Abstract:
A system and process for performing a crimping operation by which a fitting is crimped to the end of a fluid conduit, and which automatically compensates for one or more variables that can lead to out-of-tolerance crimp diameters, particularly fitting spring-back and crimper deflection. The system and method use a device for inputting into the system a targeted crimp diameter for the fitting, and a crimper for crimping the fitting to the end of the fluid conduit. The crimper comprises a plurality of dies and an actuator for contracting the dies around the fitting to obtain the targeted crimp diameter for the fitting. The system and method further includes a unit for attaining the targeted crimp diameter by automatically compensating contraction of the dies for spring-back of the fitting during crimping and/or deflection of the crimper during crimping.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application claims the benefit of U.S. Provisional Application No. 60/705,622, filed Aug. 4, 2005, the contents of which are incorporated herein by reference. 

   BACKGROUND OF THE INVENTION 
   The present invention generally relates to equipment and processes for attaching components together by compressing one of the components around the other. This invention particularly relates to a system and process for crimping a fitting to the end of a conduit to consistently achieve a targeted crimp diameter for the fitting. 
   Crimping processes generally involve a set of tooling, such as a die set, that is forced closed around a fitting loosely assembled onto the end of a conduit, such as a hose or tube adapted to transport a fluid or protect electrical wiring or other hardware susceptible to damage. A representative hydraulic hose and fitting assembly  10  is depicted in  FIG. 1  as including a hose  12  and fitting  14 , with the end  16  of the hose  12  being received and trapped between an inner stem  18  and outer ferrule  20  of the fitting  14 . The crimping action is the result of the die set (not shown), arranged around the circumference of the ferrule  20 , being collapsed in a controlled manner onto the ferrule  20  to apply a crimping force radially inwardly toward the centerline of the hose  12 , as indicated in  FIG. 1 . To meet reliability and manufacturing standards, the die set used to crimp the fitting  14  must sufficiently compress the fitting  14  to lock the fitting  14  onto the hose end  16 . For this purpose, manufacturers typically designate a final crimp diameter “D c ” and allowable tolerance for a given type and size of fitting  14  and hose  12 . 
   Crimping equipment often rely on a hydraulic cylinder to actuate the die set, such that the required crimping force is directly related to the hydraulic pressure within the cylinder.  FIGS. 2 through 4  illustrate three commonly used approaches to the application of pressure during a crimp cycle.  FIG. 2  shows a crimp cycle in which the pressure gradually and nonlinearly increases during the cycle.  FIG. 3  shows an example of the pressure being increased and then held steady to finish the crimp. In  FIG. 4 , the pressure increases but is then allowed to drop toward the end of the cycle. Various other pressure cycles are also possible, and the following discussion is not limited to the pressure cycles represented in  FIGS. 2 through 4 . 
   Typical crimping equipment and dies are designed to accommodate a range of hose and fitting sizes and types. It can be appreciated that the crimping force required to produce a reliable crimp increases as the diameters of the fittings increase. It is also true that heavier hoses and fittings, in other words, those that contain more material that must be compressed during crimping, also require much greater crimping forces than lighter hoses and fittings of the same diameter. This relationship is represented in  FIG. 5 , and can be seen to be nonlinear. 
   Another consideration during crimping is how the hose  12  and fitting  14  respond to a crimp. Due to material being compressed and plastically deformed during crimping, the diameter of the fitting  14  (as measured by the diameter of the ferrule  20  in  FIG. 1 ) naturally expands slightly after a crimp toward its original shape, a phenomenon that will be referred to as fitting spring-back. The amount of spring-back is a significant part of the crimping process that varies from fitting to fitting.  FIG. 6  represents that heavier fittings result is more spring-back than lighter ones, again in a nonlinear relationship. 
   In addition to the above factors, the pressure necessary to attain a required crimp diameter is further complicated by tolerances and variations in manufacturing hoses and fittings. Tolerances may result in different crimping forces/pressures being required to attain a required crimp diameter for a quantity of a particular type of hose/fitting combination. 
   In an effort to more reliably attain a desired crimp diameter, crimpers typically utilize either pressure or position of the hydraulic cylinder to adjust the crimp diameter.  FIG. 7  shows a flow chart for a crimper controlled by pressure. Monitoring pressure is usually only effective for very light and small fittings, especially those manufactured to relative tight tolerances so that the pressure required to achieve a desired crimp diameter is more consistent from crimp to crimp. As the fittings and hoses get bigger, the size variation between fittings tends to increase due to tolerances, with the result that the pressure to achieve a desired crimp diameter can significantly vary from fitting to fitting, for the reasons discussed previously with respect to  FIG. 5 . For crimp cycles that operate with a gradually increasing pressure as represented in  FIG. 2 , monitoring the pressure to control the crimp can generally be reasonably achieved. However, for crimp cycles of the type shown in  FIGS. 3 and 4 , reliable control of the pressure to obtain a desired crimp diameter becomes complicated. As a result, monitoring pressure to control a crimping cycle is very limited and not widely used. 
   In view of the above, positional feedback is more widely used as a method for making crimps. This type of control system is represented in  FIG. 8 . To illustrate the following discussion, reference is made to  FIGS. 9 and 10 , which show a crimper  22  whose die set  24  is in fully open (expanded) and fully closed (contracted) positions, respectively. The die set  24  is shown as being actuated with a piston  26  of a hydraulic cylinder  27 . Typically, the linear travel of the piston  26  can be directly correlated to the diameter D d  of the die set  22  through knowledge of the camming surfaces  32  between the die set  24  and piston  26 . As such, the position of the piston  26  relative to a suitable reference is often monitored with this control method. A limit switch or position transducer (not shown) is typically mounted externally on the crimper  22  to provide feedback of the position of the piston  26 . The limit switch or transducer must be mounted on the crimper  22  away from the hose and fitting (not shown) so that it is not damaged during use of the crimper  22  and does not interfere with the crimping process. For this reason, for crimpers similar to the type shown in  FIGS. 9 and 10 , the position of the piston  26  is usually monitored based on the distance between the piston  26  and the front plate  28  of the crimper  22 . 
   As seen in  FIG. 10 , the front plate  28  tends to deflect during the crimp cycle as a result of the die set  24  being retained in the crimper  22  with the front plate  28 . This deflection affects any position measurements of the piston  26  taken with respect to the front plate  28 . As fittings vary, the required pressure varies, and the deflection in the front plate  28  also varies, with higher pressures resulting in greater deflection as shown in  FIG. 11 .  FIG. 12  shows another relationship that exists between the die set diameter D d  and the deflection of the crimper front plate  28 . From  FIG. 12 , it can be understood that a position reading made during crimping of a fitting that causes only minor deflection will result in a smaller die set diameter D d  than the same position reading for a different fitting whose crimping causes significant deflection. As such, monitoring crimper position generally works well as a control method, but can be inaccurate due to crimper deflection. 
   In view of the above discussion, current crimper technology requires the operator to constantly monitor the crimping process and make adjustments as required. Though a given hose and fitting combination will have unique specifications that require certain crimper settings to achieve a desired crimp diameter D c , the operator must also adjust for variances in individual hoses and fittings attributable to tolerances. Many crimper settings do not provide for any spring-back in a hose and fitting assembly, necessitating that the operator measure each crimped assembly and re-crimp to a smaller diameter if the assembly is out of tolerance. Crimp settings also do not allow for crimper deflection, representing yet another reason for operators to measure each crimped assembly and re-crimp if necessary. Because the crimp diameter will typically be out of tolerance due to a combination of fitting spring-back and crimper deflection, it is not uncommon for some hose/fitting assemblies to require multiple crimps before their crimp diameter falls within an acceptable range. 
   From the above, it can be appreciated that, while crimp operators can identify and fix defective crimps as they occur, it would be desirable if variables that cause defective crimps could be automatically compensated for. 
   BRIEF SUMMARY OF THE INVENTION 
   The present invention provides a system and process for performing a crimping operation by which a fitting is crimped to the end of a fluid conduit, and which automatically compensates for one or more variables that can lead to out-of-tolerance crimp diameters, particularly fitting spring-back and crimper deflection. The invention overcomes many of the problems arising from variances often present in hoses and fittings that affect fitting spring-back and crimper deflection. 
   The system of this invention includes means for inputting into the system a targeted crimp diameter for the fitting, and means for crimping the fitting to the end of the fluid conduit. The crimping means comprises a plurality of dies and an actuating means for contracting the dies around the fitting to obtain the targeted crimp diameter for the fitting. The system further includes means for attaining the targeted crimp diameter by automatically compensating the contraction of the dies for spring-back of the fitting during crimping and/or deflection of the crimping means during crimping. 
   The process of this invention includes inputting into the system a targeted crimp diameter for the fitting around the end of the fluid conduit, crimping the fitting to the end of the fluid conduit with a crimping means comprising a plurality of dies and an actuating means that contracts the dies around the fitting to obtain the targeted crimp diameter and, during the crimping step, attaining the targeted crimp diameter by automatically compensating contraction of the dies for spring-back of the fitting and/or deflection of the crimping means during crimping. 
   A significant advantage of this invention is that the system and process compensate a crimping operation by factoring in the influence that fitting spring-back and crimper deflection have on the die set diameter and pressure, resulting in the elimination or at least significant reduction in the number of crimping cycles needed to identify crimping settings that will achieve a desired crimp diameter. The invention also eliminates or at least significant reduces the need to check crimp diameters of individual hose and fitting assemblies once the proper crimping settings are determined for a given type of hose and fitting assembly. 
   Other objects and advantages of this invention will be better appreciated from the following detailed description. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a fragmentary cross-sectional view of a hose and fitting assembly of a type that can be crimped in accordance with this invention. 
       FIGS. 2 through 4  represent pressure cycles of types typically employed in crimping cycles. 
       FIG. 5  is a graph representing the influence that fitting size has on the pressure required to obtain a desired crimp diameter. 
       FIG. 6  is a graph representing the influence that fitting size has on the amount of fitting spring-back that occurs at the completion of a crimping cycle. 
       FIGS. 7 and 8  are schematics of control methods used to control crimp diameters in accordance with the prior art. 
       FIGS. 9 and 10  illustrate the tendency for deflection to occur within a crimper during a crimping cycle. 
       FIG. 11  is a graph representing the relationship between crimping pressure and crimper deflection. 
       FIG. 12  is a graph representing the influence that crimper deflection has on the die diameter during a crimping cycle. 
       FIG. 13  is a schematic of a control system suitable for use in controlling crimp diameters in accordance with the present invention. 
       FIG. 14  is a graph representing the relationship between travel compensation and crimping pressure used in the control system of  FIG. 13  in accordance with a preferred embodiment of the present invention. 
       FIG. 15  depicts a suitable controller for use with the control system and method of the present invention. 
       FIGS. 16 through 21  represent input windows used to input data to the controller of  FIG. 15  in accordance with a preferred embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The present invention provides a crimping system and method by which more accurate crimp diameters can be achieved for a wide variety of hose and fitting sizes and types. As represented in  FIG. 13 , the system  40  and method employ a compensation algorithm that uses both pressure and position as inputs. The system  40  and method can be used to crimp a variety of hose and fitting types, such as the type represented in  FIG. 1 , and can be used to control a variety of crimpers, including the crimper  22  represented in  FIGS. 9 and 10 . As such, the following description of the invention will be make reference to the hose and fitting assembly  10  of  FIG. 1 , the crimper  22  of  FIGS. 9 and 10 , and their components. However, those skilled in the art will appreciate that the present invention is also applicable to other types of hoses, fittings, and crimper designs, including scissor-type crimpers well known in the art. 
   As with prior art crimpers, the invention makes use of a position sensor ( 30  in  FIG. 13 ), such as a limit switch or position transducer, to sense the position of the die set  24  within the crimper  22 , and therefore the die set diameter D d . For example, the travel of the piston  26  can be used to indicate the die set diameter D d  in view of the linear relationship evident from the camming surfaces  32  of the die set  24  and the piston  26 . Simultaneously, the invention makes use of a pressure sensor ( 34  in  FIG. 13 ) to monitor the force generated by the die set  24 . In the crimper  22  of  FIGS. 9 and 10  in which the die set  24  is actuated by a piston  26  mounted to a hydraulic cylinder  27 , the pressure of the hydraulic fluid used to actuate the cylinder  27  is convenient to monitor for this purpose. The relationships between pressure and fitting spring-back and deflection evident from  FIGS. 5 ,  6 , and  11  also make pressure a convenient input for use in this invention to improve the crimping accuracy. However, it should be understood that other means could be used to measure or otherwise monitor the force generated by the die set  24 . 
     FIG. 13  represents the system  40  as having a controller  36  communicating with an operator interface  38 , the latter of which is used to input crimp diameter D c  and the closed diameter of the die set  24  into the controller  36 .  FIG. 15  represents the interface  38  as being integrated with the controller  36  as a touchscreen  38  by which these inputs and other control and adjustment information can be input into the system  40 , as will be discussed in greater detail below. As represented in  FIG. 13 , the output of the position and pressure sensors  30  and  34  provide the feedback to the controller  36  to perform the compensation algorithm of this invention. 
   As illustrated by  FIG. 5 , the pressure required to achieve a desired crimp diameter D c  is directly related to how heavy the hose and fitting are, in other words, the combined influence of the size, type, materials, and amounts (volume, mass) of the materials that form the hose  12  and fitting  14 . According to the invention, by simultaneously monitoring crimping pressure during a crimping cycle with a preset piston position corresponding to the desired crimp diameter D c , light and heavy hose and fitting combinations can be automatically detected by sensing the crimping pressure as the piston  26  approaches its preset position. From  FIG. 5 , it can be appreciated that as the die set  24  of the crimper  22  approaches the required crimp diameter D c , additional travel may be required depending on the pressure required to achieve the crimp diameter D c . According to the present invention, as the hydraulic pressure sensed by the pressure sensor  34  increases, the controller  36  automatically increases the amount of travel of the piston  26  and therefore compensates for heavier fittings.  FIG. 14  is a graph based on empirical data that evidences a nonlinear relationship exists between sensed fluid pressure and the amount of piston travel compensation required to produce desired crimp diameters for various fitting assemblies. In particular, the empirical data suggests a roughly exponential compensation algorithm that the controller  36  can apply to the travel of the piston  26  based on the fluid pressure sensed by the pressure sensor  34 . As such, the system  40  does not employ the conventional practice of using only piston position to achieve a desired crimp diameter D c . Instead, the system  40  of this invention uses an algorithm that provides compensation relative to increasing pressure by providing an automatic, rapid, and corrective adjustment to piston position as higher pressures associated with heavy fittings are encountered. 
   By compensating for heavier fittings by increasing the travel of the piston  26 , the controller  36  also compensates for spring-back of the hose  12  and fitting  14  at the end of the crimping cycle when the die set  24  is retracted. This phenomenon, previously discussed with reference to  FIG. 6 , is characterized by a relationship between spring-back and the size, type, material, etc., of the fitting  14 , and is similar to the relationship between the crimp pressure and the size, type, material, etc., of the fitting  14  represented by  FIG. 5 . This similarity can be understood from the observation that heavier fittings  14  would tend to spring back more than lighter fittings  14 . On this basis, the invention simultaneously uses pressure to determine how much additional travel of the piston  26  is required to compensate for spring-back. As the crimp pressure increases, the fitting  14  is crimped to a smaller crimp diameter D c . 
   Another desirable result of controlling the crimper  22  based on position of the piston  26  and compensated with pressure is the effect of also compensating for deflection in the crimper  22 , or as discussed with reference to  FIG. 10 , the front plate  28  of the crimper  22 .  FIG. 11  was previously described as showing that as the crimp pressure increases, the deflection in the crimper  22  also increases. By monitoring the pressure to determine the required compensation according to the compensation curve of  FIG. 14 , the die set  24  will close farther and automatically compensate for any deflection in the crimper  22 . 
   A typical operation sequence made possible with the present invention is described in reference to  FIGS. 16 through 20 , which represent input screens generated by the touchscreen  38  of the controller  36  shown in  FIG. 15 . An example of a suitable start screen is represented in  FIG. 16 . Pushing the “START MOTOR” button of the touchscreen  38  brings the operator to the screen shown in  FIG. 17 . As with conventional crimpers, two inputs are required to initiate a crimp cycle: the closed diameter of the die set  24  when fully contracted, and the desired crimp diameter D c . At the screen shown in  FIG. 17 , the operator presses “CRIMP TO DIAMETER,” which brings up the screen shown in  FIG. 18 . At this point, the operator enters the closed diameter and the crimp diameter D c  by pressing the “DIE” and “DIAMETER” buttons of the touchscreen  38 , respectively. When either “DIE” and “DIAMETER” is pressed, the screen shown in  FIG. 19  is brought up, providing a data input pad. According to a preferred aspect of the invention, the crimp diameter D c  and die set closed diameter inputs can be entered in any combination of metric and English units, e.g., inches (“IN”) and millimeters (“MM”), as the controller  36  accepts and converts any combination of these inputs. As such, the controller  36  does not require an operator to perform a conversion when faced with, for example, using a metric die set  24  to produce a crimp diameter D c  specified in English units. 
   Once the crimp diameter D c  and closed diameter are entered, the operator presses the “MANUAL” button of the touchscreen  38  to place the crimper  22  and controller  36  in manual mode, at which time the operator is able to perform a first crimp cycle to confirm that the desired crimp diameter D c  is obtained with the particular combination of hose  12  and fitting  14  being used. The crimp diameter D c  of the crimped assembly  10  can be measured manually with a micrometer. Because of the compensation algorithm employed by the controller  36 , the likelihood of an incorrect crimp diameter D c  is greatly reduced compared to prior art crimpers. However, if a minor correction is necessary because the crimp diameter D c  falls outside the tolerance range established for the hose and fitting assembly  10 , the controller  36  and its touchscreen  38  enable such corrections to be made in a simple step that does not require the operator to perform any computations. Instead,  FIG. 20  shows a screen displayed on the touchscreen  38  at the completion of the crimp cycle, with an “ADJUST CRIMP” button. Pressing this button causes the screen shown in  FIG. 21  to appear, where the operator simply enters the measured crimp diameter D c  of the hose and fitting assembly  10 . The controller  36  then automatically calculates the difference between the desired and actual crimp diameters, and calculates the amount of travel adjustment needed for the piston  26  to obtain the desired crimp diameter D c . The measured crimp diameter can be input in either metric or English units by pressing the appropriate region of the touchscreen  38 , which brings up an input screen similar to that of  FIG. 19 . While a single correction will usually bring the assembly  10  into specification, the correction process can be repeated as many times as may be required. 
   Because tolerances and other factors can occur over the course of numerous crimping cycles that can cause the actual crimp diameter D c  to drift, the controller  36  preferably includes a screen (not shown) that allows the operator or others to set a maximum number of crimping operations that can be performed before the system  40  stops and requires the operator to perform and manually input another crimp diameter measurement. 
   From the above, it can be appreciated that the crimper  22  controlled with the controller  36  and compensation algorithm of this invention is capable of more precisely and reliably obtaining a desired crimp diameter as a result of modifying the travel of the cylinder piston  26  (and therefore the die set diameter D d ) based on the pressure required as the die set  24  approaches the crimp diameter D c . According to conventional practice, the position sensor  30  employed by this invention to sense the position of the piston  26  (corresponding to the die set diameter D d  of the die set  24 ) would be used to determine when the die set  24  arrived at the targeted die set diameter D d  during crimping. However, the present invention adjusts the travel of the piston  26  based on the pressure sensed by the pressure sensor  34 , which effectively senses the effort required to make the crimp. Based on  FIGS. 5 and 6 , this adjustment based on pressure is able to compensate for varying levels of spring-back attributable to variations in hose and fitting combinations. Based on  FIG. 11 , this adjustment based on pressure is also able to compensate for the deflection of the crimper  22  which, as seen from  FIG. 12 , also creates errors in the die set diameter D d  relative to the position of the piston  26 . As a result, an operator is able to enter the desired crimp diameter D c  and will seldom be required to manually calculate and enter an offset to achieve the correct crimp diameter D c . 
   While the invention has been described in terms of a preferred embodiment, it is apparent that other forms could be adopted by one skilled in the art. For example, the physical configuration of the hose, fitting, crimper, and controller could differ from that shown, and process steps other than those noted could be use. Therefore, the scope of the invention is to be limited only by the following claims.