Cutlery – Cutting tools – Saw
Reexamination Certificate
1998-08-13
2001-06-26
Rada, Rinaldi I. (Department: 3724)
Cutlery
Cutting tools
Saw
C030S393000, C030S182000
Reexamination Certificate
active
06249979
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention generally relates to reciprocating saws.
Reciprocating saws are used to cut a variety of objects made from a variety of materials, such as metal pipes, wood and dry wall. Such saws generally include a housing and a spindle mounted in the housing for reciprocating motion along an axis that is parallel to the longitudinal extent of the spindle. An electric motor provides power to the spindle through a mechanical reciprocating device that converts the rotary motion of a motor shaft to reciprocating motion. Such mechanical reciprocating devices can, for example, include an eccentric drive, as disclosed in U.S. Pat. No. 5,079,844, or a wobble plate drive, as disclosed in U.S. Pat. Nos. 5,025,562 and 5,050,307. In a typical wobble plate drive, the drive arm of a primary wobble plate has a spherical tip that engages a suitable bore defined in the reciprocating spindle. The drive can also include a secondary wobble plate having a drive arm with a spherical tip engaging a bore defined in a reciprocating counterweight.
In some reciprocating saws, the spindle reciprocates in an orbital motion, as opposed to a straight line reciprocating motion. The orbital motion is commonly characterized by a forward (i.e., in the cutting direction) motion of the saw blade as the saw blade is being retracted toward the saw on the cutting stroke, and a corresponding rearward (i.e., opposite the cutting direction) motion of the saw blade as the saw blade is being extended away from the saw on the return stroke. The result is a circuitous, or orbital, path of the saw blade. Such orbital motion is believed to improve the speed at which the-saw cuts a workpiece by driving the saw blade into the workpiece during the cutting stroke and withdrawing the saw blade from the workpiece during the return stroke.
Orbital motion has been achieved in a number of different ways. For example, in U.S. Pat. Nos. 4,238,884 and 4,628,605, a forward force (in the cutting direction) is applied by a blade roller directly to the saw blade during the cutting stroke, and forward motion of the saw blade is accommodated by a forgiving interconnection between the spindle and the drive mechanism. In U.S. Pat. No. 5,212,887, the spindle reciprocates through a pivotally-mounted bushing, and the back end of the spindle is connected to an eccentric member that provides forward-rearward motion to the spindle. In U.S. Pat. Nos. 4,962,588 and 4,550,501, the back end of the spindle is moved forward-rearward by connection to a cam surface on a rotating gear. In U.S. Pat. No. 5,392,519 the back end of the spindle is moved forward-rearward by connection to an eccentric member formed on the drive gear.
In some orbital reciprocating saws, the orbital motion of the saw blade can be adjusted or disengaged. For example, U.S. Pat. No. 4,550,501 discloses a cam lever located on the side of the saw and operable to adjust the orbital motion of the saw blade. The cam lever is adjusted between a first position, in which the spindle is connected to the cam surface on the rotating gear, and a second position, in which the spindle is disconnected from a portion of the cam surface on the rotating gear.
To accommodate the orbital motion of the spindle, an orbital reciprocating saw typically includes a bearing arrangement for supporting the spindle. For example, U.S. Pat. No. 4,550,501 discloses a bearing block and a slidable bearing insert received within the bearing block. The bearing insert and the bearing block are dimensioned to provide a clearance space in the vertical direction to permit limited relative movement between the bearing insert and the bearing block to accommodate the orbital motion. A separate dust seal is mounted forwardly of the bearing assembly to prevent debris and other contamination from entering the saw housing.
In U.S. Pat. No. 5,212,887, an annular bearing member slidably receives the spindle or plunger assembly of the reciprocating saw. The bearing is received within an annular support mounted on the tool casing. The bearing and the bracket define spaces for receiving O-rings and clearance spaces. The O-rings and the clearance spaces cooperate to provide a swivel or swinging mounting for the plunger assembly to permit oscillatory movement of the plunger assembly. In other bearing arrangements, a spherical bearing may be provided, such as that shown in U.S. Pat. No. 3,945,120.
Some reciprocating saws further include a shoe secured relative to the housing to provide a flat surface for resting against the workpiece during cutting operations. The shoe is positioned near the saw blade, and the flat surface is usually perpendicular to the saw blade. The shoe typically includes an opening through which the blade extends.
In some reciprocating saws, the shoe may be adjustable relative to the length of the saw blade so that the shoe may be located in an optimum position for cutting operations. U.S. Pat. No. 5,421,091 discloses an adjustable guideshoe for a reciprocating saw. The adjustable guideshoe is mounted on a support bar which is received within an elongated slot formed in the nose section of the saw housing. The support bar includes a plurality of sets of opposed cam faces which are provided in side-by-side pairs spaced longitudinally along the bar. A manually operated plunger is mounted in the nose section and is spring biased toward the support bar. The plunger bar includes cam surfaces adapted for complementary wedging engagement with selected sets of cam faces on the support bar to achieve a self-locating function for the support and guideshoe mounted thereon.
SUMMARY OF THE INVENTION
The reciprocating saws described above have several problems.
For example, in a reciprocating saw with a wobble plate drive, the wobble plate drive arm and the spindle bore are machined with tight tolerances to extend the life of the saw and also to maintain acceptable noise levels. The required machining increases the cost of manufacturing the saw. Also, as the joint between the wobble plate drive arm and the spindle bore wears, the tight tolerance of the joint is lost so that wear of the saw increases. The loose joint between the drive arm and the spindle bore also causes increased noise.
One problem with a reciprocating saw having an orbital drive system in which cam member is fixed to the drive shaft is that the cam member is not replaceable or interchangeable without changing the attached drive shaft and/or drive gear. The lack of replaceability is a problem because the cam member is subject to wear due to the pressure applied during orbital cutting operations (i.e., when the saw blade is plunged into the workpiece). The lack of interchangeability is a problem because another cam member having a different cam configuration may provide a preferred orbital path for the saw blade for a given cutting operation.
One problem with the adjustment of an orbital reciprocating saw is that previous orbital actuation levers are typically located on one side of the tool. As a result, the operator can only activate the lever from that side of the saw.
One problem with the bearing assemblies that accommodate orbital motion in a reciprocating saw is that the bearing assemblies are difficult to assemble and increase the cost of manufacturing the saw. Another problem with some of these bearing assemblies is that they do not provide a good seal to prevent contaminants and debris from entering the saw housing.
One problem with some adjustable shoe assemblies for reciprocating saws is that these assemblies do not provide fine increments of adjustment to allow the shoe to be placed in the optimal position. Another problem with some of these adjustable shoe assemblies is that they require additional tools, such as a wrench or a key, for adjustment. Yet another problem with some of these shoe adjustment assemblies is that the adjustment mechanism or lever is accessible from only one side of the saw so that the operator can use only one hand to actuate the adjustment lever. A further problem with some of these shoe adjust
Bednar Thomas Richard
Neitzell Roger Dean
Steele Michael Scott
Flores-Saánchez Omar
Michael & Best & Friedrich LLP
Milwaukee Electric Tool Corporation
Rada Rinaldi I.
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