Turning – Pattern section
Patent
1987-03-16
1990-06-26
Schmidt, Frederick R.
Turning
Pattern section
51166TS, 51354, 82158, B23B 328
Patent
active
049361732
DESCRIPTION:
BRIEF SUMMARY
The invention relates to machine tools and in particular to the tool holders of such machine tools and their actuation.
In conventional machine tools, even machine tools of the numerical controlled (NC) and computer numerical controlled (CNC) type, the tool is mounted on a carriage which is moved by a motor driving the carriage through a lead screw. Tool control signals are supplied to the motor by a control system to cause the tool to machine a rotating workpiece to a required profile.
It is a disadvantage of such machine tools that the inertia of the tool carriage and the backlash in the lead screw limits the rate at which the tool can be moved. Thus such machine tools cannot rapidly machine workpieces to complex surface profiles.
According to a first aspect of the invention, there is provided a machine tool comprising a workpiece holder for holding and rotating a workpiece to be machined, an elongate tool holder having two ends and being mounted, intermediate said ends, for pivotal movement, a tool carried towards one end of the elongate tool holder for machining the workpiece, an electric actuator having an actuator coil and a movable output member connected to the other end of the elongate tool holder, and a control system for supplying to the actuator coil, signals corresponding to a required workpiece profile, operation of the actuator moving the movable output member to pivot the tool holder to cause the tool to machine the workpiece to said profile.
According to a second aspect of the invention, there is provided a machine tool comprising a workpiece holder for holding and rotating a workpiece to be machined, an elongate tool holder having two ends and mounted intermediate said ends for pivotal movement about an axis normal to the length of said holder, said mounting including two spring strips which are connected between the tool holder and a mounting, which diverge towards the tool holder and which lie in respective planes intersecting at said pivot axis, a tool at one end of said tool holder for machining the workpiece and an actuator at the other end of the tool holder for pivoting the tool holder about said axis in accordance with control signals supplied thereto, to cause the tool to machine the workpiece to a required profile.
The following is a more detailed description of one embodiment of the invention, by way of example, reference being made to the accompanying drawings in which:
FIG. 1 is a schematic view of a machine tool incorporating an elongate tool holder pivotable about an axis by the actuator, and including a position transducer, and
FIG. 2 is a view, to a larger scale than FIG. 1, of the tool holder actuator and position transducer of FIG. 1, the actuator and the position transducer being shown in section.
Referring first to FIG. 1, the machine tool comprises a workpiece holder 10 for holding and rotating a workpiece 11. This workpiece 11 may be, for example, a piston or a bearing whose surface is to have a complex profile, such as the profiles disclosed in our U.K. Patent Specification No. 2104188.
A carriage 12 is mounted for movement in a direction parallel to the axis of rotation of the workpiece 11 by a motor 13 acting through a lead screw 14. The carriage 12 carries a tool holder 15 connected to a mounting 16 and movable by an actuator 17. One end of the tool holder 15 carries a tool 18 and the other end of the tool holder is connected to a linear variable displacement position transducer 19.
These latter parts will now be described in more details with reference to FIG. 2.
The tool holder 15 is of low inertia and is formed by a straight bar of generally ractangular cross-section which may be of titanium or an aluminium alloy. The tool holder 15 is carried on the mounting 16 for pivotal movement about an axis normal to the length of the tool holder 15. This mounting is effected by two flat spring strips 20 which are connected between the tool holder 15 and the mounting 16, which diverge towards the tool holder 15 and which lie in respective planes intersecting said pivot
REFERENCES:
patent: 1759196 (1930-05-01), Jackson
patent: 2525216 (1950-10-01), Garrand
patent: 3361018 (1968-01-01), Druckman
patent: 4203062 (1980-05-01), Bathen
patent: 4509002 (1985-04-01), Hollis, Jr.
patent: 4646595 (1987-03-01), Slee
VDI "Getriebetechnik", VDI-Tagungsheft, Oct., 1953, Deutscher--Ingenieur--Verlag GmbH (Dusseldorf, DE).
AE PLC
Schmidt Frederick R.
Showalter Robert
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