Abstract:
A test fixture facilitates the laboratory testing of windshield wiper blades for vehicles. The test fixture includes a base frame on which are mounted a number of windshield wiper arms oriented generally parallel for engagement with a stainless steel test surface. Positionally adjustable supports are mounted on the base frame to configure the test surface by varying the curvature of the test surface, as well as the overall length thereof, to permit simulation of a large variety of automotive windshields for test purposes. The test fixture also includes a wiper arm mounting device that can be manipulated to vary the wiper arm load to the wiper blade on the test surface. Adjustments in the spring force exerted on the wiper blade allow variances in the application of a biasing force on the wiper blade in conjunction with changes in the attack angle.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims domestic priority on U.S. Provisional Patent Application Ser. No. 60/638,050, filed on Dec. 21, 2004, the contents of which are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to a device for testing wiper blades for automobiles and, more particularly, to a fixture for aging wiper blades to replicate the real world environment to which wiper blades are exposed. 
     BACKGROUND OF THE INVENTION 
     Wiper blades are a high use item on automobiles and require frequent replacing during the operative life of an automobile primarily due to the aging of the elastomeric material from which the wiper blade is manufactured. Aging of the wiper is a function of the exposure of the wiper blade to the environment and of the external forces exerted on the wiper blade from the mounting arms and the curvature of the windshield glass over which the wiper blade is operated. 
     To develop improved wiper blades and to enhance their overall performance, it is preferable to replicate the real world utilization of the wiper blades in the laboratory, particularly under lab conditions that can accelerate the aging process. Laboratory testing of wiper blades would require a process and a test fixture by which the wiper blades can be subjected to accelerated tests. Historically, such a process and test fixture has not been developed adequately. 
     In order to replicate and improve wiper blade performance, the test fixture must be capable of reproducing the permanent set, stress and aging that the wiper blade is subjected to over time. Furthermore, the structural environment in which the wiper blades are to operate can vary significantly from one type or model of vehicle to the other. Accordingly, the test fixture must have sufficient flexibility to vary the parameters under which wiper blades can be operated. For example, the curvature of the windshield glass varies substantially from vehicle to vehicle. The spring force or load vector urging the wiper blade against the surface of the windshield can also be a significant variable. The attack angle, which is the angle at which the wiper blade is disposed against the windshield, is also a variable. 
     Accordingly, it would be desirable to provide a test fixture that can replicate the real world environment for the testing of wiper blades in a laboratory in which the test fixture will have sufficient flexibility to vary the operative parameters under which the wiper blades can be operable from one vehicle to another and within the same vehicle. 
     SUMMARY OF THE INVENTION 
     It is an object of this invention to overcome the aforementioned disadvantages of the known prior art by providing a fixture for the laboratory testing of wiper blades. 
     It is another object of this invention to provide a test fixture that will incorporate sufficient flexibility to vary the physical environmental parameters under which wiper blades operate in the rear world. 
     It is a feature of this invention that the shape of the test surface over which the wiper blades are to be tested can be varied to reflect the different configurations of vehicle windshields. 
     It is an advantage of this invention that many different windshield configurations can be simulated with the test fixture. 
     It is another feature of this invention that the both the length and the curvature of the test surface can be varied as needed to simulate different vehicle windshields. 
     It is still another feature of this invention that the attack angle of the wiper blade on the test surface can be varied. 
     It is yet another feature of this invention that the spring force exerted by a windshield wiper arm can be selectively varied to change the conditions under which the wiper blades are tested. 
     It is still another advantage of this invention that multiple wiper blade test simulations can be conducted simultaneously to determine the optimum parameters under which different wiper blades should be operated. 
     It is still another feature of this invention that the test fixture accommodates the mounting of different types of wiper blade mounts to provide greater flexibility in the utilization of the laboratory test fixture. 
     It is yet another advantage of this invention that the two differently configured test surfaces can be arranged on each base frame to test driver and passenger windshield glass curvature. 
     It is a further advantage of this invention that the configuration of the test surface can be quickly converted between different configurations simply by positionally adjusting the supports for the test surface. 
     It is a further feature of this invention that the base frame can be equipped with support legs that allow a stacking of multiple test fixtures for simultaneous operation in a compact space. 
     It is a further object of this invention to provide a wiper blade test fixture which is durable in construction, inexpensive of manufacture, carefree of maintenance, facile in assemblage, and simple and effective in use. 
     These and other objects, features and advantages are accomplished according to the instant invention by providing a test fixture for the laboratory testing of windshield wiper blades for vehicles. The test fixture includes a base frame on which are mounted a number of windshield wiper arms oriented generally parallel for engagement with a stainless steel test surface. Positionally adjustable supports are mounted on the base frame to configure the test surface by varying the curvature of the test surface, as well as the overall length thereof, to permit simulation of a large variety of automotive windshields for test purposes. The test fixture also includes a wiper arm mounting device that can be manipulated to vary the wiper arm load to the wiper blade on the test surface. Adjustments in the spring force exerted on the wiper blade allow variances in the application of a biasing force on the wiper blade in conjunction with changes in the attack angle. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The advantages of this invention will become apparent upon consideration of the following detailed disclosure of the invention, especially when taken in conjunction with the accompanying drawings wherein: 
         FIG. 1  is a schematic perspective view of a wiper blade test fixture incorporating the principles of the instant invention, the individual wiper blades being removed from the test fixture for purposes of clarity; 
         FIG. 2  is a partial perspective end view of the head portion of the test fixture shown in  FIG. 1 ; 
         FIG. 3  is a partial side perspective view of the test fixture shown in  FIG. 1  to show the support of the test surface for the adjustable configuration thereof to replicate differently shaped automotive windshields; 
         FIG. 4  is a partial upper perspective view of the end of the test fixture opposite the head portion to depict the support of the test surfaces over which the wiper blades are engaged, the individual wiper blades being removed from the fixture for purposes of clarity; 
         FIG. 5  is a perspective view of a mounting device for a wiper blade located at the head portion of the fixture; 
         FIG. 6  is an enlarged perspective view of the adjustment apparatus of the mounting device to affect a variation in the load vector and of the attack angle of the wiper blade being tested against the test surface; 
         FIG. 7  is an exploded perspective view of the end of the mounting device shown in  FIG. 6 , but with the mounting rod being disassembled from the mounting block of the adjustment apparatus, an alternative embodiment of the mounting rod is shown adjacent the mounting rod depicted in  FIG. 6 ; 
         FIG. 8A  is a cross-sectional view of a representative wiper blade showing the configuration of the wiper blade as the blade is manufactured; 
         FIG. 8B  is a cross-sectional view of the representative wiper blade shown in  FIG. 8A  after undergoing aging, the wiper portion of the blade being deflected into a permanent set relative to the structural body of the blade retained in the mounting apparatus; and 
         FIG. 9  is a schematic perspective view of a pair of stacked test fixtures permitted by the support legs on the frame structure to allow a large sample of wiper blades to be aged simultaneously. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to  FIGS. 1-4 , a test fixture for testing wiper blades under laboratory conditions incorporates the principles of the instant invention. The test fixture  10  includes a frame  11  preferably manufactured from aluminum and formed from a pair of side beams  12  and a pair of end beams  13  with four upright support posts  14  positioned near the four corners of the rectangular frame  11 . The upright support posts  14  are utilized, as is depicted in  FIG. 9  to stack multiple test fixtures; therefore, the upright posts  14  have to be configured to be stackable such as by having the upper ends of the posts  14  sized to fit within the bottom ends of the posts  14 . 
     The rectangular frame  11  is formed with a center support beam  16  that is oriented parallel to the side beams  12  and located midway between the side beams  12  to provide support for the plates  20  that provide a test surface against which the wiper blades will be engaged, as will be described in greater detail below. The frame  11  is also formed with a pair of fixed support bars  17  spanning between the respective side beams  12  and the center support beam  16 . The fixed support bars  17  are located, as is best seen in  FIGS. 1 and 4 , near the end beams  13 , but spaced inwardly somewhat to provide support for the curvature of the plates  20  to be described in greater detail below. 
     Preferably, each test fixture  10  is provided with a pair of flexible plates  20 , preferably formed of stainless steel with a mirror finish on the top surface thereof. One skilled in the art will readily recognize that the number of plates  20  provided on the test fixture  10  could be more or less than two, with appropriate structure changes to the frame  11  as would be required to support the plates  20  in the manner described below. The plates  20  are mounted at opposing ends by a push down bar  22  located near each opposing end beam  13 . The push down bars  22  provide support for the ends of the plate  20  and provide vertical restraint on the respective ends of the plate  20  to permit the plates  20  to be curved as desired. The push down bars  22  have sufficient depth to accommodate the changes in the length of the plates  20  caused by varying the curvature of the plates  20 . 
     The side beams  12  and the center support beam  16  of the frame  11  are formed with a plurality of threaded holes  19  along the length thereof between the respective fixed support bars  17 , preferably eight to ten holes  19 , though only a representative number of the holes  19  are depicted in the drawings, to provide adequate flexibility to form the plates  20  in the curvature desired. A plurality of support members  25  having threaded rods  26 , best seen in  FIGS. 1-4 , are threaded into selected holes  19  along the length of the side beams  12  and center support beam  16 . The support members  25  are arranged in pairs located on opposite transverse sides of the plate  20 . An adjustable cross bar  30  extends between the corresponding pair of opposing support members  25  to support the flexible plate  20  between the support members  25 . The quantity and location of support members  25  and the adjustable cross bars  30  is determined by the desired complexity of the curved formation of the respective flexible plate  20 . 
     Each threaded rod  26  has mounted thereon a pair of bronze nuts  27  with each of the bronze nuts  27  having an enlarged head  28 . The bronze nuts  27  are mounted on the threaded rod  26  in opposing fashion with the bottom bronze nut  27   b  having the head  28  at the bottom of the nut  27  and the top bronze nut  27   a  having the head  28  at the top of the nut  27 , as is best seen in  FIG. 3 . The two bronze nuts  27  are preferably positioned next to each other so that the bottom bronze nut  27   b  will support the adjustable cross bar  30  on the head  28  thereof while the top bronze nut  27   a  secures the plate  20  against the adjustable cross bar  30 . 
     One of ordinary skill in the art will recognize that the height of the bronze nuts  27  on each individual pair of threaded rods  26  is vertically adjustable by threading the nuts  27  along the length of the rod  26 . By properly positioning the bronze nuts  27 , and, therefore, the position of the adjustable cross bars  30 , at each pair of support members  25 , and providing an adequate number of pairs of support members  25 , the precise curvature of the plate  20  can be finely adjusted and tuned to mimic substantially any automotive windshield surface. The plates  20  are trapped between the push down bars  22  at the ends of the plates  20 , on top of the fixed support bars  17 , and between the longitudinally spaced adjustable cross bars  30  with the upper bronze nuts  27   a  securing the plate  20  against the adjustable cross bars  30 . 
     At the head portion  15  of the frame  11 , as best seen in  FIG. 2 , the end beam  13  has a pair of blocks  35  bolted thereto to provide support for adjustable arms  40  that will support the wiper blades  49  against the plates  20 . One of the blocks  35  correspond to each of the plates  20  and incorporate vertically slotted openings  36  for the passage of fasteners  37  connecting the blocks  35  to the end beam  13 . The vertical slots  36  permit a vertical and angular positional adjustment of the block  35  relative to the end beam  13  on which the block  35  is mounted to permit a gross positional adjustment of the wiper blades  49  mounted thereon relative to the corresponding plate  20  against which the wiper blades  49  are engaged. 
     Each adjustable arm  40  is individually bolted to the block  35  and has three adjustment features to provide flexibility in the loading and positioning of the wiper blades  49  mounted thereon with respect to the corresponding plate  20 . Each arm  40  is formed like an automotive wiper arm with an arm head  41  that is bolted to the block  35  and a pivoted arm  42  that is spring-loaded into the extended position seen in  FIG. 5  by the spring  43  housed within the arm  42 . 
     The first adjustment feature of the adjustable arm  40  is a spring force adjustment mechanism  45  mounted at the distal end of the arm  40  and connected to the spring  43 . The spring force adjustment feature includes a threaded cylinder  46  that is connected to the end of the spring  43  and is threaded onto a screw  47  that is supported by a nut  48  mounted on the arm  40 . By rotating the screw  47 , the cylinder  46  is moved along the length of the screw  47  to extend or relax the spring  43  by changing the length thereof. In this manner, the force exerted by the spring  43  to urge the wiper blade  49  against the corresponding plate  20  can be varied. 
     The second adjustment feature of the arm  40  is depicted in  FIGS. 5-7 . A mounting block  50  is affixed to the distal end of the mounting arm  40  and is formed with a bore  52  extending therethrough generally at an angle with the mounting arm  40 . A rod  53  is mounted in a grooved cylinder  55 , best seen in  FIGS. 6 and 7 , which, in turn, is received within the bore  52  through the mounting block  50 . First and second screws  54   a  and  54   b  are threaded into the mounting block  50  to engage the rod  53  within the grooved cylinder  55  and fix the orientation of the rod  53 . 
     The first screw  54   a  fixes rod  53  into the grooved cylinder  55  within the mounting block  50 , while the second screw  54   b  (closest to the distal end of the mounting arm  40 ) controls the orientation of the rod  53  within the cylinder  55 . The attack angle of the wiper blade  49  relative to the plate  20  can be adjusted by loosening the screws  54   a ,  54   b  and rotating the rod  53  within the cylinder  55  to position the wiper portion  49   a  of the wiper blade  49  relative to the plate  20  to an aged angle, such as is depicted in  FIG. 8B , whereupon the screw  54   b  is then tightened to fix the rod  53  in the desired orientation. 
     The third adjustment feature of the mounting arm  40  provides the ability to change the rod  53  for an alternative form of the rod  53   a , such as is depicted in  FIG. 7 . To replace the rod  53 , the screws  54   a ,  54   b  are loosened to permit the rod  53  to slide off the grooved cylinder  55 , whereupon the alternate rod  53   a  is inserted into the grooved cylinder  55  and the first screw  54   a  is tightened first to fix the rod  53   a  in the cylinder  55  and then the rod  53   a  is rotated to the desired aging orientation whereupon the second screw  54   b  is tightened to fix the alternate rod  53   a  within the mounting block  50 . The alternative rod  53   a  could be a rod that has a specific attachment for the aging of the wiper blade. 
     With the wiper blade  49  mounted on the end of the rod  53  and positionally adjusted to the desired orientation of the rod  53  relative to the plate  20 , the loading direction can be varied by adjusting the position of the block  35  on the end beam  13  and by adjusting the spring force exerted on the mounting arm  40  through use of the threaded cylinder  46  mounted on the screw  47 . 
     The plates  20  can be adjusted for curvature by manipulating the vertical positions of the bronze nuts  27  on the threaded rods  26 . Two plates  20  are preferably provided on each fixture frame  11  so that the curvature of the windshield at the passenger side and at the driver&#39;s side can be properly adjusted to conform to the driver&#39;s side wiper blade, as opposed to the passenger side wiper blade which is usually shorter than the driver&#39;s side blade. Multiple wiper blades can be tested on each plate  20  simultaneously. 
     The plates  20  have limitations as to adjustment of the curvature to simulate the windshield glass. The smallest radius at which the plates  20  can be curved without subjecting the plates to permanent deformation is 700 mm. If curvature greater than a 700 mm radius is required, two thinner plates  20  are placed on top of one another to provide adequate flexibility while providing support for the wiper blades. Deformation of the plate with loading from the wiper blades should be less than 0.1 mm. To maintain this tolerance, an appropriate number of threaded rods  26  with bronze nuts  27  supporting the adjustable cross bars  30  and securing the plates  20  will need to be utilized. 
     Accordingly, the flexible fixture  10  described above is capable of replicating the real world environment for the operation of wiper blades for all ranges of production variability in a quick and efficient manner. The fixture  10  is flexible to a large range of wiper blade sizes and is flexible to create a large range of glass curvatures. The fixture  10  is intended to replicate the conditions of the wiper blade when in the park position with the same load bearing and environmental to which the blades are exposed in actual use. 
     The fixtures  10  can be stacked on top of one another, as is depicted in  FIG. 9 , to provide the ability to age a large group of wiper blades  49  at the same time and under the same laboratory conditions. By stacking the fixtures  10 , the entire group of wiper blades  49  can be inserted into a small volume oven for aging purposes. 
     The advantages of this fixture  10  are that the equivalent degradation of field returned wiper blades can be replicated on new wiper blades  49 . The fixture  10  will age and test different designs of wiper blades  49  and rubber material to permit the most robust design to be selected for production. The fixture  10  is also capable of identifying the effect of blade to blade variability using established wipe quality metrics. Furthermore, the flexibility of the fixtures  10  allows the aging and testing of wiper blades across an entire spectrum of vehicles. 
     It will be understood that changes in the details, materials, steps and arrangements of parts which have been described and illustrated to explain the nature of the invention will occur to and may be made by those skilled in the art upon a reading of this disclosure within the principles and scope of the invention. The foregoing description illustrates the preferred embodiment of the invention; however, concepts, as based upon the description, may be employed in other embodiments without departing from the scope of the invention.