Abstract:
A seal testing apparatus includes a clamp assembly which receives, secures and rotates a piston and seal assembly, a mandrel which extends into the seal assembly and supports a guide which carries a spring biased sensing probe or tooth which is oriented along the axis of the mandrel. In another embodiment, the components are the similar except that the probe or tooth is disposed in the mandrel and extends circumferentially. In both embodiments, data from an optical, laser or acoustic sensor is analyzed to determine the integrity of the piston seal. Yet another embodiment includes an arbor which rotates the seal and an adjacent contra-rotating cylinder having a conical mirror. As the seal, arbor and cylinder rotate, light reflected off the mirror and the seal, and returned to the mirror and a sensor provide data which is again analyzed to determine the integrity of the piston seal.

Description:
FIELD 
       [0001]    The present disclosure relates to testing piston seals and more particularly to a method and apparatus for testing the integrity of elastomeric seals for pistons utilized in, for example, motor vehicle transmissions. 
       BACKGROUND 
       [0002]    The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art. 
         [0003]    Hydraulic transducers, that is, devices that are powered by pressurized hydraulic fluid and convert such energy to linear translation and force are common components of many power transmission and control devices. Hydraulic actuators or operators, as they are commonly called, find wide application of motor vehicle automatic transmissions and dual clutch transmissions (DCT&#39;s). The operability and service life of such actuators is related almost exclusively to the integrity of the elastomeric seal disposed between the translating component, the piston, and the stationary component, the housing. If the seal is defective, either upon assembly or later becomes so, the actuator will, at a minimum, leak and thus require more time to operate, may not be capable of achieving full design force and waste pressurized hydraulic fluid which could adversely impact operation of other components or the entire transmission. In a worst case scenario, the leak is so severe that the actuator simply does not respond to pressure inputs and fails to properly translate the associated, clutch, brake, shift fork or other component. 
         [0004]    Viewed from a chronological perspective rather than from the degree of failure, it is one type of difficulty to have the seal fail after years of service and tens of thousands of miles of travel and another to have the seal fail essentially upon installation because of a manufacturing defect. It is therefore apparent that by inspecting each piston seal the latter type of failure can be virtually eliminated. The present invention is thus directed to a method and apparatus of inspecting piston seals, detecting flaws in such seals and accepting flawless piston seals and rejecting flawed piston seals. 
       SUMMARY 
       [0005]    The present invention provides an apparatus for inspecting a hydraulic piston seal and detecting flaws or defects which could compromise the service life of the piston seal or interfere with proper operation of the piston and associated components. In a first embodiment, the apparatus includes a clamp assembly which receives, secures and rotates a piston and seal assembly, a mandrel which extends into the seal assembly and supports a guide which carries a spring biased sensing probe or tooth which is oriented along the axis of the mandrel. In a second embodiment, the components are the same except that the probe or tooth is disposed in the mandrel and is oriented circumferentially. In both embodiments, the sensing probe may include a light and data from an optical, laser or acoustic sensor is analyzed to determine the integrity of the piston seal. A third embodiment includes an arbor which rotates the seal and an adjacent contra-rotating cylinder having a conical mirror located therein. As the seal, arbor and cylinder rotate, light reflected off the mirror and the seal, and returned to the mirror and a sensor provide data which is again analyzed to determine the integrity of the piston seal. 
         [0006]    Thus it is an aspect of the present invention to provide an apparatus for determining the integrity of a piston seal. 
         [0007]    It is a further aspect of the present invention to provide an apparatus for determining the integrity of a piston seal having a sensing probe or tooth which scans the circumference of the piston seal. 
         [0008]    It is a further aspect of the present invention to provide an apparatus for determining the integrity of a piston seal having a lighted sensing probe or tooth which scans the circumference of the piston seal. 
         [0009]    It is a further aspect of the present invention to provide an apparatus for determining the integrity of a piston seal having an optical, laser or acoustic sensor for detecting flaws in the seal. 
         [0010]    It is a further aspect of the present invention to provide an apparatus for determining the integrity of a piston seal having rotating cylinder having a conical mirror disposed therein. 
         [0011]    Further aspects, advantages and areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
     
    
     
       DRAWINGS 
         [0012]    The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
           [0013]      FIG. 1  is a half sectional view of a typical piston and seal assembly which may undergo testing by the present invention; 
           [0014]      FIG. 2  is a diagrammatic, sectional view of a first embodiment of a piston seal test apparatus according to the present invention; 
           [0015]      FIG. 3  is a perspective view of a second embodiment of a piston seal test apparatus according to the present invention; 
           [0016]      FIG. 4  is a diagrammatic view of a defective piston seal in place on the second embodiment of a piston seal test apparatus according to the present invention; and 
           [0017]      FIG. 5  is a diagrammatic view of another embodiment of a piston seal test apparatus according to the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. 
         [0019]    With reference now to  FIG. 1 , a typical and exemplary piston and seal assembly which may be tested with the present invention is illustrated and generally designated by the reference number  10 . The piston and seal assembly  10  which is circular includes a body portion  12  having a generally “L” shaped cross section. The body portion  12  is preferably fabricated of metal such as aluminum and includes a molded in place gasket or seal  14  of an elastomeric material. The gasket or seal  14  may take various forms but typically includes a first, outer circumferential oblique flange or lip  16  and a second, inner circumferential oblique flange or lip  18 . It will be appreciated that when installed in a cylinder (not illustrated), the outer flange or lip  16  and the inner flange or lip  18  of the piston and seal assembly  10  are displaced slightly more into alignment with the elongate (axially extending) section of the body portion  12 . 
         [0020]    Referring now to  FIG. 2 , a test apparatus for an elastomeric seal  14  such as included in the piston and seal assembly  10  is illustrated and generally designated by the reference number  20 . The test apparatus  20  includes a stationary center fixture or mandrel  22  having an outside diameter smaller than the inside diameter of the piston and seal assembly  10  or similar seal structure to be tested. One wall of the fixture or mandrel  22  defines an axial, semicircular channel  24  which receives a cylindrical rod or guide  26 . The cylindrical rod or guide  26  is coupled to and axially translated by a bi-direction drive mechanism  30  which may include a hydraulic cylinder, a electric motor and cam or a linear actuator, for example. The cylindrical rod or guide  26  defines an axially (vertically) extending aperture  32  through which projects a spring biased, convex sensing finger, probe or tooth  34 . A compression spring  36  which may be a coil spring or a leaf spring disposed behind the sensing probe or tooth  34  may be selected for its spring rate (constant) to provide suitable distorting pressure to a particular inner flange or lip  18  so that tears, non-fills, blisters and other defects of the flange or lip  18  may be detected as will be more fully explained subsequently. 
         [0021]    Surrounding the fixture or mandrel  22  is a rotatable ring assembly  40  that is coupled to and driven by a suitable drive mechanism  42  such as an electric motor and speed reduction unit that rotates the ring  40  through at least 370°, that is, more than a full circle, during each operating (inspection) cycle. The rotatable ring assembly  40  includes one or more clamp members  44  that may be actuated by one or more solenoids or hydraulic pistons  46  to releasably secure a piston and seal assembly  10  to the rotatable ring assembly  40  during the test procedure. 
         [0022]    The test apparatus  20  also includes a machine vision, laser or air nozzle inspection device  50  for tracking and inspecting the inner flange or lip  18  as it is clamped in the rotatable ring and rotated through 370°, as noted above. If a machine vision sensor is utilized as the inspection device  50 , the device  50  will be programmed to recognize discontinuities in the flanges or lips  16  and  18  which could indicate tears or changes in the reflectivity which could indicate blisters or non-fills. Additionally, the sensing probe or tooth  34  may be translucent or transparent and include one or more light sources  52 . The light from the light sources  52  is preferably directed radially outwardly to improve the imaging and fault detection of the machine vision sensor. If a laser sensor, a reflective component such as a mirror on the opposite side of the flange or lip  16  and  18  from the laser will facilitate the detection of tears. This can be achieved by silvering the face of the sensing probe or tooth  34  or fabricating it of metal which is highly polished. 
         [0023]    Another option is an air nozzle which is utilized as the inspection device  50  which directs pressurized air toward the sensing probe or tooth  34  and an acoustic sensor  54 . As the piston and seal assembly  10  is rotated, the signal from the acoustic sensor  54  will be substantially uniform until a defect is encountered at which time the acoustic footprint (frequency spectrum and loudness) will change. Again, the inspection device  50  can be programmed to recognize faults and reject piston and seal assemblies  10  accordingly. In any case, the scanning of the second, inner flange or lip  18 , fault detection, data storage and accept/reject output signals will be synchronized with the rotation of the piston and seal assembly  10  and the rotatable ring assembly  40  such that the exact location or locations of defects on the inner flange or lip  18  can be specified so that a visual inspection and further analysis of the piston and seal assembly  10  may be readily undertaken, if desired. 
         [0024]      FIG. 3  illustrates a second embodiment of a piston seal test apparatus which is generally designated by the reference number  60 . The second embodiment piston seal test apparatus  60  is similar in most respects to the first embodiment piston seal test apparatus  10  and includes the mandrel  22  and a sliding guide or support  26 ′. In the second embodiment  60 , the guide or support  26 ′ translates radially and, at its outward end, includes a circumferentially (horizontally) extending spring biased sensing finger, probe or tooth  64  having a curved, convex end surface  66 . Again, a compression spring  68  which may be a coil spring or a leaf spring behind the sensing probe or tooth  64  provides a restoring force directed radially outwardly from the guide or support  26 ′ and may be selected for its spring rate (constant) to provide suitable distorting pressure to a particular inner flange or lip  18  so that tears and other defects of the inner flange or lip  18  may be detected. The spring biased sensing finger, probe or tooth  64  may also include one or more light sources  52 , as illustrated in  FIG. 2 . Similarly, the spring biased sensing finger, probe or tooth  64  may be fabricated of polished metal or it may be silvered, as described above with regard to the first embodiment spring biased sensing finger, probe or tooth  34 . 
         [0025]      FIG. 4  is a diagrammatic view of a piston and seal assembly  10  in place on the rotatable ring assembly  40  of the second embodiment test apparatus  60 . In this view, the inner flange or lip  18  of the piston seal assembly  10  has a tear or discontinuity  72 . With either a machine vision or laser inspection device  50 , the tear or discontinuity  72  appears as a light, white or reflective, that is, non-dark, opening in the inner flange or lip  18  and, with suitable calibration and/or algorithms and programming, the inspection device  50  recognizes the tear or discontinuity  72  as a flaw and rejects the piston and seal assembly  10 . When the inspection device  50  is an air nozzle and the acoustic sensor  54  (illustrated in  FIG. 2 ) is utilized, suitable algorithms or audio spectrum look up tables will provide suitable identification of the flaw. It should be appreciated that a similar situation exists with regard to other flaws in the piston and seal assembly  10  such as non-fills, blisters and the like. 
         [0026]      FIG. 5  illustrates yet another embodiment of the piston and seal assembly test apparatus which is illustrated and generally designated by the reference number  80 . The seal assembly test apparatus  80  is specifically designed and intended to detect flaws or faults in the first, outer flange or lip  16 . As such, it operates about and around the periphery of the piston and seal assembly  10 , in contact with the outer flange or lip  16 . The third embodiment of the seal assembly test apparatus  80  includes a rotatable arbor or mandrel  82  which receives the piston and seal assembly  10  under test. The piston and seal assembly  10  is secured to the arbor or mandrel  82  by one or more clamp assemblies  84 . 
         [0027]    Adjacent the arbor or mandrel  82  is a contra-rotating transparent, i.e., clear plastic or glass, rotatable cylinder  90 . The cylinder  90  includes a conical mirror or silvered surface  92  oriented at an angle of 45° to the axis of the cylinder  90  and its axis of rotation. Disposed above the cylinder  90  are both a source of light  94  and a light sensor  96 . Preferably, the light source  94  is a laser, LED or incandescent light and lens to provide a focused and preferably coherent light beam. The light sensor  96  is preferably a laser compatible device, other sensor or a plurality of small, individual sensors capable of providing a high definition signal to associated data storage and computational devices including algorithms and programs which process the data from the light sensor  96  and provide either or both an accept/reject signal and information regarding the location, size and type of defect to assist in its subsequent manual location and provide quality control information. 
         [0028]    The rotatable arbor or mandrel  82  and the cylinder  90  are supported on suitable shafts  86  and  98 . A drive assembly  100  includes mating spur gears  102  and  104  on the respective shafts  86  and  98  and a drive assembly  106  which may include an electric motor and a speed reduction unit and which directly drives one of the spur gears  102  and  104 , for example, the spur gear  102 . The spur gears  102  and  104  are sized so that the peripheral, i.e., circumferential, surface speeds of the outer flange or lip  16  of the piston and seal assembly  10  in place on the arbor or mandrel  82  and the transparent cylinder  90  are equal or nearly so and the use of the two spur gears  102  and  104  ensures that the shafts  86  and  98  rotate in the opposite direction. It will be appreciated, however, that other drive arrangements may be utilized that will provide the necessary relative rotational speeds and contra-rotation. Such surface speed synchronization ensures that the force applied by the transparent cylinder  90  is substantially radially directed against the outer flange or lip  16 . 
         [0029]    The drive assembly  100  also includes a bi-directional linear actuator  112  which separates the arbor or mandrel  82  and the transparent cylinder  90  to facilitate mounting of a piston and seal assembly  10  on the arbor or mandrel  82  and draws them together and provides a biasing force so that, in a manner similar to the deforming force provided by the sensing teeth, probes or fingers  34  and  66 , the transparent cylinder  90  contacts the outer flange or lip  16  of the piston and seal assembly  10  and deforms it to facilitate detection of tears, flaws and other irregularities. 
         [0030]    The description of the invention is merely exemplary in nature and variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.