Abstract:
A pad sander skirt which flares out over the periphery of the sanding pad and which is coupled to a lower housing so that it swivels about the body of the sander. The skirt and lower housing can be selectively swivelled in a rotational manner to a position desired by the user. A further sander improvement disclosed relates to the protection of a user&#39;s hand. Palm-grip random orbit sanders are sometimes configured so that the sanding pad may begin spinning at high speed when the sander is lifted off of the work. To this end, the present application discloses a protective skirt which flares out over the periphery of the pad in a palm-grip random orbit sander. Also disclosed is an improved dust collection system comprising a filter housing formed of a rigid porous material for entrapping dust.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 08/613,147, filed Mar. 8, 1996 now U.S. Pat. No. 5,791,977. Application Ser. No. 08/613,147 is a continuation of application Ser. No. 08/334,855, filed Nov. 4, 1994, now U.S. Pat. No. 5,518,442. Application Ser. No. 08/334,855 was a continuation of application Ser. No. 08/009,309, filed Jan. 22, 1993, now abandoned. Each of these applications is incorporated herein by reference. 
    
    
     BACKGROUND AND SUMMARY OF THE INVENTION 
     The present application is directed to sander improvements. These improvements include a pad sander lower housing having a skirt which flares out over the periphery of the sanding pad. The lower housing can be selectively swivelled in a rotational manner to a position desired by the user. This has particular advantages in dustless versions of a sander in which it may be desirable to reposition the dust collection system. 
     A further improvement relates to the protection of a user&#39;s hand. Palm-grip random orbit sanders sometimes are configured so that the sanding pad may begin spinning at high speed when the sander is lifted off of the work. Since palm-grip random orbit sanders can be grasped by a single hand in a manner that might put the user&#39;s fingers in contact with a high speed spinning pad, protection against injury is desirable. To this end, the present application discloses a protective skirt which flares out over the periphery of the pad in a palm-grip random orbit sander. The skirt may be configured for either dustless versions of such sanders, in which case the skirt typically also forms a portion of the dust collection system, as well as with dusty versions of the sander, in which case the primary purpose of the skirt is to prevent contact of the user&#39;s hand and fingers with the pad. 
     In sanders with dust collectors, particularly those that use passive systems such as a cloth bag to catch dust, the dust collection apparatus can be both relatively cumbersome and ineffective. In an improvement to such passive systems, the present application discloses a sander dust collector filter housing formed of a rigid, porous material for entrapping dust. Such a dust collection system can be made in a compact manner which is particularly suitable for palm-grip sanders, whether the sander be of an orbital, dual action, or random orbit type. Larger versions of such filter housings may be used with larger sanders. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a sander which incorporates a dust collection system. 
     FIG. 1A illustrates a similar sander without a dust collection system. 
     FIG. 2 is a top view of a sander showing a dust collection system which can be rotationally oriented in a direction selected by the user. 
     FIG. 3 shows a cross-sectional view of a sander. 
     FIG. 4 illustrates a dust collection housing. 
     FIG. 5 illustrates a top plan view of a sanding pad which incorporates dust collection holes. 
     FIGS. 6A and 6B illustrate alternative embodiments of a sander back-up pad. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 illustrates a sander having a body or housing  20  which is typically comprised of two halves secured together by conventional means and a pad  22  for holding sandpaper or other abrasives or materials (e.g., polishing pads) desired by the user. Such pads  22  can be configured in the pressure sensitive adhesive (PSA) variety as well as a hook and loop variety, each of which are familiar to those skilled in the art, and can be either with or without holes to incorporate either a sander with dust collection capability (for example, as shown in FIG. 1) or without such capability (for example, as shown in FIG.  1 A). Pad  22  has an outer periphery substantially defining the size of sandpaper or other material supported by the pad. 
     The sander shown in FIGS. 1 and 1A have a body or housing  20  sized for a palm grip at the top of the housing and for a single-handed grip around the body. A motor housed by body  20  typically comprises an armature  24 , a field  26 , and brush and spring assemblies  28 . Upper and lower ball bearings  30  and  32  are supported by the housing and provide stability and smooth operation for motor shaft  34 . For a random orbit sander of the type shown, motor shaft  34  is typically directly coupled to a counterweight  36 , which may incorporate integral fan blades  37  used for dust collection. 
     In the embodiment shown, pad support  38  is coupled to counterweight  36  by a ball bearing  40  having its outer race diameter press fit into a cylindrical cavity  42  defined by pad support  38  and the inner diameter of its race slip fit onto an eccentrically-located cylindrical protrusion  44  of counterweight  36 . The connection between counter-weight  36  and pad support  38  imparts an orbital motion to the pad support  38 . Pad support  38  is shown further secured to armature shaft  34  by a machine screw  46 , which ensures a secure assembly of the counterweight  36 , bearing  40  and pad support  38 . Pad  22  is typically secured to pad support  38  by threaded machine screws  48 . 
     As has previously been indicated, the sander motor in the embodiment shown is powered electrically and for this purpose includes a power cord  50  with power being controlled by an on/off switch  53 . Those skilled in the art will recognize many other components illustrated in the cross-section of FIG. 3 as being typical to the assembly of an electrically-driven sander of a random orbit nature. Those skilled in the art will also recognize that suitable components of the sander shown could be replaced with well-know components if a sander of the orbital or dual-action variety is desired. Furthermore, in embodiments driven by an air motor, power cord  50  would be replaced by an air hose, and the components previously described which relate an electric motor would be replaced with suitable air motor components. Motors used in the preferred embodiments have typical no-load speed of 12,000 RPM. 
     For the preferred random orbit sanders shown in the present application, when a sander is not in contact with the work, the rotational restraint established between the inner race, balls, seals, grease, and the outer race of the bering  40  causes the pad assembly to spin at the same speed as the motor shaft. When the abrasive or other material mounted to pad  22  contacts the work, another rotational restraint is created which opposes the bearing restraint. This additional restraint varies with pressure, abrasive grade, etc. Through this process, the rotational speed of pad  22  (i.e., of the outer race of bearing  40 ) is reduced to approximately 300 RPM, while the orbital motion (inner race of bearing  40 ) continues at a higher speed (12,000 OPM). In this manner, since the rotational speed of the pad is not synchronized with the orbital motion of the pad, the abrasive particles are made to travel in a “random orbital motion.” 
     The sanders shown in the present application comprise a skirt  52  which flares out over the periphery  54  of pad  22 . As with housing  20 , skirt  52  is preferably formed of a rigid material (for example, polyamide) and is spaced slightly upward from pad  22 , giving pad  22  sufficient clearance from skirt  52  so that the sander can operate properly and so that dust can be pulled up between the periphery of pad  22  and skirt  52  by fan blades  37 . As previously indicated, fan blades  37  may be integrally formed in a central open region interior to counterweight  36 . 
     In the preferred embodiment, skirt  52  is formed integrally with a lower housing  56 , which is configured so that it can be selectively rotated about sander body  20  for enabling the lower housing to be oriented in a position desired by the user. The position selected by the user is typically maintained by friction between the exterior lower portion of the sander body  20  and the interior portion of lower housing  56 , each of which have complementary shapes to ensure retention of the lower housing on the sander body while enabling rotational adjustment. The ability to adjustably position lower housing  56  is particularly advantageous when lower housing  56  comprises a dust collection system defining a dust exhaust channel such as  58 . Such a dust exhaust channel may be coupled either to a passive dust collector such as a bag or filter housing  60  or by a hose to an active system such as a vacuum cleaner. In these scenarios, users may wish to adjust the position of the collection system with respect to sander or workpiece features. 
     As with body  20 , lower housing  56  may comprise two halves secured together by conventional means. For the version of the sander disclosed which incorporates dust collection, dust collection channel  58  is defined in part by a portion of lower housing  56 . FIG. 2, which is a top plan view of the preferred sander embodiment comprising a passive dust collection system, illustrates how lower housing  56  may be selectively swivelled in a rotational manner to a position desired by the user. As can be seen, such-positioning will enable the user to orient the direction of exhaust port  58  in a preferred direction relative to, for example, power cord  50 . 
     The preferred dust collection system is shown cross-sectionally in FIG.  4 . Note that the preferred system incorporates a membrane  62  which maintains a normally closed position in order to prevent the back flow of dust collected within filter  60  while enabling dust to enter the filter. Membrane  62  may be formed of polyester film having a nominal thickness of 0.007 inch. Filter housing  60  is typically coupled via friction fit to an adapter  64 , which in turn fits fictionally over dust exhaust channel  58  of housing  52  in order to removably interconnect the filter and adapter assembly with the sander exhaust port. O-ring  63  retained in place by a detent in adapter  64  helps maintain a good friction fit and seal for enabling long-life and easy removal of housing  60  from adapter  64 . When filter housing  60  is full of dust, it can be removed from adapter  64  and emptied by simply twisting housing  60  off of adapter  64  and tapping the filter housing briefly in order to empty it of dust. Note that, during this emptying procedure, membrane  62  preferably remains with adapter  64  and does not interface with emptying filter housing  60 . 
     In the preferred embodiment, filter housing  60  is formed by molding, sinterring or by other means a rigid, porous, plastic material, preferably porous polyethylene, polypropylene, polystyrene, or other polyolefins having a pore size effective to retain sanding dust; it has been found that a pore size of 120-140 microns is satisfactory. In the embodiment shown, filter housing  60  is substantially cylindrical and has an internal diameter of approximately two inches, a length of approximately four inches, and a typical wall thickness of 0.15 inch. Those skilled in the art will recognize that other sizes and shapes of sander filters consistent with the present filter invention may also be useful. An inherent characteristic of a filter housing constructed as described above is that the filter housing is non-collapsible. 
     In the sander embodiments shown, pads  22  are typically five inches in diameter and comprise an upper member  66  of fiberglass-reinforced epoxy molded into a lower member  68 , which may be formed of integral skin-cast polyurethane. As is familiar to those skilled in the art, for pads used with PSA, a vinyl sheet is typically applied to the lower surface  70  of lower pad member  68 . This vinyl material is normally coated such that PSA sandpaper or the like will stick to the surface and yet, when the paper is removed, little or not abrasive will be present on the vinyl sheet. Pads  22  are typically rated for 13,000 RPM. PSA pads with lower surface  70  formed of vinyl or similar material may include an embossed grain applied in a mold (a surface familiar to those skilled in the art used with pressure-sensitive adhesive for adhering materials such as abrasive sheets to the pad). Alternatively, lower surface  70  may be formed of short-stemmed hook and loop material applied in the mold (a surface likewise familiar to those skilled in the art for use in connection with abrasive sheets or the like backed with hook and loop material). 
     In prior-art sander configurations operating in the random orbit mode, pad  22  is typically free of rotational restraint such that pad  22  may achieve a very high RPM when the motor is running and the sander is lifted off of the work. In such situations, if lower member  68  of pad  22  is formed of typical prior-art materials such as cast polyurethane foam, the pad may expand radially outward. Radial pad expansion in this manner can cause a sanding sheet adhered to the bottom face  70  of the pad to be released when PSA is used to bond the abrasive sheet to the pad. This release of the adhesive sheet has been found to be caused by the differential movement in the interface between bottom surface  70  of the pad and the adjoining layer of the adhesive sheet, resulting in release by the PSA of the sanding sheet. Such released abrasive sheets can be inconvenient to the user. 
     Accordingly, it has been found that use of an anti-radial-expansion mechanism coupled proximate the lower surface  70  of sanding pad member  68  can substantially prevent radial expansion of the pad and substantially eliminate the problem of PSA bonding failures between the pad and the adhesive sheet. In one preferred embodiment, the anti-radial-expansion system is achieved by molding a layer  72  of vinyl-coated fiberglass insect screening into the lower portion of pad member  68 . Such insect screening may have a mesh of 18 by 16 strands per inch with a strand diameter of 0.011 inch. Other similar fiberglass screening or materials may also be used in order to prevent the previously described radial expansion problem. An alternative is use of a square-weaved cloth backing molded into the vinyl coating at the bottom of the pad. 
     Pads  22  are typically secured to pad support  38  by machine screws  48  passed through mounting holes  74  formed in upper fiberglass member  66 . In sanding pads which comprise vacuum holes  76 , the vacuum holes are preferably molded in and not machined. 
     At the time of filing the present application, preferred embodiments of the sanders disclosed can be obtained from Porter-Cable Corporation, the assignee of the present application, in three models. A model  332  does not incorporate dust collection and includes a PSA pad. A model  333  includes a dust collection system as well as a hook and loop pad. A model  334  is similar to the model  333  except that it incorporates a PSA pad. 
     The present invention is to be limited only in accordance with the scope of the appended claims, since persons skilled in the art may devise other embodiments still within the limits of the claims.