Abstract:
An elbow or right angle attachment for a power tool converts the torque of the power tool drive shaft to a transverse shaft which is supported by a housing to extend angularly with respect to the drive shaft. A pinion gear is mounted on the power tool drive shaft and a face gear is mounted on the transverse shaft interiorly of the housing. The face gear and pinion gear engage one another when the elbow attachment housing is mounted to the power tool housing. The pinion gear has teeth with a face width which allows for variability in the precise mounting of the elbow attachment housing to the power tool housing, without any significant resultant detriment to operation of the device.

Description:
FIELD OF THE INVENTION 
     The present invention pertains to right angle or elbow attachments for power driven tools, and more particularly pertains to elbow attachments for mounting to power tools to drive an output shaft perpendicular to the drive shaft of the power tool. 
     BACKGROUND OF THE INVENTION 
     Several elbow attachments for use with power tools are currently available in the marketplace; however, each of the presently available elbow attachments suffers a significant shortcoming. Currently available elbow attachments are of two general types. 
     One type of commonly employed elbow attachment utilizes a pair of bevel gears to transfer the torque from the drive shaft of the power tool to the transverse shaft of the elbow attachment, which transverse shaft is supported by the elbow attachment housing perpendicular to the power tool drive shaft. That is, a first bevel gear is mounted to the drive shaft of the power tool, and a second bevel gear is mounted on the transverse shaft of the elbow attachment. The first and second bevel gears are disposed such that when the elbow attachment is mounted to the power tool, the first and second bevel gears mesh to effect transfer of the torque from the power tool drive shaft to the transverse shaft of the elbow attachment. A particular shortcoming of this type of elbow attachment is that it is necessary for the two bevel gears to be accurately positioned with respect to one another for the gears to properly mesh. Hence, this arrangement does not allow for any significant variability in the positions of the two bevel gears, and therefore it does not allow for any variability in the precise position at which the elbow attachment is mounted on the power tool. Since it is difficult to provide such high precision in the mounting of the elbow attachment to the power tool housing without increased complexity of design and/or cost, elbow attachments which utilize a pair of bevel gears are subject to improper meshing of the bevel gears and accelerated wear, as well as increased noise. 
     In another type of commonly employed elbow attachment, the housing of the elbow attachment supports both a longitudinal shaft and a transverse shaft, with the shafts supporting respective gears which mesh with one another to transfer the torque from the longitudinal shaft to the transverse shaft. The longitudinal shaft is engageable with the drive shaft of the housing and is disposed for rotation together with the drive shaft about the drive shaft axis. The transverse shaft extends perpendicular to the longitudinal shaft. The longitudinal and transverse shafts are maintained in their respective positions within close tolerance, such as by their support on respective bearings, and therefore the gears maintain good meshing. A particular shortcoming of this type of elbow attachment is its requirement of the longitudinal shaft and its associated bearings, which add significantly to the cost and size of the device. 
     Accordingly, there is a need for an elbow attachment which allows for some variability in its engagement with a power tool housing while still maintaining good meshing of the gears which transfer the torque to the transverse shaft, and which does not require a second shaft and associated bearings in addition to the transverse shaft to allow for a lower cost product. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, an elbow attachment is provided for use with power tools having a housing which supports a drive shaft which is rotary about its longitudinal axis and which protrudes externally of the power tool housing at a driving end of the housing. 
     A pinion gear is detachably mountable directly on the drive shaft of the power tool at a location externally of the power tool housing and at a predetermined distance from the driving end of the housing, with the pinion gear having gear teeth with faces of predetermined face width which extend substantially parallel with the longitudinal axis of the power tool drive shaft. An elbow member is provided, comprising an elbow member housing having a power tool engaging end which is engageable with the power tool housing adjacent its driving end, with a transverse shaft having a longitudinal axis and supported by the elbow member housing to be substantially perpendicular to the longitudinal axis of the drive shaft of the power tool upon engagement of the elbow member housing with the power tool housing, with the transverse shaft having a tool engaging end disposed externally of the housing for engaging a tool, and with a face gear having gear teeth which extend substantially parallel with respect to the longitudinal axis of the transverse shaft, with the face gear being mounted on the transverse shaft at a predetermined position at which the teeth of the face gear are engageable with the teeth of the pinion gear when the elbow member housing is engaged with the power tool housing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings, wherein like elements are referenced alike: 
     FIG. 1 is an exploded, perspective view of a prior art elbow attachment which utilizes a longitudinal shaft in addition to a transverse shaft. 
     FIG. 2 is an exploded, perspective view of an elbow attachment embodying various features of the present invention; and 
     FIG. 3 is a perspective view of the elbow attachment of FIG. 2 mounted to a power tool housing, with a cutaway to illustrate the engagement of the pinion and face gears. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An elbow attachment embodying various features of the present invention is illustrated in FIGS. 2 and 3 and referred to generally by reference numeral  20 . The elbow attachment  20  has an elbow attachment housing  22  which preferably has a split line  24  to define a first housing portion  26  and a second housing portion  28  which are engageable with one another along the split line  24 . Screws  25  may be employed to securely hold the two housing portions  24  and  26  together. With reference to FIG. 2, the housing  22  supports a transverse shaft  30  on a pair of bearings  32  for low friction rotation of the transverse shaft  30  about its longitudinal axis. The transverse shaft  30  has a tool engaging end  34  which extends externally of the housing  22 , and which has means for engaging a tool bit. In the illustrated embodiment, a threaded portion  36  is provided adjacent the tool engaging end  34  of the transverse shaft  30  for engaging a collet and collet nut assembly  38 ; however, as will be readily apparent to those skilled in the art, any of a wide variety of arrangements for engaging tool bits are currently well known and employable with the elbow attachment  20  of the present invention, and the invention is in no way limited to transverse shafts having threaded portions nor limited to use with collets. 
     The elbow attachment housing  22  is engageable with a power tool housing  48  of a power tool  50 . In the illustrated embodiment, the power tool housing  48  has an external threaded portion  52  which is threadably engageable with an internally threaded portion  54  of the elbow attachment housing  22  to detachably secure the elbow attachment  20  to the power tool  50 . 
     A pinion gear  44  is securely and detachably mountable directly on the drive shaft  56  at a location externally of the power tool housing  48  and at a predetermined distance from the driving end  58  of the power tool housing  48 . The pinion gear  44  has gear teeth  60  with faces which extend substantially parallel with one another and with the longitudinal axis of the power tool drive shaft  56 . Preferably, the pinion gear  44  has a plurality of teeth  60  extending radially outwardly and uniformly angularly spaced. 
     A face gear  40  is secured on the transverse shaft  30  internally of the elbow member housing  22 , for rotation together with the transverse shaft  30 . The face gear  40  has teeth  42  on one of its sides which extend substantially parallel to the longitudinal axis of the transverse shaft  30 . The face gear  40  is secured to the transverse shaft  30  at a location such that the teeth  60  of the pinion gear  44  mesh with the teeth  42  of the face gear  40  upon and throughout engagement of the elbow member  20  with the power tool, as best seen in FIG.  3 . 
     In accordance with one aspect of the present invention, the elbow attachment  20  of the present invention does not require great accuracy in the distance of the face gear  40  toward or away from the driving end  59  of the power tool  48 , hence allowing for inaccuracy or variability in the mounting of the elbow attachment housing  22  to the power tool housing  48 , particularly allowing for inaccuracy in the longitudinal direction of the output shaft axis, without any significant detrimental effect on the proper operation and longevity of the device. This beneficial aspect of the elbow attachment of the present invention is attributable to the fact that the faces of the pinion gear teeth  60  all extend parallel to the power tool axis  56  and extend to a predetermined face width or depth. The elbow attachment housing  22  is configured such that the teeth  42  of the face gear  40  mesh with the teeth  60  of the pinion gear  44  at a location spaced from either end  62  of the pinion gear  44  when the elbow attachment  20  is fully mounted on the power tool  50 . Since the profiles of the teeth  60  of the pinion gear all remain equal throughout the depth of the pinion gear, it does not make any difference at what point, intermediate the ends  62  of the pinion gear teeth  60 , the teeth  42  of the face gear  40  mesh with the teeth  60  of the pinion gear  44 . Hence, the elbow attachment housing  22  is preferably configured such that the teeth  42  of the face gear  40  mesh with the teeth  60  of the pinion gear  44 , when the elbow attachment is fill and ideally mounted on the power tool  50 , at a location sufficiently spaced from the end  62  of the pinion gear  44  which faces the power tool  50 , such that improper mounting of the elbow attachment or unintentional loosening of the elbow attachment from the power tool during usage will not result in detrimental operation of the device. For instance, with the threaded engagement of the elbow attachment with the power tool as in the illustrated embodiment, incomplete screwing down of the elbow attachment housing  22  or slight unscrewing of the elbow attachment housing  22  will result in the face gear teeth  42  engaging with the pinion gear teeth  60  at a location further away from the power tool  48 , but without any significant affect on the operation of the elbow attachment  20 . Similarly, over screwing of the elbow attachment housing  22 , such as attributable to wearing down of the engaging end  68  of the elbow attachment housing  22 , will result in the face gear teeth  42  engaging with the pinion gear teeth  60  at a location closer toward the power tool  50 . 
     The aforementioned advantageous aspect of the elbow attachment of the present invention allows for the use of means for engaging the elbow attachment to the power tool which are significantly less expensive and/or complex than is required with prior art elbow attachments which require greater accuracy and precision in the engagement of its gears. Likewise, the position of the pinion  44  on the drive shaft  56  does not have to be as accurate with the elbow attachment of the present invention as would be required were a pair of bevel gears or the like employed, which require greater accuracy and precision in the engagement of its gears. 
     With reference to the prior art elbow attachment of FIG. 1, it will now be appreciated that since the elbow attachment  20  of the present invention employs only one shaft mounted on bearings, rather than two shafts mounted on respective bearings as in the prior art designs of the type illustrated in FIG. 1, still farther cost savings in the production of the elbow attachment  20  of the present invention may be achieved relative to production of prior art elbow attachments. 
     The transverse shaft  30  has an integral enlarged region  70  with an aperture  72  therethrough, and the housing has a notch  74  through which an implement may be inserted into the aperture  72  when it is rotatably aligned with the notch  74 , by which the transverse shaft  30  may be held stationary against rotation during engagement and disengagement of tool bits. 
     A particularly advantageous feature of the present invention is that it allows for utilization of the power tool&#39;s already-existing tool bit holder for the pinion gear, such that no separate mechanism for securing the pinion gear to the drive shaft is required. That is, the elbow attachment lends itself to retrofitting onto a wide range of currently existing power tools, with the pinion gear mounted to the drive shaft via the standard tool bit mounting mechanism already provided on the power tool. 
     Though the invention is described herein by way of preferred and illustrated embodiments, the invention is broader in scope than any specific embodiments, and many variations and modifications will be readily apparent to those skilled in the art. All such modifications and variations are within the scope and spirit of the present invention which is set forth in the accompanying claims.