Abstract:
An automated system for testing a variety of transmissions and drive line gearbox components, and more particularly helicopter transmissions, for reliability, life expectancy, efficiency, and the like on a semi-automated basis. The system powers a unit under test with a pair of AC, variable speed drive motors connected to the transmission through relatively low speed gearboxes which in turn drive the input(s) of the test unit through geared cartridge spindles (GCSs) employing planetary gearset inputs driving a higher speed machine tool type spindle with an output chuck system which can automatically couple to adapters preloaded on the unit under test. Similar GCSs couple the outputs of the test unit to AC motors which act as generators to power the driving motors and thereby reduce the required electric power input to the losses in the system. A unit to be tested is loaded onto a positioning fixture supported on a rollable test pallet, equipped with sensors and GCS adapters, and moved into the test module where it is clamped into position and connected to the GCSs to provide input and output connections. The main rotor shaft is connected to the regenerative motor generators through a dual, 90 degree combiner gear box that includes a hydraulic thrust loading actuator for imposing axial forces against the mast. The gearboxes between the motors and the unit under test will accommodate several different types of unit under test and can be replaced to accommodate still other types.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority of U.S. Provisional Patent Application 61/375,718 filed Aug. 20, 2010, the contents of which are incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates to systems for testing transmissions and other gearboxes for reliability and life expectancy and more particularly to a system for testing a variety of different forms of helicopter transmissions, sequentially in a semi-automated manner. 
       BACKGROUND OF THE INVENTION 
       [0003]    Prior art systems for testing transmissions and the like for reliability, life expectancy, efficiency, and the like have typically been designed to test a single form of transmission. The transmissions have typically been manually loaded into a test machine driven by electric motors, with connectors manually inserted between the units and the motors. The outputs of the transmissions have been loaded by manually connecting the transmission outputs to a loading device such as a clutch, dynamometer or brake system. After the testing has been completed, the unit under test must be manually disconnected from the drive and load device. 
         [0004]    This process is very time consuming and labor intensive and the production rates are very low. If a different form of transmission needs to be tested, a separate test machine design needs to be generated, built and provided for that transmission. In situations where multiple transmission types are to be tested in a single facility, the plant space and capital investment required for the separate test modules is extensive. 
         [0005]    The primary test machine gearboxes used in these prior art test systems are required to operate at the high speeds of the transmission inputs. In the case of helicopter transmissions, the power ranges up to about 4500 horsepower and speeds ranging up to 25,000 rpm. These gearboxes are accordingly expensive and difficult to maintain. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention is broadly directed toward a system and apparatus for testing transmissions and like gearbox products and more particularly helicopter transmissions. The system comprises means for loading the units to be tested into a test module in a rapid and semi-automated manner, to provide efficient drive and loading in simulation of operating conditions, and to remove the unit under test in a semi-automated manner. Moreover, each test module is designed to receive a variety of different related designs of gearbox products with relatively minor modifications of the test module required for changeover between different forms of units to be tested. 
         [0007]    In achieving these goals the system incorporates a unique method of applying and removing power from high speed, high horsepower transmissions and the like utilizing a unique geared cartridge spindle (GCS) which has utility in systems other than transmission test facilities. 
         [0008]    In a preferred embodiment of the system of the present invention, subsequently disclosed in detail, a unit to be tested is loaded it onto a transportable test fixture (TTF) specifically designed to accommodate the particular type of unit under test. In a preparation area various forms of instrumentation such as sensors and the like, lubrication connectors, and adapters for connecting the inputs and the outputs of the unit under test to the GCSs, which in turn connect to the test system, are installed on the unit. The unit may then undergo various preliminary testing steps such as electrical testing and verifying alignment. The TTF will then be loaded onto a wheeled transport cart which is used to move the unit from the preparation area to a flexible test module (FTM). The FTM includes two sets of clamps, which engage the TTF depending on its design, in a precise manner and lift the TTF off its cart which may then be removed. 
         [0009]    The FTM itself incorporates several motor generators. In the preferred embodiment of the invention, the motor generators are AC devices with their speeds controlled by variable frequency drives. The preferred embodiment of the system operates off of an AC supply line which changes the incoming power into direct current through a converter and feeds a DC bus which services all of the motor generators. Each motor generator has a separate inverter to convert the DC to AC and a variable frequency drive for controlling its speed. When testing a given unit, certain of the motors are connected to the inputs of the transmission or gearbox and others are connected to the outputs and act as the loading device. The output driven motor generators feed electrical power through their inverters back to the DC bus so that the total electrical power requirements for the system are minimized. 
         [0010]    The FTMs are equipped with custom gearboxes which accommodate each module to the inputs and outputs of the unit under test primarily through GCSs. The gearboxes are removable from the FTM and each gearbox module is preferably designed to connect to the same motor generators and to accommodate several different types of units to be tested in terms of the positions and orientations of their connectors to the unit. If a wide variety of types of units are to be tested, it may be necessary to provide a plurality of different gearboxes to accommodate all of the styles of units to be tested, but preferably only a few gearbox designs will accommodate the widest arrangement of units to be presented to the system. 
         [0011]    The system employs a number of GCSs. These represent a common design used in the preferred embodiment of the system to couple the outputs of the gearboxes to the units under test and to connect the outputs of the units under test to the loading electrical generators which receive the output power from the transmission and generate power which is fed back to the DC bus to decrease the net electrical power input into the system to the losses incurred in the feedback loop. 
         [0012]    These GCSs contain all the high-speed gearing required by the system so that they can be inserted in a “plug and play” fashion into the lower-speed primary gearboxes, which present position and orientation for each transmission. The GCSs used in the preferred embodiment of the invention may transmit power ranging up to about 3000 horsepower at speeds ranging up to 23,000 rpm. 
         [0013]    Each GCS consists of a planetary gearset coupled to a high speed, machine tool type spindle. The planetary gearset can handle the high power levels in a compact configuration and provides a self-piloting configuration that does not impose any radial forces on the spindle drive shaft. The planetary gearset is comprised of a ring gear input, a sun gear output, and a fixed planet carrier. The sun gear drives the input to the high-speed spindle. With a 4:1 ratio, the planet bearings will rotate at approximately two thirds of the spindle velocity while all other bearings within a flexible test module will run at one fourth or less of the spindle velocity. 
         [0014]    The output of each GCS, or the input when the GCS is connected in a speed reducing configuration, is a chuck system drivingly connected to the spindle. The chuck is supported for extension and retraction relative to the other components of the GCS along the central axis of the GCS for connecting and disconnecting the GCS to the adapters on a unit under test (UUT) by a pneumatic power system. Pneumatic power is also applied to the chuck to move it between an open position, in which it is adapted to engage an adapter and a closed position. Actuating power is supplied to the body of each GCS through an integrated pneumatic connector. In addition to opening and closing the chuck and advancing and retracting the chuck, the pneumatic power drives a seal plate longitudinally along the central axis of each GCS into engagement with a mating plate on the chuck base in order to connect the pneumatic power to the chuck. The seal plate is extended and retracted by a series of pneumatic actuators which are radially spaced around the GCS and have their piston rods connected to the seal plate. 
         [0015]    The adapter which is connected to the unit under test has a central locating knob which faces the chuck and is engaged by the chuck. The face of the adapter surrounding the locating cone has several radial lobes, three in the case of the preferred embodiment. Power is transferred from the chuck body to the adapter hub through six spring loaded drive pins which are arrayed at spaced angular intervals about the face of the chuck and project toward the adapter plate. When the chuck is advanced against the adapter, three of the drive pins will usually engage the radial slots and three of the pins will project against the adapter face forward of the slots and be forced to retract under their spring biases by contact with the adapter. 
         [0016]    Once the chuck is in contact with the adapter hub, pneumatic power is removed from the drive piston to stop advancing motion of the chuck, the adapter hub central locating knob is axially secured to the chuck using a ball lock and torque is applied to the chuck base through the spindle. The rotating chuck body slips radially relative to the adapter hub until the three engaged drive pins each contact the end of their engaged radial slots. At this point the three compressed drive pins extend into the opposed ends of each of the slots removing potential backlash and allowing reverse rotation through the spindle. 
         [0017]    Testing power is then transferred from the spindle to the unit under test through the adapter hub. During testing, attached sensor outputs are provided to an operator attended machine control and data analysis and recording system. When the testing is completed, pneumatic power releases the ball lock and withdraws the chuck from the adapter hub to allow the unit under test to be removed. 
         [0018]    The FTM incorporates a motor structure which supports the drive and regenerative motors in spaced relation for connection to gearboxes. The UUTs, which are connected to the gearbox when the chucks on the GCSs are pneumatically advanced, are supported beneath the main mast framework which is itself supported above the unit under test allowing the mast of a helicopter transmission to extend upwardly through an aperture in the framework. The top of the main mast structure supports an actuator for use with helicopter transmissions which connects to their masts to loading motor generators in a manner similar to the way the GCSs connect to the adapters. Thrust is also applied through an integrated hydraulic actuator which imposes load on the main mast in an axial direction. The tail output of a helicopter transmission is connected to a GCS which provides a reduced speed output through a gearbox to a motor generator smaller than the others. 
         [0019]    After the test routine has been completed, the chucks of the GCSs and the main mast actuator are retracted, the wheeled cart is repositioned under the transportable test fixture and its loaded unit under test, and the unit under test is removed from the flexible test module and then from the transportable test fixture. 
         [0020]    In the preferred embodiment of the invention the GCS may be used both as a gear reducing unit and a speed increasing unit. For example, in certain helicopter transmissions having a tail output shaft, an adapter may be connected to that shaft which is used to drive the GCS from the chucking end, through the high speed spindle, and the planetary gear system, to provide a reduced output speed which may be applied to a load motor through the gearbox. 
         [0021]    The GCS has utility in a variety of systems other than transmission or gearbox testing. For example, it might be employed in tool changing automatic machining systems, robotic manufacturing systems, and the like. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]    Other objects, advantages, and applications of the present invention will be made apparent by the following detailed description of a preferred embodiment of the invention. The description makes reference to the accompanying drawings in which: 
           [0023]      FIG. 1  is a schematic view of the apparatus employed in the preferred embodiment of the transmission testing system, illustrating the flow of the transmissions through the system; 
           [0024]      FIG. 2  is a perspective view of a unit under test supported on a transportable test fixture and positioned above a transportation cart on which the transportable test fixture will be loaded for processing; 
           [0025]      FIG. 3  is a perspective view from the top and the right side of a flexible test module formed in accordance with the present invention; 
           [0026]      FIG. 4  is a front view of the flexible test module of  FIG. 3 ; 
           [0027]      FIG. 5  is a side view of the flexible test module of  FIG. 3 ; 
           [0028]      FIG. 6  is a perspective view of a UUT supported on a clamped TTF and connected to its gearbox. 
           [0029]      FIG. 7  is a perspective view, from the top of the main mast torque and thrust unit employed in the flexible test module; 
           [0030]      FIG. 8  is a side perspective view of the main mast torque with the bevel gear set cover removed; 
           [0031]      FIG. 9  is a schematic diagram of the mechanical and electrical power flow through a flexible test module; 
           [0032]      FIG. 10  is a perspective view of a geared cartridge spindle; 
           [0033]      FIG. 11  is a longitudinal, cross-sectional view of a geared cartridge spindle with the chuck in an extended position; 
           [0034]      FIG. 12  is a cross-sectional view through the chuck end of a geared cartridge spindle with the chuck retracted; 
           [0035]      FIG. 13  is a perspective view of the chuck end of a geared cartridge spindle positioned opposite to an adapter which may be engaged by the geared cartridge spindle; 
           [0036]      FIG. 14  is a side perspective view of the adapter; 
           [0037]      FIG. 15  is an end view of the adapter; 
           [0038]      FIG. 16  is a top view of the adapter. 
           [0039]      FIG. 17  is a schematic illustrating the electric power system of the FTM. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0040]    While the system of the present invention is useful with the accelerated life and efficiency testing of a variety of gearboxes, the preferred embodiment of the invention is designed to test a variety of helicopter transmissions, with their special features such as rotor blade masts and tail drives. 
         [0041]      FIG. 1  illustrates in schematic form the process of preparing a particular transmission under test (a unit under test or UUT)  102  for testing, transporting it to a flexible test module (FTM)  100  and associated controls and analysis equipment, and removing the UUT after testing. A UUT  102  will be loaded onto a transportable test fixture (TTF)  104  that is specially designed to support the UUT in proper orientation for testing. The TTF will incorporate an RFID tag which identifies the UUT and the TTF, an instrumentation junction box for coupling with the UUT, and a lubrication manifold for providing necessary lubrication required during the test. The TTF is then loaded on a wheeled cart  106  and moved to a staging area where adapters, which will later be disclosed in detail, are connected to the various inputs and outputs of the UUT. The cart is then moved into the test cell area  100  where it is clamped into operating position and the necessary GCSs are connected to the UUT through the adapters. 
         [0042]    The UUT is then powered through drive motors and loaded through motor generators and experiences a test routine with the sensors forming part of the instrumentation transmitting the measurements under testing to an operator attended control room which performs data logging, detailed analysis of the tests, manages test profiles, and displays all the pertinent information to the operator. After testing has been completed, the TTF is unclamped from the FTM and moved out of the test cell area. The UUT is then removed from the TTF. If it passed the test process, it is moved to a shipping area. If it didn&#39;t pass the test process, it is shipped to a repair area. 
         [0043]      FIG. 2  illustrates, in exploded form, a helicopter transmission  102  to undergo testing positioned over a transportable test fixture  104 , custom designed to accommodate the type of transmission to be tested, and a transportation cart  106  supported on casters  108  which allows the transmission and the TTF  104  to be manually moved into a staging area and then into the test cell area  100 . 
         [0044]    The next step is to connect adapters to the inputs and outputs of the transmission  102  which will connect to the FTM through GCSs to power the inputs to the transmission and act as loads for the outputs. In  FIG. 2 , three of the adapters  500 , which are supported on extension shafts  120 , are visible. A main mast adapter  110  is also supported on the mast of the UUT  102  ( FIG. 6 ). This adapter shaft incorporates all connection, instrumentation, and geometry required to connect the mast to the FTM and to automatically connect, apply torque, and apply thrust to the UUT. 
         [0045]    The UUT, supported on the cart  106 , is then moved into the FTM, generally indicated at  200  in  FIG. 3 , in a front view in  FIG. 4 , and in a side view in  FIG. 5 . The FTM  200  broadly comprises two sections, a powerhouse section  202  which houses the motor generators and a UUT support structure  204 . The support structure  204  includes a pair of opposed clamps  206  which engage and locate the opposed sides of the TTF supporting the UUT  102 . Each side includes a hydraulic cylinder attached to guide rods (not shown) that lift the TTF off of the cart and insert it into a locking cylinder (not shown), on the clamping structure which precisely positions and locates the TTF and UUT for testing. The UUT is free of the cart  106  at that point and the cart may be removed during the testing period. 
         [0046]    For certain units under test with mast side mounting features, rather than clamping the units with the clamps  206 , they are locked in position in the FTM by a pair of upper clamps  208  supported beneath a horizontal bridge  210  forming part of the UUT support structure  204 . These clamps  208  engage and align the TTF and UUT in the same manner as the lower clamps. 
         [0047]    The adapter  110  is loaded on the transmission mast. The mast adapter is engaged by a main mast torque and thrust unit  212 , supported on top of the bridge  210 , which comprises a right angle bevel gear connector to two motor generators  214  and  216  which are supported in the powerhouse structure. The motors  214  and  216  are connected to two spaced inputs on the torque and thrust unit  212  by shafts  218  and  220 . 
         [0048]    The power house structure  202  supports another pair of input motors  222  and  224  ( FIG. 9 ) on the lower level. These motors connect through shafts  226  to primary gearboxes  228  and  230  which are configured to accommodate a particular UUT and are sufficiently adjustable to accommodate similar UUTs. These gearboxes may be replaced with configurations which will service another range of gearboxes to be tested when necessary. 
         [0049]    A UUT  102 , supported on a TTF  104 , engaged by clamps  206 , and connected to a gearbox  230 , by GCSs  400 , is shown in  FIG. 6 . The gearbox  230  is adaptable to service a range of different helicopter transmissions. For example, the sections  600  do not connect to the UUT shown in  FIG. 6  but are used in connection with other forms of transmissions. These sections may be removably attached to the gearbox  230 , which is shown without any attachments in  FIG. 9 . 
         [0050]    The main mast torque and thrust unit  212  is illustrated in a top perspective in  FIG. 7  and with the gear cover removed in  FIG. 8 . The unit comprises a spaced pair of right angle drives  300  and  302  which connect through the shafts  218  and  220  to the motor generators  214  and  216 . Each of the right angle drives connects to a generally vertically aligned shaft driven by the mast adapter  110 . The input of right angle drives  300  and  302  are driven by bevel gears  304  and  306 , both of which are driven by a bevel gear  308  connected to the generally vertically aligned output shaft of the unit  212 . A thrust plate  312  is connected to the same shaft and is driven along the axis of the mast adapter  110  by four hydraulic actuators  314 . The output shaft of the unit  212  also incorporates a planetary gear set speed reducer  316 . 
         [0051]    The main rotor masts of the range of helicopter transmissions to be tested by the FTM  200  are not all oriented exactly vertically with respect to the normal orientation of their transmission bodies, in use, as are provided by the TTFs  104 . The angles with respect to the vertical may range up to about +/−10°. To accommodate this variation the unit  212  is pivotably adjustable about a horizontal axis aligned through the axis of the bevel gears  304  and  306 , about two pedestals  318  which support the unit  212 . The TTFs  104  support the transmissions so that the masts of the different transmission types all project in the plane of adjustability of the shaft connector of unit  212 . 
         [0052]    The helicopter mast, through the adapter  110 , is rotationally loaded by the force required to turn the motor generators  214  and  216  and simultaneously axially loaded by the force exerted on the thrust plate  312  by the actuators  314 . 
         [0053]    The gearboxes  228  and  230 , as well as a gearbox  270  which applies load to the helicopter tail rotor drive, are uniquely designed for each UUT type to be tested so as to apply driving power to the UUT inputs and to receive power from the UUT tail drive in a manner that accommodates the position and orientation of each of the shafts of the UUT. The gearboxes  228  and  230  have connections to the drive and driven motors as schematically illustrated in  FIG. 9 . The outputs of these gearboxes are provided to the UUT through GCSs  400 . A particular gearbox combination may be used with several styles of similar transmissions and the entire gearbox is removable so that it may be replaced with an alternative form of gearbox for accommodating other transmissions. 
         [0054]    The power flow through the FTM  200  is illustrated in  FIG. 9 . A UUT  102  supported on a TTF  104  is provided with input power through a pair of GCSs  400  which connect through a gearbox  230  and  228 . 
         [0055]    The inputs to the gearbox are from motor generators  224  and  222  which receive electrical power from a control panel  260 . As shown in  FIG. 17  each of the motor generators  280 ,  214 ,  216 ,  222  and  224  is powered by a separate unit  290  which includes an inverter for converting power on a DC bus  292  to AC and a variable generate generator to control the speed of its associated motor-generator. Each motor-generator has a speed sensor  292  which feeds back to the associated unit  290  to meet speed commands provided from the controller  260 . The DC bus is powered by an AC-DC converter  294  from an AC power line  296 , as well as feedback from the line loading motor generators. 
         [0056]    The mast output adapter  110  of the UUT  102  is connected to the mast actuator  212  which connects the shaft rotation to the two motor generators  214  and  216  which provide the load to the rotor while the hydraulic actuators associated with the mast actuator apply axial thrust to the mast. The motor generators  214  and  216  provide their electrical outputs back to the control system  260 . 
         [0057]    The tail shaft output of the UUT  102  is also provided through a GCS acting as a speed reducer to a gearbox  270  which drives a smaller motor generator  280  which also provides its output power to the control panel  260 . 
       Geared Cartridge Spindle (GCS) 
       [0058]    The GCSs are illustrated in  FIG. 10  which shows a perspective view of a GCS;  FIG. 11  which is a cross section through the central axis of a GCS showing the chuck end in an extended position;  FIG. 12 , a section through the chuck in a retracted position;  FIG. 13  which is a perspective view showing the end of the chuck forming part of the GCS positioned opposite an adapter which has been connected to the UUT in the prep area; and  FIGS. 14 ,  15 , and  16  which illustrate the adapter hub in perspective, in an end view, and in a top view, respectively. 
         [0059]    Each GCS, generally indicated at  400 , is comprised of a planetary gear section  402 , a high speed machine tool type spindle  404 , and a chuck support section  406 . In the preferred embodiment of the invention the planetary gear set preferably provides a gear ratio of approximately 4:1. The GCS  400  is generally used in the present system to increase the speed of a relatively low speed output from a gearbox, but in the case of a helicopter tail output the GCS is used in a reverse manner to accept a higher speed from the transmission tail output and provide a lower speed output to the primary gearbox and thus to a motor generator acting as a load on the tail output. 
         [0060]    The input to the GCS (or output in case of the tail output) is provided to a ring gear (not shown) of the planetary gear assembly through coupling elements in the primary gearbox over the input end of the planet carrier. A sun gear  414  driving through an integrated shaft provides the output of the planetary gear set or, in the case of the tail gear, the input. The sun gear shaft  414  is joined by a flexible coupling or splined connector  416  to the shaft  418  of the spindle  404 . The shaft is supported in a series of high speed roller bearings  420  which ensure precision rotation and support of the high-speed spindle. 
         [0061]    The output end of the spindle rotates the chuck  406 . The base of the chuck  407  is rigidly connected to the output end of the spindle shaft  418  and receives its support from the spindle shaft. The forward face of the chuck  406  comprises a locating cone  424 . 
         [0062]    A plurality of pneumatic seal plate actuators  426  have their bases supported about the spindle on a mount plate  428 . The rods of the spindles connect to a seal plate  430  which is supported for movement along the central axis of the GCS  400  on the spindle  404  body. 
         [0063]    Six spring loaded drive pins  434  are radially spaced at the forward end of the chuck around the locating cone  424 . The drive pins  434  are slidably supported for axial motion between an extended position, illustrated in  FIG. 10 , and a retracted position in which their far ends are withdrawn behind the cone  424 . Internal springs in each of the pins  434  bias them toward the extended position. 
         [0064]    The adapter plates, generally indicated at  500 , which are secured to the unit under test in the preparation stage, are illustrated in  FIGS. 14 ,  15 , and  16 . The adapter plates  500  are joined to the unit under test by bolts passing through holes  502  extending radially outward from the body of the adapter  500  at equal angular intervals. 
         [0065]    The end of the chuck system  406  comprising the locating cone  424  and the driving pins  434  is slidingly supported for axial motion along the GCS between a retracted position, illustrated in  FIG. 12 , and an extended position, illustrated in  FIG. 11 . This operating end moves along splines so that the rotation of the chuck  406  is transferred to the extending end. The axial motion is driven by a piston  440  which moves within a cylinder  442  under pneumatic power. 
         [0066]    When a unit under test is to be loaded into or out of the FTM, the head of the chuck is retracted. To connect the GCS to the unit under test through one of the adapters  500 , pneumatic power is applied to the cylinder  442  to move the head to its extended position. As the head advances, the locating cone  424  moves over an adapter hub locating knob  506  extending centrally from the face of the adapter hub  500 . The face is formed with three recessed slots  508  which are radially spaced about the knob  506  with each slot extending for about 60 degrees when there are six driving pins  434  formed on the output end of the chuck  406 . The ends of the slots  508  are rounded and the spacing between a pair of slots  508  is such that an adjacent pair of drive pins will fit into the two ends of each slot. 
         [0067]    When the head end of the chuck  406  is advanced through the piston  442 , the orientation of the adapter hub and the chuck body is unknown. Unless the orientation happens to be so precise that each pair of pins  434  will precisely hit the ends of the slots  508 , three of the pins will engage the slots while the other three pins will be compressed, against their spring biases, by the areas of the adapter face between the slots  508 . With the chuck body locked axially to the hub  506 , rotation of the chuck body will allow all six pins to engage in their driving positions, at the ends of the slots  508 , so that rotary power will be transferred from the chuck to the adapter, and thus to the unit under test, in either direction. Pneumatic power is applied to the chuck to advance, retract, and unlock the knob while not testing through a pneumatic connector  450 . This connector is supported on a nonrotating portion of the seal plate  430 . 
         [0068]    The sequence of operation of the pin drive system is as follows:
       1. The chuck is retracted and the mating adapter hub fixed to the unit under test in the prep area is presented for automatic connection.   2. The high speed spindle shaft  418  and the pin drive system are static or nonrotating.   3. The pneumatic seal plate  430  is advanced by the actuators  426  and creates sealed pneumatic paths between the pneumatic passages within the seal plate  430  and chuck base  407 .   4. Pneumatic power is applied to release the ball chuck within the cone  424 .   5. Pneumatic power is applied to advance the chuck through the drive piston  440 .   6. The drive pins  434  move forward with the chuck body. Longitudinal guides for the chuck body movement are provided by its splined engagement with the housing  406 , the front housing cap, and the drive piston  440 .   7. The locating cone  424  in the chuck body engages the mating alignment knob  506  on the adapter hub, positioning the chuck and hub concentrically.   8. Three of the six drive pins  434  engage the adapter hub drive slots  508  and the three drive pins between them are compressed against their spring biases by contact with the sections between the slots.   9. Pneumatic power is removed from the ball chuck allowing the spring actuated lock within the ball chuck to secure the chuck body to the adapter hub knob  506 .   10. Pneumatic power is removed from the drive piston  440  to stop advance motion of the pin drive system.   11. Torque is applied to the pin drive system chuck base through the high speed spindle shaft  418 .   12. The rotating chuck body slips relative to the adapter hub  500  until the three engaged drive pins contact the ends of the radial slots.   13. The three compressed drive pins then extend into the back side of the adapter hub radial slots  508  removing potential backlash from the pin drive system and allowing reverse rotation.   14. Power is transferred from the high speed spindle shaft  418  through the pin drive system to the adapter hub.   15. After testing is completed the rotation of the high speed spindle, the pin drive system, and the adapter head is stopped.   16. Pneumatic power is applied to release the ball lock allowing the adapter hub  500  to be freed.   17. Pneumatic power is provided to the drive piston rear side to retract the chuck body away from the adapter hub.