Abstract:
A power tool having an elongated housing with a nose portion, an output shaft to which a cutting blade that oscillates through a small angle is attached, the attachment comprising, an accessory interface removably mounted to the nose portion of the housing and a depth guide attachment rotatably mounted to the accessory interface, the depth guide attachment further comprising a relatively thin body portion having a generally circular first opening with a center axis generally parallel to the output shaft, the body portion fitting on the accessory interface and being rotatable thereon and having a second circular opening transverse to the first opening center axis, a depth guide member adjustably mounted on the body portion and having an offset outer end portion, and a locking member configured to secure the depth guide member in a desired position.

Description:
BACKGROUND OF THE INVENTION 
     The present invention is generally related to portable handheld power tools, and more particularly to accessory attachments for such tools. 
     Professional artisans, hobbyists and do-it-yourselfers have a relatively new type of power tool for performing cutting, grinding, sanding, scraping and grout removal tasks that are necessary for various repair, remodeling, or restoration projects. The power tool a relatively small handheld tool with an output shaft that moves from side to side through a small arc of about 2 to 3 degrees in an oscillating manner at a high frequency of up to 20,000 or more oscillations per minute. Various tool cutting and scraping blades and sanding attachments can be mounted on the tool. The high frequency side-to-side action optimizes control and provides safe operation, high precision and produces minimal dust. Such a tool is marketed as the Dremel® Multi-Max™ oscillating tool. 
     SUMMARY OF THE INVENTION 
     Embodiments of the present invention comprise an accessory attachment system for a power tool having an elongated housing with a nose portion, an output shaft to which a cutting blade that oscillates through a small angle is attached, the orientation of the oscillating blade being generally perpendicular to the output shaft, the attachment comprising, an accessory interface removably mounted to the nose portion of the housing and having a central opening through which the output shaft extends, and a depth guide attachment removably mounted to the accessory interface, and being adjustably rotatable about an axis generally concentric with the output shaft, the depth guide attachment further comprising a relatively thin body portion having a generally circular first opening with a center axis generally parallel to the output shaft, the body portion being configured and sized so that the circular opening fits on the accessory interface and is rotatable thereon and having a second circular opening transverse to the first opening center axis, a depth guide member having an elongated cylindrical mounting portion, a transition portion and an outer end portion, the outer end portion being offset relative to the mounting portion so that the end portion can be adjusted relative to the oscillating blade, and a locking member configured to secure the depth guide member in a desired position. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front left perspective view of a hand held power tool of the type which has an oscillating output shaft with an attached cutting blade, and which includes a preferred embodiment of the accessory attachment system of the present invention; 
         FIG. 2  is a front left perspective view of an accessory interface portion of the accessory attachment system mounted to the power tool shown in  FIG. 1  and also including an oscillating saw blade mounted to the tool; 
         FIG. 3  is a bottom left perspective view of the accessory interface mounted to the power tool shown in  FIG. 1  and also including an oscillating saw blade mounted to the tool; 
         FIG. 4  is a top view of the power tool with the accessory attachment system shown in  FIG. 1 ; 
         FIG. 5  is a left plan view of the power tool with the accessory attachment system shown in  FIG. 1 ; 
         FIG. 6  is a front plan view of the power tool with the accessory attachment system shown in  FIG. 1 ; 
         FIG. 7  is a front left perspective view similar to  FIG. 1 , but illustrating the saw blade as well as a depth guide rotated approximately 90° relative to an accessory interface and housing of the power tool; 
         FIG. 8  is a top view of a portion of the depth guide showing a locking mechanism for locking the body of the depth guide to the accessory interface as well as locking the depth guide member in a desired position; and 
         FIG. 9  is a side plan view of a portion of the power tool and accessory interface. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the present invention are directed to an accessory attachment system for use with hand held power tools of the type which have an output shaft that moves in an oscillating manner through a small arc of approximately 2-3° at a high frequency that can extend from less than 10000 oscillations per minute to more than 20000 oscillations per minute. Such tools are marketed by Robert Bosch LLC under the Dremel® brand as the Multi-Max™ oscillating tool and such a tool is shown in the drawings of the present invention. It should be understood that the accessory attachment system, while particularly designed and configured for use with this type of tool, can be configured for use with other types of power tools, if desired. 
     Turning now to the drawings, and particularly  FIG. 1 , an oscillating power tool, indicated generally at  10  in  FIGS. 1 and 3 , has a generally elongated housing  12  with a longitudinal axis. The tool is configured to be held in one hand of a user and has an on/off operating switch  14  for controlling the operation of a motor located in the housing. A separate speed control switch may be provided for varying the oscillating frequency of the output shaft  16  which is shown in  FIG. 3 , among other views. The power tool  10  has a nose portion, indicated generally at  18 , which extends generally at right angles to the longitudinal axis of the housing  12 . A mounting interface  20  is secured to the output shaft  16 , which interface  20  includes a number of spaced apart pins  22  configured in a circular pattern to accept and hold a mounting portion  24  of a saw blade, indicated generally at  26 . The mounting portion  24  has a number of apertures configured to engage the pins  22  at various angular orientations as desired. As shown in  FIGS. 1-6 , the blade is oriented to extend in the direction of the longitudinal axis of the housing  12 , whereas  FIG. 7  shows the blade  24  rotated approximately 90° relative to the longitudinal axis of the housing  12 . The mounting portion  24  is secured to the mounting interface  20  by a cap nut  28  that is shown to have a hexagonal recess  30  which can be tightened by a user to firmly hold the blade in place using a suitable Allen wrench or the like. 
     A preferred embodiment of the complete accessory attachment system is indicated generally at  40  in  FIGS. 1 ,  4 - 8  and includes an accessory interface, indicated generally at  42  as well as a depth guide attachment, indicated generally at  44 . 
     The accessory interface  42  is shown in detail in  FIGS. 2 ,  3  and  9  and it is shown to have a generally cylindrical relatively thin walled inner cylindrical portion  46  which fits around the outer cylindrical surface  48  of the nose portion  18  of the tool. The inner end portion  46  of the accessory interface  42  has a number of transverse slits  50  which extend from an inner end surface  52  outwardly to an outer cylindrical portion  54  which has an end flange portion  56  which defines an opening  58  through which the output shaft  16  and mounting interface  20  extend. 
     The outer end portion  54  has an annular groove  60  that extends substantially around the entire circumference of the outer end portion  54  and interacts with the depth guide attachment  44  enabling the depth guide attachment to be rotationally positioned on the accessory interface  42  to best cooperate with the angular position of the blade  26 . The rear surface of the outer end portion  54  has a reduced diameter recess  62  which is provided to facilitate attachment and removal of the depth guide attachment  44  from the interface  42 . As shown in  FIG. 3 , the recess  62  has a reduced diameter or depth that is generally coextensive with the deepest, i.e., the center of the groove  60  as is best shown in  FIG. 9 . 
     As is also best shown in  FIG. 9 , the outer end portion  54  between the end flange portion  56  and the groove  60  is slightly tapered and of reduced diameter to cooperate with the depth guide attachment  44  enabling it to be snap fitted on and relatively easily removed from the accessory interface  42 . The accessory interface  42  is preferably made of a plastic material or a plastic-like material that has some resilience, although it may be made of metal such as aluminum or steel if desired. The thin walled inner end portion  46  contains the slits  50  for the purpose of providing increased flexibility so that the accessory interface  42  can be snap fitted onto the cylindrical portion  48  of the nose portion  18 . Once it is snap fitted into place, the outer end portion  54  has a relatively substantial outwardly extending tab  64  that has an aperture  66  sized to receive a screw or the like that can be threaded into an opening (not shown) in the nose portion  18  to firmly hold the accessory interface  42  in place. 
     With regard to the depth guide attachment  44  and referring to FIGS.  1  and  4 - 8 , it comprises a relatively thin body portion  70  that has a central opening  72  in which a raised rib  74  is located that extends around a substantial portion of the central opening  72  of the body  70  as shown in  FIG. 8 . The rib  74  engages the groove  60  of the accessory interface  42  in a manner which enables the body  70  to rotate relative to the accessory interface  42 . 
     The depth guide attachment  44  also comprises a depth guide member, indicated generally at  76 , which includes an elongated cylindrical mounting portion  78 , a transition portion  80 , and an outer end portion  82  which is in the shape of a truncated conical volume having a relatively flat end surface  84 . The mounting portion  78  and transition portion  80  is made of generally cylindrical aluminum stock or other metallic stock and has a relatively small diameter of ¼ inch or less. It is sized to be sufficiently strong that it will not be easily bent, and is preferably made of cylindrical stock so that it can be rotated in a suitable aperture of the body  70 . Moreover, it is preferably slidable therein so that the position of the end surface  84  relative to the blade can be adjusted to control the depth of cut that is being achieved by the blade  26  during operation of the power tool  10 . 
     The transition portion  80  is provided so that rotation of the depth guide member  76  about the axis of the mounting portion  78  can be made to vary the position of the end surface  84  appropriately on a work piece or work surface that is being cut. In this regard, transition portion  80  is preferably angled within the range of about 30 to about 50 degrees relative to said cylindrical mounting portion  78 . It should be understood that the outer end portion  82  can be made of a relatively hard but somewhat resilient material such as rubber or the like so that it will not scratch or mar a surface of material that is being cut. 
     Once the depth guide member  76  is adjusted to its desired position by sliding and rotating the member relative to the body  70 , it can be locked in place by a locking mechanism, indicated generally at  90 . The locking mechanism generally comprises a locking knob  92  with a threaded rod portion that threadably engages a nut positioned in the body  70  or the like (not shown), but which is located in a portion  94  of the body  70 . The knob  92  has a rod end portion  96  that contacts an outer surface of the cylindrical mounting portion  78 . Tightening rotation of the knob  92  will cause the threaded portion to be moved inwardly toward the cylindrical mounting portion of the depth guide member to lock the same. Thus, the depth guide member will be locked in place depending upon the amount of force that is applied by rotating the knob  92 . 
     It should also be understood that the locking mechanism  90  not only locks the depth guide member in place, but also locks the body  70  so that it will not rotate relative to the accessory interface  42 . This is achieved by a transfer member  98  which preferably consists of a preferably cylindrical member  98  that fits within an aperture  100  in the body  70  and has a length sufficient so that when the locking mechanism  90  is tightened, the transfer member  98  will be brought into contact with the accessory interface  42  to lock the body  70  in place and prohibit it from being rotated. An opposite end  102  of the transfer member  98  may be appropriately curved to fit around a portion of the circumference of the cylindrical mounting portion  78  as shown in  FIG. 8 . The thickness of the body portion  70  is preferably minimized, but is slightly larger than the diameter of the cylindrical mounting portion  78  and may be ½ inch or less. This contributes to the ease of use and unobtrusiveness of the depth guide attachment  44 . Because of its compact design, it can be mounted onto the accessory interface  42  as well as removed from it without removing the blade  26 . 
     While various embodiments of the present invention have been shown and described, it should be understood that other modifications, substitutions and alternatives are apparent to one of ordinary skill in the art. Such modifications, substitutions and alternatives can be made without departing from the spirit and scope of the invention, which should be determined from the appended claims. 
     Various features of the invention are set forth in the following claims.