Abstract:
A drill powered reciprocating saw including a safety gear assembly which disengages the saw&#39;s drive mechanism should the operator lose his or her grip on the saw housing. The gear assembly includes a motor drive shaft that is connected to an electric drill and which drives a jackshaft by means of a pair of interlocking gears. At rest, the drive shaft is biased by a spring to a position where the gears are not in contact with each other. When the operator pulls the saw housing toward the drill, the spring is compressed and the gears are engaged, thus allowing the saw to operate. Should the operator lose his or her grip on the housing, the spring biases the drive shaft back to its original position, thereby disengaging the gears.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an attachment for power tools and, in particular, to a device for actuating a reciprocating saw from a hand drill. 
     2. Description of the Related Art 
     Reciprocating saws are frequently used by contractors and the like for various cutting applications. Unfortunately, such saws are typically heavy and inconvenient to operate. In order to reduce the inconvenience associated with these saws, a variety of attachments have been developed for converting a rotary power tool, such as a drill, into a reciprocating saw. However, many of these attachments would require a power tool having a front portion specially shaped for receiving the attachment. Moreover, most reciprocating saw attachments are connected to the power tool by a rotating spindle. The rotation of the spindle makes it necessary for the operator to grip the saw attachment during operation. Should the operator loose his or her grip, the attachment will rotate in an unrestrained fashion, thereby potentially causing an injury. 
     Therefore, there is a need for a drill powered reciprocating saw having an automatic safety mechanism that will disengage the saw&#39;s drive mechanism and prevent the saw from rotating should the operator loose his or her grip on the saw housing, or should the drill be activated without the saw housing being gripped by the operator. 
     U.S. Pat. No. 1,793,053 discloses a saw which attaches to a potable hand tool, such as a drill. The saw uses a gear and belt drive mechanism to convert the rotary motion of the drill into reciprocating motion. 
     U.S. Pat. No. 2,240,755 discloses a power tool using a gearing mechanism to convert the rotary motion of a drill to a reciprocating motion. 
     U.S. Pat. No. 2,621,685 discloses a hand carried powered tool which uses a gear and flywheel mechanism to convert the rotary motion of a motor into reciprocating motion for a saw blade. The tool includes a work-rest for providing support against a work surface. 
     U.S. Pat. No. 2,631,619 discloses a reciprocating saw tool attachment which converts the rotary motion of a drill into a reciprocating motion for driving a saw blade. The rotating parts are positioned at a maximum distance from the reciprocating spindle to give the device the maximum degree of eccentricity with respect to the axis. This arrangement minimizes the force necessary to hold the saw and prevents rotation of the housing should the saw be released from the operator&#39;s hands. 
     U.S. Pat. No. 2,793,661 discloses a power driven reciprocating saw unit for converting a power drill into a saw. The device converts the rotary motion of the drive shaft into a reciprocating motion by means of a pivoting cylinder that is attached to the-drive shaft. 
     U.S. Pat. No. 3,260,289 discloses a saber saw attachment for a power tool, such as a hand drill. A rotating shaft is attached to a piston at one end, and to the drill drive shaft at the other end. The shaft has a circumferential groove for receiving a ball bearing. As the shaft is rotated, the groove and ball bearing cause the shaft to reciprocated back and forth, thereby driving the piston. 
     U.S. Pat. No. 3,585,719 discloses a power tool for converting the motion of a rotary power source, such as a drill, into a reciprocating motion. The device can hold a variety of different cutting blades including hacksaw blades and edge trimmers. A rotating power shaft has inclined wobble plate that is connected to a reciprocating spindle. The entire tool is rotatable 360 degrees in relation to the rotary power source. 
     U.S. Pat. No. 3,876,015 discloses a power tool attachment that converts rotary to reciprocating motion for portable power tools. The attachment is secured to the power tool by means of an adaptor lock plate that is attached to the front of the power tool. 
     U.S. Pat. No. 4,841,643 shows a drill powered saber saw comprising a stationary support for supporting a power drill, and a flexible power transmission cable for connecting the saber saw attachment to the drill. 
     U.S. Pat. No. 4,494,463 discloses a sawing device attachable to regular electric drill comprising a spiral gear drive mechanism which converts the rotary motion of the drill into reciprocating motion. 
     U.S. Pat. No. 5,050,307 discloses a wobble plate drive that is mounted on a rotating shaft and has a drive arm engaging a reciprocating spindle so as to restrain the spindle from rotation. 
     U.S. Pat. No. 5,566,458 discloses a clutch mechanism for reciprocating saws comprising a spring biased gear which provides slippage between the motor and the drive shaft if there is binding of the reciprocating spindle. 
     U.S. Pat. No. 5,595,250 discloses a drill accessory for converting a power drill into a reciprocating saw having a blade which can be adjusted for several different cutting depths. 
     U.S. Pat. No. 5,607,265 discloses a reciprocating attachment for hand drills. The reciprocating attachment uses a grooved shaft for changing the rotation of the shaft of the drill to a reciprocating motion necessary to power a saw blade. 
     None of the above inventions and patents, taken either singularly or in combination, is seen to describe the instant invention as claimed. Thus a drill powered saw solving the aforementioned problems is desired. 
     SUMMARY OF THE INVENTION 
     In view of the foregoing limitations of the drill powered reciprocating saws described in the prior art, the present invention provides an improved reciprocating saw having an automatic safety mechanism that will disengage the saw&#39;s drive mechanism and prevent the saw from rotating should the operator loose his or her grip on the saw housing, or should the drill be activated without the saw housing being gripped by the operator. 
     The invention comprises a reciprocating saw having a housing that is ergonomically configured to be gripped by a person&#39;s hand. A handle is rotatably attached to the housing and may be rotated around the housing axis by loosening a clamp. A motor drive shaft for connecting to a power drill is mounted in the housing. The drive shaft is connected to a jackshaft by a safety gear assembly. One end of the drive shaft is attached to the housing by a spring and slide bearing which biases the drive shaft to a position where the gear assembly is no longer engaged, and therefore, no power is imparted to the jackshaft. The gear assembly is engaged by pulling the housing toward the drill along the axis of the drive shaft. When the gear assembly is engaged, the jackshaft drives a wobble plate which converts the rotational motion to reciprocal motion. The wobble plate is attached by a drive arm to a tubular spindle which drives a saw blade. 
     Accordingly, it is a principal object of the invention to provide a reciprocating saw that attaches to a power drill and converts the rotary motion of the drill into reciprocal motion. 
     It is another object of the invention to provide a drill powered reciprocating saw having a safety gear assembly which prevents the saw from rotating should the operator loose his or her grip on the saw housing. 
     It is a further object of the invention to provide a drill powered reciprocating saw a having a vibration insulating system which isolates the drive shaft from vibration caused by the saw&#39;s reciprocating action. 
     Still another object of the invention is to provide a drill powered reciprocating saw having an ergonomically shaped housing to provide a comfortable grip for the hand. 
     It is an object of the invention to provide improved elements and arrangements thereof for the purposes described which is inexpensive, dependable and fully effective in accomplishing its intended purposes. 
     These and other objects of the present invention will become readily apparent upon further review of the following specification and drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevational view, in section, of a drill powered reciprocating saw of the present invention and showing the safety gear assembly in a disengaged position. 
     FIG. 2 is a side elevational view, in section, of the reciprocating saw showing the safety gear assembly in an engaged position. 
     FIG. 3 is a sectional view taken along the line  3 — 3  of FIG. 1 showing the wobble drive assembly. 
     FIG. 4 is a side elevational view of the reciprocating saw. 
     FIG. 5 is a top view of the reciprocating saw. 
     FIGS. 6 a  and  6   b  are side elevation views of the reciprocating saw. 
     FIGS. 7 a  and  7   b  is a side elevation view of the reciprocating saw in accordance with a second alternative embodiment. 
     FIG. 8 shows an embodiment where the drive arm is connected to the motor drive shaft via a wobble plate. 
     FIGS. 9 and 10 illustrate safety assemblies according to alternative embodiments. 
     FIGS. 11 and 12 illustrate safety assemblies according to additional alternative embodiments. 
    
    
     Similar reference characters denote corresponding features consistently throughout the attached drawings. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Shown in the various figures is a drill powered reciprocating saw  100  of the present invention. As seen in FIGS. 4-7, the saw  100  includes an ergonomically configured housing  110  which provides the operator with a secure grip and facilitates operation of the saw, as will be discussed below. 
     As shown in FIG. 6 a,  for example, the handle  115  is adapted to rotate about the housing&#39;s longitudinal axis, independently of the housing  110 . This independent rotation may be achieved by placing (or forming) a circular track  116  around the housing  110  and mounting the handle  115  within the track, to thereby enable the handle  115  to rotate about the handle  110  in the track. The handle  115  preferably has a complementary circular assembly  119  for fitting into the circular track.  116 , or the track  118  of FIG. 7 a,  for extra strength. As shown in FIG. 6 b,  the handle  115  can be tightened (screwed) into the circular assembly  119  to reduce the circumference of the circular assembly  119  and prevent rotation of the handle  115  relative to the circular assembly  119 . In an alternative embodiment as shown in FIGS. 7 a  and  7   b,  the handle  115  can be rotated about the housing&#39;s longitudinal axis, independently of the housing  110 , and locked to the housing  110  at any of a plurality of different rotational positions using a conventional locking means, such as a pin  123  inserted into aperture  118 . 
     In yet another alternative embodiment, the handle  115  is fixed to the housing  110 , and the housing  110  and the handle  115  can only rotate together 360 degrees around the housing&#39;s longitudinal axis (which is the axis of the motor drive shaft  120 ). 
     As seen in FIG.  1  and FIG. 2, a motor drive shaft  120 , having a first end  121 , a second end  122 , and a shaft axis extending there between. The first end  121  is preferably attached to an electric drill (not shown), and the motor drive shaft  120  is mounted in the housing  110 . The drive shaft  120  drives a jackshaft  155  which s mounted in the housing  110  preferably parallel to the drive shaft  120 . The drive shaft  120  and the jackshaft  155  are connected by a safety gear assembly  300 . The safety gear assembly  300  includes a motor driveshaft gear  200  which is mounted on the drive shaft  120 , and jackshaft gear  210  that is mounted on the jackshaft  155 . The safety gear assembly may be a step-up system wherein said drive shaft gear  200  has a larger diameter than said jackshaft gear  210 . 
     In the presently preferred embodiment, both the driveshaft gear  200  and the jackshaft gear  210  comprise helical gears. As presently embodied, the helical gears  200 ,  210  have standard 45 degree off-axis gear teeth. The implementation of both the driveshaft gear  200  and the jackshaft gear  210  as helical gears provides an optimal engagement of the driveshaft gear  200  and the jackshaft gear  210  as long as virtually any pressure is applied to the handle  110 . Without the configuration of the driveshaft gear  200  and the jackshaft gear  210  as helical gears, the driveshaft gear  200  and the jackshaft gear  210  may be more likely to become disengaged as various pulling pushing and pressures are applied by a user to the handle  110  during cutting. The formation of the driveshaft gear  200  and the jackshaft gear  210  as helical gears preferably maintains a continuous engagement of the driveshaft gear  200  and the jackshaft gear  210  during cutting and/or as long as any pressure is the handle  110 . 
     A spring guide sleeve  230  is mounted in the housing  110  opposite the electric drill, and supports the second end  122  of the drive shaft  120  in a slide bearing  310 . A spring  220  is mounted inside the spring guide sleeve  230 . A metal stop  320  is mounted onto the bearing  310  and prevents the end  122  of drive shaft  120  from contacting a rubber bumper  240  mounted inside the housing  110 . 
     As seen in FIG. 1, the spring  220  biases the drive shaft  120  in a direction along the shaft axis so that the drive shaft gear  200  and the jackshaft gear  210  are disengaged from each other. In order to engage the safety gear assembly  300  as shown in FIG. 2, the operator must pull the housing  110  toward the drill, thereby compressing the spring  220  and moving the safety gear assembly  300  into an engaged position. When the safety gear assembly  300  is engaged, the metal stop  320  is pressed against the rubber bumper  240 , thereby dampening the vibrations caused by the reciprocating spindle  125 . Should the operator lose his or her grip on the housing while the saw  100  is not under a load, the spring  220  will cause the gear assembly  300  to disengage. 
     As seen in FIG.  1  and FIG. 2, the saw  100  includes a wobble drive assembly  160  for converting the rotary motion of the jackshaft  155  into reciprocating motion for driving a saw blade  145 , which is held by a clamp attached to the end of the reciprocating spindle  125 . The wobble drive assembly  160  includes a wobble plate  162  that is mounted on the jackshaft  155  by an input bearing  163 . As best seen in FIG. 3, the wobble plate  162  is connected to a drive arm support  170 , which has an opening  175  through which passes the drive shaft  120 . This construction allows the drive shaft  120  to be anchored at its second end  122 , while freely moving relative to the housing  110 . A drive arm  165  is attached to the drive arm support  170  for driving a reciprocating tubular spindle  125 . 
     As seen in FIG.  1  and FIG. 2, the spindle  125  is mounted in a spindle bearing  135 . The spindle  125  has a longitudinal spindle slot  130  positioned on the side of the spindle closer to the drive shaft  120 . The spindle bearing  135  has an axial slot  140  which is aligned with the spindle slot  130 . The drive arm  165  projects through both the spindle slot  130  and the spindle bearing slot  140  and into the spindle  125 , where the drive arm  165  is secured by a wrist pin  166 . 
     FIG. 8 shows an embodiment where the drive arm  165  is connected to the motor drive shaft  120  via a wobble plate  162 . FIGS. 9 and 10 illustrate safety assemblies according to alternative embodiments wherein solenoids  190  are used to move movable members  191  in proximal and distal directions to change the size of the opening  175 . 
     The solenoid-driven safety assemblies of FIGS. 9 and 10, and of FIGS. 11 and 12, require a power source (preferably a battery, shown in the figures as a “power” block). The power blocks are connected to triggers (shown in finger notch adjacent to “power” block) and are adapted to drive the solenoids to engage the reciprocating spindles  125  when the triggers are pressed by a finger of a user. The solenoid-driven safety assemblies may be used with or without the mechanical gear-driven safety assembly  220 ,  210 . Additionally, the trigger may be placed on other places on the housing  110 , such as on the handle  115 . Alternatively, rotation of the handle  115  may operate as a trigger, or movement of the housing  110  may be configured to provide a trigger effect, with or without the safety gears  200 ,  210 . In addition to the rotation of the handle  115 , or the movement of the housing in a proximal or distal direction (relative to the motor drive shaft, for example) for providing a drive-disengagement safety assembly, either of these movements may be used in alternative embodiments for providing the electrical power to a power-driven tool. Other means are also possible for providing a drive-disengagement safety assembly. The solenoid  190  moves the movable member  191  in the distal direction to decrease the size of the opening  175  so that the drive arm  165  can drive the reciprocating spindle  125 , and moves the movable member  191  in the proximal direction to increase the size of the opening  175  so that the drive arm  165  moves freely within the opening  175  without driving the reciprocating spindle  125 . 
     FIGS. 11 and 12 illustrate safety assemblies according to additional alternative embodiments wherein solenoids  193  are used to move movable members  195  in extended and retracted directions to change the lengths of the drive arms  165 . The solenoid  193  moves the movable member  195  in the extended direction to increase the length of the drive arm  165  and move the drive arm  165  into the opening  175 , so that the drive arm  165  can drive the reciprocating spindle  125 ; and moves the movable member  195  in the retracted direction to decrease the length of the drive arm  165  so that the drive arm  165  moves freely outside of the opening  175  without driving the reciprocating spindle  125 . 
     It is to be understood that the present invention is not limited to the embodiment described above, but encompasses any and all embodiments within the scope of the following claims.