Electromagnetic holding device

• US 5,041,806 A
• Filed: 07/09/1990
• Issued: 08/20/1991
• Est. Priority Date: 07/07/1989
• Status: Expired due to Term

• Current Assignee: Carl Zeiss Industrielle Messtechnik GmbH (Carl-Zeiss-Stiftung)
• Original Assignee: Carl-Zeiss-Stiftung
• Inventors: Wirth, Michael, Enderle, Eckhard, Baier, Bernd
• Primary Examiner(s): Harris, George
• Application Number:
  US07/550,029
• Time in Patent Office: 407 Days
• Field of Search: 335/229, 335/230, 335/288, 335/290, 335/289, 335/295, 33/561, 29/568
• US Class Current: 335/295
• CPC Class Codes: B23Q 3/1546 using permanent magnets
• CPC Class Codes: G01B 7/012 Contact-making feeler heads therefor
• CPC Class Codes: H01F 2007/208 combined with permanent magnets
• CPC Class Codes: Y10T 483/19 Miscellaneous

Abstract

The invention is directed to an electromagnetic holding device which includes one or more permanent magnets and an electromagnet. The holding device releases and pulls in units which are held thereon. During an exchange operation, the field of the electromagnet is superposable on the field of the permanent magnet either in the same direction or in the opposing direction and thereby intensifies or neutralizes the holding force. In order to provide the smallest possible assembly volume and lowest weight with the highest possible holding force, the permanent magnet is disposed ahead of the electromagnet when viewed with respect to the exchange face. When the exchange part is pulled in, the field lines of the electromagnet run in a completely closed flux-conducting part which is not interrupted at any location by an air gap.

Claims

1. A holding device for interchangeably holding task units each having an armature so as to permit the task unit to be held by magnetic force, the holding device comprising:

a flux-conducting member defining an annular gap;

permanent magnetic means having a permanent magnetic field for acting on the armature of a task unit with a holding force to hold the task unit on said holding device;

electromagnetic means for superposing an electromagnetic field on said permanent magnetic field when the task unit is transferred to or away from said holding device;

said electromagnetic means being seated in said annular gap and said electromagnetic field defining a magnetic field axis;

said permanent magnetic means defining magnetic poles and being seated in said gap so as to cause said magnetic poles to be aligned radially of said magnetic field axis; and

,

said armature and said flux-conducting member conjointly defining a contact engaging interface when said task unit is in position on said holding device so as to cause said flux-conducting member and said armature to define a completely closed magnetic circuit for the field lines of said electromagnetic field.

2. The holding device of claim 1, said permanent magnetic means being a single-piece ring-shaped permanent magnet having a radially polarized magnetic field and being seated in said annular gap.

3. The holding device of claim 1, said permanent magnetic means being a plurality of axially polarized individual magnets seated in said gap in radial alignment with respect to said magnetic field axis.

4. The holding device of claim 1, said permanent magnetic means having a first axial dimension and said electromagnetic means having a second axial dimension greater than said first axial dimension.

5. The holding device of claim 1, each of said task units being a probe pin of a coordinate measuring apparatus and incorporating said armature therein.

6. The holding device of claim 1, each of said task units being a probe head of a coordinate measuring apparatus and incorporating said armature therein.

7. A probe head of a coordinate measuring apparatus for interchangeably holding probe pins each having an armature so as to permit the probe pin to be held by magnetic force, the probe head comprising:

a holding member;

a displaceable part mounted in said holding member so as to be displaceable with respect thereto;

a holding device mounted in said displaceable part for engaging, holding and releasing the probe pin, the holding device including;

a flux-conducting member defining an annular gap;

permanent magnetic means having a permanent magnetic field for acting on the armature of a probe pin with a holding force to hold the probe pin on said holding device;

electromagnetic means for superposing an electromagnetic field on said permanent magnetic field when the probe pin is transferred to or away from said holding device;

said electromagnetic means being seated in said annular gap and said electromagnetic field defining a magnetic field axis;

said permanent magnetic means defining magnetic poles and being seated in said gap so as to cause said magnetic poles to be aligned radially of said field axis; and

,

said armature and said flux-conducting member conjointly defining a contact engaging interface when said probe pin is in position on said holding device so as to cause said flux-conducting member and said armature to define a completely closed magnetic circuit for the field lines of said electromagnetic field.

8. A probe head for a coordinate measuring apparatus for interchangeably holding a plurality of probe pins each having an exchange plate defining an armature, the probe head comprising:

a holding member;

a displaceable part defining a longitudinal axis and being mounted in said holding member so as to be displaceable with respect thereto;

resilient biasing means disposed in said displaceable part for generating a resilient biasing force;

an electromagnetic chuck mounted in said displaceable part so as to be movable along said axis and against said resilient biasing force;

the electromagnetic chuck including;

a flux-conducting part having a longitudinal axis and defining an annular gap;

permanent magnetic means having a permanent magnetic field for acting on the armature of a probe pin with a holding force to hold the probe pin on said chuck;

electromagnetic means for superposing an electromagnetic field on said permanent magnetic field to strengthen the latter when transferring a probe unit onto said chuck and for superposing an electromagnetic field on the permanent magnetic field in opposition thereto to weaken the latter when transferring the probe pin off said chuck;

said electromagnetic means being seated in said annular gap;

said permanent magnetic means defining magnetic poles and being seated in said gap so as to cause said magnetic poles to be aligned radially of said longitudinal axis of said flux-conducting part; and

,

said permanent magnetic means being stacked in said gap on top of said electromagnetic means so as to cause said permanent magnetic means to be directly adjacent said armature when the probe pin is held on said chuck.

9. The probe head of claim 8, said permanent magnetic means having a first axial dimension and said electromagnetic means having a second axial dimension greater than said first axial dimension.

10. The probe head of claim 8, said permanent magnetic means being a plurality of axially polarized individual magnets seated in said gap in radial alignment with respect to said longitudinal axis of said flux-conducting part.

11. The probe head of claim 8, said flux-conducting part and said armature conjointly defining a completely closed magnetic circuit for the lines of said electromagnetic field when said probe pin is held on said chuck.