Strapping device with a wolfrom planetary gear set

Abstract

Various embodiments of the present disclosure provide a strapping device for forming a tensioned strap loop around a load. The strapping device includes a rotatable tension wheel, a driven shaft operably connected to the tension wheel to rotate the tension wheel, a motor operably connected to the driven shaft to rotate the driven shaft, and a Wolfrom planetary gear set. The Wolfrom planetary gear set is configured to convert an input rotational speed of the driven shaft to an output rotational speed of the tension wheel. The output rotational speed is less than the input rotational speed.

Description

STRAPPING DEVICE WITH A WOLFROM PLANETARY GEAR SETPriority

[0001] This application claims priority to and the benefit of U.S. Provisional Patent Application No. 63 / 519,394, filed August 14, 2023, the entire contents of which is incorporated herein by reference.Field

[0002] The present disclosure relates to strapping devices, and more particularly to strapping devices configured to tension strap around a load and to attach overlapping portions of the strap to one another to form a tensioned strap loop around the load.Background

[0003] Strapping devices are configured to tension strap around a load and to attach overlapping portions of the strap to one another to form a tensioned strap loop around the load. Battery-powered strapping devices are one type of strapping device. To use one of these strapping devices to form a tensioned strap loop around a load, an operator pulls strap leading end first from a strap supply, wraps the strap around the load, and positions the leading end of the strap below another portion of the strap. The operator then introduces one or more (depending on the type of strapping device) of these overlapped strap portions into the strapping device and actuates one or more buttons to initiate a tensioning cycle during which a tensioning assembly tensions the strap around the load and, after completion of the tensioning cycle, a sealing cycle during which a sealing assembly attaches the overlapped strap portions to one another, thereby forming a tensioned strap loop around the load.

[0004] Since strapping device operators can use handheld strapping devices hundreds of times each day, there is a continuing need to make the strapping devices as lightweight as possible (without sacrificing performance) to reduce operator fatigue.Summary

[0005] Various embodiments of the present disclosure provide a strapping device for forming a tensioned strap loop around a load. The strapping device includes a rotatable tension wheel, a driven shaft operably connected to the tension wheel to rotate the tension wheel, a motor operably connected to the driven shaft to rotate the driven shaft, and a Wolfrom planetary gear set. The Wolfrom planetary gear set is configured to convert an input rotational speed of the driven shaft to an output rotational speed of the tension wheel. The output rotational speed is less than the input rotational speed.Brief Description of the Figures

[0006] Figure l is a perspective view of one example embodiment of a strapping device of the present disclosure.

[0007] Figure 2 is a block diagram of certain components of the strapping device of Figure 1.

[0008] Figures 3A-3C are diagrammatic views of the strapping device of Figure 1 securing a load to a pallet.

[0009] Figure 3D is a perspective view of a friction- weld strap joint formed by the strapping device of Figure 1.

[0010] Figure 4 is a perspective view of the working assembly of the strapping device of Figure 1.

[0011] Figures 5 A and 5B are perspective assembled and exploded views, respectively, of the tensioning assembly of the working assembly of Figure 4.

[0012] Figure 6 is a cross-sectional perspective view of the tensioning assembly of Figures 5 A and 5B taken along line 6-6 of Figure 5 A.

[0013] Figure 7 is a perspective view of the tensioning assembly of Figures 5A and 5B and the motor and part of the transmission assembly of the working assembly of Figure 4.Detailed Description

[0014] While the systems, devices, and methods described herein may be embodied in various forms, the drawings show and the specification describes certain exemplary and nonlimiting embodiments. Not all of the components shown in the drawings and described in the specification may be required, and certain implementations may include additional, different, or fewer components. Variations in the arrangement and type of the components; the shapes, sizes, and materials of the components; and the manners of connections of the components may be made without departing from the spirit or scope of the claims. Unless otherwise indicated, any directions referred to in the specification reflect the orientations of the components shown in the corresponding drawings and do not limit the scope of the present disclosure. Further, terms that refer to mounting methods, such as mounted, connected, etc., are not intended to be limited to direct mounting methods but should be interpreted broadly to include indirect and operably mounted, connected, and like mounting methods. This specification is intended to be taken as a whole and interpreted in accordance with the principles of the present disclosure and as understood by one of ordinary skill in the art.

[0015] Figures 1-7 show one example embodiment of a strapping device of the present disclosure in the form of a battery-powered portable strapping device 50 and certain assemblies and components thereof. As shown in Figures 3A-3C, the strapping device 50 is configured to carry out a strapping cycle to tension and seal strap S (plastic strap in this example embodiment) around a load L on a pallet P to form a tensioned strap loop that secures the load L to the pallet P. An operator pulls strap S from a strap supply (not shown) and wraps the strap around the load L and through the openings in the pallet P until a lower portion LP of the strap S (which includes the leading end of the strap S) is positioned below an upper portion UP of the strap S, as shown in Figure 3A. The operator then introduces the overlapped upper and lower portions UP and LP of the strap S into the strapping device 50 and actuates one or more buttons to initiate the strapping cycle. As shown in Figure 3B, a motor drives a tensioning assembly to carry out a tensioning cycle during which the strapping device 50 tensions strap S around the load L. Once a preset tension is reached in the strap S, as shown in Figure 3C, the motor drives a sealing assembly to carry out a sealing cycle during which the strapping device 50 connects theupper and lower portions UP and LP of the strap S to one another via friction welding to form a strap joint SJ, as shown in Figure 3D, and cuts the strap S from the strap supply.

[0016] The strapping device 50 includes a housing 100, a working assembly 200, first and second pushbutton actuators 1410 and 1, a display assembly 1490, a power supply, a controller 1600, and one or more sensors 1700.

[0017] The housing 100, which is shown in Figure 1, is formed from multiple components that collectively at least partially enclose and / or support some (or all) of the other assemblies and components of the strapping device 50. In this example embodiment, the housing 100 includes a front housing section 110, a rear housing section 120, a motor housing section 130, and a handle section 150. The front housing section 110 at least partially encloses and / or supports at least some of the components of the working assembly 200. The rear housing section 120 at least partially encloses and / or supports at least some of the components of the display assembly 1490 and defines a receptacle sized, shaped, and otherwise configured to receive and at least partially enclose and / or support the power supply (not shown) and the controller 1600. The motor housing section 130 extends between and connects the bottoms of the front and rear housing sections 110 and 120 and at least partially encloses and / or supports at least some of the components of the working assembly 200, including the motor 1100. The handle housing section 150 extends between and connects the tops of the front and rear housing sections 110 and 120 and defines a handle shaped to be held by the operator during operation of the strapping device 50. This is merely one example, and in other embodiments the components of the strapping device may be supported and / or enclosed by any suitable portion of the housing 100. The housing 100 may be formed from any suitable quantity of components joined together in any suitable manner. In this example embodiment, the housing 100 is formed from plastic, though it may be made from any other suitable material in other embodiments.

[0018] The working assembly 200, which is best shown in Figure 4, includes the majority of the components of the strapping device 50 that are configured to carry out the strapping cycle to tension the strap around the load, attach the overlapping portions of the strap to one another, and cut the strap from the strap supply. The working assembly 200 includes a support 300, a rocker 350 supporting a toothed tensioning plate 352, a tensioning assembly 400, a sealing assembly 500, a rocker lever 900, a transmission 1000, and a motor 1100.

[0019] The support 300 serves as a direct or indirect common mount for the rocker 350, the tensioning assembly 400, the sealing assembly 500, the rocker lever 900, the transmission 1000, and the motor 1100. The support 300 includes a base 300b and a frame 300f extending above the base 300b. The rocker 350 is pivotably mounted to the frame 300f and pivotable about a rocker-pivot axis A350 between a tensioning position in which the tensioning plate 352 is adjacent to the tension wheel 490 (shown in Figure 4) and an open position in which the tensioning plate 352 is spaced-apart from the tension wheel 490 (not shown). A spring or other suitable biasing element biases the rocker 350 to the tensioning position. The rocker lever 900 is operably connected to the rocker 350, such as via suitable linkages and / or gearing, such that the rocker lever 900 forces the rocker 350 to move from the tensioning position to the open position when the rocker lever 900 is pulled by an operator (not shown). In other embodiments, the motor is operably connected to the rocker and configured to move the rocker from the tensioning position to the open position when the rocker lever is pulled (or another suitable input device is actuated). The base 300b of the support 300 supports a toothed weld plate 302 below the weld shoe 520 of the sealing assembly 500 (described below).

[0020] The tensioning assembly 400, which is best shown in Figures 5A-6, is operable (via the motor 1100) to tension the strap around the load during the tensioning cycle. The tensioning assembly 400 includes a driven shaft 420; a driven gear 424; a Wolfram planetary gear set 440; a tension wheel 490; and bearings 400a, 400b, 400c, and 400d. The Wolfram planetary gear set 440 includes a sun gear 442; a ring gear 444 including inner teeth 444it; a carrier 446; first, second, and third planet gears 452, 454, and 456; and first, second, and third planet-gear shafts 452s, 454s, and 456s.

[0021] The first planet gear 452 includes a cylindrical body 452b having circumferentially arranged first teeth 452tl at one end and circumferentially arranged second teeth 452t2 at the opposite end. In this example embodiment, the first and second teeth 452t l and 452t2 are spaced-apart in the axial direction of the first planet gear 452, though in other embodiments they may be adjacent to one another. The second planet gear 454 includes a cylindrical body 454b having circumferentially arranged first teeth 454t 1 at one end and circumferentially arranged second teeth 454t2 at the opposite end. In this example embodiment, the first and second teeth 454tl and 454t2 are spaced-apart in the axial direction of the second planet gear 454, though in other embodiments they may be adjacent to one another. The thirdplanet gear 456 includes a cylindrical body 456b having circumferentially arranged first teeth 456t 1 at one end and circumferentially arranged second teeth 456t2 at the opposite end. In this example embodiment, the first and second teeth 456t 1 and 456t2 are spaced-apart in the axial direction of the third planet gear 456, though in other embodiments they may be adjacent to one another. In this example embodiment, the first teeth of all three planet gears are identical and the second teeth of all three planet gears are identical. In certain embodiments, the first and second teeth are identical, whereas in other embodiments, the first and second teeth are different. In various embodiments, some or all of the planet gears are different from one another. The quantity and characteristics of the teeth may be selected to achieve the desired gear reduction. In certain embodiments, there is a profile shift from the first teeth to the second teeth of one or more of the planet gears.

[0022] The driven gear 424, which is a bevel gear in this example embodiment but may be any suitable gear in other embodiments, is mounted to one end of the driven shaft 420 such that the driven gear 424 is fixed in rotation with the driven shaft 420. In this example embodiment, the driven gear 424 is fixed in place on the drive shaft 420 via first and second set screws 424fl and 424f2, though it may be mounted the drive shaft 420 in any other suitable manner in other embodiments. In other embodiments, the driven gear is integrally formed with the drive shaft 420. Similarly, the sun gear 442, which is a spur gear in this example embodiment but may be any other suitable gear in other embodiments, is mounted to the driven shaft 420 such that sun gear 442 is fixed in rotation with the driven shaft 420. In this example embodiment, the sun gear 442 is fixed in place on the drive shaft 420 via first and second set screws 442fl and 442f2, though it may be mounted the drive shaft 420 in any other suitable manner in other embodiments. The first, second, and third planet gears 452, 454, and 456 are mounted to the first, second, and third planet-gear shafts 452s, 454s, and 456s, respectively, such that they may rotate around the longitudinal axes of their respective shafts. The first, second, and third planet-gear shafts 452s, 454s, and 456s are, in turn, received in and mounted to the carrier 446. The tension wheel 490 includes an annular body 492 including inner teeth 494 and a cylindrical outer surface 496. The outer surface 496 is textured (such as toothed or knurled) in this example embodiment to increase the friction between the strap and the outer surface.

[0023] The driven shaft 420 is rotatably supported by the inner race of the bearing 400a (though embodiments do not include this bearing). The outer race of the bearing 400a ispress-fit into the support 300 such that the driven shaft 420 is rotatable relative to the support 300 about a tension-wheel axis A490. Although not include in this example embodiment, in certain embodiments the driven shaft extends through and is engaged by a freewheel that is press-fit into and supported by the support. In these embodiments, the freewheel is configured to permit rotation of the driven shaft relative to the support and about the tension-wheel axis A490 in a tensioning rotational direction and to prevent rotation of the driven shaft in the opposite rotational direction. The sun gear 442 drivingly engages the first, second, and third planet gears 452, 454, and 456 via the teeth of the sun gear 442 meshing with the first teeth 452tl, 454tl, and 456t 1 of the first, second, and third planet gears 452, 454, and 456. The first, second, and third planet gears 452, 454, and 456 are circumferentially spaced about the tension-wheel axis A490 and substantially aligned in the axial direction. The first teeth 452tl, 454tl, and 456tl of the first, second, and third planet gears 452, 454, and 456 mesh with the inner teeth 444it of the ring gear 444, which is rotatably supported by the bearings 400b and 400c press-fit onto the support 300. The first, second, and third planet gears 452, 454, and 456 drivingly engage the tension wheel 490 via the second teeth 452t2, 454t2, and 456t2 of the first, second, and third planet gears 452, 454, and 456 meshing with the inner teeth 494 of the tension wheel 490. The tension wheel 490 is rotatably supported by the bearing 400d, which is press-fit into and supported by the support 300, such that the tension wheel 490 is rotatable relative to the support 300 about the tensionwheel axis A490. The tension wheel 490 is held in place axially (in the direction of the tensionwheel axis A490) via a suitable retainer and suitable fasteners (not shown for clarity).

[0024] In certain embodiments, the Wolfrom planetary gear set includes a second sun gear fixed in rotation with the driven shaft that drivingly engagers the second teeth of the first, second, and third planetary gears. Specifically, the teeth of the second sun gear mesh with the second teeth of the planetary gears.

[0025] The Wolfrom planetary gear set 440 is configured to convert a relatively high-speed, low torque input — here, rotation of the driven shaft 420 — into a relatively low- speed, high-torque output — here, rotation of the tension wheel 490. Put differently, the input to the Wolfrom planetary gear set 440 has an input rotational speed and an input torque. The Wolfrom planetary gear set 440 is configured to convert that input into an output having an output rotational speed lower than the input rotational speed and an output torque that is higher than the input torque. In operation, when the driven shaft 420 rotates about the tension-wheelaxis A490, the sun gear 442 rotates with it. The sun gear 442 — via its driving engagement with the first sets of teeth 452tl, 454tl, and 456tl of the first, second, and third planet gears 452, 454, and 456 — drives the first, second, and third planet gears 452, 454, and 456 to rotate about their respective first, second, and third planet-gear shafts 452s, 454s, and 456a. During the tensioning process, a suitable decoupling assembly (not shown) fixes the ring gear 444 in rotation about the tension-wheel axis A490. Accordingly, the first, second, and third planet gears 452, 454, and 456 travel around the inner teeth 444it of the stationary ring gear 444 and rotate about the tensionwheel axis A490 as they also rotate about the longitudinal axes of their respective shafts 452s, 454s, and 456s. Because the second sets of teeth 452t2, 454t2, and 456t2 of the first, second, and third planet gears 452, 454, and 456 mesh with the inner teeth 494 of the tension wheel 490, this dual rotation of the planet gears drives the tension wheel 490 to rotate about the tension-wheel axis A490.

[0026] In this example embodiment, the size, shape, and configuration of the sun, planet, and ring gears results in a reduction ratio of approximately 60: 1 such that the rotational speed of the tension wheel 490 is approximately 1 / 60 the rotational speed of the driven shaft 420. Put differently, the ratio of the output rotational speed of the tension wheel 490 to the input rotational speed of the driven shaft 420 is approximately 1 :60. This is merely one example configuration, and the reduction ratio may be any other suitable ratio in other embodiments, such as between 15: 1 and 80: 1.

[0027] “Rotational speed” in this specification means unloaded rotational speed; that is, rotational speed of the referenced components when they are not tensioning a strap.

[0028] The use of a Wolfrom planetary gear set to convert the relatively high-speed, low-torque input of the driven shaft to the relatively low-speed, high-torque output of the tension wheel improves upon certain existing strapping tools that use serial involute planetary gear sets to obtain a desired reduction ratio. Specifically, this reduces complexity, decreases manufacturing costs, decreases assembly time, lowers the weight of the strapping tool thereby reducing operator fatigue, and enables the tensioning assembly to fit into a more compact space. Another benefit is that the Wolfrom planetary gear set resists being driven backwards. This resistance reduces the stress on certain components of the strapping device after the tensioning cycle has finished and tension is being held in the strap during the sealing cycle.

[0029] The sealing assembly 500, shown in Figure 4, is configured to attach overlapping portions of the strap to one another to form a tensioned strap loop around the load during the sealing cycle via friction welding. The sealing assembly 500 includes a weld arm 510, a weld shoe 520, a cutter, a linkage, and an eccentric shaft. The weld shoe 520 is slidably mounted to the weld arm 510 such that the weld shoe 520 can oscillate relative to the weld arm 510. The cutter is mounted to the weld arm 510. The weld arm 510 is pivotably mounted to the support 300 and is pivotable relative to the support 300 and the weld plate 302 between a home position (not shown) in which the weld shoe 520 is spaced-apart from the weld plate 302 and a welding position (Figure 4) in which the weld shoe 520 is adjacent the weld plate 302 and positioned to weld the strap. The linkage operably connects the transmission 1000 to the weld arm 510 such that the transmission 1000 can move the weld arm 510 from the home position to the welding position (and vice-versa in certain embodiments). The eccentric shaft is operably connected to the weld shoe 520 and configured to, when rotated, cause the weld shoe 520 to oscillate. A toothed belt operably connects the transmission 1000 to the eccentric shaft to rotate the eccentric shaft.

[0030] The transmission 1000, shown in Figures 4 and 7, is driven by the motor 1100, is operably connected to the tensioning assembly 400 and configured to cause the tension wheel 490 to rotate in the tensioning rotational direction to tension the strap, and is operably connected to the sealing assembly 500 and configured to cause the sealing assembly 500 to attach the overlapping portions of the strap to one another. The transmission 1000 is supported by the support 300 in any suitable manner (such as via one or more bearings) and includes transmission gearing including a drive gear 1010, which is a bevel pinion gear in this example embodiment.

[0031] The transmission gearing includes suitable components (such as gears, bearing, and freewheels) configured to transmit rotational movement of the output shaft of the motor 1100 (described below) in a first drive direction to the drive gear 1010 to rotate the drive gear 1010 but not to drive any components of the sealing assembly 500 in this example embodiment. The drive gear 1010 is drivingly engaged with the driven gear 424 of the driven shaft 420 of the tensioning assembly 400 and, when driven by the motor 1100, drives the driven shaft 420 to rotate. This causes the tension wheel 490 to rotate in the tensioning rotational direction to tension the strap, as explained above. The components of the transmission gearing1010 are configured to transmit rotational movement of the output shaft of the motor 1100 in a second drive direction opposite the first drive direction to: (1) the linkage of the sealing assembly 500 to move the weld arm 510 from its home position to its welding position; and (2) the toothed belt to rotate the eccentric shaft and cause the weld shoe 520 to oscillate. These components prevent transmission of rotational movement of the output shaft of the motor 1100 in the second drive direction to the drive gear 1010 in this example embodiment.

[0032] This is merely one example transmission assembly, and the strapping device may include any suitable transmission assembly or assemblies operably connecting one or more motors to the tensioning and sealing assemblies to drive those assemblies.

[0033] The motor 1100, which is shown in Figures 4 and 7, is operably connected to the tensioning assembly 400 and the sealing assembly 500 via the transmission 1000 and is configured to drive those assemblies, as explained above. The motor 1100 includes the output shaft (not shown) referenced above. The motor 1100 is an electric motor in this example embodiment but may be any other suitable motor in other embodiments.

[0034] The display assembly 1490, which is shown in Figures 1 and 2, includes a display screen 1492 and a touch panel 1494. The display screen 1492 is configured to display information regarding the strapping device 50, and the touch screen 1494 is configured to receive operator inputs such as a desired strap tension and desired weld cooling time. In certain embodiments, a display controller controls the display screen 1492 and the touch panel 1494 and is communicatively connected to the controller 1600 and configured to send signals to the controller 1600 and to receive signals from the controller 1600. Other embodiments of the strapping device do not include a touch panel. Still other embodiments of the strapping device do not include a display assembly. Certain embodiments of the strapping device include a separate pushbutton panel instead of a touch panel beneath or integrated with the display screen.

[0035] The first and second pushbutton actuators 1410 and 1440 are operable to initiate the tensioning and / or sealing cycles as described below. Other embodiments of the strapping device 50 do not have pushbutton actuators and instead incorporate their functionality into the display assembly 1490. For instance, in one of these embodiments two areas of the touch panel define virtual buttons that have the same functionality as mechanical pushbutton actuators.

[0036] The controller 1600, which is shown in Figure 2, includes a processing device (or devices) communicatively connected to a memory device (or devices). For instance,the controller may be a programmable logic controller. The processing device may include any suitable processing device such as, but not limited to, a general-purpose processor, a specialpurpose processor, a digital-signal processor, one or more microprocessors, one or more microprocessors in association with a digital-signal processor core, one or more applicationspecific integrated circuits, one or more field-programmable gate array circuits, one or more integrated circuits, and / or a state machine. The memory device may include any suitable memory device such as, but not limited to, read-only memory, random-access memory, one or more digital registers, cache memory, one or more semiconductor memory devices, magnetic media such as integrated hard disks and / or removable memory, magneto-optical media, and / or optical media. The memory device stores instructions executable by the processing device to control operation of the strapping device 50. The controller 1600 is communicatively and operably connected to the motor 1100, the display assembly 1490, the pushbutton actuators 1410 and 1440, and the sensor(s) 1700 and configured to receive signals from and to control those components. The controller 1600 may also be communicatively connectable (such as via Wi-Fi, Bluetooth, near-field communication, or other suitable wireless communications protocol) to an external device, such as a computing device, to send information to and receive information from that external device.

[0037] The controller 1600 is configured to operate the strapping device in one of three operating modes to carry out the strapping cycle: (1) a manual operating mode; (2) a semiautomatic operating mode; and (3) an automatic operating mode. In the manual operating mode, the controller 1600 operates the motor 1100 to cause the tension wheel 490 to rotate responsive to the first pushbutton actuator 1410 being actuated and maintained in its actuated state. The controller 1600 operates the motor 1100 to cause the sealing assembly 500 to carry out the sealing cycle responsive to the second pushbutton actuator 1 being actuated. In the semiautomatic operating mode, the controller 1600 operates the motor 1100 to cause the tension wheel 490 to rotate responsive to the first pushbutton actuator 1410 being actuated and maintained in its actuated state. Once the controller 1600 determines that the tension in the strap reaches the (preset) desired strap tension, the controller 1600 automatically operates the motor 1100 to cause the sealing assembly 500 to carry out the sealing cycle without requiring additional input from the operator. In the automatic operating mode, the controller 1600 operates the motor 1100 to cause the tension wheel 490 to rotate responsive to the first pushbuttonactuator 1410 being actuated. Once the controller 1600 determines that the tension in the strap reaches the (preset) desired strap tension, the controller 1600 automatically operates the motor 1100 to cause the sealing assembly 500 to carry out the sealing cycle without requiring additional input from the operator.

[0038] The sensors 1700 include any suitable sensors, such as microswitches, optical sensors, ultrasonic sensors, magnetic position sensors, and the like, configured to detect the position of certain components of the strapping device 50 and to send appropriate signals to the controller 1600. The sensors 1700 may include, for instance: one or more rocker-position sensors configured to detect when the rocker 350 is in its tensioning position and / or its open position; one or more rocker-lever-position sensors configured to detect the position of the rocker lever 900; and one or more actuating assembly sensors configured to detect actuation of the first and second pushbutton actuators 1410 and 1440.

[0039] The power supply is electrically connected to (via suitable wiring and other components) and configured to power several components of the strapping device 50, including the motor 1100, the display assembly 1490, the controller 1600, and the sensor(s) 1700. The power supply includes a rechargeable battery (such as a lithium-ion or nickel cadmium battery) in this example embodiment, though it may be any other suitable electric power supply in other embodiments. The power supply is sized, shaped, and otherwise configured to be received in the receptacle defined by the rear housing section 120 of the housing 100. The strapping device 50 includes one or more power-supply-securing devices (not shown) to releasably lock the power supply in place upon receipt in the receptacle. Actuation of a release device of the strapping device 50 or the power supply unlocks the power supply from the housing 100 and enables an operator to remove the power supply from the receptacle.

[0040] Use of the strapping device 50 to form a tensioned strap loop around a load is described below. Initially, the rocker 350 is in its tensioning position. The strapping device 50 is in the automatic mode for the purposes of this example.

[0041] The operator pulls the strap leading end first from a strap supply (not shown), wraps the strap around the load, and positions the leading end of the strap S below another portion of the strap to form upper and lower portions of strap. The operator then pulls the rocker lever 900, which causes the rocker 350 to move from its tensioning position to its open position. With the rocker 350 its open position and while continuing to hold the rocker lever 900, theoperator introduces the overlapping upper and lower portions of the strap between the tension wheel 490 and the tension plate 352 and between the weld shoe 520 and the weld plate 302. The operator then releases the rocker lever 900, enabling the appropriate biasing elements to force the rocker 350 to return to its strap-tensioning position to trap the upper and lower portions of the strap between the tensioning plate 352 and the outer surface 496 of the tension wheel 490.

[0042] The operator then actuates the first pushbutton actuator 1410. Once one of the sensors 1700 detects the actuation of the first pushbutton actuator 1410, the controller 1600 initiates the strapping cycle. The controller 1600 starts the tensioning cycle by controlling the motor 1100 to rotate the output shaft in the first drive direction. As explained above, the transmission 1000 transmits this rotational movement of the output shaft to the driven shaft 420 of the tensioning assembly 400, which results in the tension wheel 490 rotating about the tension-wheel axis A490 in the tensioning rotational direction as described above. As the tension wheel 490 rotates, it pulls the upper portion of the strap S over the lower portion of the strap S, thereby tensioning the strap S around the load. Throughout the tensioning cycle, the controller 1600 monitors the current drawn by the motor 1100. When this current reaches a preset value that is correlated with the preset desired strap tension for this strapping cycle, the controller 1600 stops the motor 1100, thereby terminating the tensioning cycle.

[0043] After completion of the tensioning cycle, the controller 1600 automatically starts the sealing cycle by controlling the motor 1100 to begin rotating the output shaft in the second drive direction. This causes the transmission 1000 to drive the toothed belt to begin rotating the eccentric shaft and oscillating the weld shoe 520 and pivot the weld arm 510 to its welding position. As the weld arm 510 reaches the welding position, the weld shoe 520 forces the overlapping upper and lower layers of strap against the weld plate 302 while the cutter cuts the upper strap layer from the strap supply. The oscillating movement of the weld shoe 520 locally melts the portions of the upper and lower strap layers together. After a preset period of time or a preset quantity of rotations of the motor output shaft, the controller 1600 controls the motor 1100 to stop rotating the output shaft, completing the sealing cycle. After the sealing cycle is complete, the operator again pulls the rocker lever 900, causing the rocker 350 to move from its strap-tensioning position to its open position. The operator then removes the strapping device 50 from the tensioned strap loop.

[0044] While the above-described Wolfrom planetary gear set includes three planet gears, in other embodiments the Wolfrom planetary gear set includes any suitable quantity of two or more planet gears.

[0045] Although the sealing assembly of the above-described example embodiment of the strapping device is configured to form a friction -welded strap joint, the sealing assembly may comprise other sealing mechanisms (such as notching jaw assembly, a crimping jaw assembly, a sealless joint assembly, an ultrasonic welding assembly, or a hot-knife assembly) in other embodiments configured to seal any suitable type of strap (such as metal, plastic, or paper strap).

[0046] The above-described example embodiment of the strapping device includes a single motor configured to drive both the tensioning assembly and the sealing assembly. In other embodiments, the strapping device includes separate motors configured to drive the respective tensioning and sealing assemblies and may include separate transmissions for each motor.

[0047] The above-described example embodiment of the strapping device includes a rocker carrying the tensioning plate that pivots relative to a stationary tensioning assembly. In other embodiments, the tensioning plate is supported by the support of the strapping device, and the rocker carries the tensioning assembly (or at least the tension wheel) and is pivotable relative to the tensioning plate.

[0048] While the strapping device described above is a handheld strapping device, the strapping device may be any other suitable strapping device in other embodiments, such as a standalone automatic or semi-automatic strapping machine.

Claims

Claims1. A strapping device comprising: a rotatable tension wheel; a driven shaft operably connected to the tension wheel to rotate the tension wheel; a motor operably connected to the driven shaft to rotate the driven shaft; and a Wolfrom planetary gear set configured to convert an input rotational speed of the driven shaft to an output rotational speed of the tension wheel, wherein the output rotational speed is less than the input rotational speed.

2. The strapping device of claim 1, wherein the ratio of the output rotational speed to the input rotational speed is approximately 1 : 15 to 1 :80.

3. The strapping device of claim 1, wherein the ratio of the output rotational speed to the input rotational speed is approximately 1 :60.

4. The strapping device of claim 1, wherein the Wolfrom planetary gear set comprises a sun gear, multiple planet gears each comprising first and second teeth, and a ring gear comprising inner teeth, wherein the sun gear drivingly engages the planet gears, wherein the first teeth of the planet gears mesh with the inner teeth of the ring gear.

5. The strapping device of claim 4, wherein the sun gear comprises teeth that mesh with the first teeth of the planet gears.

6. The strapping device of claim 5, wherein the planet gears drivingly engage the tension wheel.

7. The strapping device of claim 6, wherein the second teeth of the planet gears drivingly engage the tension wheel.

8. The strapping device of claim 7, wherein the tension wheel comprises inner teeth, wherein the second teeth of the planet gears mesh with the inner teeth of the tension wheel.

9. The strapping device of claim 8, wherein the tension wheel is rotatable relative to the ring gear.

10. The strapping device of claim 8, further comprising a carrier, wherein the planet gears are rotatably mounted to the carrier.

11. The strapping device of claim 9, wherein the Wolfrom planetary gear set is the only planetary gear set of the strapping device configured to convert the input rotational speed of the driven shaft to the output rotational speed of the tension wheel.

12. The strapping device of claim 9, wherein the tension wheel is rotatable about a tension-wheel axis, wherein the planet gears are circumferentially spaced around and rotatable about the tension-wheel axis, wherein the carrier is rotatable about the tension-wheel axis.

13. The strapping device of claim 12, wherein the driven shaft is rotatable about the tension-wheel axis.

14. The strapping device of claim 13, wherein for each planet gear, the first teeth and the second teeth of that planet gear are adjacent to each other in an axial direction.

15. The strapping device of claim 14, wherein the Wolfrom planetary gear set includes three identical planet gears.

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