Abstract:
A portable testing apparatus for a Brinell test meeting the load time requirements of the ASTM E10 standard. The apparatus incorporates a hydraulic accumulator acting on a cylinder which is connected to an indenter. The accumulator keeps a constant force on the indenter for the period of time of the test despite hydraulic leakage or creep of the indenter into the material that would cause a reduction in pressure if not for the accumulator. Usually, the test time length is 10 seconds. Pressure is set using springs usually in a settable sequence valve.

Description:
[0001]    This application claims benefit of U.S. Provisional Application Ser. No. 62/118,491, filed Feb. 20, 2015, pursuant to 35 USC §119(e). 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates to hardness testing equipment, in particular, portable testing equipment for a Brinell test meeting ASTM E10 standard. 
       BACKGROUND OF THE INVENTION 
       [0003]    The Brinell scale characterizes the indentation hardness of materials through a scale of penetration of an indenter loaded on a material test-piece. According to the American Society of Testing and Materials (ASTM) E10 Standard, the Brinell test requires the application to an indenter of 10 mm in diameter of a determined test force (load), usually 500 Kgf for Aluminum and 3000 Kgf for Steel, for a specified amount of time, 10 to 15 seconds. 
         [0004]    Current portable Brinell Testers as disclosed in U.S. Patent Application Publication No. 2014/0230529, published Aug. 21, 2014, which is based on its predecessor U.S. Pat. No. 3,129,582, employs a hydraulic cylinder activated by a hand pump with a release valve when a certain pressure is reached; therefore, a certain resulting load is achieved. The problem with this approach is that the load is only applied instantaneously and it does not remain applied for the specified time. Therefore, the test does not meet the ASTM E10 specification but an ad-hoc specification; that is, E110 created just for this instrument. 
         [0005]    Some users can test according to this specification but the majority must meet the full E10 specification. Thus, there is not found in the prior art a portable Brinell testing 
       SUMMARY OF THE INVENTION 
       [0006]    It is an aspect of the invention to provide a portable hydraulic Brinell testing apparatus that meets ASTM E10 standard. 
         [0007]    It is an aspect of the invention to provide a portable hydraulic Brinell testing apparatus that features an accumulator that keeps the pressure constant during the test period despite creep from the indenter moving in the test piece and hydraulic leakage. 
         [0008]    It is still another aspect of the invention to provide a portable hydraulic Brinell testing apparatus that can be made costing substantively the same as prior art portable Brinell testing apparatus. 
         [0009]    Finally, it is an aspect of the invention to provide a portable hydraulic Brinell testing apparatus that can be made from readily available components or incorporated in a self-contained module. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a schematic of the portable hydraulic Brinell hardness testing apparatus in accordance with the invention. 
           [0011]      FIG. 2  is a schematic of the hydraulic system of the portable hydraulic Brinell testing apparatus in accordance with the invention showing the invention at rest. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0012]    Referring now to  FIGS. 1 and 2 , portable instrument  10  described herein solves the problem of prior art portable systems meeting ASTM E10 standards. This is accomplished by incorporating hydraulic accumulator  30  acting on single spring return cylinder  36  (such as made by ENERPAC of Columbus, Wis., Model RSM-50) through precision sequence valve  42  (such as made by SUN HYDRAULICS of Sarasota, Fla., Model RSFCLAN). 
         [0013]    Hydraulic accumulator  30  is preferably a miniature accumulator (such as made by HAWE HYDRAULIC of Charlotte, N.C., Model Type AC 0725/1A). Accumulator  30  helps compensate for the loss of force due to indenter  14  creep and hydraulic leakage. 
         [0014]    As shown in  FIG. 1 , invention  10  is activated by handle  47  which controls hydraulic pump  46  (made by HAWE HYDRAUKICS, Model HE13 A-K0.5 100). Pump  46  is preferably a double acting pump instead of a single acting pump in order to constantly maintain hydraulic pressure and therefore, provides constant force to indenter  14 . 
         [0015]    Invention  10  uses accumulator  30  to maintain the test force (load) and sustains that force for the required time for test, usually at least  10  seconds. The output of sequence valve  42  is fed to both the top of cylinder  36  and to holding accumulator  30 . The bottom of cylinder  36  is connected to the indenter holder  22 . 
         [0016]    The prior art devices use a simple spring poppet in order to minimize loss of hydraulic pressure and thus, force, but it is not as efficient as sequence valve  42 . Cylinder  36  that applies the load can be directly in line with indenter  14  or acting on an advantage beam/lever (not shown) having a leverage of 5 to 1 or 10 to 1; thus, lowering the pressure and load required in the hydraulics but requiring more fluid flow. 
         [0017]    In operation, invention  10  works as follow: 
         [0018]    Test piece  12  is placed onto anvil  13  of tester  10  specifically on elevating screw assembly  18  which is a jack screw well known in the art. Test piece  12  is raised until test piece  12  contacts indenter  14  and closes the gap between indenter holder  22  and a loading beam (not shown) or directly onto cylinder  36 . 
         [0019]    At this point, the pressure is allowed to build up in the system by shifting the loading/unloading valve  50  which is a two position selector valve (such as made by BRAND HYDRAULICS of Omaha, Nebr., Model DSO8BK) from the rest position (shown in  FIG. 2  with the arrows crissed-crossed) to the testing position (not shown, arrows straight across). This connects accumulator  30  (previously going to blocked port  71 ) from port  72  to port  76  through valve  34  to the top of cylinder  36 . At the same time, port  74  (previously connecting cylinder  36  through port  77  to tank  48 ) is blocked and the top of cylinder  36  through port  77  now goes to blocked port  73  so allowing pressure to build into cylinder  36 . 
         [0020]    Pump  46  is activated to provide the proper pressure until pressure gauge  16  (made by ENERPAC, Model GP-10S) reaches the predetermined value. 
         [0021]    At that point, pump  46  can be stopped. Sequence valve  42  allows downstream flow only. The amount of pressure is set by internal spring of sequence valve  42  with any excess pressure being diverted to tank  48 . Pressure in sequence valve  42  could also be set by a stack of belleville springs that provide a flatter spring rate profile as compared to regular coiled springs therefore assuring smoother transition from dose to open to dose. Still another option is the use of two nested concentric springs, the outer one providing the majority of the force needed, while the inner one permits fine adjustment of the relief pressure. 
         [0022]    The same pressure is fed to holding accumulator  30 , therefore accumulator  30  has enough pressure to compensate for the minimal drop in pressure caused by the creep of indenter  14  into the material during the holding time of the test. After the specified time (min 10 sec.) the loading/unloading valve  50  is returned to the rest position, blocking the pressure from the holding accumulator  30  and, by connecting the cylinder  36  to tank  48  allowing the spring in cylinder  36  to retract indenter  14  so that test piece  12  can be removed. 
         [0023]    Check valve  40  allows flow from sequence valve  42  and prevents backpressure into it; check valve  32  allows flow into accumulator  30  and prevents back flow in that part of the circuit; check valve  34  allows flow from accumulator  30  to cylinder  36  and prevents back flow in that part of the circuit. Note that all check valves are the same (such as made by HAWE HYDRAULICS, Model RK0/RB0). 
         [0024]    The force can be calibrated by adjusting the spring in precision sequence valve  42 . This calibration only has to be done at the time of manufacture. Verification or re-calibration is necessary periodically, such as every 12 months or so. 
         [0025]    With the addition of a button load cell or pressure transducer (such as made by Forsentek of Shenzhen, China, Model No. FC50 (5000 Kg capacity)) in combination with a sensor Load Cell Amplifier Model LAU 63.1 (such as made by Sensor Techniques of Cowbridge, UK) connected to readout display  20  (such as provided by SENECA DISPLAY of Padova, Italy, Model S311AK) and powered by a battery pack (such as Model No. CU-J970 made by AA PORTABLE POWER PAC of Richmond, Calif.), a user can then read the actual load being applied. 
         [0026]    The use of hydraulic hand-operated pump  46  can be replaced or augmented by a 12 V electric pump (not shown) as another way to generate the pressure in addition to or instead of hand pump  46 . This electric pump is preferably of the type made by Bucher Hydraulics of Klettgau-Griessen, Germany, Model C117PE/V0-R106-E56-AP05/** S819. This electric pump would be powered by a battery pack well known in the art. 
         [0027]    While this invention has been described for use with a portable system, the invention could also be used with a bench Brinell tester that is firmly fixed in a location. 
         [0028]    Although the present invention has been described with reference to certain preferred embodiments thereof, other versions are readily apparent to those of ordinary skill in the preferred embodiments contained herein.