Overload protector for electrical motors

Information

  • Patent Grant
  • 7023674
  • Patent Number
    7,023,674
  • Date Filed
    Saturday, October 13, 2001
    23 years ago
  • Date Issued
    Tuesday, April 4, 2006
    18 years ago
Abstract
An overload protection for electric motors, includes a one-piece suppression choke in which the connecting point to be broken is produced by means of at least one connecting point between the connection lug of the motor and a respective connecting element of the suppression choke, wherein the connection lug exerts an adjustable mechanical stress on the connecting point, thus reliably assuring a break when the softening temperature of the solder of the breaking point is reached.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a 35 USC 371 application of PCT/DE 01/03930 filed on Oct. 13, 2001.


BACKGROUND OF THE INVENTION

1. Field of the Invention


The invention is directed to an improved overload protection for electric machines such as electric motors and generators.


2. Description of the Prior Art


Electric machines, for example electric motors, frequently contain thermal circuit breakers, which protect the electric machine from destruction or fire in the event that its movement becomes jammed or restricted. Often a suppressor choke is used for this purpose, which is comprised of two parts soldered together at a connecting point, i.e. is comprised of a soldering point, using a solder with a particular melting temperature to form an intentional breaking point. When a carbon brush or a carbon brush cable heats the suppressor choke, this solder is heated and melts at a selected melting temperature. The windings of the suppressor choke exert a certain amount of initial stress on the suppressor choke and therefore on the connecting point so that when the soldering point softens, this connection should be broken. The electric circuit of the electric machine should then be permanently broken and the electric machine should be protected from being destroyed.


Frequently, however, the initial tension is not sufficient to assure a reliable breaking of the soldering point when the suppression choke is heated.


SUMMARY OF THE INVENTION

The overload protection for electric machines according to the invention has the advantage over the prior art that an electric machine can more reliably be protected from destruction or fire in a simple manner.


In order to exert the mechanical stress on the connecting point, it is advantageous to use a sheet metal strip that is electrically connected to a connecting element of the suppression choke.


Another advantageous embodiment of the connection lug is a helical spring.





BRIEF DESCRIPTION OF THE DRAWINGS

An exemplary embodiment of the invention is explained in detail herein below, with reference to the drawings, in which:



FIG. 1 shows a suppression choke according to the prior art,



FIG. 2 shows a suppression choke of an overload protection according to the invention disposed in a brush holder, and



FIG. 3 shows a partial detail of an overload protection according to the invention.





DESCRIPTION OF THE PREFERRED EMBODIMENT


FIG. 1 shows a suppression choke according to the prior art, which is embodied in two parts and is comprised of a first part 2 and a second part 4. The first part 2 and the second part 4 are connected at a breaking point 7 with a solder. The solder melts at a particular temperature. The solder is selected according to its melting temperature, depending on the intended use.


The reference numeral for the suppression choke according to the prior art will also be used for the suppression choke 1 according to the invention (FIGS. 2, 3).


The suppression choke also has a first electrical connecting element 5 and a second electrical connecting element 6 for an electrical connection in an electrical circuit.



FIG. 2 shows the suppression choke 1 of an overload protection according to the invention partially installed in a brush holder 9. For example, the first connecting element 5 is connected to a first electrical connection lug 11, which is integrated into the brush holder 9. The connection lug 11 produces the connection to the electrical circuit of an electric machine. For example, the first connection lug 11 exerts no mechanical stress on the first connecting element 5 and its connecting point.


The second connecting element 6 of the suppression choke 1 is likewise connected electrically and mechanically to a second electrical connection lug 13. The second connection lug 13 is connected to another electrical line in the brush holder 9. It is necessary to exert a force to move the free end 14 of the second connection lug 13 toward the second connecting element 6 in order to fasten it to the second connecting element 6.



FIG. 3 shows how the second connection lug 13 is connected to the second connecting element 6. A connecting point 15, produced by means of soldering, constitutes the mechanical and electrical connection between the second connecting element 6 and the free end 14 of the second connection lug 13.


Starting from FIG. 2, this occurs as follows: through the exertion of a mechanical force, the free end 14 of the second connection lug 13 is bent toward the second connecting element 6 (parallel to 18) and, while maintaining the force, the connection is produced, for example by means of soldering. After the connecting point 15 is produced, for example after the solder cools, the force on the second connection lug 13 can be withdrawn. The second connection lug 13 then exerts a mechanical stress in the axial direction 18 on the connecting point 15.


It is also possible to use both of the connection lugs 11, 13 to exert a mechanical stress on the respective connecting points 15.


The connection lugs 11, 13 can also be helical springs.


The connecting point 15 of the connection lugs 11, 13 and the connecting elements 5, 6 assumes the function of the breaking point 7 of the suppression choke according to the prior art.


In the overload protection according to the invention, this breaking point 7 is eliminated. Instead, a connecting point 15 is used, which is also present in the prior art. In the prior art, the breaking point 7, which protrudes beyond the dimensions of the suppression choke, often causes a ground contact in the pole housing when the connecting point 7 is broken. This disadvantage is eliminated in the overload protection according to the invention.


Because there are two connecting points of connection lugs and connecting elements, it is also possible for both to be embodied in the form of connecting points to be broken in the event of an overload.


The foregoing relates to preferred exemplary embodiment of the invention, it being understood that other variants and embodiments thereof are possible within the spirit and scope of the invention, the latter being defined by the appended claims.

Claims
  • 1. An overload protection for electric machines, comprising a suppression choke made from a coil of wire, wherein the wire which forms the coil of the choke extends from the coil at both ends of the coil and thus forms two electrical connecting elements each connected to an electrical connection lug of another electrical element at a respective connecting point,at least one of the connection lugs (11,13) exerting a mechanical stress away from the connecting point (15),the at least one connection lug being detachable from its respective electrical connection point when the suppression choke is heated as a result of its mechanical stress.
  • 2. The overload protection according to claim 1, wherein the at least one connection lug (11,13) is a sheet metal strip, which exerts a force on the connecting point (15) in the axial direction of the coil.
  • 3. An overload protection for electric machines, comprising a suppression choke made from a coil of wire, wherein the wire which forms the coil of the choke extends from the coil at both ends of the coil and thus forms two electrical connecting elements each connected to an electrical connection lug of another electrical element at a respective connecting point,at least one of the connection lugs (11,13) exerting a mechanical stress away from the connecting point (15),the at least one connection lug being detachable from its respective electrical connection point when the suppression choke is heated as a result of its mechanical stress, andthe at least one connection lug (11,13) is a sheet metal strip.
Priority Claims (1)
Number Date Country Kind
100 52 220 Oct 2000 DE national
PCT Information
Filing Document Filing Date Country Kind 371c Date
PCT/DE01/03930 10/13/2001 WO 00 9/8/2003
Publishing Document Publishing Date Country Kind
WO02/33721 4/25/2002 WO A
US Referenced Citations (10)
Number Name Date Kind
2491032 Burke Dec 1949 A
2804587 Bregman Aug 1957 A
4319126 Lujic Mar 1982 A
5306974 Bates Apr 1994 A
5637967 Kim Jun 1997 A
5896080 Chen Apr 1999 A
6198643 Gray Mar 2001 B1
6348851 Wyser et al. Feb 2002 B1
6737770 Sunaga et al. May 2004 B1
6876533 Ryan Apr 2005 B1
Foreign Referenced Citations (4)
Number Date Country
2 125 116 Nov 1972 DE
3 045 540 Jun 1981 DE
968 991 Dec 1950 FR
2 510 811 Feb 1983 FR
Related Publications (1)
Number Date Country
20040042147 A1 Mar 2004 US