Abstract:
A crack test includes flowing pressurized fluid to a generally tubular part in a flare stamping process. As the flare is completed the part is sealed on opposite ends and pressurization of the inside of the part is used to determine integrity of the part.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates generally to stamped parts and components and, more particularly, the invention pertains to test systems and procedures for identifying cylindrical parts with cracks therein.  
       BACKGROUND OF THE INVENTION  
       [0002]     Stampings and progressive stampings are used to manufacture parts and pieces of many different types and shapes for use in a variety of different assemblies and constructions. Metal can be shaped into many different forms and configurations by the application of force causing a metal blank to conform to the shape of a die used while applying the force. Simple parts and pieces can be made by a single stamping. In a single stamping, force is applied in a single event so that the metal conforms to a die used while applying the force. For more complex parts or parts taking a shape quite different from the original metal blank, progressive stampings are used. In progressive stampings, a series of dies are used in a series of stamping events, with each die and each stamping event forming the metal in stages from the original blank to the desired final formation.  
         [0003]     It is known to use stamping techniques to form ends on parts having cylindrical bodies, including the formation of an expanded area or flare at an end of the cylindrical body. For example, a substantially cylindrical or tubular part can be stamped to have an outwardly bulged or flared portion at one end thereof. The initial flaring process can be a precursor, or preliminary step to a subsequent operation. By way of example, it is known to flare a tube end and then compress the flared portion in a folding manner onto itself to produce a two layer thick foot or flange at the end of tube. Parts as described can be used as a compression limiters or load-bearing parts for other purposes.  
         [0004]     Elongated tubular parts can be susceptible to cracking during stamping processes. Force applied against hollow, elongated parts such as tubes or the like when forming flanges or flares is substantially axial, and can cause cracks to form along relatively unsupported lengths during the stamping process. It is often difficult to identify such crack defects. Cameras and visual inspections are often inadequate. Even a hairline crack can be significant in detrimentally affecting the final strength of the part. Compression limiters and the like can fail if a small crack in the barrel thereof is allowed to propagate, thereby weakening the axial strength of the finished part.  
         [0005]     Stamping is often selected as the process for making parts and pieces because a stamping event is a rapid occurrence, and the manufacturing process is quick and inexpensive, with minimal waste. To ensure a high percentage of quality parts are shipped to customers cost effectively, testing procedures for stamped parts should be performed both rapidly and reliably. Preferably, a testing method occurs quickly so that testing or inspection of the part does not slow the overall process of making the part.  
         [0006]     What is needed in the art is a crack testing apparatus that quickly and accurately identifies cracked parts such as a crack along the extended barrel of an elongated part that is hollow in the form of a tube, pipe or the like.  
       SUMMARY OF THE INVENTION  
       [0007]     The present invention provides a testing device incorporated directly with a stamping press for identifying cracked parts or components during other steps in a stamping process.  
         [0008]     In one aspect thereof, the present invention provides a process to identify cracks in a hollow part during a stamping procedure The process includes steps of loading a pre-form of the part into a press; pressing the pre-form of the part to form the part; sealing openings in the part; pressurizing the part in the press; and evaluating the pressure retained in the part.  
         [0009]     In another aspect thereof, the present invention provides a stamping press with a flare pin and a die configured for receiving a first tube end and modifying a shape of the first tube end. A punch chuck assembly is configured for engaging an opposite tube end and urging the tube first end over the pin and into the die. A fluid pressure system includes a source of pressurized fluid and a fluid path through the punch chuck assembly and into a tube held by and between the pin and the die on one end and the chuck assembly on an opposite end.  
         [0010]     In a still further aspect thereof, the present invention provides a stamping process for forming a flared end on a tube and for checking for cracks in the tube. The process has steps of providing a punch chuck assembly having a probe; providing a die block assembly with a flare pin and a die; positioning one end of a generally tubular part over the flare pin and into the die; positioning an opposite end of the generally tubular part over the probe; urging the part into the die block assembly to conform a profile of the tube to the flare die and pin and thereby forming a flared end; pressurizing the inside of the tube while retaining the tube between the die block assembly and the punch chuck assembly; and rejecting the part if a pressure inside the part is below a pre-established minimum pressure.  
         [0011]     An advantage of the present invention is providing a device that can identify cracked components so that the cracked component can be discarded.  
         [0012]     Another advantage of the present invention is providing a device for identifying cracked components in which crack defects appear along the extended lengths of hollow components such as tubes, pipes or the like.  
         [0013]     Still another advantage of the present invention is providing a cracked component identifying system incorporated directly with a press performing a stamping process, so that a flawed part can be identified immediately and quickly.  
         [0014]     Still another advantage of the present invention is providing a crack detecting system for tubes that operates in conjunction with a press, such as a flaring press, for performing other functions so that no additional time is required for testing the tubular body and the manufacturing process is not adversely impacted.  
         [0015]     Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims and drawings in which like numerals are used to designate like features. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]      FIG. 1  is a cross-sectional view of a press having a crack detection system in accordance with the present invention, the press being illustrated in readiness to perform a stamping operation and conduct a crack test;  
         [0017]      FIG. 2  is a cross-sectional view of the press and part shown in  FIG. 2 , illustrating testing of an acceptable part;  
         [0018]      FIG. 3  is a cross-sectional view similar to that of  FIG. 2 , but illustrating testing on a defective part; and  
         [0019]      FIG. 4  is an exploded, cross-sectional view of a portion of the press shown in the preceding drawings. 
     
    
       [0020]     Before the embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is understood that the phraseology and terminology used herein are for the purpose of description and should not be regarded as limiting. The use herein of “including”, “comprising” and variations thereof is meant to encompass the items listed thereafter and equivalents thereof, as well as additional items and equivalents thereof.  
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0021]     Referring now more specifically to the drawings and to  FIG. 1  in particular, a punch press assembly  10  is shown. Punch press assembly  10  includes a crack test system  12  in accordance with the present invention which works in conjunction with a die block assembly  14  and a punch chuck assembly  16  and of press assembly  10 . Punch press assembly  10  in the exemplary embodiment is shown as a flaring press for forming a flare on the end of a pre-formed part  18  to complete a finished part  20  having a flare  22  on the end thereof ( FIG. 2 ). It should be understood that the configuration of pre-formed part  18  and finished part  20  are exemplary in nature and should not be considered as limiting of the present invention. The concepts of the present invention can be used to form other types of parts, different from those shown in the example.  
         [0022]     While  FIG. 1  is shown and described to have pre-form part  18 , and  FIG. 20  is shown and described to have completed part  20 , it should be understood that in referencing a part as being a “completed part” it is intended to mean only with respect to the stamping step shown. It is not intended to mean that no further formation or alterations are made to further configure the part. While the present invention can be used and the test performed on a fully completed part, the present invention also can be used at an intermediate stage of a progressive stamping so that defective parts can be immediately identified and removed from further process steps. Alternatively, defective parts identified utilizing the present invention can be flagged for later removal at a more convenient time and stage of the process overall.  
         [0023]     Die block assembly  14  includes a die block  30  configured for holding and securing a flare die  32  and a flare pin  34  therein. Flare pin  34  includes a contoured distal end  36  for receiving pre-form part  18  thereon. Specifically, a first end  38  of pre-form part  18  is engaged over distal end  36  of flare pin  34  in flare die  32 . Relative axial movement between pre-form part  18  and die block assembly  14  causes first end portion  38  of pre-form part  18  to conform to the configurations of flare die  32  and distal end  36 . Accordingly, the relative axial movement causes first end  38  to be shaped into flare  22  illustrated in  FIG. 2 .  
         [0024]     Punch chuck assembly  16  is provided for engaging pre-form part  18  and exerting force, causing the relative axial movement between pre-form part  18  and die block assembly  14 , with die block assembly  14  generally being kept in fixed position. Thus, punch chuck assembly  16  is adapted and arranged to engage an opposite end  40  of pre-form part  18  that is opposite to first end portion  38 , and to force pre-form part  18  into die block assembly  14 .  
         [0025]     Punch chuck assembly  16  includes a punch or probe  50  adapted to slide into pre-form part  18  through end opposite  40 . A longitudinal opening  52  is provided through probe  50 . A backup  54  is provided and includes a longitudinal opening  56  therein similar to opening  52 . Backup  54  and probe  50  are held in a quill  58  such that longitudinal openings  52  and  56  are in substantial axial alignment allowing fluid flow therethrough.  
         [0026]     Quill  58  is retained in a thimble  60  held on a punch chuck  62 . Those skilled in the art will understand readily that punch chuck  62  is adapted for axial movement toward and away from die block assembly  14  for routine operation of press assembly  10 .  
         [0027]     Crack test system  12  includes a pressurized fluid source  70  from which pressurized fluid is supplied. Pressurized air is a suitable fluid for many operations and uses of the present invention; however, other fluids can be used as desired. Pressurized fluid source  70  is connected to punch chuck assembly  16  by a fluid conduit  72  through which pressurized fluid is supplied to backup  14  and specifically longitudinal opening  56  thereof. Thus, a supply of pressurized fluid is provided to longitudinal opening  56  and longitudinal opening  52  in punch probe  50 .  
         [0028]     A fluid pressure gauge  74  is provided for evaluating the pressure of fluid in conduit  72  and is connected to a controller  76  via a signal line  78 . Controller  76  is configured to provide a suitable notification or response, depending on the pressure determined.  
         [0029]     In the use of the present invention, pre-form part  18  is positioned on probe  50  and is urged over distal end  36  and into flare die  32 . While this known flaring sequence and operation is being performed, in accordance with the present invention pressurized air flows from source  70  through conduit  72  and longitudinal openings  56  and  54 . Air thereby enters pre-form part  18 , and, during initial stages of the flaring operation, the air flows freely through and out of pre-form part  18 . However, as the flaring operation nears completion, with pre-form part  18  being pressed into flare die  32  and over flare pin  34 , a seal is formed retarding the outflow of pressurized air at first end  38 . Similarly, a seal is formed at a confronting interface  80  between opposite end  40  and quill  58 . Accordingly, the flow of air out of finished part  20  is retarded and pressure builds therein. As the pressure builds throughout finished part  20  and crack test system  12 , pressure gauge  74  determines the level to which pressure builds. Controller  76  can be preprogrammed with a threshold pressure indicating proper formation of finished part  20 , without cracks or defects allowing the escape of pressurized fluid. When the threshold pressure is reached, finished part  20  is considered to be an acceptable part and is transferred for further processing along the production line.  
         [0030]      FIG. 3  illustrates a finished part  90  having a crack  92  therein. Crack  92  or malformations of a flare end  94  or opposite end  96  allow continued outflow of air from part  90 . Accordingly, pressure gauge  74  and controller  76  will not determine that the threshold pressure has been reached, and as a result, part  90  will be considered a defective part. In an automated system, punch press assembly  10  can be configured with automatic reject chutes for transfer of the part to scrap processing. Alternatively, an appropriate alarm can be generated, such as a light or other visual signal, or an alarm or other audible signal to alert an operator that a defective part has been identified. Punch press assembly  10  can be disabled so that the operator can remove and dispose of the defective part.  
         [0031]     As yet another alternative, in a computerized control system, the defective part can be flagged and allowed to continue along the processing stream. At some later point in the process the defective part can be removed.  
         [0032]     While the invention has been described to provide substantially continuous flow of pressurized fluid through pre-form part  18  as finished part  20  is being generated, it should be understood that the flow of pressurized fluid need not be continuous. An intermittent flow of fluid can be used, with fluid flow commencing as the stamping process forming flare  22  is being completed.  
         [0033]     Crack test system  12  works in conjunction with and essentially simultaneously as press  10  operates to form flared end  22  on finished part  20 . Consequently, no additional time is required to perform the crack test in that the test occurs simultaneously with formation of flared end  22 . No additional steps are required in the manufacturing process for performing testing, with the testing instead being performed at a station already present for forming the flared end. The test is simple, automatic and effective.  
         [0034]     Variations and modifications of the foregoing are within the scope of the present invention. It is understood that the invention disclosed and defined herein extends to all alternative combinations of two or more of the individual features mentioned or evident from the text and/or drawings. All of these different combinations constitute various alternative aspects of the present invention. The embodiments described herein explain the best modes known for practicing the invention and will enable others skilled in the art to utilize the invention. The claims are to be construed to include alternative embodiments to the extent permitted by the prior art.  
         [0035]     Various features of the invention are set forth in the following claims.