Abstract:
A soft-sided thermal test chamber that is readily mountable upon/over a shaker test table. The test chamber includes four interconnected insulated side walls and a top which define an enclosure. A two-piece bottom receives the side walls to fully enclose the test object upon the table. The two-piece bottom includes an interchangeable center piece which is sized to accommodate various tables or test objects. The side and top pieces are hung from a frame that is readily lifted using an overhead crane or chain fall hoist to allow easy access to the table during set up. The bottom and side walls are interconnected via hook and loop fasteners, which allows for rapid alteration of the set up of the test equipment while maintaining a thermally sealed chamber.

Description:
FIELD OF THE INVENTION 
     This invention is related to thermal test chambers and, more particularly, to a thermal test chambers that are adapted to transmit a vibrational input to a test object. 
     BACKGROUND OF THE INVENTION 
     A variety of thermal testing chambers having various enclosure configurations have been previously disclosed to enable test personnel to subject a device or devices to different temperature conditions. Oftentimes, this thermal testing is combined with shock vibration testing to help ascertain the quality and reliability of the devices. 
     Vibration testing is conducted by mounting the device to be tested upon a table or base which is in communication with the thermal test chamber and by then vibrating the table. Some prior art examples of such thermal/vibration testing equipment may be found in the following patents. 
     U.S. Pat. No. 6,863,123 issued to Jeng-Yau Wang discloses a metal thermal testing enclosure that is lifted up off a rigid base plate. A rubber barrier allows the enclosure to be mounted upon/over a shaker table. 
     U.S. Pat. No. 5,251,497 issued to Elie Bressan discloses a test enclosure formed of a three-ply polyethylene material that is lifted via an overhead crane over the test stand. A sealing jacket is fixed to the floor surrounding the test stand. The sealing jacket mates with the lowered test enclosure to fully enclose the test stand. An airlock in the enclosure provides access to the test components while the enclosure is in position. 
     U.S. Pat. No. 5,610,344 issued to Ichiro Ueda et al. discloses an environmental test enclosure having a laminated insulated membrane. The enclosure has a rigid framework that is moveable like a curtain upon a rail system to allow access to the test stand. 
     While the prior art discussed above provide some solutions to the problem of providing a thermal test chamber that can be moved to provide greater access to the test stand, they do not provide a modular thermal chamber that can be quickly adapted to different vibrational test stands and which is provides unhindered access to the test objects. 
     One shortcoming of the prior art and commercially available thermal test chambers is that they are formed with rigid enclosure walls, which are effective in maintaining a desired thermal chamber, but inherently limit access to the components to be tested. Further, these test chambers are oftentimes large, expensive, fixed pieces of equipment that occupy a dedicated portion of the testing facility. 
     There is therefore a need for a thermal test chamber that is readily adaptable to differently sized vibrational test stands, while remaining portable and relatively inexpensive. 
     SUMMARY OF THE INVENTION 
     The broad purpose of the present invention is to provide an improved thermal test chamber that is readily mountable upon a shaker test table. The test chamber includes a hood having a number of non-rigid insulated side walls and a top wall which define an enclosure. A flexible two-piece bottom receives the side walls to fully enclose the test object upon the table. The two-piece bottom includes an interchangeable center piece which is sized to accommodate various tables or test objects and a collar. The collar is sized to mate with the side walls to complete the enclosure. The bottom and side walls are interconnected via hook and loop fasteners, which allows for rapid alteration of the set-up of the test equipment while maintaining a thermally sealed chamber. 
     In the preferred embodiment, the thermal test chamber has non-rigid walls and bottom, which enable the hood and bottom to be quickly assembled using high temperature hook and loop fasteners. These walls and bottom are preferably formed by at least one layer of a thermally insulated textile, such as a silicone-impregnated fabric. 
     It is an advantage of the present disclosure to provide a thermal test chamber adapted to be mounted to a top surface of a vibration table for thermal and vibration testing of a test object mounted upon a test fixture. The chamber including a thermally insulated hood and base that are both formed from a pliable textile material. The hood has an internal test cavity with an open bottom end. The base has a bottom wall mounted flat upon the top surface of the vibration table and includes at least one mounting aperture through which the test fixture is coupled to the top surface. In operation, the hood is removably coupled to the base by a continuous fastener running around a lower periphery of the hood, which thermally seals the test fixture within the test cavity. 
     It is another advantage of the present disclosure that the preferred embodiment provides a portable thermal test chamber for mounting to a vibration table. The test chamber is preferably made from a flexible insulative material and includes a base having a flat bottom member and a collar which is removably coupled to the bottom member and forms a generally vertical continuous wall extending from the periphery of the bottom member; a non-rigid enclosure hood having a roof and a plurality of downwardly extending side walls which cooperatively define a cavity. It is along these side walls that the hood is removably coupled to the base&#39;s collar. The portable thermal test chamber uses a hoist coupled to the enclosure hood to lift the hood away from the base. 
     Still further objects and advantages of the invention will become readily apparent to those skilled in the art to which the invention pertains upon reference to the following detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The description refers to the accompanying drawings in which like reference characters refer to like parts throughout the several views and in which: 
         FIG. 1  is a perspective view illustrating the thermal test chamber suspended from a hoist and mounted upon a vibration stand and connected to a forced air heating and cooling unit; 
         FIG. 2  is a view similar to  FIG. 1 , with the heating unit removed and showing a removable insulation panel prior to covering the exposed air port; 
         FIG. 3  is another perspective similar to  FIGS. 1 and 2 , showing a removable air duct adapter panel removed from the hood exposing the air port along with an enlarged access panel opened for access to the test fixture and test objects; 
         FIG. 4  is a partially exploded perspective view showing the hood separated from the base&#39;s collar and bottom panel; 
         FIG. 5  is a partially exploded side sectional view of the hood, collar, bottom panel along with the test fixture, test object, cabling, and shaker table; 
         FIG. 6  is a side sectional view of the mating ends of the collar and hood; 
         FIG. 7  is a side sectional view showing the collar and bottom panel prior to sealing over a test cable; 
         FIG. 8  is a side sectional view of the collar and bottom panel cooperating to thermally seal a test cable that is extending out of the test chamber&#39;s cavity; 
         FIG. 9  is a top plan view of one bottom panel; 
         FIG. 10  is a top plan view of another bottom panel having a different fixture mounting pattern for a different vibrational test stand than the panel shown in  FIG. 9 ; and 
         FIG. 11  is a top plan view of the base collar. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the FIGS., a thermal test chamber  10  is shown having an enlarged enclosure or hood  12  that is removably coupled with a two-piece base  14 . To ensure that the test chamber  10  is relatively light in weight and remains readily portable, the walls and panels of the entire test chamber  10  are flexible and are preferably formed from a pliable insulative textile material surrounding a middle layer of pliable insulation batting. In the preferred embodiment, the outer layer  15  and inner layer  16  are a silicone-based fabric, such as a silicone coated or impregnated canvas. The center layer  17  is a dense fibrous insulation batting, such as a blend of cotton and nylon fibers. The thermal test chamber  10 , through its combination of flexible insulative layers  15 - 17 , remains pliable at a range of operating temperatures. Further, the flexible nature of the thermal test chamber  10  reduces the burden on packaging and shipping the test chamber. 
     The hood  12  has a generally rectangular box configuration with four opposed vertical side walls  18  coupled to a roof panel  19  spanning between and interconnecting the top portion of the four side walls  18 . In one non-limiting example, the hood has a length of approximately eight feet and a width and height of approximately six feet. 
     The four parallel side walls  18  and roof  19  cooperatively define an enlarged test cavity  20  having an open bottom end opposed by the roof  19 . As will be discussed in greater detail below, test cavity  20  is sized to receive a test fixture  22  that supports at least one test object or device  24 . 
     As shown in  FIGS. 1-4 , hood  12  is vertically supported by a rigid tubular frame  26  which is itself coupled to a conventional lifting crane, dead-fall, or hoist  28 . Frame  26  is preferably a continuous rectangular-shaped hoop having the same approximate profile as the four side walls  18  of the hood. The frame  26  is passed through a series of loops  30  fixed to and spaced along the upper end of hood  12 . It should be appreciated that various configurations of lifting devices  28  and appropriate connectors may be envisioned by one skilled in the relevant art to effectively lift the hood  12  vertically at will. 
     As best shown in  FIGS. 4 and 5 , thermal test chamber  10  includes a two-piece base  14 . The two subcomponents of base  14  include a relatively flat bottom panel  32  and an annular collar  34  that is removably mounted to the periphery of the bottom panel  32 . Bottom panel  32  has a substantially planar rectangular shape. One continuous strip of half (denoted  36 A on panel  32 ) of intermeshing fasteners  36 ,  37  runs around the entire periphery of the panel  32 . Intermeshing fasteners  36 ,  37  are preferably a commercially available high strength, high temperature hook and loop fastener with a width of at least one-half inch. In the embodiment illustrated in the FIGS., one half  36 A of the complementary intermeshing fasteners  36 ,  37  is affixed to the top surface  38  of the panel  32 . It should be readily appreciated, however, that the fastener could be mounted to the bottom surface or side edge of a sufficiently thick panel. 
     The other subcomponent of base  14  is a collar  34 . Collar  34  has a relatively narrow (e.g., 2 to 6 inches) mounting lip  40  that surrounds and defines a large opening  42 . Lip  40  is generally horizontal and has an annular vertical wall or ring  44  depending from its outermost edge and rising vertically therefrom. In the embodiment illustrated in the FIGS., the underside of lip  40  has a complementary half  37 A of the intermeshing fastener of panel  32  running around the lip and having the same general shape and size as the fastener  36 A on bottom panel  32 . To that end, lip  40  and bottom panel  32  are placed in an overlapping and abutting relationship and are readily coupled together with these intermeshing fasteners  36 A,  37 A with ring  44  extending vertically from the joined lip and bottom panel and with the opening  42  exposing most of top surface  38 . 
     Another half of intermeshing fasteners  36 ,  37  encircles the outer surface of ring  44 . This fastener half, denoted  36 B in the FIGS., mates with its complementary strip half  37 B running around the lower ends of the inward faces of the four side walls  18 . To ensure that fasteners  36 B,  37 B are capable of forming a seal around the entire bottom end of cavity  20 , lip  40  and ring  44  have the same relative lengths as the four interconnected walls  18 , whereby the four walls  18  and outer surface of ring  44  are in an overlapping and abutting relationship. 
     Referring now to  FIG. 5 , a partially exploded side view of the hood  12 , bottom panel  32 , and collar  34  shows the relative positions of the mating fasteners  36 A,  37 A and  37 B,  38 B. When assembled, the hood  12  and base  14 , have their parallel walls  38 ,  40  and  18 ,  44  in an overlapping and abutting relationship which, through their intermeshing fastener halves, produce a tight bond between the severable components  12 ,  32 ,  34 . The intermeshing fasteners are preferably wide enough to hold fast while ensuring that little thermal energy (i.e., heat) escapes between the abutting panel surfaces, thereby producing a thermal seal that is satisfactory to substantially contain temperatures in the range of −50° F. to 275° F. within an enclosed cavity  20 . 
     Importantly, to maintain a desired temperature within the above range, the hood  12  and base  14  are both formed from a flexible insulative textile material (i.e., the combined insulative layers  15 - 17 , which is preferably interconnected by sewing adjacent panels (e.g., each side wall  18  and roof  19 ) together with a high-temperature thread, such as an alumina-boria-silica fiber or a PTFE thread. 
     While initial set-up of test chamber  10  is preferably done with the hood  12  lifted free of the test fixture  22  and test object  24 , there are often times when it is necessary to make adjustments and/or inspect the fixture or devices when the hood  12  is coupled to the base  14 . Referring now to  FIGS. 2 and 3 , the thermal test chamber  10  includes a number of access apertures  46  and heating/cooling/return air ports  48  through the hood&#39;s walls  18 . In the embodiment shown in the FIGS. a single access aperture and its door  50  is illustrated with a generally rectangular configuration that encompasses a majority of the surface area of one of the side walls of the hood. In this embodiment, the access aperture  46  and its door  50  have intermeshing fasteners  36 ,  37  running around three edges allowing the door  50  to be readily unsealed to gain access into cavity  20  through the enlarged aperture  46 . 
     Similarly, a plurality of air ports or vents  48  is located in various locations around the test chamber  10  providing access into the cavity  20 . These air ports  48  provide various locations for hot or cold air to be pumped into and extracted from cavity  20  by a conventional heat pump/refrigeration unit  52 . Typically, hot and/or cold air is blown into and recovered by at least a pair of conduits  54 ,  55  which allow the test personnel to regulate the temperature within the cavity  20  during a test. Depending on the amount of air needed, various sized (i.e., diameter) conduits may be used for a given test. As shown in  FIGS. 1-3 , the air ports  48  formed in hood  12  are preferably large enough to accommodate a large range of conduits, while providing an adapter sleeve  56  having a tubular body  58  that frictionally receives a particular sized conduit  54 ,  55 . The end of sleeve  56  that is opposite to the conduit-receiving end has a radially outwardly depending flange  60  that has intermeshing fasteners  36  fixed to its hood-abutting face. Complementary fasteners  37  are fixed around each air port  48  to allow the present invention to accommodate various modes of heating and cooling. When an air port  48  is not needed, a panel or cover  62  formed from the same insulating material as the hood  12  and having complementary fastener  36  around its inner face is fastened to the test chamber  10  to maintain a thermal seal. 
     Referring back now to  FIG. 4 , the hood  12  is shown remote from a vibrational test stand or shaker table  64 . The shaker table  64  includes a generally horizontal flat top plate  65 , which is used as the mounting surface for the test fixture  22  that holds the test object  24 . When preparing to conduct a test, the overall size and type of shaker table is determined along with the overall temperature settings to be used. Once a shaker table  64  has been selected for the test, a unique one of a number of differently configured bottom panels  32 , such as panels  32 A or  32 B from  FIGS. 9 and 10  is selected to coincide with the mounting hole arrangement  66 A,  66 B for the selected shaker table. The selected bottom panel, e.g., panel  32 B, is placed upon the top plate  65 , with the corresponding mounting holes  66 B allowing the fixture-mounting hardware  70  to fix the fixture  22  to the shaker table  65  with the insulated panel  32  therebetween. In other non-limiting embodiment, mounting hole arrangement  66  may be eliminated with a generic opening granting direct mounting of the fixture  22  to the top plate  65 . 
     Once the fixture  22  is mounted, the test object(s)  24  and any additional sensors or testing equipment  72  is mounted to the fixture or test stand. Typically, this equipment  72  has cables, cords, and/or tubing  74  which must pass out of the test chamber  10  to conduct the test. 
     The present invention provides an economical benefit of eliminating multiple thermal test chambers as a single hood  12  will envelop a large assortment of shaker tables  64 , therefore once a particular bottom panel  32  is selected, a single collar  34  sized to mate with that hood  12  is sealingly coupled to the bottom panel  32  along  36 A,  37 A. As shown in  FIGS. 7 and 8 , the pliable fabric material of the hood  12  and base  14  of the present invention readily permits the testing personnel to place any cords, cable, and/or tubing  74  between the interconnecting fasteners  36 ,  37 . The cords  74  are then sealing surrounded by the deformable fabric and continuous fasteners  36 ,  37  to substantially eliminate any significant heat loss through the abutting pliable surfaces (e.g., between panel face  38  and the underside of lip  40 ). The continuous fasteners  36 ,  37  allow the set-up personnel to fasten the mating components together up to each end of the protruding cord  74  to maintain the surrounding deformation of the panels. 
     As shown in  FIG. 4 , having the ability to lift a large portion of the testing chamber (i.e., the hood  12 ) up and away from the shaker table  64  during the initial set-up of the test greatly benefits the testing personnel as access to the entire test fixture  22 , test object  24  and additional test equipment  72  is unhindered and thereby allows for more accurate set-ups and tests. 
     Lastly, the hood  12  is lowered over the set-up shaker table  64 , the four side walls  18  are sealing mated to the raised annular ring  44  of the collar  34  and the heating/cooling conduits  54 ,  55  can then be affixed through the various air ports  48  and adapters  56 . 
     From the foregoing description, one skilled in the art will readily recognize that the present invention is directed to a modular thermal test chamber, which provides unhindered access to the test objects and fixtures during set-up and which can be readily adjusted for various sized or configured vibration tables. While the present invention has been described with particular reference to various preferred embodiments, one skilled in the art will recognize from the foregoing discussion and accompanying drawings that changes, modifications, and variations can be made in the present invention without departing from the spirit and scope thereof as is more fully delineated in the following claims.