US2354307A - Motor-driven hand tool - Google Patents

Description

Jul 25, 1944.

w. M. EM ERY MOTOR DRIVEN HAND TOOL Filed Nov 25, 1942 2 Sheets-Sheet 1' Fl G. l

FIG-.2.

VENTOR.

July 2 w. M. EMERY I 2,354,307

MOTOR DRIVEN HAND TOOL Filed Nov. 25, 1942 2 Sheets-Sheet 2 Patented July 25, 194 4 William M. Emer Shaker Heights, Ohio, assignor to The Rotor Tool Company, a corporation of Ohio . Application November 23,1942." Serial N o. 46(i,60 1

. My invention refers to improvements in power driven handtools with special attention to grinders, nut setters, drills,'.and' the like where the tools are of such horsepower that they develop substantial reactive torque which must be resisted by the operator. This includes such tools that for'efficient. or convenient operation and :usually for support, the handle is'positioned substantially axially or parallel thereto. "I'hisinvention bears some similarity infield and objects to that covered in my Patent many classes of applications,.-has certain limitations which are overcome in my present inven-, "tion, principally by avoiding clo'se indexing between the forearm of the operator and the wheel guard and allowing for varying-the angle between 'th guard and the work by the flexing of-the wrist.

With grinders, a limit has been found above 'which in the past it has'been ineflicient to increase the horsepower and the torque because of the inability of'the operator to resist the reactive torque by gripping the straight or axial handles without excessive fatigue. Infact, the

majority of the fatigue in the-use of suchtools is'directly tra'ceable'to finger, hand and wrist fatigue, so much so that in continuous operation theoperator seldom presses sufliciently upon the.

workto'utilize the full horsepower capacity of the tool or to secure maximum removal from the work'being ground. The work accomplished is further reduced by necessary rest periods.

Furthermore, if the wheel grabs'while grinding the inside'radius of a hole the operator is often unable to hold the tool and frequently suffers injury. 7 Y

Some years ago spade handles were used on such tools. A spade handle consists ofa handle like that of a'spade. It has a hand contacting portion substantially perpendicular to and across last five years whichsuch' ha'ndles have been used with large'tools, no method hasbeen advancedby any other that successfully overcomes the fatigueproblem'that so limits .the produotionand horsepowertorque capacity of this v type tool. My'previous il' ivjerition bylo'nger le- #2,301,264, to which reference will be made. My previous invention, although very helpful with verage places'the reactive torque largely midway on'the forearm o'f'the operator. In my present invention the reactive "torque'i's' applied through .my torque arrestor lever to the lowest point of the forearm namely the. bony structures of the forearm which in part constitutes the'w'rist j oint'and the heel of the hand adjacentthereto, although 'I do not so limitthe sphereof' my invention. More specifically, the 're'activ'e torque 'presses'my torque arrestor lever against thehypothenar emithe handle'is normally-grasped; The conventional straight handles when'normally grasped cross the palm of the hand distal (that is away from relative to the-body) to'both the thenar (that is the thumb) eminence and the hypoth- 'enar eminence. Thus my torque @arrestor' lever substantially'doubles the lever-arm as compared .to. conventional axial handles resisting the re- "active torque. "Thisw'ould of course reduce the friction grip required to'hold'thehandle-50%, if

5* the handle were substantially round. r

My invention'goesstill further try-providing an irregular shape which'willhot turn easily in the hand, so thatthe hand need gn'o't be gripped so tightly and the blood maycirculate'freely through the fingers. Also much of the wriststrain'and '1 fatigue is eliminated, because-theleverage-at the wristis reduced-to-a minimum by applying the pressure from the reactive torque to the'hypoth enar eminence adjacent to the wrist. There is no muscular-pad more-adequateand adjacent to the wristfto receive this reactive torque thrust, 1.40

the axis of the tool and-connected to the tool by rigid bales integral 'to each" end of the handle.

"They have been largely abandoned after many T hands, especially thumbs, were injured when the wheel grabbed. The spade handle provided insufiicient leverage to resist the stalling 'load 'of the motor and when this occurred the operator was often 'unable 'to disengage his hand before injury."

T The so-called straight of axial "handles shown in my Patent 2,301,264 are'the standard'conventional handles used today andtheiraxial position "is'more convenient for most. grinding, but in the" and more particularly the -"thumb and fingers.

I It is a known that that thel'ei's a defi nitel'imit t0 the size of the periphery or diameter ofa bar which can be comfortably andtightlygripped by a normal hand,'and.:such limitedlcircumference I does not allow-sufficient-leverage to resist the reactive torque in many cases, a diameter in the neighborhoodpf'. 1% incheshas been g'enerally recognized in this fieldas a comfortable handle .omitted.

Fig. 3 isanend view of Fig. 1 substantially as tindicated by line 33 of Fig. 1.

Fig. 4 is .view from the other end i substantiallyas indicated by line 44 of Fig. 1, held in the-left hand.

size. I have found that a range of one to two and one-quarter inches is possible, although the extreme sizes are much more fatiguing where reactive torque must be resisted.

Another object is to provide an abutment or lever arm projecting from a hitherto practically unused and ungripped portion of the handles of the class of toolsalready described, said lever arm contacting the,. proximal end or portion of hypothenar eminence of the operators hand adjacent to the wrist in a manner to form such a steep cam relationship as to effect not more tha a minor resultant tending to open the hand or to act against the muscles maintaining the grip thereon.

Another object is to relieve the fingers, hand and the wrist of the operator. from much of the fatigue incident to resisting the torque reaction of the motor by applying said forces more direct-' ly to the wrist and more adjacent to the forearm and tea muscular mound moreadapted to receive themwithou't fatigue or discomfort.

Another object is to increase-the hourly pro- Jduction of the operator'by reducing his 'or her fatigue and also by utilization of the maximum horsepower capacity of .the tool and. by the increase in the horsepower capacity and also by .Also to provide. a, ,torquearrestor .lever, as I jwill hereinafter call an embodiment of myinvention'that will'innocase hamper the-.release of .the toolby the operator in the case of an emergency.

' Other objects are-to increase the productivity .and metal removing capacityl oi. portable tools without increasingbperator .labor and to reduce the labor .Of-g handling-. many. portable tools, so ,that war workers such.-asuwomen, who have not suflicient hand-strengthto handle many tools now on themarket; can takeover more types of this work. I Further objects and novel-features of my construction will bepapparentfrom the following specifications and :claims when considered to- .-.gether with theaccompanying-drawings in which:

V ,Fig. -1 is aside elevation ofv a conventional elecztric grinding tool towhichhas been added embodiments oimy. invention. The wheel end han dle is grasped-with the left hand'and the other handle with the right. I

Fig. 2 is atop elevation ofFig. lzwith the hands of Fig. 1

Fig.6 is a top or plan'view of a spindle end Ill) ings or to the specific type of motorization or tool selected for illustrative purposes.

In Fig. l I show, as an example, the wheel end or work spindle handle H of a portable grinder powered by a 180 cycle induction electric motor mounted in a frame or housing I2 of approximately 2 horsepower under average working conditions but having a stalling torque. equivalent to double the working torque. The speed of the grind wheel 9 is geared down to 4000 R. P. M. which at a 2 horsepower load results in a torque of approximately 31.5 inch pounds to be resisted by the operator by gripping two handles such as a wheel end handle H or live end handle 20 which has a diameter of approximately 1% inches and is positioned substantially parallel to the axis of the motor in housing l2.

This means that while working at full capacity the operator must constantly resist 42 pounds torque at the surface of the gripping handles. In an effort to preventthe' tool 'from'turmfng in his hand, he must oftenwg'ripit so:.tightly-:that the circulation of blood tor-his fingers is -so "-restricted'a's to further exaggerate his fatigue.

Under :stalling conditions, because the JnOtOl is a substantially constant speed induction-motor, the stalling reactive'torque. inithe example:set forth would be about 63. inch pounds or-84pounds on the surfaceof the handle to be resisted bygthe grip of the operator. If :the wheel grabs, the. tool is often wrenched' from the operatorshands; suddenly and without warningand he cannot contact the push button switch. III to stop the-motor while the'tool is revolving. Fearthat the stallingv thing applies proportionately to s-mallen-tools" and it is obvious that in all events it ;will be possible for such'an operatorgto .usea tool-equipped with mydnvention possessing at-least twice thepower i of the ,;maximum size"- tool=which she could use without the benefit of my.-.invention, becauseas previously;saidrmy invention more than doubles the lever-arm. Also with a;.subs.tantially .round axial handle such as: is conventionally used-.the grip is-largely a-matter of friction whereas .with

w my utorque arrestor lever a positive abutment 'tweenthe axis of the handle-and -the,axis-of the -wrist joint. By abutting mylever more. adj acent tothe wrist I -materially -.reduce this distance with theq-gear housing 1,6. lever I 5' oifersa surface to .contactywith theproxi- :and reduce accordingly. the strain on' the muscles controlling the wrist movement.v v

The forward torquearrestor; lever 15 :arises from-the midportion-ofthe wheelend handle as seen in l,sloping;,up; as shown toblend -.Theytorque arrestor "mal, endnor portion of;-hypothenar eminence: ,of

the hand ,ofmthe 'operatorfiubstantially normal to the tangent of the cylindrical surface-ofg-the handle I l10r'it can be described as havingasteep cam: relationship with theihand. of the; operator .which effects only; a minor; resultant: of forces the torque arrestor abutment I 5'or'2 I the case 'maybe, andif the direction of rotation-was re- In Fig.2 it will be seen that-it i's 'set' at an angle of'about 2 to the axis'of the handles so that it can besaid-that it is-set at a helix angle-on the handle'or work spindle I3 {of the tool which passes-through handle- I I. Whenlooking at the lever- I is'set at a right handhelix angle. If

the wheel (or work spindle I3) turned counterclockwise then the helix angle'of' thetorque arrester could be left'hand such as 'I'IFig. 5. on a reversible tool," then both-angles would be used so that the combination of both helix angles combining would create a wedge torque arrestor lever I5 and II with its apex pointed toward the grind wheeler-metal cutting end as viewed from the top as in Fig. 5. This construction is included in my invention.

Fig. 3 shows the torque arrestor lever I5 pressing against the hypothenar eminence of the operators left hand and approximately adjacent to the wrist joint of the forearm sometimes popularly called the heel of the hand. When the wheel as shown in Fig. 3 turns clockwise the reactive torque tends to turn the handle I I counterclockwise to do this, so that the torque arrestor lever I5 prevents the handle II from turning in the hand of the operator even though his grip is materially relaxed compared with the necessary required tightness if the torque arrestor abutment I5 were absent.

Fig. 1 also shows that the circumference or perimeter of the part actually gripped is not increased but additional leverage is provided by the torque arrestor abutment pressing against the hand heel or wrist joint without making the size of the gripped part uncomfortably large. Figs. 1, 3 and 4 also show that in gripping any conventional handle of reasonable and comfortable size that there is a normally unused portion of the periphery beyond the ends of the third and little fingers. From this normally unused and uncontacted portion of the handle I project my torque arrestor levers I 5 and 2|.

Such tools as grinders are used by some operators holding the wheel end handle in the left hand as shown in Fig. l and other operators hold the wheel end handle with the right hand. Since the direction of revolution of the wheel 9 is uniform it is obvious that in the latter case the torque arrestor lever I5 will tend to turn away from the heel of the right hand if so held and accordingly in this case would not provide as much benefit in holding the tool in this way as when handle II is held in the left hand.

To provide the maximum benefits of my invention under conditions where the hands are reversed left and right from the way shown in Fig. 1, I have also applied my invention in the form of a second torque arrestor lever 2| to the rear or live handle 20 in a modified form, as will be seen in Figs. 1, 2 and 4.

When grinding with a tool having the conventional right hand direction of rotation which is held with the right hand gripping handle I I and the left hand gripping handle 20, then the torque arrestor lever 2| will be pressed by the reactive torque of the motor against the heel or hypothenar eminence of the left hand adjacent to the wrist joint.

It will be noted from this explanation that when the wheel is rotated in a clockwise direction as shown in Fig. 3 then the left hand resists versed then the right'hand resi'ststhe torque arrestor abutment or 2I,-"=re gardless of which hands hold the handles I I- and-20, so long asthe thumbs of both hands are-toward the wheel or work spindle as they customarily are.

It will be seen that in the drawings that the switch I 0 is always conveniently located for 'actuation by the thumb or first finger and I have 'invented means to-greatly assist the resistance of torque reaction in a portable" tool without I any encircling or other meahswhich might catch or strike the fingers, hands, or'body of the careless operator or which might interfere with the s11d den release of the tool-by an operator in event of anaccident. I I l *In 'this-application where Irefer to the grind wheel it should be understood that I mean any abrasive polishing, metal cutting or working tool or other type work spindle.

It also should be understood that it is in the realm of my invention to make either or both torque arrestor lever I5 and 2I either as an integral part of handles II or 20 respectively or as a separate and removable attachment thereto or with one of them integral with its handle and the other detachable and/or adjustable angularly relative one to the other.

The wheel guard 22 is clamped by bolts 23 to the wheel end handle II so that it can be set on the handle at any convenient angle about the tool axis relative to the torque arrestor lever I5. As seen in Fig.1 the wheel guard does not completely cover the wheel 9.

Bolts 26 have a common bolt circle radius likewise bolts 21 so that the wheel end handle with torque arrestor abutments I5 can be set at various angles to handle 20 with torque arrestor abutment 2 I. Other means to accomplish this indexing of the guard 22 and handles II and 20 are well known in the art and may be substituted without departing from the spirit of my invention such as attaching torque arrestor abutment 2| through association with the thread nipple 25.

Accordingly I claim:

1. A manually portable unit including the combination of a motor, a shaft rotatably driven thereby, a rotary work device attached to said shaft, a handle having a substantially longitudinal axis positioned sufficiently adjacent to the line of the axis of said shaft and sufficiently parallel thereto to cause said handle to be turned principally about its said longitudinal axis by reactive torque incident to the motora-cting to revolve the work device, and a lever predominatingly projecting from only one side of a portion of said handle and adapted to be pressed by said reactive torque against the proximal portion of the hypothenar eminence of a hand grasping said handle and to thereby resist the turning of said handle and tool unit in said grasped hand under said reactive torque primarily by abutment with said proximal portion of the hypothenar eminence of said hand in contra-distinction to friction therewith.

2. In a manually portable unit including the combination of a motor, a shaft rotably driven thereby, a rotary work device attached to said shaft, a handle having a substantially longitudinal axis positioned sufficiently adjacent to the line of the axis of said shaft and sufficiently parallel thereto to cause said handle to be turned principally about its said longitudinal axis by reactive torque incident to the motor acting to unit under said reactive torque primarily by :abutment with :said portion of thehyDQthenar .-eminenc e of said hand in contra-distinction to iriction therewith.

3. Amanually portable unit including-,theicom- ,bination of a motor, a shaft rotably driven thereby, a rotary work device attached to :said

U'Shaft, a handle-having a substantially longitudinal axis positioned sufiiciently adjacent to the .line of the axis of said shaft and sufiiciently parallel thereto to cause said handle to he turned ifprincipally about its said longitudinal axis; by re- {active torque incident t 0: the motor vacting-to re- -;volve the work device, a lever predominating'ly projecting from one side of a ,portion Qf'SMd handle and adapted to 'be;pressed bysaid reactive torque :against the proximalportion of the hy- DOthBnaIzCIniIlBIiCi-Z of ahandgrasping said handleand-tothereby resistithe turning of saidhandleand1tool unit under aid reactive torque ,primarily by abutment .with said zproximal portion of the hypothenar eminence of said hand in contra-distinction to friction therewith, said point of abutment of said lever with said .hand being-nearer the wrist and further fromthe .axis def saidhandle thereby increasing'the leverage of the handon the .tool and reducing ,theleverage of the tool on the hand.

WILLIAM M. EMERY.

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