Cutlery – Cutting tools – Saw
Reexamination Certificate
1998-04-09
2001-09-11
Peterson, Kenneth E. (Department: 3724)
Cutlery
Cutting tools
Saw
C030S220000, C083S748000
Reexamination Certificate
active
06286217
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to reciprocating saws and more particularly to a drive train for such saws.
BACKGROUND OF THE INVENTION
Inline reciprocating saws. Inline saws have the motor axis and the axis of reciprocation of the blade parallel and the driving of the blade output shaft changes the center of gravity of the saw and generates high vibration. Without counterbalancing of the drive train, such vibration requires the speed of the blade to be limited to keep the vibration to an acceptable level. Accordingly, high performance reciprocating saws often incorporate counterbalancing to reduce the vibration caused by the reciprocation of the drive train for the blade. With counterbalancing, higher blades speeds and higher cutting rates can be achieved with an acceptable level of vibration.
Examples of counterbalanced reciprocating saws are disclosed in U.S. Pat. No. 5,079,844; U.S. Pat. No. 5,025,562; and U.S. Pat. No. 3,945,120. As disclosed in these patents, it is known to use wobble plate, bevel gear, and cam drives to drive the output shaft and counterbalance of the saw. Acceptable performance can be achieved using such drive trains. However, further improvement of such drive trains is desirable. Low cost, simplicity of design, light weight, low vibration, and compactness are continuing design objectives in the design of improved, commercially acceptable drive trains for counterbalanced, inline reciprocating saws.
SUMMARY OF THE INVENTION
The present invention has multiple aspects. According to one aspect of the invention, a reciprocation saw comprises an output shaft mounted for reciprocal motion in a housing. A counterweight is mounted in the housing for reciprocal movement relative to the output shaft. A first drive is connected between a motor and the output shaft for reciprocally driving the output shaft. A second drive is connected between the motor and the counterweight for reciprocally driving the counterweight. One of the first and second drives comprises a pivot arm pivotally mounted about an axis transverse to the output shaft for receiving at a first location a reciprocating input in a first direction and for producing at a second location a reciprocating output in a second direction different from the first direction.
Preferably the one of the drives including the pivot arm (“pivot arm drive”) is the second drive for driving the counterweight. A pivot arm drive may also be used to drive the output shaft in addition to the counterweight. The pivot arm may comprises a cross bar with at least one and preferably two posts at one end of the arm and a lifter rod at the other end of the arm. In the preferred embodiment, the counterweight is saddle shaped and is slidably mounted on the output shaft. The posts are connected to two rearwardly extending legs of the counterweight.
Preferably the pivot arm drive includes (1) a cam fixed to a drive shaft connected to the motor and (2) sleeve fixed against rotation in the housing and mounted on and permitting rotation of the cam. The sleeve provides a linear reciprocating input to the second end of the pivot arm.
Preferably the first drive is a wobble plate drive and both the first and second drives are driven by a common drive shaft.
According to a second aspect of the invention, a reciprocating saw comprises an output shaft mounted for reciprocal motion fore and aft in a housing. A drive shaft is drivable by a motor and mounted in the housing for rotary motion about a first axis. A first drive for reciprocally driving the output shaft is connected between the drive shaft and the output shaft. A counterweight is slidably mounted in the housing and reciprocally drivable relative to the output shaft. A second drive is connected between the counterweight and the output shaft for reciprocally driving the counterweight. One of the first and second drives comprises a cam lifter including: a cam rotatable with the drive shaft; and a sleeve fixed against rotation relative to the housing, mounted on the cam and movable in a linear reciprocating direction transverse to the first axis when the cam is driven by the drive shaft.
Preferably the one drive of the first and second drives including the cam lifter is the second drive. The one drive preferably includes a pivot arm as described above in connection with the first aspect of the invention.
According to a third aspect of the present invention, a drive train for a reciprocating saw comprises a drive shaft connected to and drivable by a motor for rotation about a first axis. A cam is fixed to and drivable by the drive shaft. A sleeve is fixed in the housing against rotation relative to the drive shaft, is mounted on and permits rotation of the cam. The sleeve generates a linear reciprocating output along a second axis generally transverse to the first axis when the cam is rotated by the drive shaft. A pivot arm is pivotably mounted in the housing about a third axis transverse to the first and second axes for transferring and changing the direction of the reciprocating output of the sleeve. The pivot arm has a first end for providing an arcuate reciprocating output and a second end connected to the sleeve for receiving the linear reciprocating output from the sleeve.
The drive train is preferably used for the driving of a counterbalance for the reciprocating saw. Although the pivot arm drive is preferred for use in a counterbalanced saw, the drive may also be used to drive the output shaft in a reciprocating saw without counterbalancing.
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Mechanisms & Mechanical Devices Sourcebook, Copyright 1991, p. 95, Cover and Copyright Pages, month unknown.
Dassoulas Stephen C.
Nickels, Jr. Richard C.
Black & Decker Inc.
Leary Michael P.
Peterson Kenneth E.
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