Rotary turret head apparatus

A rotary turret head apparatus for installing a fastener such as a rivet. The rotary turret head apparatus has a plurality of machining and fastener installation tools disposed perpendicular to the axis of rotation of the turret. The individual tools are independently powered and the entire turret head apparatus is fed toward the workpiece by a single actuator mechanism such as a roller screw or hydraulic cylinder thereby eliminating the need for a separate actuating mechanism for each tool and eliminating the need for engagement of each tool with a central actuating mechanism.

FIELD OF INVENTION
 The present invention relates to a rotary turret head apparatus, and more
 particularly to a rotary turret head apparatus suitable for use with
 automatic fastening tools subject to large forming forces.
 BACKGROUND OF THE INVENTION
 In a number of machine tool applications, multiple operations must be
 performed successively on a fixed workpiece at the same location. For
 example, the assembly of the exterior skin of an airplane fuselage may
 require drilling a hole, inserting a rivet into the hole, upsetting the
 rivet, and shaving the rivet head. Automatic fastening machines for
 performing these operations are well known. Such a machine utilizes a
 controlled transfer head that selectively positions various tools carried
 by the machine for sequential operation on a workpiece. Typically, the
 different tools in the transfer head are arranged in linear fashion. The
 linear carriage enables the tools to be indexed in a straight line into a
 working position aligned with a work axis that is disposed substantially
 perpendicular to the plane of the workpiece. A control system moves the
 tools into and out of alignment with the work axis depending on the
 required sequence for the manufacturing operation that is being performed.
 It is common to have separate actuators or feed mechanisms for each tool.
 The separate feed mechanisms drive the tool toward the workpiece after it
 has been aligned by the indexing mechanism. Also, certain tools such as
 drills require drive mechanisms for rotating the tool. Accordingly, the
 number and different types of mechanisms associated with indexing, feeding
 and rotating the tools presents a drawback to the linear carriage type
 systems.
 Another drawback to these type of systems is that it is difficult to
 retrofit the linear carriages of existing machines unless the existing
 machine has the same number of tool positions.
 As an alternative to having independent feed mechanisms for each tool, a
 centralized feed mechanism capable of engaging with the individual tools
 can be provided. However, the feed mechanism should be direct coupled to
 the tools to prevent backlash or chatter, and therefore the single feed
 mechanism introduces complexity due to the fact that each tool has to be
 separately brought into alignment and engagement with the central feed
 mechanism.
 There have been tool changers and other machine tool devices that dispose
 machine tools about a turret perpendicular to the axis of rotation of the
 turret such as the devices disclosed in U.S. Pat. Nos. 3,296,896;
 3,975,109; and, 4,679,276. However, these patents generally disclose
 turrets designed specifically for cutting tools. The purpose of the
 turrets disclosed in these patents is to provide tool changers that
 separately and individually engage different cutting tools with a central
 drive. Accordingly, the systems include clutches and transmissions for
 engaging the tools and for driving the tools at different speeds. These
 systems suffer from some of the same drawbacks discussed above such as the
 complexity associated with having to separately and individually engage
 numerous tools with a central drive. Also, these patents address a
 different problem, namely using a single drive to rotate tools over wide
 ranges of speeds. Furthermore, none of the prior patents is suitable for
 use in riveting operations where forming forces can reach into the tens of
 thousands of pounds.
 Accordingly, what is needed is an indexing turret head apparatus that is
 capable of indexing several tools into a single position relative to a
 workpiece, that has a single actuator device for all of the tools, that
 does not require separate engagement of the actuator device with the
 tools, and that is suitable for use with fastener installation tools for
 installing fasteners such as rivets where the forming forces for upsetting
 the rivet are typically in the range of tens of thousands of pounds.
 SUMMARY OF THE INVENTION
 The present invention meets the above described need by providing a
 rotating turret head apparatus that has a plurality of tools mounted
 perpendicular to the axis of rotation of the turret, that has a single
 actuating mechanism for feeding the tools to a workpiece, and that is
 suitable for use in installing fasteners where forming forces are in the
 tens of thousands of pounds.
 By mounting the tools perpendicular to the axis of rotation of the turret,
 a single actuator can be used to feed all of the tools toward the
 workpiece without the need for separate engagement of a central actuator
 with each tool. The tools are disposed around the periphery of the turret
 with sufficient space between adjacent tools such that there is sufficient
 clearance between the inactive tools and the workpiece to avoid
 obstruction or damage to the workpiece. Also, because the tools do not
 have individual actuators and do not have to individually engage with a
 central actuator, the mounting of the tools is simplified greatly. Each
 tool can be removably mounted to the turret and can be independently
 powered by its own source. Accordingly, the individual sources can operate
 at different frequencies and rpm's and can be powered continuously or
 powered intermittently depending on the specific application. Also, there
 can be a greater number of tool mounting positions on the turret than
 there are tools in order to provide for future expansion. In addition,
 because the only requirement is mounting the tools to the turret, it is
 relatively easy to substitute different types of tools into the system
 with little or no modification.
 Accordingly, the turret head apparatus has a turret with an axis of
 rotation and a plurality of tool mounting positions disposed around the
 turret. A plurality of fastener installation and machining tools are
 removably attached to the tool mounting positions on the turret and are
 disposed substantially perpendicular to the axis of rotation of the
 turret.
 A drive system rotates the turret to index the tools into a working
 position aligned with the work axis. The turret is preferably connected to
 a shaft that is mounted on a set of bearings disposed inside a frame. The
 frame supports both the turret and the drive system. When the tool
 attached to the turret has to be fed toward the workpiece, the entire
 frame is moved by an actuating mechanism. The actuating mechanism is
 capable of moving the frame to bring the fastener installation tool into
 engagement with a cooperating fastener tool such as an opposing ram to
 install a fastener.
 A guide structure such as a set of guide rails is disposed about the frame
 such that the frame is maintained in substantial alignment with the
 workpiece as it travels toward and away from the workpiece.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
 FIG. 1 shows one form of an illustrative automatic fastening machine to
 which the present invention is applicable, and the machine is an automatic
 drilling and riveting machine generally designated 10. Machine 10 includes
 a generally C-shaped frame 12 supported on a surface 14, such as the floor
 of a factory. A workpiece 16 comprising two metal worksheets 18, 20 to be
 joined is introduced into the C-shaped jaws of the machine 10 and clamped
 together by pneumatic and/or hydraulic pressure in a known manner. This
 pressure holds sheets 18, 20 during the drilling operation, assuring exact
 hole positioning. Typically, the first operation performed by machine 10
 on workpiece 16 is drilling a hole at a location where the center of the
 hole is on what is known in the art as the work point or centerline that
 is disposed perpendicular to the plane of the surface of the workpiece 16
 surrounding the hole. A tool 22 (shown in FIG. 3) is provided for
 inspecting the hole. A fastener 25 (shown in FIG. 3) is inserted in the
 hole and squeezed or upset therein by hydraulic cylinder or roller screw
 force applied from above by a bucking ram 26 and below by an opposing ram
 28.
 Machine 10 includes an upper head assembly 32 and a lower head assembly 34,
 both carried by frame 12. Both upper and lower assemblies 32, and 34,
 respectively, are mounted on frame 12 so that a work centerline alignment
 is maintained between their respective tooling, i.e., the lower ram 28 and
 selectively an upper head tool such as the bucking ram 26.
 Referring to FIG. 2, a turret head apparatus 40 includes a rotary turret 43
 having a plurality of tool mounting positions 46 disposed around a side 49
 of the turret 43. The turret 43 has opposite sides 49 and 51, and a
 circular periphery 54. The turret 43 is disc-shaped, rigid, and capable of
 supporting a plurality of tools 57. The tools 57 are preferably mounted to
 the one side 49 of the turret 43.
 Turning to FIG. 3, typically the tools for installing a fastener can
 include a drill 60, the hole inspection tool 22, the bucking ram 26, and a
 shaving tool 66. A rivet or slug 25 is held in fingers 27 carried by
 bucking ram or tool 26 in a known manner. Each of these tools performs its
 function in sequence. First, the drill 60 provides a hole through the two
 metal worksheets 18, 20. Second, the hole inspection tool 22 is brought
 into the workpiece 16 to inspect the hole. Next, the bucking ram 26
 inserts a rivet 25 into the opening, and then upsets the rivet 25 through
 its action against the opposing ram 28 (shown in FIG. 1). Finally, the
 shaving tool 66 shaves the rivet 25.
 Returning to FIG. 2, a drive system 70 for rotating turret 43 includes a
 shaft 71 that is attached to the turret 43, and is capable of rotating on
 a set of bearings 73 (shown in FIG. 5) that are disposed inside a pair of
 openings 75 in a frame 76. The shaft 71 is preferably constructed of a
 solid, rigid material.
 The shaft 71 is rotated by a speed reducer 82. The speed reducer 82
 preferably comprises a zero backlash gearbox. The preferred gearbox is
 model #MSHV-50 B4117B available from Cone Drive Textron, Traverse City,
 Mich. The speed reducer 82 is coupled to an electric motor 85 (shown in
 FIG. 2). The preferred motor is a Goldline B-606-B-B9-225 available from
 Koll Morgan, Radford, Va. As an alternative to the motor 85 and speed
 reducer 82, a direct drive servomotor may also be used. An example is the
 "DR Series" Direct Drive Brushless Servo Motor available from the Parker
 Hannifin Corporation in Rohnent Park, Calif. The drive system 70 is center
 driven which is possible due to the high resolution associated with
 servomotors and zero backlash gearboxes. However, other drive systems such
 as edge driven systems with belts, pulleys, or gears may be substituted.
 With the use of an encoder (not shown) on the periphery 54 of the turret
 43, other types of motors can also be used including hydraulic motors and
 non-servo motors. Accordingly, the invention is not intended to be limited
 to a center driven system using a servomotor.
 The frame 76 is preferably U-shaped and supports the shaft 71 mounted
 inside the frame 76 on the bearings 73. The frame 76 also supports the
 motor 85 and the speed reducer 82. Accordingly, the frame 76 is
 constructed of a strong, rigid material capable of supporting the drive
 system 70 and the turret 43. The frame 76 is preferably supported and
 guided by a set of structural rails 88 that are disposed above, below, and
 on opposite sides of the frame 76. Other guide structures would also be
 suitable as will be apparent to those of ordinary skill in the art.
 The frame 76 is connected to and driven by an actuating mechanism 90. The
 actuating mechanism 90 may comprise a roller screw actuator as disclosed
 in U.S. Pat. No. 5,829,115, the disclosure of which is hereby incorporated
 by reference. Alternatively, the actuating mechanism 90 may comprise a
 hydraulic cylinder or the like or other suitable source of motive force
 known to those skilled in the art.
 Turning to FIG. 4, the tools 57 are disposed perpendicular to the axis of
 rotation of the turret 43. The tools 57 are disposed about the turret 43
 such that adjacent tools 57 are spaced far enough apart to provide
 clearance around the workpiece 16, when the active tool 57 is brought into
 engagement with the workpiece 16 by the actuating mechanism 90.
 In FIG. 5, all of the components that comprise the drive system 70 for the
 turret 43, namely the shaft 71, speed reducer 82 and motor 85, are shown.
 As described above, the speed reducer 82 is preferably a right angle zero
 backlash gear box. The motor 85, speed reducer 82, and shaft 71 rotate the
 turret 43 to index the tools 57 into a working position that is in
 alignment with the workpiece 16.
 The tools 57 are mounted on the side 49 of the turret 43. For the tools 57
 that must withstand the large forming forces associated with forming a
 rivet tail, the back end 100 of the tools 57 is disposed adjacent to the
 shaft 71 such that the shaft 71 provides support upon upset. In this
 manner, the shaft 71 and the bearings 73 withstand most of the upset
 forces rather than the periphery of the turret 43. By mounting the tools
 57 in this manner, the structural requirements for withstanding thousands
 of pounds of force are met without having to design a turret or turntable
 capable of withstanding all or most of the force at the periphery 54.
 In operation, the turret head apparatus 40 is mounted on a C-frame riveting
 machine of the type shown in FIG. 1. With the workpiece 16 positioned
 between the opposing ram 28 and the rotary turret head apparatus 40, the
 tools 57 are indexed in succession into the working position and then fed
 to the workpiece 16 by the actuator 90. As described above, the tools 57
 include a drill 60, a bucking ram 26, a hole inspection tool 22, a shaving
 tool 66 and the like. When one of the tools 57 is being fed to the
 workpiece 16, the other tools 57 are disposed at a sufficient angle such
 that the tools 57 do not obstruct or come into contact with the workpiece
 16. After the particular operation is finished, the actuator 90 retracts
 the turret 43 away from the workpiece 16 so that the tools 57 do not
 strike the workpiece 16 when they are rotated into the working position.
 Once the next tool 57 is in the working position, the actuator 90 feeds it
 to the workpiece 16 to begin the next step in the succession of steps
 required for installing a fastener such as a rivet 25 or the like. Due to
 the configuration of the rotary turret head apparatus 40, the feeding and
 rotating of the turret 43 can be performed simultaneously to reduce cycle
 times.
 Accordingly, the present invention offers several advantages including
 eliminating the need for separate actuators for each tool and eliminating
 the need for separate and individual engagement of each tool with a
 centrally located actuator. The present invention provides a single
 actuator feed mechanism 90 that feeds the entire turret head apparatus 40
 toward the workpiece 16. As a result the tools 57 can be removably
 attached to the turret 43 and do not have to conform to the other tools
 57. Each tool 57 where necessary can have its own motor and power supply,
 such as the drill 60 shown in FIG. 3, can be powered continuously or
 intermittently, and can be operated at different frequencies and rpm's.
 Because the tools 57 only have to mount to the turret 43 and do not have
 to engage individually with the actuator 90, the tools 57 can easily be
 interchanged.
 Another advantage of the present invention is that, because the turret 43
 is supported by a center shaft 71 and the tools 57 are mounted on the side
 of the turret 43, the shaft 71 provides support for the tools 57 to
 withstand the upset forces associated with riveting.
 Also, the rotary turret head apparatus 40 provides a modular design that
 enables the user to make tool changes and to add tools without the
 drawbacks associated with known apparatus.
 Another advantage of the present invention is that unlike the linear
 carriage systems, the rotary turret head apparatus can feed and rotate the
 turret simultaneously which reduces the overall cycle time.
 While the invention has been described in connection with certain preferred
 embodiments, it is not intended to limit the scope of the invention to the
 particular forms set forth, but, on the contrary, it is intended to cover
 such alternatives, modifications, and equivalents as may be included
 within the spirit and scope of the invention as defined by the appended
 claims.