CENTERING DEVICE FOR USE WITH BRINELL HARDNESS-MEASURING PROBE

Abstract: The invention is directed to centering devices for use with Brinell hardness measuring instruments, particularly electro-optical instruments. Such instruments include an electro-optical probe (114) coupled by appropriate flexible cabling (115) with an associated processor which may include a display and a keyboard (19) interface. The probe includes one or more illumination sources (119) in a housing (116) with at least some of the optics of the instrument. The housing has an aperture (120) at one end of the probe which is aligned at least generally with the central axis (124) of the probe optics to provide to the probe optics a field of view of the specimen surface when the one end of the probe is located against the specimen surface (120). One centering device includes a spiderlike mechanical centering structure (40) protruding through the probe end opening. Another centering device includes a source (134) which develops a beam (140) of coherent or non-coherent light in the visible spectrum which is directed through the opening at the one end of the probe to permit an operator to align the probe.

Description: CENTERING DEVICE FOR USE WITH BRINELL HARDNESS-MEASURING PROBE Related Application This is a continuation-in-part of U.S. Patent Application Serial No. 07/657,596 filed February 19, 1991, which is incorporated by reference. Field of the Invention The invention relates generally to hardness testing and specifically to methods and apparatus for determination of Brinell indentation diameters for hardness testing. Background of the Invention Hardness of metal may be determined by indenting a metal specimen at a known force using a known device and measuring either the depth or diameter of the indentation. Diametric testing is most commonly referred to as Brinell testing, and is described in ASTM E10 (10-78) , incorporated herein by reference. In Brinell testing, a ball penetrator, either 5 mm or, more typically, 10 mm in diameter, is applied to a test specimen with a predetermined load to produce a generally spherical indentation in the specimen. Knowing the applied force, the Brinell hardness of the test specimen can be determined from the diameter of the indentation. Current Brinell testing involves measuring the diameter of the indentation along orthogonal axes using either a small optical microscope with a graded reticle or, more recently, an electro-optical instrument with a probe which indicates or responds to, respectively, the differences in light reflected from the specimen surrounding the indentation, the raised side walls adjoining the indentation and the indentation itself. Each type of instrument can be positioned over and against a specimen. Each instrument generates a magnified image of the underlying specimen surface. The operator moves the instrument to try to center the instrument over the center of the indentation. Each instrument also typically employs light focused or otherwise directed through at least part of the instrument so that when the central axis of the scope or probe is perpendicular to the specimen surface, the light also strikes the specimen surface beneath the instrument to illuminate that area including the indentation. A major problem with each type of instrument is the difficulty in locating and then accurately centering the instrument with respect to the indentation. In most instances, a field of view relatively large with respect to the size of the indentation must be provided in order to permit the operator to view a sufficiently large area of the specimen surface to orient the probe with respect to the indentation. In some instances, due to a roughness of the specimen surface and/or the polish of the side walls of the indentation, the contrast between light reflected from the undisturbed surface and the indentation is relatively low, making it difficult for the operator to optically identify the indentation and the center of the indentation. While the newest Brinell hardness- measuring electro-optical probes are configured to compensate for misalignment of the probe with respect to the central axis of the indentation, such misalignment between the indentation and the central optical axis of the probe can still lead to some degradation of accuracy in the diameter measurement, particularly if the probe is significantly off center. Because a relatively large field of view is typically provided to the optical system to permit the operator to find the indentation, the resolution of the optical system is further reduced. Another problem arises with the electro- optical probes in connection with the miniaturization of such systems for portability. Stationary systems can provide a CRT to image the specimen surface for the operator. Existing portable systems use liquid crystal displays to depict the specimen's surface and impression for the operator. The processing capability required to generate and maintain these specimen surface reproduction displays are typically a significant portion to total processing capability of the portable unit. Consequently, such units take undesirably long periods of time to perform measurements and provide a determination of Brinell hardness. It would be desirable to provide a means and a method to simplify alignment of a Brinell hardness optical measuring instrument, particularly one having an electro-optical probe, with a Brinell indentation which does not adversely affect the measurement results. It also would be desirable to provide the means and method to simplify portable Brinell hardness measuring instruments with electro-optical probes which dispense with the need to generate a display duplicating the specimen surface for the operator in order to align the probe with the Brinell impression for accurate Brinell hardness determination. Summary of the nvention In an instrument for determining hardness of a specimen by diametric measurement of an indentation in the surface of the specimen, the instrument including a probe and an electronic processor coupled with the probe, the probe including a housing with an opening at one end thereof, the probe further including artificial illumination means located for illuminating a specimen surface through the opening and optics means within the housing located for viewing the specimen surface exposed through the opening and illuminated by the illumination means, an improvement comprising a centering device mounted on the probe, the centering device having an alignment guide projecting through the opening, the alignment guide entering an indentation when the indentation is at least generally aligned with the opening. A centering device to improve a Brinell hardness-determining instrument, the instrument having an end configured for placement on a specimen surface to be examined and an opening through the end providing to optics within the instrument a field of view of the specimen surface on which the end of the instrument is placed, the centering device comprising: an alignment member having a central axis and two opposing axial sides, a portion of the alignment member protruding generally concentrically with respect to the central axis from one axial side of the alignment member through the opening to form a centering structure of the alignment member shaped to mate with a generally circular indentation in the specimen surface, a central portion of the alignment member further being configured to freely pass light axially through the alignment member generally around the central axis whereby the field of view of the instrument through the opening is at least substantially unblocked. In an instrument for determining hardness of a specimen by diametric measurement of an indentation in a surface of the specimen, the instrument including a housing with an opening at one end thereof, and optics within the housing configured for viewing the specimen surface exposed through the opening, an improvement comprising a centering device including an alignment guide projecting through the opening, the alignment guide entering an indentation when the indentation is at least generally aligned with the opening and the alignment guide. Brief Description of the Drawings The foregoing summary as well as the following detailed description of the presently preferred embodiment of the invention will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there is shown in the drawings an embodiment which is presently preferred. It should be understood, however, that the present invention is not limited to the particular arrangements and instrumentalities shown. In the drawings: Fig. 1 depicts a portable Brinell hardness- measuring apparatus including a hand-held electro- optical probe-type instrument mounting a first embodiment centering device of the present invention; Fig. 2 is a diagrammatic cross-sectional view of the probe taken along the lines 2-2 of Fig. 1; Fig. 3 is a cross-sectional view of the probe taken along the lines 3-3 of Fig. 2; and Fig. 4 depicts diagrammatically a preferred reticle used with a Brinell hardness-determining microscope equipped with the centering device of the present invention; and Fig. 5 is a partially broken away, diagrammatic side elevation of a probe of a portable electro-optical Brinell hardness-determining instrument including a second embodiment centering device of the present invention; and Fig. 6 is a localized side elevation of the second embodiment device of Fig. 5; and Fig. 7 is a bottom plan view of the device of the probe of Figs. 5 and 6. Detailed Description of Preferred Embodiment Like reference numerals are used to identify the same elements in the various drawings. Fig. 1 depicts schematically an exemplary, electro-optically configured Brinell hardness-measuring instrument indicated generally at 10 and, in conjunction with it, a specimen 12 the hardness of which is being measured. Electro-optical Brinell hardness measuring instruments are known and have been disclosed and discussed in a variety of U.S. patents, including, for example, U.S. 4,945,490, which is incorporated by reference herein in its entirety, as well as in other printed, published literature. The novelty of the present invention does not reside in such conventional instruments, per se, but rather in centering devices to be described which are improvements to such instruments as well as to microscope type Brinell hardness-measuring instruments, either as an aftermarket accessory or, preferably, configured into the instruments during original manufacture. The exemplary Brinell measuring instrument 10 in Fig. 1 includes a hand-held, electro-optical probe 14, physically and electrically coupled by appropriate flexible cabling 15 with an associated electronic processor 16 preferably including an optical display 18 and keyboard 19. The probe 14 includes an outer, generally tubular housing 20 which typically contains at least one internal artificial illumination light source 23 indicated diagrammatically and in phantom in Fig. 3. The probe housing further includes a photoresponsive subsystem with at least some optics which optics are indicated diagrammatically at 22. The probe 14 has one end 24 with a preferably circular (see Fig. 2) opening 25 therethrough, preferably centrally located with respect to the housing 20 and end 24. The end 24 is preferably planar for butting the end against a planar surface of a specimen. Light source 23 and the photoresponsive subsystem respectively illuminate and receive light reflected from a specimen 12 positioned at the opening 22. Power is typically supplied to light source 23 in the probe 14 through the cabling 15 from the processor 16. The photoresponsive subsystem typically generates one or more electrical signals in response to light reflected on the subsystem, particularly the optics in the probe 14. The signal or signals are returned from the probe 14 to the processor 16 through the cabling 15 for processing. While the photoresponsive subsystem typically includes a CCD array or other transducer(s) , the photoresponsive subsystem in the probe may be pas¬ sive, such as an optical wave guide or bundle of guides suitable to carry an image back to the processor where a photoelectric array may be located to respond to the image. The probe optics focus an appropriate image on the active or passive component of the subsystem used to pass information back to the processor. The opening 25 provides a field of view to the illumination light source 23.and to the optics 22 of the photoresponsive subsystem of the probe 14 of the surface of the specimen 12 against which the end 24 of the probe 14 is placed. Preferably the optic elements of the probe 14 have a central optical axis which, in the case of the probe 14 of the present example, is preferably coincident with the central axis of the outer tubular housing 20 and center axis of opening 25. This central, coincident axis is indicated diagrammatically at 26 in the figures. Mounted at the one working end 24 of the probe 14 is a first embodiment, mechanical type centering device of the present invention, which is indicated generally at 30 in the figures. Referring to Figs. 2 and 3, the basic centering device 30 preferably comprises an alignment member, indicated generally at 40, and biasing means, indicated generally at 50. Referring specifically to Fig. 3, the preferred alignment member 40 has a central axis which is at least generally coincident with the central axis 26 of the probe 14. The alignment member 40 has two axial sides, indicated generally at 41 and 42. The alignment member 40 is preferably formed by two interfitted pieces 40a, 40b defining four arms 43, 44, 45 and 46 extending radially with respect to the central axis of the centering device, as represented by the coincident central axis 26 in the figures. Each of the pieces 40a, 40b and each of the arms 43-46 is perpendicular to its adjoining neighbor. This is best seen in Fig. 2. The central portion of each arm 43-46 extends radially away from the axis 26 with a radius of curvature "r" forming a convexly curved quarter round outer surface. After curving through an arc of approximately ninety degrees, each arm 43-46 thereafter extends radially outwardly from the central axis 26 in a direction generally perpendicular to said axis 26. Collectively, the radiused portions of the arms 43-46 form an alignment guide protruding generally concentrically with respect to the central axis 26 on one axial side 42 of the alignment member 40 through the opening 25. As is indicated in Fig. 2, the arms 43-46 leave open a major proportion of the central area of the alignment guide, which is the portion of alignment member 40 circumscribed by the opening 25 in end 24 of the probe 14. This open central area permits light to pass freely between the optical component(s) within the probe and the opposing specimen 12, whereby the field of view of the optics 22 of the probe 14 through opening 25 is at least substantially unblocked, permitting the probe 14 to make/take optical readings axially through the alignment guide 40. The alignment member 40 is biased away from the proximal end 24 of the probe housing by the biasing means. Preferably the biasing means is provided in the form of a coil spring also identified by the same reference number 50. Preferably, the alignment member 40 and biasing means spring 50 are held concentrically with respect to one another and the central axis 26 by a the coupling means 60, which is preferably provided in the described embodiment by a generally tubular collar member, indicated by the same reference number 60. The collar 60 may be an original portion of the housing of a new probe or an adaptor for replacement of an end portion of an existing probe housing. Coupling collar 60 preferably includes a generally cylindrical wall 62, concentric with the central axis 26, preferably threaded on an inner circumferential side at one end to engage threading which has been provided on an adjoining tubular portion of housing 20 of the probe 14. An annular flange 64 extends radially inwardly from the cylindrical wall 62, at the end of the wall spaced farthest from the remainder of the probe 14, and defines the surface of the one end 24 of the probe and the opening 25 therethrough. The flange 64 retains the alignment member 40 and biasing means spring 50 within the probe 14. In this way, the coupling collar 60 couples the alignment member 40 and biasing means spring 50 with the remainder of the probe 14 such that the central axis of the alignment member 40 is generally coincident with the central axis 26 of the probe and opening 25 and such that the alignment member 40 is supported for movement in the axial direction with respect to the probe 14, biased away from the remainder of the probe 14 by the biasing means spring 50. The alignment member 40 may be formed, for example, by a pair of planar, stamped metal pieces which are slotted and interfitted perpendicularly at their centers to form the four radiating arms 43-46. It is envisioned each arm might be approximately fifteen mils thick and at least about one hundred twenty-five mils high with a radius of curvature "r" of 5 mm to mate with a circular indentation 13 in the surface of specimen 12 formed by a 10 mm diameter circular Brinell penetrator. Where a circular penetrator of a different diameter is employed, the radii of the curvature of arms 43-46 are adjusted accordingly. Preferably, the centering device 30 further comprises a ring member 70 sized for slidable movement within the adjoining outer tubular portion of housing 20 of the probe 14. Ring member 70 assists in keeping the biasing means spring 50 in concentric position and in keeping the alignment guide 40 from pitching severely, causing it to possibly dislodge from the probe 14 or jam within the probe 14. Preferably, too, the alignment member 40 is coupled with the ring member 70 in a way which retards relative movement between the alignment member 40 and the ring in member 70, such as, for example, by the provision of slots at the lower end of the ring member 70 which receive each of the arms 43-46. Preferably, the arms 43-46 of the alignment member 40 are fixedly secured with the ring member 70 by soldering, spot welding, adhesive, frictional engagement or other means suitable for the materials selected to form an integral structure, which itself constitutes an alternate embodiment alignment member of the present invention. It is further contemplated that the centering device 30 of the present invention will include switch means, indicated diagrammatically at 80, which are configured and located to respond to the depression of the probe 14 against the specimen 12 after receipt of the centering structure 48 in a Brinell penetrator indentation, such as indentation 13 illustrated in Fig. 3. The switch means 80 will be discussed further with respect to the following discussion of the operation of the centering device 30 with the probe 14. The optical, working end 24 of the probe 14 with the centering device 30 is positioned by the operator against the surface of specimen 12 bearing one or more of the Brinell indentations 13. The operator moves the probe 14 across the surface of the specimen 12 with the centering structure alignment guide 48 contacting and running across the surface, visually aligning the probe with an indentation until the protruding centering structure 48 is caught in the indentation 13. Once the centering structure enters the indentation 13, the annular flange portion 64 of the coupling member 60 at end face 24 is pressed against the facing surface of the specimen 12 to automatically center and vertically align and space the probe 14 with respect to that surface. In this way, the probe 14 can be virtually automatically aligned with respect to the indentation 13 in a manner which eliminates the incremental movement required of prior instruments without the present centering device. It also eliminates the need to generate a specimen surface display for the operator, thereby greatly reducing the computation load on the processor 16 and greatly increasing the response time of the portable instrument 10. Preferably, the switch means 80 is one that will respond to the upward movement of the alignment member 40, for example, a switch means responsive to the movement of the ring member 70 or alignment member 40 away from a position occupied by either of those members before alignment is achieved and the probe depressed against the specimen surface. Such a switching means can include, for example, but is not limited to a throw switch, a momentary contact switch, a Hall effect or other proximity switch, a photoresponsive element exposed (or covered) by movement .of the ring member 70, a pressure switch responsive to the change in biasing force of the biasing means spring 50, a contact switch formed by overlapping contacting conductive portions of the ring 70 and housing 20 or alignment member 40 and coupling means/member 60 or any number of other possible switching means, any of which could be selected and incorporated into the centering device 30 (and/or the probe 14) in any of a variety of ways. The processor 16 of the instrument 10 can be configured to respond to such a signal to begin a series of automatic measurements and computations leading to the derivation of a Brinell hardness value assigned to the specimen 12 as a result of automatic diametral measurements of the indentation 13. It is further believed that the alignment member 40 can assist the instrument 10 in its diametric measurement by improving distribution of the illumination source lighting within the impression. At least one and preferably plural illumination light sources, for example a plurality of individual LED's, are located in or on the probe housing 20 spaced radially from the optical axis 26 and preferably uniformly angularly spaced around that axis, pitched at an angle to that axis, for example about forty-five degrees, so as to direct illumination light through the aperture 25 and an open center of the alignment guide centering structure 48 into the impression 13 at an angle to the central axis 26 so as to strike the various sides of the alignment member 40 which in turn reflect and disperse the light within the impression 13. By illuminating the interior of the impression 13 in this fashion, a greater contrast can be obtained between the impression 13 and the adjoining exposed surface of the sample 12. Centering devices of the present invention can equally be incorporated into microscope-type Brinell hardness-determining instruments. The centering device 30, for example, would again be incorporated into the optical working end of the scope, either during original design and manufacture of the scope or, in at least some cases, by being retrofitted into a conventional instrument. Scope-type instruments are typically provided with a reticle having a single diametral axis which is gradiated numerically from the left to right. Typically, the operator attempts to align the reticle with the Brinell penetrator indentation in a way in which the operator can read off the diameters of the indentation. This typically requires considerable incremental movement of the scope to properly position the reticle with respect to the indentation. The centering device of the present invention greatly simplifies not only the alignment process but the subsequent measurement process of such scopes. Since the centering structure of the centering device of the present invention aligns the optical axis of the scope with the center of the indentation receiving the centering structure 48, a cross-hair type reticle like reticle 100 in Fig. 4 can be provided inscribed with diametral as opposed to radial values along each radial arm ( M 1 H , "2", "3", "4" mm, etc.) of the cross hair so that the operator can tell, at a glance, by simply reading the numbers from the gradiated scale, the diameter(s) of the indentation regardless of the rotational position of the scope. In addition, because the centering device of the present invention accurately aligns a scope on which it is installed concentrically with an indentation to be measured, it permits the possibility of providing GO/NO-GO type reticles for product grading. Such a reticle would be scored or otherwise marked in some way, for example, to provide a circle like circle 102, or segments of such a circle, to indicate a maximum indentation diameter corresponding to a minimum specified hardness. Thus, in Fig. 4 indentation 13 lies within circle 102 indicating the sample is sufficiently hard. Where a hardness range is to be verified, a pair of GO/NO-GO circles or the like could be provided, one to indicate a minimum diameter permitted by a maximum hardness tolerance for a specific material and a maximum diameter marking for a minimum hardness tolerance permitted for the material by the specification. The operator would simply verify that the rim of the indentation 13 lies within the two sets of marking to assure that the sample lies within the specified hardness tolerance range. In addition, many Brinell hardness-testing scopes are provided with removable eye pieces which contain the reticle. Thus, such instrument could easily be modified to measure different hardnesses or to measure indentation diameter to determine a hardness simply by substituting a different eye piece. In addition, in those existing scopes in which it would be difficult to retrofit a centering device of the present invention without altering the spacing of the original working end of the scope from its optics, it would be possible to add a centering device to the existing working end of such a scope and provide a new eye piece, the optics of which are altered to take into account the increased spacing provided between the optics from the addition of the centering device to the working end of the scope. Referring to Figs. 5-7, a second embodiment centering device 130 of the present invention, which is mounted on the probe 114 of a preferably portable instrument for determining Brinell hardness of a specimen by diametric measurement of a Brinell indentation in the specimen. Apart from the below noted changes in probe 114, the instrument is preferably otherwise like the instrument 10 of Fig. 1. Probe 114 includes a housing indicated generally at 116 containing a photoresponsive subsystem with at least some optics, which probe optics are indicated diagramatically at 118. One or more artificial illumination sources, indicated diagrammatically at 119, are provided on the probe 114. Again, the source(s) 119 can be configured to direct light parallel to a central axis 124 of the probe or at an angle to that axis. One end 120 of the probe is preferably planar to be placed on a planar specimen surf ce indicated at 12. The housing has an opening 122 at the one probe end 120 which is at least generally aligned and, preferably coaxial with respect to a central axis 124 of the opening and housing and to the optics 118 so as to provide to the photoresponsive subsystem including the probe optics 118, a field of view of the specimen surface 12 through opening 122 when the one end 120 is located against the specimen surface 12. Opening 122 is also sufficiently large so as to provide to the optics 118 a field of view of the specimen surface 12 opposite the one end 120 sufficiently large to fully view and permit the diametric measurement of any Brinell indentation 13 in surface 12 aligned opposite the opening 122. Centering device 130 preferably comprises an alignment light source 134 separate from the illumination source 119, which generates a beam 140 of visible light as an alignment guide. "Visible light" as used in this application refers to the visible light spectrum of wavelengths between about four and seven thousand angstroms. Light source 134 is preferably located on the exterior of the probe housing 116 so as to not interfere with the field of view of the probe optics 118. A cut-out 126 is preferably provided in a side wall of the housing 116, proximal the one end 120. Source 134 is preferably oriented to direct alignment guide beam 140 through cut-out 126 and through the opening 122 and out of the housing 116. The center of beam 140 might be aligned to intersect the central axis 124 in the plane of the one end 120 where the central axis 124 would normally intersect the planar surface of the specimen 12 against which the one end 120 was placed. The beam 140 produces a visible light illumination intensity level at opening 122 greater than the level produced there by illumination source 119 and sufficiently great to permit an operator to align the probe end with an indentation in a specimen surface using only the light beam 140 to locate the probe opening and guide it to an indentation. While the probes of known, electro-optical Brinell hardness determining instruments include an illumination source 119, such source is either infra-red or produces low level visible light. The former obviously produces no level of visible light intensity while the latter produces visible light which is very faint and diffuse to minimize glare and to otherwise enhance illumination of a Brinell indentation for measurement purposes only. Neither type of illumination source has been adequate to enable an operator using such instruments to use the illumination source alone to align the probe end with Brinell indentations. Preferably, light source 134 is a compact laser generating a very intense beam of visible light 140 having a diameter on the order of only about one millimeter or so. The smaller the diameter of the beam, assuming the beam is still of a sufficiently high illumination intensity, the more quickly and closely the probe central axis 124 and opening 122 can be aligned with the Brinell indentation in the specimen surface 12 by an operator simply observing the probe end 120 on specimen surface. Further fine alignment, if necessary, would be performed through an operator display providing a magnified view of the surface through the probe optics. However, more sophisticated instruments include the capability of determining Brinell indentation diameters, even when the indentation is off-center and out of exact alignment with the central axis 124 of the probe 114. The present invention can thus be used with such instruments as the sole means provided for alignment of the probe end 120 with the indentation 13 for measurement purposes and an operator specimen surface display dispensed with entirely. Again, this is particularly valuable with portable units where specimen surfaces must be computer generated for display on a liquid crystal device. In newly designed instruments, the light source 134 can be incorporated into the design of the probe housing. In the absence of such original incorporation, it may be necessary to mount a light source 134 in some way, such as with a collar 136, which might be designed to replace a similar collar of similar diameter originally provided at the one end of the probe 114. A threaded coupling between the replacement collar 136 and the remainder of the probe 114 is indicated at 138. Collar 136 would replace an original, cylindrical portion of the housing 116 and would contain an opening 122 identical or at least nearly identical in size to the original opening at the one end of the original probe 114. Not only does cut-out 126 provide a means for passing the light beam 140 from the exterior of the housing 116 through the housing and then through the opening 122, it permits an operator to view the beam's impact on the specimen surface, when the end 120 is placed against the surface, so as to more closely align the probe central axis 124 with the center of a Brinell indentation 13 beneath the one end 120 of the probe. While a laser light source 134 is preferred, a non-coherent visible light source together with a suitably configured optical system can be provided to generate a beam of bright, non-coherent, visible light passing through the opening 122 at the one end 120 of the probe sufficiently narrow to permit alignment of such beam and the central axis 124 with a Brinell indentation 13. Preferably, such beam, if directed through a cut-out like cut-out 126 and through opening 122, would be sufficiently sharp and narrow to prevent or, at the very least, minimize reflections from the inner and outer walls of the probe housing 116, which might interfere with the operator's view through the cut-out. It is also believed possible to eliminate separate light source 134 and to provide a visible light illumination source which is operated at high and low illumination intensity levels for initially aligning the probe end with the indentation and then measuring the diameter of the indentation. Moreover, while direct projection of the beam 140 from the light source 134 through the cut-out 126 and opening 122 is shown, one of ordinary skill will appreciate that the beam 140 could be directed through the opening 122 in other ways. For example, a transparent planar lens might be provided in housing 116 and oriented so as to not interfere with light transmitted from the opposing end of the housing 116 through the opening 122 or reflected back from an indentation 13, and yet oriented to reflect the beam 140 downward through the opening 122. In this way, it might be possible to virtually align at least a portion of the beam passing through the opening 122 coaxially with the central axis 124, as the axis projects from the one end 120 of the probe 114. Centering device 130 preferably further comprises a switch, indicated diagrammatically at 144, coupled with light source 134 to selectively manually activate and extinguish the alignment light source 134 separately from any operation of the illumination source(s) 119. Alternatively, the alignment light source 134 and the instrument can be configured so that activation of source 134 is controlled by the instrument to synchronize the extinguishing of light source 134 with operation of the illumination source(s) 119 provided when the diameter of the indentation is actually being measured, or vice versa. Where the photoresponsive subsystem is essentially insensitive to the frequency of the alignment beam light, for example, where an infra-red detector is used, it may be possible to operate light source 134 continually. Again, the visible light source(s) 119 may be configured to operate at different intensity levels for alignment and measurement steps and to be switched between those levels, either manually or automatically under control of the system, for example, when a signal is generated to control the taking of a diametric indentation measurement. While this preferred embodiment of the invention comprises a laser mounted on the probe 114, the alignment light source 134 might alternatively comprise an incandescent bulb, high intensity LED or other conventional visible light generator with a focusing lens or lens train. Also, one of ordinary skill will appreciate that the laser, incandescent bulb or other light generator might even be located remotely from the probe, for example, in the processor portion of the instrument, and light produced by the generator carried through the cabling 115 to the probe 114 by suitable means, such as a fiber optic wave guide, to be projected from inside the housing 116 through the opening 122. The illuminated end of the fiber optic wave guide in such an embodiment would constitute the alignment light beam source associated with the probe. Also, one of ordinary skill will appreciate that if a non-coherent light source is used for alignment, the light source might be used simply to generate visible, non-coherent light within the housing 116. The housing interior and/or its opening 122 can be configured to confine the light to a defined beam 140 projecting from the one end 120 through the opening 122, like a flashlight. One of ordinary skill will further appreciate a significant benefit of the centering devices of the present invention in simplifying the process of aligning the working end of a Brinell hardness determining instrument with a Brinnell impression in a specimen surface, to make the alignment process quicker and at least as accurate if not more accurate and, further, the benefit of eliminating the need to provide or generate a display reproducing a specimen surface for an operator. One of ordinary skill will appreciate that it may be desirable to combine centering devices 30 and 130 in a single instrument to achieve faster, more accurate alignment with indentation illumination. While preferred mechanical and photomechanical centering devices for electro-optically configured and optically configured Brinell hardness determining instruments has been described and variations to the instruments and preferred devices suggested, still other variations thereto are clearly possible and would be known to others of ordinary skill in this art. Accordingly, the invention is not limited to the precise embodiment disclosed but rather is intended to cover any modifications which are within the scope and spirit of the invention, as defined by the appended claims.

Claims: WE CLAIM: 1. In an electro-optical instrument for determining hardness of a specimen by diametric measurement of an indentation in a surface of the specimen, the instrument including a probe and an electronic processor coupled with the probe, the probe including a housing with an opening at one end thereof, the probe further including artificial illumination means located for illuminating a specimen surface through the opening and optics means within the housing located for viewing the specimen surface exposed through the opening and illuminated by the illumination means, an improvement comprising a centering device mounted on the probe, the centering device having an alignment guide projecting through the opening, the alignment guide entering an indentation when the indentation is at least generally aligned with the opening. 2. The centering device of claim 1 comprising an alignment light source separate from the illumination light source, the alignment light source being mounted on the probe to project a beam of visible light out of the housing through the opening and the alignment light source developing a visible light intensity level at the opening greater than an intensity level of visible light developed at the opening by the illuminating light source, the alignment guide comprising the beam. 3. The centering device of claim 2 wherein the alignment light source comprises a laser. 4. The centering device of claim 2 wherein the alignment light source comprises a non-coherent visible light generator. 5. The centering device of claim 2 further comprising an activation switch coupled with the alignment light source to permit .selective activation of the alignment light source. 6. The centering device of claim 5 wherein the activation switch is located on the probe for manual operation. 7. The centering device of claim 1 comprising an alignment light source separate from the illumination light source, the alignment light source being mounted on the probe so as to project a beam of visible light out of the housing through the opening, and an activation switch coupled with the alignment light source to selectively activate and extinguish the alignment light source separately from the illumination light source, the alignment beam comprising the alignment light source beam. 8. The centering device of claim 7 wherein the alignment light source comprises a laser. 9. The centering device of claim 7 wherein the alignment light source comprises a non-coherent visible light generator. 10. The centering device of claim 7 wherein the activation switch is located on the probe and configured for manual operation. 11. The improvement of claim 1 wherein the illumination source of the probe develops visible light passing out of the housing through the opening, and wherein the centering device comprises means for selectively varying visible light intensity developed at the opening by the illumination source between relatively high and low levels, whereby light of the relatively high intensity level of the illumination source constitutes at least part of the alignment guide. 12. The improvement of claim 11 wherein the means comprises a switch on the probe configured for selective activation by an operator. 13. The centering device of claim 1 comprising: an alignment member having a central axis and two opposing axial sides, the alignment guide comprising a portion of the alignment member protruding generally concentrically with respect to the central axis from one axial side of the alignment member through the aperture and forming a centering structure of the alignment member shaped to mate with a generally circular indentation in the specimen surface, a central portion of the alignment member further being configured to freely pass light axially through the alignment member generally around the central axis whereby the field of view of the instrument through the opening is at least substantially unblocked. 14. The centering device of claim 13 further comprising biasing means concentrically positioned with respect to the alignment member and the probe housing for biasing the one side of the alignment member and the centering structure axially through the opening away from a remainder of the probe. 15. The centering device of claim 14 further comprising coupling means for coupling the alignment member and the biasing means with a portion of the probe housing containing the optics such that the central axis of the alignment member is at least generally coincident with a central axis of the probe optics and the alignment member is supported for movement in the axial direction biased away from the remainder of the probe by the biasing means. 16. The centering device of claim 13 wherein the alignment member includes at least three arms extending radially with respect to the central axis, each of the arms protruding generally axially on the one side of the alignment member so as to collectively define at least part of the alignment guide centering structure of the alignment member protruding from the one end of the probe through the aperture. 17. The centering device of claim 16 wherein the one axial side of each of the arms is radially curved. 18. The centering device of claim 17 wherein the alignment member further comprises a tubular member having openings extending radially therethrough receiving each of the arms, the tubular member being positioned concentrically with respect to the central axis. 19. The device of claim 13 further comprising switch means for responding to the movement of alignment member when the one end of the instrument is moved towards the sample after mating of the centering structure with a Brinell indentation. 20. In an instrument for determining hardness of a specimen by diametric measurement of an indentation in a surface of the specimen, the instrument including a housing with an opening at one end thereof, and optics within the housing configured for viewing the specimen surface exposed through the opening, an improvement comprising a centering device including an alignment guide projecting through the opening, the alignment guide entering an indentation when the indentation is at least generally aligned with the opening and the alignment guide. 21. A centering device to improve a Brinell hardness-determining instrument, the instrument having an end configured for placement on a specimen surface to be examined and an opening through the end providing to optics within the instrument a field of view of the specimen surface on which the end of the instrument is placed, the centering device comprising: an alignment member having a central axis and two opposing axial sides, a portion of the alignment member protruding generally concentrically with respect to the central axis from one axial side of the alignment member through the opening to form a centering structure of the alignment member shaped to mate with a generally circular indentation in the specimen surface, a central portion of the alignment member further being configured to freely pass light axially through the alignment member generally around the central axis whereby the field of view of the instrument through the opening is at least substantially unblocked. 22. The centering device of claim 21 further comprising: biasing means concentrically positioned with respect to the alignment member and the instrument for biasing the one side of the alignment member and the centering structure axially away from the instrument through the opening. 23. The centering device of claim 22 further comprising: coupling means for coupling the alignment member and the biasing means with the instrument such that the central axis of the alignment member is at least generally coincident with an optical axis of the instrument and the alignment member is supported for movement in the axial direction biased away from the instrument by the biasing means. 24. The centering device of claim 21 wherein the alignment member includes at least three arms extending radially with respect to the central axis, each of the arms protruding generally axially on the one side of the alignment member so as to collectively define at least part of the centering structure of the alignment member protruding from the one end of the instrument through the opening. 25. The device of claim 24 wherein the one axial side of each of the arms is radially curved. 26. The device of claim 24 wherein the alignment member has four arms, each arm being perpendicularly positioned with respect to each immediately adjoining arm. 27. The device of claim 26 wherein the alignment member further comprises a tubular member having openings extending radially therethrough receiving each of the arms, the tubular member being positioned concentrically with respect to the central axis. -32- 28. The device of claim 21 further comprising switch means for responding to the alignment member when the one end of the instrument is moved towards the sample after mating of the centering structure with a 5 Brinell indentation. 29. The centering device of claim 21 in combination with a reticle for a Brinell hardness- determining microscope, the reticle being marked with at least a pair of perpendicular gradiated axes. 10 30. The centering device of claim 21 in combination with a reticle for a Brinell hardness- determining microscope, the reticle being marked with a gradiated axis bearing numerals indicating diameters along the axis. 15 31. The centering device of claim 21 in combination with a reticle for a Brinell hardness- determining microscope, the reticle being marked with single diametral measurement to indicate a specific Brinell hardness diameter for GO/NO-GO hardness testing.

Inventors: BAKER GORDON M, MAZZOLENI GIANCARLO, BAKER, GORDON, M., MAZZOLENI, GIANCARLO
Applicants: NEWAGE IND INC, NEWAGE INDUSTRIES INC.
Application year: 1992
Main classification: G01N3
IPC codes: G01N3