Patent Publication Number: US-4319403-A

Title: Power drill position indicator

Description:
BACKGROUND OF THE INVENTION 
     The present invention concerns an indicator device for providing a visual signal to a tool operator to assure the tool operating axis is perpendicular to the surface of a work piece. 
     In certain types of fabrication work it is desirable that pilot holes for fasteners be formed truly perpendicular or normal through the pieces being joined. Pilot holes inclined to a desired axis incur wasted man hours spent trying to remedy same by re-drilling the work pieces or beveling a shim. Installation of a metal fastener other than in normal disposition to the joined pieces may impart asymetrical loads to the fastener causing premature failure of same. 
     The problem of boring pilot holes normal to a work piece surface is entirely distinct from boring pilot holes along vertical or horizontal axes. In the prior art are gravity responsive drill attachments such as shown in U.S. Pat. Nos. 4,141,151 and 4,189,726. A pilot bore drilled with such an aid would be perpendicular to the work piece surface only if the surface is truly vertical or horizontal which is seldom the case in certain types of fabrication, e.g., airframe. 
     SUMMARY OF THE PRESENT INVENTION 
     The present invention is embodied in a device for indicating to a power tool operator the relationship of the tool&#39;s operating axis to an optimum axis perpendicular to the work pieces regardless of whatever position or attitude the work piece or pieces may be in. 
     The instant device is for use in conjunction with a power tool such as a hand held drill. A foot member of the device is adapted to restingly abut the surface being drilled. Electrical contacts are concentrically disposed so as to come into foot engagement upon the drill moving out of the optimum perpendicular axis. Indicator signal means indicate to the operator which direction the drill must be repositioned to return to the perpendicular. The foot member and its carrier are axially retractable during drilling to provide guidance throughout initial drilling after which the course of the bit is automatically controlled by the bore formed. The indicator signal means are positionable so as to be easily viewed by the operator at various drill locations. 
     Important objects of the present invention include the provision of a device for use with a power tool having an operating axis at all times desirably perpendicular to the surface of the work piece or pieces being drilled, said device providing to the tool operator a signal when the tool is out of perpendicular and further, what direction the tool must be moved to restore coincidence of the tool operating axis and a desired perpendicular axis; the provision of a device for use by those boring pilot holes in inclined, horizontal or vertical work pieces where it is important that the hole so formed is on an axis normal to work piece surfaces; the provision of a device readily attachable to a power drill with check means provided to assure the work piece engaging foot member of the device is in parallel offset relationship with the tool operating axis. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     In the drawing: 
     FIG. 1 is a side elevational view of a power drill with the present device thereon; 
     FIG. 2 is a side elevational view of the present device sectioned for purposes of illustration and shown approximately full scale; 
     FIG. 3 is a vertical sectional enlarged view taken along line 3--3 of FIG. 2; 
     FIG. 4 is a wiring schematic; 
     FIG. 5 is a side elevational view of a chuck mountable aid used for aligning the axis of the present device with the tool operating axis; and 
     FIG. 6 is an elevational view on a reduced scale of signal means of the device taken along line 6--6 of FIG. 2. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     With continuing attention to the drawing, the reference numeral 1 indicates generally a hand held power tool shown as an electric drill typically including a chuck 2 within which is received a drill bit 3. The drill includes a finger actuated control 4 which opens and closes associated switch contacts in circuit with an electrical power supply via a cord 5. While a typical power drill is illustrated, it is to be understood that the present device is compatible with power drills of different configuration as well as other drilling or boring devices. 
     An elongate housing at 10 of the present device is secured in place on a drill motor housing at 6 by mounting means at 11 shown as metal straps of the type incorporating tensioning means. Depending upon the configuration of the motor housing 6, elongate housing 10 may be supported in a manner utilizing shims or the like to assure the major axis Y of housing 10 is parallel to the operating axis X of the power drill. While housing 10 is shown as being cylindrical, that portion abutting drill motor housing 6 may be otherwise configured to enhance secure placement on the motor housing. A rearward end segment 10A of the elongate housing is bifurcated at 19 to support signal means 12 pivotally coupled thereto by a fastener 13 which permits positioning of the signal means for optimum viewing by the drill operator. As shown in FIG. 6, the signal means is provided with lamps which may be light emitting diodes termed LED&#39;s at 14, 15, 16 and 17. Additionally, the signal means serves to conventionally mount an OFF-ON control switch 18 in electrical circuit with said diodes and a power source. 
     The elongate housing of the present device is segmented at 20 to facilitate deposit of a power source such as dry cell batteries at B arranged in series. A ground at 21 is carried by a yieldably mounted support 22 the latter spring biased into battery engagement by a helical spring 23. Shown also in FIG. 2 is a disk-like terminal 24 contacted by the forwardmost battery. A support 25 is fixed within the tubular housing. Terminal 24 is in electrical contact with housing 10. 
     Indicated generally at 27 is inclination sensing means including a tubular carrier 28 having a spherical forward end 30 shaped to provide a ball socket. Said carrier is adapted for telescopic movement relative the forward end segment 10B of housing 10 with such movement being limited by a stop 31 coacting with a recessed flat area 28A formed on the carrier. A foot member includes a foot 33 with a work piece abutting surface 33A and integral with a spherical component 34, the latter universally supported in the ball socket end 30 of the carrier. Integral with spherical component 34 is an arm 36 which is substantially coterminous with the inner end 32 of carrier 28. As shown in the sectional view of FIG. 3, the inner end of arm 36 is proximate a circular array of electrical contacts 37, 38, 39, 40 in place within a ring 35 of insulative material. Ring 35 and the contacts are held in place within the carrier inner end by a suitable adhesive. In a suitable embodiment of the invention, arm 36 when concentrically disposed within ring 35 (as shown in FIG. 3) has a contact clearance of approximately one-sixteenth of an inch. From the foregoing, it will be seen that upon foot surface 33A being in surfacial abutment with a work piece surface at S, any inclination of housing 10 (and hence carrier 28 therein) from the perpendicular position shown in FIG. 1 will result in the inner end of arm 36 contacting at least one of the contacts 37 through 40. 
     Biasing tubular carrier 28 outwardly in a forward direction is a helical spring 48 acting on carrier mounted contact supporting ring 35. A fixed spring end is retained by stationary support 25. 
     In the wiring schematic of FIG. 4, current from the batteries B is applied to arm 36 with metal housing 10 and carrier 28 serving as conductors. Relative axial displacement between arm 36 and carrier 28 will result in arm 36 closing with and imparting current flow to a contact 37, 38, 39 or 40 or to two adjacent contacts to cause illumination of a diode 14, 15, 16 or 17 (or two adjacent diodes) via leads 41, 42, 43 or 44 in circuit respectively with the diodes. A resistor at 45 and OFF-ON control switch at 18 in a ground conductor 47 complete the circuit back to the ground size of batteries B. Leads 41-44 are bundles for convenient lengthwise passage through housing 10. 
     In the preferred embodiment of the invention above described arm 36 will close with a contact 37-40 upon housing axis Y (and tool operative axis X) being displaced through five degrees or less about a center Z of spherical component 34. With contacts 37-40 in circuit with diodes 14-17 as shown, diode 14 will illuminate to indicate operative axis X of the drill is above optimum axis, illumination of diode 15 indicates axis X of the drill is to the right of the optimum axis, etc., with corrective repositioning of the drill indicated by the diode(s) going out. 
     For purposes of installation of the present indicator on a power tool and periodic checking of parallel alignment to the tool operative axis, an aid is shown in FIG. 5 including a spindle 50 for chuck installation. A plate 51 is normal to the spindle axis and serves to surfacially receive foot member 33. Elongate housing 10 is then positioned on the power tool and secured in place with attention to assuring the diodes remain unlit to thereby indicate parallel alignment with indicator axis Y and tool operating axis X. 
     While the indicator disclosed as being separable from the power tool, it is to be understood that the indicator may be a part of or permanently secured to the tool and that a power source for the indicator may utilize a common power source with the tool. 
     While I have shown but a few embodiments of the invention it will be apparent to those skilled in the art that the invention may be embodied still otherwise without departing from the spirit and scope of the invention. 
     Having thus described the invention, what is desired to be secured under a Letters Patent is: