US 2481499 A
Description (OCR text may contain errors)
3 Sheets-Sheet 1 F. COLLURA BRUSH AND BRUSH HOLDER FOR ELECTRIC DRILLS Filed April 24, 1945 Sept. 13, 1949,
T 7 \NVENTOR 1 fPAA CESCO 604401914 iTToRNx 5 SQQiL 133 19 590 F. @QLLURA BRUSH AND BRUSH HOLDER FOR ELECTRIC DRILLS 5 Sheets-Sheet 2 Filed April 24:, 1945 v M FFWMQWJ ATTO R N E Sept. 13, 1949. F. COLLURA 2,481,499
BilUSH AND BRUSH HOLDER FOR ELECTRIC DRILLS Filed April 24, 1945 3 Sheets-Sheet 3 INVEN o R fzA/vaszrco 0440,64
Patented Sept. 13, 1949 UNITED STATES PATENT OFFICE.
BRUSH AND BRUSH HOLDER FOR ELEETRIC DRIELS Application April 24-, 1945, Serial" No; 590,079
9 Claims. 11
This invention relates to electric drills, orother' tools of a similar character, supplied with ahand grip section in the nature of a pistolv grip, the operators hand controlling the point of application of the drill and the amount oipressureth-ere-L on: and also controllingthe electric power switch sothat the power may be conveniently thrown on and off.
An Object is the provision of an electric hand: tool having a minimum number of casin parts: sothat there are a minimum number of junction lines on the casing, which: lines have the disadvantage of permitting entry of dust ancli other foreign matter, and also tend to. limit the efficiency of the tool by causing: discomfort or injury" to the hand of the operator along the. meeting lines of the casing, particularly at theliand' grip section.
A further object is the provision of a. Commit-'- tator and brush assembly in an electric tool: of. this type which permits ready assembly, removal; and replacement of brushes, provides a. brush subject to a minimum of shearing, Wearing and? breaking strains, provides a. brush having acummutator contact surface which. functions with maximum efficiency and retains such. maximum; efficiency; and provides further a. brush. having an. extended length. so that replacement is necessary only at longer intervals, while at the same. time the outside dimensions: of. the. tool may be. sharply limited and the tool. rendered relatively light and compact.
A further object is the provision of a commutator brush of a special shape which permits maximum eifi-ciency at the commutator contact area, maximum efficiency because of the lengthof the brush and the mass thereof available to take up frictional wear at contact, while at the same time space necessary for the application of such brush in its relation to a. commutator is economi'zed and the feed. of such brush toward the contact area to take upthe effects of contact wear may be readily and: eili'ciently accomplished;
A. further object. is: the provision in. an electric tool of. a device; operating: the: on and off: power" switch,v of a nature such. that. it maybe readily operated by one hand: of the operator so that the.- power' may bereadily. thrown.- orr by a.v finger of the. operators: hand. holding. the tool atthe hand; grip, While at the: same time: the same finger; or a.v second finger of the; operator's: same hand; can; throw into locking.- position a switch. lock: so; that: the power will:. remain on. without; theoperators; pressure: upon: the: switch. This switch lock? may also; be; readily thrown, or: released; to: the u.m-
2. locking position, permitting the switch togo to the power-oftposition so far as the lock isconcerned'.
Other obi'ects of the invention will in part be obvious and will in part appear hereinafter;
The invention accordingly comprises the fear tures of construction, combinations of elements; and arrangement of parts, which will be exemplifled in the constructions: hereinafter setforth, and the scope of the application of which will be indicated in the claims For a fuller understanding of the. nature and objectsof the invention reference should be had tothe following detailed description taken in 0011- nection with the accompanying drawings, in which:
Fig. 1 is a side elevation ofanassembled elec:-- trio drill emb'odyingthis invention;
Fig; 2- isa section on a somewhat enlargedscale on the lines 2-2 of Fig; i looking in thedirectiom orthe arrows,
Fig: 3 is a: section on the lines 3--3 of Fig; 2 looking inthe direction ofthe arrows, this View" being on substantially thesame scale as Fig; 1 and showing detailthebrush carrying unit as it isin position within the drill:
Fig. 4 is a; detailshowing the en-d'cfthis brush carrying unit as it is being partly removed from the casing thereby permittingthe operation of a brake which holds the brush inposition within the brush carrying unit While it is being removed from the-casing'a-nd thereafter:
Fig; 5 is a section taken on the line 5-5 of V Fig, Zbut drawn to the scale of Fig. 1;
1 the off. or no.-power position;
Fig. 9 is a sectionaldetail of one. of. the brush. carrying units;
Fig. 104s adetail. showing. the relation between, brush. aha-commutator with, an indication of the a passage of tangential line'sof; force, causedlby the contact between. the rotating. commutator anda the: brush,, through the: mass of the brush;
Fig; 1 1'. is a detail section showing azmodifiedr form: of triggen'lock;
Figs 12*: is; a detail; showing. the; parts; of Fig. 1];
3 in section and in the unlocked position, on the lines |2-l2 of Fig. 11;
Fig. 13 is a section looking in the direction of the arrows showing this form of trigger lock in looking position;
Fig. 14 is a sectional detail showing a trigger lock such as that shown in Fig. 11 but with a spring tending to hold this look in non-locking position;
Fig. 15 is a section on the lines 15-45 of Fig. 14 looking in the direction of the arrows; and
Fig. 16 is a side elevation of one of the brush carrying units showing the brush as it is inserted in the holder ready to be moved in the holder to its operative position.
In the drawings, Fig. 1 shows a drill assembled in accordance with my invention which comprises a main body section A having a central casing member I and a pistol grip member 2 integrally connected therewith and forming part of a single casting which may be readily constructed of metal or aluminum. An end section B of the casing is connected to the section A by the interposition of section C, provided with ventilating passages 3 leading to the interior of the tool. A drill chuck 4, broken away in its length for convenience of illustration, projects from the end of the casing section B.
A further casing section D is shown below the hand grip section I of the main casing and fitted thereto to complete the outside form of the tool. A switch trigger 5 and a projecting part of a lock therefor at 6 are shown. At 1 is shown the outer surface of a brush carrying unit fitted to an opening in the casing. A similar brush carrying unit 8 is indicated by dotted lines as provided on the opposite face of the tool casing.
Referring now to Fig. 5 there is shown an electric motor having a conventional armature 9, field magnet I0 and windings therefor. This armature carries a. central operating shaft [I journaled at 12 in casing A and I3 in casing C, and carrying at its outer end a pinion M which operates pinion IS on a stud shaft I6 carrying at its end a pinion l1 meshing with the pinion l8 on the I brushes which constitute an important feature of this invention. Referring first to Fig. 6, an upper brush assembly unit is indicated at 8, removably held in position in the upper part of the tool casing by a screw 22 and carrying are shaped brush 23, indicated as of usual carbon material, held within metallic holder 24 and having a contact area at 25 bearing upon the commutator bars 26 and fed forward as it is worn away at the contact area by spring pressure of the arm 2! bearing against the end of the brush, this arm being the extended end of a coil spiral spring 28 suitably mounted upon stud 29 carried by the body of the unit 8.
The brush holder 24 has two parts, in addition to its main frame work, a back plate 24a, shown most clearly on Figs. 3, 9 and 16, and a front plate 24b which is cut away in part as shown on Fig. 16 to provide an open faced slot within which one end of the are shaped brush may be inserted from the side when the drill is in process of assembly or when it is necessary to install a fresh brush. This makes it possible to use a comparatively long are shaped brush, providing a greater mass of material which will accordingly have a longer life and require less frequent replacement. As shown in Fig. 16, the brush is dropped into the open faced slot and then moved in an anti-clockwise direction, carrying the spring arm 27 with it and winding up the coil spring, until it reaches the position shown at Fig. 2 when it is ready for use. If it were not for the provision of this holder thus formed with one section cut away so as to permit placing of the brush in the position shown in Fig. 16, it would be possible to use only a comparatively short are brush to the extent of the distance between the points marked a: and :c on Fig. 16. It is found that with the construction as shown a brush may be used well over the arc in length and up to a point of 270 and beyond in length. The 270 length of the arc is found quite serviceable and useful. As shown on Figs. 2 and 6 the long are shaped brush there illustrated is of a length such that while one end bears at its contact area upon the commutator the other end approaches, as shown, the commutator at a point along the circumference, and a relatively long brush is thereby provided limited only by the practical length of a brush having one end at the contact area bearing upon the commutator and the other end sufficiently spaced from the commutator so that the spring arm 21 may be interposed as shown in Figs. 2 and 6. It will thus be seen that the are shaped brush is struck upon a circle, the center of which, when the brush is installed, is outside the peripheral circumference of the commutator. The brush thus has a contact area at one end extending radially across it While the mass of the brush extends away from said contact area along an are shaped line which may be extended so far as desired up the point where further extension would bring its farther end, and the feed spring bearing against it, too close to the commutator. It will accordingly be seen that, while in some other relations the are shaped brush such as is shown would have a useful function, independently of the construction of its holder, in the present relation, as shown, the shape of the brush is of special importance and the shape of the holder providing the cut away portion for assembly of the brush is also of special utility.
A similar brush unit 1 is shown in Fig. 6 below the commutator removably held in place by screw 30 and carrying a brush, brush holder, and controlling spring therefor in all respects the same as that already described for the upper brush.
This brush makes possible the use of a relatively large mass of brush material, rendering replacements much less frequent, while at the same time relatively small space is occupied by the brush and a smaller, more compact tool is secured. In addition, the major tangential lines of force caused by the friction between the brush and the oncoming rotary armature will as is indicated in Fig. 10 at 3|, pass through the body of the brush in the line of its path of movement rather than across such line of movement as in brushes now in common use. This tends to lessen the uneven wearing away of the brush at the line of contact with the commutator and thereby to a marked extent increases the efficiency of the brush and lengthens its useful life. At the same time the wearing and shearing action between the brush and its holder are reduced to a minimum and particularly there is no excessive shearing action between the brush and the holder at the end of the holder where the brush is forced against this end in a construction 5: new widely used: in, the. art; With. this; type; OI? brush: also all: ofv these: conditions. remain. sub.-
stantially. constant throu hout. the: life on; the:
vented; come in contact with the. armature: and;
damage would be caused. thereby;v Ii, provide a. stop: in the. nature of a lug; 32; struck up: from the inner side of: the brush: holder 24; in. aposition. such that. the spring; arm. will,. at the appropriatetime toward the end of its. trayeli be: caughtby this lug and be held: as against-inn ther' advances.
A form of electric tool in generalt use embodies. a straight brush with. a; spiral spring bearing again-st the end of such brush and: feeding it. forward to contact with. the commutator- This involves a shearing, breaking and crumbling ei. fectupon the lowerend of the brush. asalready described but it also involves. an: irregular erosiorr of the brush at the contact area.- caused? by the fact that the feeding forward of? the spring is necessarily uneven and: the pressure of the brush on the commutator at the contact area accordingly uneven. With: the present construc tion, however, the spring pressure of" the arm-.- 21! upon the end of" the arc shaped brush is an even pressure exerted evenly; through the mass. of" the brush and: as a result. the erosive action at the contact area is. substantially even and: the brush wears away evenly and. with. maximum. efficiency.
With the brush assembly unit described; having a. spring pressure behind the brushv tendin to. force it out. of." its container. the brush. would: be forced out by spring action as 7 911311115111 as? sembly unit is being removed: from. the casing:
and contact,v of brush. and commutator broken; To prevent this there is provided. as; shown; in. Figs. 2, 3 and 4 a brake, inactive: when; the; brush, assembly unit is, in position within the; casingand brought into; action; as the; brush. assembl unit is removed from the casing.
As shown, this brake; is in-I the forms, of a lever 56.- pivoted; on, stud 51; carried, by the; brush. as sembly unit and formed at one. end at 5.8 to pass down through opening 59 in the containertrame; so that it: may bear upon the; side; of; the brush 23. Sprin 6% bearing upon. the. other end 015 this brake lever tends normally to force it to.
braking; position. This brake lever is provided; at its. other endat 6!. with an inclined surface bearing upon the inclined projection 62 on; the: inner face of the. casing section. It: will thus: be seen that when the brush assembly unit, is; in position within the casing the brake; lever will be; held to the inactive position. against the force of spring 58 as shown in Fig. 3, and that the; brush. may be freely fed forward in use. As how.- ever the brush assembly unit is being removed from the casing the end of thebrake lever passes away from the projection 62 and: as shownin Fig. 4, spring 60 forces up the one end of the brake lever and the other braking and is; then brought into action against the brush. to. hold it in position within the container and prevent its being forced out by the action of the, spring arm 21.
We come now to the switch for turning on andoffthe-power inv the use; of the tool. The under side of the hand grip section of the tool is closed by casing. section D... shown. as. ribbed to ra ns ev r: orrth sw tchiriggen mthiscas the 6 limit. slipping ot the hand.. This section of the casing; carries a tube 33 through which passes the electric lead wires t4.- and 35; with contact posts; 36? and; 31. In; Fig. 5 switch lever 38- piv-. oted. at 39; and carrying an extended contact arm 40 is; shown. as; only in contact with the postv 36 and, power supply. to the tool is accordin ly'bmken; This. condition isnormally maintained by action of; the spring 1:! acting against the; pivoted lever 38; to hold the parts in: the; po-
sition: shown: in Fig. 5; When this lever 38 is turned; on its; pivot in. a clockwise direction, its arm; 40. will bridge the two. contacts. and power-- will? besupplied to the tool. Leads of the circuit. through, the motor and back are all such as; conventionally used in the art and are not, shown, in: detail; Posts. 56 and 51- as shown in Fig. 5; and at, the upper end, of' Fig- 8., supply connections for the ends of lead wire 58; and 59 connected in. conventional mannerfor driving the chuck rotating; motor. Soiar as this invention. is concerned; it is only necessary that; there be means for, switching on and ofi the; power under the: control of; a. spring-pressed switch; to; be operated; by the trigger and trigger the. trigger 5; forward or to. the left. When it.
is. desired to. use the tool; the operator with his: hand on the hand grip section by the use of, for example. hisv second finger, presses in the trigger 5 against; the force of the spring. This completes the circuit and the tool is rotated through. the connection described.
If it is desired to maintain the tool in. operationwithout the necessity of continued finger pressureupon the trigger member 5, the operator, as. by-theuse of the first finger of his hand, or by the slight upward. movement of the same finger which is pressing upon trigger member 5, can: press. up. the pivoted detent lever 6: shown in- Figs. 5 and 7.; This lever is carried by the screw 45, tapped? into the under face of the frame section I, and rocks up and down uponthe spherical inner face 46' of the screw head as shown. Spring 41 tendstothrow this detent into the inactive position shown in Fig. 5. When the trigger i'sheld back by the finger of the operator into. the power supply position as shown in Fig. '7 and the detent is pushed up against the action of the spring il by the same or another finger of'the same hand of the operator, the inner end of the detent slightly incline-das at 48 is-brought to. position against the edge d3 of. the cut out in the trigger 51 also slightly inclined. and the parts will behcldin that position until. the operator releases the loci; by again pressing in slightly. on the trigger so. that the trigger lock may automaticallyresume, the; position shown in- Fig. 5.
It; will thus be,- scen that there is provided: an. of? and onswitch. which may be readily operated byrt he finger; one hand and at: the sametime be; locked positio so long as desired by the slight movement of the; same; or another fingerof the same hand or the operator and this. lock a in; ased: wh n. sir d.
In. E s to- 1: 5.- is; shown. another form of lock:
locking lever 50 is shown mounted for simple horizontal pivoting movement about the screw 51 tapped into the frame. This lever when in its intermediate position as shown in Fig. 12 has no effect upon the switch trigger. When, however, the switch trigger is retracted to the position shown in Fig. 13 the operator by turning, with his finger, the locking lever 50 in either direction may lock it against either one of the faces 52 of the end cut out on the top of the switch trigger.
Figs. 14 and 15 show a detent lock same as that shown in Figs. 11, 12 and 13 but there is also provided a leaf spring 53 seated at one end in the frame at 54 normally tending to hold the locking lever in its central non-active position. In this case the lever is thrown to the locking position by the finger of the operator against the force of this spring, which will without action of the operator return the lock to negative position when the switch trigger is retracted.
The efiiciency of the outside assembly form of the casing construction as shown in Figs. 1 and has been sufficiently referred to.
Thi construction, however, has a further advantage in the form and arrangement of casing sections in that it permits a ready insertion of interior working units followed by completion of casing assembly and an equally ready removal of the parts for repair, replacement or any other purpose. Referring on this point to Fig. 5, it will be seen that the interior motor assembly in the main section of the casing can be inserted as a unit, thereafter the two brush units put in place, the connecting section C of the frame added, and the casing section B and the chuck driv parts carried thereby added as a unit. Thereupon, the assembly is completed by positiom'ng the lower hand grip section D shown in Fig. 8 in position such that the leads 58 and 59 can be readily connected to their screw contact posts and thereupon this section carried up to the position shown in Fig. 5 and held there by screw 55.
The entire tool may be thus assembled or disassembled with a minimum of effort and when assembled it shows marked efliciency in operation and limited likelihood of breakdown in use.
Since certain changes may be made in the above construction and different embodiments of the invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.
It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention which as a matter of language might be said to fall therebetween.
Having described my invention, what I claim as new and desire to secure by Letters Patent is:
1. In an electric tool a brush adapted to bear at its end upon a commutator and extended from said bearing content along a circular arc and at its farther end approaching the commutator at a point along the circumference thereof from said bearin contact area, and a coil spring having an arm extended therefrom bearing against the farther end of the brush to impose a spring pressure upon the are shaped brush to feed it to the armature contact area as it is worn.
2. In an electric tool a brush adapted to hear at its end upon a commutator and extended from said bearing contact along a circular arc and at its farther end approaching the commutator at a point along the circumference thereof from said bearing contact area, and a coil spring having an arm extended therefrom bearing against the farther end of the brush to impose a continuous and even spring pressure upon the are shaped brush to feed it to the armature contact area as it is worn, a stop for said spring, in position, at the end of its feeding'stroke, to prevent contact thereof with the commutator.
3. In an electric drill, a brush assembly unit comprising an are shaped holder, an arc shaped brush carried thereby, spring means acting to feed said brush from said holder and a springpressed brake operating through an opening in said brush holder upon the brush to retain it within the holder.
4. In an electric tool a brush assembly unit, comprising an are shaped holder, an are shaped brush carried thereby, a spring tending to feed said brush through the said holder, a springpressed brake operating through an opening in said brush holder upon the brush at a point adja-' cent its contact area end, and means for holding said brake out of action when the brush assembly unit is in operative position within the tool.
5. In a brush assembly unit, a holder, are shaped for the reception of an are shaped brush, a portion of said holder being cut away to permit the insertion of one end of the arc shaped brush within such cut away portion.
6. In a brush assembl unit, an arc shaped brush holder, an arc shaped brush, the material of said holder being cut away at one side to provide an opening such that the end of the brush may be inserted in said opening from the side.
7. In a brush assembly unit, an are shaped brush, an are shaped brush holder, said brush having a contact area at one end therefor, a
, spring bearing upon the other end of said brush to feed it to the commutator, a section of the holder being cut away so that the brush can be inserted from the side and the brush then moved, carrying the spring with it and putting tension upon the spring until the brush is in position for use.
8. In a brush assembly unit, an are shaped brush, an are shaped brush holder, saidbrushhaving a contact area at one end therefor, a spring bearing upon the other end of said brush to feed it to the commutator, a section of the holder being cut away so that the brush can be inserted from the side and the brush then moved, carrying the spring with it and putting tension upon the spring until the brush is in position for use, and a brake adapted to bear against said brush to hold it in position within the commutator as against the pressure of said spring.
9. In a brush assembly unit, an arc shaped brush, an arc shaped brush holder, said brush having a contact area at one end therefor, a spring bearing upon the other end of said brush to feed it to the commutator, a section of the holder being cut away so that the brush can be inserted from the side and the brush then moved, carrying the spring with it and putting tension upon the spring until the brush is in position for use, and a spring-pressed brake adapted to bear against said brush to hold it in position within the commutator as against the pressure of said spring.
(References on following page) um er REFERENCES CITED 2,277,572 The following references are of record in the 2,349,401 file of this patent: 2,373,842 5 2,389,941 UNITED STATES PATENTS 2,399,935 Number Name Date 731,740 Bassett June 23, 1903 2,029,171 Lundquist Jan. 28, 1936 Number 2,234,695 Hanna Mar. 1 19 1 10 269,203
Name Date Weissinger Mar. 24, 1942 Beckwith May 23, 1944 Mitchell Apr. 1'7, 1945 Stephenson Nov. 27, 1945 Merrill May '7, 1946 FOREIGN PATENTS Country Date Italy Nov. 13, 1929