Abstract:
Apparatus and methods for thrust sensing valves are disclosed. In one embodiment, an apparatus includes a housing including an input port and an output port and further having a mounting portion adapted to be coupled to a manufacturing tool. A supply member is operatively coupled to the housing to provide a flow of the pressurized medium into the input port of the housing. Finally, an elongated body is operatively coupled to the housing and moveable along an axis between a first position corresponding to a first pressure output from the housing and a second position corresponding to a second pressure output from the housing. The elongated body is biased into the first position and moveable into the second position in the presence of a thrust force on the mounting portion.

Description:
FIELD OF THE INVENTION 
   The present disclosure relates to apparatus and methods for thrust-sensing valves, and more specifically, to valves that automatically retract a drilling device when thrust goes to zero. 
   BACKGROUND OF THE INVENTION 
   Typically, the stroke of power feed drilling equipment is adjusted for the maximum material thickness in the area drilled. This results in excessive cycle time drilling holes through the thinner materials in that area. In addition, to accommodate material thicknesses that vary to a greater degree, production frequently has to set-up multiple pieces of power feed drilling equipment that are identical except for stroke adjustment. This situation results in the need for additional power feed drill motors and additional time to set-up and control those drill motors. Thus, a need exists to reduce the waste and inefficiency associated with such fixed-stroke drilling apparatus. 
   SUMMARY OF THE INVENTION 
   The present invention is directed to apparatus and methods for thrust-sensing valves, and more specifically, to valves that automatically retract a drilling device when thrust goes to zero. Apparatus and methods in accordance with the present invention may advantageously sense when a hole has been completely drilled through a workpiece, and automatically retract to a starting position. In this way, drill cycle times for areas with varying material thicknesses may be optimized. Also, the need to adjust and document the stroke for power feed drilling equipment will be eliminated, as well as the need for multiple drill motor set-ups for areas with a wide range of material thicknesses. 
   In one embodiment, a thrust sensing valve assembly includes a housing including an input port and an output port and further having a mounting portion adapted to be coupled to a manufacturing tool. A supply member is operatively coupled to the housing to provide a flow of a pressurized medium into the input port of the housing. Finally, an elongated body is operatively coupled to the housing and moveable along an axis between a first position corresponding to a first pressure output from the housing and a second position corresponding to a second pressure output from the housing. The elongated body is biased into the first position and moveable into the second position in the presence of a thrust force on the mounting portion. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The preferred and alternative embodiments of the present invention are described in detail below with reference to the following drawings. 
       FIG. 1  is side elevational view of a drill assembly having a thrust-sensing valve in accordance with an embodiment of the present invention; 
       FIG. 2  is an enlarged side elevational view of a thrust valve assembly coupled to a drill chuck of the drill assembly of  FIG. 1  in accordance with another embodiment of the invention; 
       FIG. 3  is an isometric view of the thrust valve assembly of the drill assembly of  FIG. 1  in accordance with yet another embodiment of the invention; 
       FIG. 4  is an exploded side elevational view of the thrust valve assembly of  FIG. 3 ; 
       FIGS. 5   a ,  5   b , and  5   c  are side elevational views of the drilling assembly of  FIG. 1  performing various stages of a drilling operation on a workpiece in accordance with an embodiment of the invention; 
       FIG. 6  is a schematic view of a 4-way valve assembly of a drilling assembly in a first operating condition in accordance with yet another embodiment of the invention; 
       FIG. 7  is a schematic view of the 4-way valve assembly of  FIG. 6  in a second operating condition in accordance with an embodiment of the invention; 
       FIG. 8  is a schematic view of the 4-way valve assembly of  FIG. 6  in a third operating condition in accordance with an embodiment of the invention; and 
       FIG. 9  is a schematic view of the 4-way valve assembly of  FIG. 6  in a fourth operating condition in accordance with an embodiment of the invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The present invention relates to apparatus and methods for thrust-sensing valves, and more specifically, to valves that automatically retract a drilling device when thrust goes to zero. Many specific details of certain embodiments of the invention are set forth in the following description and in  FIGS. 1–9  to provide a thorough understanding of such embodiments. One skilled in the art, however, will understand that the present invention may have additional embodiments, or that the present invention may be practiced without several of the details described in the following description. 
     FIG. 1  is side elevational view of a drill assembly  100  having a thrust-sensing valve  110  (partially shown) in accordance with an embodiment of the present invention. In this embodiment, the drill assembly  100  also includes a drive motor  102  coupled to a drill chuck  104 . A drill bit  106  is coupled to the drill chuck  104 . As described more fully below, the drilling assembly  110  equipped with the thrust-sensing valve  100  may advantageously sense when a hole has been completely drilled through a workpiece, and will automatically retract the drill bit to its starting position. 
     FIG. 2  is an enlarged side elevational view of the thrust valve assembly  110  coupled to the drill chuck  104  of  FIG. 1 .  FIG. 3  is an isometric view of the thrust valve assembly  110  of  FIG. 2 . The thrust valve assembly  110  includes a needle valve  111  operatively coupled to a supply gland  112 , and a threaded end  114  that threadedly couples to the drill chuck  104  ( FIG. 2 ). The supply gland  112  is coupled to a supply line  113  that is, in turn, coupled to a source of a pressurized medium  101  ( FIG. 1 ), such as and air pump, a pressurized vessel, shop air, or any other suitable source. 
     FIG. 4  is an exploded side elevational view of the needle valve  111  of the thrust valve assembly  110  of  FIG. 3 . In this embodiment, the needle valve  111  includes an outer valve housing  116  and an inner needle body  118  that, in an assembled position, is slideably disposed within the outer valve housing  116 . A spring  120  is disposed about the inner needle body  118 . As further shown in  FIG. 4 , a pair of pins  122  are longitudinally disposed in longitudinal keyways  123  disposed in the inner needle body  118  and corresponding longitudinal keyways  117  disposed in the outer valve housing  116 . An aperture  119  is also disposed through the outer valve housing  116 . A snap ring  124  secures the components of the thrust valve assembly  110  together. 
   Operationally, drilling torque is transmitted through the sliding, spring-loaded thrust valve assembly  110  by equipping the outer valve housing  116  and the inner needle body  118  with the longitudinal keyways  123 ,  117 . As the outer valve housing  116  and the inner needle body  118  are assembled, the pins  122  are inserted into the keyways  123 ,  117 . During a drilling operation, torque is transmitted from the outer valve housing  116  through the pins  122  to the inner needle body  118  without interfering with the movement necessary for the thrust valve assembly  110  to operate. 
   It will also be appreciated that a pressurized medium (e.g. air or other suitable pressurized medium) is supplied to the needle valve  111  via the supply gland  112 . The supply gland  112  is equipped with O-ring seals (not visible) that engage between an inner surface of the supply gland  112  and an outer surface of the outer valve housing  116  to minimize pressure losses. In one embodiment, snap rings may be used to maintain the position of the supply gland  112  on the outer valve housing  116 . As best shown in  FIG. 3 , the supply gland  112  includes an anti-rotation lug  115  that projects outwardly and fits through an opening  103  of a drill motor nosepiece  105 , as shown in  FIG. 1 , providing a location for coupling the supply gland  112  with the supply line  113 . 
     FIGS. 5   a ,  5   b , and  5   c  are side elevational views of the drilling assembly of  FIG. 1  performing various stages of a drilling operation on a workpiece  502  in accordance with an embodiment of the invention. In this embodiment, a feedback line  513  is coupled between the needle valve assembly  111  and a control valve  510  of a drive unit  520  of the drill assembly  100 . 
   In  FIG. 5   a , the drilling assembly  100  is shown in a first (or initial) position  504  prior to engagement with the workpiece  502 . The needle valve assembly  111  is biased by the spring  120  into an open position such that a pressurized medium from the supply line  113  enters the supply gland  112 , flows through the aperture  119  and through the feedback line  513  to the control valve  510 . The control valve  510  is in an advance position A such that the drive unit  520  advances the drill bit  106  toward the workpiece  502 . 
   As shown in  FIG. 5   b  in a second (or engaged) position  506 , the drill bit  106  is engaged with the workpiece  502 . The needle valve assembly  111  senses the thrust of the drill assembly  100  against the workpiece  502 , and the spring  120  compresses, moving the inner needle body  118  into a forward position such that the aperture  119  is blocked, thereby dropping the pressure within the feedback line  513  The control valve  510  senses the pressure drop within the feedback line  513  and remains in the advance position A, maintaining the drive unit  520  in the advance mode of operation and performing a drilling operation on the workpiece  502 . 
   Finally, as shown in  FIG. 5   c , in a third (or breakthrough) position  508 , the drill bit  106  has broken through the workpiece  502 , removing the thrust (or compression) force on the needle valve assembly  111  and allowing the spring  120  to re-expand, withdrawing the inner needle body  118  back from the aperture  119  and returning the needle valve assembly  111  to the open position. 
   It will be appreciated that a variety of embodiments of control valves  510  and drive units  520  may be conceived, and that the invention is not limited to the particular embodiment described above and shown in  FIGS. 5   a ,  5   b , and  5   c . For example, in one particular embodiment, the control valve  510  may be a 4-way pneumatic valve used in conjunction with the thrust sensing valve  110  to operate an internal spool valve that controls a drill and retract cycle of a power feed drill motor, such as the PAR-A-MATIC® series of pneumatic self-feed drill motors commercially available from Ingersoll-Rand Fluid Products of Bryan, Ohio. In this embodiment, the spool valve shifts to the feed and retract positions as air is exhausted on each side of the valve. Exhaust ports of the spool valve may be coupled to the 4-way control valve such that when the 4-way control valve is manually shifted to an advance, position A by an operator, air (or other pressurized medium) is exhausted from a “feed” side of the spool valve and the drill motor advances. At this time, a metered air supply is being sent to the thrust sensing valve  110 . The thrust sensing valve  110  air supply line  113  may also be connected to an air pilot on the 4-way valve so that when the drill starts to penetrate the material closing the thrust sensing valve  110 , a back pressure is built up causing the 4-way valve to shift back to its original position B. In position B, the “retract” side of the spool valve is connected to the thrust sensing valve  110 . When the drill bit (or other tool)  106  exits the back side of the workpiece, opening the thrust sensing valve  110 , the air is exhausted from the “retract” side of the spool valve causing the drill motor to retract. 
   More specifically,  FIG. 6  is a schematic view of a 4-way valve assembly  600  of a drilling assembly  602  in a first operating condition  610  in accordance with yet another embodiment of the invention. The drill motor  604  of the drilling assembly  602  is in an initial starting position  606  with the drill bit  106  fully retracted away from the workpiece  502  ( FIG. 5   a ). In this initial starting position  606 , the drill motor  604  is in a “retract” position or mode as air exhausts out of a retract port  608 . As shown in  FIG. 6 , the thrust valve assembly  110  ( FIGS. 2 and 3 ) is operatively coupled to the 4-way valve assembly  600  and is initially in a closed position. 
   Next,  FIG. 7  shows the 4-way valve assembly  600  of  FIG. 6  in a second operating condition  612  after an operator or controller (not shown) has commanded the drill motor  604  to begin drilling. The 4-way valve assembly  600  has now shifted to the second operating condition  612 , with the drill motor  604  in the advance or drill position as air exhausts out of a drill port  609  of the drill motor  604 . In the second operating condition  612  shown in  FIG. 7 , the drill bit  106  has not yet contacted the workpiece  502  ( FIG. 5   a ), and the thrust valve assembly  110  remains in the closed position. 
     FIG. 8  shows the 4-way valve assembly  600  of  FIG. 6  in a third operating condition  614 . As the drill bit  106  contacts the workpiece  502  ( FIGURE 5   b ), the thrust valve assembly  110  moves to an open position. Air pressure at a second air pilot  14  is now greater than an air pressure at a first air pilot  12 , causing the 4-way valve assembly  600  to shift to the third operating condition  614 . As shown in  FIG. 8 , in the third operating condition  614 , air exhausts out of both the drill and the retract ports  609 ,  608  of the drill motor  604 . The drill motor  604  remains in the drill or advance position, and continues to advance the drill bit  106  into the workpiece  502  ( FIG. 5   b ). 
   Finally,  FIG. 9  shows the 4-way valve assembly  600  in a fourth operating condition  616 . In the fourth operating condition  616 , the drill bit  106  has broken through the back side of the workpiece  502  ( FIG. 5   c ). The thrust valve assembly  110  returns to the closed position, and air exhausts out of the retract port  608  of the drill motor  604  only. The drill motor  604  then returns to the initial retract position, automatically withdrawing the drill bit  106  back away from the workpiece  502  ( FIG. 5   a ). The drill assembly  602  may then be re-positioned over another location of the workpiece  502 , and the operation repeated. 
   Apparatus and methods in accordance with the present invention may provide significant advantages over the prior art. As described above, manufacturing assemblies equipped with the thrust-sensing valve may advantageously sense when a hole has been completely drilled through a workpiece, and will automatically retract to a starting position. In this way, drill cycle times for areas with varying material thicknesses may be optimized. Also, the need to adjust and document the stroke for power feed drilling equipment will be eliminated, as well as the need for multiple drill motor set-ups for areas with a wide range of material thicknesses. 
   While various preferred and alternate embodiments of the invention have been illustrated and described, as noted above, many changes can be made without departing from the spirit and scope of the invention. Accordingly, the scope of the invention is not limited by the disclosure of the preferred embodiment. Instead, the invention should be determined entirely by reference to the claims that follow.