Hydraulic drill unit

• US 4,157,231 A
• Filed: 09/27/1977
• Issued: 06/05/1979
• Est. Priority Date: 09/27/1977
• Status: Expired due to Term

• Current Assignee: United States Of America As Represented By The Secretary Of The Air Force
• Original Assignee: United States Of America As Represented By The Secretary Of The Air Force
• Inventors: Phillips, Joseph L.
• Primary Examiner(s): Vlachos, Leonidas
• Application Number:
  US05/837,330
• Time in Patent Office: 616 Days
• Field of Search: 408/1, 408/9, 408/11, 408/13, 408/16, 82/2 B, 82/1 C
• US Class Current: 408/1.00R
• CPC Class Codes: E21B 19/086 with a fluid-actuated cylinder E21B19/084, E21B19/087, E21B19/09 take precedence
• CPC Class Codes: E21B 44/06 in response to the flow or pressure of the motive fluid of the drive
• CPC Class Codes: G05B 19/4166 Controlling feed or in-feed G05B19/4163 takes precedence
• CPC Class Codes: G05B 2219/33261 Conversion of detected pulses to voltage, frequency to voltage convertor
• CPC Class Codes: G05B 2219/34037 Brm followed by postprocessor to smooth curve
• CPC Class Codes: G05B 2219/37077 Relative movement
• CPC Class Codes: G05B 2219/37081 Display machining parameters
• CPC Class Codes: G05B 2219/37092 Display position actual and or target
• CPC Class Codes: G05B 2219/37093 Display speed
• CPC Class Codes: G05B 2219/37175 Normal encoder, disk for pulses, incremental
• CPC Class Codes: G05B 2219/37183 Marker or index or coded information as well as position pulses
• CPC Class Codes: G05B 2219/37344 Torque, thrust, twist, machining force measurement
• CPC Class Codes: G05B 2219/37401 Differential pressure
• CPC Class Codes: G05B 2219/37405 Contact detection between workpiece and tool, probe, feeler
• CPC Class Codes: G05B 2219/41109 Drilling rate, feed rate
• CPC Class Codes: G05B 2219/41301 Pilot valve, linear fluid control valve and power cylinder
• CPC Class Codes: G05B 2219/43152 Feed in, transfer line, rapid traverse to work, grip speed
• CPC Class Codes: G05B 2219/45127 Portable, hand drill
• CPC Class Codes: G05B 2219/45129 Boring, drilling
• CPC Class Codes: G05B 2219/49047 Remove chips by tool up down movement, pecking
• CPC Class Codes: G05B 2219/49237 : Depth, tool depth control
• CPC Class Codes: G05B 2219/50031 : Zero setting, go to reference with gauge
• CPC Class Codes: G05B 2219/50203 : Tool, monitor condition tool
• CPC Class Codes: Y10T 408/03 : Processes
• CPC Class Codes: Y10T 408/165 : to control Tool rotation
• CPC Class Codes: Y10T 408/172 : Responsive to Tool
• CPC Class Codes: Y10T 408/175 : to control relative positioning of Tool and work
• CPC Class Codes: Y10T 408/21 : with signal, indicator, illuminator or optical means

Abstract

A hydraulic drill unit for drilling multimaterial, thick layer stock having a conventional hydraulic drill modified to have its feed controlled by a servo valve and its spindle speed controlled by a servo valve. A linear encoder is attached to the drill to provide an indication of drill position. The linear encoded provides 20,000 forward and reverse pulses per inch, depending upon the direction of travel, which are used to determine net feed rate. The net feed rate signal is compared with a command feed rate to control the feed servo valve. A magnetic pickup is used to provide a pulse signal proportional to RPM. This signal is compared with a command speed signal to control the spindle speed servo valve. Differential pressure transducers are used to measure pressure across the hydraulic feed pistion and the hydraulic drill motor to provide signals which can be used as indications of chip packing or a dull drill. Displays are provided to indicate Torque, Thrust, RPM, Inches of travel per revolution and relative displacement of the drill. These displays are used for the manual control of the drill. Torque, Thrust, RPM and absolute displacement information is supplied to a computer for the automatic operation of the hydraulic drill. Since optimized speeds and feeds are generally known for specific drill diameters and materials, this information has been programmed into the computer to provide the command feed and command speed levels for the various materials in a stack to provide the error signals for controlling the feed and speed servo valves. Torque and Thrust buildup are used by the computer for indications of chip packing or dull drill. Four solenoid valves are used to provide rapid advancement and rapid retraction of the drill.

Claims

1. An apparatus in combination with a drill, having a drill frame member and a drill feed housing which is movable with respect to the frame member;

a system for providing a signal proportional to the net rate of travel of the drill feed housing with respect to the frame member, comprising;

a linear incremental encoder, adapted to provide a predetermined number of pulses per inch of forward travel of the drill feed housing with respect to the frame member and a predetermined number of pulses per inch of reverse travel of the drill feed housing and a pulse signal indicating a substantially fully retracted position of the drill feed housing;

said encoder having a linear scale secured to said drill feed housing and an encoder head secured to said frame member;

a first frequency to voltage converter, responsive to pulses related to forward travel of said feed housing;

a second frequency to voltage converter, responsive to pulses related to reverse travel of said feed housing;

means for inverting the output of one of said frequency to voltage converters;

a first summing circuit;

means for connecting the inverted output of said one frequency to voltage converter to said summing circuit;

means for connecting the output of the other frequency to voltage converter to said summing circuit to provide a signal proportional to net feed rate of the drill feed housing with respect to the drill frame member.

2. The device as recited in claim 1 wherein said drill is a hydraulic drill having a hydraulic motor driven spindle and a hydraulic piston driven feed;

a hydraulic supply;

means, including a first servo valve, connected between the hydraulic supply and said hydraulic motor for controlling the rotation of said spindle;

means, including a second servo valve, connected between the hydraulic supply and said hydraulic piston, for controlling the drill feed;

said means for controlling the rotation of said spindle including a first servo controller, connected to said first servo valve;

said first servo controller including a second summing circuit;

said spindle having a plurality of angularly spaced slots around the spindle;

a magnetic pickup, adjacent said spindle, adapted to provide two square wave signals offset 90°

proportional to the rotational speed of said spindle past said magnetic pickup;

means responsive to said square wave signals for providing a first input to said second summing circuit;

means for providing a control input signal to said second summing circuit to provide an error signal to the first servo controller to thereby control the spindle rotational speed;

said means, for controlling the drill feed including a second servo controller connected to said second servo valve;

said second servo controller including a third summing circuit;

means, responsive to the output of said first summing for providing a first input to said third summing circuit;

means for providing a control input signal to said third summing circuit to provide an error signal to the second servo controller to thereby control the drill feed.

3. The device as recited in claim 2, including, means, responsive to the pressure across the hydraulic motor, for providing a signal proportional to torque on said motor;

means, responsive to said torque signal for providing a display of the torque on said motor;

means, responsive to the pressure across hydraulic piston, for providing a signal proportional to thrust of said feed of the hydraulic piston;

means responsive to said thrust signal for providing a display of thrust of said hydraulic piston;

means responsive to the outputs of said linear encoder for providing a display of the position of the drill feed housing with respect to the drill frame member;

means, responsive to the outputs of the linear encoder and said square wave signals for providing a display of inches of travel of the feed per revolution of the spindle;

means for resetting said position display to zero whereby the travel of the drill feed from a predetermined position can be indicated on the display.

4. The device as recited in claim 3 including a normally open solenoid valve connected between said hydraulic supply and downward side of said hydraulic piston, a second normally closed solenoid valve connected between said hydraulic supply and the upward side of said hydraulic piston;

a third normally open solenoid valve connected between the upward side of the hydraulic piston and the hydraulic return line;

a fourth normally closed solenoid valve connected between the downward side of the hydraulic piston and the hydraulic return line;

means for selectively energizing the first, second, third and fourth solenoid valves for rapidly advancing the drill and means for selectively deenergizing the first, second, third and fourth solenoid valves for rapidly retracting the drill;

means for selectively energizing first, third and fourth solenoid valves together with said hydraulic piston to permit normal advance of said drill.

5. The device as recited in claim 4 including a computer programmed to provide computer control feed signals and computer control speed signals corresponding to known recommended feeds and speed for a plurality of materials in a stack for a given drill size;

and programmed to sense torque and thrust and to provide an output signal when torque or thrust exceed known recommended levels;

means, responsive to said first frequency to voltage converter and said second frequency to voltage converter for providing a drill feed position signal to said computer;

means responsive to said square wave signals for providing a spindle speed signal to said computer;

means responsive to said torque signal for providing a signal proportional to torque to said computer;

means responsive to said thrust signal for providing a signal proportional to thrust to said computer;

a first manually operable potentiometer, adapted to provide a control feed signal;

a second manually operable potentiometer, adapted to provide a control speed signal;

means for selectively supplying said potentiometer control feed signal or the computer control feed signal to said second summing circuit and means for selectively supplying said potentiometer control speed signal or the computer control speed signal to said third summing;

a pulse counter responsive to the output of said first frequency to voltage converter and said second frequency to voltage converter for providing a signal proportional to the position of the drill feed housing with respect to the drill frame member;

means for supplying the pulse signal indicating a fully retracted drill to said counter to reset the counter when the drill is fully retracted to thereby provide an absolute drill displacement signal;

means for supplying said absolute displacement signal to said computer;

means, for switching the drill control between manual operation;

automatic computer control operation or manual control with computer monitor operation.

6. The method of drilling through a multi-material stack with a hydraulic drill, comprising:

controlling the forward and reverse movements of a drill with a hydraulic feed cylinder;

measuring the forward and reverse movements of the hydraulic drill feed cylinder with a linear encoder;

subtracting a signal proportional to the reverse movement from a signal proportional to the forward movement to obtain a net feed rate signal;

comparing the net feed rate signal with a common feed rate signal proportional to the desired feed rate for each material in the stack, to obtain an error signal;

controlling the rotation of the drill with a hydraulic spindle motor;

measuring the hydraulic spindle speed with a slotted spindle and a magnetic pickup;

comparing a signal proportional to spindle speed signal obtained from said magnetic pickup with a command speed signal proportional to the desired speeds for the materials in the stack measuring the differential pressure across the feed piston to obtain a signal proportional to thrust;

measuring the differential pressure across the spindle drive to obtain a signal proportional to torque, retracting the drill in response to an increase in thrust or torque, above predetermined levels.