초록 ▼

A single or composite lifting electromagnet has several cores whose poles can attract round, elongated or otherwise configurated ferromagnetic objects. The cores are surrounded by and/or flank discrete sensors in the form of Hall generators or induction coils which are provided in addition to exciti

A single or composite lifting electromagnet has several cores whose poles can attract round, elongated or otherwise configurated ferromagnetic objects. The cores are surrounded by and/or flank discrete sensors in the form of Hall generators or induction coils which are provided in addition to exciting coils for the cores. The sensors are disposed centrally of or mirror symmetrically around the center of the electromagnet, and the purpose of the sensors is to generate signals in response to changes of the electromagnetic field to thereby facilitate automatic guidance of the electromagnet toward an optimum position with reference to an object which is to be lifted and transported, e.g., to the treating station of a machine tool.

대표청구항 ▼

1. A lifting electromagnet, comprising a plurality of cores defining poles arranged to attract and support at least predominantly ferromagnetic objects; exciting coil means for said cores; and sensor means for generating control signals in response to influencing of the magnetic field of the electro

1. A lifting electromagnet, comprising a plurality of cores defining poles arranged to attract and support at least predominantly ferromagnetic objects; exciting coil means for said cores; and sensor means for generating control signals in response to influencing of the magnetic field of the electromagnet by an at least predominantly ferromagnetic object, said sensor means being disposed at least substantially centrally with reference to the poles of said cores and comprising a plurality of discrete sensors which are symmetrical to one another with reference to the center of the electromagnet, said sensor means further comprising at least one induction coil surrounding one of said cores. 2. The electromagnet of claim 1, wherein said sensors include a sensor which is disposed between two poles. 3. The electromagnet of claim 1, further comprising means for regulating the supply of energy to said exciting coil means so that the magnetic force is less while the electromagnet is in the process of attracting an object and greater while the object adheres to the electromagnet. 4. The electromagnet of claim 1, wherein the number of said poles exceeds two. 5. The electromagnet of claim 1, further comprising means for supplying direct or alternating current to said exciting coil means. 6. The electromagnet of claim 1, wherein the total number of said poles is divisible by three and further comprising a source of multiphase current connected with said exciting coil means. 7. A composite lifting electromagnet comprising a plurality of discrete lifting electromagnets which are disposed one behind and/or one next to each other, said electromagnets having cores with poles of different polarities, exciting coil means for said cores, sensor means for generating signals in response to influencing of the electromagnetic fields of the respective electromagnets by ferromagnetic objects, said sensor means being disposed at least substantially symmetrically with reference to the center of the composite electromagnet, means for connecting the cores of said discrete electromagnets to one another and additional exciting coil means carried by said connecting means. 8. The composite electromagnet of claim 7, wherein said discrete electromagnets are separated from each other by air gaps. 9. The composite electromagnet of claim 7, wherein said discrete electromagnets are separated from one another by partitions consisting of nonmagnetic material. 10. The composite electromagnet of claim 7, wherein said sensor means comprises a plurality of discrete sensors disposed between the poles of the cores of neighboring discrete electromagnets. 11. A lifting electromagnet, comprising a plurality of cores defining poles; exciting coil means for said cores; sensor means for generating signals in response to influencing of the magnetic field of the electromagnet by an at least predominantly ferromagnetic object, said sensor means being disposed at least substantially centrally with reference to the poles of said cores and between two poles; and means for varying the distance between said poles. 12. The electromagnet of claim 11, wherein said sensor means comprises at least one induction coil. 13. A lifting electromagnet, comprising s plurality of cores defining poles, at least one of said cores comprising at least two sections one of which is movably telescoped into the other section; exciting coil means for said cores; and sensor means for generating signals in response to influencing of the magnetic field of the electromagnet by an at least predominantly ferromagnetic object, said sensor means being disposed at least substantially centrally with reference to the poles of said cores and comprising a sensor which shares the movements of said one section. 14. The electromagnet of claim 13, wherein said one section is freely movable with reference to said other section. 15. The electromagnet of claim 13, further comprising means for moving said one section with reference to said other section. 16. The electromagnet of claim 15, wherein said moving means comprises an electric motor. 17. The electromagnet of claim 15, wherein said moving means comprises a fluid-operated motor. 18. A lifting electromagnet, comprising a plurality of cores defining poles; exciting coil means for said cores; and sensor means for generating signals in response to influencing of the magnetic field of the electromagnet by an at least predominantly ferromagnetic object, said sensor means being disposed at least substantially centrally with reference to the poles of said cores and comprising a plurality of discrete sensors connected in a bridge circuit. 19. The electromagnet of claim 18, wherein said sensor means comprises at least one semiconductor. 20. A lifting electromagnet, comprising a plurality of cores, said cores including a first core and a second core, said first and second cores respectively having first sections disposed at a first distance from one another and second sections disposed at a lesser second distance from one another; exciting coil means for said cores; and sensor means for generating signals in response to influencing of the magnetic field of the electromagnet by an at least predominantly ferromagnetic object, said sensor means being disposed at least substantially centrally with reference to the poles of said cores. 21. A lifting electromagnet, comprising a plurality of cores defining poles; exciting coil means for said cores; sensor means for generating signals in response to influencing of the magnetic field of the electromagnet by an at least predominantly ferromagnetic object, said sensor means being disposed at least substantially centrally with reference to the poles of said cores; and means for supplying direct or alternating current to said exciting coil means, said exciting coil means comprising a plurality of parallel windings which are connected in parallel for operation with alternating current and in series for operation with direct current. 22. The electromagnet of claim 21, further comprising means for connecting said windings with a source of direct current while the electromagnet supports and/or transports an object and for connecting said windings with a source of alternating current shortly before or shortly after disengagement of the transported object from the poles of the electromagnet. 23. The electromagnet of claim 22, wherein said connecting means is arranged to increase the amplitude of the magnetic field for a short interval of time upon switching over from operation with direct current to operation with alternating current. 24. A lifting electromagnwt, comprising a plurality of cores; a permanent magnet disposed between said cores; exciting coil means for said cores, said exciting coil means being disposed between said cores; a current source for said exciting coil means; means for changing the polarity of said exciting coil means; means for regulating the strength of the current which is supplied by said source; and sensor means for generating signals in response to influencing of the magnetic field of the electromagnet by an at least predominantly ferromagnetic object, said sensor means being disposed at least substantially centrally with reference to the poles of said cores. 25. A lifting electromagnet, comprising a plurality of cores defining poles, said poles including at least one pair of poles disposed in mutually inclined planes; exciting coil means for said cores; and sensor means for generating signals in response to influencing of the magnetic field of the electromagnet by an at least predominantly ferromagnetic object, said sensor means being disposed at least substantially centrally with reference to the poles of said cores. 26. The electromagnet of claim 25, wherein the planes of said pair of poles make an angle which equals or approximates 120 degrees.