Abstract:
A method and apparatus achieves making a surface-analysis determination precedent to allowing an electrofusion welding operation on pipe stock which is prescribed to be scraped, skinned or cleaned of surface contaminants prior to being graded ‘passable’ for such electrofusion welding. The method and apparatus utilizes non-contacting probes affixed to the welding power-supply leads such that inspection is automatic on the applicable pipe section(s) contemporaneously prior to enabling power-supply to the hot-wire welding coils. If the applicable pipe section fails the inspection, the welding equipment is disabled until the probes are disassembled, and then re-assembled for a succeeding inspection, such that during the interim an operator presumptively rectifies the situation as by re-scraping or skinning the applicable pipe section.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application is a continuation of U.S. patent application Ser. No. 10/634,652, filed Aug. 4, 2003 now U.S. Pat. No. 6,858,822, which claims the benefit of U.S. Provisional Application No. 60/400,488, filed Aug. 2, 2002, all of which disclosures are incorporated herein by reference. 
    
    
     BACKGROUND AND SUMMARY OF THE INVENTION 
     The invention relates to electrofusion of thermoplastics and, more particularly, to apparatus and method for making a pipe-surface quality determination preceding electrofusion. 
     Nowadays thermoplastic fittings are commonly fused or welded to thermoplastic pipes by electrofusion technology. Typically the fitting has an embedded conductor coiled inside it for induction heating by an electrofusion processor to accomplish welding to the pipe. It generally is a prerequisite that the involved pipe surface be cleaned and scraped preceding electrofusion. Scraping importantly accomplishes exposing unvarnished and/or fresh plastic for the electrofusion process. Un-scraped or insufficiently scraped pipe exacerbates problems with achieving leak-tight electrofusion welds. In cases of natural gas piping, leaking natural gas is a tremendous hazard. 
     To date reliance on whether the pipe is sufficiently scraped preceding electrofusion is reliant wholly on the honesty and/or good judgment of the responsible worker. 
     It is an object of the invention to provide a machine-controlled determination of pipe surface quality preceding electrofusion of thermoplastics in order to eliminate human error. 
     A number of additional features and objects will be apparent in connection with the following discussion of preferred embodiments and examples. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       There are shown in the drawings certain exemplary embodiments of the invention as presently preferred. It should be understood that the invention is not limited to the embodiments disclosed as examples, and is capable of variation within the scope of the appended claims. In the drawings, 
         FIG. 1  is an elevational sectional view of two plastic pipe ends butted against one another for permanent joining together by electrofusion technology as known in the prior art, wherein the exterior surfaces of both pipe ends have been cleaned and scraped for a given marginal length extending away from each end such that the scraping exposes unvarnished and/or fresh plastic; 
         FIGS. 2   a ,  2   b  and  2   c  form a series of views showing an example, prior art, plastic pipe scraper in accordance with U.S. Pat. No. 4,663,794-Evans, which is incorporated by reference, wherein: 
         FIG. 2   a  is a side elevational view, 
         FIG. 2   b  is a bottom plan view thereof, and 
         FIG. 2   c  is a side elevational view comparable to  FIG. 2   a  except showing the scraper in use to accomplish scraping on the exterior of plastic pipe, whereby the scraping process produces a series of spirally formed ridges and valleys proceeding axially along the exterior surface of the pipe; 
         FIGS. 3   a / 3   b  and  FIG. 4  form a series of views showing a non-limiting selection of example electrofusion fittings in accordance with the prior art, wherein: 
         FIG. 3   a  is a side elevational view of tapping-tee fitting and its mating under saddle, which slides on the lips of the tapping-tee in the direction of the reference arrow until limited by stops, 
         FIG. 3   b  is a view in the direction of arrows IIIB—IIIB in  FIG. 3   a  except in the omitting the under saddle, and 
         FIG. 4  is an elevational sectional view comparable to  FIG. 1  except showing an electrofusion coupling fitting slid over the scraped end margins of the abutting pipe ends; 
         FIG. 5  is a is a side elevational view comparable to  FIG. 4  except showing the connection of a pair of probe/connectors in accordance with the invention to the opposite terminals of the electrofusion fitting shown by  FIG. 4 ; 
         FIG. 6  is an enlarged detail of the right-side probe in  FIG. 5  (eg., right relative FIG.  5 &#39;s perspective) showing a non-contacting probe arrangement in accordance with the invention comprising an emitter (eg., “laser”) and “receiver” for sensing quality of pipe surface matters such as the local presence or absence of sufficient scraping (or skinning) on the pipe exterior; 
         FIG. 7  is a perspective view of an electrofusion processor modified in accordance with the invention as more particularly described below; 
         FIG. 8  is a is schematic view of a preferred embodiment of the invention for utilizing the results of surface analysis preceding electrofusion of thermoplastics in accordance with the invention; 
         FIG. 9  is a flowchart showing a method in accordance with the invention for determining a particular “reference signal” as denominated in  FIG. 8 ; 
         FIG. 10  is a flowchart showing a method in accordance with the invention for determining passing or failing pipe surface quality preceding electrofusion welding of thermoplastics in accordance with the prior art; and 
         FIG. 11  is an elevational sectional view comparable to  FIG. 4  except showing successful completion of electrofusion welding of the pipe ends and coupling. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The invention relates to apparatus and methods as more particularly described below for making machine-controlled determination(s) of pipe surface quality preceding electrofusion of thermoplastics, and in order to promote elimination of human error. 
     By way of background, briefly, electrofusion includes at least the practice of mating plastic parts  20  by the fusion achieved from the heat developed in hot-wire coil(s) (eg.,  52   b  in  FIG. 4 ) embedded in one or the other of the parts  50  (eg., typically embedded in a fitting  50 , and see FIGS.,  3   a ,  3   b  and/or  4 ).  FIG. 1  shows the ends  22  of two plastic pipe  20  ends butted against one another in preparation for permanent joining together by electrofusion technology as known in the prior art (although that will require a ‘coupling’ fitting  50  as shown by, eg., as  52  in  FIG. 4 ). The exterior surfaces of both pipe ends  22  have been cleaned and/or scraped (eg., skinned) for a given marginal length  25  extending away from each end  22  such that the scraping (or skinning) exposes newly-exposed plastic.  FIGS. 2   a ,  2   b  and  2   c  are a series of views showing an example, prior art, plastic pipe scraper  30  and in accordance with U.S. Pat. No. 4,663,794—Evans. 
     In general, raw or un-scraped (un-skinned) pipe stock  26  is procured with a varnished or otherwise smooth finish that is unsuitable for electrofusion process(es) while in that raw or un-scraped (un-skinned) condition. That is, there is an unacceptable likelihood that an electrofusion joint will fail quality standards if obtained by plastic parts having any surface varnish or dirt if not oxidation or contamination or OEM printing thereon. Hence it has long been a practice in the industry to scrape off a skin- or surface-layer of the pipe  20  in order to expose fresh or clean plastic  25  which indeed is suitable for electrofusion process(es). Scrapers  30  typically have a blade  32  that is about ⅜-inch ( ˜ 10 mm) wide and formed with about twelve shallow teeth  34  across such width such that as a result the scraper  30  might leave about thirty-two lines per inch ( − twelve lines per cm) of helically-formed ridges (eg., indicated by reference numeral  40  in  FIG. 8 , and which are alternated of course by valleys) along the axial extension of the exterior surface of the pipe  20 . The prior art scrapers  30  are arranged to auto-advance themselves helically along the axis of the pipe  20  while being turned in complete rotations so that the last furrow left behind by the trailing tooth of the blade  32  plows through the plastic skin more or less accurately parallel and properly spaced relative to the leading furrow cut or plowed one-rotation previously by the leading tooth. In other words, a scraped-section  25  of pipe  20  appears to be formed with a continuous screw thread (eg., as indicated by reference numeral  44  in  FIG. 3 ), having a coarseness at about thirty-two lines per inch (0.8 mm pitch), although relatively finer and much more coarser teeth arrangement are also known in the art. 
     Additionally, the scraping typically produces a surface roughness of between about 200 micro-inches ( ˜5 /1000 ths  mm) and 500 micro-inches ( ˜13 /1000 ths  mm). In contrast, un-scraped sections  26  of the pipe  20  typically exhibit a much smoother finish, measuring for example at about 30 micro-inches (very approximately  ˜1 /1000 ths  mm), which despite being smoother is structurally disordered and not nearly as structurally ordered as scraped pipe  25 , such structural ordering being (as said) in the form of, eg., screw thread  44 . 
       FIGS. 3   a  and  3   b  together show one example of a prior art electrofusion fitting  50 , and that being a tapping-tee fitting  51 .  FIG. 3   a  shows the tapping tee fitting  51  situated on a section of scraped pipe  25 , as prior to electrofusion.  FIG. 3   a  also shows that the tapping-tee fitting  51  has a mating under saddle  51   a , which slides on the lips  51   b  of the tapping-tee  51  in the direction of the reference arrow  51   a X until limited by stops. The under saddle  51   a  is utilized predominantly for temporary clamping purposes only. As soon as the electrofusion weld is completed, the under saddle  51   a  might be optionally removed as needless although it is typical to leave it in place. If the under saddle  51   a  were removed after welding, then  FIG. 3   b  shows an axial view (ie., in the direction of arrows IIIB—IIIB in  FIG. 3   a ) of how that would appear. 
       FIG. 4  shows a further example of an electrofusion fitting  50  in accordance with the prior art, this more particularly being a coupling fitting  52 . Coupling fittings  52  receive insertion of the scraped end margins  25  of a pair of abutting pipe ends  22 , such as comparably shown previously in  FIG. 1 . In  FIG. 4 , the fitting  52  has a barrel section  52   a  having an inner surface formed with an embedded hot-wire coil conductor  52   b  wound in a helix around the barrel section  52   a  and terminating in opposite terminals  52   c . To weld, the terminals  52   c  are connected to connectors “C” (not shown but see, eg., what is denominated as “C” in  FIG. 7 ) of an electrofusion processor (again not shown in this view but see what is denominated as EP 100  in, eg.,  FIG. 7 ). The electrofusion processor EP 100  supplies power to the terminals  52   c  through the connectors “C.” How much power, and by what profile of power-against-time, is a matter which is highly fitting-specific. Notwithstanding, fitting manufactures widely disseminate such specifications for their fittings  50  and they even code their fittings accordingly, typically by way of a bar code. Prior art electrofusion processors (see for comparison, eg.,  FIG. 7 ) include readers of such bar codes by way of for example and without limitation a bar code wand “W” (not shown in  FIG. 4  but see, eg., what is denominated as “W” in  FIG. 7 ) in order to search through their memory for what power-against-time profiles are expected, and supply such. The fitting  52  in  FIG. 4  furthermore includes a pair of visual ports  52   d , which are alongside the pair of terminals  52   c  respectively. After the fitting  52  has been fused welded to form the pipe connection, the visual ports  52   d  afford an operator opportunity to visually inspect the success (or not) of the weld. The foregoing are matters of the prior art. 
       FIG. 5  is a view comparable to  FIG. 4  except showing the connection of a pair connectors “C” in accordance with the invention to the pair of opposite terminals  52   c  of the electrofusion fitting  52  of  FIG. 4 . The inventive connectors “C” generally combine conventional aspects of supplying power to the terminals  52   c  along with more particularly a pair of probes  110  in accordance with the invention for making an inventive surface-analysis determination precedent to electrofusion welding. 
       FIG. 6  shows better one preferred arrangement for the probe(s)  110  in accordance with the invention. The operative principle comprises measuring the reflection, or more accurately the change or loss of such, of an emitted signal as detected or collected by one or more signal receivers  60 . Accordingly, the invention preferably operates on the basis of non-contact techniques. 
     As  FIG. 6  more particularly shows, a signal emitter  70  comprises a laser source as, for example and without limitation, a diode laser operating on a six-hundred nanometer wavelength (eg., visible red light). The emission receiver  60  or collector optionally comprises an infrared/photo-transistor although alternatively a photo-diode works as well, and a photo-resistor presents another option still. One such group of usable devices include without limitation CdS cells (and as indicated  62  in  FIG. 8 ). 
     It is preferred to aim the signal emitter  70  at as shallow angle-of-attack as possible, perpendicular to the ridges  40  of the scraped (or skinned) surface. To date the shallowest angle experimented with has been at 15° although it is believed that, if such can be constructed, half that angle would work better still.  FIG. 6  shows that a patch  25   p  of the scraped surface  24 , as illustrated by a dot-dash line, is impinged by the emitted signal. This patch, rather than being an infinitesimally small point, actually has some size. The impinged patch  25   p  has an ovate shape (if viewed from above) and impinges upon two to five or more lines of ridges  40 . Arranging things for a shallower angle is better because correspondingly that means more lines of ridges  40  will obstruct or interfere with the ‘clean’ reflection of the emitted signal. 
     There are impediments to producing a probe  110  with as shallow angle as desired, and these impediments relate to physical problems when working at such a miniature scale. It is preferred to overcome such impediments by folding the signal with one or more mirrors  81  at least for the purpose of locating both the emitter  70  and collector  60  on the outboard side of the probe  110  where there is more physical space to mount such. 
       FIG. 7  shows an electrofusion processor EP 100  that is modified in accordance with the invention to include circuitry and controls  100  to obtain such functionality as machine-controlled determination of pipe surface quality preceding electrofusion of thermoplastics F 100 . The electrofusion processor EP 100  comprises an input line cord “I,” output leads “O,” output lead connectors “C,” bar-code wand “W,” and various connector adaptors not specifically referenced and partially covered by reference letter “W.” The input line cord “I” plugs into something as public utility power which in this country runs at about one-hundred and twenty VAC line voltage. The electrofusion processor EP 100  is configured (or programmed) for stepping through the functions of, among other functions, energizing the probe(s)  110  and analyzing the signal(s) obtained thereby in order to make a quality determination if the pipe surface(s) has(ve) been sufficiently scraped (or skinned or otherwise made suitable). This functionality is more particularly shown in connection with  FIGS. 8 and 9 . Other functionality which is extra for the purpose includes without limitation data-logging functions F 101  which record and store operator functions against a time and date stamp in order to allow ‘ad hoc’ auditing of operator honesty and/or integrity. It is an object of the invention that, in cases of a failing surface-analysis determination, the electrofusion processor EP 100  is aborted or disabled A 120  from any chance at welding F 250  until a passing surface-analysis determination is obtained A 125 . Presumptively a passing surface-analysis determination A 125  can only practicably be obtained by an operator performing a reasonably timely calibration A 130  (see  FIG. 9 ) and then, after that, obtaining a very recent passing surface-analysis determination A 125  (see  FIG. 10 ) prior to a fusion operation F 250 . Instances of failing surface-analysis determination to date are presumptively/preferably overcome by an operator (or worker) disassembling the fitting and pipe(s) A 135  in order to scrape or re-scrape A 140  (skin or re-skin or the like) the involved pipe surface(s) for a succeeding chance to obtain a passing surface-analysis determination A 125 . 
       FIG. 8  is a is schematic view of a preferred embodiment of the invention for utilizing the results of surface analysis preceding electrofusion of thermoplastics in order to determine passing or failing surface-analysis determination. The receiver  60  is shown receiving the received signal  83 , wherein  FIG. 6  shows a preferred arrangement for positioning a signal receiver  60  in accordance with the invention relative to a surface to-be-analyzed and the source  70  of such signal, a signal emitter in accordance with the invention. The receiver  60  provides its own output-signal  85  corresponding to the received signal  83 . The receiver&#39;s output signal  85  is fed to a comparator  102  (eg., ‘comparison operator’ or like op-amp) which compares the receiver&#39;s output signal  85  to a reference signal  87 . At present it is preferred if the comparator  102  provides an output which signifies “pass” or “fail” although it is more preferred still if the comparator  102  outputs a range of values corresponding to a range of quality findings (eg., ranging from an upper extreme of fairly superior to a lower extreme of fairly inferior). The output of the comparator  102  is fed to control system  100 , as shown generically in  FIG. 8 . The control system  100  operates to achieve several functions. One, the control system  100  disables the operability of the weld function F 250  of the electrofusion processor EP 100  until a timely “pass” surface-analysis is achieved. Another, the control system  100  provides a recordable activity F 101  for the data-logger to record so that a relatively permanent record is made of the “pass, “fail” and/or ‘degree’ (or other) determination for audit purposes. Additionally, the control system provides the operator with one or more feedback signals so that the operator can act to correct the situation accordingly. 
     Preferred at present and due to changing preference in the future, it is preferred to compare the received (or measured) signal  83  against a reference signal  87  in order to make a “pass” or “fail” (or in-between quality) surface-analysis determination F 100  in accordance with the invention. It is known, however, in fields of industry outside the invention to utilize multiple metrics and/or criteria to make a surface-analysis evaluation, such as disclosed by and without limitation Lasercheck® gauge of the Optical Dimensions Co., of Lake Forest, Calif. Ideally it might be desirable to utilize the most advanced technology available to make a most complete surface-analysis determination. But in the real world of protecting against human error in electrofusion practice it is more realistic to practice technology which is highly competent though not the most advanced for the purposes of making a “pass” or “fail” (or in-between) surface-analysis determination precedent to electrofusion. It is believed that utilizing highly-competent in contrast to the most-advanced technology is more practical when better opportunity for advancing the objects of the invention are to be obtained from analyzing a larger area/circumference of the pipe(s). 
       FIG. 9  is a flowchart showing a methodology  150  in accordance with the invention for determining a particular “reference signal”  87  as denominated in  FIG. 8 .  FIG. 9  represents what might be alternatively referred to as a ‘set-up’ or a ‘calibration’ process  150 . An operator at the job-site fetches or acquires a sample piece of the pipe(s) to-be-welded. The object is to determine what signal the un-scraped (or un-skinned or otherwise un-cleaned) pipe provides under local conditions. Local conditions include color and type of pipe to-be-welded as well as the ambient light (in spite of shielding or hooded-enclosures to block out ambient light). Preferably this calibration or set-up cycle would likewise be logged by the data-recorder  100  for audit purposes F 101  to determine irregularities and the like. 
     Step one A 160  involves the operator procuring a sample of the un-scraped (or un-skinned or insufficiently cleaned) pipe of the color and type to-be-welded before the welding process(es) are to be attempted. It is preferred if this step is done often. For example, a work day which will involve a lot of welding of the same type and color of pipe deserves calibration at least at the beginning of the day. Indeed the calibration process  150  might best be performed several times during a day as there are likely changing circumstances with the quality of the pipe or else the amount of leakage of ambient light. In contrast, with reference to  FIG. 6 , the diminishment of the received signal  83  as compared to a reference  87  of un-scraped (or un-skinned or insufficiently cleaned) pipe against scraped (or its corollary sufficiently skinned or cleaned) pipe is ordinarily substantial:—particularly for yellow and white pipe, yellow pipe being more common in natural gas piping. 
     A succeeding step A 170  involves inserting one or more samples of un-scraped (or insufficiently skinned or cleaned) pipe under the probes  110  to obtain A 190  a reference value  87  or { 87 }. Perhaps one sample is sufficient to obtain the reference value. Better yet is if the operator subjects several samples to the work of the probes  110  to provide several individual reference values  87 , and with which the processor  100 &#39;s control circuitry analyzes for determining a ‘statistical’ reference value { 87 }.  FIG. 9  shows a manual way A 180  of determining individual reference values  87 , as by an operator manually tuning a dial as to a variable resistor (or potentiometer) or the like until such activity A 190  finds a given level of diminishment of the received signal  83  in comparison to the emitted signal. The foregoing assumes the circuitry  100  is measuring signal strength. 
     Ultimately, by means of the foregoing, the operator establishes a reference value  87  which compares favorably to what un-scraped (or insufficiently skinned or cleaned) pipe  20  looks like. 
       FIG. 10  is a flowchart showing a further methodology  200  in accordance with the invention for determining F 100  passing or failing pipe surface quality preceding electrofusion welding. The presumptive input or starting materials (and apparatus) include an electrofusion processor EP 100  or probe-operating/signal-processing system  100  in accordance with the invention, a fitting  50  and one or more pipes  20  depending on whether it is a single pipe to-be-welded to (eg, in cases of a tapping-tee fitting  51 ) or more (eg., in cases of a coupling fitting  52 ). Step one A 210  preferably comprises the original attempt to satisfactorily scrape (or skin or clean) the involved pipe section(s) prior to welding. Step two A 220  presumptively comprises assembling the fitting where it belongs. The succeeding steps A 230  comprise variously inputting to the electrofusion processor the particulars of the particular fitting:—nowadays that being most popularly accomplished by bar-code coding affixed to the fitting in combination with equipping the electrofusion processor with a bar-code reader (eg., “W” in  FIG. 7 ). It is presumed that the fitting&#39;s welding particulars will be a relevant factor in surface-analysis evaluation, but then perhaps not. What is presumptively most relevant is whether the relevant pipe section(s) has(have) been properly scraped (or otherwise skinned or cleaned). 
     Provided that the fitting  50  is properly disposed on the presumptively-properly scraped (or skinned or cleaned) pipe section(s)  25 , a preferred succeeding step A 230  is to energize the probe(s). It is preferred that the electrofusion processor EP 100  be disabled A 120  from providing welding-power to the fitting  50 &#39;s terminals unless as a condition precedent the electrofusion processor is enabled to do so by the probe control circuitry. Therefore, energizing the probes  110  for the first time affords the first opportunity to get an “operative” feedback signal  89 . In contrast, if a “fail” (or “abort” or “disable”) feedback signal is obtained, the operator is faced with several choices A 240 . Perhaps the fitting was improperly aligned over properly scraped (or skinned or cleaned) pipe section. Re-alignment might solve the problem. Perhaps otherwise, the pipe section(s) is(are) indeed insufficiently scraped (or skinned or cleaned), and therefor the operator&#39;s only practical choice for remedy is to disassemble and re-clean (eg., scrape or skin) the involved pipe section as whole. 
     Such is done iteratively until ultimately a “pass” (or the like) signal  89  is obtained from the probe(s)  110 &#39;s processing/control circuitry  100 . Given satisfaction of the foregoing condition(s), the probe(s)  110 &#39;s processing/control circuitry  100  enables (eg., no longer aborts or disables) the electrofusion processor EP 100 &#39;s weld functions F 250  (eg., the power-supply feed to the terminals). Therefore a better likelihood of a satisfactory weld in accordance with OEM prescriptions is much more likely obtained. The invention offers the prospect of negating human error better than nowadays achieved by previously practiced practices in the field of electrofusion of thermoplastics. 
       FIG. 11  is sectional view comparable to  FIG. 4  except showing successful completion of electrofusion welding  99  of the pipe ends  22  and coupling  52 . It is an object of the invention to promote a better likelihood of achieving satisfactory welds by a machine “checking” of the condition of things precedent before welding is attempted, as well as by providing a data log of such, for auditing purposes, not as much for back-tracking to identify operators lacking integrity but more for the benign purpose of reminding operators persistently that there is log of their operations. To be abstract for a moment, a popular definition of integrity is not only that one would do as one would want for themselves but alternatively that one would “do” with the thought that someone else is watching over one&#39;s shoulder. Every action will be public, or at least exposed in the end. The data logging functions of the invention promote the concept of that “someone” else is indeed watching over one&#39;s shoulder. It&#39;s not so much an object of the invention to create an onerous “big brother,” but that given good people who work as operators, who are nevertheless pressured by productivity pressures, better it is to promote good work ethics for the larger good of public welfare or safety than to rush a job and endanger such for sake of meeting productivity targets. Given that many of the many of these electrofusion welds are made in natural gas pipelines, the stakes are paramount. It is not so much a matter of assuring no contractor forsakes its/his responsibility but that no contractor endangers the public needlessly beyond what are locally-stated or more broadly-codified acceptable criteria for constructing electrofusion-formed piping systems. 
     The invention having been disclosed in connection with the foregoing variations and examples, additional variations will now be apparent to persons skilled in the art. The invention is not intended to be limited to the variations specifically mentioned, and accordingly reference should be made to the appended claims rather than the foregoing discussion of preferred examples, to assess the scope of the invention in which exclusive rights are claimed.