Abstract:
A portable drill apparatus combines an air motor that drives a drill chuck in rotation, a linear actuator that drives the air motor and the drill chuck in linear reciprocating movements, and an electric motor that operates the linear actuator. The drill chuck, air motor, linear actuator, and electric motor are all connected together, end to end, enabling the apparatus to be easily manually transported and positioned. A separate programmable controller communicates with the electro-pneumatic drill apparatus and controls the operation of the apparatus to perform peck feed drilling on layers of different materials, and power feed drilling to drill and countersink to controlled depths.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     (1) Field of the Invention  
         [0002]     The present invention pertains to a portable drill apparatus that combines an air motor that drives a drill chuck in rotation, a linear actuator that drives the air motor and the drill chuck in linear reciprocating movements, and an electric motor that operates the linear actuator. The drill chuck, air motor, linear actuator, and electric motor are connected together, end to end, enabling the apparatus to be easily manually transported and positioned. A separate programmable controller communicates with the electro-pneumatic drill apparatus and controls the operation of the apparatus to perform a peck feed drilling process on layers of different materials, or a power feed drilling process to drill and countersink holes into layers of materials to controlled depths.  
         [0003]     (2) Description of the Related Art  
         [0004]     In the manufacturing of large structural bodies that are required to have a large degree of structural strength, for example in the manufacturing of aircraft, it is often necessary to drill precisely dimensioned fastener holes through multiple layers of materials having different degrees of hardness. For example, it is often necessary to drill through multiple layers of materials that include a combination of hard and soft materials, such as a composite material and titanium, or a composite material and aluminum. In order to prevent the chips of the harder materials produced by the drilling from eroding the softer materials and causing an oversized hole condition, a peck feed drilling process is often employed.  
         [0005]     The peck feed drilling process through multiple layers of different types of materials involves controlling incremental movements of the drill bit. The drill bit movement is controlled to drill into a small amount of the material at a time (typically about 0.033 inches), and then to react the drill bit from the drilled hole. The drill bit is retracted back to its starting position to remove the chips of the material drilled from the hole. This “peck” cycle is repeated numerous times, each time drilling the hole a small amount deeper and removing the drilled chips, until the hole is produced completely through the layers of material. This gives a very consistent and precise hole diameter through the multiple layers of material.  
         [0006]     Peck feed drilling is a very useful process when drilling multiple layers of different materials. However, prior art apparatus that are available for performing the peck feed drilling process have been a source of numerous problems. Prior art peck feed drilling equipment typically employs a pneumatic air motor that drives a spindle which, in turn, drives the drill bit in rotation. In addition to the first air motor that drives the spindle, a second air motor in the form of an air cylinder and piston is attached to the rear of the first air motor. The second air motor is operative to move the first air motor and the drill bit spindle forwardly in pecking away portions of the drilled hole, and to retract the air motor and drill bit spindle rearwardly after each pecking movement.  
         [0007]     An extensive network of pneumatic couplings and hoses is needed to control the rotation of the first air motor and the linear reciprocating movements of the second air motor during the peck feed drilling process. The pneumatic couplings and hoses are a part of an extensive air logic circuit that includes numerous valves, couplings, and air lines that control the drilling rotation of the first air motor and the pecking reciprocating movements of the second air motor. A substantial framework is needed to support the drilling apparatus and the pneumatic air logic circuit that controls the operations of the two air motors.  
         [0008]     The complexity of operating the two air motors and controlling the movements of the two air motors through the operation of the numerous valves of the extensive air logic circuit makes it very difficult to adjust the operation of the two air motors to the desired drill process parameters (i.e., the feed rate of the drill bit, the peck rate of the drill bit, the setback for retracting the drill bit, etc.). The complex nature of the two drill motors and their extensive air logic circuit also makes it difficult to repair the motors and air logic circuit, and also contributes to a frequency of malfunctioning of the motors and the air logic circuit during use. Consequently, this type of manufacturing equipment is very expensive to purchase, is very expensive to maintain, and is very expensive to use.  
         [0009]     The same problems exist in power feed drilling equipment that is used in drilling holes and producing countersinks in multiple layers of different materials. This type of drilling process requires precise controlling of the feed rate of the drill bit and the countersink cutter to a controlled depth in the different layers of material, controlling the dwelling of the drill and countersink cutter at the controlled depth for a fixed amount of time, and controlling the retraction of the drill and countersink cutter from the drilled hole and countersink. The prior art equipment of this type has also required a complex air logic circuit to control the movements of the drill bit and the countersink cutter and their dwell times. Consequently, this type of prior art pneumatic power feed drilling equipment is also prone to the same types of problems associated with the prior art pneumatic peck feed drilling equipment.  
       SUMMARY OF THE INVENTION  
       [0010]     The apparatus of the invention overcomes the problems associated with the complex air logic circuits employed in prior art peck feed drilling and power feed drilling equipment by providing a portable electro-pneumatic drill apparatus that uses a programmable linear motion actuator to electronically control the travel of the drill bit spindle and the pneumatic air motor that rotates the spindle.  
         [0011]     The portable electro-pneumatic drill apparatus of the invention employs the combination of an air motor and an electric motor in controlling the rotation of a drill bit chuck, and the reciprocating movements of the drill bit chuck. The combination of the air motor and the electric motor provides the apparatus of the invention with a compact construction that is portable and can be easily manually positioned for drilling operations. In addition, the combination of the air motor and the electric motor in the apparatus significantly simplifies the control system required for the apparatus.  
         [0012]     The entire construction of the apparatus is made up of known components arranged in the novel combination and configuration. The components of the apparatus are assembled together, end to end, along a center axis of the apparatus, which facilitates the manual portability of the apparatus.  
         [0013]     The apparatus is provided with an adjustable drill bit chuck at one end. The chuck is conventional, and is adjustable to securely and removably hold a variety of different size drill bits.  
         [0014]     The chuck is supported in the interior of a nosepiece housing. The nosepiece housing basically supports the chuck for rotary movement, and for axial reciprocating movements of the chuck through the nosepiece housing interior.  
         [0015]     An air motor housing is connected to the nosepiece housing. The air motor housing has a hollow interior bore that extends axially through the housing.  
         [0016]     An air motor is mounted in the air motor housing for axial reciprocating movement of the air motor through the air motor housing interior bore. The air motor is operatively connected to the drill bit chuck and moves in axial reciprocating movements with the drill bit chuck. The air motor has a coupling for connecting the air motor to a separate source of pneumatic pressure. The pneumatic pressure supplied to the air motor controls the operation of the air motor in rotating the drill bit chuck.  
         [0017]     A linear actuator housing is connected to the air motor housing. The actuator housing contains a ball and lead screw actuator that is connected to the air motor in the air motor housing. Operation of the linear actuator moves the air motor axially through the interior bore of the air motor housing, and thereby moves the drill bit chuck axially through the interior bore of the nosepiece housing.  
         [0018]     An electric motor is connected to the linear actuator housing. The electric motor is operatively connected to the ball and lead screw actuator in the actuator housing. In the preferred embodiment, the electric motor is a hybrid stepper motor. Selective operation of the electric motor controls the linear actuator to move the air motor axially in the air motor housing interior bore, which results in movements of the drill bit chuck axially in the nosepiece housing interior bore.  
         [0019]     An optical encoder is connected to the electric motor for monitoring the rotary output of the electric motor. The optical encoder is designed to produce signals representative of degrees of rotation of the electric motor, which are also representative of movements of the linear actuator in the actuator housing, movements of the air motor in the air motor housing, and movements of the drill bit chuck in the nosepiece housing.  
         [0020]     A sensor is mounted on the linear actuator housing. In the preferred embodiment, the sensor is a magnetic reed switch. The sensor senses the position of the linear actuator screw in the actuator housing. In particular, the sensor provides signals that are representative of the position of the lead screw in the actuator housing, and thereby determines movement of the lead screw to its fully set back position.  
         [0021]     A separate programmable controller communicates with the electric motor, the optical encoder, and the sensor on the actuator housing. The controller is operative to control the operation of the electric motor based on information previously programmed into the controller and information provided by the signals produced by the optical encoder and the sensor. The programmable controller is designed so that a motion profile for the drilling operation to be performed by the apparatus can be programmed on a desk top computer and downloaded to the controller. The controller can then be activated by a push button operated by an individual monitoring the drilling operation of the apparatus. With the apparatus secured at a work station adjacent the object to be drilled, the operator activates the apparatus to execute a peck feed drill cycle or a drill/countersink cycle, according to the preprogrammed motion profile. The controller executes the motion profile by controlling the rotation of the air motor and electric motor, and the resulting rotation of the drill bit chuck and the linear movements of the linear actuator. The controller can execute the motion profile without being connected to an external computer, and the motion profile can be repeated any number of times desired as programmed. Exact feed rates, peck rates, set back distances, stroke lengths, and dwell times can be programmed into the motion profile programmed in the controller, and the controller will control the drilling cycle to repeat itself exactly time after time. The programmed motion profile cannot be changed by the operator, and crib setup personnel simply download the motion profile provided to them into the controller to control the operation of the apparatus. Thus, the apparatus of the invention provides very little chance for human or mechanical errors to occur in the drilling procedures.  
         [0022]     The present invention greatly simplifies and improves the reliability of existing peck feed drilling and drill/countersink processes, and makes these processes more practical at manufacturing sights. The present invention provides significant improvements in the cost of manufacturing, the quality of the manufactured product, and the cycle time required for the manufacturing process. Thus, the apparatus of the invention represents an important evolutionary development in the field of portable power feed drilling.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0023]     Further features of the invention are set forth in the following detailed description of the preferred embodiment of the invention and in the drawing figure wherein:  
         [0024]      FIG. 1  shows a schematic representation of the portable electro-pneumatic drill apparatus of the invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0025]      FIG. 1  shows a schematic representation of the portable electrode-pneumatic drill apparatus  12  of the present invention. As stated earlier, the construction of the apparatus  12  is made up of known components arranged in a novel combination and configuration. Because the components are known, they are shown only schematically in  FIG. 1 . As shown in  FIG. 1  and as will be explained, the components of the apparatus  12  are assembled together, end to end, along a center axis  14  of the apparatus  12 , which facilitates the manual portability of the apparatus.  
         [0026]     The apparatus  12  includes an adjustable drill bit chuck  16  of conventional construction. In the preferred embodiment, the chuck  16  is a 3-jaw chuck that is adjustable to securely hold a variety of different size drill bits. The chuck  16  removably holds the drill bits, allowing replacement of various different size drill bits in the chuck.  
         [0027]     A nose piece housing  18  surrounds and protects the chuck  16 . The nose piece housing  18  is generally cylindrical, and has a hollow interior bore  22  that extends through the length of the housing. The bore  22  has a cylindrical interior surface that is coaxial with the apparatus center axis  14 . The interior surface of the bore  22  provides support to the drill bit chuck  16  for rotation of the chuck in the bore, and for axial movement of the chuck through the bore. The nose piece housing  18  is opened at its distal end  24  to enable insertion of a drill bit (not shown) into the opening and into the drill bit chuck  16  when removably securing the drill bit to the chuck.  
         [0028]     The proximal end  26  of the nose piece housing  18  is connected to an air motor housing  28 . The air motor housing  28  has a hollow interior bore  32  that extends through the air motor housing and is coaxial with the apparatus center axis  14 . The air motor housing bore  32  communicates with the nose piece housing bore  22  through the connection between the air motor housing  28  and the nose piece housing  18 . A slot (not shown) is provided through the side of the air motor housing  28  to the interior bore  32 . The slot (not shown) extends axially along a portion of the length of the air motor housing bore  32 .  
         [0029]     An air motor  34  is mounted in the air motor housing bore  32  for axial reciprocating movement of the air motor through the bore. The air motor  34  is operatively connected with the drill bit chuck  16  by a shaft  36  of the motor, represented schematically in  FIG. 1 . The operative connection between the air motor  34  and the drill bit chuck  16  rotates the drill bit chuck in the nose piece housing bore  22  on operation of the air motor  34 . The operative connection between the air motor  34  and the drill bit chuck  16  also causes the drill bit chuck  16  to reciprocate axially through the nose piece housing bore  22  on axial reciprocation of the air motor  34  in the air motor housing bore  32 . The air motor  34  has an air pressure inlet  38  that extends through the air motor housing slot (not shown). The air pressure inlet  38  is connectable to a separate source of pneumatic pressure that is supplied to the air motor  34  to rotate the air motor shaft  36 , as is conventional.  
         [0030]     A linear actuator housing  42  is connected to the air motor housing  28 . In the preferred embodiment of the invention, the linear actuator is a ball and lead screw linear actuator having a lead screw  44  that is operatively connected to the air motor  34 , represented schematically in  FIG. 1 . The lead screw  44  and the linear actuator housing  42  are positioned coaxially with the apparatus center axis  14 . Operation of the linear actuator lead screw  44  moves the air motor  34  axially through the air motor housing bore  32 , and there moves the drill bit chuck  16  axially through the nose piece housing bore  22 .  
         [0031]     An electric motor  46  is connected to the linear actuator housing  42  to operate the lead screw  44  of the linear actuator. In the preferred embodiment, the electric motor  46  is a hybrid stepper motor having a rotational axis that is coaxial with the apparatus center axis  14 . Selective operation of the electric motor  46  causes the lead screw  44  to move axially through the linear actuator housing  42 , which in turn cause the air motor  34  to move axially through the air motor housing  28 , which in turn causes the drill bit chuck  16  to move axially through the nose piece housing  18 .  
         [0032]     An encoder  52  is connected to the housing of the electric motor  46 . In the preferred embodiment, the encoder  52  is an optical encoder. The encoder  52  monitors the rotary output of the electric motor  46  and produces signals representative of the degrees of rotation of the electric motor. The signals produced by the encoder  52  are also representative of the movements of the linear actuator  44  in the actuator housing  42 , the movements of the air motor  34  in the air motor housing  28 , and the movements of the drill bit chuck  16  in the nose piece housing  18 . Thus, the encoder produces signals that are also representative of the axial position of a tip of a drill bit mounted in the drill bit chuck  16 .  
         [0033]     A sensor  54  is mounted on the side of the linear actuator housing  52  at a pre-determined position along the housing axial length. The sensor  52  is preferably a magnetic read switch. The lead screw  44  inside the linear actuator housing  42  is modified with a magnet (not shown), the position of which in the linear actuator housing  42  is sensed by the magnetic read switch sensor  54 . Thereby, the sensor  54  senses the position of the linear actuator lead screw  44  in the actuator housing  42 . In particular, the sensor  54  provides signals that are representative of the position of the lead screw  44  in the actuator housing  42 , and thereby provides an indication of the movement of the lead screw  44  to its fully set back position in the linear actuator housing  42 .  
         [0034]     The stepper electric motor  46 , the optical encoder  52 , and the magnetic read switch  54  are all wired through flexible electrical conductors  56  to a programmable controller  58 . The programmable controller  58  is wired to a separate power source  62 . In the preferred embodiment, the power source  62  is a 30-volt, 4 amp power supply.  
         [0035]     The controller  58  is programmable by connecting the controller to the serial port on a desktop computer (not shown). In the preferred embodiment the desktop computer would be running Si programmer software. A user of the apparatus writes a program using the desktop computer for the required motion profile of the apparatus, downloads the program to the controller  58 , tests the program, and then removes the power and disconnects the controller from the desktop computer. Activating the controller  58  will then automatically run the downloaded motion profile. The program for the motion profile can be written so that the controller  58  requires only the press of an activation button to start the motion profile. This would allow the operator of the apparatus to lock the apparatus into a drilling fixture prior to starting the drilling cycle. The controller  58  could also be programmed to stop at any point when an “interrupt” button is pressed. This gives the production operator full control over when the motion profile starts, and also provides the operator with the ability to stop the drilling cycle if something goes wrong.  
         [0036]     The controller  58  is also programmed to go to the start position should the linear motion of the actuator  42  encounter more than a predetermined rated load. This is very useful for situations where a drill bit becomes broken during the process, and accumulation of material chips hinders the rotation of the drill bit, or the air motor  34  is not rotating as the drill bit chuck  16  is fed forward by the linear actuator  42 . As a result, even though the linear actuator  42  uses a mechanical lead screw, it is very difficult for anything to occur that would cause permanent damage to the actuator.  
         [0037]     A separate programmable controller communicates with the electric motor, the optical encoder, and the sensor on the actuator housing. The controller is operative to control the operation of the electric motor based on information previously programmed into the controller and information provided by the signals produced by the optical encoder and the sensor. The programmable controller is designed so that a motion profile for the drilling operation to be performed by the apparatus can be programmed on a desk top computer and downloaded to the controller. The controller can then be activated by a push button operated by an individual monitoring the drilling operation of the apparatus. With the apparatus secured at a work station adjacent the object to be drilled, the operator activates the apparatus to execute a peck feed drill cycle or a drill/countersink cycle, according to the preprogrammed motion profile. The controller executes the motion profile by controlling the rotation of the air motor and electric motor, and the resulting rotation of the drill bit chuck and the linear movements of the linear actuator. The controller can execute the motion profile without being connected to an external computer, and the motion profile can be repeated any number of times desired as programmed. Exact feed rates, peck rates, set back distances, stroke lengths, and dwell times can be programmed into the motion profile programmed in the controller, and the controller will control the drilling cycle to repeat itself exactly time after time. The programmed motion profile cannot be changed by the operator, and crib setup personnel simply download the motion profile provided to them into the controller to control the operation of the apparatus. Thus, the apparatus of the invention provides very little chance for human or mechanical errors to occur in the drilling procedures.  
         [0038]     The present invention greatly simplifies and improves the reliability of existing peck feed drilling and drill/countersink processes, and makes these processes more practical at manufacturing sights. The present invention provides significant improvements in the cost of manufacturing, the quality of the manufactured product, and the cycle time required for the manufacturing process. Thus, the apparatus of the invention represents an important evolutionary development in the field of portable power feed drilling.