US 3712352 A
A depth adjuster made of injection molded plastic parts has a bit housing which screws onto the projecting externally threaded nose on the gear housing of a standard electric powered hand tool provided with a positive pressure engaged clutch. The bit housing has a bore to accommodate the clutch chuck and the shank of a bit for a screw head. The bore passes through an extending neck on the bit housing which is externally threaded and provided with an outwardly facing shoulder having locking tabs. Onto this neck is threaded a locator assembly of a type designed for a particular application. This assembly has three parts which are snapped into place and remain assembled even when disconnected from the bit housing. These parts consist of (1) a locking collar with locking slots which engage with the locking tabs, (2) a locator sleeve which has limited axial movement and a non-rotative movement with respect to the locking collar, and (3) a compression spring which axially urges the locking collar rearwardly toward the outer extreme of its limited motion with respect to the locator sleeve.
Description (OCR text may contain errors)
United States Patent 1 Lafferty, Sr.
[ Jan. 23, 1973 DEPTH ADJUSTERS AND INTERCHANGEABLE LOCATORS FOR SCREWDRIVERS  Inventor: Gary S. Lafferty, Sr., Milwaukee,
 Assignee: Milwaukee Electric Tool Corporation, Brookfield, Wis.
 Filed: May 6, 1971  Appl. No.: 140,728
UNITED STATES PATENTS 3,527,273 9/1970 Falter ..l44/32 2,790,47l 4/1957 Graybill ..l44/32 2,940,488 6/1960 Riley ..l44/32 3,454,059 7/1969 Sindelar... ..I44/32 3,298,410 l/l967 Morifuji ..l44/324 Primary ExaminerDonald R. Schran Attorney-John W. Michael, Gerrit D. Foster, Bayard H. Michael, Paul R. Puerner, Joseph A. Gemigani, Robert E. Clemency, Andrew 0. Riteris, Glenn A. Buse and Spencer B. Michael [5 7] ABSTRACT A depth adjuster made of injection molded plastic parts has a bit housing which screws onto the projecting externally threaded nose on the gear housing of a standard electric powered hand tool provided with a positive pressure engaged clutch. The bit housing has a bore to accommodate the clutch chuck and the shank of a bit for a screw head. The bore passes through an extending neck on the bit housing which is externally threaded and provided with an outwardly facing shoulder having locking tabs. Onto this neck is threaded a locator assembly of a type designed for a particular application. This assembly has three parts which are snapped into place and remain assembled even when disconnected from the bit housing. These parts consist of (1) a locking collar with locking slots which engage with the locking tabs, (2) a locator sleeve which has limited axial movement and a nonrotative movement with respect to the locking collar, and (3) a compression spring which axially urges the locking collar rearwardly toward the outer extreme of its limited motion with respect to the locator sleeve.
7 Claims, 8 Drawing Figures PATENTEUJANZB I973 I 3.712.352
sum 1 OF 2 @ZWPW DEPTH ADJUSTERS AND INTERCHANGEABLE LOCATORS FOR SCREWDRIVERS BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to an improved depth adjuster for electric powered hand tools used to apply self drilling, self tapping fasteners, drywall fasteners, and the like. The invention specifically features: the use of injection molded parts; a locator assembly which cannot be disassembled without destruction; a standardized bit housing; and a standardized locking collar and locking collar spring with which a variety of locating sleeves for different applications can be assembled to provide locator assemblies suited for use in particular applications.
2. Description of the Prior Art Depth adjusters for positive clutch electric powered hand tools used to apply fasteners including: (1) a bit housing to be mounted on the tool; (2) a locking collar; (3) a locator sleeve threadably mounted on the bit housing; and (4) a locking collar spring are well known prior art. Examples are shown and described in U.S. Pat. No. 2,940,488 issued June 14, 1960, and in the Service Parts List of Milwaukee Electric Tool Corp. identified as Bul. 54-42-5102 Catalog No. 6746-1 and Bul. 54-42-5454 Catalog No. 6796-1 (copies of which are attached for including in the tile of this application).
In current practice the parts of the prior art depth adjusters are fabricated from steel at relatively high cost. Also a decided detractor is that the parts can be easily disassembled and when this is done parts, particularly the spring, are lost.
BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:
FIG. 1 is a fragmentary view in axial cross-section of an electric powered hand tool having applied to it a depth adjuster embodying the present invention;
FIG. 2 is an exploded view in perspective showing the bit housing and locator assembly constituting parts of the depth adjuster embodying the present invention;
FIG. 3 is an exploded view in perspective showing the elements comprising the locator assembly;
FIG. 4 is an axial sectional view of the locator assembly;
FIG. 5 is a sectional view similar to FIG. 1 showing the parts when driving the screw with the clutch in engagement;
FIG. 6 is a sectional view similar to the view FIG. 5 showing the parts in stopped position with screw head flush with the work surface;
FIG. 7 is a sectional view similar to that of FIG. 6 showing the depth adjuster adjusted to stop driving action prior to the complete setting of the screw; and
FIG. 8 is a sectional view similar to the view of FIG. 5 showing a depth adjuster and locator sleeve adjusted to seat a screw below the surface of a workpiece.
DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings by reference numerals, there is illustrated for the purpose of describing this invention an electric powered hand drill the design of which makes it particularly suitable for driving screws of various natures. This drill has a clutch gear 10 mounted within its gear housing 11. This clutch gear receives motor torque through its geared teeth and transmits it to its clutch teeth. Mounted within an extending neck 13 of the gear housing is a clutch chuck 12 which is carried in a roller bearing 14. This clutch chuck has a standard non-circular bore for receiving the shank of a bit. The interchanging teeth and recesses of the clutch gear and the clutch chunk are of standard well-known design. Not shown is a spring which urges the clutch chuck forwardly to the non-driving position shown in FIG. 1. When force is applied by the tool operator to the drill the driving bit forces the clutch chuck rearwardly into the driving position shown in FIG. 5. This part of the drill and positive clutch are not part of this invention and are described to show the nature of the drill to which the depth adjuster of this invention is attached.
Mounted on the neck 13 is a bit housing 16. This bit housing is formed by injection molding of a plastic known in the trade as Black Nylatron GS, a product of The Polymer Corp. It is a molybdenum-disulfide filled nylon moisture stabilized at 2 percent water content. It has an internal bore with an enlarged inner end with internal threads and an outer projecting neck 18 provided with external male adjustment threads 19. A screwdriving bit 20 of conventional design is housed in this bit housing and conventionally engaged with the clutch chuck 12. A locator assembly later described in detail is supported on the neck 18. As shown in FIG. 2 lands 22 and recesses 24 are formed in angular spaced relation on the outside of the enlarged end. Four angularly spaced reference arrows may also be formed on certain of the lands 22 to show the relative rotational positions between the bit housing and locking collar. An important part of the bit housing is the forwardly facing surface 26 from which project locking tabs 28 the purpose of which will be hereinafter described.
A feature of this invention is the locator assembly shown in the exploded views of FIGS. 2 and 3 before its parts are assembled and in the assembled view of FIG. 4 with its parts assembled. This assembly consists of three mechanical elements: (1) a locking collar 30; (2) a locator sleeve 32; and (3) a compression spring 34. When these are assembled as shown in FIG. 4 they may not be disassembled without destroying the interlocking feature hereinafter described. The advantage of this is that the operator in making an adjustment for depth control cannot accidentally disassemble the parts and in particular allow the spring to fly out of position and become lost.
The locking collar 30 is also formed by injection molding of the same material as set forth above in the description of the bit housing 16. It has an internal bore 36 in which the spring 34 is contained. As clearly shown in FIG. 2 it has an intumed flange 38 at the inner end of the bore. The inner flange 38 has angularly spaced locking slots 42 into which the locking tabs 26 on the bit housing fit when aligned to prevent relative rotation between the bit housing 16 and the locking collar 30 during normal operation of the driver. Each time there is an alignment between the tabs 28 and the slots 42 the compression spring 34 acting between inner end of the locator sleeve and the flange 38 forces the slots 42 toward and into engagement with the tabs 28. The locking collar 30 is preferably provided with angularly spaced lands 44 and recesses 46. Reference numerals such as 1 through 4 may also be formed on certain spaced lands 44 to align the reference arrows on the bit housing with reference members to help the operator change adjustment as later described.
The locking collar 30 with compression spring 34 wormed into the bore 36 comprises a standardized subassembly which is the same size for each different complete assembly which includes locator sleeves designed for different applications. Since the mechanical characteristics of the various locator sleeves which cooperate with locking collar and spring subassembly and the adjuster thread 19 on the bit housing are the same, only one a so-called standard locator sleeve will be described in detail. The other mechanical shapes or characteristics which adopt the applicator for special uses, sometimes identified as washer head, drywall head, and limited clearance head are old in this art and do not form part of this invention other than to relate that such shapes as arerequired and which were heretofore fabricated from metal can be formed by injection molding in the same manner and from the same material as described for the bit housing.
As shown in FIGS. 3 and 4, an inturned flange 40 at the outer end of the bore 36 of the locking collar has angularly spaced slots 48 into which are slidably fitted longitudinally extending angularly spaced lands 50 on the locator sleeve 32. Between such lands the locator sleeve has rearwardly extending flexible fingers 52 the ends of which support radially projecting locking teeth 54. The forward surface of these teeth is sloped as shown in FIG. 4 so that during assembly the fingers will be inwardly depressed by the angularly spaced portions of the flange 40 and as these teeth slide inwardly and pass beyond such portions they will be sprung outwardly to the position shown in FIG. 4 and the teeth will engage the inner face of such portions to prevent disassembly of the locator sleeve from the locking collar.
The locator sleeve 32 is shaped as shown in FIG. 2 and is classified as standard. It has a frusto-conical nose 56 and a central bore 58. At the inner end of this bore are internal female adjustment threads 60 which mate with the external threads 19 on the neck of the bit housing in the manner shown in FIG. 1.
The adjustment threads on the locator sleeve and bit housing are at a pitch of 16 threads per inch. Thus, as the locator sleeve assembly is rotated, each full revolution represents one-sixteenth inch axial movement. The assembly may be locked in one-fourth turn increments, resulting in a fine adjustment in one sixty-fourths inch increments. For the convenience of the user, the numbers 1 through 4 on the perimeter of the locking collar can be aligned with four arrows on the bit housing. As a result, when the operator wishes to change the adjustment one thirty-seconds inch, he may choose any arrow and using it as a reference point, rotate the locator sleeve assembly two numbers, correspondingly changing the adjustment two sixty-fourths inch.
Since the locking collar may be moved axially with respect to the locator sleeve and rotated to also rotate the locator sleeve the operator may make the adjustment by one hand. The systems presently offered require two hands to make an adjustment, one must hold the locking collar and the other turn the locator sleeve.
As previously stated locator sleeves may be offered with various characteristics to create different assemblies. It has been found advantageous to provide complete factory made and inspected locator assemblies as this insures that the quality of the fit between the locator sleeve and the screwdriving bit is readily maintained over a prolonged period. The .lubricant which is inherent in the thermoplastic material used in these assemblies will prolong the life of the relatively expensive screwdriving bit and prolong the life of the desired quality of fit. This is not true of the assemblies manufactured from steel.
1. A depth adjuster adapted for mounting on an electric powered hand tool, said tool having a positive pressure engaged clutch including a clutch chuck for receiving a bit, and a gear housing having an externally threaded neck, said adjuster comprising:
a. a bit housing threadedly mounted on the neck of the tool, said bit housing having spaced locking tabs and an adjusting thread; and
b. a locator assembly consisting of (1) a locking collar with spaced locking slots into which said locking tabs fit, (2) a locator sleeve carried by said locking collar and having limited axial movement and non-rotative movement with respect thereto, said locator sleeve having an adjusting thread engaged with the adjusting thread on said bit housing, and (3) a compression spring acting directly between said locking collar and said locator sleeve to move said locator sleeve to the outer limit of its limited axial movement with respect to said locator sleeve.
2. A depth adjuster as defined in claim 1 wherein the limited axial movement of said locking collar relative to said locator sleeve is accomplished by connecting means including a resilient member on one which snaps into engagement with an abutment on the other of said locking collar or locator sleeve.
3. A depth adjuster as defined in claim 2 wherein said connecting means prevents disassembly of the locator assembly without destruction of connecting means.
4. A depth adjuster as defined in claim 1 wherein said bit housing, said locking collar and said locator sleeve are plastic parts formed by injection molding of plastic identified as molybdenum-disulfide filled nylon.
5. A depth adjuster as defined in claim 4 wherein:
a. said locking means consists of locking tabs projecting from a forwardly facing surface on the bit housings; and
b. said locking means on said bit housing consists of spaced locking slots in an inner flange into which said locking tabs fit when aligned to prevent relative rotation between said bit housing and said locking collar to maintain the required depth adjustment.
A depth adjuster as defined in claim 5 wherein:
a. said locking collar has an internal bore in which said compression spring is contained and an inturned flange at the outer end of said bore with angularly spaced slots; and
d. said tabs and slots being angularly spaced with relation to said pitch so that the operator may change the depth adjustment by two sixth-fourths inch by rotating said locator sleeve so that a reference marking on said sleeve is moved into alignment with a reference marking on said bit housing spaced two lands from the reference marking on said bit housing with which reference marking on said sleeve was initially aligned.