Apparatuses and method for measuring the length of elongate flexible objects

Abstract: A roller measurement fixture is comprised of a series of small in-line rollers (20) mounted in rows, forming a receiving cradle or trough (25). An extruded part to be measured is cradled in a semi-circular arrangement of the rollers and straightens as it settles under its own weight. The cradle will accommodate many different cross-sections of extruded part. The rollers are free to rotate as the part is placed into the fixture and properly located. Friction from these rollers is negligible; therefore the part remains in, or attains, its free state, without internal stresses, throughout the loading and measurement process. Thus, the extruded part is limp within the cradle, being loaded so as to contact a head or alignment stop at one end of the cradle. A floating stop (35) riding on the rollers engages the other end of the part and cooperates with a scale (30) on the cradle as a means of acquiring the measurements.

Description: This invention is related to length measurement of elongate flexible parts. Accurate length measurements of e.g. extruded rubber seals are required for production control data collection, capability studies, and shrinkage studies. These seals are long flexible extruded parts having a variety of cross-sectional configurations, generally in length up to 6.1 m (twenty feet) or more. After extrusion, the seals are placed onto a measurement fixture or gauge, and an overall length measurement is recorded. One of the problems with accurately measuring the overall length of such extruded rubber seals is the variation caused by handling the part. Typically, one end of a long part is placed against an end stop in the measurement fixture (such as an aluminium angle or channel, or on a flat wooden boundary board with attached scale) and straightened to extend to its full length where a measurement is recorded. Errors in length measurement will occur if the part is not perfectly straight on the fixture. Another major contributor to errors in measurement is the stretching or compressing (stuffing) of the extruded part while placing it into the measurement fixture. This can create localised tension or compression forces in the extrusion. The coefficient of friction between the typical measurement fixture and the various rubber compounds is high enough to allow a stretched or stuffed part to remain in that altered stage, e.g. such localised forces are not dissipated, while the part is being measured. If a part is not in its "free state" (not stretched or stuffed) when measured, variations and measurement errors will result. A measurement fixture (on which the preambles of the independent claims are based) is disclosed in US 4562743. The fixture is for measuring the extension of a cable when subjected to tension. The fixture includes two pairs of rollers for supporting the cable between ends of the fixture. The cable extends in an unsupported manner between the ends of the fixture and the pairs of rollers and accordingly relies on tension in the cable to maintain the length of cable being measured in a straight line. This measuring fixture is accordingly not suitable for measuring the length of a flexible part which needs to be measured in a completely relaxed or untensioned state. A further measurement fixture is described in US 4604813. The fixture includes two rotatable tables, the distance between which along a base can be varied by means of a screw threaded control means. The fixture is stated to be particularly suitable for measuring a length of a rigid pipe bent in three dimensions and is not suitable for measuring the length of a flexible part which cannot support itself. A primary object of the invention, therefore, is to provide a method and apparatuses by which the length of elongate flexible parts can be measured accurately. According to one aspect of the invention, there are provided novel roller measurement fixtures (as set out in the independent claims 1 and 4) designed to help eliminate both of the problems mentioned above (as set out in the independent apparatus claims). The fixtures are composed of a series of small in-line rollers mounted in one or more rows, forming a receiving cradle device, such that the part to be measured is cradled in a semi-circular arrangement and straightened as it settles under its own weight. The semi-circular cradle device will accommodate many different cross-sections of e.g. extruded seal. The fixtures also contain a scale, for example a stainless steel scale that is used as a means of acquiring the measurements. The cradle is preferably comprised of a series of rows of in-line rollers which are free to rotate as the part is placed into the fixture and properly located. The friction from these rollers is negligible, therefore the part remains in, or attains, its free state, without internal stresses, throughout the loading and measurement process. Thus, it can be characterized that the extruded part is limp within the cradle, being loaded so as to contact a head or alignment stop at one end of the cradle. A floating end stop, preferably with an integral pointer, rides in or along the part cradle, and is used to rest against the free end of the part to indicate the measurement on the scale attached to the fixture cradle. From another aspect, the invention provides a method by which the length of a long flexible part may be measured (as set out in the independent method claim 3), which includes supporting the part at a large number of incremental locations along its length, each support being movable relative to the adjacent surfaces of the part so as to allow the part to straighten and to relax and dissipate any localized tension or compression forces in the part prior to taking the length measurement. Reference will now be made to the accompanying drawings, in which:- Figs. 1 and 2 are schematic diagrams of prior art measurement devices; Fig. 3 is an end view of a measuring device incorporating a cradle embodying the invention, typically installed at the delivery end of an extrusion apparatus; Fig. 4 is an enlarged and broken partial front view of the cradle; Fig. 5 is an enlarged cross-sectional view of the cradle and the rollers, taken along line 5--5 in Fig. 4; Fig. 6 is a plan view of the floating end stop; and Fig. 7 is an end view of the floating end stop. Fig. 1 illustrates schematically the prior manner of measuring long flexible rubber (or the like) extrusions, for example natural or synthetic foam rubber extrusions. Of particular interest are synthetic material extrusions used for weather stripping and sealing in automotive applications, such as around windows, in windows runs or channels, and around doors and trunk lids. These seals are extruded through a die to achieve the desired cross-sectional configuration, which is usually irregular, and cut to prescribed length. Inspection of these extruded parts, particularly length measurement, is required to maintain uniformity and quality. Proper length is needed to avoid problems of installation on production lines. Both short and long extrusions present difficulties to the installer, who is working under time constraint. The cut parts E (lengths) are placed on a flat board 10 (Figs. I and 2), one end against a stop 11, and the length is noted on a rule 12 attached to the board. These parts are flexible and relatively small in cross-section and comparably quite long; for example, a particular extruded seal might be 3.8 cm (1.5 inches) across its greatest cross-section, and up to 6.1m (twenty feet) or more in length, i.e. a width-to-length ratio of the order of 1 :160 or more. The material is often sponge-like and in any event is easily subject to localized compression or tension as the part is manually laid out on board 10, due to its longitudinal resilience. The coefficient of friction between the part and the board can result in internal localized stress (either compression or tension) which affects the true length ( when relaxed) of the part. Also, the part may be (hurriedly) not laid in a straight line, as illustrated in an exaggerated way in Fig. 2. All of these variations, caused in part by haste during the manufacturing operation, may result in parts of incorrect length measurement. In accordance with one embodiment of the invention, a novel roller measurement fixture is provided to help eliminate both of the problems mentioned above. The fixture is comprised of a series of small in-line rollers 20, preferably having rims of like diameter, supported on small shafts 22 aligned in one or more rows 20A, 20B, 20C, within a trough 25 which is an open beam 26 having legs 27A, 27B preferably at right angles to each other, with a small shelf 28 secured across its bottom, at the joinder of the legs 27A, 27B forming a receiving cradle device. The cradle is preferably comprised of the three (or more) rows 20A, 20B, 20C of in-line rollers 20, the rollers of each of which rows are free to rotate on their respective support shafts 22 as the part is placed into the fixture through its open top (see Figs. 3 and 5) and properly located. The shafts are all mounted to extend transverse to the beam 26, and adjacent shafts in each row are spaced apart by a distance slightly greater than the diameter of the rollers whereby the circumferential rim surfaces or peripheries of the rollers facing upwardly in the cradle provide a large number of independent or discontinuous supports or segments for the part, both longitudinally and circumferentially of the part, and extending at least the full length of the part. The friction from these rollers is negligible; therefore the part remains in, or attains, its free state, without internal stresses, throughout the loading and measurement process. Other forms and arrangements of rollers can be used. For example, the rollers can be a single set, each having a large convex peripheral configuration, or a larger number of rows of smaller rollers can be used. In an actual embodiment, three rows of rollers having a diameter of 2.54 cm (one inch) are provided, with their centers spaced apart 1.43 cm (9/16 inch). The rows extend along a cradle beam 6.1m (twenty feet) in length. Thus, it can be characterized that the extruded part is limp within the cradle, and the extruded part to be measured is placed and held by gravity, cradled in a semi-circular arrangement of rollers (see Figs. 3 and 5), and will straighten as it settles under its own weight. Any tension or compression forces temporarily created in the part during handling will be relieved or dissipated, since each roller can move independently of the others, and each provides an incremental support of the part over a very short portion of its total length. The semi-circular arrangement of the rollers of the cradle device will accommodate many different cross-sections of extruded seal or other parts. The fixture includes a stainless steel scale 30 supported on a U-shaped member 32 (see Fig. 5) which is fastened to, and runs the length of leg 27B of beam 26, the scale being used as a means of acquiring the length measurements. The zero point of the scale is aligned with an end stop 34 at the head end of the fixture. A floating end stop 35 (see Figs. 3, 6 and 7) with an integral pointer 36 rides in and along the part cradle, being cylindrical in shape and simply slidably supported on rollers 20, This stop is used by rolling it against the free end of the part to indicate the part length measurement via the arm or pointer 36 extending toward scale 30. While the method and the apparatuses herein described constitute preferred embodiments of this invention, it is to be understood that the invention is not limited to this precise method and apparatuses, and that changes may be made in either without departing from the scope of the invention, which is defined in the appended claims.

Claims: A fixture for measuring the length of elongate flexible parts of different cross-sections, said parts being incapable of self-support in a straight line, comprising: an elongated support means (25, 27); a plurality of rollers (20) having rims of like diameter arranged along said support means to present a series of support surfaces; and support shafts (22) for said rollers (20) extending through the axes of rotation of said corresponding rollers (20), said shafts (22) extending parallel to each other and transversely of said support means (25, 27) whereby circumferential rim surfaces of said rollers facing upward in said support means provide a part support of discontinued segments of a full length of a flexible part placed on and extending along said fixture, characterised in that : i) said fixture is for measuring extruded parts formed of foam rubber or like material; ii) said support means comprises a cradle (27) including an upwardly open trough (25); iii) said rims of said rollers (20) are aligned seriatim in said trough (25) whereby said support surfaces of said rims are arranged in a line; iv) said shafts (22) are spaced apart a distance slightly greater than the diameter of said rollers (20); and v) said fixture further includes a scale (30) attached to and extending along said trough (25), an end stop (34) at one end of said trough for indexing said part placed thereon, and a floating stop (35, 36) movable along said rollers into engagement with a free end of said part and cooperating with said scale (30) to indicate the length of said part, wherein localised tension and compression of said part will dissipate due to said part being supported independently at relatively closely spaced increments along the length of said part. A fixture as defined in claim 1 wherein said trough (25) is formed by a beam (26) having an upwardly open top, a bottom, and opposed sides (27A, 27B), and said rollers (20) are supported in alignment along said beam (26) from the bottom and sides thereof in at least three rows (20a, 20b, 20c) of aligned roller supports for confining said elongate flexible part therein. A method of measuring the length of elongate flexible parts which are incapable of self-support in a straight line, comprising: supporting a part in a substantially straight horizontal position at independent locations spaced lengthwise of said part, each support location being provided by a freely rotatable roller (20) aligned along a support means (25, 27) with axes (22) of said rollers being parallel and each said roller (20) being independently movable with respect to adjacent surface portions of said part, and then measuring the length of said part, characterised in that : i) said method is for measuring the length of flexible extruded parts; ii) said support means (25, 27) comprises a cradle (27); iii) supporting said part comprises supporting it at closely spaced locations along its length by means of said rollers (20), said axes (22) of which are spaced apart a distance slightly greater than the diameter of said rollers (20); and iv) said measuring step is performed with said part being in its relaxed state, whereby said rollers allow said part to expand or contract locally due to the release of tension or compression localised in said part. A fixture for measuring the length of an elongate part which is flexible so as to be incapable of self-support in a straight line, and is longitudinally resilient so as to be prone to changes in length, comprising: an elongate support means (25, 27), a plurality of rollers (20) supported independently in said support means (25, 27) to present a plurality of support surfaces along the length of the part, said rollers being freely rotatable, and spaced apart in the longitudinal direction of said support means (25, 27), support shafts (22) for said rollers (20), said shafts (22)extending generally parallel to each other and generally transversely of said support means (25, 27), whereby said rollers (20) provide support for said part when placed thereon, characterised in that : i) said support means (25, 27) comprises a cradle (27) including an upwardly open trough (25); (ii) said rollers (20) are supported seriatim and at relatively closely spaced intervals along the length of said part; and iii) said fixture further includes a scale (30) attached to and extending along said trough (25), an end stop (34) at one end of said trough (25) for indexing said part placed thereon and a floating stop (35, 36) movable along said rollers (20) into engagement with a free end of said part and cooperating with said scale (30) to indicate the length of said part, whereby said rollers (20) serve to dissipate localised tension and compression in said part, such dissipation being due to said part being supported independently at relatively closely spaced intervals along the length of said part. A fixture as defined in claim 4 wherein said trough (25) is formed by a beam (26) having an upwardly open top, a bottom and opposed sides (27A, 27B), and said rollers (20) are supported in alignment along said beam from the bottom and sides thereof in at least three rows (20a, 20b, 20c) for confining said part therein.

Inventors: MALIK RICHARD, MALIK, RICHARD
Applicants: COOPER TIRE & RUBBER CO, COOPER TIRE & RUBBER COMPANY
Application year: 1997
Main classification: G01B5
IPC codes: G01B5