Abstract:
A device for measuring rigidity, flexibility, and other properties associated with deformation of a thin planar material sample such as carpeting is described. The device is portable and can be manually operated. The device includes a movable testing assembly which is used to urge a testing member against a sample and measure compressive force(s) relative to deformation of the sample.

Description:
FIELD OF INVENTION 
     The present invention relates to a device for measuring rigidity of carpeting or similar materials. 
     BACKGROUND OF THE INVENTION 
     In manufacturing and assembly environments, it is frequently desired to assess certain characteristics of materials such as carpeting or flexible panel-like materials in their installed state, partially installed state, or in an assembly environment. This presents several difficulties because most testing equipment is not mobile or designed for on-site use. In addition, many testing procedures are destructive in nature such that the sample undergoing testing is physically torn, severed, or otherwise altered. This is undesirable for testing of materials that have already been installed or are in an assembly environment and are about to be installed. Accordingly, a need exists for a portable and non-destructive device for measuring physical properties such as rigidity and flexibility of a thin planar member. 
     Testing carpet is typically performed by cutting or otherwise severing one or more samples from large carpet rolls. The cut pieces can then be subjected to an array of laboratory testing equipment. When attempting to use a portable device to measure or test certain characteristics of carpeting such as its flexibility or rigidity, a common problem is that measurements are not repeatable. That is, measurements can vary significantly between samples from the same source, and between different measurement trials. Accordingly, a need exists for a portable, hand-held device that can measure physical properties of carpeting in a consistent and repeatable manner. 
     SUMMARY OF THE INVENTION 
     The difficulties and drawbacks associated with previously known devices and measuring techniques are overcome in the present invention for a measurement device and related method of using the device. The device is particularly well suited for measuring carpet stiffness. 
     In one aspect, the present invention provides a measurement device for measuring force associated with a material deflection. The device comprises a frame; a material supporting fixture supported by the frame, the fixture defining a rest plane for contacting and supporting a material to be measured; and a testing assembly supported by the frame. The testing assembly includes a testing member in communication with a force gauge. The testing member is positionable between a material deflection position and a retracted position. The rest plane defined by the fixture lies between the material deflection position and the retracted position. 
     In another aspect, the present invention provides a device for measuring properties associated with deforming a thin planar material sample. The device comprises a frame including a main member and a first leg extending therefrom. The first leg defines a distal end. The device also comprises a second leg pivotally attached to the frame. The second leg also defines a distal end. The device also comprises a handle pivotally attached to the frame and in operable engagement with the second leg such that upon pivoting of the handle, the second leg also pivots. The device further comprises a material supporting fixture affixed to the distal end of the first leg. The fixture of the device includes a circular hoop. The hoop defines a face for contacting and supporting a thin planar material sample. The face of the hoop extends within a rest plane. The device further comprises a testing assembly affixed to the distal end of the second leg. The testing assembly includes a testing member and a force gauge. The testing member is positionable between a retracted position and an extended position. The rest plane extends between the retracted position and the extended position. 
     In yet another aspect, the present invention provides a method for measuring force associated with a material deflection. The method comprises providing a device including a frame, a material supporting fixture supported by the frame, the fixture defining a rest plane for contacting and supporting a material to be measured, and a positionable testing assembly supported by the frame. The testing assembly includes a testing member in communication with a force gauge. The method further comprises positioning a material to be tested in contact with the fixture and generally oriented in the rest plane. And, the method comprises moving the testing member from a retracted position into contact with the material and further to a material deflection position. Upon positioning the testing member to a material deflection position, a compressive force applied to the testing member is measured by the force gauge. 
     As will be realized, the invention is capable of other and different embodiments and its several details are capable of modifications in various respects, all without departing from the invention. Accordingly, the drawings and description are to be regarded as illustrative and not restrictive. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic illustration of a preferred embodiment device in accordance with the present invention, the device shown in a retracted position. 
         FIG. 2  is a schematic illustration of the preferred embodiment device in an extended position. 
         FIG. 3  is a detailed view of a material supporting fixture portion of the device. 
         FIG. 4  is a detailed view of a testing assembly portion of the device. 
         FIG. 5  is a view further illustrating relative positions of the device in retracted and extended positions. 
         FIG. 6  illustrates measuring rigidity of a material sample using the preferred embodiment device. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     The present invention provides a measurement device that is particularly well suited for measuring carpet deflection. Carpet deflection measurements provide a quantitative value that relates a particular dimensional deflection value to a corresponding force value. Thus, for example, the present invention device can be used to measure the amount of compressive force applied to a sample of carpet which is required to deflect the carpet 20 mm beyond a flat circular ring. These measurements can be used in comparing different carpet types or comparing properties of a single carpet type at different conditions such as across changing temperatures. 
     Generally, the preferred embodiment measurement device includes a frame, a material supporting fixture affixed to the frame for supporting a sample to be tested, and a testing assembly supported by the frame. The testing assembly includes a force gauge and is positionable with respect to the fixture. The fixture includes a circular ring against which the carpet to be tested is positioned. During testing, the carpet sample is placed between the circular ring of the fixture and the testing assembly. The testing assembly is urged against the carpet to cause the carpet to be deflected at least partially through the ring. A corresponding force measurement is then noted by referring to the force gauge. Each of the main components of the preferred embodiment measurement device is described in greater detail as follows. 
     Frame 
     The frame is preferably a rigid member or collection of rigid members, such as may be formed from metal for example, steel or aluminum. The frame may be provided in a variety of different shapes, sizes, and configurations. However, it is generally preferred that the frame includes a longitudinal main member and at least one leg extending outward therefrom and preferably, from an end of the main member. The leg can extend from the main member at nearly any angle, however a transverse orientation is preferred. It is also preferred that the leg be rigidly attached to the main member, however the invention includes variations in which the leg is movable with respect to the main member. 
     Preferably, a second leg also extends from the main member. This second leg is preferably pivotally attached to the main member. The second leg preferably pivots within the same plane within which lies the main member and the first leg. The second leg pivots between a retracted position in which the distal end of the second leg is farthest from the first leg, and an extended position in which the distal end of the second leg is closest to the first leg. The second leg is preferably attached to the main member at an end of the main member opposite the end to which the first leg is attached. The second leg supports the testing assembly, described in greater detail herein. 
     The second leg pivots about a pivot angle of about 5° to about 30° or more. That is, the pivot angle is the angle extending between the retracted position and the extended position of the second leg. The second leg is preferably engaged with a handle to facilitate pivoting the second leg. The handle is also preferably pivotally attached to the main member and proximate the location at which the second leg is attached to the main member. The handle can be operably engaged with the second leg by one or more straps or other connectors. The present invention includes the use of additional pivoting leg members generally extending alongside the second leg member. These additional pivoting leg member(s) can serve to provide further support for the testing assembly affixed at a distal end of the second leg. 
     The present invention preferably includes a force amplification assembly. That is, it is preferred that such assembly be used to increase and/or govern the amount of force exerted by the pivotable second leg as a result of force application by the handle. Such assembly can be used to provide a specific motion profile for the testing assembly attached at a distal end of the second leg, as the handle is pivoted from one position to another. An example of such a force amplification and/or force governing assembly is a cam assembly and lever arrangement. In such example, the handle can be pivotally attached to a cam element which in turn is pivotally attached to the frame. The cam element can contact an engagement surface of a pivotable member and thereby govern movement of that member. 
     The legs, handle, and other frame components are preferably formed from steel, aluminum, or other rigid materials. 
     Material Supporting Fixture 
     As noted, the material supporting fixture is preferably attached to a distal end, or substantially so, of the first leg member of the frame. The material supporting fixture preferably includes a ring or circular hoop against which a sample to be tested is positioned. The fixture is directed toward the testing assembly, and preferably such that the center of the ring is aligned with a testing member of the testing assembly. Additional details as to the preferred orientation of the ring and testing assembly are described later herein. 
     The fixture can be formed from a wide array of materials, however metals such as steel and aluminum are preferred. A wide array of sizes for the material supporting fixture may be used. Although not wishing to be limited to any particular size, it has been found that a circular hoop having an inner diameter of about 110 mm and an outer diameter of about 120 mm is preferred. 
     The fixture is also preferably positionable with respect to the first leg of the frame. That is, it is preferred that the fixture be selectively positionable and adjustable in at least one direction, i.e. preferably towards or away from the testing assembly. Various mechanical assemblies such as threaded fasteners can be used to provide this adjustable feature. 
     Testing Assembly 
     The testing assembly is preferably affixed to a distal end of the pivotable second leg such that upon pivoting the second leg, the testing assembly is positioned closer to, or further from, the fixture. 
     The testing assembly includes a force gauge and a testing member in engagement with the force gauge. The force gauge can utilize electronic force measuring means, mechanical force measuring means, or both. Preferably, the force gauge measures compressive forces applied to the testing member. The force gauge preferably includes a dial display or can utilize a digital display. It is also contemplated that the force gauge could transmit information pertaining to the measured force(s) to a display device external to the measurement device. A preferred force gauge is a Force Dial Model FDL available from Wagner Instruments of Greenwich, Conn. A typical preferred force range for the gauge is 10 KgF×0.05 KgF. 
     The testing assembly is preferably adjustably affixed to a distal end of the pivotable second leg. By adjusting the position of the testing assembly, and in particular, of the force gauge to the second leg, the relative position of the force gauge to the fixture can be changed as desired. This is particularly desirable since this feature provides positional adjustment of the force gauge relative to the fixture when the device is in an extended position. 
     Preferred Device 
       FIGS. 1-6  illustrate a preferred embodiment measurement device  10  in accordance with the present invention. Specifically, as shown in  FIGS. 1 and 2 , the device  10  comprises a frame  20 , a fixture  60 , and a testing assembly  80 .  FIG. 1  illustrates the device in a retracted position, such as prior to a testing or measuring operation. And,  FIG. 2  illustrates the device in an extended position, such as during a testing or measuring operation. The frame  20  generally includes a longitudinal main member  22  defining first and second ends  24  and  26 , respectively. Preferably affixed to the first end  24  of the main member  22  is a first leg  30 . And, the frame  20  includes a second leg  40  pivotally attached to the main member  22  proximate the second end  26  of the main member  22 . The second leg  40  is preferably pivotally attached to the main member  22  at member G. The resulting assembly of the main member  22 , the first leg  30 , and the second leg  40  is preferably in the form of a U-shape, with the member  22  and legs  30  and  40  all co-planar with one another or at least substantially so. Although the frame  20  is depicted in  FIG. 1  as including a transversely extending section that terminates at the first end  24 , to which the first leg  30  is attached, it will be appreciated that the present invention includes versions in which the main member  20  does not include the noted transversely extending section and instead, includes a first leg that is longer in length than the leg  30  depicted in  FIG. 1 . Furthermore, it is contemplated that the main member  22  and the first leg  30  could be integrally formed with one another. 
     Referring further to  FIGS. 1 ,  2 , and  3 , the first leg  30  defines a first end  32  which is attached, affixed or otherwise formed with the main member  22 . The leg  30  defines a second end  34 , opposite the first end  32 . Attached proximate the second end  34  of the first leg  30 , is the fixture  60 . The fixture  60  comprises a circular ring or circular hoop  62 , a base  66  secured to the second end  34  of the leg  30 , and one or more support members  64  extending between the ring  62  and the base  60 . It will be appreciated that the present invention includes the use of a variety of different structures and assemblies for supporting the ring  62 . Preferably, the ring  62  is positionally adjustable with respect to the frame  20  and its components. The preferred embodiment device  10  includes a positioning assembly which provides for selective adjustment of the position of the ring  62  relative to the end  34  of the leg  30 . A wide array of different positioning assemblies may be used to achieve such selective adjustment. A preferred assembly is the provision of a region of threads along a circular shaft  68 , which is threadedly engaged with a nut  69  or other threaded fastener. The nut  69  is secured or otherwise attached to the ring  62  and/or the support members  64 . Thus, by rotating the ring  62 , support members  64 , and nut  69  about the longitudinal axis of the threaded shaft  68 , the linear position of the ring  62  relative to the frame  20  can be selectively adjusted. The present invention includes an array of other types of positioning assemblies besides that depicted in the referenced figures. 
     Referring to  FIGS. 1 ,  2 , and  4 , the device  10  preferably also comprises the testing assembly  80 . The testing assembly  80  is affixed to a distal end of the second leg  40 . The second leg  40  defines a first proximal end  42  and an opposite, distal, second end  44 . The testing assembly  80  is preferably attached or otherwise affixed to the second end  44  of the second leg  40 , which can be pivoted about its point of attachment G to the frame  20 . The testing assembly  80  includes a force gauge  90  and a testing member  82  generally extending therefrom, the member  82  defining a distal end  83 . The force gauge  90  includes a dial  94  or other display for providing information concerning the amount of force applied to the testing member  82 . As explained in greater detail herein, during a testing or measuring operation, the distal end  83  of the testing member  82  contacts the carpeting or other planar sample undergoing testing. The testing assembly  80  also includes a positioning assembly  84 , which preferably utilizes a rack and pinion geared configuration such that rotation of an actuator  89  causes linear movement of a toothed rack member  86 . For example, referring to  FIG. 4 , rotation of the actuator  89  in the direction of arrow C causes linear movement of the rack member  86  in the direction of arrow D. The force gauge  90  is preferably affixed to the positioning assembly  84  and most preferably affixed to the rack member  86  by a support arm  92 . It will be appreciated that a wide array of other affixment assemblies and configurations could be utilized. 
     Referring to  FIGS. 1 and 2 , the preferred embodiment device  10  also includes a handle  50 . The handle  50  is preferably movably attached to the frame  20 . The handle  50  and its attachment and/or configuration with the frame  20  and the second leg  40  is preferably such that pivoting of the handle  50  causes pivoting motion of the second leg  40  and movement of the testing assembly  80  between extended and retracted positions. Although a wide array of different mechanisms and assemblies can be used to achieve this configuration, a preferred assembly is depicted in the referenced figures. Referring to  FIGS. 1 and 2 , the device  10  preferably includes a stop cam element  70 . The third leg  46  is preferably pivotally engaged with the main member  22  of the frame  20  at member H. The third leg  46  generally extends in a parallel fashion with the second leg  40 . The distal end of the third leg  46  is preferably engaged to the positioning assembly  84  of the testing assembly  80 . The handle  50  is secured to the cam element  70  at member J, and also secured to the main member  22  at member I. The cam element  70  is rotatably attached to the main member  22  and preferably proximate the second end  26  of the main member  22  by member I. Thus, upon movement of the handle  50  and the cam element  70 , the cam element  70  also pivots about member I. Movement of the cam element  70  is transmitted to the second leg  40  by a connecting member  54  extending between the cam element  70  and the second leg  40 . The connecting member  54  is affixed to the second leg  40  by member L and affixed to the cam element  70  by member K. Preferably, the cam element  70  includes a stop surface  72  defined along a side of the cam element  70 . Upon positioning the handle  50  as shown in  FIG. 2  from the position illustrated in  FIG. 1 , the stop surface  72  contacts the third leg  46  and prevents further displacement of the handle  50 . 
       FIG. 5  further illustrates the device  10  in a fully retracted position indicated by the testing assembly  80  and handle  50  shown in solid lines, and the handle shown in position H A . In this retracted position, the distal end  83  of the testing member  82  is in position A. In an extended position, shown by the components  80 ,  50 , and others in dashed lines, the handle  50  is in position H B  and the distal end  83  of the testing member  82  is in position B. It will be noted that a plane X of orientation of the ring  62  is between position A and position B. 
       FIG. 6  schematically illustrates a portion of the preferred device  10  in contact with a sample  98  undergoing a deflection measurement operation. Specifically, a portion of the sample  98  is in contact with the ring  62  of the fixture  60 . The testing assembly  80  including the force gauge  90  is positioned toward the sample  98 , and such that the distal end  83  of the testing member  82  is in contact with the sample  98 . The testing assembly  80  and the force gauge  90  are progressively urged against the sample  98  until a desired amount of deflection of the sample occurs, at which point the corresponding compressive force exerted on the testing member  82  is indicated by a dial  94  or other indicator associated with the force gauge  90 . 
     Methods 
     The present invention provides a method for measuring force associated with a material deflection, such as the amount of deflection associated with a particular force. The method generally comprises providing a device including a frame, a material supporting fixture supported by the frame, the fixture defining a rest plane for contacting and supporting a material to be measured, and a positionable testing assembly supported by the frame. The testing assembly includes a testing member in communication with a force gauge. The method further comprises positioning a material to be tested in contact with the material supporting fixture and generally oriented in the rest plane. And, the method comprises moving the testing member from a retracted position into contact with the material and further to a material deflection position, the rest plane extending between the retracted position and the material deflection. Upon positioning the testing member to a material deflection position, a compressive force applied to the testing member is measured by the force gauge. This method enables quick and convenient measurement of carpet deflection values. It has been discovered that the measurement techniques described herein using the preferred device provide consistent and repeatable measurement values. 
     More specifically, when measuring a carpet sample, it is preferred to place the carpet sample on a level surface, carpet side directed upwards. The compression depth of the device is adjusted to 15 mm, for example. The compression depth is the distance that the distal end of the testing member extends through the circular hoop of the fixture. The force gauge is zeroed and set to a mode in which the peak force measured is noted, sometimes referred to as “peak hold”. The device is then positioned over the carpet sample. The sample is contacted with the hoop of the fixture, and the testing assembly then urged toward the carpet sample. The operator continues to move the testing member against the carpet sample, i.e. by moving the handle of the device, until the compression depth of the device is reached. Care should be taken so as to not introduce significant movement of the device and carpet sample. The peak force measured is then noted. The procedure may be repeated as desired, such as on different regions of the carpet. 
     It will be appreciated that the present invention includes variations of the previously described preferred embodiment device  10 . For example, the invention includes the use of different positioning members, different camming assemblies, different handle provisions, different testing assemblies, and includes variations in the described structures for the material supporting fixture, frame, and testing assembly. 
     Many other benefits will no doubt become apparent from future application and development of this technology. 
     As described hereinabove, the present invention solves many problems associated with previous type devices and measuring methods. However, it will be appreciated that various changes in the details, materials and arrangements of parts, which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art without departing from the principle and scope of the invention, as expressed in the appended claims.