CA1237178A

CA1237178A - Method and apparatus for performing workpiece inspection with a probe

Info

Publication number: CA1237178A
Application number: CA000456486A
Authority: CA
Inventors: Richard O. Juengel
Original assignee: GTE Valeron Corp
Current assignee: Valenite LLC
Priority date: 1983-06-14
Filing date: 1984-06-13
Publication date: 1988-05-24
Also published as: JPS6013202A; NL190956B; GB2141365A; IT1209553B; FR2548349B1; ZA843832B; MX158057A; SE8403156D0; NL190956C; GB8411441D0; AU555481B2; KR900002677B1; CH669842A5; NL8401874A; JPH0738810Y2; SE457336B; FR2548349A1; IT8421251A0; DE3422181C2; SE8403156L

Abstract

Abstract of the Disclosure METHOD AND APPARATUS
FOR PERFORMING WORKPIECE INSPECTION WITH A PROBE
Various techniques are disclosed for controlling the operation of a workpiece inspection procedure using a battery operated probe to contact the workpiece and transmit information back to a controller in a machine tool system. In one embodiment, battery power is applied to the probe transmission circuitry in response to a flash of infrared radiation. In another embodiment, the probe is turned on by touching the probe against a reference surface. In both embodiments, a timer is provided to automatically disconnect the batteries after a predetermined time period. In such manner battery life is prolonged.

Description

~37~

This invention generally relates to workpiece in~pection system~ and, more particularl~, to the u~e of probes in automated machine tools to contact the workpieoe and provide information relating thereto. Related material i~ disclosed in applicant's U.S. Patent No~. 4,401,945, 4,545,106 and 4,578,874 issued August 30, 1983, October 8, 1985 and April 1, 198~, respectively.

~ackground Art Automated machine tool 3y9tem9 require a precise mean~
of locating surfaces on workpieces. One of t`he most common methods is to have the machine move a probe into contact with a workpiece and to record the probe position when contact is made. Probes of this type are known as touch probes. They generally include a stylus for contacting the workpiece and circuitry which operates to generate an electrical signal when the stylus contacts the part. ~he machine controller can calculate information about the shape or location of the part from the X, Y and Z axes positional data of the probe when the stylus contact generates the electrical signal.
One of the problems encountered with the use of many of these types of probing systems is in the method by which the signal indicating contact by the probe i8 tranemitted back to the controller. It is often impractical to rely on conventional ~iring to carry the ~ignal since the wire~ may interfere wibh normal machining operations.
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~37~78 The patent literature di~closes several probe designs ~hich are adap-ted to be used in an automatic Machining center where the probe~ are temporarily stored in a tool magazine and are connected and removed from the spindle by an automatic tool changer mechanism. Representative examples of patent~
disclosing these probes include U.S. Patent No. 4,339,714 to Ellis; U.S. Patent No. 4,118,871 to Kirkham; and U.S. Patent No.
4,401,945 to Juengel.
The Kirkham approach is disadvantageous because its radio frequency signals are susceptible to electromagnetic interference and must be used within a relatively short transmission distance between the probe and a receiver. Among the problems with the probe system of the Ellis patent is that great care mu~t be taken to align the probe and a specially constructed detector on the spindle head in order for the reactive coupling therebetween to operate properly. The infrared transmission approach disclosed in the Juengel patent is far more advantageous. However, it does require that the probe, in most circumstances, contain its own power 30urce.
It has also been proposed to use touch probes in turning centers such as lathes, as well as in machining centers. Turning centers differ from machining or milling centers in that the workpiece is rotated instead of the tooI.
In most turning centers, the tool holders are mounted at spaced locations about a turret which operates to selectively advance one of the tools towards the workpiece to perform work thereon.

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general, tools for performing outer dimension worlc on the workpiece are mounted in slots within the ~urret whereas inner diameter tools such as boring bars are held in an adapter mounted to the turret.
5Touch probes used in turning centers have a somewhat different set of problems to overcome than probe used in machining centers, although the rnethod of transmitting the probe signal back to the controller remains a common concern. One of the problems unique ~o 10turning center application is that the probes remain fixed to the turret even when not in use unlike the situation with the machining centers where the probes are inserted in the spindle only when they are needed to be used. Consequently, it is not possible to rely on 15the probe insertion operation to activate the electronic circuitry therein.
One prior touch probe technique for turning centers utilizes inductive tr~a~smission modules to transmit the probe signal through the turret to the 20controller. See, e.g., LP2 Probe System literature of Renishaw Electrical Limited. Unfortunately, this technique requires a substan~ial modification of the turret in order to utilize the systemO Consequently, this approach does not lend itself to be easily used in 25existing machines without requiring the expense and machine down time to perform the retrofitting operation.
Also related to this invention, al~hough less directly, is that prior art concerned with wireless transmission o dimensional gauging data such as dis-closed in U.S. Patent No. 3,670,243 to Fougere; U.S.
Patent No. 4,130,941 to Amsbury and U.S~ Patent No.
4,32~,623, to Juengel et al.
Disclosure of the Invention The present invention is directed tv appar~tus and a method of performing workpiece probing operations in a manner so as ~o prolong the life of the power sources used in these types of probes. According to one embodiment of the present invention the probe is pro-' :
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vided with a detector that serves to connect the powersource to the probe signal ~ransmission circuitry when the detector receives a given siynal. Means are pro-vided remotely loca~ed from the probe for generating this "turn on~ signal and wirelessly transmitting it to the detector in the-probe. This signal i~ generated prior to anticipated use of the probe to inspect the workpiece and may be initiated by the controller in an automated ~achine tool. Later, the power source is disconnected. Power is thus drained from the source only when necessary. This approach is espe~ially advan-tageous when the probes are used in turning centers where they remain fixed to the turret even though not always used for inspecting operations. However, the broad concepts of this invention have applicability in a wide variety of other probingand machine tool system applications.
In the preferred em^~diment, the machine controller initiates a flash of infrared radiation from a head mounted at a convenient location on the machine.
As a result, the probe transmission circuitry is enabled and generates an IR signal of a given frequency to indi~ate that the pro~e is opera~ing properly and ready for use. The controller then proceeds with the inspection operation. When the probe s~ylus contacts the workpiece, the frequency o~ the IR transmission shifts. This shift in frequency is remotely detected and used by the controller to derive useful inforJnation about of the workpiece. The probe circui~ry preferab~y includes a timer which shuts off power to the circuit components after a predetermined time period has elapsed from the initial power up cycle or s~ylus contact.
Advantageously, the head may serve the dual purpose of transmitting the flash turn on signal and receiving the ~R ra-diation from the probe~ ~he head includes an internally contained optical flash device and a photodetector. An outer face of the head housing preferably includes a lens with an IR filter~ The IR
filter serves to fil~er out light in the visible spec-;~ . -'~ ~

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~ ' ~Z371~8 trum from the flash during probe turn on procedure. The lens operates to focus the IR radiation from the probe onto the photodetector in the head.
In an alternative embodiment, power to the probe circuitry is initially applied when the stylus contacts a reference s~rface. In operation, the machine moves the probe so that the stylus contacts the reference surface to initialize the power up cycle. The probe is then used to inspect the workpiece, with the probe operating to transmit signals relating thereto back to a remote receiver head.
Brief Description of the Drawings These and various other advantages o~ the present invention will become apparent to one skilled in ~15 the art upon reading the following specification and by reference to the drawings in which:
FIGURE 1 is an environi~ntal view showing a probin~ system made in accordance with the teachings of this invention in use with an automated machine tool;
FIGURE 2 is a perspective view illustrating the of a probing system utilizing a flash turn 011 techrique according to one embodiment of this invention;
EIGURE 3 is a perspective view illusLratirlg the use of a probing system with a touch turn on technigue according to an alternative embodiment, FIGU~E 4 illustraLes a cross sectional view along the lines 4-4 of FI~URE 2 of a probe construction according to one embodiment of this invention;
FIGURE 5 is a cross-sectional view along the lines 5-5 of FIGURE 4;
FIGURE 6 is an exploded perspectiye view of the probe shown in FIGURE 4;
FIGURE 7 is a perspective view of a flash/receiver head used in one embodiment of this invention;
FIGURE 8 is a cross sectional view alon~ the lines B-8 of FIGURE 7;
FIGURE 9 is a top plan vi~w of a circuit ~237~7~3 ~ 6 --board used in the flash/receiver head of FIGURE 7;
FIGURE 10 is a schematic diagram of circuitry used in the flash/receiver head;
FIGURE ll is a schematic diagra~n of circuitry used in the probe of one embodiment of this invelltion that utilizes the fla~h turn on technique; and FIGUR~ 12 is a schematic diagram of circuitry used in a probe utilizing the touch turn on technique.
Description of the Preferred Embodiments I. Overview FIGURE 1 illustrates, in simplified form, a typical machine tool system utilizing various aspects of the inventive features to be described. A n~merically controlled turning center 10 is shown therein together with a controller 12 for automatically controlling turning operations on a workp;ec~l4 according to pro-grammed instructions. Turning center 10 typically in-cludes a rotating chuck 1~ with jaws 18 thereon for holding the workpiece 14. Mounted to a turret 20 are a plurality of tools 22 - 24 for performing work on the inner diameter (ID) of workpiece 14. Typically, ID
tools of this sort include an elongated shank portion which are held in place in turret 20 by way of adapters - 26 - 28. In accordance with the present invention, a ~5 w~rkpiece inspection probe 30 is mounted to turret 2~ in the same manner as tools 22 - 24~ In this embodiment, probe 30 i5 mounted to turret 20 by way of adapter 32 which is identical to adapters 26 - 28.
As is known in the art, controller 12, among other things, operates to rotate turret 20 to bring the desired tool into the appropriate work position and then moves turret 20 until the tool contacts the workpiece and performs its desired machining operation thereon.
Probe 30, on the other hand, is used to inspect the workpiece 14. In this specific exarnple~ probe 30 is known in the industry as a touch probe in that it gen-erates an output signal when the probe stylus contact a .

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surface of the workpiece or other object. Suitable resolvers, digiti7ers or the like are used to provided signals to controller 12 indicating the position of the probe 30. Consequently, when the signal from probe 30 indicates contact with the workpiece controller 12 can derive useful information about workpiece dimensions, appropriate positioning thereof within the chuck, etc;
A. Flash Turn On ~ ro~e 30 contains its own battery power source for supplying energy to its signal transmission circuitry. Batteries, unfortunately, have limited useful lives. Thus, there is a real need for some means of preserving bat~ery life as long as possible. This is especially true for smaller sized probes used in turning centers. Smaller probes are also restricted in the size of the batteries they can use and thus conservation of energy is very important. ~
One aspect of this invention provides two way optical communication between probe 30 and a 2~ flash~receiver head 40. Head 40 is connected to con-troller 12 through an interface 42. When controller 12 determines that it is time ~o use probe 30 for a probing operation it generate~ a signal over llne 44 to inter-face 42, which in t~rn generates a control signal on 2~ line 46 to cause head 40 to transmit a given op~ical signal to probe 3~. In the preferred embodiment, this optical signal is a high intensity flash of infrared radiation. This flash is sensed by a suitable detector 48 in probe 30 ~see ~IGURE 23. The flash causes de-tector 48 to couple the battery power to the probetransmission circuitry. Preferably, probe 30 respon~s to the flash by transmitting IR radiation at a given frequency back to head 40 via light emitting diodes - (LEDls) 50 - 54. This I~ radiation is received by head 40 which, in turnJ supplies a signal to oontroller 12 via interface 42 indicating ~hat the probe 30 is operating properly and ready to perform Its lnspection operation.

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~.;2371~3 Controller 12 then causes turret 20 to advance probe 30 until the stylus 56 contacts worlcpiece 1~.
Probe ~0 responds to stylus contact by creating a shift in the frequency of the IR radiation transmitted by LEDIs 50 54. The shift in frequency is detected by interface ~2 and communicated to controller 12. The workpirce inspection operation continues as desired, with probe 30 transmitting frequency shifted IR radia-tion t~ head 40 every time the stylus makes contact.
Probe 30 includes timing means therein which will disconnect the battery supply from the transmission circui~ry after a predetermined period of ti~e. This time period begins when battery power is initially applie~ to the circuitry and is reset every time ~;he 1~ stylus contacts the workpiece. Thus, after the probing operation is finished the time period will eventually lapse and the battery power is disconnected from the transm~ssion circuitry. Accordi~!ly, the ba~tery power is onl~ used during periods of anticipated probe usage.
Whenever the probe is not in use the battery power is discon~ected and thus, conserves energy prolonging periods belween battery replacement.
B. Touch Turn On FIGURE 3 illustrates an alternative method of prolon~ing battery life. In this example, battery power ~s first connected to the probe transmission cir-cuitry ~y touching the probe stylus 56 against any known refere~ce surface 60. Reference surface 60 can be any fixed point within machine 10 whose location is known by

3~ contro~ler 12. Probe contact with surface 60 couples the ba~teries to the probe transmission circuitry and initia~es the transmission from LEDIs 50 - 54 to head 40~ ead 40' is like head 40 previously described except ~hat it does not need the flash means therein, nor do~ probe 30' req~ire the photodetector 48. O~her-wise, t~e two embodiments operate substantially identicially. After initialization, the probe is moved into p~sition for inspecting workp;ece 14, with probe ~h237~L78 g 30' transmitting frequency shifted signals to head 4~' whenever stylus contact is made. After a predetermined period of time from the last stylus contact, the batteries are disconnected from the probe transmission circuit.
II. Probe Construction FIGURES 4 - 6 illustrate in more detail the construction of probe 3~. The probe housing is characterized by a generally cone-shaped middle portion ~0 and a rearwardly projecting shank or cylindrical portion 72 of reduced cross-sectional diameter. In this specific embodiment, cylindrical portion 72 is hollow measuring about 4 and 1/4 inches in length~ with an outer diameter of about 1.4 inches.
The outer dimensions of cylindrical portion 72 are chosen to generally correspond with the dimensions of the bodies or shanks of tools 22-24. Consequently, probe 30 may be used in place o,~- one of the tools in turret 20 and held in adapter 32 ln the same manner. As shown most clearly in FIGURE 4, this may be accomplished by sliding cylindrical portion 72 into the pocket 74 of adapter 32 until the rear wall 76 of housing portion 70 abuts the front face 78 of adapter 32. This procedure thereby insures that the tip of stylus 56 is spaced at a 2~ known posi'ion with turret 20~ Consequently, controller 12 may accurately rely upon the position of the stylus 56 during the probe inspection operation~ O~ course, other conventional means may be used to position st~lus tip 56 at the appropriate spacing. For example, scme machine tool systerns utilize a set screw tnot shown)~or other means within the rear of pocket 74 to adjust the stylus spacing.
Cylindrical portion 72 advantageously serves the dual purpose of providing a battery co~partment as well as t~ provide an easy to use mounting mem~er. The elongated cylindrical shape of portion 72 enables the use of long life ~cylindricalU batteries resemblirlg typical flashlight batteries in shape for powering the probe transmission circuitry. Preferably, two "C~ cell ~.:
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', 7~78 ~0 --lithium batteries 80, 82 are employed. The ability to use cylindrical batteries, instead of smaller batteries such as button or disc cells, provides the probe with an exceedingly long operational life at low cost.
Batteries 80, 82 are slid into the interior of portion 72. A spring loaded cap 84 is then threaded onto the end of portion 72, with spring 86 urging the positive or male terminal 88 against board 90O The lower surface of board g0 incl~des a circular conductive layer 92. Board 90 is secured within a well 94 in an interior surface of wall 76 by way of screws 96. An insulated lead 98 makes elect.ical connection with con-ductive layer 92 by way of a plated through hole in board 90. 1`he opposite end of lead 98 is connected co circuit board 100 containing the probe circuitry. A
description of the electrical schenatic for the cir-cuitry will be described later h~erein. Circuit board 100 is generally circular in shape containing electrical components mounted on both sides thereof. Circuit board 100 is mounted within the interior of middle por~ion 70 by way of suitable fasteners 102 passing through standoffs 104. The board 100 also includes a centrally located aperture 106 therein ~hrough which various leads can pass to facilitate connection to the appropriate areas of circuit board 100.
Photodetector 48 and its associated sub-assem~ly is mounted in the outer sloping surface 1100f middle housing portion 70O ~hotodetector 48, in thi~s - particular example, is a PI~ diode such as par' No~
DP104 available from Telefunken. Photodetector 48 fi's within a countersunk bore and is held in place by way of a bezel 112 having a window therein. Interposed between bezel 112 and photodetector 48 are layers of transparent plastic 114, an infrared fil~er layer 116 and an O-ring 118. Suitable fasteners 120 sandwich all of these com-ponents into a subassembly mounted within the counter-sunk bore~ The leads from photodetector 48 pass through aperture 106 and are connected to suitable points on circuit board 100O

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~l23~7~78 LED's 50-59 are mounted adjacent to photode-tector ~8. LEDs 50-54 are designed to emit optical signals in the infrared radiation band, i.e. light which is not normally visible to the human eye. LED's 50-54 may comprise, for example, component Nos. OP290 avail-able from TRW, Inc. It should be noted at this point that the arrangement of LED's 50-54 and photodetector 48, taken together with the configuration of the sloping probe surface to which they are mounted combine to optimize several important advantayes. For example, by mounting LED's 50-54 onto the sloping surface 110 of the probe, the infrared radia'ion that is emitted thereby is directed forwardly of turret 20 at angles at which the radiation may be easily picked up by vaiious locations of head 40. The probe construction enables the user to rotate the probe into a position where the LED's 50 -54 and photodetector 98 are pointing in the general direc--tion of head 40. Thus, it is not necessary to mount ~ead 40 at any absolute spatial~location relative to probe 30 giving the system great flexibility for use in different 0achine tool systems. Reliable optical com-munication between probe 30 and head 40 is thereby obtained while at the same time minimizing the number of light emitting devices within probe 30. By keeping the number of light emitting devices to a minimum the energy drain from the batteries is kept as small as possiblec thereby further prolonging battery life.
Rounding out the assembly of middle portion 70, the wall 76 is affixed ~o rearward portions of por~ion 70 by way of suitable fasteners 122. O-r~ngs, such as ring 124, are advantageously used to seal the interior of the probe 30 from the somewhat adverse conditions that the probe may encounter during use in the machine tool system.
An annular nosepiece 130 includes a threaded male member 132 which mates with threads formed in a bore 134 in the front face of middle housing portion 70.
O-ring 136 is again employed for sealing purposes~
Nosepiece 130 may be made in various legnths to increase 12 - ~æ~7~

or decrea,~e the relatlve ~pacing of ~tylue tip 56 as may be desired. Due to the -threaded fastening engagemen-t with the middle housing portion 70, a variety 0~3uch no~epieces can be made and interchanged with one ~mo-ther for u~e in different applications.
A swi-tch unit 140 is removably attached to nosepiece 130. Switch unit 140 includes a circular whLotle no-tch ond con~truction 142 including a surrounding O-ring 146 which is press fit into -the internal passageway 146 within nosepiece 130. One or more set screws 148 extending orthogonally through nosepiece 130 clamps the switch unit 140 i.n place. Swi-tch unit 140 can be a variety of conqtructions that operate to open or break one or more electrical contacts therein when stylus 56 i~q moved from its rest position. ~hooe skilled in the art are aware of a variety of construction~ tha-t fulfill this general purpo~e.
One suitable switch construction is disclosed in detail in applicant's Canadian Patent ~o. 1,198,188, is~ued December 17, 1985. Priefly, this construction employs a wobble plate with three equally spaced ball contacts thereon. The wobble plate is spring biased so that the balls are normally pres~qed against three corresponding electrically conductive inserts. The three ball-insert pairs serve as switches (referred to later herein as switches Sl-S3) and are connected together in series. The wobble plate is connected to stylus 56. Whenever stylu~ 56 moves, the wobble pla-te -tilts and lifts one of the ball contacts from its corresponding in~ert -thereby breaking the electrical connection therebetween.
The three switche~ in unit 140 are connected to circuitry on board 100 by way of cable 150. lhe other end of cable 150 include~ a miniature coa~ connector 152 or o-ther suitable connector -that ma-tes with a connector on the end of replaceable ~witch unit 140. ~hose skilled in the . art appreciate that these typeo of swi-tch units are very sensitive and may need to be ~23~

replaced. The construction of the present invention enables such replacement to be made quickly and easily.
Various shapes and sizes of styli may be used in connection with probe 30. For example, instead of the straight stylus 56 shown in the drawings, a stylus may be used in which the tip thereof is offset from the major l~ngitudinal axis of probe 30O The various styli are in~erchangeable with switch unit 1~0 and may be attache~ thereto by the use of suitable fastening mealls such as set screws.

_I . FLi~SH TURN ON
A. Flash/Receiver Head The mechanical details of flash/receiver head

4~ are ~hown most clearly in FIGURES 7 - 9. Head ~0 employs a generally rectangular container 160 having an openin~ 162 formed ln a front face 1~4 thereofO One or more c~rcuit boards 166 are moun~ed within container lfi0. Circuit board 166 includes a variety of electrical componer~ts 'hereon for carrying out the functions to be described later in detail. Two of the most important components are shown in these drawings~ ~hey are xenon f~ash tube 16~ and photodetector 170. As noted before, the purpose of flash tube 168 is to generate a high intensity light pulse of short time duration to 2~ initiate probe operation. Xenon is preferred because it generates light that is rich in infrared radia~ion. In the preEerred embodiment, flash tube 168 is a part No.
BUB ~64~ xenon flash tube available from Siemens. It is capable of generatins a flash or light pulse lasting about S0 microseconds with an intensity of 100 watt/seconds. Other types of suitable light sources~ o~
course, can be employed.
Although not absolutely necessary, the visible light generated by flash tube 168 is preerably elimina~ed so as not to distract the operator or o~hers in the shop where machine tool 10 is being used. To this end, an infrared filter 172 coverinq opening 162 is r ' ~l237:~78 employed. IR filter 172 serves to block out visihlc light but passes infrared radiation therethrough generated by flash tube 168.
The purpose of photodetector 17~, on the other hand, is to detect in~rared radiation transmitted by probe 30. In this embodiment, photodetector 170 is a PIN diode and operates in a similar manner as pho~o-detect:or 48 in probe 30. A convex lens 174 is advan tageously used in opening 162 to concentrate the IR
radiation from probe 30 onto photodetector 170 which is located at the focal point of lens 174. Rounding out the construction of head 40, there is supplied a transparent face plate 176. ~ace plate 176 covers opening 162 and is suitably attached to front face 164 havinq a gasket 178 sandwiched therebe'ween.
B. Flash/Receiver Head Circuitry FIGURE 10 illustrates the circuitry used in the flash/receiver head 40 of t~e preferred embodiment.
As noted bef~re, head 40 is coupled to interface 42 over one or more conductor lines generally indicated by the reerence numeral 46~
A 26 volt alternating current ~AC) signal is dpplied to the primary of step u~ transformer Tl.
Energy from transformer Tl is stored across capacitors C8 and C9 which are, in turnl coupled across the posi-tive and negative electrodes of xenon flash tube 168 In this embodiment, capacitors C~ and C9 store abo~t 250-300 volts DC when fully charged.
To cause tube 168 to flash, controller 12 via interface 42 generates an appropriate signal level on the lines labeled ~controlU to cause LED 171 to conduct and emi light. LED 171 is part of an optical isolation package containing silicon controlled rectifier (SCR) 173. S~R 173 is connected in a series circuit wi~h the primary of transformer T~ and capacitor C10. Capacitor C10, like capacitor C8 and C9 is charycd due to the action of transformer Tl. When LED 171 is activa~ed, SCR 173 conducts and dumps the charge of ~apacitor C10 . .

~;Z 3~7~3 across the primary of transformer T2. This charye i.5 stepped up fo about 4,000 volts by transformer T2 whose secondary is connected to the trigger electrode 175 o~
flash tube 168. Trigger electrode 175 is capacitively coupled to tube 168 and the high voltage thereon is sufficient to ionize the gas within the tube. The ionized gas is sufficiently conductive to permit the energy from capacitors C8 and C9 to discharge across the positive and negative electrodes to create a very hiqh intensity flash of short duration. After tube lG8 flashes the capaci,ors begin to recharge until s~ch time as another flash initiating control signal is supplied from interface 42.
The probe 30 responds to the flash by transm~tting the IR signal which is picked up by the photodetector 170 in head 40. Photodetector 170 i5 - coupled to a tuned tank circuit comprising variable induct~r Ll and capacitor C2. By the way of a specific example~ probe 30 will generate IR radiation pulsed at a ~requency of abou~ 150 kilohertz until the probe stylus contac~s an object at which time the frequency will shift t~ about 138 kilohertz. The tank circuit in head 40 is t~ned to approximately the average of these two frequencies so that the head circuitry can detect eith~r one of these probe frequencies but will ilter out extraneous frequencies outside a preselected range or band wi~th~
The remaining circuitry in FIGURE 10 is used to ampl~y the detected signal transmitted from probe 30 which is coupled over the ~output" line to interface 42.
Brieflys the head amplification circuitry employs a field e~fect transistor Ql whose high input impedence matches that of the tuned circuit so as to avoid loadin~ problems. Transistor Q2 in cooperation with transis~or Ql amplifies the received signal and couples it to an emitter follower network employing transistor Q3. The amplified slgnal is coupled to interface 42 over the output line through DC filter capacitor C6 and resister R7 coupled to the emitter of transistor Q3.

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`` ~ Z37~7~3 In-terE~ce 42 has circuitry therein -that operates to d~tect theae selec~cd probe s~gnal frequencies and will generate outputs to controller 12 in response thereto. A first signal is generated to indicate that the probe is operating properly and a second signal is generated when the probe stylus contacts an object. Suitable circuitry for detecting the frequency shift is disclosed in U.S. Patent No. 4,545,106. ~riefly, such circuitry employs a phase locked loop circuit to perform a frequency shift keying operation on the received signals and activates relays upon detection of either of the selected frequencies. ~lowever, a variety of other methods of detecting the probe signals is within the skill of the ordinary practitioner.

_ Probe Circuitry FIGURE 11 is an electrical schematic diagram of the circuitry within probe 30. PNP transistor Q10 operates as a switch to selectively connect or disconnect power from batteries 80, 82 to the components used to generate IR radiation from L~D's 50-54. ~ransistor Q10 is normally in a nonconducting state and thus, the batteries 80, 82 effectively see an open circuit so that energy is not drained from the batteries.
However, when head 40 generates its flash of IR radiation, photodetector 48 conducts current from the batteries through inductor Ll for the duration of the flash.
~ he very fast rise time associated with the light pulse from the xenon flash tube provides a unique signal which can be easily discriminated from other light sources in the area of the machine tool. The IR filter at the head 40 excludes most of the visible spectrum so that the flash cannot be seen and become an aggravation to nearby per30ns. When the fast rise time _ 16 -kh/ ~l~J

~L~3 717 !3 light ~ulse reaches the photodetector 48, it is con-verted to an electrical pulse across the inductor coil L10. The coil L10 serves as a high pass filter and e~~
cludes steady state or low frequency light pulses such as flourescent lights in the area may produce.
The surge of current through photodetector 48 during the flash creates a ~rinqing~ phenomenon in in-ductor L10 as is knownin the art. ~his ringing phenomenon is basically a damped oscillation that lasts approx~mately 500 microseconds in response to the flash light pulse of about 50 microseconds. The oscillations from inductor Ll are amplified and inverted by invert7ng amplif~er 200. The output of amplifier 200 is connected to the base of transistor Ql~o The momentary ringing in inductor Ll caused by the flash creates a forward bias across the base-emitter junction of transistorQ10 and causes it to conduct. The conduc~ion of transistor ~10 connec~s the power from bat~eri~e~,~s, 80, 82 to the power inputs of the circuit components labled ~V in the drawings. When power is applied to oscillator 202 it begins supplying pulses to a time out counter 204 Counte~ 204 is reset to initialize its time out period when t~e flash is received from head 40. This ls accomp~~ished by way of an inverter 206 which inverts tne output of amplifer 202 to a positive signal which is shaped by the RC time constant of capacitor C20 and resist~r R2~ into a pulse. This pulse is connected to the re~et input of counter 204 through OR gate means 208. A~ will appear9 time out counter 204 is also reset whenever the probe stylus 56 contacts an object re-flecte~ hy the opening of one of switches Sl-S3.
Time out counter 204 is designed so ~ha~ i~
will pr~vide a logical lo~ signal on its output line ~10 as long as it is counting, i.e. not timed out~ The logical low signal on line 10 is inverted by inverter 212 wh~ch, in turn, is connected through diode D20 to the inp~t of amplifier 200. As a result~ the outpu~, of amplifier 200 is latched Lo a low state t~.ereby keeping transis~or Q10 in a conductive state providing power to ~237 1~t~

the circu.it components until such time as counter 209 times ~ut. The time out period for counter 204 is chosen to be of sufficient length to allow the ~on-troller 12 to begin the actual inspection process with the probe stylus con~acting the workpiece. In general, a time period of sevèral minutes is sufficient for this purpose. The time out period may be adjusted by way of potentiometer P20 defilling the oscillation frequency ~or time delay oscillator 202. Higher frequency oscilla-tioJIs from oscillator 202 cause counter 204 to count faster and thus, time out in a shorter time, and vice versa~ The generation of various ti~e delays is, Gl course 5 well within the skill of the ordinary practitioner.
Carrier oscillator 220 and divider 222 cooperate ~o define the frequency at which LEDs 50 - 54 transm~t their IR radiation back to head 40~ Conv~n-tional~y, oscillator 220 uses a`~crystal 224 having a known r~sonant frequency as a master clOckr Osci 1 lator 220 ope~ates to shape the oscillations from crystal 224 into a ~orm suitable for providing clock pulses to a conventional digital divider such as divider 222.
Divider 222 ser-~es as a convenient means for shifting the fre~uency transmitted by LEDs 50 - 54 when the probe stylus contacts an object. In this particular example, divider ~22 operates to divide 1.8 M~3z pulses from carrier oscillator 222 by the number 12 and thus pro vides at its output signal frequencies of about 150 Kr-lz.
The output of divider 222 is coupled to a driver transistor Q12 or other suitable circ~itry for driving LEDs S0 - 54 at the freguency defined by the divider output. Thusf in this example, when head ~0 initiates the flash turn on sequence, probe 30 responds by starting the transmission of IR radiatlon at a given frequency. ~he probe.transmission is detected by photo-detector 170 in head 40 which, in turn, supplies a indication to controller 12 that the probe 30 i.s operati~g properly and is ready to initiate the probing sequence. If probe 30 does not respond in such manner ~237 17~
- 1'3 -suitable precautionary measures can be taken.
When the probe stylus 56 contacts an object, one of the three switches Sl-S3 in probe unit 140 will open. The opening of one of the switches Sl-S3 causes two things to happen. First, it resets time out counter 201 to the beginning of its time out sequence.
Secondly, it creates a shift in the frequency trans-mitted by LEDs 50 - 54. This may be accomplished in a variety of manner. However, in the preferred embodi-ment, the opening of one of the switches Sl-S3 causes comparator 228 to go high. The output of comparator 228 is coupled to the reset input of counter 204 through OR gate 208 and thus, resets the counter. In addition, the output of comparator 228 is coupled to a frequency shift keying input of divider 222 over line 229 to cause it to divide the clock pulses from carrier oscillator 220 by a different number, here by the number 13. The output signals from di~ 222 thereby changed in ~requency to about 13~ KHz. Thus, the frequency of the I~ radiation transmitted by LEDs 50 - 54 is shifted in comparison to the frequency transmitted when the probe was initially turned on. This shift of frequenc~
is detected by photodet~ct~r 170 and transmitted to controller 12 to indicate stylus contact with an object, normally a workpiece surface~ Controller 12j by knowing the posi'ion of stylus 56 when this signal is received, can accurately calculate the dimensions of the workpiece or derive other useful information.
Controller 12 may move the probe 30 to contact other workpiece surfaces, each time the probe responding by a shift in IR radiation transmitted from the probe.
The timeout period of timeout counter 204 is chosen so that it is longer than the time that would elapse be-tween stylus contacts. When the probing operation is completed, controller 12 may go forward with other ma-chining operations as may be desired. There is no need to generate any further signals to turn of the probe since energy from the ba~teries will be automatically disconnected once counter 204 times out. In such case, .~ .

lZ37 'L78 its ou~put line 210 would go high ultimately resulting in the reverse biasing of the base -emitter junct1On of transistor Q10. This places transistor Q10 in a non-conducting state. In this manner the only drain on the batteri~s 80, 82 is the leakage current of the semicon~
ductors and the photocurrent of photodetector 48 Typically, this current can be very small, of~en less than 3~0 microamps. Consequently, the more power de-manding components are disconnected from the battery supply until actually needed for anticipated probe use.
Preferably these components are made from CMOS semi--onduct~r technology to even further conserve drain on the ba~'eries when used.
By way of a nonlimited example, carrier oscill,ator 220 is formed by a crystal controlled transislor Component No. 2N2222, divider 222 is an LM4526 available from National Semiconductor/ time delay oscillator 202 is formed from on,~e~,,,,half of an integrated circuit LM2903 available from National Semiconduc~or, and ti~e out counter 204 is an LM4040 also available from National Semiconductor.
IV. T~UCH TURN ON
The touch turn on technique previously descri~ed in connection with FIGURE 3 may be used 2S an 2~ altern~tive to the flash turn on technique described in sectio~ III. soth techniques have the same general ob3ect-,1ve, i.e,. to conserve battery life. To a larye extent the prob~ construction and circuitry for both techni~ues are similar. A schematic diagram of ~he probe circuitry or the touch turn on ~echnique is shown in FI~RE 12. This circuitry is like that of ~IGURE 11 and th~s, common reference numerals will be used to reference common componentsO
A comparison of the two figures will reveal that the major difference is the deletion of photo~
detector 48 and associated ind~ctor coil L10 in favor of resist~r R50 and capacitor C50. This circuit also differs in that it includes a line 231 conne~ted between ~LZ37~Lt78 the probe switches Sl-S3 and node N1 coupled to the input of inverting amplifier 200. Transistor Q10 is kept in a nonconducting state until such time as one of the switches Sl-S3 opens as a result of the stylus 56 contacting reference surface 60 (FIGUR~ 3). This is because the switches-Sl-S3 keep the input to amplifier 200 at substantially ground level as long as they are closed; i.e. when the probe stylus is not contactiny anything. However, when stylus 56 contacts the reference surface 60 one of the switches S1-S3 opens and causes capacitor C50 to begin charging. Preferably, the values of resistors R50 and R18 as well as capacitor C5~
are chosen to provide an RC time constant that delays the time at which capacitor C50 is charged to a vol~age sufficient to turn on transistor Q10 after being in-verted by amplifier 200 This requires that the con-troller 12 hold the probe stylus 56 against the refer-ence surface 60 for a definite period of time, for example, about a second. This procedure will insure that accidental bumps against the probe stylus or other extraneous factors such as electrical noise will not erroneously trigger activation of the probe.
Once capacitor C50 has been sufficiently charged the transistor Q10 will turn on and ~upply po~er ~rom batteries 80, 82 to the probe transmission com-ponents. The counter 204 will be reset and supply its output signal over line 210 to latch the transistor Ql~
in its conducting state . In this embodiment, the divider will initially generate the lower of the two output frequencies due to the tripping of comparator 2~8 while the probe stylus 56 is contacting the reference surface. The controller 12, however, can be suitably programmed to consider this initial probe signal as an indicator that the probe has properly turned on and is ready to proceed with inspecting the workpiece.
Controller 12, knowing that the probe 30' is operating properly, then moves on to the workpiece in~
spection procedure with the stylus 56 contacting various workpiece surfaces. Once the stylus 56 is moved away ,, .

37~L7~

from the reference surface 60 the switches Sl~S3 close causing divider 222 to drive the LED's 50-54 at t~e other frequency. As soon as the stylus contacts a workpiece surface, one of the switches Sl-S3 opens again tripping comparator 228. This results in the resetting of counter 204. The tripping of comparator 28 also provides an output over line 229 to divider 222 to cause its output and therefore the outputs of LED's 50 - 54 to shift in frequency. This procedure continues until such time as the workpiece piece inspection procedure is finished, with the battery supply being automatically disconnected from the probe circuitry once timer 204 times ou~
SUMMARY
I5 From reading the foregoing specification, those skilled in the art will come to appreciate that it discloses several significant advances in the workpiece inspection art. Each of the embodiments have been described in connection with the best mode that is currently contemplated for carrying out their inventive techniques. No attempt, however, has been made to list all of th~ various alternatives or modifications to the general concepts thereof. Such modifications or improvements should become apparent to the skilled 2S practitioner after a study of the drawings, specifica tion and claims. For example7 it should be apparent that the flash turn on or touch turn on techniques can be used with di;fferent types of probes other than the one specifically illustrated. Therefore, while this invention has been described in connection ~ith a par-ticular example thereof, its true scope Should be measured in light of _he following claims and equiva-lents thereto.

'

Claims

1. Apparatus for use in a machine tool system, said apparatus comprising:
first means for sensing information about a workpiece, said first means including circuit means for transmitting information relating to the workpiece to a remote receiver, a power source, and detector means operative to connect power from the source to the circuit to enable operation thereof upon receipt of a given signal; and second means remotely located from the first means for wirelessly transmitting the given signal to the detector means to thereby initiate the supply of power to the circuit;
whereby power drain from the source is minimized by selectively using energy therefrom only during periods of anticipated use

2. The apparatus of claim 1 wherein said circuit means includes timer means for discontinuing the supply of power from the source to the circuit after a predetermined period of time.

3. The apparatus of claim 2 wherein said predetermined period of time is measured from the time at which power from the source is initially supplied to the circuit or an indication that the first means has undergone a sensing operation.

4. Apparatus for use in a machine tool system to detect contact with a workpiece, said apparatus comprising:
probe means including a stylus for contacting the workpiece, circuit means for wirelessly transmitting information associated with stylus contact to a remote receiver, a battery power source, and photodetector means operative to connect power from the battery to the circuit to enable operation thereof upon receipt of a given optical signal, and first means remotely located from the probe for transmitting the given optical signal to the photo detector means in the probe prior to anticipated usage thereof whereby power drain from the battery is minimized.

5. The apparatus of claim 4 wherein said probe circuit includes a timer that discontinues the supply of power from the battery after a predetermined period of time has elapsed from the generation of the given signal or stylus contact with the workpiece.

6. The apparatus of claim 5 wherein said given optical signal is a high intensity flash of infrared radiation.

7. The appartatus of claim 4 wherein said probe further includes:
optical transmission means connected to said circuit means, operative to transmit infrared signals indicating stylus contact with the workpiece.

8. The apparatus of claim 4 wherein said first means further comprises:
a housing having a flash tube therein, a photodetector, and an infrared filter covering in an opening in a wall of the housing.

9. The apparatus of claim 8 wherein said housing further includes a lens for focusing IR
radiation from the probe onto the photodetector.

10. The apparatus or claim 7 wherein said probe circuit is operative to generate a given frequency for driving the optical transmission devices when power from the battery is first applied, and for shifting the frequency when the stylus contacts the workpiece.

11. A method of using a battery powered probe in a machine tool system, said method comprising:
generating an optical signal prior to anticipated usage of the probe;
detecting said signal at the probe; and using said detected signal to couple power from the battery to electrical components within the probe for a period of time sufficient to enable the probe to perform desired operations on a workpiece.

12. The method of claim 11 which further comprises the steps of:
transmitting an optical signal of a given frequency from the probe when power from the battery is initially supplied to the circuit components; and shifting the frequency of said transmitted optical signal when the probe contacts the workpiece.

13. The method of claim 11 which further comprises the step of:
discontinuing the supply of power from the battery to the circuit components after a predetermined period of time has elapsed from the detection of said optical signal or probe contact with the workpiece.

14. A probe for detecting information about a workpiece, said probe comprising:
circuit means for wirelessly transmitting information about the detected workpiece to a remote receiver; a battery power source; and detector means operative to initiate the supply of power from the battery to the circuit means to enable operation thereof upon receipt of a given wirelessly transmitted signal.

15. The probe of claim 13 wherein said detector means is a photodetector operative to respond to a given optical signal.

16. The probe of claim 14 wherein said given optical signal is a high intensity flash of infrared radiation.

17. Apparatus for use in a probing system utilized by a machine tool, said apparatus comprising:
a container having a light source and a photodetector therein, means for energizing the light source prior to a probing operation for coupling battery power in a probe mounted to the machine tool thereby energizing its optical transmission circuitry, and means coupled to the photodetector for detecting receipt of optical signals containing information relating to the probing operation.

18. The apparatus of claim 17 wherein said light source is a flash tube, said photodetector is responsive to infrared radiation, and said container includes an infrared filter for substantially filtering out light in the visible spectrum generated from the flash tube;

19. The apparatus of claim 17 wherein said container further includes lens means for focusing the optical signals onto the photodetector.

20. In a probe for detecting information about a work-piece, said probe having at least one optical transmitting device for transmitting information to a remote receiver, electrical components for driving said optical device, and at least one battery for supplying energy to the components, wherein the improvement comprises:
input circuit means containing a photodetector and an inductor coupled to the battery, operative to generate an output signal of a given amplitude in response to a remotely generated flash of light, and switch means responsive to the output signal for connecting energy from the battery to the electrical components to thereby enable optical transmission of the information to the remote receiver.

21. The improvement of claim 20 which further comprises:
timer means for generating a latching signal to keep the switch means in a given state to thereby maintain battery connection for a predetermined period of time;
first means for detecting when the probe contacts an object;
second means for generating at least two different frequencies for driving said optical transmitting device; and said first means being connected to the timer means and second means, operative to reset the timer and create a shift in frequency when the probe contacts an object.

22. Apparatus for use in a machine tool system, said apparatus comprising:
first means including a probe for sensing information about a workpiece, said first means including circuit means for transmitting information relating to the workpiece to a remote receiver, a power source, and detector means operative to connect power from the source to the circuit to enable operation thereof upon receipt of a given signal;
second means remotely located from the first means for wirelessly transmitting the given signal to the detector means to thereby initiate the supply of power to the circuit;
said second means including a flash tube and tube activation means for energizing said tube to create said given signal in the form of a high intensity flash of light of short duration; and said detector means including photodetector means having an electrical characteristic responsive to light, and said detector means further including filter means coupled to the photodetector means for rendering said detector means responsive to said flash to cause connection of power from the source to the circuit to enable operation thereof while rendering the detector means essentially unresponsive to other light sources which may be located in the area of the probe;
whereby power drain from the source is minimized by selectively using energy therefrom only during periods of anticipated use.

23. Apparatus for use in a machine tool system to detect contact with a workpiece, said apparatus comprising:
probe means including a stylus for contacting the work-piece, circuit means for wirelessly transmitting information associated with stylus contact to a remote receiver, a battery power source, and detector means operative to connect power from the battery to the circuit to enable operation thereof upon receipt of a given optical signal;
first means remotely located from the probe for trans-mitting the given optical signal to the detector means in the probe prior to anticipated usage thereof whereby power drain from the battery is minimized;
said first means including a flash tube, means for energizing said flash tube, and infrared optical filter means for blocking visible light from the flash tube whereby activation of said flash tube generates said given optical signal in the form of a high intensity flash of infrared light of short duration; and said detector means including photodetector means having an electrical characteristic responsive to light, said detector means further including electrical filter means coupled to the photodetector means for rendering said detector means responsive to said flash to cause connection of said battery power to said circuit while rendering said detector means substantially unresponsive to other light sources which may be located in the area of the probe.

24. The apparatus of claim 23 wherein said first means further comprises:
a housing having said flash tube therein, a photo-detector for receiving signals from the probe, and said infrared optical filter means being located in an opening in a wall of the housing.

25. A method of using a battery powered probe in a machine tool system, said method comprising:
using a flash tube to generate an optical signal in the form of a high intensity flash of light prior to anticipated usage of the probe;
filtering visible light from the flash and transmitting it to the probe;
employing circuitry in the probe that will provide a given output signal in response to said flash while being sub-stantially unresponsive to other light sources which may be located in the area of the probe; and using said output signal to couple power from the battery to electrical components within the probe for a period of time sufficient to enable the probe to perform desired operations on a workpiece.

26. A probe for detecting information about a workpiece, said probe comprising:
circuit means for wirelessly transmitting information about the detected workpiece to a remote receiver; a battery power source; and detector means operative to initiate the supply of power from the battery to the circuit means to enable operation thereof upon receipt of a high intensity flash of infrared radiation generated from a flash tube, said detector means including photodetector means having an electrical characteristic responsive to light; and filter means coupled to the photo-detector means for rendering said detector means responsive to said flash to cause connection of battery power to the circuit means while rendering said detector means substantially unresponsive to other light sources which may be located in the area of the probe

27. The probe of claim 26 wherein said filter means comprises an inductor coupled to said photodetector means.

28. In a probe for detecting information about a workpiece, said probe having at least one optical transmitting device for transmitting information to remote receiver, electrical components for driving said optical device, and at least one battery for supplying energy to the components, wherein the improvement comprises:
input circuit means containing a photodetector and an inductor coupled to the battery, operative to generate an output signal of a given amplitude in response to a remotely generated flash of light from a flash tube while being sub-stantially unresponsive to other light sources which may be located in the area of the probe, and switch means responsive to the output signal for connecting energy from the battery to the electrical components to thereby enable optical transmission of the information to the remote receiver.

29. The improvement of claim 28 wherein the remotely generated flash of light is infrared radiation provided by the energization of said flash tube and filtration of visible light therefrom.