Force sensor

• US 4,884,461 A
• Filed: 10/05/1988
• Issued: 12/05/1989
• Est. Priority Date: 10/13/1987
• Status: Expired due to Term

• Current Assignee: Sandvik Intellectual Property AB (Sandvik AB)
• Original Assignee: Sandvik AB
• Inventors: Meier-Dornberg, Karl E., Weck, Bernd K., Sawicki, Wolfgang H., Svensson, Tomas L.
• Primary Examiner(s): NOT, DEFINED
• Application Number:
  US07/253,586
• Time in Patent Office: 426 Days
• Field of Search: 73/862.04, 73/862.06, 73/104, 340/680
• US Class Current: 73/862.06
• CPC Class Codes: B23Q 1/36 Springs
• CPC Class Codes: B23Q 17/0966 by measuring a force on parts of the machine other than a motor
• CPC Class Codes: G01L 1/2231 the supports being disc- or ring-shaped, adapted for measuring a force along a single direction
• CPC Class Codes: G05B 19/4065 Monitoring tool breakage, life or condition
• CPC Class Codes: G05B 19/408 characterised by data handling or data format, e.g. reading, buffering or conversion of data

Abstract

A force sensor monitors the behavior of cutting tools during machining operations. The sensor is mounted on a machine tool of the type comprising a stable support portion and a carrier which includes a tool holder. The sensor is mounted between the stable support portion and the tool holder. The sensor includes a generally planar plate provided with a stable portion and flexible elements. The carrier is mounted to the flexible elements whereby forces from the tool holder are transmitted to the flexible elements for displaying same. Such displacement is detected by strain gauges mounted on deformable lands which interconnect the stable portion with the flexible elements.

Claims

1. A force sensor for a machining tool of the type comprising a stable support portion and a carrier including a tool holder in which a cutting tool is mounted, said force sensor being mounted in between said stable support portion and said carrier, said sensor comprising a generally planar plate which includes slots therein defining first and second zones resiliently arranged relative to each other within the plane of said plate, said zones being interconnected by an interconnecting portion of said plate, said first zone being connected to said carrier and said second zone being connected to said stable support portion, said sensor provided with gauges on a side of said interconnecting portion, said force sensor being flexible only in said plane of said plate, and said gauges arranged to detect forces directed in said plane in response to a machining operation.

2. A force sensor according to claim 1, wherein said gauges comprise strain gauges coupled to a complete Wheatstone-bridge and arranged in pairs such that one of said pairs measures an identical value of deformation as another of said pairs, said one pair measuring compressive deformation and the other of said pairs measuring an elongative deformation.

3. A force sensor according to claim 8, wherein said machining tool comprises a base surface, said stable support portion comprising a cross-slide indirectly mounted on said base surface, said plate being of generally rectangular shape and having pluralities of first and second holes extending therethrough, said first holes disposed at respective corners of said plate for receiving first bolts connecting said second zone to said cross-slide, said second holes being partially surrounded by first slots extending substantially perpendicularly through said plate in spaced relation to said second holes whereby elements of said plate disposed between said slots and said second holes define said second zone, said elements being displaceable relative to said second zone in a direction of movement, said second holes receiving second bolts connecting said first zone to said carrier whereby forces transmitted to said elements from said tool cause said elements to be displaced in said direction of movement.

4. A force sensor according to claim 3, wherein a first pair of said plate elements are arranged diagonally opposite one another, each of said first pair of plate elements being partially bordered by a pair of additional slots having a larger width than said first slot associated with the respective said second hole, adjacent ends of said additional slots being spaced apart to form a thin land therebetween defining said interconnecting portion of said plate interconnecting said second zone and said elements, said lands extending substantially parallel to said direction of movement of said elements, said gauges comprising strain gauges connected in pairs to respective ones of said lands.

5. A force sensor according to claim 4, wherein a second pair of said plate elements are arranged diagonally opposite one another, each of said plate elements of said second pair being partially bordered by two identical ones of said slots which comprise two straight ends and a midportion with is concavely curved relative to said second holes.

6. A force sensor according to claim 3, wherein said elements project beyond a surface of said plate to provide clearance between that plate surface and the one of said cross-slide and said tool holder toward which said plate surface faces.

7. The method for sensing forces arising during machining of a work piece in a machine tool, providing axial, radial and tangential cutting forces comprising the steps of:

providing a force sensor in the shape of a generally planar plate provided with slots defining zones resiliently arranged relative to each other in the plane of the plate,

providing means for fastening one zone of the plate to a carrier of a machine and another zone of the plate to a stable support portion of said machine, said carrier including a tool holder,

connecting the force sensor to a signal processing means,

measuring only radial and axial cutting forces transferred from the carrier to the sensor and disposed in the plane of the plate,

detecting signals from the sensor by means of the signal processing means in response to the magnitude of the cutting forces arising during machining.