US 2730635 A
Description (OCR text may contain errors)
J. A. MccABE 2,730,635
Jan. 10, 1956 PORTABLE ELECTRIC DRILLS 2 Sheets-Sheet l Filed April 4, 1952 figg. .2
YJosep/lf Cabe- Jan. 10, 1956 J. A. MccABE 2,730,635
PORTABLE ELECTRIC DRILLS Filed April 4, 1952 2 Sheets-Sheet 2 n Mi IN V EN TOR.
TTOR EY United States Patent PORTABLE ELECTRIC DRILLS Joseph A. McCabe, Chicago, Ill., assigner to Portable Electric Tools, Inc., Chicago, Ill., a corporation of Illinois Application April 4, 1952, Serial No. 286,479
Claims. (Cl. 3110-50) This invention relates to portable electrically driven tools such as electric drills and the like, and particularly it relates to an arrangement and relationship of the elements of the tool whereby undesired stresses in the tool structure are avoided.
In portable electric tools such as drills, the body of the tool is provided with a handle at or near the rear end of such body, while the working tool such as a drill bit is mounted in a suitable chuck at the forward end of such body, the driving motor and the speed reduction gearing being included within the main body of the tool. Thus, when the tool is operated as in a drilling operation, the user holds and guides the tooi by the means of the aforesaid handle, and in proportion to the load that is encountered by the working tool or drill bit, the user must apply a reactive force to the handle to overcome the tendency of the body of the tool to turn about the axis of the output shaft of the tool. In normal operation of such a portable drill or the like, this reactive force that must be applied to the handle of the tool is relatively slight, but when the drill bit encounters a hard object such as a nail that may be located in the path of the bit, the rotation of the drill bit is, of course, stopped and there is a greatly increased tendency of the body of the drill to rotate. This increased rotative tendency of the body of the drill, of course, normally counteracted by reactive forces applied to the handle by the user, and in prior portable electric drills of the kind to which the present invention relates, it has been found that the torsional forces that are involved in such a situation often cause twisting of the motor frame elements, thus to produce misalignment of the motor bearings with resultant excessive wear in such bearings.
In view of the foregoing, it is the primary object of the present invention to enable such'twisting forces in the motor frame of such a portable tool to be avoided, and another and related object is to so connect or associate the handle of a portable electric drill unit with the other elements of the unit that twisting forces are not applied to the motor frame at any time in the use or operaion of the portable drill unit.
Other and further objects of the present invention will be apparent from the following description and claims and are illustrated in the accompanying drawings which, by way of illustration, shows a preferred embodiment of the present invention and the principle thereof and what I now consider to be the best mode in which l have contemplated applying that principle. Other einbodiments of the invention embodying the same or equivalent principle may be used and structural changes may be made as desired by those skilled in the art without departing from the present invention and the purview of the appended claims.
In the drawings:
Fig. 1 is a side elevational View of a portable drill unit embodying the features of the invention;
Fig. 2 is a fragmentary top plan view of the forward Patented Jan. 10, 1956 portion of the portable electric drill unit shown in Fig. l, portions of the casing or housing being broken away to illustrate details of internal construction;
Fig. 3 is a longitudinal vertical sectional view taken through the portable electric drill unit of Fig. l;
Fig. 4 is a side elevational view of the motor unit of Fig. 3, certain portions of Fig. 4 being shown in vertical cross section; and
Fig. 5 is an elevational View of the forward end of the motor unit as viewed from the line 5-5 of Fig. 3.
For` purposes of disclosure, the present invention is illustrated in a portable electric drill unit 20 having a main housing that is sectional in character and which is afforded by a front or gear box section 21 and a rear housing section 22, such rear housing section 22 being provided with a rigid or integral handle 23 that is in the present case illustrated in the form of a saw-grip handle having a switch operating lever 24 mounted therein in a conventional relationship. Forwardly of the forward end of the gear housing 2l, an output shaft 26 is arranged to carry a tool-mounting means such as a geared chuck 27.
"f he gear housing section 2l is generally cup-shaped in form and has a forward wall ZIP and a generally cylinrical side wall 21S, and the output shaft Z6 is journalcd in an eccentric location in the forward wall 21F by means including a bearing 28. Within the gear housing section 2l, the shaft 26 has gearing associated therewith so that the geared end of a motor shaft 30 may serve, through such gearing, to drive the output shaft 26. The motor shaft 30 extends from the adjacent end of the armature of an electric motor M which will be described in detail hereinafter, and the relationship is such that the tooth end of the shaft 3) is engaged with a first gear 33 that is supported within the gear housing 2 on and in a rotatable relation on the inner end of the output shaft 26. The gear 33 constitutes the larger element of a two-element gear cluster, the smaller element 34 of which is engaged with the large element 3S of a second two-element gear cluster. The smaller element 36 of this last mentioned gear cluster is engaged with a relatively large gear 37 fixed on the output shaft 26.
Under and in accordance with the present invention, the motor M is so constructed and arranged that an element of the motor frame serves as a closure for the open or rear end of the gear box 21, and this closure element serves as the sole point or source of support for the motor M within the housing section 22, such housing section 22 being connected directly to the gear housing section 21 in a physically separate and independent relationship with respect to the motor M. In attaining such a mounted relationship of the motor M, the motor frame is formed so that it has a forward end wall 40 that is disc-like in form, and this end wall 40 is shouldered as at 4tlS so as to t accurately into a complemental annular shoulder 1468 that is formed in the side wall 21S adjacent to the rear or left-hand end of the side wall as viewed in Fig. 3. Thus, the wall 40 may be secured in place in a closing and sealing relationship with respect to the gear box by means of a pair of cap screws 42 that are extended through thel front wailv 2l? of the gear housing and threaded into the wall 4t) as will be evident in Figs. l, 2 and 3.
Under the present invention, the disc 40 of the motor frame serves as the sole mounting or supporting means for the motor M, and the body of the motor extends rearwardly from the mounting plate or disc Sti in spaced relation to the side walls 22S and the rear end wall 22R of the motor chamber that is formed within the housing section 22. The construction of the motor may, of course, be varied within the purview of the present invention, but
as herein shown, the end plate 40 serves to support the forward end of the rotor shaft 30 through the medium of a self-aligning bearing 45 while at its other or rearward end the shaft 39 is supported by a self-aligning bearing 46 that is mounted in relatively narrow transverse frame bar 48. The frame bar has longitudinal brush support bars 49 extended in perpendicular relation to the bar and from opposite ends of the bar 48, and similar bars Si) are extended from corresponding points on the mounting disc or plate it). These bars 49 and SG have their opposite ends engaged with opposite sides of a field lamination pack 52, and tie rods 53 are extended through the plate 4t), the respective bars Si), and the lamination pack 52, and are threaded into the respective bars 49 so as to hold the frame and field elements of the motor in the desired rigid relationship. The iield coils 55 are extended through the field lamination pack 52 as shown in Fig. 3 of the drawings and are held in place by tie straps 56.
The armature 6i) of the motor M is, of course, mounted on the shaft 36 and has its commutator 61 engaged on opposite sides by brushes 62 that are mounted in suitable brush holders in the bars 59. The armature 66 also carries a conventional fan 63 adjacent the forward end of the armature and in such a position that it is located at substantially the juncture between the housing sections 21 and 22. This fan 63 is arranged to draw air through rear Ventilating slots 63 in the housing section 22 and to discharge this air from lateral discharge slots 69 formed by cutting away portions of the side walls 21S near the rear ends thereof. To aid in directing and controlling the air ow that is thus induced through and about the motor M, a delecting plate 7d formed from sheet-metal is preferably mounted on the motor frame as by clamping integral bails TSB betr. 'een the ends of the bars S0 and the adjacent side of the iield lamination pack 52.
The connections to the brushes 62 are afforded by wires 73 that extend through hollow portions of the handle to a main connecting cord '74, one of these wires being connected through a switch mechanism located within the handle and governed by the switch lever 24. It will be observed that the handle 23 has a removable side cover portion 23R held in place by screws 23S to facilitate mounting and inspection of the switch elements and the related wiring.
The motor M as above described is supported on the gear box 2 by means of the mounting plate 40, and after it has been thus mounted, the rear housing section 22, which carries the handle 23, is put in place in surrounding relationship. When thus located, the forward end of the side wall 22S of the rear housing 22 abut against the opposed rear edges of the gear housing 21, and the parts are held in this relationship by a plurality of cap screws 80 that are extended from the forward ends of clearance grooves SSC and through web portions 80W of the side walls 22S and are threaded into tapped openings in the walls ZiS of the gear housing. Thus the two housing sections are rigidly related to each other.
With the construction of the arrangement that has thus been described, any tendency of the housing or tool body to rotate in a reverse direction when the working tool encounters an undue resistance is transmitted from the handle 23 through the walls 22S of the housing 22 and directly to the gear housing 21, thus to avoid the application of twisting or distorting forces to the motor frame. Because of this relationship, the motor parts and particularly the bearings thereof remain in the proper relationship and undue wear on the bearings is avoided. Through the use of this construction, the life and usefulness of portable electric drills and the like is materially extended, and the manufacture thereof is simplified.
Thus, while i have illustrated and described the preferred embodir'ient of my invention, it is to be understood that this is capable of variation and modification, and I therefore do not wish to be limited to the precise details set forth, but desire to avail myself of such changes and 4 alterations as fall within the purview of the following claims.
l. In a portable drill unit, a sectional housing comprising a forward gear box section including a forward wall, and a hollow rear section having side and rear walls deiining a motor chamber and secured at its forward end to said gear box and having a rigid handle at its rear end, an output shaft journaled in and extending through said forward wall of said gear box-section, gearing in said gear box section, an electric driving motor disposed inr said motor chamber in a spaced and independent relationship with respect to said side and rear wails thereof and including a motor frame having a mounting member disposed adjacent the rear end of said gear box section, said motor including a motor shaft extended through said mounting member and drivingly engaged with said gearing, and means fixing said mounting member to said gear box to support said motor in said spaced relation to said side and rear walls of said rear housing section.
2. ln a portable tool unit, a gear housing section having a front wall and continuous side wall extended therefrom to ailord a generally cup-shaped form and defining an open rear end, a power output shaft journaled in and extending through said front wall, gearing in said gear housing section, an electric motor having a stator including a frame having interconnected end members, a rotor having a rotor shaft, self-aligning bearings mounted in said end members and rotatably supporting opposite ends of said rotor shaft, one of said end members being formed as a closure for and being secured in closing relation to said open rear end of said gear box section, the end of said rotor shaft that is supported in said one end member being drivingly connected to said gearing, and said motor extending a substantial distance from said gear box section in a rearward direction, a handle located adjacent to the other end member, and torque transmitting means rigidly connecting said handle to said gear box section independently of said motor frame.
3. In a portable electrically driven tool unit, a hollow sectional housing having a hollow forward gear box section with a forward wall and side walls delining an open rear end, and a hollow rear section with a rear wall and having a forwardly opening forward end, said rear section being rigidly secured at said forward end to said open rear end of said gear box section, speed reduction gearing in said gear box section and terminating in an output shaft journaled in and extending through said forward wall, an operating motor having a rotor and a stator including a frame having front and rear end frame members, said rotor having a rotor shaft having one end extended through said front end frame member and said motor being disposed within said housing with said one end of said rotor shaft drivingly engaged with said gearing, means rigidly connecting said front frame member to one of said sections adjacent to the connected open ends of said sections to support all other portions of said motor in a free oating, physically spaced and non-connected relation with respect to the interior surfaces of said hollow rear section of said housing, and handle means rigid with said rear housing section.
4. In a portable electric tool unit, an electric motor having a stator affording a motor frame with front and rear end members and a rotor having a rotor shaft journaled at its opposite ends in said end members and having a front end extending through and beyond said front end member, a gear box having a front Wall and a rear end and to which rear end said front end member of said motor frame is rigidly secured so that said motor extends rearwardly from said rear end of said gear box, an output shaft journaled in and extending through said front wall of said gear box and speed reduction gearing in said gear box operatively connecting said rotor shaft and said output shaft, and a rear housing section having a rear wall and side walls extending forwardly from said rear wall to define an open forward end, handle means xed to and rigid with said walls of said rear housing section, said rear housing section being disposed in spaced surrounding and physically independent and non-connected relation with respect to said motor and being rigidly connected to said gear box adjacent to said front end member of said motor to effect transmission of torque between said handle means and said gear box Without twisting of said motor frame.
5. In a portable electric tool unit, an electric motor having a stator affording a motor frame with front and rear end members and a rotor having a rotor shaft, front and rear self-aligning bearings supporting rotor shaft at its opposite ends in said front and rear end members and said rotor shaft having a front end extending through and beyond said front end member, a gear box having a front wall and a rear end and to which rear end said front end member is rigidly secured so that said motor extends rearwardly from said rear end of said gear box, an output shaft journaled in and extending through said front wall of said gear box and speed reduction gearing in said gear box operatively connecting said rotor shaft and said output shaft, and a rear housing section having a rear Wall and side walls extending forwardly from said rear Wall to detine an open forward end, handle means fixed to and rigid with said walls of said rear housing section, said rear housing section being disposed in surrounding and spaced and independent relation to said motor and being rigidly connected to said gear box adjacent to said front end member of said motor to eiect transmission of torque between said handle means and said gear box without twisting of said motor frame.
References Cited in the le of this patent UNITED STATES PATENTS 595,731 Pengnet Dec. 21, 1897 1,424,879 Carlstedt Aug. 8, 1922 1,497,513 Kelley June 10, 1924 1,990,036 Kratz et al. Feb. 5, 1935 2,477,150 Snyder et al July 26, 1949 FOREIGN PATENTS 404,477 Great Britain Jan. 18, 1934 785,053 France May 13, 1935