Typical quick-change toolholders have separate devices to align the toolholder in the spindle, to retain the toolholder in the spindle and to drive the toolholder. One example of a quick-change toolholder is disclosed in United States Patent No.

4,834,596 (the'596 holder) which is assigned to the assignee of the present invention.

The'596 holder aligns the toolholder in the spindle and drives the toolholder through the interaction of a longitudinally extending keyway or driveslot in the spindle that receives a Woodruff key mounted to the toolholder.

In operation, the toolholder is inserted into the spindle with the Woodruff key being aligned and received within the keyway or driveslot. The toolholder is held in the spindle by an outer shell that is internally threaded to mate with exterior threads on the toolholder. The'596 holder is a quick-change toolholder because the external threads are threaded segments that are received within windows in the outer shell. The windows are aligned with the threaded segments so that the toolholder can be fully inserted into the spindle and then the sleeve can be rotated about 1/8 turn to lock the toolholder into the spindle.

One disadvantage with this type of toolholder is that the Woodruff key is prone to damage through rough handling. Once damaged, it is difficult to reinsert the toolholder and the toolholder can be misaligned in the spindle. As a result of this damage, the Woodruff key and keyway must be checked regularly and maintained in order to insure proper registry in the spindle. Another disadvantage is the cost of manufacturing the'596 holder. The keyway and Woodruff key must be carefully

machined and aligned. The sleeve and thread segment must be properly aligned, all of which adds to the cost of the toolholder.

Another example of a toolholder is illustrated in United States Patent No.

5,201,620, (the'620 toolholder). In this toolholder, a locating base member is mounted in the spindle. The locating base member has a nose that mates with the toolholder to retain and align the toolholder in the spindle. A spring loaded sleeve having integral driving dogs is mounted to the toolholder. The dogs are received within openings in the face of the spindle and drive the toolholder. To fit and secure the toolholder in the spindle, the toolholder is inserted into the spindle bore and the end of the toolholder is oriented to mate with the nose of the locating base member.

The base member has a T-shaped nose that is received within slots in the end of the toolholder. Rotation of the toolholder locks the nose into the end of the toolholder and rotates the dogs into the openings.

One difficulty with the'620 toolholder is the damage that can occur due to rough handling. The end of the toolholder is exposed and if damaged will effect alignment and retention. Additionally, the driving dogs are exposed and if damaged can prevent proper driving of the toolholder. The end of the toolholder is also exposed to dirt and grime which is common in the working environment of this tool. If the end becomes clogged it can effect alignment and retention. The openings are also exposed and if they become clogged can result in an inability to retain and align the toolholder.

Another difficulty with the'620 toolholder is the complexity of the toolholder assembly. The spindle has to be machined deep in the spindle bore to receive the attaching means of the base member. The base member must be machined precisely to be received within the spindle bore and the base member must be precisely installed in the spindle bore. The end of the toolholder must be carefully machined to properly receive the nose and the openings in the end of the spindle must be carefully machined to receive the driving dogs in the sleeve. The sleeve itself has to be carefully positioned on the toolholder and timed to ensure that the dogs spring into the openings when the toolholder is rotated.

Another problem with some conventional toolholders is their large diameters.

In many operations, there is a need to quickly change a tool in a multi-spindle machine. A multi-spindle machine performs several simultaneous operations and commonly has a plurality of closely located spindle stations. Accordingly, the closer the spindles can be located to each other, the greater the number of tools which can be provided on a single machine head, and the closer each tool center can be located to each other. However, quick change toolholders have relatively large retention devices to retain the toolholder and can not be closely spaced which reduces the quantity of tools available on each machine and limits the types of operations performed.

Further, conventional toolholder assemblies receive the full torque from the machine spindle through the key or the drive dogs. Only one corner of the key or drive dog takes all the rotational torque. As there is a tolerance between the key and slot or dog and slot assemblies, the torque is transferred through only a portion of the key or dog. Accordingly, the key or dog assemblies are prone to further damage and wear which decreases the concentric alignment between the toolholder and spindle. Thus, the operational tolerance that the tool can maintain is reduced.

SUMMARY OF THE INVENTION The present invention overcomes the problems encountered with conventional quick change toolholders by providing a quick change toolholder having a unique, low maintenance, inexpensive aligning, retaining and driving system which distributes forces evenly about the tool holder. All of this is accomplished by a single aligning retaining and driving system.

The toolholder assembly of the present invention includes a toolholder, a moveable sleeve mounted on the machine spindle and multiuse connectors, preferably balls, which interconnect through the spindle into the holder. The machine spindle includes an axial bore at its forward end to receive the toolholder and a shank at the opposite end, which axially projects into a bore of a powered machine such as a multi-

spindle machine. In the preferred embodiment, the forward end of the machine spindle defines a conical bearing surface adapted to receive a centering cone on the toolholder.

The centering cone is arranged forwardly of the toolholder shank and is in registry with the bearing surface for facilitating axial self-alignment of the toolholder and spindle.

A spring biased locking and unlocking shell is mounted for axial movement along the power-driven spindle. The shell interacts with a plurality of drive balls, which are movably retained in the machine spindle. It should be understood that connectors other than balls could be used, but balls are preferred. Other connectors could include roller bearings, pins of various geometric shapes, oblong members, etc.

The balls are supported in openings in the spindle, which allow the balls to extend into the bore of the spindle without going completely through the spindle wall. Each of the drive balls is adapted to engage a corresponding pocket in the toolholder to align the toolholder, to lock the toolholder in the adapter, and to drive the toolholder. The drive balls and pockets provide a plurality of locations to evenly transfer and distribute the torque a full 360° about the power-driven spindle and the toolholder The shell is spring biased and therefore maintains the drive balls in engagement with the toolholder and locks with an audible"click". To release the toolholder from the machine spindle, the shell is axially retracted against the spring along the machine spindle. The multipurpose balls are thereby allowed to move radially away from the axial centerline of the power-driven spindle and the toolholder is released.

Additionally, a chipguard can be used to engage the toolholder at its outer periphery to exclude chips, debris and lubricants from the interior of the shell, adaptor and the spindle.

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages of the present invention will be readily appreciated, as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein: Figure 1 is a side view of an assembled quick-change toolholder assembly of the present invention; Figure 2A is a side view of the machine spindle of the present invention; Figure 2B is a sectional view of the machine spindle of Figure 2A taken along line B-B; Figure 3A is a side view of the toolholder of the present invention; Figure 3B is a sectional view of the toolholder of Figure 3A taken along line A-A; Figure 4A is an end view of the locking/unlocking shell of the present invention; and Figure 4B is a sectional view of the locking/unlocking shell of figure 4A taken along line A-A.

Figure 5 is a perspective view of a toolholder showing a tool held within a collet.

Figure 6 illustrates several collets.

Figure 7 illustrates a rear coolant seal.

Figure 8 is a cutaway view of a pocket or ball spot in the toolholder.

Figure 9 is a cutaway view of a ball hole in the power-driven spindle.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A quick-change toolholder assembly 10 of the present invention is shown in Figure 1. As will be further described below the quick change toolholder assembly 10 generally includes a power-driven spindle 12 incorporated into a machine head, a toolholder 14, multiuse connectors, preferably balls 20, and a locking and unlocking shell 16.

As shown in figure 1, the assembly 10 includes the machine spindle 12 having a bore 36 for receipt of the toolholder 14. In operation the power-driven spindle 12 fits into a power-rotated machine. The narrow profile of this tool allows effective use in a multi-spindle machine. The power-driven spindle 12 includes a plurality of angularly located holes 18, which retain a plurality of multiuse connectors, preferably, drive balls 20. Each of the drive balls 20 are adapted to register in a plurality of corresponding pockets or ball spots 22 located in the toolholder 14.

The drive balls 20 are retained within the holes 18 by the locking shell 16 and by the configuration of the holes 18. The holes 18 have an inner diameter that is initially greater than the diameter of the maximum diameter of the balls but is reduced to a diameter which is less than the maximum diameter of the balls 20. This allows the balls to extend into the bore 13, but not fall through the holes 18. The locking shell 16 is axially retained to the power-driven spindle 12 by a first 24 and second 26 snap ring and is axially biased to the locked position by a coil spring 28. Additionally, an annular chip guard 30 is located to snugly engage the assembly 10 and a nut 32 is operative to retain a tool 31 and collet 33 within a collet bore 34, see Figures 5 and 6.

A rear coolant seal 35 is shown in Figures 1 and 7 for use with drill holder coolant applications.

In the preferred embodiment, the balls range in size from 6.5mm to 9mm. The different sizes of balls correspond to different spindle sizes. The 3/4 inch and a 1 1/16 inch spindles use a 6.5mm ball, the 5/8 inch spindle uses a 4.5mm ball and the 1 3/8 inch spindle uses a 9mm ball. Preferably, there are six balls 20 spaced about 60 degrees apart evenly around the inner diameter of the spindle 12, providing balanced driving torque.

The power-driven spindle 12 is shown in greater detail in figures 2A and 2B.

As illustrated, the power-driven spindle 12 does not require a longitudinal keyway to receive a Woodruff key normally mounted upon the toolholder. In the disclosed embodiment, the power-driven spindle 12 includes a conical recess 38 within its inner bore surface 36 at its forward end. The conical bearing surface opens forwardly and

outwardly. The included angle between opposite sides of the conical bearing surface will be discussed in greater detail below in relationship to the centering cone on the toolholder 14.

The power-driven spindle 12 further includes holes 18 located about the periphery of the power-driven spindle 12 to retain the drive balls 20 (Figure 1). The holes 18 have an initial uniform bore diameter 21 which terminates in a reduced diameter opening 23 so that the drive balls 20 can move toward the toolholder 14 and engage the pockets 22 without falling through the hole 18. In the preferred embodiment, the holes 18 are drilled with a tool having the shape of the hole formed on the tool. The uniform bore diameter is slightly larger than the diameter of the balls 20 and the opening in the floor has a diameter that is less than the diameter of the balls 20. In this way, the balls 20 can move within and protrude out of the hole 18, yet, not fall through the holes 18. Although one row of six equally spaced holes 18 are shown, one will realize that various ball quantities, ball sizes, rows and locations may be employed. Further, a pair of annular grooves 40 and 42 are formed in the outer surface of power-driven spindle 12 to receive snap rings 24 and 26 (Figure 1).

As shown in figures 3a, 3b, 5 and 6, the toolholder 14 has a collet chuck holder assembly for mounting tools such as a drill, a reamer or a counter boring tool within the collet bore 34. The collet 33 and nut 32 are shown in figure 6 with a drill 31. The completed assembly is shown in figure 5. It will be understood by those of ordinary skill in the art that any type of tool can be mounted to the toolholder. The tools are retained by nut 32 on one end and an adjustable stop 15 on the other end for adjusting the length of the colleted tool (see Figure 1). The toolholder 14 includes an annular body 40 which includes a centering cone 42. The centering cone 42 has the same included angle as the conical recess 38 and the two are configured to mate such that there is surface-to-surface contact as opposed to line contact. The preferred angle of the surface is a 50 degree included angle. In the preferred embodiment, the toolholder 14 is precision-ground and heat treated to 58 Rc and threaded on one end.

The pockets 22 are illustrated in figure 3A and 8. In the preferred embodiment, the pockets 22 are drilled to ensure that the balls 20, protruding from holes 18 in the spindle 12, make secure contact with the walls of pockets 22. In this way, there is very limited play in any direction between the holder 14 and the power-driven spindle 12.

Each ball receives the same torque since the torque is equally distributed. This distribution of forces reduces, if not eliminates, problems of spindle and toolholder breakage encountered with conventional toolholders and power-driven spindles.

It will be understood that the diameter and depth of pockets 22 will depend upon the diameter of the balls 20. The preferred diameter and depth receives the ball 20 and provides line contact about the wall of pockets 22 and the exposed portion of ball 20. The pockets 22 are uniformly formed with a tool having a cutting surface equal to the hole diameter and profiled to the shape of the pockets 22 shown in figure 8. The pockets 22 are equally spaced about the spindle 12. In the preferred embodiment, the pockets 22 are on 60° centers.

As shown in figures 4A and 4B, the locking shell 16 which traps the drive balls 20, is shown in greater detail. Shell 16 is slidably retained by the lock rings or snap rings 24 and 26. The rings 24,26 axially locate the shell 16 upon spindle 12 and further provide a fixed base for the spring 28. A spring seat 44 is provided in one end of the shell 16. The spring 28 is trapped between the snap ring 24 and the spring seat 44 to axially bias the shell 16 to the locked position and maintain the balls 18 in pockets 22. The cylindrical shell 16 includes an annular recess 42 to accept the drive balls 18 while allowing the balls 18 to disengage the pockets 22 when the toolholder 14 is to be removed.

Additionally, the plurality of pockets 22 and shell 16 provide locking engagement by seating the drive balls 20 with an audible"click". The"click"helps to confirm to the operator that the toolholder 14 is positively locked. The drive balls 20 operatively connect the spindle 12 to the toolholder 14 to transmit torque. Thus, when the shell 16 is in a locking position the drive balls 20 engage the pockets 22 and rotational motion of the spindle 12 is transferred to the toolholder 14 at a plurality of

locations. The drive balls 20 thus equally distribute the torque applied to the toolholder 14. The balls also align and retain the toolholder. In this way, the present invention eliminates the conventional assemblies having numerous separate devices for performing these functions and eliminates the problems associated with numerous separate devices such as high manufacturing costs, close tolerance requirements, high maintenance due to inadvertent damage, and the necessary transfer of torque through only one location.

To unlock the toolholder 14, the shell 16 is retracted and the annular recess 42 aligns with the balls 20 so that the balls 20 can be moved radially outward into the recess 42. The balls 20 are thus disengaged from pockets 22 and toolholder 14 is released from spindle 12.

Further, the assembly 10 preferably includes a chip guard 30 to exclude chips, debris and lubricants from the interior of the assembly 10.

With the present invention changes in tooling will take mere seconds as compared to minutes or hours for standard methods. Additionally, changes can be easily made by an operator using only one hand, even though a plurality of closely spaced spindle assemblies are provided.

The present invention has been described in an illustrative manner, and it is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation. Many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.