Abstract: Disclosed is a parallel mechanism structure for controlling three-dimensional position and orientation. In the parallel mechanism structure according to the present invention, three links are connected to the main spindle of the mechanism and driven in vertical and horizontal direction, with a consecution that the main spindle connected to the three links achieves the six d.o.f motions. The structure includes three links comprised of a first link transferred along a circular vertical guide and second and third links transferred along corresponding rectilinear vertical guides and a circular horizontal guide on which the circular vertical guide and the two rectilinear vertical guides are horizontally transferred.

Abstract: A spindle device for machine tools that can eliminate the need for laborious air bleeding work and labor-demanding fitting/removing work for maintenance. The spindle device for machine tools includes a drawbar that is axially movably inserted into an axial hole of a tool spindle body. The drawbar serves to bias a tool in a clamping direction. An unclamping cylinder mechanism is provided in a rear of the tool spindle and serves to move the drawbar in an unclamping direction. The unclamping cylinder mechanism has a cylinder block fixed to a rear end wall of the tool spindle body and includes a plurality of bolts. A relay oil passage allows a hydraulic passage in the tool spindle body and a hydraulic passage in the cylinder block to communicate with each other.

Abstract: A rotary actuator with improved damping and stiffness is disclosed. The rotary actuator includes one or more bearing plates that form sliding-surface bearings to provide the desired preload to the rotary actuator. One embodiment of the invention includes a multi-piece bearing plate that makes repair or replacement of the bearing material in the sliding-surface bearings easy to perform. Another embodiment for applications where heat dissipation is critical includes thermal barriers on either side of the sliding-element bearings, with resilient members between the thermal barrier and a bearing ring used to supply the appropriate preload to the output shaft. The invention is particularly suited to precision applications, such as the drive unit for the swivel mechanism on the spindle head of certain types of five-axis milling machines.

Abstract: A spindle head holder (5) is pivoted on a base member (1), a linear drive (21) is mounted to the base member (1), a linear guide (50) is mounted to the spindle head holder (5), and an engagement member (60) is engaged with both linear drive and linear guide at a substantially identical part (35, 37) thereof.

Abstract: A reconfigurable tool changer allows a tool cartridge to be easily attached to, or detached from, a standard machine-tool spindle head. The modular design, includes a revolving tool cartridge having a plurality of tool holders, a meshing gear for engaging a tool holder with the spindle of the machine tool, and an adapter block for positioning the revolving tool cartridge on any standard machine-tool spindle head. The adapter block allows the automatic tool changer to be easily coupled to a wide variety of commercial machine-tool spindles, making the invention a truly reconfigurable and portable tool changer. The revolving tool cartridge incorporates a novel three-dimensional cam structure mechanism, which allows tool indexing to be achieved by means of only one actuator.

Abstract: A universal-joint tool head, having a tool platform which can move in three axes, at least three connecting rods which are articulatedly mounted on the tool platform and can be displaced independently of one another, at least three linear-movement drives, which are arranged around and at a distance from the tool platform and are parallel to one another, for the connecting rods articulatedly mounted thereon, the connecting rods being articulatedly mounted on the tool platform in such a manner that they can move on all sides and on the linear-movement drives in such a manner that they can pivot about pins running perpendicular to the direction of movement of the linear-movement drives.

Abstract: The invention concerns a device for infinitely variable support of a tool on a drivable tool spindle of a machine tool. To provide such a device which allows exact adjustment of the tool within a range of one millimetre, at the same time avoiding centrifugal force-related imbalances, it is proposed that the tool is exchangeably attached to a tool carrier which is mounted in a housing so as to be pivotable about an axis of rotation of the tool carrier extending at an angle, preferably at a right angle, to the axis of rotation of the tool spindle.

Abstract: A device for producing relative motion with two translational degrees of freedom between a spindle means (95, 195, 295, 395) with a spindle which bears the first part of a first pair of parts formed from a workpiece and a tool, and a retaining element for holding the second part of the first pair of parts, has a first base part to which a first part of a second pair of parts which is formed from the spindle means (95, 195, 295, 395) and the retaining element is attached. The movement device furthermore comprises a second base part, and at least one of the two base parts can be moved in a straight line with respect to the other along a linear guide with a first translational degree of freedom.

Abstract: A machining apparatus has a guide extending in an x-direction, an x-slide displaceable in the x-direction on the guide, a y-slide displaceable in a y-direction generally perpendicular to the x-direction on the x-slide, and a z-slide displaceable in a z-direction generally perpendicular to the x- and y-directions on the y-slide. A tool holder is pivotal about a holder axis generally parallel to the x-direction on the z-slide and carries a tool rotatable about a tool axis perpendicular to the holder axis on the z-slide. The tool holder and tool have a center of mass generally at the holder axis. An actuator tips the tool holder and tool relative to the z-slide about the holder axis on the z-slide.

Abstract: A machine tool has a workpiece table for fixing workpieces to be machined and a tool spindle for receiving in a fixture the tools used for machining the workpieces. The machine tool works with an overhead tool pointing upwards in the operating condition.

Abstract: A device for producing relative motion with two translational degrees of freedom between a spindle means (95, 195, 295, 395) with a spindle which bears the first part of a first pair of parts formed from a workpiece and a tool, and a retaining element for holding the second part of the first pair of parts, has a first base part to which a first part of a second pair of parts which is formed from the spindle means (95, 195, 295, 395) and the retaining element is attached. The movement device furthermore comprises a second base part, and at least one of the two base parts can be moved in a straight line with respect to the other along a linear guide with a first translational degree of freedom.

Abstract: A milling machine includes a bi-directional, variable speed, rotary workpiece-holding table, a table drive sized to achieve relatively high acceleration and deceleration rates, a cutting tool mounted to a single or dual axis head, and a control system adapted to achieve a high degree of tool position and table rotational position accuracy cooperating to permit high-speed machining operations, including substantially dome-shaped parts characterized by circumferential surface portions interrupted by radial wall portions. A dual table drive and interchangeable head arrangement make the machine also suitable for conventional turret lathe operations.

Abstract: Module with parallel kinematic movement and orthogonal axes, characterised because it has a fixed structure; and a passive structure that has at least one kinematic shears joined at one end to the fixed structure and at the other end to a flat mobile structure, one of these unions being articulated; and a spatial mobile structure carrying the work head and which can be moved linearly respect to the flat mobile structure; and arms joined at one end to the fixed structure and at the other end to the spatial mobile structure, one of the unions having two degrees of freedom and the other union three degrees of freedom; and means to activate the movement of the arms.

Abstract: Operating head for automatic machine tools of the type comprising a structure (2) which moves along a set of three Cartesian axes, a first support (3), fitted to the said structure in such a way that it can rotate around a first axis (C), and a chuck unit (5) fitted to the said support, wherein the said chuck unit (5) is interchangeable and projects from the said first support (3), and is designed to allow angular positioning around a second axis (A) orthogonal to the said first axis (C). Said first support (3) incorporates a power transmission system and means designed to connect the said power transmission system to the said chuck unit (5). This feature allows to change over from roughing to finishing tasks without replacing the entire head, as is necessary with known equipment in which the chuck assembly is mounted on a fork support, merely by replacing the chuck unit, a much quicker and cheaper operation.

Abstract: Operating head for machine tools characterised in that it comprises:

Abstract: A spindle head holder (5) is pivoted on a base member (1), a linear drive (21) is mounted to the base member (1), a linear guide (50) is mounted to the spindle head holder (5), and an engagement member (60) is engaged with both linear drive and linear guide at a substantially identical part (35, 37) thereof.

Abstract: The present invention is designed to realize structure having high rigidity in any direction and to realize a parallel mechanism machining device having good chip removal property. According to the present invention, forked adjustable joints 28 are provided at two positions near the tip end of a movable body 20 and near the rear end thereof, respectively, two first links 36 and two second links 37 are attached to the movable body 20 and the tip ends of these links are extended in X and Y axis directions and coupled to a machine-side fixed platform through adjustable joints, respectively. A link 5 extending in Z axis direction is attached to the rear end of the movable body 20 and a restriction link 6 is attached to the back of the forked adjustable joint 28 near the tip end.

Abstract: A machining system has a frame forming a working station and a mounting plate movable relative to the frame in and adjacent the station in a first main direction, in a second direction transverse to the main direction, and in a third direction transverse to the first and second directions. A machine tool head is mounted on the mounting plate and a plurality of struts have outer ends swiveled on the mounting plate and extending inward away from the plate. A mechanism acting on the struts moves the plate and tool head in the three directions. A main panel is movable only in the first and second directions and the head is mounted in the panel for movement relative thereto only in the third direction. In addition a pair of side panels of changeable length each have an inner edge connected along a respective inner axis parallel to the third direction to a respective outer edge of the main panel and a respective outer edge connected at a respective outer axis parallel to the third direction on the frame.

Abstract: An apparatus for milling the surface of low slope substrate has a milling device, such as a saw, and a track along which the milling device may move. The track is supported above the substrate by a plurality of adjustable supports which have adjustment means for orienting the track vertically or at a desired angle to horizontal. A mounting assembly for the milling device has means for engaging the track and enabling movement of the assembly along the track with the milling device depending from the mounting assembly. Adjustment means coact with the milling device and the mounting assembly enabling the device to be oriented in a desired manner relative to the substrate.

Abstract: The present invention provides a guide apparatus for use with a portable router, for enabling the router to rout an edge of a workpiece at virtually any angle between 0.degree. and 90.degree.. The guide apparatus comprises: a main body for receiving a router base and including an opening for a router bit to extend therethrough; a reference member having a planar surface for abutment with a planar surface of a workpiece and including a guide edge along one edge thereof; a hinge means connecting the reference member to the main body; a securing means for securing the reference member to the main body at a desired angle; and a guide bar securable relative to the workpiece and providing a guide surface for abutting the guide edge of the reference member, to guide the router bit of the router mounted on the main body along the edge of the workpiece.

Abstract: An oil conduit mechanism for spindle head of five-axis machine tool integrates cutting liquid conduit, lubricating oil conduit and braking oil conduit within the spindle head. Those conduits comprises ducts to guide cutting liquid, braking oil and lubricating oil to the processing location for cooling and lubrication. The oil conduit mechanism further comprises a lubricating oil recycling conduit to recycle the lubricating oil for repeated use.

Abstract: The device serves for moving a movable platform (2) in respect to a base (1). The connection between platform and base is established by six legs (4a-4f), which are connected to the platform in articulated manner. At the base side, they rest in articulated manner on sliding carriages (6a-6f). The sliding carriages can be displaced along parallel guiding tracks (7a-7c), by means of which position and orientation of the platform can be adjusted. Two sliding carriages are running independently of each other on each guiding track, allowing a movement with a total of six degrees of freedom. Since two sliding carriages share one guiding track, the design is simplified and some drive components can be dispensed with.

Abstract: A working head for numeric-control machine tools is adapted to be moved along two or three axes relative to one or two parts mounted on respective worktables which can rotate about respective parallel axes. According to the present invention, the head supports one or preferably two tool-supporting spindles which are pivoted about a common axis which is transverse to the axes of the spindles under the actuation of motor means which are rigidly coupled to the head and are controlled by a numeric control unit.

Abstract: A composite mechanism multi-axis machine tool includes an orthogonal coordinate feeding axis mechanism and a parallel type spatial linkage mechanism. The orthogonal coordinate feeding axis mechanism has two orthogonal platforms to provide two dimensional motion vectors. The parallel type spatial linkage mechanism has three sets of linear feeding modules engaging with a base frame for holding a main spindle which further holds a tool cutter. The parallel type spatial linkage mechanism provides one dimensional motion and two dimensional rotation for the tool cutter. A controller is provided to control and coordinate the movements of the orthogonal coordinate feeding axis mechanism and the parallel type spatial linkage mechanism.

Abstract: A camshaft shaping machine that is capable of providing a camshaft shaped with a cam surface inclined with respect to the cam axis is disclosed. The machine includes a pair of work heads (2) for clamping a camshaft workpiece (4) at its opposed ends rotatably about a longitudinal axis of the workpiece; an X-axis slide (8) movable along an X-axis that extends horizontally in a direction parallel to the longitudinal axis of the camshaft workpiece (4); and a Y-axis slide (11) movable along a Y-axis that horizontally extends in a direction orthogonal to the X-axis. An indexing table (13) is mounted on one of the X-axis and Y-axis slides (8. 11) so as to be turnable about a turning center (0) in a horizontal plane to angularly index and position, relative to the camshaft workpiece (4), a milling cutter (21) that is rotatably supported on a cutter head (20) to angularly mill the workpiece and thereby to permit an inclined cam surface to develop therein.

Abstract: In the case where a product having a free-curved surface is obtained, a machining work is performed by separate machine tools. Therefore, works of attaching and removing a half-machined product are necessary. Consequently, a lot of working time and labor are required. Also in an automatic production system, productivity is lowered if the system is stopped by failure in gripping during the attaching and removing works and an enormous equipment cost is required. A machining apparatus M comprises a main chuck head 1 having a control axis for holding and rotating a long bar member W, a head stock assembly 3 having three or more control axes, and a bar member feeder 5 for feeding the long bar member W to the head stock assembly 3. These four axes are simultaneously controlled to manufacture a plurality of products V having free-curved surfaces from the long bar member W.

Abstract: A machine tool includes a base, a traveling plate to which a tool is to be attached, plural rods, and plural drive mechanisms fixed to the base. Each of the drive mechanisms is provided with a slide table movable on the drive mechanism and with an actuator for moving the slide table. One end of each of the rods is swingably connected to the corresponding slide tables through a first joint and the other end of each of the rods is swingably connected to the traveling plate through a second joint. Each of the first and the second joints include two rolling elements, each of which is rotatably supported by a rolling bearing to swing the rod.As the rolling elements are supported by the rolling bearings without a clearance, the positioning accuracy of the machine tool is enhanced.

Abstract: A device for manipulating workpieces has a support and linear actuators for moving the support. A coupling gear is connected to the support. The coupling gear includes at least two coupling members pivotably connected to one another. The at least two coupling members move the support in a plane of movement and lock a degree of freedom perpendicular to the plane of movement.

Abstract: The present invention relates to a computer aided design and manufacturing system. The system comprises a platform suspended by means of three pairs of supportive legs which are coupled at triangularly spaced-apart locations by means of three universal joints, each of which couples to one end of each of the two legs of a respective pair.

Abstract: Ball screws are moved axially to move a spindle unit in directions X, Y to position a cutter mounted on the spindle unit. Support arm assemblies which support the spindle unit are also moved. Then, a slide table which supports the support arm assemblies is moved in a direction Z to cause the cutter to machine a workpiece.

Abstract: A pattern sizing tool for use as a milling device for removing a portion of a surface of a stiff material to leave a desired thickness of material and is particularly useful for milling a hard plastic coping like that produced in a tooth replacement procedure for forming, from that coping, a crown as a replacement tooth in a practice of a "lost wax casting procedure". The tool includes a pair of upper and lower arms that are coupled together at their ends to be scissored and are spring biased apart. The upper arm includes a mount with an arrangement for maintaining a dental rotary grinder thereon that has a chuck for mounting a milling burr.

Abstract: A machine tool of the present invention includes a base fixed to an outside fixed portion, a travelling plate to which a tool is to be attached, plural guide portions radially outwardly fixed to the base at a predetermined angle, and plural rods. Each of the plural guide portions is provided with a slide table movable in a longitudinal direction of the guide portion and an actuator for moving the slide table. One end of each rods is connected with one of the slide tables through first joint means and another end of each of the rods is connected to the traveling plate through second joint means.

Abstract: An angle spindle attachment for a vertically movable spindle unit is provided for rotating a cutting tool in a generally horizontal orientation. The attachment includes a spindle assembly having a drive train that is mechanically independent from the drive train of the vertically movable spindle unit, and a connector block for detachably connecting the spindle assembly at a transverse angle with respect to the vertically movable spindle unit. The connector block may include an angular adjustment mechanism that allows the spindle assembly to be oriented at an angle above or below the horizontal, as well as a rotational adjustment assembly that allows the spindle assembly to be pivotally adjusted about the axis of rotation of the vertically movable spindle unit.

Abstract: A machine tool includes a machine table for receiving a workpiece, a headstock disposed above the table, a turntable mounted on an underside of the headstock and being rotatable relative thereto about a vertical first axis, and a spindle mounted on the turntable for movement in a direction oriented radially relative to the first axis. The spindle includes a chuck for supporting a machining tool for rotation about a second axis oriented eccentrically relative to the first axis. The spindle is rotatable relative to the turntable about a third axis oriented orthogonally relative to the first axis. A second spindle can be mounted on the turntable for rotation about the first axis.

Abstract: A small scale milling machine including a machine base having an upright rotary wheel, a rotary column sleeve fixedly secured to the rotary wheel, a retractable support fixedly secured to the inside of the rotary column sleeve to hold a vertical mounting frame outside the rotary column sleeve, a machine head suspended from the bottom end of the vertical mounting frame and connected to the rotary column sleeve by a dovetail joint and moved vertically along a longitudinal rack on the rotary column sleeve, the rotary column sleeve having a longitudinal track at one lateral side, two stop blocks adjustably fixed to the longitudinal track at different elevations to limit the vertical moving distance of the machine head, and a scale at the front side along the longitudinal track for measuring the vertical moving distance of the machine head.

Abstract: The present invention relates to a computer aided design and manufacturing system. The system comprises a platform suspended by means of three pairs of supportive legs which are coupled at triangularly spaced-apart locations by means of three universal joints, each of which couples to one end of each of the two legs of a respective pair. The two legs of each pair extend from their respective universal joint in divergent directions to spaced-apart locations in an overhead mounting where each leg is drivingly engaged by a respective gimbal-mounted electric motor arranged to move the leg in its own longitudinal direction. The platform position and orientation can be controlled by appropriate operation of the six leg drive motors.

Abstract: A space frame system for use with a machine, such as a machine tool, is disclosed. The system as used with a machine tool includes a base and a machine component, such as a workpiece support, mounted to the base. A first space frame is mounted solely to the workpiece support. A second and separate space frame is connected to the first space frame by a plurality of extensible legs. Another machine component, such as a tool holder, is rigidly mounted to the second space frame for cooperation with a workpiece mounted on the workpiece support. Thus, as the extensible legs are independently controlled, the tool holder is moved along a desired path with respect to the workpiece support to perform various cutting operations on the workpiece.

Abstract: The milling head (1) comprises:a principal body (2),an interposed piece (5), which is mounted to rotate on the principal body (2) and which is equipped with a first crown gear (12a),means for driving and for blocking in rotation the interposed piece (5) with respect to the body (2),a spindle-holder (3), which is mounted to rotate along axis XX' with respect to the interposed piece (5), on which is fixed a second crown (12b) adapted to mesh with the first crown (12a), and which is mobile in translation along axis XX' between a position of blockage in rotation in which the crown gears (12a, 12b) mesh in one another, and a position of setting in rotation in which the two crown gears (12a, 12b) are out of mesh,means (13) for setting in translation the spindle-holder (3) between the positions of blockage and of setting in rotation,and means (17, 18, 19) for setting in rotation the spindle-holder (3) along axis XX'.

Abstract: A universal milling and drilling machine provided with a swivel milling head for an automatic reset from horizontal to vertical machining. The driving of the work spindle is carried out by a driving motor via bevel gears and a shift transmission which ensures a high torque even in a low rotation speed range. For optimizing the power transmission between the driving motor and the work spindle, the shift transmission is arranged in the swivel milling head, and the bevel gear transmission is seated directly on the motor shaft of the driving motor. The swivel milling head is mounted on the front surface of a support housing, the front surface being downwardly inclined by 45.degree..

Abstract: A universal spindle head device for machine tools, comprising a spindle head with a main spindle, a built-in motor, a first rotating spindle with the end fixed to said spindle head and appearing an inclined angle of 45 degrees toward the main spindle of the machine tool, and its center having a hollow passage; a second rotating spindle with its center axial line located on identical plane to center axial line of said main spindle and first rotating spindle and appearing at an inclined angle of 45 degrees toward the spindle center of the first rotating spindle; and a drive device for driving the spindle head to enable it to rotate centering around the first rotating spindle and second rotating spindle and to change over in direction in order to perform five-side processing of workpiece.

Abstract: A machine tool with a work supporting table is disclosed having a main shaft rail body with vertically extending sliding rails located in a vertical plane extending obliquely to a front face. A sliding machine seat is slidably mounted on the vertically extending sliding rails and has a first mounting surface extending parallel to the vertical plane of the sliding rails. A second machine seat having a second mounting surface located in a plane extending obliquely to the vertical plane of the sliding rails is rotatably attached to the first mounting surface. A main shaft machine seat is attached to the second machine seat.

Abstract: This invention relates to a machine tool providing a unique approach towards positioning and movement for a workpiece and tool in numerical control machine tool applications. The goal is to provide decrease machine costs and maintenance. Current machine tools such as milling machines principally rely on linear sliding mechanisms to position a table and workpiece relative to a spindle and provide motion for cutting. In accordance with this invention motion and positioning is achieved through less cost and readily available mechanisms through use of a plurality of revolute joints. Arms are provided having tangential actuators featuring extremely high stiffness and zero backlash actuator capable of a high degree of positioning accuracy. The arms resemble three dimensional truss structures for added structural stiffness characteristics. Preferably a cable drum type tangential actuator is employed in conjunction with this invention.

Abstract: An improvement of spindle for vertical-horizontal machine tools, comprising a built-in motor type spindle, a rotating shaft, a drive device, and a locating-device, wherein the spindle is mounted on the machine tools by means of the rotating shaft; the rotating shaft maintains a 45.degree. incline toward the horizontal and vertical datum lines of the machine tools and is rotably driven by drive device to lead the spindle to change into vertical or horizontal manner; the locating device is provided for ensuring the spindle in accurate position. The characteristics of the invention are that the spindle mandrel is directly driven by a built-in motor within the spindle head; and the rotating shaft is defined to contain a hollow manner therein for the spindle pipelines and power cables to pass through its center.

Abstract: A machine such as a machine tool includes a pair of spaced platforms. One platform may mount an operator such as a tool in a spindle, and the other platform may mount an object such as a workpiece. The spaced platforms are joined by six powered and extensible legs joined to the respective platforms by universal joints. The length of the legs is individually manipulated to vary the positions of the platforms and, therefore, the object and operator relative to each other. Four of the legs are arranged into two pairs which are spaced apart to provide between them a part of a corridor for moving the workpiece into a working position. The two legs in each pair may cross each other. The other two legs extend away from each other and provide another part of the corridor between their inboard ends.

Abstract: A drive shaft 40 extends through a ram 42. The ram can be driven up and down by rotating a screw shaft 35. The ram carries with it a motor 44 which drives a pulley 36 connected to the top of the shaft 40 for rotating that shaft 40. The ram 42 can be rotated upon operation of a motor 60 which drives a worm 62 to engage a worm wheel 64 which surrounds the ram 42 and is fast therewith.

Abstract: A self-drilling and tapping screw, the self-drilling portion of which is formed in two major operations. A cutting tip is formed on the tip of a screw blank by a pair of rotating circular saw blades in a first operation. A pair of flutes extending from the cutting tip to the threaded portion of the stem are formed by a second pair of rotating circular saw blades in a second operation.

Abstract: A milling head is provided having an axially displacable spindle for retaining a machine tool, the spindle being pivotally movable with respect to a workhead, and the lower end of the machine tool lying on the axis of rotation. In a first embodiment, the spindle is rotatably mounted to the workhead via an angular carrier, and the workhead is axially movable. In a second embodiment, the workhead includes guide rails for guiding rotational movement of a plate-shaped structure with respect to the workhead, and the plate-shaped structure includes guides for controlling linear displacement of the angular carrier.

Abstract: This invention relates to an operating head for automatic machine tools of the type consisting of a fork with several degrees of freedom to which the support of a chuck is hinged, which can rotate arond an axis passing through the arms of the fork. In accordance with the invention clamping devices are provided, designed to lock the support of the chuck in any angular position to the fork, to perform power tasks with high precision.

Abstract: An operating head for automatic machine tools consists of a fork (2) having a shaft (6) rotatably mounted to a support arm (1) for rotating around an axis (C). A motor chuck (5) is rotatably mounted between the arms of the fork and rotates around an axis (A). Axis (A) is orthogonal to axis (C). Drive systems (10,9,8) control the rotation of the fork (2) around the axis (C) by directly engaging the shaft (6). In order to transmit rotational motion for the fork (2) around support arm (1) and for the positioning motion of the motor chuck (5), a hypoid toothed crown wheel (8,13) and pinion (9,14) are used.

Abstract: The invention relates to improvements in a tilting mechanism for a saddle swivel head for a double housing type machine tool. The saddle swivel head 13 is provided at the sides thereof in the tilting direction with hydraulic cylinders 18R, 18L, to which is connected a hydraulic piping system 19 for giving swivel balancing pressures and back pressures when the swivel head 13 is tilted by a predetermined angle by a tilting driving mechanism. The saddle swivel head 13 is tilted while providing swivel balancing pressures to the hydraulic cylinders 18R, 18L, and after tilting the head by the predetermined angle, back pressures are applied to the hydraulic cylinders 18R, 18L to compensate for a tilting moment of the saddle swivel head 13.