Patent Publication Number: US-2016221092-A1

Title: Reciprocating Saw with Reinforced Offset Saw Blade Holder

Description:
REFERENCE TO RELATED APPLICATIONS 
     This is divisional application of prior U.S. patent application Ser. No. 13/724,000, filed and issued as U.S. Pat. No. 9,278,397, the disclosure of which is hereby incorporated in its entirety herein. 
    
    
     BACKGROUND OF THE DISCLOSURE 
     The present disclosure relates generally to reciprocating saw tools and more particularly, to an improved reciprocating saw with a reinforced saw blade holder that is mounted to a slotted drive shaft. 
     In the insulating foam industry, installers spray an insulating, expanding foam into selected building wall areas, such as those areas between adjacent studs of the building framing. The sprayed foam expands and sets and extends past the faces of the wall studs. This excess foam must be trimmed by the installer in order for interior and exterior sheathing and SHEETROCK® drywall or wall board to be applied to the framing. The foam is commonly trimmed by a hot wire that is pulled along the stud faces by an installer, or with a thin-bladed saw, such as a coping saw. Both of these methods are difficult to employ and both require substantial labor, reducing the potential profit for the installer. Installers now use reciprocating saws in order to trim the sprayed foam more quickly and more efficiently. 
     In order to make the process of using a reciprocating saw to remove excess foam more efficient, I developed a modification for an existing reciprocating saw that converts an ordinary reciprocating saw into one with an offset blade holder and a second, exterior handle. In this modification, I provided an offset mounting head that includes a mounting block with a hollow bore that receives therein, the free end of the saw tool drive shaft. The offset mounting head permits the installer to place the saw blade into closer contact with the faces of the framing studs to achieve a better trim of the insulating foam. 
     However, the free end of the drive shaft of the saw tool has a central slot that receives the attachment end of the saw blade, and the saw blade is secured to the shaft by means of a set screw or the like that extends through one of the drive shaft halves flanking the slot, into the drive shaft slot and into contact with an opposing surface of the saw blade. Although in my prior offset saw, the saw blade was no longer held in the drive shaft slot but mounted instead to a mounting block of the offset assembly, the drive shaft slot remained slotted as the replacement of it would make the resulting saw commercially unfeasible. The slotted drive shaft was used and the mounting block was slipped over the drive and a set screw was used to secure the mounting block to the drive shaft. The set screw extended through one of the drive shaft halves and into the slot. 
     This drive shaft slot creates a natural area in the drive shaft for stress risers to occur, i.e., areas of concentrated stress and this may result in one or both of the drive shaft halves deflecting under impact loading, or worse, breaking Impact forces that occur when the end of the saw blade contacts a stud or sheathing during operation are transferred through the saw blade directly to the drive shaft to cause this stress. A need therefore exists for an offset saw blade mounting assembly used with a reciprocating saw in which the manner of mounting the saw blade is stronger and more resistant to stresses which may induce drive shaft failures. 
     The present disclosure is therefore directed to an improved offset saw blade mounting assembly for a reciprocating saw with a means for reinforcing the slotted drive shaft. 
     SUMMARY OF THE PRESENT DISCLOSURE 
     Accordingly, there is provided a power tool in the form of a reciprocating saw that is suitable for use with foam installation with a means for reinforcing the drive shaft. 
     In accordance with an embodiment as described in the following disclosure, an offset mounting block is provided for a reciprocating saw tool that utilizes a cylindrical, slotted drive shaft. The offset mounting block has a generally L-shaped configuration with distinct mounting block and a blade support portions that are spaced apart from each other. In the L-shaped offset mounting block of the preferred embodiment of the disclosure, a cylindrical bore is provided in the mounting block portion. This bore extends axially through the mounting block portion so that it may be slipped over a free end of the drive shaft. A pair of retaining screws clamp the mounting block to the drive shaft. 
     A guide channel assembly is also provided that guides the offset mounting block in its reciprocating movement and also is attached to the saw tool. The guide channel assembly includes a baseplate attached to the forward end of the saw body and extending out therefrom at an angle to the drive shaft. Two guide arms extend from the guide baseplate and cooperatively define a guide channel therebetween. The drive shaft and mounting block are disposed in this guide channel and the channel at least partially guides the mounting block in its reciprocating movement during operation of the saw. A handle member is attached to the baseplate on the side opposite the guide arms and extends out from the saw body at a right angle thereof so that the operator may grasp the saw at both its rear, conventional handle and at the forward end of the saw. The handle member is attached to the baseplate by way of a U-bolt, which also partially secures the guide channel assembly to the front barrel portion of the reciprocating saw tool. The baseplate is also preferably secured to the front barrel portion in a manner to prevent rotation, or other movement, of it about the front barrel portion. 
     In order to eliminate the possibility of one (or both) of the drive shaft halves bending or collapsing on the other in response to unexpected impact loading, my new development includes a shim member, or filler, that is provided to fill the drive shaft slot. Both of the drive shaft halves act like cantilevered beams when the slot is empty, and the drive shaft halves may bend or deflect a distance at least equal to the width of the slot Impact forces on the saw blade may cause this deflection or bending. Inserting the shim member into the slot prevents the drive shaft halves from deflecting in a manner that could cause damage to the drive shaft. In the preferred embodiment of the present disclosure, the shim member is formed as a separate piece that is dimensioned to completely fill the slot, and this piece is inserted into the drive shaft slot. One or more set screws extend through part of the mounting block to securely clamp it to the drive shaft. 
     In another embodiment of the present disclosure, the mounting block includes a positioning slot formed in the mounting block, and which is aligned with the drive shaft slot so that an assembler may first place the mounting block onto the drive shaft, align the mounting block guide slot with the drive shaft slot and subsequently insert the shim member into the drive shaft slot by way of the mounting block guide slot. The guide slot assists in positioning the shim member in place within the drive shaft. In this regard, the shim member may be larger in dimensions than the drive shaft slot. 
     In yet another embodiment, the shim member may be formed as part of a separate insert, having a cylindrical, tubular body portion with a larger outer rim, or hub portion, and a shim portion integrally formed therewith and extending between walls of the tubular body portion. The mounting block bore is dimensioned so as to snugly receive the insert therein, and accordingly, a leading edge of the bore may be counterbored to accommodate the outer rim portion so that the insert fits flush with a face of the mounting block. In this manner, the drive shaft may be first roughly positioned in the mounting block bore and the insert then inserted into the bore onto the drive shaft. Thus, the insert fills the annular space between the inner wall of the bore and the exterior surface of the drive shaft. 
     Lastly, in yet another embodiment of the present disclosure, the shim member may also be formed as an integral part of the mounting block by a suitable method such as die-casting or electrodischarge machining (EDM) or the like so that when the mounting block is installed on the drive shaft, the shim member simultaneously is inserted into the drive shaft slot. Additionally, a finger guard may be provided for the entire offset mounting assembly, and supported by the guide channel guide arms in order to define a shield that at least partially encloses the opening that exists between the guide arms and the body of the saw. The shim member and the mounting block may be attached to an existing saw tool or may be utilized in the context of a kit of parts for converting an existing reciprocating saw into one with an offset blade holder. 
     These and other objects, features and advantages of the present disclosure will be clearly understood through a consideration of the following detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The organization and manner of the structure and operation of the disclosure, together with further objects and advantages thereof, may best be understood by reference to the following detailed description, taken in connection with the accompanying Figures, wherein like reference numerals identify like elements, and in which: 
         FIG. 1  is a perspective view of a prior art, right-handed, reciprocating saw tool with a offset saw blade mounting assembly; 
         FIG. 2  is a slightly angled elevational view of a left-handed, reciprocating saw tool incorporating a reinforced saw blade holder constructed in accordance with the principles of the present disclosure; 
         FIG. 2A  is an exploded view of the offset saw blade mounting assembly of the reciprocating saw tool of  FIG. 2 ; 
         FIG. 3  is a slightly angled top view of the known reciprocating saw tool of  FIG. 1 ; 
         FIG. 4  is a perspective view of the reciprocating saw tool of  FIG. 2 , taken from the front end thereof and with the saw tool bottom side up; 
         FIG. 5  is an enlarged detail view of the front end of the barrel portion of the reciprocating saw tool of  FIG. 2 , with the offset saw blade mounting assembly removed for clarity, and illustrating a first embodiment of a shim member partially in place within the drive shaft slot; 
         FIG. 6  is a view of the front end of a the reciprocating saw tool barrel portion and drive shaft and an shim member of the present disclosure intended for use therewith; 
         FIG. 7  is a perspective view of the guide channel member and a finger guard of the present disclosure attached thereto; 
         FIG. 7A  is a rear elevational view of the offset mounting blade assembly in place upon the power saw; 
         FIG. 8  is a perspective view of an alternate embodiment of an offset saw blade mounting block in accordance with the principles of the present disclosure utilizing a shim member inserted into the saw drive shaft slot and positioned therein by way of a guide slot in the mounting block; 
         FIG. 9  is a perspective view of a third embodiment of an offset saw blade mounting block constructed in accordance with the principles of the present invention in which the shim member is incorporated into a cylindrical insert that is supported within a bore of the blade holder; 
         FIG. 10  is a sectional view of the saw blade mounting block of  FIG. 9 , taken along lines  10 - 10  thereof; and, 
         FIG. 11  is a perspective view of a fourth embodiment of an offset saw blade mounting block constructed in accordance with the principles of the present invention which utilizes a shim member formed integrally as a single piece with the mounting block and extending within the bore thereof 
     
    
    
     DETAILED DESCRIPTION OF THE DISCLOSURE 
     While the present disclosure may be susceptible to embodiment in different forms, there is shown in the Figures, and will be described herein in detail, specific embodiments, with the understanding that the disclosure is to be considered an exemplification of the principles of the present disclosure, and is not intended to limit the present disclosure to that as illustrated. 
     In the illustrated embodiments, directional representations—i.e., up, down, left, right, front, rear and the like, used for explaining the structure and movement of the various elements of the present disclosure, are relative. These representations are appropriate when the elements are in the position shown in the Figures. If the description of the position of the elements changes, however, it is assumed that these representations are to be changed accordingly. 
     Turning now to  FIG. 1 , a power tool  20  is illustrated in the form of a reciprocating saw  22 . The saw  22  has an elongated body  24  with a rear handle portion  26  that includes an operating switch  27  and a front barrel portion  28 . A drive shaft  30  is disposed in the front barrel portion  28  and supported therein for reciprocating motion along a first axis L 1  that preferably is at the center of the drive shaft  30  so that a saw blade  29  attached to the drive shaft will operate in a back and forth cutting action. The drive shaft  30  ( FIG. 5 ) is cylindrical in nature and has a free end  31  configured with a central slot  32  of a given length that is dimensioned to receive the butt end (not shown) of an elongated saw blade  29 . As illustrated in  FIG. 5 , the drive shaft free end  31  extends past the front end  34  of the tool barrel portion  28  and is supported therein for movement by a series of bearings  36 . The drive shaft slot  32  divides the free end  31  of the drive shaft  30  into two halves, or shaft arms  38   a,b  and one of these two shaft arms  38   a  includes an opening  33  formed therein that is dimensioned to receive a retainer  35  that retains the saw blade  29  on a conventional saw tool. The retainer  35  typically takes the form of a fastener, such as a set screw. 
     In order to move the axis of the saw blade  29  to a second axis L 2  that is spaced apart, or offset from, the first axis L 1 , an offset mounting assembly  40  is provided, which includes, among other elements, a mounting block  40 . The mounting block  40  can be seen to have an L-shaped configuration defining two distinct portions, shown as a mounting portion  42  and a saw blade support portion  44 , which, as illustrated in the Figures, may be integrally formed together. The saw blade support portion  44  extends alongside the mounting portion  42  and serves to engage, such as by screws or the like, the mounting end  45  of a saw blade  29  along the second axis L 2 . The second axis L 2  is spaced a predetermined distance D from the first axis L 1 . The mounting block  40  has a bore  46  formed in it that runs along the first axis L 1  and which is dimensioned to receive the free end  31  of the drive shaft  30  therein. The mounting block  40  further includes a fitting slot  48  in alignment with the bore  46  and first axis L 1 , and which extends through the mounting block  40  to communicate with the bore  46 . In order to provide a secure means of fastening the mounting block  40  to the drive shaft  30 , a pair of holes  47  that accommodate clamping screws  47   a  are provided. These clamping screws  47   a  are tightened to an extent where the fitting slot  48  compresses and the mounting block thereby exerts a clamping force on the outside of the drive shaft  30 . 
     Due to the offset nature of the mounting block  40 , a guide assembly  50  is provided in order to guide the mounting block  40  in its reciprocating movement. This guide assembly  50  includes a baseplate  52  that extends in a plane parallel to the first axis L 1  and is disposed proximate to the front end  34  of the saw front barrel portion  28 . The guide baseplate  52  is secured to the saw body  24  by means of a U-bolt  54  that is joined at one end thereof to a cylindrical handle  56  and to fastening nuts  58  at the other end thereof The U-bolt  54  is sized to extend around and contact the rubber boot that envelops the front end  34  of the saw front barrel portion  28  so as to secure the guide assembly  50  in place upon the saw tool. A pair of guide arms, or wings,  60  are mounted to the guide baseplate  52  such as by screws or bolts  62  and these guide arms  60  extend outwardly from the guide baseplate  52  for a length past the mounting area of the mounting block blade support portion  44  as well as the mounting end  45  of the saw blade  29 . The guide arms  60  are separated by an intervening space  64  that forms a channel in which the mounting block  40  and drive shaft  30  move back and forth in their movement. The guide arms  60  have a predetermined width so as to close off the normally open area between the front end of the saw tool and the rear edge of the mounting block  40 . The above structure and that illustrated in  FIG. 1  defines my prior reciprocating saw development. 
     In order to prevent the guide assembly  50  from rotating or otherwise moving about the front barrel portion  28  of the saw  22 , during operation of the saw and the operator exerting a force on the handle  54 , a mounting screw  94  is provided that extends through an opening  95  in the baseplate  52  and preferably into a tapped hole  96  in the front barrel portion  28  of the saw body  24 . ( FIG. 7 .) In order to reinforce the mounting screw  94 , a hollow collar, or sleeve  97 , extends over the shaft  94   a  of the mounting screw and extends between and in contact with an interior surface of the baseplate  52  and the exterior surface of the front barrel portion  28 . The sleeve increases the resistance of the mounting screw  94  to bending and other detrimental forces. Furthermore, in order to partially close off access to the moving drive shaft  30  and reduce the risk of a user getting his fingers, clothing or the like caught by the drive shaft  30  and front end of the tool during operation, I have now provided a guard plate  66 . ( FIGS. 4 &amp; 8 .) The guard plate  66  has an overall U-shaped configuration with a backbone portion  67  interconnecting two leg portions  68 ,  69 . The guard plate  66  may be secured to the guide assembly by screws  70  or the like such that the body portion  67  is disposed to the outside of the guide baseplate to provide necessary closure of this open area. 
     In use of my prior saw tools, it was discovered that even though the saw blade mounting end  45  was removed from the drive shaft slot  32 , the drive shaft  30  was still subjected to possible stress concentrations and during repeated cycles of cutting, and the drive shaft arms/halves  30   a,    30   b  could deflect, or crack, thereby weakening them. Once cracked, the mounting block lost complete reliable contact with the drive shaft  30  and the possibility of it coming loose from the drive shaft increased. In order to solve this problem, my new development utilizes a shim member  80 , shown in  FIGS. 5 &amp; 6  as having a plate-shape, that is at least partially inserted into the drive shaft slot  32 . Preferably, the shim member  80  has a thickness equivalent to the thickness of the drive shaft slot  32  and has a length equivalent to the slot length so that it completely fills the drive shaft slot  32 . In use, the shim member  80  is inserted into the drive shaft slot  32  and the mounting block  40  is then applied to the drive shaft free end  31 . The shim member  80  fills the slot  32 , reinforces the drive shaft  30  and prevents either of the two shaft halves  38   a,    38   b  from bending or otherwise deflecting during operation, thereby reducing the likelihood of imposition of increased stresses. In this embodiment, the shim member  80  is preferably inserted into the drive shaft slot  32  before applying the mounting block  40  onto the drive shaft  30 . 
       FIG. 8  illustrates another embodiment of an improved power tool utilizing a shim member of the present invention. In this embodiment, the mounting block  40  is provided with a positioning slot  81  that is formed in the body of the mounting block and in communication with the mounting block bore  46 . The positioning slot  81  is larger than the bore  46  and it permits the shim member  80  to be more easily inserted into the drive shaft slot  32  after the mounting block  40  has been attached to the drive shaft  30 . In this embodiment, it is desired that the filling slot  48  be positioned off center of the bore  46 , i.e. off of the first axis L 1 . In instances where the power saw has the drive shaft oriented in a horizontal direction, the positioning slot  81  will also be arranged horizontally. 
       FIGS. 9 and 10  illustrate a third embodiment of the present disclosure in which the mounting block  40  has been modified with a counterbore  82  to receive an integrated, cylindrical insert  84  in the form of a tubular member  85  with a continuous sidewall  86  and a shim portion  86   a  formed integrally therewith and extending axially through the insert  84 . The insert  84  may have a larger, outer shoulder or rim portion  87  that sits in the counterbore  82  and against an inner shoulder  88  thereof The exposed, or front end,  90  of the insert preferably lies flush against the front face  43  of the mounting block mounting portion  42 . 
     Lastly,  FIG. 11  illustrates yet another embodiment of the present disclosure where the shim member  92  is integrally formed with the mounting block  40  so that it divides the bore  46  into two distinct parts  46   a,    46   b.  This is easily done for instances where the drive shaft slot  32  is oriented horizontally, but in vertical instance the bore filling slot  48  is made off center of the bore  46  so that the shim member  92  properly extends into the bore  46  without weakening the support for it. This type of mounting block may be formed by die-casting or EDM. 
     While preferred embodiments have been shown and described, it is envisioned that those skilled in the art may devise various modifications without departing from the spirit and scope of the foregoing Description and the appended Claims.