Abstract:
A scratch testing apparatus for performing a scratching test while gradually increasing or decreasing a load, in which a pressure applied to the surface of a test specimen gradually increases or decreases as a head unit, to which a tip is attached, moves horizontally. The scratching testing apparatus includes a head unit having a bottom to which a tip attached; a guiding unit for guiding the head unit to move horizontally; and a pressure changing unit for changing pressure applied to the tip while the head unit is moving along the guiding unit. Therefore, the scratch testing apparatus may perform a scratching test as gradually increasing or gradually decreasing a load applied to the test specimen by the tip by moving the head unit, to which the tip is attached, horizontally.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS 
       [0001]    This application claims the benefit of Korean Patent Application No. 2009-0013911, filed on Feb. 19, 2009, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a scratch testing apparatus for performing a scratching test while gradually increasing or decreasing a load. and more particularly, to a scratch testing apparatus, in which load applied using a tip gradually increases or decreases as a tester head, to which the tip is attached, moves horizontally, so that scratching operation may be performed as changing a load applied to a test specimen. 
         [0004]    2. Description of the Related Art 
         [0005]    A tape testing method, a bending test, a press-fitting testing method and a scratching testing method are included as examples of testing methods generally used for testing adhesiveness between an object material and a thin film of coating or paint performed to maintain and reinforce characteristics of the object material. A tape testing method is to determine whether coating or paint comes off or not when a tape (an adhesive tape) is attached on and then detached from a surface of an object material. The bending test is the method of measuring a bending load at which a coating or paint comes off. A press-fitting testing method is to determine adhesiveness of a coating or paint through inspecting a crack and an indentation existed on a coated or painted surface after an object material is press-fitted. Finally, a scratching testing is a method of determining the critical load based on scratches formed by scratching a coated or painted surface. 
         [0006]    Here, the scratching testing method is convenient and provides quantized measurement. Therefore, the scratching testing method is the most widely used in industries. 
         [0007]    During a scratching test, adhesiveness between materials is determined based on color shifting of a coating, paint, or a thin film or a change of plasticity which appears on the surfaces of the materials. 
         [0008]    A method of applying a predetermined load on a surface and scratching the surface is used to determine the adhesiveness. However, a number of tests should be performed and a lot of test specimens are needed in order to determine a critical load. 
         [0009]    Therefore, scratching testing method, in which a load applied to a test specimen changes as a tip moves from a beginning point to a ending point of the scratching, is standardized and disclosed in ASTM D7027, ISO 1518, and ISO 12137-2. 
         [0010]    According to the method above, a load at the time of generating a deformation by a scratch on a surface is detected, and thus adhesiveness between the surface and the material and a property of the material are determined by measuring the load. 
         [0011]    According to the ASTM D7027 standards, the critical load shall be determined by gradually increasing a load from 2N to 50N with respect to a displacement of 100 mm at a rate of 100 mm/s and observing whitening phenomenon of the material. 
         [0012]    Furthermore, according to ISO 1518 and ISO 12137-2 standards, a scratching test shall be performed by forming a scratch at a rate of 200 mm/s to determine the critical load of scratching paint or a coated plastic. 
         [0013]    However, since the scratching method shall be performed at a relatively fast rate, it is difficult to control the load and displacement of a testing apparatus, and it is difficult to synchronize the beginning of movements, transportations, and the stopping of movements along the vertical axis and the horizontal axis. 
       SUMMARY OF THE INVENTION 
       [0014]    To solve the above and/or other problems, the present invention provides a scratch testing apparatus for performing a scratching test while gradually increasing or decreasing a load. 
         [0015]    According to an aspect of the present invention, there is provided scratching testing apparatus including a head unit, wherein a tip is attached to the bottom of the head unit; a guiding means  22  for guiding the head unit  10  to move horizontally; and a pressure changing means for changing pressure applied to the tip while the head unit moves along a guiding means, and the pressure changing means including an inclined rail slantingly installed above the head unit and a spring unit installed in the head unit. 
         [0016]    Furthermore, a unit to be pushed is installed below the inclined rail, and a vertical position adjusting unit is formed on the bottom of the unit to be pushed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which: 
           [0018]      FIG. 1  is a view of a head unit of the scratching testing apparatus according to the present invention; 
           [0019]      FIG. 2  is a view of the scratching testing apparatus according to the present invention; and 
           [0020]      FIG. 3  is a view of operations of the scratch testing apparatus according to the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0021]    Hereinafter, the scratch testing apparatus according to the present invention will be described in detail by explaining exemplary embodiments of the invention with reference to the attached drawings. The same reference numerals in the drawings denote the same or similar elements. 
         [0022]      FIG. 1  is a diagram showing a head unit  10  of the scratch testing apparatus according to the present invention.  FIG. 2  is a diagram showing the scratch testing apparatus according to the present invention.  FIG. 3  is a diagram showing operations of the scratch testing apparatus according to the present invention. 
         [0023]    In the scratch testing apparatus to the present invention, a unit to be pushed, which is vertically pushed and is moved downward when its top is depressed, is formed in the head unit  10 , which moves horizontally, as shown in  FIG. 1 . 
         [0024]    The unit to be pushed is a bearing unit  16 , which has a shape for minimizing friction while being moved, and thus friction between the bearing unit  16  and a surface may be minimized. 
         [0025]    Although the bearing unit  16  is introduced as an example of the unit to be pushed, the present invention is not limited thereto, and the unit to be pushed may be formed of a sliding member or a vertical rod. In other words, as long as friction may be minimized by the unit to be pushed at surfaces contacting each other, any of various members may be used as the unit to be pushed. 
         [0026]    A spring unit  13 , which works in linkage with the bearing unit  16 , is formed below the unit to be pushed, that is, the bearing unit  16 . 
         [0027]    The bearing unit  16 , which is above the spring unit  13 , presses the spring unit  13  downward by a height in which the bearing unit  16  is pushed. 
         [0028]    At this time, the spring unit  13  vertically pressed by the bearing unit  16  is formed to press a tip unit  12 , which is connected to the spring unit  13  to work in linkage with the spring unit  13 , vertically downward. 
         [0029]    A damper is attached on top of the spring unit  13  to prevent vibration or the like when the spring unit  13  is displaced in horizontal direction while being vertically pressed by the bearing unit  16 . 
         [0030]    As the bearing unit  16  of the head unit  10  is pressed and presses the spring unit  13  downward, elastic reaction force generated by the spring unit  13  is applied to the tip unit  12 , and thus the tip unit  12  applies a vertical load to a test specimen  40 , which is disposed on a test bed  21  formed below a body  20 . 
         [0031]    Although not shown, the spring unit  13 , which applies elastic load to press the tip unit  12  of the head unit  10  downward, may be easily replaced with various types of springs having different spring coefficients, and thus a starting load and an ending load may be changed as desired. 
         [0032]    The tip unit  12  of the head unit  10 , which works as described above, is installed such that the tip unit  12  is moved horizontally by a motor  11  simultaneously as the tip unit  12  is vertically pressed. 
         [0033]    Furthermore, a vertical load cell  15  for detecting amount of pressure applied by the spring unit  13  is installed on the spring unit  13 , which is attached to the head unit  10 . 
         [0034]    Therefore, a vertical load applied to the tip unit  12  may be detected by using the vertical load cell  15 . 
         [0035]    Furthermore, a horizontal load cell  14  is attached to the motor  11 , and thus, when the tip unit  12  moves on the surface of the test specimen  40 , which is disposed and fixed on the test bed  21 , as scratching the surface of the test specimen  40 , a horizontal load applied in the direction in which the tip unit  12  moves may be detected. 
         [0036]    As shown in  FIG. 2 , the head unit  10  including the tip unit  12 , which works as described above, is installed to move along a ball screw  22 , which is formed between vertical frames  23  on the test bed  21  of the body  20 . 
         [0037]    When the head unit  10  is attached to the ball screw  22  of the body  20 , the head unit  10  is horizontally moved along the ball screw  22  by the motor  11 . 
         [0038]    When the head unit  10  is smoothly slid without vibration by the motor  11  and is moved horizontally along the ball screw  22 , the bearing unit  16  of the head unit  10  is horizontally slid and moved along an inclined rail  30  formed on an upper frame  24  of the body  20 , where the bearing unit  16  continues to contact the bottom surface of the inclined rail  30 . 
         [0039]    In other words, the bearing unit  16  is vertically pressed while being horizontally moved along the inclined rail  30  at a tilt corresponding to the angle of inclination of the inclined rail  30 . 
         [0040]    Accordingly, the bearing unit  16 , which is moved by the motor  11 , moves along the bottom surface of the inclined rail  30 , which is inclined by a predetermined angle with respect to the horizontal direction. 
         [0041]    The spring unit  13  formed below the bearing unit  16  is gradually pressed in a vertical direction as the bearing unit  16  is moved along the inclined rail  30 . 
         [0042]    As shown in  FIG. 3 , due to elastic reaction force of the spring unit  13 , pressure is applied to the tip unit  12  formed below the spring unit  13 . 
         [0043]    When a pressure is applied to the tip unit  12 , load applied to the surface of the test specimen  40  disposed on the test bed  21  increases, and thus the surface of the test specimen  40  is scratched. 
         [0044]    Therefore, pressure applied by the tip unit  12  of the head unit  10  gradually increases (as the bearing unit  16  moves from an end of the inclined rail  30  to the opposite end of the inclined rail  30 ), and thus the surface of the test specimen  40  is scratched. In other words, the scratching testing method according to the present invention begins when the inclined rail  30  is installed on the upper frame  24  such as to be inclined downward as going toward the right side of  FIGS. 2 and 3  as shown in  FIGS. 2 and 3 . Therefore, as the head unit  10  moves horizontally, the vertical position of the head unit  10  is lowered, and thus the spring unit  13  is further compressed. 
         [0045]    Pressure applied to the tip unit  12  as the inclined rail  30  is slantingly installed as described above is transmitted to the tip unit  12  as elastic reaction force of the spring unit  13 , and thus the head unit  10  moves horizontally while press-fitting the test specimen  40 . Therefore, the surface of the test specimen  40  is scratched, and also a vertical load applied to the test specimen  40  increases. 
         [0046]    According to the present invention, the position and the angle of inclination of the inclined rail  30  may be changed, and thus a scratching test may be performed with a desired load applied when the scratching test begins or ends. 
         [0047]    Furthermore, a screw-like vertical position adjusting unit  17  is formed on the bottom of the bearing unit  16 . Therefore, when the vertical position adjusting unit  17  is rotated in a first direction, for example, the bearing unit  16  may rise, and thus the spring unit  13 , which is formed below the bearing unit  16  to work in linkage with the bearing unit  16 , and the tip unit  12 , which is formed below the spring unit  12 , may also rise. 
         [0048]    Furthermore, when the vertical position adjusting unit  17 , which is attached to the bottom of the bearing unit  16  so as to be integrally formed with the bearing unit  16 , is rotated in a second direction, which is opposite to the first direction, the tip unit  12  may be lowered. 
         [0049]    Therefore, since the vertical location of the tip unit  12  may be easily adjusted by using the vertical position adjusting unit  17  as described above, the scratch testing apparatus of the present invention can be properly applied even if the thickness of the test specimen  40  on the test bed  21  is changed. 
         [0050]    While this invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. 
         [0051]    For example, although a case in which a vertical load applied to the test specimen  40  by the tip unit  12  increases as the head unit  10  moves horizontally is described in the above embodiment, a case where a load applied by the tip unit  12  gradually decreases as the inclined rail  30  is inclined oppositely as compared to the case shown in  FIGS. 2 and 3 , that is, the incline rail  30  is inclined upward as going toward the right side of  FIGS. 2 and 3  may be considered.