US2307431A

US2307431A - Power driven abrading device

Info

Publication number: US2307431A
Application number: US410988A
Authority: US
Inventors: Dwight M Tilden; Carl S Tilden
Original assignee: Individual
Current assignee: Individual
Priority date: 1941-09-16
Filing date: 1941-09-16
Publication date: 1943-01-05
Anticipated expiration: 1960-01-05

Description

H7251 w1- ?.mflwl /j Jan. 5, 1943. D M TILDEN ETAL 2,307,431

POWER DRIVEN ABRADING DEVICE Filed Sept. 16, 1941 4 Sheets-Sheet 1 *gjm r" ,gama

k W//f/x//M l/l/f//ff//A V/////////////// A TT ORNE Y .313. IJIE. HL WUHNRL Jan. 5, 1943. D. M. TILDEN Erm.

Filed Sept. 16, 1941 POWER DRIVEN ABRADING DEVIGE Cross Reference 4 Sheets-Sheet 2 W/'WLT-TORNEY Examiner .29. METAL wonxma: (MSS Referenc@ F? D. M. TILDEN EIAL POWER DRIVEN ABRADING DEVICE i-Jan. 5, 1943.

4 Sheets-Sheet 3 Filed sept. 1s. 1'941 @1r/@vr M 77.405# and INVENTORS;

M/sv" w A TTORNE Y LCUIIIHT Cross Reference Filed Sept. 16, 1941 4 Sheets-Sheet 4 WNN BY @d/W' .ATroRA/sy.

29. METAL wuunum.

Jan. 5, 1943.

swam .\NN\ \\QQ- n N om E LV um M L 7 e H M u SQ @QN N QNX 4S mw QNT e n E QQ QQ ma, w www QQ@ uw W N91 aww T, nh? .QN d l, NQN WN\ QNN NU .QN .N kan me mdw Patented Jan. 5, 1943 UNITED STATES PATENT FFICE Powea DRIvEN ABRADING nevica Dwight M. 'rilaen and can s. Tiiden,

` Glendale, Calif.

13 Claims.

This invention relatesvto power-driven tools and pertains particularly to an abrading device adapted for manual use.

One of the particular objects of the invention is to provide a power-driven abrading deviceadapted to have great capacity for removing material from the surface worked upon, together with substantial freedom from vibrations.

A further important object of the invention is to provide a device of the character described which is of relatively inexpensive construction, durable, and capable of high operating speed, together with stability and uniformity of operation.

Application September 16, 1941, Serial No. 410,988

A further object of the invention is to provide a power-driven abrading device provided with an improved form of drive means which enables the device to operate at an exceptionally high speed while preserving the stability characteristics of the device so that the device may be handled in a safe manner.

A further object of the invention is to provide a device of the character described, having an elongated arcuate abrading member provided with a downwardly convex working surface and reciprocable in the direction of the length of such member, said memberbeing so mounted that the path of movement of each point of the worksurface thereof is substantially coincident with the curvature of the abrading member at such point.

A further object ofithe invention is to provide an improved type of enclosed fiuid lubricant-containing housing construction for reciprocatory driving devices having a driving element slidably mounted at or adjacent the housing side-wall, characterized by the provision -of a condition of reduced pressure withinthe housing for elimination of loss of lubricant from such housing.

Other objects of the invention will be specifically pointed out in the following description of certain preferred embodiments thereof, or will be apparent therefrom.

The device of the invention comprises,'essen tially, an abrading member disposed in an arcuate i'elation,"together with means for reciprocating the abrading memberlengthwise along its curved position, i. c., along a path substantially conforming to the curvature of such member. More particularly, the device may comprise a frame having a motor member operatively associated with an elongated longitudinally recipror cable support member carrying an abrading element, su^h as a file or an abrading block such as a sandpaper holder. The abrading member is provided with a working surface having a downwardly convex'configuration.inr elle direction of its length, and the support member carrying said abrading element is mounted at its respective ends on said frame for longitudinal reciprocatory motion along a path such that the path of movement of each portion of such working surface conforms closely to the curvature of such working surface and coincides with such curvature at at least one point in such path of movement.

The accompanying drawings disclose illustrative embodiments of the invention, and referring thereto:

1 is a side elevation of one form of the device, on somewhat reduced scale;

Fig. 2 is an enlarged longitudinal section of the device-shown in Fig. l,`showing the constructional elements in greater detail;

Fig. 3 is a partly broken-away inverted plan view of the device shown in Figs. 1 and 2;

Fig. 4 is a transverse sectional detail taken on line 4 4 in Fig. 2;

' Fig. 5 is a partly broken-away view substantially corresponding to Fig. 2, illustrating a modied form of the invention;

Fig. 6 is a partly broken-away inverted plan view thereof, corresponding to Fig. 3;

Fig. '7 is a transverse sectional detail thereof taken on line 'l-l in Fig. 5;

Fig. 8 is diagrammatic representation of one arrangement of the curved le and its mounting' means which may be established to secure certain advantageous operating characteristics of the device of the present invention;

Figs. 9 through 11 are diagrammatic representations of the character of reciprocatory movement which may be secured according to the invention;

Figs. l2, 12a and 12b are fragmentary details of a modified form of driving means which may be employed to reciprocate a curved abrading member according to this invention, Fig. 12a being a transverse section of a portion ofthe device, as taken on line I2a--I2 in Fig. 12, and Fig. 12b being taken on line |2b-l2b in Fig. 12a;

Figs. 13 and 14 are longitudinal andI transverse sections, respectively, the further mcdication of the invention, corresponding to Figs. 5 and 7, Fig. 13 being taken on line-|3-I3 in Fig. 14, and lFig. 14 being taken on line N-H in Fig. 13; and

Figs. 15, 16 and 17 are longitudinal and sectional details and an inverted plan view, respectively, of a further modification of the invention, showing an abrading device adapted for use as a sander, Fig. 16 heini?,r tak-@gon line Iii-I6 in Fig. 15,.

Referring to'r'ig's'; l to 4, the device may com- 29- wit-it. Illumunw prise, in one embodiment, a housing member I carrying a forward support arm 2 provided with articulated file-supporting means such as a downwardly convex (in a longitudinal direction) backing plate 5 pivotally mounted on

support arms

3 and 4 and adapted to carry an abrading element such as a file 6 in a condition of comparable curvature. The device further includes a driving member such as a motor I which may be secured to the upper end of the 4housing I, as at 8, and having a drive shaft 9 extending into the housing I and terminating in a worm gear I I mating with a worm wheel I2 carrying an eccentric I3 operatively associated with a yoke I4 mounted on a crank arm I5 integrally connected with the rearward crank arm 4. The device is preferably also provided with a suitable handle member IS which may be carried on rearwardly extending brackets I'I and I8 which may be secured, respectively, to the motor 'I and the rearward end of the housing I. An electrical supply conduit is indicated at I9, and a suitable switch or the like is indicated at 2I for control of the operation of the motor.

A suitable sleeve bearing may be provided as at for the projecting shaft 9, said sleeve bearing being carried by the housing I in any suitable manner. The worm Wheel I 2 is conveniently carried on a stub shaft I2a extending transversely of the device, and the mounting of the

crank arms

3 and 4 may be provided through the agency of

pins

3a and 4a mounted in suitable openings or recesses in the supports 2, as shown more particularly in Fig. 4 in connection with the crank arm 4. The respective crank arms 4 and I5 in this construction may be secured to the pin 4a through the agency of set screws or the like 26 and 2'I, and the crank arms 4 and I5 preferably extend through suitable slots 28 and 29 in the supports 2, said slots being closely tted to the diameter of the crank arms to provide a fairly good seal against loss of the lubricating agent which is contained within the housing I as hereinafter described.

The `member 5 is preferably pivotally secured to the

respective crank arms

3 and 4 as through v the agency of

pin bearings

5a and 5b, and the file 6 is conveniently secured to the member 5 through the agency of countersunk screws 6a and 6b, the heads of the screws being recessed sufhciently to allow the same to pass over the work in normal use of the device.

In order to keep the gears II and I2, eccentric I3, yoke I4, and the bearing 4a adequately lubricated, a suitable supply. of lubricating fluid is maintained within the reservoir provided by the housing I, and in order to prevent loss of this lubricant from the reservoir we preferably provide for the maintenance of a slightly reduced pressure within the reservoir during operation of the device so that the tendency will be for inltration of air from the atmosphere rather than loss of lubricating agent to the exterior. This condition of reduced pressure is conveniently secured through the agency of the conventional blower or fan Wheel provided for small motors of the type illustrated at 'I, such fan wheel being illustrated at 3I. In order to provide communication between the reservoir and the low pressure side of the fan Wheel 3|, we may bore the shaft 9 axially to provide a passage 32 which communicates at its lower end with a transversely extending passage 33 in the worm II and at its upper end with a comparable passage 34 at a point adjacent the fan Wheel 3 I. Upon operation of the UNSS Reference motor l, the rotation of the fan wheel 3l will cause a reduced pressure at the position of the passage 34, which reduced pressure will be communicated to the interior of the housing I through the associated passages 32 and 33, but substantially no lubricant will be lost from the housing through the several passages by virtue of the relatively high speed of rotation of the worm wheel I, which produces a suciently forceful centrifugal effect upon the lubricant present adjacent the passage 33 to keep it from entering the vertical passage 32 and thus escaping from lthe motor. The effectiveness of the provision of the reduced pressure condition within the housing depends to a considerable degree upon the housing being substantially sealed against the atmosphere, by virtue of the small clearances obtaining at the position of the pivot pin 4a and the motor shaft 9, which slidably engage the housing walls. These clearances are small enough to prevent gravity flow of lubricant from the housing should the device be inverted, and the reduced pressure condition within the housing during operation of the device results in a gradual infiltration of air to (rather than loss of lubricant from) the housing.

The above construction, providing for elimination of lubricant loss from a substantially enclosed housing, is applicable to other types of apparatus presenting the same problem, and in this respect we do not consider our invention limited specifically to power-driven abrading apparatus.

The alternative construction illustrated in Figs. 5 through 7 may comprise a housing 4I carrying a driving motororl the like 42, a forwardly extending support 43, and a suitable handle member 44, all corresponding to the arrangement of the corresponding elements of the firstdescribed form of the invention. The file member 45 is carried on the support 43 at its forward end through the agency of a sliding mount 46 adapted to provide for reciprocation of the file member in the direction of its length, and the rearward end of the le member may be supported through the agency of a vertical arm 4'I pivotally secured to a shaft 48 extending through a guide 49 mounted on the housing 4I. The shaft 48 terminates in a Scotch yoke 5I engaged by an actuating slide 52 pivotally mounted on a gear 53 eccentric to the axis of rotation of said gear. The gear 53 is rotatably mounted on the housing 4I as at 54 and is driven by a pinion 55 mounted on the shaft 56 of the motor 42. The motor 42 is preferably provided with a fan wheel 51, and the shaft 56 is provided with passage means 58, 59, and 6I, corresponding to the

passages

32, 33 and 34 in the first-described form of the device for maintaining the space within the housing 4I under the desired condition of reduced pressure during operation, to prevent escape of lubricant therefrom as hereinbefore described. The slidable mounting of the forward end of the file 45, shown at 46, may comprise a rectangular pin 62 pivotally secured to the housing 43 and slidably carrying a cooperatingly shaped lug 63 which is secured to or formed integrally with a backing member 64, to which the file 45 or other desired abrading element may be secured as through the agency of countersunk screws as above described.

The movement imparted to the elongated abrading element is intended to be one such that the path of movement of each point ofthe work- LXmInBr caused to have a sweeping movement over the surface which is being worked upon in the abrading opera-tion. In the form specifically illustrated in Fig. 2, the pivot points defined by the

pins

3a and 4a are established along the radii of the curvature of the file member 6, with reference to an intermediate position of the le member in its stroke, corresponding to the dot-dash lines r1 and r2. This arrangement is illustrated more particularly in Fig. 8 wherein the radii r1 and T2 intersect at a point which constitutes the center of curvature of the le G. The actual movement of each portion of the working surface of the file in this embodiment will be dened by an arc having a curvature limited by the separation of the pivot points from the working surface, but this movement will conform to an arcuate path which is tangent to and conforms closely with such working surface.

I'hismovement is more particularly illustrated in Fig. 9 wherein a fragmentary portion of the file member is indicated at 'l0 on enlarged scale, two adjacent file teeth being indicated at 10a and 10b. In this figure the vertical dot-dash line ll corresponds to the radius r2 in Fig. 8, and the arcuate path of movement of a tooth '10a is :indicated by the dot-dash line l2. This path of movement is symmetrical with respect to the line 'll and it will be seen that as the file is reciprocated in a power stroke from right to left the tooth 70a Wi1l-dig in until the line ll is reached and will then lift for the remainder of the stroke. rl'his type of movement, taken with the fact that the stroke is preferably somewhat in excess of the longitudinal separation of the file teeth, results not only in fairly rapid removal of the metal from the surface worked upon, but also results in clean work due to the continued tendency for the file to clear itself.

It will be appreciated thatI the relative amounts of dig and lift" provided in the operation of the le member may be controlled within substantially any desired degree, by adjusting the longitudinal position of the reciprocating stroke with respect to the vertical line corresponding to the radius of curvature cf the file member, as is more particularly illustrated in Figs. l0 and l1. In 1Eig. 10 the stroke has been adjusted so that the forward terminus corresponds to the line 'll so that the power stroke of the le from right to left is devoid of lift," as indicated by the dot-dash curce 'l2'. In Fig. ll the rearward terminus of the reciprocating motion has been established at the line 1| wherefore the resulting arcuate path of movement of the file teeth is devoid of digf as indicated by the dot-dash curve '12".

Where the forward and rearward ends of the file member are carried on pivot pins having centers located on radii of curvature of the le member, as is particularly illustrated in the form shown in Figs. 1-4, the degree of lift increases progressively from the rearward to the forward end of the file member, which has been found to provide an advantageous operating performance of the device.

In Figs. 12, 12a and 12b we have illustrated a modified form of device, the general character of the type illustrated in Figs. 1 to 4, in which provision is` made for adjusting the throw of the abrading element supper@ member to secure any desired movement between the extremes illustrated in Figs. 10 and 11, and referring thereto, we provide a housing member 13 carrying a forward support arm 14 provided with articulated le-support means l5 corresponding to the support arm and backing plate construction shown at 3-5 in Figs. 1 to 4. The adjustment of the throw of the articulated file-supporting means is provided by means of a dove-tail mount 'i6 provided with an adjusting screw Il mounted on the drive arm 18 secured to pivot pin 19 corresponding to pivot pin 4a in the first form of the invention. 'I'he dove-tail mount 'I6 carries a yoke 8l corresponding to the yoke I4, riding on an eccentric 82 provided with gear means 83 associated with a motor B4, the latter corresponding to the elements indicated at 1, Il and l2 in the first form of device. A suitable plug 85 is provided in the wall of the housing 13, which may be removed to permit insertion of a screw driver or the like as shown in dot-dash line at 86, for adjustment of the screw 1'1 to change the throw of the device. The screw 'l'l may be provided with a reduced diameter portion 'Vlav engaged by a key (such as a Woodruff key) 16a held in the mount '16, it being appreciated that the screw 11 is threadedly engaged in the dove-tailed portion 18a of the drive arm 18.

In the form illustrated -in Fig. 5, the actual movementof the file member 45 at its rearward end is in the plane of the working surface, and the paths of movement of the various sections of the file forwardly of the rearward end will conform substantially to a plane movement conforming to the tangent to the curvature of the file at the particular section under consideration.

In Figs. 13 and 14 we have illustrated a further modification of the construction comprising housing provided with a forward support or frame member 9| carrying an arcuate le-support member 92 slidably disposed in arcuate slides or guides 93 in the support 9| and adapted for reciprocation in an'arc corresponding to the arc of curvature of a flle member 94 carried by the le support member 92. This construction provides substantially the same movement as that of the form shown in the Figs. 5 through 7, and any desired form of driving means may be employed to secure the desired reciprocation of the le structure. For the purpose of simplicity the driving means is illustrated as of the type employed in connection with the form shown in Figs. 5 through 7, the only modification necessary being in the pivot-al mount o1 the driving shaft 95 to the le support structure 92, namely, in the provision of a slotted stud S8 on the le support member receiving a driving pin Sl secured to the driving shaft 95 to permit transverse movement of the stud 98 with respect to the shaft 95 during reciprocation.y

While we have specifically-illustrated and described ilie motormeans for actuation of the structure 'as Comprising 4an electric motor, it will be appreciated that any other equivalent motor means such as an air driven motor, may be substituted. We prefer to reciprocate the file member at a frequency of from 1000 to 3000 cycles per minute, and the amplitude of oscillation of the le member (where ay le is used as the abrading element) is preferably so established that the length of the reciprocating stroke at the working surface is in excess of the longitudinal spacing of the le teeth.

Where thedevic is to be employed as a sander the stroke is still made relatively short, say about 1A" to 5A". It will be appreciated that the abrading device of any of the above-described forms may be converted into a sander by removing the screws 6a and 6b and the file 6, for example, and attaching a sanding block in place thereof.

In Figs. 15-17 we have illustrated a further modification of the support structure for the abrading element, and have shown a sander attached in place of the le. Referring to these figures, a housing member is shown at carrying a forward support arm |02 provided with a reciprocatory abrasion element supporting-member pivotally mounted at the rearward end as by means of a crank arm |04 and slidably mounted at the forward end as at |03. An abrading member such as a sanding block |06 is attached to the support member |05 as by means of screws at I05a. The driving motor is shovm in broken-away position at |01, driving an eccezitric H3 operatively associated with a yoke ||ll mounted on a crank arm 5 integrally connected to the crank arm |04, as in the first-described form of the invention.

The abrading element supporting member' |05 is preferably pivotally connected to the crank arm |04 as at |051; at its rearward end, and the forward end of the member |05 is provided with a slide bar mating within a coacting longitudinal guide slot or groove ||8 provided at the forward end of the forward support arm |02. The slot or groove ||8 is conveniently provided in a guide member ||9 secured in place against he arm |02. The member |05 is preferably provided with a downwardly convex longitudinal curvature as above-described in connection with the member 5, and the lower faces ||9a of the lands of the guide member ||9 are preferably of convex shape, so as to conform to the curved upper surface of the member |05 which bears against it, so that the desired arcuate movement cf abrading element is obtained.

rfhe support |05 is described above as having a downwardly convex curvature, and the flexible nature of the abrading element |06 permits the same to be curved into a comparable shape when it is forced into place by means of the screws |06a. It will occur to one skilled in the art that the member |05 may be made perfectly straight, if desired, and the cushion member |22 m-ay be so shaped (as by thickening in the middle section) as to have the desired downwardly convex shape at its lower or working face. When the member |05 is formed as a straight bar or the like, the forward end thereof in this embodiment will preferably be so formed in relation to the bearing plate against which Ait slides (such as against the lower faces ||9a of the lands of the guide member IIS) so that the desired arcuate movement is secured at the forward end of the abrading element.

.The abrading element supporting member will preferably be provided with a lower surface which is curved so -as to establish the desired curvature in the abrading member which is attached thereto, however, so that the device may interchangeably be provided with a file, sanding block, or any other type of abrading member which is of sufiicient flexibility to conform to such lower surface when attached thereto.

This application discloses and claims the subject-matter ci our co-pending application Ser. No. 274,532.11led May 19, 1939, allowed March 17, 1941.

Other modifications of the structure will occur to those skilled in the art and we do not prefer to be limited to specific embodiments herein delineated and described but rather to the scope of the subjoined claims.

We claim:

l. A power-driven abrading device for manual use, which comprises: a frame member having a forwardly elongated support portion provided with an opening along one side thereof; guide means on said support portion disposed closely adjacent said opening; motor means mounted on said frame member; a forwardly elongated abrading member cari'ied by said frame member and extending below said support portion at the position of said opening, said abrading member being curved along its length to define a downwardly directed convex working surface, and being mounted on said guide means for reciprocatory movement along its length in an arcuate path so that the path of movement of each point of the working surface of said abrading member conforms substantially to the curvature of such member at such point and coincides with such curvature at at least one position in such movement, said guide means being positioned closely adjacent such working surface; and driving means associated with said motor means and said abrading member for imparting such reciprocatory movement.

2. A power-driven abrading device for manual use, winch comprises: a forwardly elongated frame member having a housing portion at its rearward end defining a, gear box; motor means secured to said frame member adjacent said housing; a forwardly elongated abrading^mem ber disposed below said frame member forwardly of said housing portion, said abrading member being curved along its length to define a downwardly directed convex working surface; guide means for said abrading member including articulated support means adjacent the rearward end of said abrading member pivotally secured to said frame member to provide forward and rearward reciprocating movement of said abrading member with. respectgto said frame member in an arcuate path so that the path of movement of each point in the working surface of said abrading member conforms substantially to the curvature of said member at such point; driving means operatively associated with said articulated support member; gear means disposed in saidhousing portion and operatively associated with said driving means and said motor means to effect reciprocation of said abrading member upon operation of said motor means.

3. A power-driven abrading device for manual use, which compn'ses: a frame member having a forwardly elongated support portion; a forwardly elongated abrading member extending below said support portion, said abrading member being curved along its length to define a downwardly directed convex working surface; reciprocatory support means for said abrading member constraining said abrading member to reciprocating motion along its length in an arcuate path, the path of movement of each portion of the working Surface of such abrading member being in substantial conformity with the curvature of such member at such portion and in substantial coincidence with such curvature at at least one point in such path of movement; and driving means mounted on said frame member and operatively associated with said abrading member for effecting such reciprocating movement, said reciprocatory support means comprising an articulating structure including a pivot arm pivotally secured to and extending radially upwardly from said abrading member with respect to the curvature of said convex working surface at one position of said abrading member in its reciprocatory movement, and adjacent one end thereof, said pivot arm being pivotally secured to said forwardly elongated support portion at its upper end.

4. A power-driven filing device for manual use, which comprises: a frame member having a forwardly elongated support portion; a forwardly elongated file member extending below said support portion, said file member being curved along its length to denne a downwardly directed convex working surface; reciprocatory support means for said file member constraining said le member to reciprocating motion along its length in an arcuate path, the path of movement of each point of the working surface of such file member conforming substantially to the curvature of such le member at such point and being coincident therewith at at least one position in such path of movement; and driving means mounted cn said frame member and operatively associated with said file member for effecting such reciprocating movement, said reciprocatory support means comprisingr an articulating structure including two longitudinally spaced pivot arms pivotally secured to and extending radially upwardly from said file member with respect to the curvature of said convex working surface at one position of said nie member in its ieciprocatory movement, said pivot arms being pivotally secured to said forwardly elongated support portion at their upper ends, and one of said pivot arms being connected to said driving means for operative association therewith to cause oscillation of said support arms and the file member between positions at opposite sides of said one position.

5. A power-driven filing device for manual use, which comprises: a forwardly elongated frame member provided with a gear housing at its rearward end; motor means secured to said frame member at.the rearward end and extending upwai-diy therefrom; a forwardly extending file member pivotally secured to said frame member at two longitudinally spaced points located adjacent its forward and rearward ends respectively, said f'lle member being curved along its length to define a downwardly directed convex working surface and the pivotal mounting of said file member on said frame member being such as to provide for reclprocatory movement thereof along its length in an arcuate path such that the path of movement of each point of the working surface of said le member is substantially tangent to the curvature of said working surface at such point; driving means operatively associated with said file member and including gear means located within said housing and operatively associated with said motor means and effecting reciprocation of said file member; and a handle member secured to said frame member at a position rearwardly of said housing and in substantial lateral alinement with said forwardly elongated file member.

6. A power-driven abrading device for manual use, which comprises: a frame member having a forwardly elongated support portion; motor means mounted on the rearward portion of said frame member; a forwardly elongated abrading member carried by said frame member and extending below said support portion, said abrading member being curved along its length to dene a downwardly directed convex working surface, and being mounted for reciprocatory movement along its length in an arcuate path so that the path of movement of each point of the working surface conforms substantially to the curvature of such abrading member at such point; a gear housing carried by said frame member; gear means disposed within said housing and including driving means operatively associated with said abrading member for effecting such reciprocatory movement, said motor means being provided with shaft means extending into said housing and operatively secured to said gear means, said motor means being provided with a fan member adapted to produce a condition of reduced pressure at a point adjacent said lhousing and including passage means establishing fluid communication between the interior of said housing and such point of reduced pressure.

7. A power-driven abrading device for manual use, which comprises: a forwardly elongated frame member provided with a housing portion adjacent one end thereof; motor means secured to said frame member adjacent said housing portion; driving means including a longitudinally reciprocable driving member having a portion extending forwardly from said housing portion; a forwardly elongated abrading member pivotally secured at its rearward end to said driving member, constrained to move therewith, and being curved upwardly and forwardly to define a downwardly directed convex working surface, said abrading member being slidably mounted on said frame member at its forward end and adapted for reciproca tory movement through operation of said motor means along an arcuate path such that the path of movement of each point of the working surface of said abrading member conforms substantially to the curvature of such abrading member at such point.

8. The construction set forth in claim '7, the forward end of said abrading member being slidably mounted on the forward end of said frame member through the agency of an elongated guide .member secured to said frame member and adapted to constrain the reciprocating motion of the forward end of said abrading member to substantial conformity to the curvature of said member at its forward end.

9. The construction set forth in claim 7, said forwardly elongated frame member being provided with an arcuate guide conforming to the curvature of said abrading member, and said abrading member being slidably mounted on said arcuate guide.

10. In a power-driven tool, a driving means which comprises: a substantially closed gear housing adapted to contain a quantity of liquid lubricant; a motor member provided with an aircirculating blower element adapted to produce a condition of reduced pressure at a position exteriorly of said housing, and a rotatable driving shaft extending through a wall of said housing in sliding engagement therewith; a driven member extending through a wall of said housing and in sliding engagement therewith and adapted for operative association with a tool member disposed exteriorly of said housing; and gear means in said housing operatively connecting said driving shaft with said driven member; said driving shaft being provided with a fluid-conducting passage opening at one end at said position and opening at the other end within said housing at a position removed from the axis of rotation of said driving shaft, to provide fluid communication between the interior of said housing and said position of reduced pressure condition, said gear means extending below said second-named position.

11. A power-driven abrading device for manual use which comprises: a forwardly elongated frame member provided with a housing portion adjacent one end thereof; motor means secured to said frame member adjacent said housing portion; driving means including a longitudinally reciprocable driving member; a forwardly elongated abrading member secured at its rearward end to said driving member, constrained to move longitudinally therewith, and being curved upwardly and forwardly to define a downwardly directed convex working surface; arcuate guide means secured to said frame member at the forward end thereof and conforming to the curvature of said working surface, said abrading member being slidably mounted on said guide means and adapted for reciprocatory movement through operation of said motor means along an arcuate path defined by such guide means and such that the path of movement of each point on the working surface of said abrading member conforms substantially to the curvature of such le member at such point.

l2. A power-driven abrading device for manual use, which comprises: a forwardly elongated frame member; motor means secured to said frame member; an elongated abrading member disposed below said frame member and having a downwardly directed upwardly and forwardly curved working surface; guide means located adjacent the ends of said elongated abrading meinber and securing the same along said frame member for longitudinal reciprocatory movement with respect thereto in a path conforming substantially to the curvature of said working surface, said abrading member comprising a support portion mounted on said guide means and an abrading element portion secured to said support portion, and said working surface being located at the lower surface of said abrading element.

13. A construction as set forth in claim 12, the support portion of said abrading member having a convex lower surface conforming in curvature to the curvature desired in said working surface, and the abrading element portion comprising a flexible abrading element removably secured to said convex lower surface of said support portion in a curved relation, to establish the aforesaid desred curvature at the working surface.

DWIGHT IVI. TILDEN. CARL S. TILDEN.