US 2840673 A
Description (OCR text may contain errors)
June 24, 195v8 E. F. BURTON FLEXIBLE lSHAFT POWER TOOL FiledA Nov. 2, 1953 1N V EN TOR. bu/Ae 52,270#
BY Arroz/wwf- United States Patent O This invention relates to flexible shaft power tools such as drilling, grinding, and erasing machines and is directed primarily to improving and simplying the control means for the electrical power drive and making such machines safer and more convenient to operate.
Flexible shaft power tools presently available consist generally of an electric motor mounted on a suitable support, a flexible shaft and casing means attached to the motor, and a power head carried by the outer, or free, end of the flexible casing means, together with a control switch mounted directly on the motor, or remotely located on the floor for foot operation, with a conductor means extending to the motor.
The rst type is particularly inconvenient for the ilexible shaft is normally three feet or more in length and it is diflicult if not impossible to operate the switch while hol-ding the power head in working position. When working with a cutting or abraiding tool mounted in the power head it is desirable more often than not to locate the tool in position before setting it in motion. This purpose is obviously defeated if the switch is too far away to reach with the operators free hand.
The vsecond type is used in professional work where the operator uses the tool enough to develop the proper coordination between hand and foot but it is not particularly desirable for amateur use because of the necessity for special coordination. Moreover, foot operated switches are subject to considerable damage while lying on the floor and must be moved from place to place as the operator changes his position. In addition, the cord leading from the switch to the motor is frequently in the way and is also subject to damage.
The present invention eliminates all of the objections to the previous types and provides a simpler, safer, and more convenient means for controlling the motor. It is particularly desirable for amateur use because of its natural feel, the operator using the same hand to guide the tool and to control the application of power thereto.
Essentially the present improvement consists in providing an elongate flexible electrical conductor means which is operatively connected to the power circuit of the driver motor, the conductor means extending along the length of the flexible casing and preferably wrapped therearound and secured thereto, and mounting an electric switch directly on the power head of the tool, with the conductor means connected to the switch so that the operator, while holding the power head in one hand, may operate the switch with a finger, thus enabling him to locate the tool exactly in the desired position and then, without moving the tool or his hand, set the tool in operation.
The presently preferred embodiments of the invention are illustrated in the accompanying drawing, in which:
Figure l is a general elevational view, with a portion broken away, of a flexible shaft power tool embodying the simplest form of the invention;
Figure 2 is a longitudinal sectional view of the power head of the tool shown in Figure l;
Figure3 is a sectional view taken on line 3-3 of Figure l;
Figure 4 is an exploded view in perspective of the adjacent end fittings of the power head and flexible shaft and casing assembly of a modified form of the invention incorporating a built-in wiring system;
Figure 5 is a similar view of the adjacent end fittings of the flexible shaft and casing assembly and the motor;
Figure 6 is a sectional view taken on line 6-6 of Figure 4;
Figure 7 is a perspective view of a modified power head with portions broken away to show a modification of the control switch; and
Figure 8 is a sectional view taken on line 8-8 of Figure 7.
As generally illustrated in Figures l and 2, the power tool includes an electric motor 10, a flexible shaft 12 and flexible casing 14 connected thereto, and a power head 16 carried by the outer, or free, end of the casing. The power circuit within the motor housing is connected to an outside source of power by conductor 11.
The power head 16 includes an external shell 18, bushings 20 and 21, a rotatable shaft 22 carried thereby, and bushing retainer 24 secured to the shell. The shaft is provided with a bore 26 thruout the major portion of its length to receive an eraser stick 28 which is held in adjusted position by chuck 30, attached to the open end of the hollow shaft and provided with a chuck ring 32. The rightward end of the shaft, as viewed in Figure 2 is provided with a squared hole 34 to receive the squared end 36 of the flexible shaft 12 to be driven thereby, and the assembly is held together by collar 38 screwed onto bushing retainer 24, the flange 39 of the collar engaging the flange 40 on the end of the flexible casing 14.
A casing member 42 is mounted on the power head and provides protection for the snap acting electric switch 44 located therein. The control member 45 extends a slight distance outward of the casing to provide access for finger operation. Elongate, flexible electrical conductor means 46 extend along the length of the flexible casing and are connected operatively at their inner ends to the power circuit of the motor. They may be connected directly in series with the circuit or may lead to a relay to cause operation of the circuit. At their outer ends they are connected to the terminals 47 and 48 of the switch 44.
It will now be seen that when the operator is ready to use the device he may grasp the power head in one hand, place the cutting or abrading tool in operativo position, and then with his fingers depress control member 45 with his finger to actuate motor 10. He may do this with ease regardless of the length of shaft and casing assembly 14.
While the conductor means may extend substantially directly parallel to the casing it has been found desirable, in order to avoid any reduction of the flexibility of the casing, to wrap the conductor means helically around the casing with a pitch of at least one full turn per foot of length of the casing. ln either form the conductor means may be held in place by one or more collars or clips 50. Figure 3 shows how the conductor means lies closely adjacent the surface of the casing.
Figures 4 to 8 illustrate a modification of the invention in which the wiring is, in effect, built-in, In Figure 4 the power head end fitting 52 carries a driven shaft 54 provided with a bore 55 having a keyway 56. The adjacent end fitting 58 of the flexible casing carries a driving shaft 60 provided with a boss 61 having a key 62 for engagement with the driven shaft. Fitting 58 carries electrical plugs 64 to which the conductor means 65 are connected and fitting 52 carries receptacles 66 toreceiveplugs v64.- shown, extend from receptacles 66 to the switch on the ppwer head., Collar 68 screwson to fittingA 52 to hold the ttingsirr assembled relations- 'Pin' 69 on-tting352 engages socket 70 in fitting 58 tionandtorelieVe they electrical connections ofshear andiotherrloads; 1
In'Figure 5, the fitting 72 carries drivenlshaftf7ffi=ratvk the inner end of the-ilexible/'shaft and casing-assembly. The Yshaftis provided with-non-circular bore 75; Fitting 7.6 on themotor housing-carries driving shaft 77 with a non-circularend portion 78-to engage bore 75. Receptacles 79 inriitting 72 are connected with conducto'rmeans` 65f while/plug means-8tl-are^connected Vto a conductor, notshown, whichI extendsinto the motor-housing for operative connection to the power circuit asV described above withv referenceV to the` modification of Figures 1 and 2. Pin 81 and socket 82 perform the same functionY asipin 691and socket 70 inwFigure 4. The collar- 84 screws onto fitting 76` to holdthefittings in assembledrelation.
Asbestseen` in Figure 6, thel flexible sheath 86 envelops the iiexible casi11g87 and the conductor means 65 and holds tbemin assembled relation while permitting the necessary flexing which occurs during use of the tool. It alsoV provides protection againstY dirt and abrasion. The sheath Vmay be mechanically laid-over'the assembly orgtheconductor means may be molded-into its asindicated in Figure 6.
To complete theV enclosure of the electrical4 system theswitch mechanism may be modified as shown in Figures'7 and 8, in Whichra rigid casing-member 88 surrounds the power head 90, its upperV porting being enlarged to -receivethe switch 92 which is generally similar, to the switchi of the-first modification. An opening `941 is provided inthe upper, or radially outer, portion ofthe casing member andthe control member-96 ofthe switch is located in said opening and substantially flush with the contour ofthe casing member so that it may be depressed to close the circuit.
A sheath 98 of elastically deformable material, such as rubber, enclosesthe entire casing member and covers thev opening 9 4 to exclude all foreign matter fromthe switchV mechanism. It thus protects the switch also from the mechanical damage and prevents inadvertent operato prevent relative Yrota- Y asaogefa Further conductormeans; not-- tions Sinceu it is elastic, itmayV be` deformed` under` finger pressure so that the control member may be depressed to actuate the motor.
While the preferred embodiments of the invention have been illustrated in the drawing and described above, it will be apparent to those skilled in the art that various changes and modiiicationsmay be made Without departing from the spirit yof the invention, and it is intended that all such changes'and modifications shall be embraced within the scope of the-following claims.
1. Controlmeansfor an` electric y-power'tool having a power head, comprising: a rigid casing'v mounted on said power head and provided with an opening in its Iradially outer side; an electric switch mounted within said casing and having a depressible control member extending, in
Y non-operating condition, into said opening and beingsubstantially flushwith the-contour of said casing; and an elastically` deformable shield extending over said-openingto exclude foreignmatter and to prevent inadvertent` operation of said-switch, the shieldbeing deformablel under iin-gerpressure to providevfor depressionofsaid-A control member.
2; Control means as claimed'in claim 1, in which saidshleldY sr an elastically deformable sheath surrounding-y said power head an'dsaidcasing.
References Cited in the tilev of this patent UNITED STATES PATENTS` Great Britain Jan. 8,