# US 4,396,322 A · Contact detecting apparatus

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- Number: US 4,396,322 A
- Document ID: US4396322A
- Status: Granted
- Kind: A
- Application number: 06/218,678
- Filed: 1980-12-22
- Granted: 1983-08-02
- Earliest claimed: 1980-12-22
- Assignees: Toyoda Koki Kabushiki Kaisha
- Inventors: Kenji Nomura; Akira Tsuboi; Kunihiko Eto; Kunimichi Nakashima
- Web page: https://patentgrep.com/patent/US4396322A

## CPC

- G01B 7/003: {for measuring position, not involving coordinate determination (coordinate measuring G01B7/004)}
- B23Q 17/2241: {Detection of contact between tool and workpiece}
- G05B 19/18: Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of program data in numerical form (G05B19/418 takes precedence)
- G05B 2219/37405: Contact detection between workpiece and tool, probe, feeler
- Y10T 408/14: Responsive to condition of Tool or tool-drive
- Y10T 408/16: with control means energized in response to activator stimulated by condition sensor
- Y10T 408/172: Responsive to Tool
- Y10T 409/30392: with means to protect operative or machine [e.g., guard, safety device, etc.]
- Y10T 409/309464: and draw bar
- G01B: MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- B23Q: DETAILS, COMPONENTS, OR ACCESSORIES FOR MACHINE TOOLS, e.g. ARRANGEMENTS FOR COPYING OR CONTROLLING (tools of the kind used in lathes or boring machines B23B27/00); MACHINE TOOLS IN GENERAL CHARACTERISED BY THE CONSTRUCTION OF PARTICULAR DETAILS OR COMPONENTS; COMBINATIONS OR ASSOCIATIONS OF METAL-WORKING MACHINES, NOT DIRECTED TO A PARTICULAR RESULT
- G05B: CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS (systems for controlling or regulating non-electric variables G05D; systems for regulating electric or magnetic variables G05F; control devices or systems insofar as characterised by mechanical features only G05G)
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

A contact detecting apparatus for detecting the contact between a workpiece and a tool in a machine tool which includes a coil mounted on a spindle head and connected to an AC power source for generating an induced current in a looped secondary circuit including the workpiece, a work table, a machine body, a spindle head, a brush, a clamp bar for clamping the tool on a tool spindle, springs interposed between the spindle and the clamp bar, the tool spindle and the tool, when the workpiece and the tool are moved relatively into contact with each other. The brush is kept contact with the clamp bar at the rotational axis of the tool spindle. A detector is connected between the AC power source and the coil for detecting a change in an electric signal caused by the contact between the workpiece and the tool.

## Claims

### Claim 1

In a machine tool including a machine body, a work table mounted on said machine body for mounting thereon a workpiece to be machined, a spindle head mounted on said machine body, a tool spindle rotatably supported in said spindle head for removably supporting a tool, a clamp bar received in said tool spindle in coaxial relationship therewith and engageable with said tool for clamping the same relative to said tool spindle, spring means interposed between said tool spindle and said clamp bar urging said clamp bar in a direction to clamp said tool, unclamping means for moving said clamp bar against said spring means to unclamp said tool, and control means for effecting relative movement between said work table and said tool spindle, a contact detecting apparatus comprising:
a brush disposed in contact engagement with said clamp bar in coaxial alignment therewith and electrically connected to said spindle head;
an AC power source;
a coil mounted on said spindle head and connected to said AC power source for generating an induced current in a looped secondary circuit including the workpiece, work table, machine body, spindle head, brush, tool spindle and tool, when said workpiece and said tool are moved relatively into contact with each other; and
means connected between said AC power source and said coil for detecting a change in an electric signal caused by the contact between said workpiece and said tool.

### Claim 2 (depends on 1)

A contact detecting apparatus as set forth in claim 1, wherein said clamp bar further comprises a contact member made of copper alloy in contact with said brush.

### Claim 3 (depends on 1, 2)

A contact detecting apparatus as set forth in claim 1 or 2, wherein said unclamping means further comprises a hydraulic cylinder disposed in face to face relationship with said clamp bar, and a piston slidably received in said hydraulic cylinder in axial relationship with said tool spindle and provided with a piston rod engageable with the end surface of said clamp bar, and wherein said contact detecting apparatus further comprises a support rod slidably received in said piston in coaxial relationship therewith and supporting said brush at a first end thereof, and spring means disposed between said piston and said support rod for urging said brush into contact with said clamp bar, a second end of said support rod being electrically connected to said spindle head.

### Claim 4 (depends on 3)

A contact detecting apparatus as set forth in claim 3, further comprising means for preventing rotation but allowing axial movement of said support rod relative to said piston.