Electronically triggered surface sensor unit

• US 6,158,929 A
• Filed: 11/05/1999
• Issued: 12/12/2000
• Est. Priority Date: 07/01/1998
• Status: Expired due to Fees

• Current Assignee: BAE Systems Plc
• Original Assignee: BAE Systems Plc
• Inventors: Fisher, David
• Primary Examiner(s): Howell, Daniel W.
• Application Number:
  US09/434,260
• Time in Patent Office: 403 Days
• Field of Search: 408/1 R, 408/10, 408/11, 408/12, 408/13, 408/14, 408/15, 408/16, 408/72 R, 408/202, 408/241 S
• US Class Current: 408/1.00R
• CPC Class Codes: B25B 23/0064 Means for adjusting screwing depth
• CPC Class Codes: G05B 19/19 characterised by positioning or contouring control systems, e.g. to control position from one programmed point to another or to control movement along a programmed continuous path
• CPC Class Codes: G05B 2219/49232 Limit penetration of drill into backup material, support
• CPC Class Codes: Y10T 408/03 Processes
• CPC Class Codes: Y10T 408/17 to control infeed
• CPC Class Codes: Y10T 408/18 with stopping upon completion of prescribed operation
• CPC Class Codes: Y10T 408/21 with signal, indicator, illuminator or optical means
• CPC Class Codes: Y10T 408/8925 Depth-limiting member

Abstract

A method and apparatus for controlling the penetration depth of a cutting tool of a numerically controlled machine. A substantially cylindrical collar extends around at least part of the cutting tool with the collar being axially movable with respect to the axis of rotation of the cutting tool. An electronic sensor, secured to a non-rotatable housing of the numerically controlled machine transmits a signal to terminate further penetration of the cutting tool. The sensor is situated adjacent the collar and axially rearward thereof. A locking pin is provided for preventing an axially rearward end of the collar from touching an axially forward end of the electronic sensor when the collar is not being subjected to a force acting in a rearward axial direction. A nose bush for pre-positioning of the collar relative to the cutting tool in the axial direction is advantageously provided.

Claims

1. A surface sensor unit for controlling the penetration depth of a cutting tool of a numerically controlled machine, said sensor unit comprising:

a substantially cylindrical collar extending around at least part of the cutting tool, said collar being axially movable with respect to the axis of rotation of the cutting tool;

an electronic sensor secured to a non-rotatable housing of a numerically controlled machine, said sensor being capable of transmitting an end of penetration signal to said machine upon contact between said sensor and said collar, said sensor being situated adjacent the collar and axially rearward thereof;

restraining means for preventing an axially rearward end of the collar from touching an axially forward end of the electronic sensor when the collar is not being subjected to a force acting in the rearward axial direction; and

depth control means for pre-positioning of the collar relative to the cutting tool in the axial direction.

2. A surface sensor unit as claimed in claim 1 wherein said collar comprises at least an axially rearward portion and an axially forward portion, said axially forward portion being movably connected to said axially rearward portion.

3. A surface sensor unit as claimed in claim 2 wherein said axially rearward portion of said collar is axially slidable along said non-rotatable housing.

4. A surface sensor unit as claimed in claim 2 wherein said axially forward portion of said collar extends axially forward around at least part of said cutting tool.

5. A surface sensor unit as claimed in claim 2 wherein the axially forward portion of the collar is able to move in an axial direction relative to the rearward portion, such that the collar may be extended or retracted in the axial direction without movement of the rearward portion.

6. A surface sensor unit as claimed in claim 2 wherein said depth control means are adapted to allow the accurate axial movement of the forward portion independent of the rearward portion.

7. A surface sensor unit as claimed in claim 6 wherein said depth control means allow said forward portion to be threaded on to the rearward portion and said depth control means further provide an index ring for moving the forward portion accurately relative to the rearward portion.

8. A surface sensor unit as claimed in claim 7 wherein said depth control means comprise locking means for locking the forward portion relative to the rearward portion so that the portions are unable to move independently and the forward portion is constrained to slide in an axial direction with the rear portion.

9. A surface sensor unit as claimed in claim 8 wherein said locking means comprises a locking ring.

10. A surface sensor unit as claimed in claim 1 wherein said restraining means comprises a spring.

12. A surface sensor unit as claimed in claim 1 wherein said electronic sensor is adapted to transmit a signal, when its axially forward end is touched, to a suitably located receiving unit which communicates with or is a part of a control system for the NC machine, to request immediate retraction of the cutting tool.

13. A surface sensor unit as claimed in claim 12 wherein the signal is an infra-red signal.

15. A surface sensor unit as claimed in claim 12 wherein the signal is a radio signal.

16. A surface sensor unit as claimed in claim 12 wherein a cable is run from the electronic sensor to the control system of the NC machine to transmit the signal in the form of an electric current.

17. A surface sensor unit as claimed in claim 12 wherein the electronic sensor comprises a biased plunger operated micro-switch, connected in series with a light emitting diode and a power source.

18. A surface sensor unit as claimed in claim 17 wherein the micro-switch is positioned so as to be closed when its plunger is touched by a co-operating member of the unit.

19. A surface sensor unit as claimed in claim 17 wherein the light emitting diode emits radiation upon closure of said micro-switch.

20. A surface sensor unit as claimed in claim 19 wherein the electronic sensor comprises at least one window, said window comprising a substantially transparent material adapted to allow the emitted radiation to pass through.

21. A surface sensor unit as claimed in claim 20 wherein said emitted radiation is detected by said suitably located receiving unit.

22. A surface sensor unit as claimed in claim 1 wherein the position of the electronic sensor is recorded by the control system of the NC machine when the electronic sensor is touched.

23. A surface sensor unit as claimed in claim 22 wherein said position of the electronic sensor is compared to co-ordinates given in a NC machine program for the manufacture of an article currently being manufactured, for allowing simultaneous manufacture and inspection of the article.

24. A surface sensor unit as claimed in claim 1 wherein flexible seals are used to prevent coolant used during drilling and countersinking operations from reaching the electronic sensor.

11. A method of controlling the penetration depth of a cutting tool of a numerically controlled machine, comprising the steps of:

setting the axial position of a movable collar extending axially along at least part of the cutting tool;

moving the cutting tool axially forward to cut into a surface of an article being manufactured until the cutting tool reaches the desired depth and the collar touches the surface;

sliding said collar to slide axially relative to the cutting tool as the cutting tool continues to advance and the collar contacts the surface of the article;

providing an electronic sensor being capable of transmitting an end of penetration signal to said machine, and being situated axially adjacent and rearwards of the collar and in fixed relationship to the advancing cutting tool; and

biasing the collar from touching the electronic sensor until the cutting tool penetrates the article to the desired depth of penetration and the collar makes contact with the electronic sensor, causing the sensor to send a signal to a control system of the numerically controlled machine to request immediate retraction of the cutting tool.

14. A surface sensor unit for controlling the penetration depth of a cutting tool of a numerically controlled machine, comprising:

a substantially cylindrical collar extending around at least part of the cutting tool, said collar being axially movable with respect to the axis of rotation of the cutting tool;

an electronic sensor secured to a non-rotatable housing of a numerically controlled machine, said sensor being capable of transmitting an end of penetration signal to said machine upon contact between said sensor and said collar, said sensor being situated adjacent the collar and axially rearward thereof;

a biasing spring for preventing an axially rearward end of the collar from touching an axially forward end of the electronic sensor when the collar is not being subjected to a force acting in the rearward axial direction; and

a nose bush for pre-positioning of the collar relative to the cutting tool in the axial direction.

25. A method of controlling the penetration depth of a cutting tool of a numerically controlled machine, comprising the steps of:

setting the axial position of a movable collar extending axially along at least part of the cutting tool;

moving the cutting tool axially forward to cut into a surface of an article being manufactured until the cutting tool reaches the desired depth and the collar touches the surface;

providing sliding means on the cutting tool for enabling the collar to slide axially relative to the cutting tool as it continues to advance and the collar is pressed against the surface of the article;

providing an electronic sensor being capable of transmitting an end of penetration signal to said machine, and being situated axially adjacent and rearwards of the collar and in fixed relationship to the advancing cutting tool; and

providing restraining means for preventing the collar from touching the electronic sensor until the cutting tool penetrates the article to the desired depth of penetration and the collar makes contact with the electronic sensor, causing the sensor to send a signal to a control system of the numerically controlled machine to request immediate retraction of the cutting tool.

26. A method for controlling the penetration depth of a cutting tool of a numerically controlled machine as claimed in claim 25 wherein a shadowgraph is used to allow the collar to be accurately positioned axially with respect to the cutting tool before use.

27. A method for controlling the penetration depth of a cutting tool of a numerically controlled machine as claimed in claim 25 wherein the position of the electronic sensor is recorded at the instant it transmits a signal to the control system of the NC machine.

28. A method for controlling the penetration depth of a cutting tool of a numerically controlled machine as claimed in claim 27 wherein said position of the electronic sensor is compared with co-ordinates given in a NC machine program for the manufacture of the article, for allowing simultaneous manufacture and inspection of the article.

29. A method for controlling the penetration depth of a cutting tool of a numerically controlled machine as claimed in claim 25 wherein a safety factor is included in the NC machine program, so that the cutting tool will not necessarily continue to penetrate the article until a retraction signal is sent, but will retract at a given coordinate even if the sensor has not been activated.