belt drive via the piston member disposed above the belt drive; e.g., with a longitudinal axis of the output rod between an inner surface of the actuator housing and the upper portion of the belt drive, opposite the lower portion of the belt drive.
While this invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes can be made and equivalents may be substituted without departing from the spirit and scope thereof. Modifications may also be made to adapt the teachings of the invention to particular problems, technologies, materials, applications and materials, without departing from the essential scope thereof. Thus, the invention is not limited to the particular examples that are disclosed herein, but encompasses all embodiments falling within the scope of the appended claims.
This application claims priority to U.S. Provisional Application No. 62/549,183, HIGH SPEED LINEAR ACTUATOR PART PLACEMENT SYSTEM, filed Aug. 23, 2017, which is incorporated by reference herein, in the entirety and for all purposes.
| Number | Date | Country | |
|---|---|---|---|
| 62549183 | Aug 2017 | US |
