Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
1998-07-21
2001-06-12
Ramirez, Nestor (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S247000, C310S249000
Reexamination Certificate
active
06246144
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to assemblies including holders, or cards, for devices typically called carbon brushes and more particularly to holders for such brushes in which a lead functions not only to carry electricity to or from a brush but also to compress a spring or other mechanism used to bias the brush toward a rotating mechanism such as a commutator.
BACKGROUND OF THE INVENTION
U.S. Pat. No. 5,621,262 to Han, incorporated herein in its entirety by this reference, illustrates in its FIGS. 1 and 2 exemplary existing carbon brush holders. Both holders include (unlettered) caps, typically formed of plastic like material B of FIG. 1. Additionally shown in FIG. 2 are a brush C to which a lead is attached or embedded, with the lead in turn being connected to terminal G. An (unlettered) spring biases brush C (downward in the drawing) toward the surface of a rotating commutator, with the cap of the holder serving to compress the spring and effectively fix the position of one of its ends.
Also disclosed in the Han patent are various embodiments of a brush holder in which a flexible copper lead connects a brush to an element denoted a “brush terminal,” which brush terminal in turn contacts an element called the “lead terminal.” Like the brush holder of FIG. 2 of the Han patent, these other embodiments may contain a spring useful to bias the brush to contact the surface of a commutator. As illustrated in FIG. 15 of the Han patent, for example, the position of one end of the spring (the upper end shown in the drawing) is fixed by the brush terminal and underside of a cap screwed into the holder body, while its other end abuts a carbon brush. According to the Han patent, the cap is plastic and functions also to press together the lead and brush terminals.
Other commercially-available designs involving torsion springs include seventeen components, while those utilizing leaf and coil springs may contain as many as thirteen components. Typical coil-spring designs, for example, require not only a card and dual shunted brushes, but also two brush boxes, two coil springs, two lead wires, and four terminals (two to the brush boxes and two to external switches). Assembly of these coil-spring designs requires two repetitions of eight steps, including (1) inserting a spring into a brush box, (2) inserting a brush into the brush box, (3) bonding the shunt wire to the brush box, (4) bending the tab of the brush box to retain the brush and spring within the box, (5) bonding one end of a lead wire to a terminal (to the brush box), (6) bonding the other end of the lead wire to a terminal (to an external switch), (7) mounting the brush box assembly to a brush card, and (8) inserting a lead wire and terminal into a terminal of the brush box. Although assembly of existing leaf-spring designs necessitates two repetitions of fewer steps (six rather than eight), it nonetheless continues to require steps of bonding of lead wires and leaf springs to terminals or mounts and interconnecting the components via the terminals.
SUMMARY OF THE INVENTION
The present invention, by contrast, encompasses assemblies of brush cards or holders containing as few as nine components in some dual-brush embodiments and whose assembly is less complex than those techniques described in the preceding section. It additionally avoids any need to use a separate plastic cap such as that of the brush holders of the Han patent. Instead, a single lead wire (which could be or include a rod or other electrically-conductive device) not only electrically connects the brush and an external switch but also mechanically fixes the position of one end of a biasing mechanism such as a spring. By utilizing a lead wire with sufficient rigidity to withstand the expansive force of the spring without significant deformation and securing its position vis-a-vis the abutting end of the spring, the cards of the present invention provide simpler devices for holding functional carbon brushes.
Certain embodiments of the present invention contemplate placement of two conductive blocks such as brushes in a card or holder, each designed to contact the same rotating object (e.g. a commutator) in use. However, to complete an electrical connection between the commutator and an external device (such as but not limited to a switch), only a single block or brush is necessary. Thus, for a shunted brush, only a card, biasing means, and a lead wire are necessary to convey electricity reliably from the commutator to an external device (or vice-versa). Typically one end of the lead wire is connected to the shunt, while the other connects directly or indirectly (through, e.g., a terminal) to the external device.
In addition to being connected to the shunt, the lead wire of the present invention may also be secured to the brush card itself. Embodiments of the invention are designed for the lead wire to be the subject of an interference fit with a slot in the card. However, those skilled in the art will recognize that other means (including adhesive as one of multiple examples) may be employed to retain the lead wire in position respecting the brush card.
Assuming the biasing means is a coil spring, one end of the spring abuts the end of the brush opposite the commutator to allow the spring force to press against the commutator surface. The other end of the spring directly (or indirectly if appropriate) abuts the lead wire, typically in an insulated area of the wire. Because the lead wire is selected to withstand the expansive force of the spring without significant deformation, it provides an essentially immovable base against which the spring can expand in the opposite direction.
It is therefore an object of the present invention to provide a card or holder for an electrically-conductive brush.
It is also an object of the present invention to provide a brush card assembly which is simpler to assemble and requires fewer components than analogous conventional assemblies.
It is another object of the present invention to provide a brush card assembly which does not require any plastic cap.
It is an additional object of the present invention to provide a brush card assembly in which a lead wire not only electrically connects to the brush but also mechanically fixes the position of one end of a mechanism (such as a spring) used to bias the brush against the surface of a rotating machine such as a commutator.
It is a further object of the present invention to provide an assembly in which the lead wire is sufficiently rigid to withstand the expansive force of a spring without significant deformation.
It is yet another object of the present invention to provide an assembly in which the lead wire is secured to the brush card as, for example, by an interference fit.
Other objects, features, and advantages of the present invention will be apparent with reference to the remaining text and the drawings of this application.
REFERENCES:
patent: 3842302 (1974-10-01), Apostoleris
patent: 3967148 (1976-06-01), Walsh
patent: 4297605 (1981-10-01), Tak
patent: 5621262 (1997-04-01), Han
patent: 5686775 (1997-11-01), Veil et al.
patent: 78 05 597 (1978-06-01), None
patent: 1238113 (1960-11-01), None
International Search Report for International Application No. PCT/US99/14548.
Fitzner Scott L.
Hockaday Shepard L.
Nedriga Michael W.
Simmons Beecher G.
Dinh Le Dang
Kilpatrick & Stockton LLP
Morganite Incorporated
Ramirez Nestor
Russell Dean W.
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