Abstract:
An indexing tool turret assembly is disclosed including a rotatable indexable turret tooling plate having mounted thereon stationary as well as live tooling. A single drive motor is utilized in order to perform indexing as well as to drive the live tooling. A plurality of live tools can be simultaneously mounted on the turret tooling plate and the single drive motor is selectively engageable with each of the live tools so that only one of the plurality of live tools is driven at a given time. The selective live tool drive train includes an axially movable drive shaft and bevel drive gear for selectively engaging the driven bevel gear of the desired live tool. The axially movable shaft assembly includes a mechanism for adjusting the backlash between the driving and driven bevel gears when these gears are engaged with one another. The turret assembly further includes a clutch for selectively engaging the single drive motor to index the turret tooling plate and a torque limiter provided in the indexing drive train to disengage the indexing drive in the event of a torque overload occurring during indexing.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 60/099,295, filed Sep. 4, 1998. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to an indexing turret assembly for a machine tool and more particularly, to an indexing turret assembly having provisions for mounting both stationary and live tooling. 
     DESCRIPTION OF THE PRIOR ART 
     Indexing turret assemblies have found widespread use in the machine tooling industry. Such assemblies are capable of selectively positioning a plurality of diverse tools into proper alignment with a workpiece so as to allow sequential machining operations to be performed thereon. 
     The most common types of indexing turret assemblies are those which support tools suitable for turning operations wherein the tools are stationary with respect to a revolving workpiece or those which support tools suitable for milling, drilling, tapping, etc., wherein the tools are rotatably driven with respect to a non-rotating workpiece. 
     There are also indexing turret assemblies capable of supporting combinations of stationary and live tooling. Such indexing turret assemblies serve to increase the overall flexibility of the machine tool by allowing greater diversity in the machining operations. 
     One such machine tool is disclosed by Kolblin in U.S. Pat. No. 4,429,443. Kolblin discloses the use of an indexing turret assembly for supporting stationary as well as live tooling and includes a live tooling engagement device movable between a decoupled position and a coupled position by means of a piston and cylinder arrangement. One shortcoming associated with the Kolblin apparatus is that the live tooling drive units are separate from the indexing drive units, thus adding to the overall complexity of the turret assembly. 
     Smith, U.S. Pat. No. 4,656,708, owned by the same assignee as the present invention, discloses the use of an indexing turret assembly utilizing a single drive motor to provide angular rotation of the turret plate for indexing, as well as for providing the drive to the live tooling mounted on the turret. Hydraulic pressure is used to disengage the turret plate and allow the turret plate to rotate with respect to the rest of the turret. A pneumatic clutch can then be engaged to rotate the turret plate with the single drive motor until the desired tool is indexed. The turret plate is then reengaged with the turret and the clutch disengaged to allow the single drive motor to drive the live tooling. 
     Link, U.S. Pat. No. 5,490,307, also discloses an indexing turret assembly utilizing a single drive motor for both indexing the turret and driving the live tooling. As with Smith, hydraulic pressure is used to disengage the turret plate and allow the turret plate to rotate with respect to the rest of the turret. The single drive motor is then used to rotate the turret plate until the desired tool is indexed. However, when the turret plate is reengaged with the turret, the drive to the turret plate automatically disengages so that the single drive motor can then be used to drive the live tooling. 
     Hafla, U.S. Pat. No. 4,847,960 also discloses an indexing turret assembly utilizing a single drive motor for both indexing the turret and driving the live tooling. Hafla does not disengage the turret plate from the turret to index the desired tool, but uses a disengageable planetary gear arranged with the live tool bevel drive gear to index the turret. 
     In Smith, Link and Hafla, the single live tool bevel drive gear is always engaged with all live tooling installed in the turret plate. Thus, where more than one live tool is installed in the turret plate, all live tools installed in the turret plate will be driven when any live tool is driven. There is a substantial loss of power in driving all live tools simultaneously when it is necessary to drive only the live tool indexed to perform an operation on a workpiece. This can require a higher capacity drive unit than would otherwise be required if only one live tool is driven at a single time or can result in insufficient power being available to properly drive the live tool performing an operation. None of Smith, Link or Hafla allows the selective driving of any single one of a plurality of live tools installed at a given time. 
     SUMMARY OF THE INVENTION 
     The present invention provides a turret assembly including a rotatable indexable turret tooling plate having mounted thereon stationary as well as live tooling and wherein a single drive motor is utilized in order to perform indexing (angular rotation of the turret tooling plate) as well as to drive the live tooling. A plurality of live tools can be simultaneously mounted on the turret tooling plate and the single drive motor is selectively engageable with each of the live tools so that only one of the plurality of live tools is driven at a given time. The selective live tool drive train includes an axially movable drive shaft and bevel drive gear for selectively engaging the driven bevel gear of the desired live tool. The axially movable shaft assembly includes a mechanism for adjusting the backlash between the driving and driven bevel gears when these gears are engaged with one another. The turret assembly further includes a clutch for selectively engaging the single drive motor to index the turret tooling plate and an encoder mechanism activated during the indexing operation in order to allow precise tracking of the turret tooling plate during the rotation thereof. A torque limiter is provided in the indexing drive train to disengage the indexing drive in the event of a torque overload occurring during indexing, such as may occur if the turret tooling plate or a tool mounted thereon strikes another object (workpiece, other turret, etc.). The drive motor is variable speed and reversible in order to allow bi-directional indexing following the shortest path and further allowing the live tooling to be bi-directionally driven at variable speeds. 
     It is therefore an object of the present invention to provide an indexable turret assembly capable of supporting stationary as well as live tooling. 
     It is also an object of the present invention to provide a turret assembly having an indexable turret tooling plate capable of supporting live tooling and having a single drive unit responsible for driving the live tooling as well as for causing angular displacement of the turret tooling plate during indexing. 
     It is another object of the present invention to provide a turret assembly having a live tool drive train that is engageable to selectively drive only a single one of a plurality of live tools mounted on the turret tooling plate. 
     It is another object of the present invention to provide a turret assembly having a selective live tool drive train that includes an axially movable drive shaft and bevel drive gear for selectively engaging the driven bevel gear of the desired live tool and wherein the axially movable shaft assembly includes a mechanism for adjusting the backlash between the driving and driven bevel gears when these gears are engaged with one another. 
     It is another object of the present invention to provide a turret assembly that includes a clutch for selectively engaging the single drive motor to index the turret tooling plate. 
     It is another object of the present invention to provide a turret which includes a torque limiter in the indexing drive train to disengage the indexing drive in the event of a torque overload occurring during indexing, such as may occur if the turret tooling plate or a tool mounted thereon strikes another object. 
     It is another object of the present invention to provide an indexable turret assembly including a variable speed reversible motor drive unit allowing bi-directional indexing following the shortest path and further including reversible bi-directionally driven live tooling. 
     It is another object of the present invention to provide a turret assembly having an indexable turret tooling plate and encoder mechanism for accurately tracking angular displacement of the turret tooling plate during indexing thereof. 
    
    
     The foregoing and other objects, features, characteristics and advantages of the present invention as well as the methods of operation and functions of the related elements of structure, and the combination of parts and economies of manufacture, will be apparent from the following detailed description and the appended claims, taken in connection with the accompanying drawings, all of which form a part of the specification, wherein like reference numerals designate corresponding parts in the various figures. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevational view of the indexing tool turret of the present invention; 
     FIG. 2 is a partial sectional view of the indexing tool turret of the present invention showing the tooling turret in an engaged position; 
     FIG. 3 is a partial sectional view of the indexing tool turret of the present invention showing the tooling turret in a retracted position; 
     FIG. 4 is a detailed sectional view of the tool driveshaft retracting mechanism of the present invention; 
     FIG. 5 is an end elevational view of the tool driveshaft retracting mechanism of the present invention; 
     FIG. 6 is a detailed side elevational view of the torque limiting mechanism of the present invention; 
     FIG. 7 is a detailed sectional view of the tooling plate lifting mechanism of the present invention; and 
     FIG. 8 is a sectional view of the tooling plate lifting mechanism of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As can be seen in FIGS. 1,  2  and  3 , an indexing tool turret according to the present invention is generally indicated at  10 . The tool turret  10  includes a drive unit  12  mounted to a tool turret housing  14 . In the preferred embodiment, the drive unit  12  is a variable speed, reversible electrical spindle motor, but other conventional types of drive units, including hydraulic and pneumatic units can be used. The drive unit  12  includes a drive shaft  16  conventionally connected to an input shaft  18  of a clutch mechanism  20 . Clutch mechanism  20  also includes an output shaft  22 . The clutch mechanism  20  is of a pneumatic type. The clutch mechanism  20  is available as model no. 5H20P from Horton Industrial Products, Inc. of Minneapolis, Minn. Other types of alternative clutch mechanisms can also be utilized. 
     The output shaft  22  of the clutch mechanism  20  is conventionally connected to an input shaft  24  of a speed reduction mechanism  26 . A housing  28  of the speed reduction mechanism  26  is attached to the tool turret housing  14 . The speed reduction mechanism  26  also includes an output shaft  30 . The speed reduction mechanism is available as model no. M03 from the Mectrol Corporation of Salem, N.H. Other types of alternative speed reduction mechanisms can also be utilized. 
     The output shaft  30  of the speed reduction mechanism  26  is conventionally connected to an input side  32  of a torque limiting mechanism  34 . A drive gear  36  is conventionally attached to a housing  38  of torque limiting mechanism  34 . The torque limiting mechanism  34  is available as model no. SKL-75 from Gam/Jakob Enterprises of Chicago, Ill. Other types of alternative torque limiting mechanisms can also be utilized. 
     Drive gear  36  is operatively engaged with a drive gear  40  conventionally attached to an index shaft  42  connected to tooling plate  44 . In the preferred embodiment, the gear engages keyed slots on the index shaft  42  and is retained by a nut engaging a threaded portion of the index shaft. Tooling plate  44  includes a plurality of tool stations  46  for mounting tools  48 . The tools  48  can be stationary or live, of the customary types. As seen in FIG. 2, the tool  48  mounted in the lower tool station  46  is of a live type and can be utilized for drilling operations. Tool  48  includes a bevel drive gear  50  for positioning in bore  52  of the lower tool station  46 . Index shaft  42  and tooling plate  44  are conventionally rotationally mounted on a hub  60  of tool turret housing  14  to rotate about an axis  62 . In the preferred embodiment, bearings or bushings are used to rotationally mount tooling plate  44  on hub  60 . 
     A lifting mechanism, discussed below and shown in FIG. 7 but not FIG. 2, is connected to the tooling plate  44  to raise the tooling plate from the lowered locked index position seen in FIG. 2 to a raised rotatable position (i.e., toward the right along axis  62 , as seen in FIG. 3) during indexing of the tooling plate  44 . Drive gear  40  is wider than drive gear  36  so that even when the tooling plate  44  is in the raised rotatable position, the proper mesh engagement between the two drive gears is maintained. 
     A drive gear  70  is conventionally attached to input shaft  18  of clutch mechanism  20 . Drive gear  70  is operatively engaged with an idler gear  72  rotationally attached in a conventional manner to turret housing  14 . Idler gear  72  is operatively engaged with a tool driveshaft gear  74  attached to tool driveshaft  76 . Tool driveshaft  76  is rotationally mounted in a bore  78  in hub  60 . In the preferred embodiment, bearings or bushings are used to rotationally mount driveshaft  76  in bore  78 . A bevel drive gear  80  is conventionally attached to an end  82  of tool driveshaft  76  and is adapted for operative engagement with bevel drive gear  50  of live tool  48 . In the preferred embodiment, bevel drive gear  80  engages a keyed slot on driveshaft  76  and is retained by a nut engaging a threaded portion of the driveshaft. 
     A tool driveshaft retracting mechanism, generally indicated at  100 , is attached to an end  84  of tool driveshaft  76 . Tool driveshaft retracting mechanism  100  is adapted to axially move tool driveshaft  76  in bore  78  from an engaged position (to the right, as seen in FIG.  2 ), to a retracted position (to the left, as seen in FIG.  3 ). In the engaged position, the bevel drive gear  80  is operatively engaged with live tool drive gear  50 . In the retracted position, the bevel drive gear  80  is disengaged from live tool drive gear  50 . Drive gear  74  is wider than idler gear  72  so that the proper mesh engagement between the two gears is maintained regardless of whether the tool driveshaft  76  (and thus drive gear  74 ) is in the engaged position or the retracted position. 
     As can be seen in FIG. 4, a housing  102  of driveshaft retracting mechanism  100  is mounted to the turret housing  14  by a plurality of screws  104  passing through a plurality of bores  106 . Housing  102  includes an interior bore  108  which is concentric with a stepped bore  110  in turret housing  14  when housing  102  is mounted to turret housing  14 . Although positioning bore  108  directly in the turret housing  14  is presently the preferred embodiment, the bore could also be positioned in a replaceable sleeve mounted to housing  14 . A piston  111  adapted for sliding and rotating movement in bores  108  and  110  is disposed in the bores. Seal  116  disposed in groove  118  maintains a sealing relationship between the housing  102  and turret housing  14  and between the housings and the piston  111 . Seals  112 ,  120  and  124  disposed in grooves  114 ,  122  and  126 , respectively, maintain a seal relationship between the housings and the piston  111 . 
     Piston  111  includes an interior bore  130 , a lip  132  at one end of the bore and a threaded portion  134  of interior bore  130 . A set of angular contact bearings  136  are disposed in the piston interior bore  130  seated against lip  132  for rotationally supporting drive shaft  76 . A seal/spacer  138  disposed between bearings  136 , lip  132  and driveshaft  76 , shields contaminants from the interior of retracting mechanism  100  and provides axial clearance between the drive gear  74  and the housing  14 . A nut  140  engages threaded portion  142  of driveshaft  76  to secure the driveshaft  76  to the retracting mechanism and to secure inner races of the bearings  136  to the piston  111 . 
     An internal nut  144  includes an externally threaded portion  146  for engaging threaded portion  134  of piston  111  to secure outer races of the bearings  136  to the piston  111 . The interior nut also includes a recessed interior portion  148  for providing clearance between the interior nut  144  and the nut  140 /driveshaft  76  and a hexagonally shaped bore  150  for engagement with a hex tool (not shown). The hex tool can thus be used to removably install the interior nut  144  in piston  111  as well as to rotate piston  111  after the nut  144  is tightened against the outer races of the bearings  136 . 
     A threaded collar  152  engages an externally threaded portion  154  of piston  111 . A plurality of shouldered screws  156  disposed in bores  158  of collar  152  are used to retain the collar  152  to the housing  102  and prevent rotation of the collar  152 . A compression spring  160  is disposed between each screw  156  and the collar  152  to bias the collar  152  against the housing  102  while still allowing a predetermined range of axial motion of the collar  152  and thus, the driveshaft  76  and bevel drive gear  80 . A plurality of adjustable threaded set screws  174  are disposed in a plurality of threaded radial bores  176  in the collar  152  (shown in phantom in FIG. 5) for engaging piston  111  and locking the piston  111  with respect to the collar  152 . In the preferred embodiment, the setscrews are made of a softer material than the piston so as not to damage the piston surface. 
     An engagement sensor  170  is attached to the collar  152  and is adapted for sensing its proximity to a portion of the turret housing  14  to sense when the bevel drive gear  80  is in the engaged position with bevel drive gear  50 . A retract sensor  172  is attached to the turret housing  14  and adapted for sensing its proximity to the collar  152  to sense when the bevel drive gear  80  is in the retracted position and disengaged with bevel drive gear  50 . Both sensors are conventionally adjustable to adjust their sensing positions. In the preferred embodiment, proximity sensors are used which do not have moving parts, although other types of conventional sensors can be used. 
     The engagement of piston  111  with bores  108  and  110  creates two hydraulic chambers between the piston  111  and the bores  108  and  110 . The first chamber  180  is created on one side of seal  120  and the second chamber  182  is created on the other side of seal  120 . Each of chambers  180  and  182  is operatively connected to a hydraulic supply, as is conventionally available on turret utilizing machine tools. Supplying pressurized hydraulic fluid to chamber  180  forces the piston  111  and thus the bevel drive gear  80 , to move toward the retracted position. The travel of the piston  111  can be limited by the contact of the step  184  in the outer surface of the piston  111  with the surface of housing  102 . Alternatively, one or more adjustable shoulderless limit screws can be provided to engage the collar  152  and the housing  102 , similarly to screws  156 , to limit travel of the piston in toward the retracted position. Other known types of travel limiters, adjustable or not, can also be provided. 
     Removing the supply of pressurized hydraulic fluid from either chamber causes the piston  111 , and thus the bevel drive gear  80 , to move toward the engaged position because of the biasing force supplied by the springs  160 . Supplying pressurized hydraulic fluid to chamber  182  will supply additional biasing force to the piston  111 , and thus the bevel drive gear  80 , toward the engaged position. This additional biasing force is utilized to maintain the bevel drive gear  80  in proper driving engagement with bevel drive gear  50  and to overcome the natural driving forces which would otherwise act to force the bevel gears apart when the live tool  48  is performing a machining operation. 
     Alternatively, other types of mechanical, hydraulic, pneumatic, electrical or electromechanical types of actuators can be attached to the piston  111  or other component in the axially movable assembly and utilized to provide movement and biasing force in either direction. FIG. 8 shows such an embodiment where an actuator  195  is mounted between the turret housing  14  and the collar  152  to axially move and bias the driveshaft  76 . 
     The travel of piston  111  toward the engaged position is limited by the contact of collar  152  with housing  102 . The engagement travel limit is adjustable due to the threaded engagement of piston  111  with collar  152 . The setscrews  174  are first backed out of engagement with piston  111 . A hex tool is then inserted into hex bore  150  of inner nut  144 . Since the force required to loosen the inner nut  144  with respect to piston  111  is generally greater than the force required to rotate the piston  111  with respect to the housing  102 , turret housing  14 , etc., the hex tool can be generally used to rotate the piston in either direction. Because of the threaded engagement of the piston  111  with respect to the collar  152 , rotation of the piston  111  with respect to the collar  152  causes the piston  111  to move axially with respect to the collar  152 . The direction of axial movement will depend on the direction of rotation and whether the threaded engagement uses a right-hand or left-hand thread. In the preferred embodiment, an M50×1 mm thread is used to provide for fine axial adjustability of the piston  111 . Different threads can also be utilized. 
     The piston  111  is rotated and the piston correspondingly moved axially until the desired backlash is obtained between the bevel drive gear  80  and the bevel drive gear  50  when the two gears are in the engaged position. When the desired backlash is obtained, which can be determined by conventional methods, the setscrews  174  are then retightened against the piston  111  to maintain that setting. The backlash can also be adjusted by removing the screws  156  and springs  160  and rotating the collar  152  with respect to the piston  111 . After the desired backlash is obtained, the setscrews can be tightened down and the collar  152  aligned with the housing  102  so that the screws  156  and springs  160  can be reinstalled. If necessary, the sensor  170  is repositionable with respect to the collar  152 . 
     The indexing tool turret of the present invention operates as follows. To index the tool plate, index shaft  42  and tooling plate  44  are lifted from the position shown in FIG. 2 to the position shown in FIG. 3 by the lifting mechanism. The driveshaft  76  and bevel drive gear  80  are retracted by the retracting mechanism  100  to the position shown in FIG.  3 . When the retract sensor  172  senses that the driveshaft is retracted, the clutch mechanism  20  is engaged (see FIG. 3) and the drive unit  12  started to transmit torque through the speed reducing mechanism  26  to the torque limiting mechanism  34 , which in turn rotates the tooling plate  44  through the drive gears  36  and  40  and index shaft  42 . The tooling plate is then rotated until the desired tool station is properly indexed, as is sensed by conventional encoding mechanisms. The variable speed and reversible drive unit  12  allows bi-directional indexing following the shortest path and further allows the live tooling to be bi-directionally driven at variable speeds. 
     The speed reducing mechanism  26  operates in conjunction with the various gear ratios present in the indexing drive train to reduce the speed at which the tooling plate  44  indexes in comparison to the speed of rotation of the live tool  48 . In the preferred embodiment, the final drive ratio through the indexing drive train to the tooling plate  44  is approximately 22/1, whereas the final drive ratio through the live tool drive train to the live tool  48  is approximately 1/1. 
     The torque limiting mechanism  34  ratchets when a torque overload is encountered, such as when the tooling plate strikes an object while indexing (crashes) or when the indexed tool has not been properly retracted from the workpiece prior to indexing. The ratcheting operates to limit the torque transmitted from the drive unit  12  to the tooling plate  44  (and vice-versa). The operation of the torque limiting mechanism  34  when a torque overload is encountered is such that a plate  39  of the torque limiting mechanism is pushed outward from the mechanism (to the right in FIG.  6 ). A proximity sensor  190  is mounted to the turret housing  14  and positioned with respect to the torque limiting mechanism  34  so as to sense when the plate  39  has been pushed outward, indicating that a torque overload has been encountered. Upon sensing such an occurrence, the proximity sensor  190  sends a signal to shut down the machine tool until the cause of the torque overload is determined and rectified. The tripping of the torque limiting mechanism and the shutting down of the machine in response to the trip signal helps to prevent further damage to the drive unit, drive train, tooling plate, and tools. The possibility of crashing is increased in a machine tool having more than one tool turret, so this feature is especially desirable in such machines. 
     When the tooling plate is properly indexed, it is lowered by the lifting mechanism and locked in place. The clutch mechanism  20  is then operated to disengage the drive unit from the tooling plate  44  (see FIG.  2 ). The pressurized hydraulic fluid supply is then removed from chamber  180  so that the biasing force from springs  160  move the driveshaft  76  and bevel drive gear  80  toward the engaged position. The springs are designed to have less biasing force than the hydraulic locking mechanism. Therefore, the use of the springs as opposed to the hydraulic mechanism to perform the initial engagement of the bevel drive gears is preferred, because it limits excessive engaging force which might damage the bevel drive gears or other components. 
     The engage sensor  170  then determines if the bevel drive gear  80  has properly engaged the bevel drive gear  50 . If not, the drive unit is engaged to slowly turn the bevel drive gear  80  through the gears  70 ,  72  and  74  and driveshaft  76  until the engage sensor determines that the bevel drive gear  80  has properly engaged the bevel drive gear  50 , whereupon, the drive unit  12  is shut down in response to the signal from the engage sensor  170 . Once the engage sensor  170  determines that the bevel drive gears are properly engaged and the drive unit is shut down, pressurized hydraulic fluid supply is connected to the chamber  182  to bias the piston  111  toward the engaged position to maintain the engagement of the bevel drive gears during machining operations. At this point the drive unit can be started to drive the live tooling. 
     In the preferred method, the above described operations are automatically sequentially controlled as predetermined and in response to the discussed signals by a computer, machine controller or other logic device. The operations can also be manually controlled in the desired sequence and, if desired, in response to the discussed signals and provisions can be made for manually overriding the automatic controls. 
     A tool turret lifting mechanism, generally indicated at  200 , is disclosed in FIG.  7 . Index shaft  42  is rotatably mounted on hub  60  by needle bearings  302  and seal  304  provides a sealing arrangement between the index shaft  42  and hub  60 . Retaining rings  303  retain the bearings  302  in place in the index shaft  42 . Driveshaft  76  is rotatably mounted in hub  60  by needle bearings  306  and seal  308  provides a sealing arrangement between the driveshaft  76  and hub  60 . Turret housing  14  includes a stepped bore  310 , in which is disposed an axially movable piston  312 . Although positioning bore  310  directly in the turret housing  14  is presently the preferred embodiment, the bore could also be positioned in a replaceable sleeve mounted to housing  14 . 
     An inner face gear  314  is mounted to turret housing  14  by a plurality of screws  316  and encloses bore  310  with respect to piston  312 . Seals  318 ,  320 ,  322  and  324  provide a sealing arrangement between housing  14 , inner face gear  314  and piston  312 . Index shaft  42  is rotatably supported with respect to piston  312  by needle bearings  326  and  328 . Needle bearings  330  and  332  and thrust washers  334 ,  336  and  338  mounted between the index shaft  42 , piston  312  and drive gear  40  provide axial thrust support to tooling plate  44  mounted to index shaft  42 . An outer face gear  340  is mounted to tooling plate  44  by a plurality of screws  342  and adapted to indexingly engage inner face gear  314 . 
     A coolant housing  344  is mounted to the tooling plate  44  by a plurality of screws  346  and includes a plurality of coolant flow ports  348 . Generally, a coolant flow port is provided for each tool station  46  and provides for coolant flow to the indexed tool. A seal  350  provides a sealing arrangement between the coolant housing  344  and inner face gear  314 . A coolant supply port  352  is connected to a coolant source and is adapted to provide coolant to the indexed coolant flow port. Coolant supply port  352  includes a spring-loaded sealing tube  354  for providing a sealing relationship between coolant supply port  352  and the indexed coolant flow port  348 . 
     The mating relationship between the turret housing  14 , inner face gear  314  and piston  312  creates two chambers  360  and  362 . The first chamber  360  is created on one side of seal  322  and the second chamber  362  is created on the other side of seal  322 . Each of chambers  360  and  362  is operatively connected to a hydraulic supply, as is conventionally available on turret utilizing machine tools. Supplying pressurized hydraulic fluid to chamber  360  forces the piston  312 , and thus the tooling plate  44 , to move toward the retracted (lowered) position. Supplying pressurized hydraulic fluid to chamber  362  forces the piston  312 , and thus the tooling plate  44 , to move toward the disengaged (raised) position. The surface area of the piston perpendicular to axis  62  is greater in chamber  360  than in chamber  362 . Thus, the force that can be exerted on the piston  312  by the supply of pressurized hydraulic fluid to the chambers is greater toward the retracted position than toward the disengaged position, all other things being equal. 
     To raise the tooling plate  44 , the supply of pressurized hydraulic fluid is removed from chamber  360  and supplied to chamber  362 , thereby moving the piston  312 , and thus tooling plate  44 , to the right as seen in FIG.  7 . This also disengages the face gears  314  and  340 , thereby allowing rotation of the tooling plate  44 . The tooling plate can then be indexed (rotated) as discussed above until the desired index is achieved. A conventional encoding mechanism is used to determine that the proper indexing has been achieved. 
     To lower the tooling plate  44 , the supply of pressurized hydraulic fluid is removed from chamber  362  and supplied to chamber  360 , thereby moving the piston  312 , and thus tooling plate  44 , to the left as seen in FIG.  7 . This also reengages the face gears  314  and  340 , thereby preventing further rotation of the tooling plate  44  until it is raised again. The continuing supply of pressurized hydraulic fluid to chamber  360  retains and locks the tooling plate  44  in the lowered position. If desired, the pressurized hydraulic fluid supplied to chamber  360  to lower the tooling plate can be initially supplied at a lower pressure to more gently lower the tooling plate and reengage the face gears. Then, the pressure of the hydraulic fluid can be increased to more securely lock the tooling plate in the lowered position. 
     Other known lifting and locking mechanisms can also be utilized with the present invention, such as the mechanism disclosed in Smith, U.S. Pat. No. 4,656,708, owned by the same assignee as the present invention and incorporated herein by reference. 
     While this invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that it is capable of further modifications and is not to be limited to the disclosed embodiment, and this application is intended to cover any variations, uses, equivalent arrangements or adaptations of the invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice in the art to which the invention pertains, and as may be applied to the essential features hereinbefore set forth and followed in the spirit and scope of the appended claims.