Abstract:
An oscillating power tool includes a drive motor (M) producing rotary motion and an oscillating mechanism ( 30 ) for converting the motor rotary motion to an oscillatory side-to-side movement. The oscillating mechanism ( 30 ) includes a link ( 32 ) driven by an eccentric shaft ( 16 ) of the motor (M), a drive arm ( 40 ) that drives the hub ( 45 ) of the working tool (B) in oscillating motion, and a bearing arrangement ( 37 ) between the drive arm ( 40 ) and the link ( 32 ) that isolates relative rotation and translation between the components while still imparting an oscillatory motion to the drive arm ( 40 ).

Description:
REFERENCE TO RELATED APPLICATION AND PRIORITY CLAIM 
       [0001]    This application is a utility filing of and claims priority to co-pending provisional application No. 61/918,749, filed on Dec. 20, 2013, the entire disclosure of which is incorporated herein by reference. 
     
    
     FIELD 
       [0002]    This invention relates to the field of power tools, and more particularly to a handheld power tool having an oscillating tool or blade. 
       BACKGROUND 
       [0003]    Oscillating power tools are lightweight, handheld tools configured to oscillate various accessory tools and attachments, such as cutting blades, sanding discs, grinding tools, and many others. The accessory tools and attachments can enable the oscillating power tool to shape and contour workpieces in a many different ways. 
         [0004]      FIG. 1  illustrates the operating end of a conventional oscillating power tool  10  having a generally cylindrically shaped housing  12  and a tool holder  14 , or tool head, located at a front end of the housing. The tool holder  14  is adapted to accept a number of different tools or tool accessories, such as a scraping tool or cutting blade, for instance. The tool holder  14  is configured to oscillate the tool from side to side by way of a reversing angular displacement about an axis A that is generally perpendicular to the longitudinal axis L of the tool housing. The housing  12  can be constructed of a rigid material such as plastic, metal, or composite materials such as a fiber reinforced polymer. The housing  12  can include a nose housing (not shown) to cover the front of the tool, the tool holder, and the oscillating mechanisms. 
         [0005]    The housing  12  includes a handle portion formed to provide a gripping area for an operator. The housing  12  is further configured to carry a power supply and a motor M that drives a motor drive shaft  15  that has an eccentric drive portion  16  that is coupled to an oscillating mechanism  18  and more particular engages a spherical drive bearing  20  disposed between the arms  23  of a yoke  22 . The rotation of the motor shaft produces a translation of the spherical bearing  20  which in turn produces a lateral translation of the yoke  22 . The bearing  20  must be spherical to “release” the rotational degree of freedom between the bearing and yoke. Consequently, the contact between the spherical bearing and the yoke is essentially a point contact on each arm  23 . Since the rotational degree of freedom is released between the components there is relative movement and sliding occurring at the interface, which leads to significant heat build-up and wear. The sliding at this interface also generates a moment in the bearing  20  that introduces a load in the direction of the longitudinal axis L. 
         [0006]    The interface between the spherical bearing  20  and the yoke  22  also releases the X-direction translation parallel to the axis A since the eccentric drive portion  16  drives the bearing up and down. The yoke  22  is locked in this degree of freedom. In theory, the spherical bearing would roll at the X-direction interface, but testing has revealed that the bearing is only intermittently contacting the two arms  23  of the yoke  22  and is constantly changing the rolling direction and constantly sliding. This sliding movement generates heat which eventually damages the bearing. 
         [0007]    Moreover, since the interface between the spherical bearing  20  and the yoke  22  releases the up and down motion in the X-direction, some clearance is required between the bearing and yoke arms. This clearance causes banging as the bearing impacts the yoke, thereby producing an impact load that further reduces the life of the bearing. 
         [0008]    It can be seen that the conventional oscillating mechanism has a deleterious impact on the life of the spherical bearing  20 . The sources of this weakness includes: a) the point contact between the spherical bearing and the yoke arms; b) sliding of the outer race of the bearing due to the relative rotation between bearing and yoke; c) up and down sliding of the bearing; and d) banging or impacting of the bearing due to necessary looseness of the bearing-yoke interface. Robustness, or more accurately, lack of robustness limits the size of blade and the operating conditions of the conventional oscillating tool, which can ultimately limit cutting performance. A larger blade increases the load on the oscillating mechanism  14  which consequently increases the load on the spherical bearing  20 . An increase in operating speed also increases the bearing load. This increased load ultimately requires that limits be placed on the size and operating speed of the tool. Consequently, there is a need for an oscillating mechanism that overcomes these problems and allows for higher “power” and performance operation of an oscillating tool. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a perspective view of an oscillating power tool including an oscillating mechanism. 
           [0010]      FIG. 2  is a perspective view of the drive components and oscillating mechanism for an oscillating power tool according to one aspect of the present disclosure. 
           [0011]      FIG. 3  is an enlarged side cross-sectional view of the drive components and oscillating mechanism shown in  FIG. 2 . 
           [0012]      FIG. 4  is an exploded view of the drive components and oscillating mechanism shown in  FIGS. 2 and 3 . 
           [0013]      FIG. 5  is a side view of a power tool with a circular saw blade using the oscillating mechanism shown in  FIGS. 2-4 . 
           [0014]      FIG. 6  is a side view of a power tool with an alternative oscillating blade using the oscillating mechanism shown in  FIGS. 2-4 . 
           [0015]      FIGS. 7 a -7 b    are cut-away views of an oscillating mechanism similar to the mechanism of  FIGS. 2-4  with a bearing supporting the eccentric motor drive shaft. 
           [0016]      FIG. 8  is a representation of an oscillating mechanism according to another aspect of the present disclosure. 
           [0017]      FIG. 9  is a representation of an oscillating mechanism according to a further aspect of the present disclosure. 
           [0018]      FIG. 10  is a side partial cross-sectional view of an oscillating mechanism having a dual output according to one aspect of the present disclosure. 
           [0019]      FIG. 11  is a side view of an oscillating and reciprocating mechanism according to a further aspect of the present disclosure. 
           [0020]      FIGS. 12 and 13  are representations of an oscillating mechanism incorporating a rotating gear driving a pair of links. 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    For the purposes of promoting an understanding of the principles of the disclosure, reference will now be made to the embodiments illustrated in the drawings and described in the following written specification. It is understood that no limitation to the scope of the disclosure is thereby intended. It is further understood that the present disclosure encompasses any alterations and modifications to the illustrated embodiments and includes further applications of the principles of the disclosure as would normally occur to one of ordinary skill in the art to which this disclosure pertains. 
         [0022]    In order to address the problems of the conventional oscillating power tool discussed above, the present disclosure contemplates an articulating mechanism that eliminates the point contact and sliding movement aspect of the prior oscillating mechanism. An articulating mechanism  30  shown in  FIGS. 2-4  is coupled between the eccentric drive portion  16  of the motor M and an oscillating working tool or blade B. The eccentric drive portion  16  may be supported by a roller or other suitable bearing R disposed within the housing  12  of the tool. In one aspect, the oscillating mechanism  30  includes a link  32  having a first link housing  33  and a second offset link housing  34  that is offset below the first housing  33  relative to the longitudinal axis L. A counterbalance  17  may be mounted to the motor drive shaft  15  or the eccentric portion  16  at a position 180° opposite the second link housing  34 . The counterbalance  17  has a mass generally equal to the mass of the second link housing  34  to balance the inertial force generated by eccentric rotation of the second link housing. The counterbalance thus reduces the lateral load on the drive bearing M supporting the eccentric drive portion  16 . It is noted that no counterbalance is required for the first link housing  33  since that housing is aligned with the longitudinal axis L and does not generate any inertial force. 
         [0023]    The first link housing  33  is configured to support a bearing  36  through which the eccentric drive portion  16  passes. The bearing  36  may be a conventional roller bearing to accommodate the rotation of the drive shaft within the link housing  33 . The second or offset link housing  34  is configured to receive a second bearing  37 . However, the second bearing  37  is configured to release relative rotation between the second offset link housing  34  and a drive arm  40 . The drive arm  40  thus terminates in a spherical end  42  that is seated within the second bearing  37 . The second bearing may thus be in the form of a low-friction bushing or other bearing interface that releases rotation between the two components. As best seen in the cross-sectional view of  FIG. 3 , the spherical end  42  of the drive arm  40  is in a close running fit within the second bearing  37  and is permitted to rotate about the axis of the spherical end  42  as well as to translate along the axis of the second link housing  34 . The interface between the spherical end and the bearing thus also releases relative translation between the drive arm  40  and the offset link housing  34 . The configuration of the bearing and spherical end of the drive arm thus limits the force transmission between the eccentric shaft and the drive arm to the vertical direction V. 
         [0024]    The drive arm  40  is coupled to a hub  45  and shaft  47  that is supported for rotation by a bearing support  48 . The shaft  47  is coupled to the working tool B so that rotation of the hub and shaft produces the desired oscillation of the working tool. The drive arm  40  is thus fixed to the hub  45  such as by engagement within a bore  46 . The end of the arm may be threaded and engaged by a nut  47 , as illustrated in  FIGS. 7 a -7 b   . It can be appreciated that as the drive arm  40  moves up and down in the direction V shown in  FIG. 3  this motion pivots the hub  45  and thereby oscillates the tool B. The up and down movement V of the drive arm  40  is accomplished by up and down movement of the link  32  in the same direction V that occurs as the eccentric motor shaft  16  rotates. The eccentric movement of the eccentric shaft  16  causes the link  32  to not only move up and down in the direction V but also side-to-side in a direction parallel to the direction A ( FIG. 2 ). However, since the interface between the drive arm  40  and the link  32  is a spherical interface the side-to-side movement is isolated from the drive arm. Moreover, the spherical end  42  is free to translate within the offset second link housing  34  to further isolate all rotation and translation other than the up-and-down movement V. 
         [0025]    One significant benefit of the oscillating mechanism  30  is that there is no point contact between a bearing and any component of the mechanism. The first bearing  36  may be a conventional roller bearing or similar bearing. The second bearing  37  may be a bushing. Although the component engaging the surface of the second bearing  37  is the spherical end  42  of the drive arm  40 , the interface is a line contact around the circumference of the spherical end  42 . Even as the components wear and the running fit becomes more loose, there is no significant risk of banging or impacting between the spherical end  42  and second bearing  37  because the continuous rotation of the offset link housing  34  will maintain constant pressure on the spherical end as the housing tries to move the spherical end in the eccentric rotation pattern. 
         [0026]    Additional benefits are illustrated in  FIGS. 5 and 6 . As shown in  FIG. 5 , when the working tool B is a circular saw, the oscillating mechanism  30  allows the motor to remain on the longitudinal axis L of the tool  10  which is axially offset from the blade B. This feature allows the tool to be used at a sharper angle relative to the work surface W and allows the blade B o cut more deeply into the work surface. When the working tool B is a blade configured as shown in  FIG. 6 , the oscillating mechanism  30  allows the blade B to be generally in line with the operator&#39;s hand H when used in a standard oscillating orientation. This improves the overall ergonomics of the tool and reduces wrist strain for the operator. 
         [0027]    The oscillating mechanism  30  may be modified as shown in  FIGS. 7 a -7 b   . The mechanism shown in these figures is the same as the mechanism in  FIGS. 2-6  with a modification to the support for the motor drive shaft  15  and eccentric drive portion  16 ′. A housing  49  may be provided to surround the oscillating mechanism components, with the housing  49  fastened to the tool housing  12 . This housing may be configured to support a bearing  50  that receives the end portion  16   a  of the eccentric shaft  16 ′. This bearing supports the drive shaft to eliminate any moment created by the link  32  cantilevered on the end of the shaft. Whereas in the embodiment of  FIGS. 2-6  the link  32  is supported on the eccentric end of the shaft  16 , in the embodiment of  FIGS. 7 a , 7 b   , the end portion  16   a  is aligned along the longitudinal axis to support the motor drive shaft. The shaft  16 ′ further defines an eccentric portion  16   b  that engages the link  32  to impart the eccentric movement upon rotation of the shaft. 
         [0028]    In a further modification shown in  FIG. 8 , the offset link housing  34  receives a bearing  37 ′ that allows a certain amount of “slop” between the bearing and the end  42 ′ of the drive arm  40 ′. The end  42 ′ does not include the spherical configuration in this embodiment. Instead, the “slop” in the modified bearing  37 ′ essentially simulates a spherical joint by allow a certain amount of play in the transmission of movement from the bearing  37 ′ to the drive arm  40 ′. In certain applications, the drive arm  40 ′ only rotates through an angle of ±3 degrees. The modified bearing  37 ′ may be a roller bearing that incorporates a loose fit with a small amount of play between the inner race and the rollers, and/or between the rollers and the outer race. This alternative configuration allows the use of low cost standard components for the second bearing  37 ′ without sacrificing functionality and performance. 
         [0029]    Another modification is shown in  FIG. 9 . In this embodiment, the oscillating mechanism is similar to the mechanism  30  and link  32  except that the drive arm is modified. In particular, the modified drive arm  55  includes a bearing portion  56  that is aligned with the axis of the second offset link housing  34  and an angled portion  57  that is angled toward the longitudinal axis L of the motor. This modified drive arm  55  thus allows the axis A of the working tool to intersect the axis L of the power tool. This modification provides the advantage of an improved depth of cut since the axis of the working tool or blade is shifted closer to the work piece. The orientation of the bearing portion  56  in the modified arm  55  also helps eliminate most of the sliding of the drive arm within the second link housing  34 . The modified drive arm  55  moves in the same manner as the drive arm  40 . 
         [0030]    The oscillating mechanisms described above may be further modified to provide two outputs driven by the same motor. Thus, as shown in  FIG. 10 , the motor shaft  60  may be configured similar to an automotive crank shaft, with two crank sections  61 ,  62  that are angularly offset from each other. As shown in  FIG. 10 , the two crank sections  61 ,  62  are 180° apart, although other angular orientations are contemplated with appropriate modifications to the housing covering the mechanism. The first crank section  61  engages the link  32  to drive the drive arm  40  for the working tool B. The second crank section  62  may engage a link  65  that is configured similar to the link  32 , except that this link drives a second drive arm  66  that oscillates a second hub  67  and associated working tool. 
         [0031]    The oscillating mechanism  30  may be further modified to impart a reciprocating motion to the working tool. As shown in  FIG. 11 , the drive arm  60  may be modified from the drive arm  40  to replace the spherical end with a pin joint  62 . The pin joint allows for relative pivoting between the drive arm and the second link housing  34  but does not allow the end of the drive arm to slide along the axis of the housing. Thus, when the drive arm is moved away from the normal line of action from hub  45  to link  32  the effective length of the drive arm shortens due to the angular offset. This reduction in length pulls and pushes the hub  45  in the direction of the arrow T, thereby imparting a reciprocating motion to the working tool along with the oscillating motion already provided by the mechanism. 
         [0032]      FIGS. 12-13  show a mechanism for imparting oscillating motion that employs a gear  70  driven by the motor M. In  FIG. 12  a bevel gear  76  driven by the motor M engages the gear  70  to rotate the gear about an axis that is perpendicular to the axis of the tool and motor. In  FIG. 13  the gear  70  is directly driven by the motor, but the motor axis is perpendicular to the hand grip portion H of the power tool. In both configurations, a first link  72  is attached to the gear  70  by a pivot pin  73 , and to a second link  74  by a corresponding pin  78 . The second link  74  is attached to the hub  75  to which the working tool is mounted. Rotation of the gear  70  thus imparts an oscillating rotation to the hub and working tool. 
         [0033]    While the power tool and oscillating mechanism have been illustrated and described in detail in the drawings and foregoing description, the same should be considered as illustrative and not restrictive in character. It is understood that only the preferred embodiments have been presented and that all changes, modifications and further applications that come within the spirit of the disclosure are desired to be protected.