Reciprocating tool having offset spur gear and counterweighting assembly

Patent metadata

Field	Value
Publication number	US-12466048-B2
Application number	US-202318396926-A
Country	US
Kind code	B2
Filing date	Dec 27, 2023
Priority date	Dec 27, 2023
Publication date	Nov 11, 2025
Grant date	Nov 11, 2025

Abstract

A reciprocating power tool includes a transmission that converts rotational force from a motor to linear forces output by a reciprocating device and a counterbalancing device. The transmission is a parallel axis transmission including a first gear portion and a second gear portion formed on a gear shaft, with the first gear portion and the second gear portion rotating together about a first rotational axis. The first gear portion rotates a first output gear and the second gear portion rotates a second output gear about a second rotational axis that is parallel to and offset from the first rotational axis. The first output gear drives the reciprocating device and the second output gear drives the counterbalancing device. The reciprocating device reciprocates linearly and the counterbalancing devices performs a linear reciprocating movement that is opposite that of the reciprocating device to counterbalance forces generated by operation of the reciprocating device.

First claim

What is claimed is:

1 . A reciprocating power tool, comprising:
a motor; a reciprocating device; a counterbalancing device; and a transmission coupled between the motor and the reciprocating device, and between the motor and the counterbalancing device, wherein the transmission includes a gear shaft configured to rotate in response to a driving force from the motor, the gear shaft including:
a first gear portion formed on a first portion of the gear shaft, the first gear portion driving a first output gear, the first output gear driving the reciprocating device; and
a second gear portion formed on a second portion of the gear shaft, the second gear portion driving a second output gear, the second output gear driving the counterbalancing device.

2 . The reciprocating power tool of claim 1 , wherein the gear shaft rotates about a first axis of rotation and the first output gear and the second output gear rotate about a second axis of rotation that is offset from and in parallel to the first axis of rotation.

3 . The reciprocating power tool of claim 1 , wherein a linear reciprocating direction of the counterbalancing device is opposite a linear reciprocating direction of the reciprocating device so as to balance a linear reciprocating movement of the reciprocating device.

4 . The reciprocating power tool of claim 1 , wherein a configuration of the first gear portion corresponds to a configuration of the second gear portion, and a configuration of the first output gear corresponds to a configuration of the second output gear, such that a rotational speed output by the first output gear corresponds to a rotational speed of the second output gear.

5 . The reciprocating power tool of claim 1 , wherein a linear reciprocating direction of the reciprocating device and a linear reciprocating direction of the counterbalancing device is substantially orthogonal to a first axis of rotation of the gear shaft and a second axis of rotation of the first output gear and the second output gear.

6 . The reciprocating power tool of claim 5 , wherein the reciprocating device includes:
a reciprocating shaft positioned between the first output gear and the second output gear; and a pin fixed to the first output gear and coupled in a slot formed in a yoke portion of the reciprocating shaft, wherein the pin is eccentrically positioned relative to the second axis of rotation.

7 . The reciprocating power tool of claim 6 , wherein the pin is movably received in the slot formed in the yoke portion of the reciprocating shaft, such that the pin is configured to move in the slot formed in the yoke portion of the reciprocating shaft in response to rotation of the first output gear about the second axis of rotation, and the reciprocating shaft is configured to perform a linear reciprocating movement in response to movement of the pin in the slot formed in the yoke portion of the reciprocating shaft.

8 . The reciprocating power tool of claim 6 , wherein the counterbalancing device includes:
a counterweight member positioned between the second output gear and the reciprocating shaft, the counterweight member including a slot formed on a side portion of the counterweight member facing the second output gear, and a protrusion formed on the second output gear, eccentrically positioned with respect to the second axis of rotation, wherein the protrusion is movably received in the slot formed in the counterweight member.

9 . The reciprocating power tool of claim 8 , wherein the protrusion is configured to move in the slot formed in the counterweight member in response to rotation of the second output gear about the second axis of rotation and the counterweight member is configured to perform a linear reciprocating movement in response to movement of the protrusion in the slot formed in the counterweight member.

10 . The reciprocating power tool of claim 8 , wherein the protrusion is positioned approximately 180 degrees from the pin with respect to the second axis of rotation.

11 . The reciprocating power tool of claim 8 , wherein
the reciprocating shaft is configured to reciprocate linearly in response to rotation of the first output gear and movement of the pin in the slot formed in the yoke portion of the reciprocating shaft, and the counterweight member is configured to reciprocate linearly in response to rotation of the second output gear about the second axis of rotation movement of the protrusion in the slot formed in the counterweight member, the linear reciprocating direction of the counterweight member being opposite the linear reciprocating direction of the reciprocating shaft.

12 . The reciprocating power tool of claim 8 , wherein the counterweight member also includes:
a recess formed in a first end portion of the counterweight member and configured to receive a coupling portion of the reciprocating shaft; and an opening formed in a second end portion of the counterweight member and configured to selectively receive an intermediate portion of the gear shaft, between the first gear portion and the second gear portion, as the counterweight member reciprocates.

13 . The reciprocating power tool of claim 8 , further comprising a rail guide positioned between the counterweight member and the reciprocating shaft, the rail guide including:
a first rail seated on a first stepped portion at a first lateral side of the counterweight member; a first guide slot formed in the first rail; a second rail seated on a second stepped portion at a second lateral side of the counterweight member; and a second guide slot formed in the second rail, wherein the first guide slot and the second guide slot are positioned so as to guide reciprocating movement of the yoke portion of the reciprocating shaft and restrict rotation of the reciprocating shaft.

14 . The reciprocating power tool of claim 1 , wherein the transmission also includes:
a pinion gear coupled to an output shaft of the motor and configured to rotate in response to the driving force generated by the motor; a spur gear mounted on an end portion of the gear shaft and in meshed engagement with the pinion gear, wherein the spur gear and the gear shaft are configured to rotate in response to rotation of the pinion gear, the first output gear is configured to rotate in response to rotation of the gear shaft and first gear portion formed thereon to drive the reciprocating device, and the second output gear is configured to rotate in response to rotation of the gear shaft and second gear portion formed thereon to drive the counterbalancing device.

15 . The reciprocating power tool of claim 1 , wherein:
a position of the first output gear is set by a first alignment fixture that extends through an opening in a first portion of a housing of the power tool and into an opening formed in the first output gear, with key features formed on an external portion of the first alignment fixture corresponding to key features formed on an internal portion of the opening formed in the first output gear into which the first alignment fixture is inserted; and a position of the second output gear is set by a second alignment fixture that extends through a second opening in a second portion of the housing of the power tool and into an opening formed in the second output gear, with key features formed on an external portion of the second alignment fixture corresponding to key features formed on an internal portion of the opening formed in the second output gear into which the second alignment fixture is inserted.

16 . The reciprocating power tool of c

Assignees

• Black & Decker Inc

Inventors

• Kuehne Brent A
• Qian Zhicheng
• Bao Xin
• Wang Shihuai
• Qiu Dongrong
• Xu Jiachao

Classifications

• F16F15/28

  Counterweights, {i.e. additional weights counterbalancing inertia forces induced by the reciprocating movement of masses in the system, e.g. of pistons attached to an engine crankshaft (rotating balancer shafts F16F15/264; correcting-weights for balancing rotating bodies F16F15/32)}; Attaching or mounting same · CPC title

• B23D51/16

  of drives or feed mechanisms for straight tools, e.g. saw blades, or bows · CPC title

• B23D51/161

  with dynamic balancing · CPC title

• B25F5/006 Primary

  Vibration damping means · CPC title

• B23D49/165 Primary

  with means to move the saw blades in an orbital path · CPC title