Abstract:
A reciprocating saw including a housing, a spindle mounted for reciprocation relative to the housing and having a front end adapted to support a saw blade, the spindle being movable through a cutting stroke and a return stroke, a motor for moving the spindle in a reciprocating fashion, and a reciprocating member interconnecting the motor with the spindle. The motor and the spindle define a drive force path from the motor to the spindle and passing through drive force bearing components of the reciprocating saw, and wherein at least part of the reciprocating member is in the drive force path. The reciprocating member is configured to counterbalance the spindle. A pivot body interconnects the spindle with the motor. A shock absorber is operatively positioned between the motor and the front end of the spindle, and is at least partially mounted within the spindle.

Description:
FIELD OF THE INVENTION 
     The invention relates to reciprocating saws, and more particularly to the drive mechanisms of reciprocating saws. 
     BACKGROUND OF THE INVENTION 
     Reciprocating saws are used to cut a variety of objects, such as metal pipes, wood and drywall. Such saws typically 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 of the spindle. Such mechanical reciprocating devices can, for example, include an eccentric drive, as disclosed in U.S. Pat. No. 5,079,844, or wobble plate drive, as disclosed in U.S. Pat. Nos. 5,025,562 and 5,050,307. 
     In addition to various types of drive mechanisms, there are also various types of reciprocating motion. For example, the simplest type is straight linear motion, in which the spindle and blade are translated along a linear path parallel to the spindle and returned along the same path. Alternatively, rocking motion is motion in which the spindle and blade are translated and returned along a path oblique to the spindle axis. Such motion may be straight or curved, and may help to drive the saw blade into the workpiece on the cutting stroke and retract the blade on the return stroke. As another alternative, orbital motion is motion in which the spindle and saw blade are translated along a cutting path and returned along a different path. Typically, the paths form a loop-type movement that forces the saw blade into the workpiece on the cutting stroke and then lifts the saw blade off the workpiece on the return stroke. All of these types of movement involve some reciprocation of the saw blade and are therefore considered to be a form of reciprocating motion. 
     The reciprocating motion of the spindle, and other components attached to the spindle such as the saw blade and drive components, causes vibration of the saw. Such vibration makes relative positioning of the saw to the work piece difficult, and can be significant in the case of hand held saws. Therefore, it is known to use a counterbalance that provides an inertial force opposed to the primary reciprocating inertial force. For example, in U.S. Pat. No. 5,025,562 issued Jun. 25, 1991 to Palm, a reciprocating saw is disclosed including a counterbalanced reciprocating drive having a jack shaft on which primary and secondary wobble plates are mounted. The primary wobble plate drives the spindle, and the secondary wobble plate drives a mass in a direction opposed to the spindle movement. 
     SUMMARY OF THE INVENTION 
     Incorporation of a counterbalance into prior art mechanical reciprocating devices, such as eccentric drives and wobble plate drives, can be complex and expensive. Further, the introduction of additional mechanisms into the devices can create another potential point of failure. Accordingly, it is an object of the present invention to design a saw that provides an improved drive mechanism without necessarily adding weight, cost, or complexity. It is a related object of the present invention to provide a reciprocating saw drive mechanism that may be inherently counterbalanced, i.e., the counterbalance is integral to the drive mechanism itself, thus not requiring additional moving parts. It is a further object of the present invention to provide a drive mechanism that incorporates a shock absorbing feature without adding significant weight, cost, or expense. 
     In accordance with these objectives, the invention provides a reciprocating saw comprising a housing, a spindle mounted for reciprocation relative to the housing, a motor for moving the spindle in a reciprocating fashion, and a reciprocating member interconnecting the motor with the spindle. The reciprocating member is adapted to move in a direction that is at least partially opposed to the direction of the spindle movement, and the motor and the spindle define a drive force path from the motor to the spindle, and at least part of the reciprocating member is in the drive force path. The reciprocating member may thereby be configured to counterbalance movement of the spindle. For example, the reciprocating member may have substantially the same mass as the spindle. 
     In one embodiment, the reciprocating member defines an axis and the spindle defines an axis, and the reciprocating member axis is offset from the spindle axis. The reciprocating member axis may be substantially parallel to the spindle axis. The reciprocating saw may further comprise a drive shaft that is driven by the motor wherein the reciprocating member is driven by the drive shaft. For example, the reciprocating member may comprise a barrel cam. 
     In one aspect, the saw can further include an actuating member in the form of a pivot body having a first end interconnected with the spindle and a second end driven by the motor. The pivot body can be mounted at a pivot point between the first and second ends. The pivot body may be movable perpendicular to pivot axis to thereby vary the extent to which the spindle is driven. 
     In yet another aspect, the saw includes a shock absorber mounted on the spindle and operatively positioned between the motor and the front end to at least partially absorb impact to the front end. The shock absorber may interconnected between the front end and an actuating member, and may be at least partially mounted within the spindle. Preferably, the shock absorber comprises an elastomeric cushion. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side view of a reciprocating saw according to the present invention, shown in partial cross section. 
     FIG. 2 is a perspective view of the reciprocating saw, exploded to show individual components. 
     FIG. 3 is a cross-sectional view along line  3 — 3  of FIG.  1 . 
     FIG. 4 is a cross-sectional view along line  4 — 4  of FIG.  1 . 
     FIG. 5 is a perspective view of a portion of another embodiment of the reciprocating drive assembly. 
     FIG. 6 is a side view, in cross section, of the reciprocating drive assembly portion of FIG.  5 . 
    
    
     Before one embodiment of the invention is explained in detail, it is to be understood that the invention is not limited in its application to the details of the construction and the arrangements of processes set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is understood that the phraseology and terminology used herein is for the purpose of describing the illustrated embodiment and should not be regarded as limiting the scope of the invention. 
     DETAILED DESCRIPTION 
     Referring to the drawings, FIG. 1 shows a reciprocating saw  10  according to the present invention. Some components of the reciprocating saw  10  may be similar or identical to components shown in U.S. patent application Ser. No. 08/699,448, herein incorporated by reference. 
     The reciprocating saw  10  generally includes a housing  12  that is configured to house the drive components at the front end and to fit an operator&#39;s hand at the rear end. The housing is split in two halves (FIG.  2 ), which are combined when the saw  10  is assembled. At the front end of the reciprocating saw  10  is a saw blade  18  mounted to a spindle  14  that reciprocates within the saw  10 . Specifically, the saw blade  18  is mounted within a blade clamp  16  at the front end of the spindle  14 . Such a blade clamp is shown and described in pending International Application No. PCT/US97/03633, which claims the benefit of U.S. Provisional Application Ser. No. 60/021,470, both of which are herein incorporated by reference. 
     In the configuration shown in FIG. 1, the saw blade  18  is oriented such that the serrations will face downward. Thus, the saw blade  18  is configured for downcutting. In some cases, it may be beneficial to reverse the saw blade  18  such that the teeth of the saw blade  18  face upward, thereby configuring the saw for upcutting. The spindle  14 , the spindle drive mechanism, and the spindle clamp  16  may be suitably adapted to saw in both directions. Further, the type of motion of the saw blade  18  and the spindle  14  may be varied to make the motion of the saw blade  18  more suitable to upcutting or downcutting, as described hereinafter in further detail. 
     The spindle  14  reciprocates in a generally forward and rearward direction, and defines a spindle axis  15  through the center of the spindle  14 . The saw blade  18  is reciprocated and thereby moved through a cutting stroke in one direction and a return stroke in a substantially opposite direction. A motor  20  powers the mechanism of the reciprocating saw  10  and moves the saw blade  18  through the cutting stroke and the return stroke. Power from the motor  20  passes through a number of components before being transferred to the saw blade  18 . These components thereby define a drive force path that includes those components, or those portions of components, that carry a drive force from the motor  20  through to the spindle  14  and to the saw blade  18 . 
     The motor  20  is fixedly mounted within the housing  12 . The motor  20  may be externally powered or, as shown in FIG. 1, may include a plug  22  for a battery (not shown) that provides power to the motor  20 . The motor  20  drives a motor pinion  24  through a motor shaft  26 . The motor pinion  24  engages and drives a drive gear  28 . 
     The drive gear  28  is coaxially mounted to a drive shaft  30 . The drive gear  28  and the drive shaft  30  thereby define a drive axis  31 . As shown in FIG. 2, the drive shaft  30  includes a shoulder  32  that is sized to fit the inner diameter of drive gear  28 . The drive shaft  30  is reduced in diameter at a first end  34  and a second end  36 . The first end  34  and the second end  36  are adapted to fit within a front bearing  38  and a rear bearing  39 , respectively, that are fixedly mounted by their outer races inside the housing  12 . Such bearings may be, for example, radial cartridge bearings. 
     As shown in FIGS. 1 and 2, a reciprocator body  40  fits over the drive shaft  30 . The reciprocator body  40  translates the rotary motion of the drive shaft  30  to reciprocating motion. The reciprocator body  40  interacts with the drive shaft  30  by means of a drive pin  42  within a groove  44  of drive shaft  30 . The drive pin  42  is held in a fixed position relative to the reciprocator body  40  by a pin retainer cup  46 . The drive pin  42  is freely rotatable relative to the reciprocator body  40  and the pin retainer cup  46 . 
     Two embodiments of the drive pin configuration are shown in the drawings. In the first embodiment, shown in FIGS. 1 and 2, a single drive pin  42  rides within a single groove  44 . In the second embodiment, shown in FIGS. 5 and 6, a drive pin  42 ′ and a follower pin  43 ′ ride within a groove  44 ′ and a follower groove  45 ′, respectively. The follower pin  43 ′ functions to more precisely locate the reciprocator body  40 ′ relative to the drive shaft  30 ′ and thereby prevent backlash. As shown in FIG. 6, the follower pin  43 ′ preferably has a frustoconical tip, and the follower groove  45 ′ is frustoconical in cross-sectional shape to receive the frustoconical tip. A further difference between the two illustrated embodiments is that in the first embodiment of FIGS. 1 and 2, the drive pin  42  rotates on bearings  48  separated by spacer  47 . In the second embodiment of FIGS. 5 and 6, the drive pin  42 ′ and the follower pin  43 ′ rotate on bushings  49 ′, such as sintered brass bushings, that separate the pins from the pin retainer cup  46 ′. 
     As one skilled in the art would recognize, the drive pin  42  will preferably be free to rotate relative to the pin retainer cup  46 . Thus, the end of the drive pin  42  that rides within the groove  44  is preferably slightly smaller in size than the groove  44 . The drive pin  42  will therefore roll along the sidewalls of the groove  44 . 
     The pin retainer cup  46  may comprise a separate assembly that houses the drive pin  42  and is attached to the reciprocator body  40 . Alternatively, the pin retainer cup  46  may, as shown in FIG. 2, comprise a plate that is attached at the end of the pin retainer cup to contain the drive pin  42 . Such a plate or the entire pin retainer cup  46  may be affixed to the reciprocator body  40  by means of fasteners in order to permit disassembly and repair. 
     FIGS. 1 and 2 illustrate that the reciprocator body  40  includes a pair of the reciprocator pins  37  that extend from the side of the reciprocator body  40 . As shown in the cross section of FIG. 4, the reciprocator pins  37  are reflected on both sides of the reciprocator body  40 . The reciprocator pins  37  are generally cylindrical and have flattened top and bottom sides. 
     The reciprocator pins  37  of the reciprocator body  40  engage a pivot body  50 . The pivot body  50  transfers the drive force to the spindle  14 , and thus functions as an actuating member of the spindle  14 . The pivot body  50  is pivotally mounted within the housing  12 , and pivots about pivot axis  51 . 
     In the first embodiment shown in FIGS. 1 and 2, the pivot body  50  is generally Y-shaped and includes a first end  52  that engages the spindle  14 , and a second end  54  that engages the reciprocator body  40 . As best shown in FIGS. 2 and 4, the second end  54  includes two portions that are offset from the central axis of the reciprocating saw  10  and engage the two reciprocator pins  37  on either side of reciprocator body  40 . The pivot body  50  further includes a pair of apertures  56  (FIG. 2) on either side of the pivot body  50 , the apertures being configured to receive a pivot pin  58 . The ends of pivot pin  58  are mounted within bushings  60  that are mounted within the housing  12 . 
     The first end  52  includes an open slot  53  for engaging the spindle, and the second end  54  includes an open slot  55  on each side to engage the reciprocator pins. As the pivot body  50  pivots, and as the corresponding pins that are engaged within the slots  53 ,  55  reciprocate, the distance of the corresponding pins to the pivot axis  51  of the pivot body  50  changes. Therefore, an elongated slot is desired in the illustrated embodiment. 
     The first end  52  of the pivot body  50  engages spindle  14  by means of a spindle pin  62 . The spindle pin  62  is cylindrical and engages the slot  53  in the first end  52 . As FIG. 2 more clearly shows, the spindle pin  62  passes through an aperture  64  in the spindle  14 , and the spindle pin  62  engages the walls of the aperture  64 . 
     In the second embodiment, shown in FIGS. 5 and 6, the arrangement of the interconnection between pivot body  50 ′ and spindle  14 ′ is different. The pivot body  50 ′ is generally X-shaped, having two portions on both the first end  52 ′ and the second end  54 ′. The first end  52 ′ engages the spindle pin  62 ′ on both sides of the spindle  14 ′. The first end  52 ′ of the pivot body  50 ′ is shown as having closed slots  53 ′, instead of an open slot as shown in the first embodiment. As long as the slots  53 ′ are sufficiently long to engage the spindle pin  62 ′ during the entire travel of the spindle  14 ′, either configuration will function properly. 
     In either embodiment, the spindle pin  62  may be flexibly mounted to the spindle  14 , such that a shock absorber is mounted between the spindle pin  62  and spindle  14 . FIG. 6 shows, in cross section, such an arrangement in which a shock absorber  66 ′ is made of an elastomeric, shock absorbing material, and is interconnected between the spindle pin  62 ′ and the spindle  14 ′. Because the spindle pin  62 ′ may then move relative to the spindle  14 ′, it is necessary to configure the spindle  14 ′ to permit such movement. For example, in the configuration shown in FIGS. 5 and 6, the spindle pin  62 ′ could extend through a longitudinal slot  74 ′ in the spindle  14 ′, instead of the circular aperture  64  shown in FIG.  2 . 
     As shown in the cross section of the spindle  14 ′ in FIG. 6, the spindle pin  62 ′ may be connected to a pin sleeve  68 ′ that fits in the center of the spindle  14 ′ and has a cylindrical passage for retaining the spindle pin  62 ′. The pin sleeve  68 ′ presses against the shock absorber  66 ′, and is mounted behind front shock portion  70 ′ and in front of rear shock portion  72 ′. The rear shock portion  72 ′ may be smaller such that the shock absorption is more stiff during the cutting stroke. The shock absorber  66 ′ provides greater shock absorption in the event that, for example, the blade strikes a rigid object or is pinched during the return stroke. This increases the life of the mechanism and may prevent damage to the mechanism, as well as aiding the operator comfort. 
     The spindle  14  does not, in the preferred embodiment, reciprocate only along a spindle axis  15  that is parallel to the drive axis  31 . Instead, for more effective cutting, the saw blade  18  can be moved with rocker motion as described in U.S. patent application Ser. No. 08/699,448. In short, the spindle  14  is reciprocated by moving the spindle pin  62  within a spindle track  82  having an adjustable inclination. The spindle track  82  thus provides an adjustable spindle path. 
     Referring to FIGS. 1 and 2, the angle of the spindle  14  may be selectively varied by adjustment of the position of spindle track  82 . The spindle track  82  is pivotally mounted to the housing  12  at one end and can therefore be angled up or down. Referring to FIG. 2, a fixed end  84  includes a pair of track pins  86  that pivotally engage the housing  12 . At a free end  88  of the spindle track, a pin  90  extends rearward. The pin  90  engages a slot  92  in a cam  94 . The slot  92  has a shape that varies the vertical position of the pin  90  as the cam  94  rotates. The cam  94  may rotate relative to the housing. The cam  94  may be moved using a tab  96  that protrudes through the top of the housing  12 . By adding frictional engagement points, the cam  94  motion can be made such that the user selects one of several positions of the cam  94 . Frictional engagement between the cam  94  and the housing  12  thus keeps the cam  94  in a selected position. 
     In a preferred embodiment, the position of the spindle track  82  is adjustable such that the free end  88  is either at, above or below a horizontal position (as viewed in FIG.  1 . Thus, the “rocker” motion can be tailored to the particular working conditions, such as the type of material and the blade used. Further, as previously mentioned, the reciprocating saw  10  of the present invention may be used for upcutting and downcutting. The motion of the saw blade  18  may be selected for optimal cutting in both upcutting and downcutting conditions. 
     Referring to FIGS. 1 and 2, the spindle  14  is mounted at the forward end of the reciprocating saw  10  by a spindle bushing  80 . The spindle bushing  80  has a cylindrical inner surface to engage the outer surface of the spindle  14 , and a spherical outer surface so as to be pivotally mounted within the housing  12 . In this way, the angle of the spindle  14  relative to the housing  12  may be varied. When the reciprocating saw  10  is adjusted so that the saw blade  18  is rocking up or down, the outside of the spindle bushing  80  pivots relative to the housing  12 . 
     As will be appreciated by one skilled in the art, in the illustrated embodiment the reciprocator body  40  both translates force from the drive shaft  30  to the spindle  14 , and also reciprocates in a direction largely opposed to the direction of the spindle  14 , thereby counterbalancing the reciprocating saw  10 . Thus, the reciprocator body  40  is both a driving mechanism and a counterweight at the same time, without additional mechanisms or complexity. It can be seen that a drive force path exists from the motor  20 , through motor pinion  24  and drive gear  28 , through drive shaft  30 , through reciprocator body  40 , through pivot body  50 , through spindle  14 , and finally to saw blade  18 . The portion of the reciprocator body  40  that is truly essential for operation of the saw  10  is the portion around drive shaft  30 , around groove  44 , and that contacts the pivot body  50  (i.e, at reciprocator pin  37 ). Any additional mass of the reciprocator body  40  serves to reinforce the structure and to provide a counterweight. Because the travel of the spindle  14  and the reciprocator body  40  may be determined by the geometry of the mechanism, the reciprocator body  40  may be designed to provide an inertial force that substantially balances the spindle  14  and therefore the reciprocating saw  10 . 
     More particularly, during the cutting stroke, typically when the saw blade  18  is being retracted, the spindle  14  is travelling along a substantially rearward path. Adjustment of the spindle track  82  moves the path of travel of the spindle  14  and saw blade  18  somewhat, but still the travel is still largely rearward. While the spindle  14  is retracting, the reciprocating member  40  is travelling along a path in a forward direction and parallel to the drive axis  31 . Thus, a substantial vector component of the direction of travel of the saw blade  18  and the spindle  14  will be opposed to the direction of travel of the reciprocating member  40  during the cutting stroke. If the spindle  14  is adjusted to reciprocate longitudinally along the spindle axis  15 , then the travel will be exactly opposed. During the return stroke, the path of travel of the spindle  14  and the reciprocating member will be exactly the same as the extending stroke, but the components are moving in the opposite direction. 
     An additional benefit of the invention is that the configuration of the drive mechanism of the reciprocating saw  10  permits adjustment of the length of travel of the spindle  14  and thus the saw blade  18 . This may be accomplished by varying the position of pivot axis  51 . More specifically, pivot axis  51  can be varied up or down as indicated by arrows  76  in FIG. 1, in a direction perpendicular to the drive axis  31  and the spindle axis  15 , in order to vary the travel of the spindle  14 . Different housings  12  could be created with different pivot axis  51  positions, or the pivot axis  51  position could be made selectively adjustable with a housing  12  having the pivot pin  58  and bushings  60  being movable to different positions and fastenable at a selected position. 
     While the several embodiments of the present invention has been shown and described, alternative embodiments will be apparent to those skilled in the art and are within the intended scope of the present invention. Therefore, the invention is to be limited only by the following claims: