Abstract:
A torsion tester incorporates a microprocessor based data acquisition/control package and special tooling. The tooling makes calibration of the tester very easy. The combination of the tooling and control package permits acquisition, storage and transfer of test data that is accurate, absolute and repeatable. In addition, torsion tester provides a zeroing pin and a zeroing slot on opposing tooling members for calibration. Further, the torsion tester provides an interchangably mounted load cell.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of co-pending application Ser. No. 09/169,254, filed Oct. 9, 1998, which claims the benefit of U.S. Provisional Application No. 60/062,352, filed Oct. 15, 1997. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a system for testing torsion springs. More specifically, the present invention relates to a torsion spring tester having dedicated fixtures which permit absolute measurements rather than relative measurements to be taken of the spring and further permits the results of such measurements to be repeatable. 
     2. Description of the Related Art 
     A variety of torsion spring testers have been available for a number of years. These torsion spring testing machines are designed for checking torque loads in inch ounces and inch pounds and deflections in degrees. They are intended for use with a variety of springs including torsion springs, double torsion springs, spiral springs, clock springs, motor springs and power springs. Early spring testers work in conjunction with a balance and weights to determine torque load. Such units also typically included a protractor to permit one to read deflection in degrees. More recently, various companies have developed digital torsion spring testers. Such testers typically utilized a load cell and an “electronic protractor” measuring deflection. 
     Testers of the type described above are manufactured by The Carlson Company of Clinton, Ark., the Spring Research and Manufacturers&#39; Association of Sheffield, England and Link Engineering Company of Plymouth, Mich. 
     Testers of the type described above offer a variety of advantages. However, set up, use and recordation of information using such testers generally tends to be time consuming. Further, the results tend not to be repeatable. As such, there is a real need for a torsion spring tester which is quick and easy to use, is quick and easy to calibrate, and is capable of providing measurements which are repeatable. There is also a real need for a torsion spring tester that provides absolute measurements rather than relative measurements. 
     SUMMARY OF THE INVENTION 
     The present invention relates to a new torsion spring tester that is easy to use, easy to calibrate, generates repeatable results and provides absolute rather than relative measurements. The system includes a carriage, a first housing secured to the carriage in a fixed position, and a second housing slidable back and forth along the carriage. The first, fixed housing contains a faceplate coupled to a tube, and a microprocessor based data acquisition/control package. It also contains a specially designed load cell which measures the load and transfers the data into the electronics package. Running through the tube in the first housing is a threaded shaft which is coupled to a knob. The threaded shaft is used to couple a tooling blank to the faceplate in the housing. 
     The second housing includes three individually positionable stops, a sliding stop bar, and a knob used to fix the stops in place. The second housing also includes a face plate coupled to a tube. A threaded shaft running through the tube is used to couple a second tooling blank to the face plate on the housing. The tube is also coupled by a belt to an encoder. The encoder is used to measure rotation of the tube. To impart rotational motion to the tube (and thus to the face plate and tooling blank), the housing is provided with two exterior knobs. These knobs are coupled to a gearing arrangement. A switch is also provided to activate one knob or the other. Since the gearing ratio associated with the two knobs are different, one of the knobs can be used for gross rotation of the tube while the other can be used for fine rotation of the tube. Signals from the encoder are transmitted via a cable to the electronics package in the first housing. 
     A key aspect of the present invention is the tooling that is used in conjunction with the first and second housings. As explained above, each tooling member includes a blank which is coupled using the threaded shaft to the face plate of the specific housing. The tooling secured to the second housing, in addition to the blank, includes a mandrel and a first engagement bar. The tooling secured to the first housing includes a second engagement bar. Also provided are first and second zeroing elements. The first zeroing element is a pin that can be coupled to one of the tooling blanks. The second is a slot in the other tooling blank which receives the pin. When the first and second blanks are attached to the face plates of the first and second housings, the second housing is slid toward the first housing until the pin engages the slot. Switches associated with the electronics are then used to indicate to the electronics that the device is now in the zeroed position. Once zeroing is complete, the second housing can be slid back along the carriage and the pin can be removed. A spring can then be placed over the mandrel and easily tested. The fact that the second housing incorporates three stops allows the spring to be easily tested at three preset angles of deflection. 
     Another key aspect of the present invention is the use of a replaceable load cell cartridge designed to be interchangeable with other load cell cartridges. This offers significant advantages. First, it broadens the number of applications for which the spring tester can be used. Second, it makes calibration of the load cells much more efficient. For example, the National Association of Spring Testing recommends that load cells be calibrated annually. Prior to the present invention, the whole machine would have to be shipped for calibration, making it unavailable for use for a significant period of time. The present invention allows the owner to merely remove and ship the cartridge. The rest of the machine can continue to be used with a replacement cartridge. 
     The replaceable load cell cartridges can either be dumb or smart. Dumb cartridges include only a load cell. When calibrated, the performance characteristics are noted in writing so that the user can manually input those characteristics into the machine as part of the cartridge installation process. Smart cartridges include memory and input/output capabilities. Thus, parameters related to the calibration of the cartridge can be stored in memory during the calibration operation and electronically read by the machine. This serves to eliminate the need to manually input these parameters during installation of the cartridge. 
     Various other advantages and benefits of the present invention will become clear from a thorough reading of the following detailed description of the preferred embodiment in conjunction with the figures provided herewith. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an elevational plan view of one side of the device of the present invention. 
     FIG. 2 is an elevational plan view of the opposite side of the device shown in FIG.  1 . 
     FIG. 3 is a block diagram of the electronics of the present invention. 
     FIG. 4 is a perspective view showing various components associated with the first housing of the device shown in FIG.  1 . 
     FIG. 5 is a perspective view of various components associated with the second housing of the device shown in FIG.  1 . 
     FIG. 6 is a top plan view of the second housing with portions thereof cut away to show the manner in which tooling is coupled to the housing. 
     FIG. 7 is a view of a typical display and key pad arrangement. 
     FIG. 8 is a perspective view of two typical tooling members. 
     FIG. 9 is a perspective view of two alternative tooling members. 
     FIG. 10 is a perspective view of a load cell cartridge housing. 
     FIG. 11 is a cross-sectional view of the contents of the load cell cartridge housing of FIG.  10 . 
     FIG. 12 is a schematic diagram of the electronics package of a smart load cell cartridge. 
     FIG. 13 is a perspective view with portions cut away to show the manner in which the load cell is actuated. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIGS. 1 and 2 are perspective views of the present invention. Shown in these figures is a carriage  1 , a first housing  2  fixed in place at one end of the carriage  1 , and a second housing  3  mounted to rails  4  and  5  of the carriage so that the second housing  3  can slide back and forth along the rails  4  and  5 . 
     As shown in FIG. 1, the first fixed housing  2  includes a control panel  6  which includes a display  7  and a key pad  8 . The display  7  is preferably a liquid crystal display. The key pad  8  preferably includes ten switches  8   a - 8   j  as shown in FIG.  7 . The control panel  6  provides an interface between an electronics package  9  (see FIG. 3) and the user. 
     FIG. 3 is a block diagram of the electronics package  9 . As shown in FIG. 3, the electronics package  9  includes the display  7  and switches  8  which are labeled  8   a - 8   j  in FIG.  7 . The electronics package also includes a microprocessor  10  and three types of memory, static random access memory (RAM)  11 , electrically programmable read-only memory (EPROM)  12 , and electrically erasable programmable read-only memory (EEPROM)  13 . The program of instructions for controlling operation of the device is stored in the EPROM  12 . Data collected by the device can be stored in the EEPROM  13 . 
     In one embodiment, the electronics package  9  also includes a load cell  14 . The load cell  14  is electrically coupled to a pair of amplifiers  15  and  16  which are, in turn, coupled to a pair of analog-to-digital converters  17  and  18  which convert the analog signals from the load cell  14  to digital signals which are forwarded to the microprocessor  10 . The electronics package  9  also includes a clock  20  and an RS232 interface  21 . The RS232 interface  21  can be used to electrically couple the device to a printer (not shown) or personal computer (not shown). This permits data to be printed or to be stored on a separate computer where the data can be manipulated or otherwise further processed. Another important aspect of the electronics package  9  is the encoder  22 . While the encoder  22  is physically located within the second housing  3 , it is hardwired to the electronics package  9  so that signals generated by the encoder  22  are received and processed by the microprocessor  10 . 
     As an alternative to the permanent installation of a load cell  14 , a load cell cartridge  100  which houses a load cell  14  can be used. See FIGS. 10-12. Such a cartridge  100  includes a housing  102  designed to allow the cartridge  100  to be physically mounted to one of the housings  2  or  3 . The cartridge  100  also includes a jack  104  for electrically coupling the cartridge  100  to the rest of the electronics package  9 . The housing  102  and jack  104  are both shown in FIG.  11 . 
     Two varieties of load cell cartridges  100  are contemplated by the present invention. One is a “dumb” cartridge which includes nothing other than the load cell  14 , the housing  102  which allows it to be physically coupled to either the fixed housing  2  or the slidable housing  3 , and the jack  104  which carries signals generated by the load cell  14  to the rest of the electronics package  9 . The other is a smart cartridge which includes all of the elements of the dumb cartridge plus a memory module  106  comprising the electronic elements shown in FIG.  12 . The memory module  106  is coupled to the load cell  14  by the jack  104  and allows data relating to the performance characteristics of the load cell  14  to be electronically stored in the cartridge  100 . The memory module also is capable of sending signals to the rest of the electronics package  9  via port  105 . 
     Significant advantages are achieved through the use of interchangeable load cell cartridges  100 . First, a variety of load cells rather than a single load cell  14  can be used on the same machine. This greatly increases the capability and flexibility of the machine. Also, if a plurality of cartridges are available, there is no down time during calibration of the load cell or need to ship the entire machine to a remote location for calibration of the load cell. 
     The difference between a dumb and a smart cartridge  100  relates exclusively to the manner in which load cell performance characteristics are stored and conveyed to the microprocessor  10  of the electronics package  9 . When a dumb cartridge is used, such performance characteristics are entered via the key pad  8  or another data entry device, such as a personal computer, attached electrically and coupled to the electronics package  9 , via the RS232 interface  21 . The advantage of the smart cartridge is that these performance characteristics can be stored in the memory module  106  and transferred automatically to the microprocessor  10  of electronics package  9 . Such performance characteristics can include, but are not limited to, the full scale value of the load cell  14  in the cartridge, the electrical output of the load cell  14  when zero load is being applied to the load cell  14 , the electrical output of the load cell  14  when a load approximating the full scale value is applied to the load cell  14 , and data that can be used by the microprocessor to linearize the output of the load cell  14 . 
     Turning, then, to FIGS. 1,  2 ,  4 ,  8  and  9  associated with the first, fixed housing  2  is a knob  30  coupled to a shaft  31 . The shaft  31  runs through the fixed housing and is used to join a tooling blank  34  to the face plate  33  of housing  2 . The tooling blank  34  has a generally cylindrical shape including a first face  36 , an opposing second face  38  and a sidewall  40 . Located at the center of the first face  36  is a threaded bore  42 . The threaded bore  42  cooperates with threading on the shaft  31  to secure the blank  34  to the face plate  33  of the housing  2 . As shown in FIG. 4, the blank  34  also has an engagement member  44  projecting perpendicularly from the second face  38  and a zeroing slot  46  in the side wall  40 . The zeroing slot is open through the second face  38 . 
     FIG. 13 shows in greater detail how the engagement member  44  interacts with the load cell  14 . The engagement member  44  projects from the face  38  of the tooling blank  34 . Face  36  of the tooling blank is secured to the face plate  33  of the housing by running the shaft  31  through the tube  32  coupled to the face plate  33 . As such, torque is readily transferred from the engagement member  44  through the tooling blank  34  and faceplate  33  of the housing to the tube  32 . Coupled to the tube  32  is an arm  50 . The end of arm  50  is located a distance of more than 10 thousands of an inch above the load cell  14  so that it never comes into contact with the load cell  14 . A flexible metal strip  52  is attached at one of its ends to the load cell and at the other of its ends to the arm  50 . This strip  52  is used to transfer torque from arm  50  to the load cell  14 . Thus, the load cell  14  is only capable of measuring loads transmitted through the flexible metal strip  52 . First and second bearing elements  54  and  56  secure the tube  32  and arm  50  in place and prevent them from rotating. 
     FIGS. 1,  2 ,  5  and  6  show the second housing  3 . Associated with the second housing are a first wheel  60 , a second wheel  62 , a switch member  64 , three stops  65 ,  66  and  67 , a stop securing knob  68 , a knob  70 , a face plate  71  and a second tooling blank  72 . Like tooling blank  34 , tooling blank  72  has a generally cylindrical shape having a first face  74 , a second face  76 , and a cylindrical side wall  78 . Located at the center of the first face  74  is a threaded bore  80 . A shaft  82  (see FIG. 6) projects from knob  70  through a tube  73  joined to the face plate  71  of the housing  3 . The shaft  82  has a threaded end which cooperates with the threaded bore  80  to fix the tooling blank  72  so that its face  74  is in face-to-face registration with the face plate  71  of the housing  3  and so that its face  76  is in face-to-face registration with face  38  of the first tooling blank  34 . Projecting perpendicularly from the center of face  76  is a mandrel  79 . Also projecting perpendicularly from the face  76  is a second engagement member  81 . A zeroing pin is also provided. The zeroing pin can either be coupled to the engagement member  80  using orifice  83  (see FIG. 8) or otherwise coupled to the tooling blank  72 . To zero the device, the zeroing pin is mated with the zeroing slot  46  and switches on the electronic package is actuated to signal the microprocessor  10  that the device is in the zero position. 
     Located within the housing  3  is a gear box (not shown). The gear box is used to impart rotational motion to the tooling blank  72  via the tube  73  and face plate  71  of the housing  3 . The encoder  22  is positioned to detect movement of the tube  73  and transfer signals representative of rotation of the tube  73  to the microprocessor  10 . The switch member  64  is actuated to selectively couple either the first wheel  60  or the second wheel  62  to the gear box and thus to the tube  73 . The gearing is such that when the first wheel  60  is engaged (via switch member  64 ), it can be rotated for gross rotation of the blank  72 . Alternatively, when the switch member  64  is positioned so that the second wheel  62  is engaged, wheel  62  can be turned to impart fine rotation to the blank  72 . In the preferred embodiment, rotation of wheel  60  turns the blank  72  forty times further than the same rotation of wheel  62 . 
     The housing also includes a sliding stop bar  69 . See FIG.  6 . Stop bar  69  is provided to engage projections on the stops  65 ,  66  and  67  to define the selected angles at which test readings will be taken. 
     The electronics package  9  and the program used in the preferred embodiment combine to offer a variety of advantages. Perhaps the most significant is the ability to compensate for deflection of the tooling blank  34  during testing of a spring. As load signals are sent to the microprocessor  10  from the load cell  14 , the software performs an algorithm which calculates rotation of the tooling blank  34  from the load readings. This calculation is then used to adjust the test data related to the springs to make the deflection data more accurate. 
     As indicated above, the display  7  and keypad  8  provide an operator interface. See FIG.  7 . For example, the keypad includes two zeroing switches,  8   a  to zero the torque and  8   b  to zero the deflection angle. The units switch  8   c  allows the user to tell the microprocessor to store, display and print data in either English or metric units. The store switch  8   d  can be used to send an instruction to the microprocessor  10  to store the data related to the test. The data is then stored in memory  13  where it can later be recalled and displayed or transmitted through the RS232 port  21  to an external computer or printer. The send switch  8   e  is used to instruct the microprocessor  10  to transmit the data through the RS232 port  21  to generate, for example, a hard copy printout of the data. The test mode switch  8   f  is used to select between various preset modes of operation. The option switch  8   g  and the two function switches  8   h  and  8   i  are used to set various parameters. Typically, the option switch is activated to instruct the microprocessor  10  to display various menu options and the two function switches  8   h  and  8   i  are used to select between the menu options. The on/clear switch  8   j  is used to both turn on the device and clear data to begin a new test. 
     In view of the foregoing explanation of the preferred embodiment, its operation will now be described. First, the second housing  3  is slid back along the rails  4  and  5  to separate it a working distance from the first housing  2 . Second, the tooling blank  34  is positioned and secured to the face plate  33  of housing  2  by coupling the threaded end of the shaft  31  to the threaded bore  42 . The knob  30  is used to secure the blank  34  in position. No separate tools are required. In a similar fashion the blank  72  is secured to the face plate  71  of the second housing  3 . The threaded end of shaft  82  is coupled to the threaded bore  80  in the blank  72 . The knob  70  is used to tighten the connection. Again, no additional tools are required. 
     Next, the zeroing pin  82  is inserted into a bore  83  in the end of engagement member  80  to temporarily couple the zeroing pin  82  to the engagement member  81 . The housing  3  is slid along the rails  4  and  5  toward the housing  2 . As this occurs, the blank  72  is rotated so that the zeroing pin  82  is aligned with the zeroing slot  38  in the tooling blank  34 . The housing  3  is slid forward until the zeroing pin  82  rests within the zeroing slot  46 . With the housing  3 , tooling blank  72  and zeroing pin  82  so positioned, and with no load on the engagement member  44 , the operator then depresses the two zeroing switches  8   a  and  8   b . Thus, the microprocessor  10  is able to establish the “zero” deflection angle and torque parameters so that all measurements taken thereafter will be absolute rather than relative. 
     With the housing  3  still in the “zeroing position”, the three stops  65 ,  66  and  67  can be set to establish the angle at which various test data will be recorded. These stops can be set individually using separate setscrews associated with each stop. Alternatively, the stop securing knob  68  can be tightened to simultaneously lock all three stops in place. When the stop securing knob  68  is used, no special tools are required. 
     Once the device has been “zeroed” and the stops have been set, the housing  3  is slid along the rails away from the housing  2 . The zeroing pin  82  is removed and the first spring to be tested is slid over the mandrel  79 . The housing  3  is slid back toward the housing  2  and the spring to be tested is positioned so that one of its outer tines engages one of the engagement members and the other of its outer tines engages the other engagement member. With the spring so positioned, the operator actuates the switch member to  4  to select which of the two wheels  60  or  62  the operator wishes to use. The operator then turns the selected wheel to impart a rotational motion via the tube  73  and face plate  71  to the tooling blank  72 . As the tooling blank  72  rotates, changes in deflection angle and load are displayed. The operator continues to rotate the wheel until the projection  100  in the first stop  65  engages the stop bar  69 . Once this position is reached, the operator hits the store switch  8   d  to cause the microprocessor  10  to load deflection data derived from the encoder  22  and load data derived from the load cell  14  into memory. The stop bar  69  is then moved and the wheel is rotated until the stop bar  69  engages stop  66 . The store switch  8   d  is again actuated to record the new load and angle data into memory. This process is repeated for the third angle defined by the third stop  67 . When the test is complete, the data can be left in the device&#39;s memory, transferred to a personal computer, or printed out. 
     The hardware and software of the present invention offer various advantages over prior art spring testing equipment. As indicated above, the use of interchangeable load cell cartridges  100  enable the user to quickly switch from one load cell range to another. Also, load cell calibration only requires the cartridge rather than the entire machine. Interchangeable tooling and the rapidity with which tooling changes can be made without special equipment greatly increases efficiency. Further, the apparatus is able to perform two-point testing and an automatic spring rate calculation based upon the change in torque and the change in angle. The apparatus is designed so the user can specify a range or tolerance for either load or deflection angle. As springs are tested against the specified range or tolerance, the display indicates whether the measurement for the spring is too low, acceptable, or too high. 
     The foregoing description is not intended to be limiting. Instead, it is intended to provide a description of the preferred embodiment sufficient to enable those skilled in the art to practice the invention, the scope of which will be defined by the claims of the patent. Those skilled in the art will recognize that the present invention is applicable to the torsion testing of a variety of variety of material and objects. Therefore, the present invention should not be limited to the testing of springs.