Abstract:
The orbital sander of the present invention eliminates many of the disadvantages of the prior art sanders by providing a compact, lightweight, and economical sander having a body and shroud formed from an injection-molded synthetic polymeric material. The head is replaced using a built-in plunger which engages notches in the spindle, without the need for tools. The built-in plunger enables the flexible shroud of the prior art to be replaced with a rigid polymeric shroud positioned with a minimal gap between the shroud and the head or shoe. The polymeric shroud is attached to the rest of the polymeric body structure by three screws and two pins. The pins project upwardly from the polymeric shroud and into precise engagement with the polymeric body structure, thus reducing the required drilling and tapping, providing rotational stability, and increasing the strength of the connection between the two parts. The air control valve is securely held in the housing using a set screw having a dog which engages a groove in the air control valve to resist the axial force tending to eject the air control valve from the body structure. Finally, a new muffler is used which creates a circuitous path for the exiting air, and thus dampens its acoustic energy.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application is based on provisional patent application serial No. 60/144,746. filed Jul. 20, 1999. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     Orbital abrading or polishing tools have been available for many years. Examples of such tools are presented in U.S. Pat. No. 4,592,170 to Hutchins, U.S. Pat. No. 4,660,329 to Hutchins, U.S. Pat. No. 4,671,019 to Hutchins, U.S. Pat. No. 4,839,995 to Hutchins, U.S. Pat. No. 4,986,036 to Hutchins, U.S. Pat. No. 5,445,558 to Hutchins, and U.S. Pat. No. 5,597,348 to Hutchins, all of which are incorporated by reference in their entirety into the present disclosure. 
     2. Description of the Related Art 
     Orbital sanders of the prior art have, in some instances, been shaped to be held by a user in manipulating the sander and moving it along a horizontal work surface to sand that surface. Such sanders often utilize a head which carries a sheet of sandpaper and is driven rotationally by a compressed air powered motor. The motor is usually contained within a rather heavy body structure. 
     Typically, the head is mounted to a spindle which in turn is mounted eccentrically relative to the vertical axis of the motor so that the head orbits about the vertical axis. It is often desirable to be able quickly and easily remove the head from the drive portion of the sander in order to enable selective use of any of several heads of different sizes and shapes with a single drive unit. A drive unit and a set of different heads can then serve, in effect, as a number of different tools. In the prior art, replacing the head has been relatively difficult because tools have typically been required for unscrewing the head from the drive portion of a sander. 
     Previously developed portable orbital sanders have utilized a flexible shroud to provide access for insertion of a tool between the head, which is also commonly referred to as a shoe, and the housing to lock the spindle so that the head can be unscrewed manually from it. Located within the shroud and just above the spindle is a rotating counterweight used to counterbalance the eccentrically mounted spindle and head. This arrangement has several disadvantages, however. First, the flexible shroud can be pressed inwardly by an operator&#39;s fingers until it contacts the rotating counterweight. This causes wear to the sander in addition to unwanted vibrations. Also, debris can enter the space between -the shroud and the head, and thus clog the inner workings of the sander, if the flexible shroud becomes distorted. Further, there is a risk that the fingers of the operator might enter the space, causing injury to the user. 
     Prior art sanders have used air control valves having rotatable cylindrical valve elements for regulating the supply of compressed air to the motor. However, in order to prevent the air pressure from ejecting the air control valve axially from the body structure, the air control valve has been secured in place within the body structure using such imprecise and makeshift methods as using a strap to hold the air control valve against the body structure. 
     After powering the motor, the compressed air must, of course, leave the sander. The escaping high pressure air creates a loud noise which can be harmful to the operator as well as those in the area. The noise level can be lowered by packing the output path with cotton or other materials, but this leads to the disadvantage of significantly greater back-pressure. 
     Prior orbital sanders have sometimes utilized a top cover secured to the body structure by screws passing downwardly through the cover and into threaded bores formed in the body structure. This method of securing the cover is disadvantageous and expensive, however, because it requires time-consuming drilling and threading of the body structure. 
     SUMMARY OF THE INVENTION 
     The orbital sander of the present invention eliminates many of the disadvantages of the prior art sanders by providing a compact, lightweight, and economical sander having a body and shroud formed from an injection-molded synthetic polymeric material. The head is replaced using a built-in plunger which engages notches in the spindle, without the need for tools. The built-in plunger enables the flexible shroud of the prior art to be replaced with a rigid polymeric shroud positioned with a minimal gap between the shroud and the head or shoe. The polymeric shroud is attached to the rest of the polymeric body structure by three screws and two pins. The pins project upwardly from the polymeric shroud and into precise engagement with the polymeric body structure, thus reducing the required drilling and tapping, providing rotational stability, and increasing the strength of the connection between the two parts. The air control valve is securely held in the housing using a set screw having a dog which engages a groove in the air control valve to resist the axial force tending to eject the air control valve from the body structure. Finally, a new muffler is used which creates a circuitous path for the exiting air, and thus dampens its acoustic energy. 
     To realize the advantages outlined above, one embodiment of the portable orbital abrading or polishing tool of the present invention includes: a tool body to be held and manipulated by a user; a motor carded by the body; an orbital drive structure driven rotatably about a first axis by the motor; a spindle having at least one notch along its outer circumference and which is connected to the orbital drive structure for rotation relative thereto about a second axis offset from the first axis to drive the spindle in an orbital path about the first axis as the orbital drive structure turns; a head threadedly connected to the spindle and adapted to carry an element for abrading or polishing a work surface; and a plunger passing through the body and movable radially inwardly, the plunger movable between a first position and a second position, wherein in the first position the plunger does not contact the outer circumference of the spindle and in the second position the plunger engages the at least one notch for any position of the spindle along the orbital path. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings, which constitute part of this specification, embodiments demonstrating various features of the invention are set forth as follows: 
     FIG. 1 is a side elevational view of a disclosed embodiment of an orbital sanding tool constructed according to the present invention; 
     FIG. 2 is a rear elevational view of the orbital sanding tool of FIG. 1; 
     FIG. 3A is a bottom plan view of the orbital sanding tool of FIG. 1 with its head or shoe removed to reveal the spindle and showing the plunger in its normal, retracted condition; 
     FIG. 3B is a bottom plan view of the orbital sanding tool of FIG. 1 with its head or shoe removed to reveal the spindle and showing the plunger engaging one of the notches even when the spindle is at the furthest point of its travel away from the plunger; 
     FIG. 4 is a horizontal cross-sectional view of the orbital sanding tool taken along the line  4 — 4  of FIG. 1; 
     FIG. 5 is a partial vertical cross-sectional view of a muffler of the sanding tool of FIG. 4 taken along the line  5 — 5 ; 
     FIG. 6 is a vertical cross-sectional view of the muffler taken along the line  6 — 6  of FIG. 5; 
     FIG. 7 is a vertical cross-sectional view, partially broken away, taken along the line  7 — 7  of FIG. 2; 
     FIG. 8 is an exploded perspective view of the body structure of the sanding tool of FIG. 1, showing how the top cover is secured to the main body section using lugs secured to a reinforcing plate embedded within the top cover; 
     FIG. 9 is an exploded perspective view of the body structure showing how the shroud is secured to the main body section using three screws and two pins; 
     FIG. 10 is a fragmentary vertical cross-sectional view of the orbital sanding tool showing a screw passing through the main body section to secure the top cover utilizing a lug embedded in the top cover; 
     FIG. 11 is a fragmentary partial vertical cross-section view of the orbital sanding tool showing the connection between the body structure to the shroud at the location of one of the attachment screws; 
     FIG. 12 is a fragmentary partial vertical cross-sectional view of the orbital sanding tool showing the engagement of the pin of the shroud with the inner wall of the main body section; 
     FIG. 13 is a fragmentary vertical cross-sectional view of the orbital tool showing the air control valve structure, including the set screw engaged in a groove formed in the shank of the air control valve, taken along the line  13 — 13  of FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Although detailed illustrative embodiments are disclosed herein, other suitable structures and machines for practicing the invention may be employed and will be apparent to persons of ordinary skill in the art. Consequently, specific structural and functional details disclosed herein are representative only; they merely describe exemplary embodiments of the invention. 
     The tool  10  shown in the drawings is an orbital sander having an injection molded body structure  12  which is shaped externally to facilitate its being grasped by a user to manipulate the sander and move it along a typically horizontal work surface  14  to sand that surface. An air driven motor  16  is contained within a main body section  18  of the body structure  12  (FIG.  1 ). Four lugs  20  are embedded in a top cover  22  of the body structure  12  (FIGS.  8  and  10 ). The top cover  22  is secured to the main body section  18  by screws  24  passed upwardly through holes  25  in the top of the main body section  18  and fastened to the lugs  20 . The top cover  22  is preferably covered by a cushion  26  of rubber, plastic or other resilient material by which the sander is held. The lower portion of the body structure  12  is made up of a skirt or shroud  28  attached to the main body section  18  (FIG.  9 ). The shroud  28  is held in place by three screws  30  extending upwardly through holes  32  in the shroud  28  and into tapped bores  34  in the main body section  18 . Further anchoring the shroud  28  to the main body section  18  are two pins  36  formed in the top of the shroud  28  and extending into engagement with the main body section  18 . 
     Referring specifically to FIG. 1, the air driven motor  16  acts through an orbital drive structure  38  to move an abrading pad, shoe or head  40  and an attached sheet of abrasive material (not shown) in an orbtial path about a first vertical axis  42  of the motor to sand the surface  14 . The orbital drive structure  38  includes a carrier part  44  which rotates about the first axis  42 . The orbital drive structure  38  also includes a spindle  46  mounted eccentrically to the carrier part  44  for free rotation about a second vertical axis  48  which is parallel to the axis  42  but offset slightly thereform. This gives the spindle  46  a desired orbital motion about the first axis  42 . An externally threaded screw  52  extends from the central axis of the head  40  for engagement with a threaded bore  50  disposed along the second vertical axis within the spindle  46 , enabling the head  40  to be detachably fastened to the spindle. 
     As illustrated in FIG. 3, the spindle  46  can be locked against rotational motion relative to the body of the orbital sander  10  by engaging a spring-loaded plunger  54  with notches  56  along the circumference of the spindle  46 . This enables the head  40  to be turned manually relative to the spindle  46  to withdraw the screw  52  from the threaded bore  50 , thereby removing the head  40 . 
     With reference again to FIG. 1, compressed air is supplied to the motor  16  through a manually actuable valve  58 . A separate air control valve  60  is rotatable within the body structure  12  for adjustment of the flow of pressurized air through the tool. In order to prevent the air control valve  60  from being ejected axially from the body structure  12 , the air control valve  60  is held in place within the body structure  12  by a set screw  62 . The set screw  62  can be a full dog Allen screw wherein the dog end tip  64  engages a groove  66  formed within the air control valve shank  69  (FIGS.  7  and  13 ). 
     After driving the motor  16 , the compressed air leaves the orbital sander  10  through a silencer, filter, or muffler  68  in order to provide quieter operation. The muffler  68  creates a circuitous path for the exiting air to travel, and thus dampens the acoustic energy of the air (FIGS.  4 - 6 ). 
     Proceeding now with a more detailed description of certain specific features of the present invention, FIGS. 3A and 3B illustrate the manner in which the spring plunger  54  locks the spindle  46  for replacing the head  40 . The tool operator applies pressure to the plunger  54  in order to move it radially inwardly toward the first vertical axis  42  and into engagement with the notches  56  along the circumference of the spindle  46 . Because the vertical axis  48  of the spindle  46  orbits about the first vertical axis  42 , the outer circumference of the spindle  46  will at some points in its orbital path be relatively close to the plunger  54  and at other points be further from the plunger  54 . The plunger  54  is dimensioned and arranged so that when it is in its first, released position it does not contact the spindle  46 , even when the spindle  46  is at the location in its orbital path at which it is closest to the plunger  54 . At the same time, the plunger  54  is designed to extend approximately 40 mils (0.040 inches) into the notches  56  when the spindle  46  is at the location in its orbital path at which it is furthest from the plunger  54  and when the plunger  54  is fully compressed. FIG. 3A shows the spindle  46  when it is closest to the plunger  54 . From the figure, it can be seen that in the first released position, the plunger  54  clears the outer circumference of the spindle  46 . Dashed lines  71  show how the plunger  54  engages the notch  56  when compressed in the direction of arrow  73 . FIG. 3B shows the spindle  46  when it is furthest from the plunger  54 , with the plunger  54  fully compressed to a second position. In this position, the plunger  54  is still able to engage the notch  56 . 
     When it is desired to replace the head  40 , the plunger is depressed in the direction of the arrow  73  until the end of the plunger contacts the spindle  46 . The head or shoe  40  is then manually turned with the user&#39;s other hand until the plunger enters one of the notches  56 , thus locking the spindle  46  against further rotation. Now the head  40  can be spun while the spindle  46  remains in place, thereby unscrewing the screw  52  from the threaded bore  50  until the head  40  is separated from the spindle  46 . A new head  40  can then be installed by reversing the method. 
     The spindle locking method described above enables quick and easy replacement of the head  40  without tools. Thus, the orbital sander  10  can be used with different heads to serve, in effect, as a number of different tools. Further, this method permits the shroud  28  to be rigid and yet to be very close to the upper surface of the head. There is no need for a flexible shroud or a large gap because tools need not be introduced beneath the shroud to lock the spindle in place. 
     It is desirable to make the hand-held orbital sander  10  economical as well as light weight for easy handling. In order to achieve these goals, the body structure  12  is injection molded of a suitable synthetic polymeric material. For example, #6 nylon with 38% glass fiber can be used. As illustrated in FIG. 9, the polymeric main body section  18  is attached to the polymeric shroud or skirt  28  to form the body structure  12 . The shroud  28  is formed separately from the main body section  18  so that the shroud  18  can be replaced easily for use with heads  40  of different sizes. For example, a 3-inch diameter shroud can be used with a smaller head and a 5 or 6-inch diameter shroud can be used with larger heads. The shroud  28  is secured to the main body section  18  by means of the three screws  30  extending upwardly through the holes  32  in the shroud  28  and into the tapped bores  34  of the main body section  18  (FIG.  11 ). Further securing the shroud  28  to the main body section  18  are the two pins  36  formed in the top of the shroud  28  and extending into engagement with an internal angular portion of the main body section  18 . The two pins  36  can engage the inner wall of the main body section  18  as shown in FIG. 12, or alternatively, holes can be formed in the main body section  18  for receiving the two pins  36 . Utilizing the pins  36  reduces the number of screws needed and thus reduces the required tapping and threading of the shroud  28  and the main body section  18 . Also, in order to drill and tap into the walls, the walls must be thicker, thus increasing the weight of the sander. Using fewer screws and thinner walls thus reduces the weight of the sander. Further, in order to avoid warping of the thin shroud walls upon cooling of the shroud  28 , it is important that the walls have uniform thickness. Utilizing the two pins  36 , rather than using extra screws, allows for greater uniformity of wall thickness and thus decreases warpage. Strength is also a consideration when using polymeric materials. Utilizing the pins significantly increases the strength of the joint between the shroud  28  and the main body section  18 , thus reducing breakage and increasing reliability. Further increasing the strength of the joint is the lip and groove arrangement formed in the connecting edges of the main body section  18  and the shroud  28  (FIGS. 9,  11  and  12 ). 
     As illustrated in FIGS. 8 and 10, four lugs  20  are affixed to the corners of a metal plate  69  embedded within the top cover  22  of the body structure  12 . The top cover  22  is secured to the main body section  18  by passing screws  24  upwardly through holes  25  in the top of the main body section  18  and fastening the screws into the lugs  20 . Sheet metal nuts or other commercially available hardware can also be used so long as they have inside threads for matching with the threads on the outside of the screws  24 . This method saves time and expense by requiring significantly less drilling and tapping than prior art methods in which a top cover is secured to a body structure utilizing screws passing downwardly through the top of the cover and into threaded bores in the body structure. Further, by passing the screws  24  upwardly into the lugs  20 , the screws  24  can conveniently be used to support the motor  16  in the main body section  18  as shown in FIG.  10 . 
     Referring to FIGS. 1,  2  and  4  together, air is supplied to the motor  16  from a source of compressed air through a line connecting into a rearwardly projecting portion  70  of the body structure  12 . From this inlet, air flows through a passage  72  in the portion  70  to a vertical bore  74  containing the manually actuable valve  58 . The valve  58  is normally spring urged to its closed position and is adapted to be opened by downward movement of an actuating handle  76  attached pivotally at  78  to the body structure  12  (FIG.  7 ). The air control valve  60  can be rotated to adjust the degree of alignment between the passage  72  and an entrance hole  79  in the wall of the control valve  60 . Greater alignment of the holes provides increased air flow while blockage of the passage  72  can shut off the air flow. Thus, depression of the handle  76  by an operator admits air from the passage  72  to a passage  80  leading to the motor  16 , commencing operation of the motor and orbital movement of the head  40 . Air discharged from the motor is exhausted to the atmosphere through an outlet passage  82  and the muffler  68  (FIG.  4 ). 
     As illustrated in FIG. 7, the air control valve  60  is seated in the vertical bore  74  with O-rings providing an airtight seal to keep pressurized air from escaping. In order to prevent the air pressure from ejecting the air control valve  60  axially from the body structure  12 , the valve is held in place within the body structure  12  by the set screw  62 . As shown in FIG. 4, after powering the motor  16 , exhaust air leaves the orbital sander  10  through the muffler  68  in order to provide quieter operation. The muffler  68  is seated in a bore  94  with O-rings  96  providing an air tight seal to assure that the compressed air passes through the muffler  68 . FIGS. 4-6 show how the muffler  68  creates a circuitous path for the exiting air to travel, and thus dampens the acoustic energy contained within the air. Exiting air first passes from the outlet passage  82  into a first internal channel  86  of the muffler  68 . The first internal channel  86  is blocked off by a barrier  88 , which causes the air to pass through holes  90  in the muffler walls  92 , and into a first outer chamber  96  between muffler walls  92  and the-bore  94 . Next, the air passes through notches formed in a portion of the barter  88  extending into the outer chamber and passes into a second outer chamber  98  between the muffler walls  92  and the bore  94 . The air then passes through holes  90  in the muffler walls  92  and back into a second internal channel  100  of the muffler  68 . From there it passes into a widened internal channel  102  and is exhausted to the atmosphere through the holes  104 . The circuitous path taken by the air substantially reduces axial and radial fluctuations within the air flow, thereby dampening its acoustic energy. 
     The present invention is not meant to be limited in use to sanding. Instead, it can be used for any sort of abrading or polishing by using abrading or polishing sheets or pads with the head or shoe  40 . The head or shoe  40  itself can also be designed to abrade or polish without any abrading or polishing sheets or pads attached. 
     While the above description contains many specific features of the invention, these should not be construed as limitations on the scope of the invention, but rather as an example of one preferred embodiment thereof. Many other variations are possible. Accordingly, the scope of the invention should be determined not by the embodiments illustrated, but by the appended claims and their legal equivalents.