Abstract:
In an apparatus for measuring the extension and contraction properties of filamentous specimens ( 10 ), comprising a housing ( 2 ) with at least two delivery devices ( 4, 8 ) between which a test section ( 12 ) for the filamentous specimen ( 10 ) extends, a force sensor ( 14 ) measuring the force exerted on the filamentous specimen ( 10 ) in the test section ( 12 ), and a heating means ( 18 ) enclosing the filamentous specimen ( 10 ) in the test section ( 12 ) and heating it to a predetermined temperature, it is provided that a positioning means ( 24 ) displaces the filamentous specimen ( 10 ) relative to the heating means ( 18 ) or displaces the heating means ( 18 ) relative to the filamentous specimen ( 10 ) such that, in one end position, the specimen ( 10 ) is placed outside the heating means ( 18 ) and, in the other end position, the specimen is within the heating means ( 18 ).

Description:
BACKGROUND ART 
     The present invention refers to a device and a method for measuring the extension or contraction properties of filamentous specimens. 
     Such testing apparatus are known, for example, under the name “Dynafil” and are available from Textechno, Mönchengladbach Germany (Textile Asia, March 1981, Business Press Limited: Continuous Tester). In these testing apparatus, the filamentous specimens are supplied through a heating tube under adjustable extension or overfeed (shortening) that is constant throughout the test or without an alteration in length, the occurring tensile force being continually measured. Depending on the test parameters set and on the type of specimen, various test methods may be obtained: 
     draw force test of pre-oriented or fully stretched yarns, 
     crimp force test of textured yarns, and 
     shrinkage force test of flat and textured yarns. 
     Another known testing apparatus by the name TYT, available from Lawson Hemphill, continually measures the alterations in length of a filament yarn under constant tensile force while the yam passes through a closed heating tube. Preferably, this test is used to determine the crimp contraction of textured yarns. 
     The known apparatus comprise a test section formed by an inlet and an outlet delivery device and the intermediately arranged heating tube, as well as the force sensor (DYNAFIL) or the device for keeping the filament tensile force constant (TYT). The supply rates of both delivery devices may be varied in common or relative to each other. 
     The melting temperature of the fiber materials usually subjected to such tests is 260° C. at maximum (polyester, nylon 6.6). Therefore, the heating tube temperature of the known test apparatus must always be set below this limit value. Otherwise the yarn would melt and tear in the heating tube when the apparatus is at a standstill or running slowly, as well as when a new specimen is introduced into the test section. 
     Due to this limitation of the heating tube temperature, the maximum possible filament speeds, at which the yarn is still heated to the degree necessary for the test, are limited, too. Depending on the count of the yarn, 100 to 200 m/min can be reached. 
     SUMMARY OF THE INVENTION 
     Starting from this prior art, it is an object of the present invention to improve testers of the type mentioned above such that, on the one hand, substantially higher test speeds are possible and, on the other hand, high temperature resistant specimens can be tested. 
     Advantageously, the invention provides that a positioning means displaces the filamentous specimen relative to the heating means or the heating means relative to the filamentous specimen such that, in an end position, the specimen is placed within the heating means and, in the other end position, the specimen is placed outside the heating means. 
     To this effect, the heating means is not designed as a closed tube as with conventional testers. Rather, it comprises a heating channel with a lateral slot for inserting and removing the specimen, the slot being adapted to be opened and closed automatically. 
     Such a positioning means in connection with the heating means allows for heating temperatures far above the melting temperatures of the fiber materials, e.g. up to 800° C., and thus much higher filament speeds, e.g. up to 1000 m/min, at which the filament reaches the optimum temperature. When the running of the filamentous specimen is to be stopped or a new specimen is to be placed into the test section, the positioning means first moves the specimen—still running at a high speed—out of the heating means. Upon restarting the device, the specimen is first accelerated to the test speed outside the heating means and introduced into the heating channel thereafter. In this manner, melting and tearing of the fibre material in the heating means are excluded. 
     Another advantage of such a high-temperature heating means is that it also allows for the testing of high-temperature resistant fiber materials. Testing such materials in the known apparatus at relatively low heating temperatures does not yield any useful test results. 
     The delivery devices of the present tester may be motor-driven godets or feed rollers with aprons or nip rolls. 
     In a development of the invention, it is provided that additional measuring means are arranged in the test section between the inlet and the outlet delivery device, in front of the inlet delivery device, seen in the running direction of the specimen, or behind the outlet delivery device. These additional measuring means serve to measure friction, filament breaks, entanglements, yarn evenness or yarn count. 
     In a preferred embodiment, it is provided that a means for adjusting and maintaining constant a predetermined pre-tensioning force in the running specimen is arranged in front of the first delivery device, seen in the running direction of the specimen, which may be controlled by the measuring signal from the force sensor picked from the test section. This means ensures an exactly adjustable pre-tensioning force constant during the test. 
     Behind the heating means, seen in the running direction of the specimen, a temperature sensor may be disposed for determining the actually reached specimen temperature. This temperature sensor provides a measuring signal suitable for the temperature control of the heating means. 
     Further, behind the heating means, seen in the running direction of the specimen, a twisting means for generating a false twist in the specimen may be provided. 
     The device of the present invention joins the different test methods of the known test apparatus in one apparatus. In measuring the running filamentous specimen, tests with constant extension or contraction of the specimen and a simultaneous measuring of the force occurring in the specimen become possible. Alternatively, the test may be effected using a constant tensile force acting on the specimen, the speed of at least one of the two delivery devices being continually adjusted. The variation in length of the specimen, which at all times corresponds to the difference in speed between the two delivery devices, is measured continually. 
     At heating temperatures below the melting temperature of the specimen, testing of the standing specimen is also possible. Here—after insertion of the specimen into the tester—either without change in length or with a constant change in filament length, force is measured in relation to time, or, with the force maintained constant, the change in length is measured in relation to the time. 
     In measurements of the standing specimen, an essential advantage of the present invention is that a subsequent measurement may be effected very fast by introducing a new specimen section by means of the delivery devices. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The following is a detailed description of embodiments of the present invention, taken in conjunction with the accompanying drawings. 
     In the figures: 
     FIG. 1 is a partial view of the present tester, 
     FIG. 2 illustrates a means for setting pre-tension, and 
     FIG. 3 illustrates a second embodiment. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring now to the figures, FIG. 1 shows a tester for tensile force or length variation tests of filamentous specimens  10 , arranged in a housing  2 . The specimen  10  can be tested with the specimen standing or running. The tester has at least two delivery devices  4 ,  8  which, as is obvious from FIG. 1, may be godets or feed rollers with aprons or nip rolls  7 . Each delivery device  4 , 18  is driven by a precision motor that has a variable speed regulation and a speed measuring feature (e.g. incremental transmitter, resolver or tachometer generator). 
     In front of the inlet delivery device  4 , a unit  22  is arranged for maintaining constant a predetermined pre-tensioning force in the running specimen  10 , as illustrated in FIG.  2 . This means  22  may be adjusted pneumatically or electronically, the means being controllable by the measuring signal from the force sensor  14  picked at the specimen  10 . The means  22  is set with both delivery devices  4 ,  8  running at the same speed, i.e. without delay, until the force measured by the force sensor  14  matches the pre-tensioning force to be set. 
     The means  22  comprises an inlet-side disk-tensioner  40  via which the specimen  10  is supplied. The specimen  10  is wound upon a reel, at least two complete windings being on the reel  42 . From the motor driven reel  42 , the specimen is passed through an eyelet  43  in a feeler lever  44  and via an outlet-side guiding eyelet  48  to a measuring means  26  or the inlet delivery device  4 , respectively. The feeler lever  44  is pre-tensioned by means of a pressure spring  46 . The spring force of the pressure spring  45  may be adjusted manually or electronically depending on a control signal so that a desired pre-tensioning force may be set in the specimen  10 . The position of the feeler lever  44  controls the motor drive of the reel  42  so that an exactly constant pre-tensioning force acts on the specimen  10 . 
     As an alternative to the means  22  and prior to the beginning of a test, the ratio of the speeds of the inlet and the outlet delivery devices  4 ,  8  may be altered, first with the specimen running, such that the tensioning force in the test section  12  reaches the desired value for the pre-tensioning force. The speed ratio thus determined is to be considered when the tensioning force or the change in length of the specimen  10  is set for the actual measurement. 
     A test section  12  for the filamentous specimen  10  extends between the delivery devices  4 ,  8 . In the test section  12 , a force sensor  14  is provided with which the tensile force in the specimen  10  can be measured. The changes in length of the specimen  10  in the test section  12  are determined from the speed differences between the delivery devices  4 ,  8 . The specimen is deflected in the test section by a filament guiding roller  15  mounted to the force sensor  14  and then enters a heating channel  19  of a heating means  18 . On the side of the heating channel  19  averted from the housing  2 , a slit  20  is provided in the housing  17  of the heating means  18  through which the specimen  10  may be guided out of the heating channel  19 . Thus, in the embodiment illustrated in FIG. 1, the heating means  18  is at least partly retractable into the housing  2  by means of a positioning means  24 , whereby the specimen  10  can be guided completely out of the heating channel  19  by withdrawing the heating means. 
     The housing  17  of the heating means  18  has a mechanically operated pivoting flap  21  which is closed when the heating means  18  is fully withdrawn or fully moved, and which is opened automatically, as soon as the heating means  18  is to be displaced. In the closed position, the pivotable flap  21  avoids too great heat losses. 
     As an alternative, it is also possible, with the heating means  18  stationarily fixed to the housing  2 , to displace the delivery devices  4 ,  8  together with the measuring means  14  in parallel until the test section  12  is outside the heating channel  19 . 
     According to another alternative, the heating means  18  and the delivery devices  4 , 8 , including the measuring means  14 , may be fastened stationary at the housing  2 , with only the specimen  10  in the test section  12  being guided out of or into the heating channel  19  by means of filament guiding means. 
     Due to the fast introduction of the specimen  10  into the heating channel  19 , as well as the fast removal by means of the positioning means  24 , it is possible to operate the heating means  18  at temperatures up to an upper limit of 800° C. and more. This allows for test speeds of more than 1000 m/min. Here, the heating temperature may be set steplessly from ambient temperature to a desired temperature in the heating channel  19 . Moreover, tests of high-temperature resistant fibre materials can be carried out. 
     FIG. 1 illustrates additional measuring means  26 ,  28  that may be disposed in front of, in or behind the test section  12 . These additional measuring means  26 ,  28  serve to measure friction, filament breaks, entanglements, bulk of textured yarns, yarn evenness or yarn count. 
     Behind the heating means  18 , seen in the running direction of the specimen, a temperature sensor  30  may be disposed at the lower end of the heating channel  19 , for determining the actually reached specimen temperature. The temperature signal may be used for heating control and/or control of the transport speed of the delivery devices  4 ,  8 . 
     Further, behind the heating means  18 , seen in the running direction of the specimen, a twisting means  34  for generating a false twist in the specimen  10  may be provided. 
     Behind the outlet delivery device  8 , the specimen  10  may be transported off and cleared by means of a suction means  38 . 
     Using the tester described above, the following measurements may be carried out, for example: 
     Measurement under constant application of force to the specimen 
     In this case, a predetermined constant tensile force is set using varying speed ratios of the delivery devices  4 ,  8 , and the resulting extension or contraction of the specimen is measured under the effect of a predetermined temperature. The extension/contraction measurements are effected by measuring the difference in speed between the delivery devices  4 ,  8 . 
     Measuring the tensile force at a constant change in the specimen length 
     Here, a predetermined extension or contraction is applied by a constant speed difference of the delivery devices  4 ,  8 . The respective resulting tensile force is measured and recorded, with the measurements possibly being carried out at different temperatures in the heating channel and at different transport speeds. 
     Dynamic force-extension tests 
     The speed ratios of the two delivery devices may also be altered under program control during the test. Thus, dynamic force-extension graphs may be measured, for example, by incrementally or continuously increasing the extension and measuring the resulting (drawing) force, which is recorded as a function of the extension. Here, the extension of the specimen  10  is set via the different transport speeds of the delivery devices  4 ,  8 . 
     Force or length variation measurement with increasing filament speed of the specimen 
     To determine suitable parameters regarding the temperature in the heating channel  19  and the specimen speed for the above measurements, preliminary tests of the extension and contraction properties of the specimen  10  may effected with force or length variation measurements at increasing filament speed and constant temperature in the heating channel  19 . 
     FIG. 3 illustrates another embodiment, wherein the specimen  10  may be supplied to a first test section  12   a  via a first supply unit  4 , the test section extending in a heating channel  19   a  of a first heating means  18   a . At the end of the first test section  12   a , the specimen  10  is supplied to a second supply unit  6  via a filament guiding roller  15   a  of a first force sensor  14   a , associated with the first test section, the specimen  10  being introduced into a second test section  12   b  via the second supply unit.  12   a  The second test section  12   b  extends in a heating channel  19   b  of a second heating means  18   b . The second test section  12   b  includes a second force sensor  14   b  at which the specimen  10  is supplied to a third supply unit  8  via a guiding roller  15   b.    
     The supply units  4 ,  6 ,  8  of this embodiment are either godets or feed rollers with aprons or nip rolls  7 . Both heating means  18   a ,  18   b  have a slit  20   a ,  20   b , respectively, through which the specimen  10  may be introduced into the heating channel  19   a ,  19   b . It is evident that the slits  20   a ,  20   b  may be closed as in the embodiment of FIG.  1 . For example, the slits  20   a ,  20   b  may be closed separately or together by a flap adapted to be displaced in parallel or pivoted. 
     The device of FIG. 3 is particularly suited for drawing filament cables or coarse filament strands of 10,000 to 20,000 dtex. 
     Here, the specimen  10  may be pre-stretched in the first test section  12   a  and the final drawing may be done in the second test section  12   b.    
     Also in this embodiment, the housing  17  with the heating means  18   a ,  18   b  may alternatively be retracted into the housing  2 , or, as an alternative thereto, the filamentous specimen  10  may be guided out from the heating means  18   a ,  18   b  with parallel displacement.