Abstract:
A pneumatic rotary tool including a housing and an output shaft projecting from the housing for transmitting torque to an object. An air motor drives rotation of the output shaft in the forward and reverse directions. Air passages extend from an air inlet to the motor for delivering pressurized air to the motor. A spring biases the lower portion of a valve within the air passage in a closed position, to restrict the flow of air through the air passage. The upper portion of the valve comprises a stem. When an operator squeezes a trigger on the pneumatic rotary tool, a deflector connected to the trigger deflects the stem to a first angularly deflected position, the valve thereby allows a relatively low rate of air flow to the motor for low-speed operation thereof. As the operator continues to squeeze the trigger, the stem is deflected to a second angularly deflected position, allowing a relatively high rate of air flow to the motor for high-speed operation thereof.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to a pneumatic rotary tool, and more particularly to an air inlet valve construction for such a tool. 
     The invention has been developed as an improvement on the pneumatic rotary tool disclosed in U.S. Pat. No. 5,918,686 issued Jul. 6, 1999, entitled Pneumatic Rotary Tool, incorporated herein by reference, hereinafter referred to as the &#39;686 patent. 
     In the tool disclosed in the &#39;686 patent, the flow of air to the air motor thereof is under primary control of a trigger-operated air valve (indicated at 65 in the &#39;686 patent), which is referred to in the patent as the primary air valve. Paraphrasing lines 37-45, column 7 of the patent, in using the tool the operator, using his index finger, squeezes the trigger to open the valve and the speed at which the tool operates depends on how far inward he pulls the trigger. While the tool has been generally satisfactory, inexperienced operators may encounter some difficulty in squeezing the trigger to attain and maintain a relatively low speed when that is needed for the work to be performed. 
     SUMMARY OF THE INVENTION 
     Accordingly, among the several objects of this invention may be noted the provision of a tool of the type shown in the &#39;686 patent improved to the extent of making it easier for the user to attain and maintain a low speed of the air motor, whereby the user may readily attain and maintain a particular low-speed setting or a high speed setting, as needed for the job at hand; the provision in the tool of valve means including the primary air valve of the &#39;686 patent invention for the dual stage speed purpose; the provision of a pistol-grip type of tool such as shown in the &#39;686 patent wherein the pull on the trigger controls the speed setting; and the provision of valve means for the stated purpose of economical construction and capable of economic assembly. 
     In general, a pneumatic rotary hand tool of this invention comprises a housing having an air motor therein, the housing having an inlet passage for flow of air to the motor for driving it and valve means for controlling the flow of air through the inlet passage. The inlet passage has an upstream facing valve seat, the valve means comprising members in the passage upstream of the seat one of which has a stem extending downstream therefrom past the seat. A spring biases said members in downstream direction to a closed position with respect to the seat. The stem extends generally axially in said passage in said closed position of said members. A deflector for the stem is operable by one holding the tool for deflecting the stem angularly from said generally axial position to a first angularly deflected position wherein said valve members establish flow of air to the motor at a relatively low rate for low-speed operation thereof and further to a second farther angularly deflected position wherein said valve members establish flow of air to the motor at a relatively high rate for high-speed operation thereof. 
     Other objects and features will be in part apparent and in part pointed out hereinafter. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a generally schematic vertical section of a pneumatic rotary hand tool similar to FIG. 2 of the &#39;686 patent but showing valve means in accordance with this invention instead of the valve indicated at 65 in the &#39;686 patent, the valve means being shown in off position wherein it completely blocks the flow of air; 
     FIG. 2 is an enlarged fragment of FIG. 1; 
     FIG. 3 is a view similar to FIG. 2 illustrating the valve means in a low-flow position; 
     FIG. 4 is a view similar to FIGS. 2 and 3 illustrating the valve means in a high-flow position; 
     FIG. 5 is an enlarged view with parts shown in section of an assembly per se of components of the valve means; and 
     FIG. 6 is a view generally in section on line  6 — 6  of FIG.  5 . 
    
    
     Corresponding reference characters indicate corresponding parts throughout several views of the drawings. 
     DETAILED DESCRIPTION 
     Referring to the drawings, first more particularly to FIG. 1, a pneumatic rotary hand tool having novel primary valve means of this invention is shown as comprising a pistol-like housing generally designated  1  having a pistol grip or handle  3  and a chamber  5  above the grip  3  in which reposes an air motor  7  for driving a shaft  9  for a tool (not shown) extending out of the chamber  5 . In the grip  3  is an air inlet passage designated  11  in its entirety for flow of air under pressure supplied thereto via a flexible hose (not shown) connected to a swivelling fitting  13  at the entrance end of the passage. At  15  is indicated a combination selector valve for selection of operation of the air motor  7  in forward or reverse direction and selection of the torque generated by the air motor. In the grip  3  alongside the inlet passage  11  is an air exhaust passage  17 . All this is essentially disclosed in the &#39;686 patent, to which reference may be had for details (not critical so far as the present invention is concerned). It is to be understood that the selector valve  15  and swivelling fitting  13  may be eliminated without departing from the scope of the present invention. The present invention involves the provision in the inlet passage  11  of the valve means designated in its entirety by the reference numeral  19 , replacing the primary air valve designated by the reference numeral  65  in the &#39;686 patent, said valve means  19  being trigger-operable as will be subsequently described. 
     The inlet passage  11  is formed by a lower counterbore  21  extending up from the lower end of the grip  3  more than half way up the grip to a second counterbore  23  of slightly smaller diameter than the lower counterbore, and a bore  25  extending up from the second counterbore having a relatively thin-walled tubular insert  27  secured in the bore  25  as by being press-fitted therein extending up from the upper end of the second counterbore. The upper end of the second counterbore and the lower end of the tubular insert define a upstream-facing (downward facing) shoulder  29 . A ring  31  is secured in the second counterbore  23  up against the shoulder  29 , as by being press-fitted in the second counterbore, said ring having an annular boss  33  projecting downwardly therefrom surrounding the central opening  35  in the ring (and the boss) constituting a relatively narrow annular valve seat. As shown, the opening  35  is very slightly less than the internal diameter of the tubular insert  27 . 
     The valve means  19  comprises in association with the valve seat  33  two valve members generally designated  37  and  39 , respectively in the inlet passage upstream of the seat  33 , one of which, namely the member  39 , has a stem generally designated  41  extending downstream therefrom through a central opening  43  in the other member, namely member  37 , through the central opening  35  in the bossed ring  31 , and up into the space  45  in the inlet passage  11  downstream of the ring  31  (the space in insert  27 ). A spring  47  biases the members  39  and  37  in downstream direction (in the direction toward the seat  33 ) to the closed position in which they are illustrated in FIGS. 1 and 2 wherein the stem  41  extends generally axially in downstream direction in the inlet passage  11 . At  49  is indicated a trigger-operated rod which constitutes a deflector for the stem  41  operable by one holding the tool for deflecting the stem angularly from its aforesaid generally axial position to a first angularly deflected (tilted) position such as that in which it is shown in FIG. 3 wherein the valve members  37  and  39  establish flow of air to the motor  7  at a relatively low rate for low-speed operation of the motor, and deflecting the stem farther to a second angularly deflected (tilted) position, such as that in which it is shown in FIG. 4, wherein the valve members establish flow of air to the motor at a relatively high rate for high-speed operation of the motor. 
     The valve member  39 , the one having the stem  41  extending downstream therefrom, comprises a disk  51 , preferably of sheet metal, having a downstream face designated  53  and an upstream face designated  55  (see FIG.  5 ). The stem  41  extends downstream from the downstream face  53  generally from the center thereof. Referring more particularly to FIG. 5, the stem  41  has a relatively short upstream portion  57  of circular cross-section immediately adjacent the disk  51 , a somewhat longer portion  59  of circular cross section and of larger diameter than portion  57  immediately downstream of (above) portion  57  forming an annular groove  61  around portion  57  between the lower end of portion  59  and the disk  51 . At the downstream (upper) end of portion  59  the stem  41  has an annular groove  63 . Downstream of the groove  63 , the stem has a tapered portion  65  widening in downstream direction from an upper relatively long portion  67  of circular cross-section of relatively small diameter. The diameter of the disk  51  is slightly less than the diameter of the counterbore  23 , the disk, in its closed position fitting somewhat loosely therein generally in a plane at right angles thereto. Referring more particularly to FIG. 6, the disk is shown as having a plurality (e.g. four) arcuate slots  69  extending on a circle adjacent its periphery constituting ports for flow of air as will be subsequently described. 
     The second of the two valve members, namely the member  37 , comprises a generally annular or ring-shaped member positioned between the downstream face  53  of the disk  51  and the valve seat  33 . This annular member  37  has the generally central opening  43 . The stem  41  extends downstream from disk  51  through this opening surrounding portion  59  of the stem, the opening  43  being of larger diameter than portion  59  to provide an annular passage  73  for flow of air upward around portion  59  as will be subsequently described. An O-ring  75  in groove  61  in the stem seals the upstream (lower) end of said passage  73  in the closed position of the valve members  37  and  39  in which they are shown in FIGS. 1 and 2 with the lower face  77  of member  37  in flatwise engagement with the upper face  53  of disk  51  and maintains the annular member  37  generally centered (i.e. coaxial) with respect to portion  59  of the stem. Annular member  37  is shown (FIG. 6) as having a main ring-shaped portion  79  of circular outline, the diameter of which is somewhat greater than that of valve seat  33 , with a plurality of radially outwardly extending projections  81 , e.g. four such projections at 90° intervals. 
     The spring  47  presses upwards on the disk  51  and thereby biases the disk downstream toward member  37  and, via the disk, biases member  37  toward the closed position of FIGS. 1 and 2 against the valve seat  33 . In detail, the upper face  53  of the disk engages the lower face  77  of member  37  and the upper face  82  of member  37  engages the seat. The stem  41  has a part  83  thereon spaced downstream of member  37  when the stem is in the generally axial position of FIGS. 1 and 2 (and FIG.  5 ), this part, which is constituted by a flat (e.g. sheet metal) ring or collar on the stem at the lower end of the taper having inwardly directed teeth  85  snapped into the groove  63  in the stem, having a function to be described. 
     The trigger-operated rod  49  extends from the trigger  87  of the tool across the exhaust passage  17  in openings indicated at  89  and  91  into the space  45  where its inner end is engageable with the stem  41  adjacent the upper end of the stem (the upper end of portion  67  of the stem). The trigger  87  is slidable in a cavity  93  in the forward side of the grip  3  adjacent the upper end of the grip. The forward end of the rod  49  is secured in the trigger as indicated at  95 . Forward (outward) movement of the trigger is limited by a stop  97 . Rod  49  is slidably guided in the openings  89  and  91 . Without pull on the trigger, as illustrated in FIGS. 1 and 2, the valve means  19  under the bias of spring  47  is held in the closed position wherein member  37  engages the seat  33  and the stem  41  is in a generally axial position extending generally centrally (axially) within the inlet passage  11 . The rod  49  is generally in position retracted from the stem  41 , having been pushed out to this position by the stem under the spring bias; thus the trigger  87  is in forward position determined by its engagement with the stop  97 . By pulling (squeezing) the trigger  87  to push the rod  47  inward a limited distance within a limited range, readily sensed by the user pulling the trigger, the rod (acting as a deflector for the stem  41 ) deflects the stem angularly (i.e. tilts the stem) from its generally axial position of FIGS. 1 and 2 to a first angularly deflected (tilted) position such as shown in FIG. 3 without moving member  37  away from the valve seat  33 . While part  83  (the flat collar) on the stem angles down toward the member  37 , it stops short of moving member  37 . However, on tilting of the stem  41  to said first angularly deflected position (which may be in the range from somewhat past the FIG. 2 position to the FIG. 3 position in which the collar  83  is contiguous to member  37 ), the disk  51  is angled down away from member  37 , opening up a relatively restricted path for flow of air at a relatively low rate through the ports  69  in the disk  51  to the space opened up between the downstream face  53  of disk  51  and the upstream face  77  of member  37 , thence through the annular space  73  and up around the flat collar  83 , the central opening  35  in ring  31  to the upper space  45  in the inlet passage  11 . The O-ring  75  moves down with disk  51  to open up space  73 . 
     By pulling (squeezing) the trigger  87  to push rod  49  farther inward than above described, the stem  41  is still farther angularly deflected (tilted) as shown in FIG. 4 resulting in part  83  (the flat collar) on the stem engaging and moving valve member  37  away from the valve seat  33  thereby establishing relatively high-rate flow of air through the inlet passage  11  to the motor  7 . The high-rate flow is generally via the ports  89  in disk  51  (and to some extent around the disk  51 ), thence through the spaces at the periphery of member  37  between projections  81 , around collar  83  and through the opening  35  in ring  31 . 
     In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained. 
     As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.