Abstract:
A clamp for use with a line burner, the clamp having an internal through-hole constructed and arranged to receive a line burner and having an external tapered surface. The tapered surface of the clamp is adapted to align or center the line burner within a hole in a unit for fire spread testing and is adapted to reduce gaps between the line burner and the hole so that flames emitted during fire spread testing from the hole are reduced or eliminated. The line burner may include an indicator constructed and arranged to assist in providing desired alignment of the gases out of the line burner during testing.

Description:
FIELD OF INVENTION  
       [0001]     The invention relates to a clamp. More particularly, the invention relates to a clamp for use in fire spread testing.  
       BACKGROUND OF INVENTION  
       [0002]     Numerous fire testing standards exist to test telecommunications equipment. One particular set of standards often used is the Network Equipment Building Standards (NEBS). This set of standards assures that telecommunications equipment is of a certain quality and remains functional even when catastrophic events such as extreme thermal conditions or earthquakes occur. Equipment is also tested for fire spread, but does not need to function during fire spread testing. The reliability of communications equipment is generally expected to exceed 99.999%. The NEBS standards, particularly GR-63 CORE, ANSI T1.319-2002 and GR-1089 CORE, were created to address issues of reliability of telecommunications equipment for a central office installation. Manufacturers of telecommunications equipment generally have independent laboratories test and certify that their equipment meets the NEBS. Different standards and tests are used depending on the particular technology and equipment involved.  
         [0003]     GR-63 CORE and T1.319-2002 are particular standards under the NEBS that deals with the physical characteristics of the equipment. This standard has different tests, including tests for temperature, humidity and altitude, earthquake simulation and fire spread. The fire spread test determines how a particular unit being tested will react when a flame is introduced into the system, and it particularly tests for fire spread and fire propagation hazard of the unit.  
         [0004]     Typically the unit to be tested is a telecom chassis having circuit cards and other components held within an outer housing. The fire spread test currently used under the GR-63 CORE standard is generally performed as follows: a circuit card is removed from the inside of the telecom chassis, a blank faceplate is placed on the housing approximate to where the circuit card was removed, and a hole having a diameter of approximately three-quarter inch is drilled into the blank faceplate. A six inch line burner is inserted through the drilled hole into the telecom chassis. The line burner simulates a circuit card on fire. Methane gas is used to light the line burner, and it is controlled to a flow profile between 0.5 to over 25 liters per minute, eventually extinguishing at about 5.5 minutes. The line burner may be lit before or after insertion into the telecom chassis.  
         [0005]     Telecommunications equipment is expensive, and the units tested are no longer usable after testing has been performed. As such, it is important that the tests be performed properly the first time, and that the unit does not fail a test because of an error that occurs with the test itself. Improper failures, however, can occur and result in the need to repeat the test. An improper failure can drastically increase the cost of testing and certification of the equipment, as a new unit is typically needed for further testing if the initial test fails. Thus, it is desirable to perform the test correctly the first time to reduce the potential costs of testing and certification.  
         [0006]     Different types of failures can occur with the fire spread test. For example, a test failure can occur when the flames come out the hole drilled in the unit into which the line burner is inserted or if burning occurs for longer than 30 seconds on the outside of the unit. Thus, it is important that test failures be avoided so that retesting is not required.  
       SUMMARY OF INVENTION  
       [0007]     In accordance with this invention, a line burner may be centered within a hole for fire spread testing and/or flames may be prevented from being emitted from the hole used to insert the line burner into a unit under test by providing a clamp on the line burner. This clamp may center the line burner within the hole and/or may reduce or eliminate gaps between the line burner and the hole margin to thereby reduce or eliminate flames emitted from the hole during fire testing.  
         [0008]     In one aspect of the invention, a clamp for use in connecting a rod to a unit is disclosed. The clamp includes an outer surface, first and second ends and a through-hole provided between the first and second ends constructed and arranged to receive a rod. The clamp is adapted to substantially center the rod within a hole in a unit through which the rod is inserted.  
         [0009]     In another aspect of the invention, a clamp for use in connecting a rod to a unit is disclosed. The clamp includes an outer surface, first and second ends and a through-hole provided between the first and second ends constructed and arranged to receive a rod. The clamp is adapted to substantially block the hole in the unit through which the rod is inserted.  
         [0010]     In yet another aspect of the invention, a method of fire spread testing is disclosed. The method includes the steps of: providing a unit to be tested, the unit having a hole, providing a line burner for insertion through the hole into the unit, and providing a clamp having an outer surface with a tapered portion and a through-hole extending through the clamp. The line burner is slid through the through-hole of the clamp, and the clamp is secured to the line burner. The line burner is inserted through the hole in the unit to be tested at least until the tapered portion of the clamp abuts against the hole of the unit, and the line burner is ignited. 
     
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0011]     The objects, advantages and features of this invention will be more clearly appreciated from the following detailed description, when taken in conjunction with the accompanying drawings, wherein like numbers are used for like features, in which:  
         [0012]      FIG. 1  is a perspective view of a clamp according to one embodiment of the invention;  
         [0013]      FIG. 2A  is a side view of the clamp of  FIG. 1 ;  
         [0014]      FIG. 2B  is a side view of another embodiment of the clamp according to the invention;  
         [0015]      FIG. 3  is an end view of the clamp of  FIGS. 1 and 2 A;  
         [0016]      FIG. 4  is a perspective view of the clamp of  FIG. 1  in use on a line burner; and  
         [0017]      FIG. 5  is a perspective view of the clamp of  FIG. 1  in use on a line burner that has been inserted into a unit to be tested.  
     
    
     DETAILED DESCRIPTION  
       [0018]     The present invention is directed to a clamp. The clamp may be used during fire spread testing to align a line burner within a hole in a unit to be tested. The clamp may also be used during fire spread testing to reduce or eliminate gaps between the line burner and the hole margin to reduce or prevent flames from being emitted from the hole during fire spread testing. The unit to be tested includes telecommunications equipment, such as a telecom chassis having circuit cards and other components stored within a housing.  
         [0019]     The embodiment of the invention described below, with reference to a line burner for use in testing telecommunications equipment, particularly telecom chassis, is for illustrative purposes only. It will be understood that the various aspects of the invention are not limited to use with the particular line burner described, but instead may be used with any suitable lighting device that uses gas for ignition, such as lighters for gas grilles, stoves or furnaces. Moreover, it will be appreciated that although the clamp is described for use in performing a particular fire spread test for telecommunications equipment, the clamp may be used in connection with any fire spread test on any device, including devices other than telecommunications equipment. It will also be appreciated that the clamp is not solely for use with testing, but may be used for purposes unrelated to testing with any device to which an ignition source may be connected, for example gas grilles, stoves or furnaces. For example, the clamp could be used on lighters for gas grilles to help prevent flames from being directed back out at the operator.  
         [0020]     Referring now to  FIGS. 1 and 2 A, an illustrative embodiment of a clamp  10  according to the invention is shown. The clamp  10  has tapered and cylindrical portions  20  and  26  and first and second ends  12  and  14 . A through-hole  16  extending from the first end  12  to the second end  14  is provided through the clamp  10  for receiving a rod or pipe. The through-hole  16  is illustrated as being centered within the body of the clamp  10 , although it will be appreciated that the through-hole  16  may be off-set. The through-hole  16  has a diameter d th , while the clamp has a diameter d c  at the larger end.  
         [0021]     The clamp  10  includes an outer sidewall  18 . As illustrated in  FIG. 2A , at least the portion  20  of the sidewall  18  is tapered, and more particularly is frusto-conical in shape. The smaller end of the portion  20  is provided at the first end  12  of the clamp  10 . This first end  12  has a diameter d fe , and this diameter d fe  is substantially the same as the diameter d th  of the through-hole  16 , as illustrated.  
         [0022]     As shown in  FIG. 3 , an opening  22  is provided in the sidewall  18  for receiving a fastener  24  and extends perpendicular to and intersects the through-hole  16 . The fastener  24  is inserted into the opening  22  to lock the clamp  10  in a desired position on a rod or pipe disposed in the through-hole  16  of the clamp  10  (see  FIG. 4 ). Any particular fastener  24  may be used, including a thumb screw, set screw, etc. As illustrated, the opening  22  is provided on the cylindrical portion  26  of the sidewall  18 , although it will be appreciated that the opening  22  may be provided in any suitable location on the clamp  10 .  
         [0023]     Referring now to  FIG. 2A , the tapered portion  20  and cylindrical portion  26  of the sidewall  18  have respective lengths A and B. It will be appreciated that these portions  20  and  26  may have any particular length relative to one another. As shown, the cylindrical portion  26  has a smaller length than the tapered portion  20 , but is wide enough to accommodate the opening  22 . It will be appreciated that the entire sidewall  18  may be tapered with no cylindrical portion  26 . The side wall of the tapered portion  20  has a frusto-conical shape that converges at an angle θ to provide the sidewall with a slope. The angle may be any suitable angle to provide a desired slope to the sidewall  18 , but is preferably between 5° and 85°.  
         [0024]     Referring now to  FIG. 2B , another embodiment of the clamp  10  as shown. In this embodiment, the tapered portion  20  of the side wall  18  has a fluted shape that converges from the cylindrical portion  26  to the first end  12 . In this embodiment the slope of the tapered portion  20  of the clamp  10  is varied, so that it has a radius of curvature with an angle θ that changes along the length of the sidewall  18 . It will be appreciated that the tapered portion  20  may have any shape that allows the diameter dc of the clamp to converge or taper toward the diameter d fe  of the first end  12 . The resulting diameter d fe  may be substantially the same size as the diameter d th  of the through-hole  16 . The shape of the tapered portion  20  may be any suitable shape, including frusto-conical and fluted shapes.  
         [0025]     The clamp  10  is made of stainless steel, although any suitable material may be used, including any metals or plastics. It is preferable that the material be able to withstand higher temperatures and fire, so that during use in fire spread testing the clamp  10  will not be easily damaged. Although the clamp  10  and through-hole  16  have been illustrated and described as having circular cross-sections with diameters, it will be appreciated that either may be provided with any desired shaped cross-section to accommodate the particular shaped hole in the unit to be tested or the particular shaped rod or pipe to be inserted through the through-hole  16 .  
         [0026]     In  FIG. 4 , a line burner  28  is shown. The line burner  28  includes a rod  30  having first and second ends  32  and  34 . The rod  30  is at least partially hollow to receive methane gas for performing the fire spread test, and a line of gas holes  36  extends from the first end  32 . The holes  36  allow the methane gas and flames to escape from the rod  30 . The holes  36  may be provided at any distance from one another and may be provided in any size, but are preferably provided in conformance with the desired fire spread test standard. As illustrated, the line burner  28  includes seven holes in a straight line and spaced equi-distant from one another. The first end  32  of the rod  30  is adapted for insertion through a hole  40  into a unit to be tested  42  ( FIG. 5 ), such as the housing of a telecom chassis. The second end  34  is adapted to be connected to a gas line (not shown). A hook-up assembly  37  is provided at the second end  34  of the rod  30 . The hook-up assembly  37  may be any desired mechanism to connect the line burner  28  to a gas-line.  
         [0027]     A pin  38  extends upward from the line burner  28  adjacent where the line burner  28  is connected to the gas line. As illustrated in  FIG. 4 , the pin  38  is provided on the hook-up assembly  37  itself. The pin  38  indicates to a user the direction in which the line of holes  36  are facing, as the pin  38  is aligned with the line of holes  36 . Thus, even when the holes  36  cannot be seen, such as when the line burner  28  is inserted into the unit to be tested, the position of the line of holes  36  may be determined. The user can then rotate the rod to move the line of holes  36  in a desired direction, such as in a direction to prevent flames from moving along cards in the unit being tested, which may avoid a test application failure. It will be appreciated that the pin  38  may be any suitable indicator provided on line burner to indicate to the user the direction in which the holes are facing, including a raised portion or a colored marker.  
         [0028]     The clamp  10  may be slid over the first end  32  of the rod  30  by sliding the rod through the through-hole  16  to a desired position on the rod beyond the holes  36 . The clamp may be placed at a distance X from the first end  32  of the rod  30 . The clamp may then be secured to the rod  30  by tightening the fastener  24  in the opening  22  until the fastener  24  abuts the rod  30  and hinders sliding movement between the clamp  10  and rod  30 . Hand tightening of the fastener  24  into the opening  22  until it abuts with the rod  30 , is generally sufficient to keep the clamp  10  in place. The through-hole  16  and rod  30  may have substantially the same diameters d th  and d r , so that when the clamp  10  is secured to the rod  30  there should be substantially no relative movement between the two. The clamp  10  is placed on the rod  30  with the first end  12  of the clamp  10  (the smaller end of the tapered portion  20 ) facing the first end  32  of the rod  30  to be inserted into the unit to be tested.  
         [0029]     As illustrated in  FIG. 5 , during use the clamp  10  is placed on the rod  30  as described above at the desired distance X from the first end  32  of rod  30  with the line of holes  36  disposed between the clamp  10  and first end  32  of the rod  30 . The first end  32  of the rod  30  is then inserted into a hole  40  that has been formed in a unit  42 , such as a telecom chassis, to be tested. The rod  30  is slid into the unit  42  until the tapered portion  20  abuts against the hole  40 . This also aligns the line burner to a particular insertion depth within the unit  42 . The first end  12  of the tapered portion  20  of the clamp  10  preferably is smaller than the hole  40  and at least a small part  44  of the clamp  10  will fit within the hole  40  in the unit  42 . The part  44  of the tapered portion  20  within the hole  40  assists in centering the rod  30  within the hole  40 . Additionally, the clamp  10  substantially seals or blocks the hole  40  so that flames are less likely to escape through the hole  40  during fire spread testing.  
         [0030]     Once the line burner  28  and clamp  10  are in place and the second end  34  of the line burner  28  is connected to a gas line, the rod  30  may be rotated to align the pin  38  in the direction that the line of holes  36  are to face. The test may then be performed to the desired standards.  
         [0031]     It will be appreciated that the angle θ of the tapered portion  20  may vary, and that the angle determines how much of the tapered portion  20  of the clamp  10  will fit within the hole  40 . For example, assuming that the diameter d fe  of the end  12  of the clamp is constant for the same size hole  40  in the unit and the tapered portion has a frusto-conical shape with a constant slope at an angle θ, a larger angle will result in less of the portion  20  fitting within the hole  40 , while a smaller angle will result in more of the portion  20  fitting within the hole  40 . It will also be appreciated that the cross-section of the hole  40  and the tapered portion  20  preferably have substantially the same shape, so that a part  44  of the tapered portion  20  fits into the hole  40  substantially without gaps between the two. Thus, the amount of flames escaping from between the clamp  10  and the hole  40  is minimized.  
         [0032]     It will also be appreciated that the tapered portion  20  may converge in any suitable manner from the cylindrical portion  26  of the clamp to the first end  12  of the clamp. Typically, the cross-section of the first end  12  is substantially the same size as the cross-section of the through-hole  16 . Alternatively, the cross-section of the first end  12  may be larger than the cross-section of the through-hole  16  and still fit within the hole  40  in the unit  42 . Thus, it will be appreciated that the tapered portion  20  need not taper until the cross-section of the first end  12  is substantially the same size as the cross-section of the through-hole  16 .  
         [0033]     Having thus described several aspects of at least one embodiment of this invention, it is to be appreciated various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be part of this disclosure, and are intended to be within the spirit and scope of the invention. Accordingly, the foregoing description and drawings are by way of example only.