Patent Abstract:
A low profile vacuum driven sander as is appropriate for drywall sanding, with a vacuum flow pulled therethrough to drive a turbine whose turning through an eccentric provides an oscillating movement to a sanding pad that releasably mounts a section of sanding material thereto, and with that vacuum air flow also removing sanded particles and dust off from the sanded surface and transports it through the sander and a connected pipe or hose into a catchment container. The sander housing includes a pair of spaced inlet ports that are formed to provide a balance air flow into a turbine chamber that contains a turbine that is journaled axially to bearings of a bearing assembly maintained in a bearing assembly cavity of a center stanchion, with the bearing assembly cavity separated from the vacuum air flow and is ported to without the sander housing for providing, when the sander is operating, a fresh air flow into the bearing assembly cavity, prohibiting dust as is entrained in the vacuum air flow from entering the cavity as could interfere with bearing functioning and result in a loss in sander efficiency and malfunction. The turbine is preferably formed from upper and lower sections that are of different heights for facilitating assembly of the bearings in the bearing assembly cavity to, in turn, allow the sander housing to be formed having a low profile, and includes a coupling assembly of the sander body to a vacuum tube that can be freely adjusted and locked in place at a desired angle to a surface to be sanded.

Full Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention pertains to sanding devices, and in particular to a light weight pole sander for use in sanding dry wall that is attached to a vacuum hose to be vacuum driven and to remove sanding dust off of a wall surface and pull that dust into a vacuum canister. 
     2. Prior Art 
     The present invention contemplates a new and improved vacuum driven sander that is appropriate for mounting onto a hollow tube or pole to be manually moved over a sheet rock wall to function as a dry wall sander, providing an oscillating sanding section that mounts a sheet of sanding material. The sanding section of the sander is operated by a vacuum driven turbine to smooth a dry wall surface, creating dust that is pulled through the turning turbine blades and into the hollow tube that a vacuum hose is connected to, to vent into a vacuum canister. 
     Heretofore, a number of sanding tools incorporating vacuum devices for removal of sanded particles and for transporting them through a connected vacuum hose to a collection vessel have been employed. For example a number of U.S. utility patents to Mehrer U.S. Pat. No. 4,062,152; to Marton U.S. Pat. No. 4,184,291; to Romine U.S. Pat. No. 4,697,389; to Paterson U.S. Pat. No. 5,007,206; to Sanchez, et al. U.S. Pat. No. 5,193,313; to Brown U.S. Pat. No. 5,283,988; to Matchuk U.S. Pat. No. 5,605,600; and to Brown U.S. Pat. No. 5,624,305, all show examples of manual sanding devices whereto is connected a vacuum hose for drawing dust off from a surface being sanded. Similarly, a number of electric motor driven devices that connect through a hose to a vacuum or suction device have been developed and examples of such are shown in U.S. Patents to Davies U.S. Pat. No. 1,800,341; to Jones U.S. Pat. No. 3,468,076; to Hutchins U.S. Pat. No. 3,785,092; to Hutchins U.S. Pat. No. 4,052,420; to Matechuk U.S. Pat. No. 4,782,632; to Flacheneck, et al. U.S. Pat. No. 4,905,420; to Fushiya et al. U.S. Pat. No. 5,018,314; to Chu, et al. U.S. Pat. No. 5,228,224; to Smith U.S. Pat. No. 5,384,984; to Hutchins U.S. Pat. No. 5,582,541; to Heidelberger U.S. Pat. No. 5,595,530; to Everts, et al. U.S. Pat. No. 5,637,034; and in Design Patents to Taylor U.S. Pat. No. Des. 375,885; to Gildersleeve et al. U.S. Pat. No. Des. 392,861; to Fushiya et al. U.S. Pat. No. Des. 326,398; to Morey et al. U.S. Pat. No. Des 351,976; and to Stiles U.S. Pat. No. Des. 353,313. None of which sanding devices, however, provide a sanding device that includes a vacuum driven oscillating sanding disk that, additionally, provides for removal of sanded particles from the work surface through an attached vacuum hose that is like that of the invention. Similar to the invention, U. S. Patents to Brenner U.S. Pat. No. 3,722,147; to Rodowsky, Jr. et al. U.S. Pat. No. 4,399,638; to Brenner U.S. Pat. No. 3,722,147; and to Marton U.S. Pat. No. 4,616,449, shown sanding devices where an oscillating plate mounting a sheet of sand paper is air driven by a vacuum flow and also provides for removal of sanding dust off from a work surface and the moving of that collected dust through a vacuum hose into a collection container. With the patent to Rodowsky, Jr. et al., U.S. Pat. No. 4,399,638 believed to be the closest to the invention. However, while, like the invention, the &#39;638 patent provides a turbine blade that is turned by a vacuum air flow passed over the turbine blades to operate an oscillating plate whereto a section of sanding material is attached and will pull sanding dust therethrough, the turbine bearings of the &#39;638 patent are exposed to that vacuum air flow with entrained sanding dust particles tending to collect in the turbine bearings, greatly limiting bearing life and, accordingly, the life of the device. Whereas, the invention is arranged to provide the presence of a positive or greater than vacuum pressure across its turbine bearing assembly, prohibiting the dust contaminated vacuum air flow from traveling into which bearing assembly, greatly lengthening the life of the bearings, and further allows for passing lubricants therethrough to lubricate the bearing assembly bearings, greatly improving upon earlier vacuum sanding devices, such as the &#39;638 patent. 
     Additionally, as improvements over the prior art, the invention includes a balanced split-air intake that provides a balanced driving force onto the turbine blades by drawing essentially equal air flows from both sides of the sander that also improves upon the entrainment of dust and contaminants in the air flows as are passed through the sander. Also, the turbine itself is improvement in that it incorporates a split design where the top and bottom turbine sections are not symmetrical, with the lower turbine section having the greater height to allow the bearings and bearing supports to be conveniently fitted inside the turbine mounting in the sander housing providing a turbine housing profile that is shorter than former sanders turbines and has a lower center of gravity as compared to earlier sanders. Further, the invention provides an improved pole coupling assembly whereby, the pole angle to the sander top surface can be conveniently changed and that angle can be maintained while the sander is moved up and down or along a wall surface. 
     SUMMARY OF THE INVENTION 
     It is a principal object of the present invention to provide a vacuum air driven turbine operated sander for attachment to a conventional vacuum line wherethrough an air flow is pulled, with the air turning the turbine that is, in turn, connected to turn an eccentric that is fitted into a bearing mounted in a sanding plate to oscillate that plate, thereby moving an attached sheet of sanding material in an orbital path over a surface to be sanded. 
     Another object of the present invention is to provide a vacuum driven sander that includes turbine blades and turbine bearing assembly for turning in a housing wherein a passage is provided for passing a flow of clean air at ambient pressure into the bearing assembly, providing cooling thereto, and discouraging the vacuum flow wherein sanding dust is entrained from passing to the bearings of the bearing assembly and providing for passing a lubricant therethrough into the bearing assembly, greatly extending the bearing life and the life of the device. 
     Another object of the present invention is to provide a vacuum driven sander having a low profile provided by an incorporation of a turbine, as the device motive power source, that is formed from two non-symmetrical halves and includes, as a bearing assembly, a pair of bearing and bearing supports, that are to be fitted into a stanchion formed within the sander housing to contain turbine section, with the turbine top and bottom sections to be fitted together to close off which turbine section in the sander housing. 
     Still another object of the present invention is to provide a vacuum sander having a balanced split-air intake where air is drawn from opposite sides of the housing through the turbine, efficiently picking up and entraining dust particles in the flows as are generated by oscillating movement of the sanding pad that is provided by turbine rotation. 
     Still another object of the present invention is to provide a vacuum sander that incorporates a hollow tube connected to the sander body to be conveniently adjusted at its mounting to the body top surface to change the sander pad surface angle to the wall being sanded, and provides for connection of a vacuum tube as a pole to the hollow tube end opposite to the sander body. 
     Still another object of the present invention is to provide a vacuum driven sander that is light in weight and convenient to connect to a vacuum hose to both turn an oscillating sanding plate or pad and to draw collected dust therethrough for passage to a collection container. 
     The present invention is in a new and improved vacuum air flow air driven oscillating sander that includes a bent hollow tube that connects to a hollow pole whereon the sander is mounted and is connected to pass the vacuum air flow therethrough and into a vacuum hose to vent that flow into a collection container. The bent hollow tube is arranged to turn axially at is connection to the top of the sander body at a collar that has a number of radially spaced cavities formed therein that selectively receive stub pivots fitted therein that are formed to extend oppositely from a ball end of the bent hollow tube. A cap having a center hole therein is provided to fit over the bent tube and is for turning onto the collar to maintain coupling of the stub pivots in the selected radially spaced cavities, allowing the bent hollow tube to be turned relative to the collar end and to be locked in place. So arranged, the angle of the sander forms to a wall can be adjusted by a repositioning of the stub pivots in the radially spaced cavities and turning the cap onto the collar. 
     Further unique to the invention, the sander includes a turbine that is mounted by a bearing assembly onto a stanchion located within a sander housing, and provides, by a passage formed through the housing into a bearing assembly cavity located within the stanchion, for a flow of ambient air to the bearings during operation and precludes contamination of the bearing assembly by dust entrained in the vacuum flow that has passed over the sanded surface, greatly extending bearing life over earlier air driven sanders that have exposed their turbine bearings to the dust filled vacuum air flow. 
     Additionally, the sander body of the invention exhibits a significantly reduced profile by an incorporation of a split design turbine that allows the bearing assembly to be conveniently fitted into and assembled in a bearing cavity in a shanchion formed in the housing. The construction of the turbine as a split design provides two turbine sections, with a lesser height upper section arranged to cap over the greater height lower section, simplifying mounting of the turbine bearing assembly in the bearing assembly cavity prior to fitting the assembled turbine thereto. The turbine is turned by passage of the vacuum air flow there through that is first passed through balanced air intakes where air is pulled across the surface being sanded and into the housing opposite ends, applying a balanced driving force to drive the turbine. The turbine, at its lower end, is connected through an eccentric to oscillate a sanding pad whereto a section of sanding material is releasably attached. 
     The sanding pad is formed as a plate, and the entire sander is assembled and held together by four (4) screws that are each turned through spiders attached to corners of the inner surface of the plate that are turned into the housing lid or top, maintaining the sander in its assembled state. 
     Still other benefits and advantages of the invention will become apparent to those skilled in the art to which it pertains upon a reading and understanding of the following detailed specification. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     The invention may take physical form in certain parts and arrangements of parts, and a preferred embodiment of which will be described in detail in this specification and illustrated in the accompanying drawings which form a part hereof: 
     FIG. 1 is a perspective view taken from a left side and front of a vacuum sander of the invention, showing a bent tube end extending out from a housing top section collar and cap; 
     FIG. 2 is a side elevation exploded view of the vacuum sander of FIG.  1 : 
     FIG. 2A is a top plan sectional view taken along the line  2 — 2  of FIG. 2 of the turbine lower section, showing the turbine as having the equal radially spaced turbine blades; 
     FIG. 3 is a profile sectional view taken along the like  3 — 3  of FIG. 1; 
     FIG. 4 is a front elevation sectional view taken along the line  4 — 4  of FIG. 1; 
     FIG. 5 is a top plan view of the vacuum sander of FIG. 1; 
     FIG. 6 is a front elevation view of the vacuum sander of FIG. 1; 
     FIG. 7 is a side elevation view of the vacuum sander of FIG. 1, and showing in broken lines, the bent tube coupling neck pivoted around its pivot coupling to the sander collar; and 
     FIG. 8 is a view like that of FIG. 1 showing the collar mounted onto the sander top to include radially spaced slots formed therein that are to receive stub pivots formed to extend oppositely outwardly from a ball end of the bent tube coupling neck, and with the bent tube and cap shown exploded from the collar. 
    
    
     DETAILED DESCRIPTION 
     The invention is herein described with reference to a preferred embodiment shown in the accompanying drawings, with FIG. 1 showing a front elevation perspective view of the low profile vacuum driven sander  10  of the invention, hereinafter referred to as sander. As shown in the Figs., the sander  10  includes a housing  11 , having front, rear and side walls  13   a ,  13   b ,  14   a , and  14   b , respectively, extending at right angles from the top edges, forming a narrow rectangular box configuration having, as shown in FIGS. 3 and 4 an open bottom  15  and whereover a flat top  12  is fitted. A coupling collar assembly  16  is shown in FIGS.  1 , 3  and  4 , fitted into the center of the top  12  that includes, as shown in FIGS. 2 and 8, a pair of turbine ducts  17   a  and  17   b  that are shown as flat raised sections that extend oppositely from steps  18   a  and  18   b  to an opening in the center of the flat top  12 , and are open, as shown in FIGS. 1,  2 ,  4  through  6  and  8 , to serve as ducts that pass and direct turbine exhaust air flow into a hollow bent tube  23  that is preferably bent at an angle of approximately twenty two and one half (22½) degrees, and wherethrough the flow is vented into a vacuum hose or tube. 
     The turbine ducts  17   a  and  17   b , as shown best in FIGS. 1 and 5, are slightly greater than half semi-spherical sections and terminate, as shown best in FIGS. 1,  2  and  6 , in stepped up sections  19   a  and  19   b  that join into dome  20 , as shown best in FIGS. 3 and 4. The dome  20  has a center hole  21  formed therethrough, with the edge of which hole  21  to serve as a seat whereover a ball end  22  of a bent exhaust tube  23  travels. The ball end  22  to maintain sealing engagement with the hole  21  edge, with the ball and its edge serving as a ball valve. So arranged, the turbine ducts  17   a  and  17   b  direct the turbine exhaust flow into the dome  20  that then directs that flow into the bent exhaust tube  23 , wherefrom it is exhausted through a connecting hose or tube into the collection container, not shown. 
     An upper outer portion of the walls of which dome  20 , as shown best in FIG. 8, is formed into collar  20   a  that has outer threads  24  and wherethrough the hole  21  is formed. Around the edge of which hole  21  are formed a number of radially equal spaced pivot cavities  25 , shown as half cylindrical sections that are to individually receive each of a pair of stub pivots  26  fitted therein. The stub pivots  26  extend oppositely outwardly from the ball end  22  of the bent tube  23 , and are to fit into individual pivot cavities  25 . So arranged, as shown best in FIGS. 3 and 4, with the pair of stub pivots  26  each fitted into a pivot cavity  25 , a cap  27  having a center hole  28  formed therein is slid along the bent tube  23  to where threads  29  thereof can be turned onto the outer threads  24  of the collar  20   a . With cap  27  turned onto collar  20   a  the positioning of the stub pivots  26  in the selected pivot cavities  25  is maintained, setting the positioning of the sander body  11  relative to the bent tube  23 . Which positioning, however, is preferably not rigid in that the diameter of the hole  28  through the cap  27  is selected to be somewhat larger or greater that the bent tube  23  diameter, as shown in FIGS. 1 and 5, allowing for some pivotal movement between which sander body  11  and bent tube  23 , as during use of the sander, to minimize damage to the coupling should the sander “stick” to the wall surface. So arranged, the sander body  11  is selectively positionable relative to the bent tube  23  to facilitate the sander  10  being moved up and down or side to side or at an angle therebetween, as the operator desires. The bent tube  23  preferably has its end  23   a , shown in FIG. 2, fitted into a coupling end  31  of a vacuum pipe  30 , as shown in FIGS. 1 through 7, which coupling can be by providing interior threads, not shown, formed in the coupling end  31  for turning onto threads  32  formed in the bent tube  23  end  23   a , as shown in FIG. 8, providing a rigid coupling therebetween. Or, as required, to further facilitate sander back and forth or up and down travel, the coupling can be such as to allow partial or full axial rotation of the vacuum pipe  30  to the bent tube  23 , within the scope of this disclosure. 
     The sander  10  is equipped with a sanding pad  45 , as shown best in FIG. 2, that, as shown in FIGS. 3 and 4, is of a lesser length and width than the distances between the inner surfaces of housing end walls  14   a  and  14   b  and front and rear walls  13   a  and  13   b , leaving a space therebetween that allows for passage of a vacuum air flow pulled therearound. Which vacuum air flow will both turn the turbine  63 , will pick up sanding dust off of the surface being sanding and entrain that dust in the vacuum air flow, as discussed below. To provide sanding, the sanding pad  45  is fitted with a section of sanding material  46 , as shown in FIGS. 3 and 4, that is maintained thereto, preferrably with Velcro type fasteners, adhesive sections, or the like, and the sanding pad  45  is oscillated through an eccentric  72  that is turned by the turbine  63 , as set out below. 
     The sanding pad  45 , shown best in FIGS. 2,  3  and  4 , includes a stiff flat rectangular plate  47  having a front or outer face  47   a  arranged for releasably mounting sheets of sand paper, or other sanding material, thereover, and includes, mounted to the corner of a rear or inner face  47   b , as shown best in FIG. 3, identical spiders  48  that each having a head end  49  wherein a center hole is formed, and include like spaced straight legs  50  extending from around the head end  49  whose opposite ends are secured to the plate inner face  47   b  surface. Which legs  50  are preferably formed from a semi-rigid plastic, or other appropriate light weight stiff material, to flex so as to allow the sanding pad  45  to oscillate, so as to move orbitally, while supporting the pad against collapse when pressure is applied to force the sanding pad against a surface to be sanded. For mounting the sanding pad  45  to the sander body  11 , as shown in FIG. 2, screws  51  are each aligned for fitting through holes formed through the sanding pad  45 , preferrably at the corners thereof. With the holes each aligning to pass a screw  51  into a hole  49   a  formed through a spider end, as shown in broken lines in FIG. 4, and are turned into a pier  52  that is formed in to project from the bottom surface  12   a  of the flat top  12 , shown also in FIG.  2 . So arranged, with each of the spiders  48  each connected to a pier  52  at its head end  49 , the sanding pad  45  is suspended by the spider legs  50  to allow the sanding pad  45  to oscillate orbitally when moved by operation of the turbine  63  turning an eccentric  72 , as set out below. Which connection of the sanding pad  45  spiders to the undersurface  12   a  of the flat top  12  is a last step in the assembly process where the flat top  12  and sanding pad are fitted to the housing  11 , positioned within the walls  13   a ,  13   b ,  14   a  and  14   b , following the installation of the turbine and bearing assembly in the housing  11 , as set out herein below. 
     The housing  11  is preferably formed, as by molding, or like methods, to include air intakes or air inlet cavities  55  that are arranged in both ends of the housing  11 , and are to direct inlet air passing around the sanding pad  45  into inwardly sloping sections within the housing  11  that vent into a turbine chamber  56 , striking blades  80  of the turbine  63 . The inlet flows are of approximately the same volume, providing a balanced driving force that turns the turbine  63 . The air inlet cavities  55  are each formed in the housing along with the turbine chamber  56  that, as shown best in FIG. 3, is a cavity formed around a center stanchion  57  that projects upwardly from a chamber floor  58  that is formed across the housing interior and is spaced upwardly from where the sanding pad  45  is positioned. Which housing interior chamber floor  58  has the air inlet cavities  55  and a center hole  59  formed therein that an eccentric  72  is fitted in, as set out below. 
     The stanchion  57 , as shown in FIGS. 3 and 4, provides an inner turbine chamber wall  60 , is flat across its top surface  61  and includes a bearing cavity  62  formed through that top surface that extends downwardly to the chamber floor  58  center hole  59 . The bearing cavity  62  is to receiving a pair of like upper and lower turbine bearings  64  and  65  of turbine  63  that align to pass a turbine axle  66  journaled therethrough. To accommodate which upper and lower turbine bearings  64  and  65 , respectively, the bearing cavity  62  is stepped inwardly at  62   a  and  62   b , providing a ledge  62   c  therebetween, for maintaining bearing spacing, and whose opposite ends support each of the turbine bearings. 
     The turbine axle  66 , shown in FIGS. 3 and 4, includes a flat head end  67  and is threaded at its opposite end  68 . With the turbine axle passed through a center hole formed through center plates of both the turbine top and bottom sections  70  and  71  and has its lower threaded end  68  turned into a threated top end  73  of eccentric  72 . The axle head end  67  fits in a cup  69  that is formed as a raised section at the center of turbine top section  70  center plate  70   a , with the axle  68  to pass through the turbine lower section  71  center plate  71   a  of turbine  63  and is turned into the eccentric  72  top end  73 . The eccentric  72  is preferably a single unit formed with the threaded top end  73  wherein the turbine axle  66  threaded end  68  is turned, that extends upwardly at approximately a right angle from the center of a top surface of a disk  74  and includes an axle pin  75  that extends downwardly, at approximately a right angle, from the bottom surface of which disk  74  and is off-set from the disk center. The axle pin  75  is fitted into a bearing  76  that is maintained in a center cavity formed into the inner face  47   b  of the sanding pad  45 . So arranged, turning of the turbine  63  turns the turbine axle  66  that is coupled to the eccentric  72  top end  73  to turn the eccentric axle pin  75  that is journaled in the sanding pad  45  bearing  76 , thereby imparting an oscillating motion to the sanding pad that is moved along an orbital path, in turn, moving a sheet of sand material attached thereto over a surface that it is in contact with, sanding that surface. 
     The turbine  63  is a split design, formed in two sections, a lower of which sections  71  has a greater height than the height of the top section  70 . So arranged, the bearing assembly including the turbine axle bearings  64  and  65 , can be easily installed in the bearing cavity  62 , the top axle bearing  64  being dropped into the top end of the bearing cavity  62  sliding along the stepped section  62   a  to come to rest on the top lip of the ledge  62   c , with the lower axle bearing  65  to be fitted through the housing  11  open bottom center hole  59  to travel into the bearing cavity, sliding along the lower stepped section  62   b  to where its edge engages the bottom lip of ledge  62   c.    
     The turbine  63  is fitted, as shown in FIGS. 3 and 4, through the open top of housing  11  to rest on the top of the top surface  61  of the stanchion, with a hole through the collar  69  to receive the axle  66  fitted therethrough to where the axle top end  67  is nested in the collar  69 , and whereafter the eccentric  72  top end  73  threaded cavity is turned onto the turbine axle  66  threaded end  68 , securing the turbine  63  to the eccentric. Thereafter, with the sanding pad  45  bearing  76  seated in the bearing cavity  77  that is formed in the sanding pad inner face  47   b , the eccentric axle pin  75  is fitted into which bearing  76  and the sanding pad  45  and top  12  are installed to the body  11 , as set out above. 
     The turbine  63  is preferably formed from a hard plastic material, metal, or the like, as the described upper and lower turbine halves  70  and  71 , as shown in FIGS. 2,  3  and  4 , that are joined together as by an adhesive bonding, by welding, brazing, or the like, with the assembly then fitted, as shown best in FIG. 3, into the housing turbine chamber  56 . So arranged, the turbine top half rests on a top surface of center plate  71   a  of the lower turbine half  71 , and the top and bottom sections of turbine blades  80  are joined, as shown in FIGS. 3 and 4, along their contacting surfaces. So arranged, the blades  80  are spaced apart equal distances and are curved to each receive the inlet vacuum air flow at their forward edges  80   a  that travels therealong to their hub ends  80   b . The curve of which blades  80  is shown best in FIG.  2 A. The spacing distance between which blades  80  is shown as reducing from their inlet ends  80   a  to their exhaust ends  80   b.    
     In practice, an inlet vacuum flow is pulled around the sanding pad  45  to pass, as a balanced air flow, through the air inlet cavities  55  and into the turbine chamber  56  wherein the turbine  63  is journaled to upper and lower bearings  64  and  65 , with the turbine blades  80  receiving the air flow and reacting thereto by turning, to turn also the eccentric  72  that turns an off-set axle pin  75  fitted in a bearing  76  mounted in the sanding pad  45 . The sanding pad is thereby moved through an orbital path, sanding a surface. With the inlet vacuum air flow picking up sanding dust off from a working surface during its passage around the sanding pad  45 , that then passes through turbine ducts  17   a  and  17   b  to drive the turbine  63 , with that vacuum flow, with entrained dust collected therein, is then exhausted through the bent tube  23 , passing into the vacuum hose  30  and then to a collection container. 
     The vacuum air flow is, of course, contaminated with sanding dust that is entrained therein during its passage across the sanded surface and around the sanding pad  45  edges. A portion of such dust, in earlier sanders, has tended to find its way into the bearing assembly to, in short order, contaminate the bearings and greatly curtail turbine turning, thereby severely limiting the useful life of such sander and requiring, if possible, that the sander be taken apart and the collected dust removed from the bearings. The invention recognizes and solves this problem of dust contamination of the turbine bearings by effectively closing off access to the bearing cavity  62 . This is accomplished by the arrangement of the fitting of the turbine axle  66  head end  67  in the upper turbine half plate  70   a  collar  69  and turning of the axle threaded end  68  into the eccentric top end  73  so as to provide a tight clamping together of the upper and lower turbine halves plates  70   a  and  71   a . Thereby clamping the upper turbine bearing  64  between the undersurface of the lower turbine half plate  71   a  and the upper edge of the stepped section  62   c  of the bearing cavity. The lower turbine bearing  65  top edge is thereby clamped against the lower edge of the stepped section  62   c  and which bearing  65  has its lower edge held against the eccentric disk  64  top surface. So arranged, dust is discouraged from passage into the bearing cavity  62 . Further, and significant to the invention, to preclude dust travel into which bearing cavity  62 , a passage  85  is formed, as shown in FIG. 3, from a passage end  85   a  in the bearing cavity  62 , that is downwardly sloping through the stanchion  57  and then become a horizontal passage through the chamber floor  58 , and opens at opening  86  through the housing  11  front  13   a , as shown also in FIGS. 1,  6  and  8 . So arranged, the vacuum inlet flow through into the sander  10  creates less than ambient conditions within housing  11  and the bearing cavity  62 , causing an air flow to be pulled through a opening  86  in the housing wall  13   a  that travels through the passage  85  that is formed through the chamber floor  58  and slopes upwardly through the stanchion  57  and opens at  85   a  into the bearing cavity  62 . A positive pressure is thereby created within the bearing cavity  62  that blocks dust in the vacuum flow from traveling therein and provides air cooling to the bearings  64  and  64 . Additionally, this passage  85  can be used to pass oil, fed as drops into the opening  86 , that travel into the bearing cavity, to lubricate the turbine bearings  64  and  65 , providing bearing lubrication. Accordingly, by passing a clean air flow from without the sander into the bearing cavity  62  through passage  85 , and by a periodic introduction of oil through opening  86 , the sander  10  can enjoy a long and useful life. 
     A preferred embodiment of my invention in a low profile vacuum driven sander has been shown and described above. It will, however, be apparent to one skilled in the art that the above described embodiment may incorporate changes and modifications without departing from the general scope of the invention, which invention, it should be understood, is intended to include all such modifications and alterations in so far as they come within the scope of the appended claims and/or a reasonable equivalence thereof.

Technology Classification (CPC): 1