US2271737A - Brush-lifting relay - Google Patents

Description

1942- R. M. HEINTZ BRUSH-LIFTING RELAY Filed Sept. 16, 1940 mmvrox, RALPH M. HEl/VTZ. BY

W -W ATTORNEYS.

Patented Feb. 3, 1942 BRUSH-LIFTING RELAY Ralph. .M. Heintz,

Palo Alto, Calif., assignor, by

mesne assignments, to Jack & Heintz, Inc., Cleveland, Ohio, a corporation of Ohio Application September 16, 1940, Serial No. 356,951

5 Claims.

This invention relates to relays for operating electric motors, and is particularly adapted for use in connection with impulse starters for air craft engines or in other situations where at most reliability must be combined with minimum weight. Where these devices are used in connection with impulse starters the source of supply is ordinarily a battery, the voltage is low and the current required to produce the necessary starting energy is correspondingly high. As I have set forth in my copending application, Serial No. 334,386, filed May 10, 1940, an operating relay of the ordinary type would require a contact pressure of the order of thirty pounds in order to carry the necessary current without overheating the contacts. Where the starting contact is made by the motor brushes against the commutator, however, a pressure of one or two pounds is entirely adequate, and this permits the use of much less energy to operate the relay, results in a much smaller relay, and thereby achieves a valuable saving in weight. The copending application above referred to covers one class of such brushrelay mechanism. The present mechanism is designed for motors of somewhat different characteristics and where such motors can be used presents some advantages over the device in my previous application.

Among the objects of the present invention are to provide a brush-operating mechanism having a minimum number of parts and particularly a minimum number of moving parts; to provide a motor-starting and operating relay of minimum weight; to provide a brush-operating mechanism which is simple to construct and assemble and is readily accessible for inspection or repair; and to provide a brush-operating mechanism which is quick and positive in action and which will operate two brushes orsets of brushes simultaneously, giving a double break in the circuit and resulting in minimum sparking at the instant of making or; opening the circuit.

Other objects of my invention will be apparent or will be specifically pointed out in the description forming a part of this specification, but I do not limit myself to the embodiment of the invention herein described, as various forms may be adopted within the scope of the claims.

Referring to the drawing:

Fig. 1 is an end view of the commutator housing of a motor embodying my invention, showing the commutator, brushes, and brush-operating relay. In this view the electrical circuits of the device are shown schematically.

Fig. 2 is a side view, partly in section of the apparatus of Fig. 1, the plane of section being indicated by the line 2--2 of Fig. 1.

Fig. 3 is a sectional View showing the solenoid and core construction used in Fig. 1.

The motor shown in the figure is a high speed D. C. motor of more or less conventional type, having a casing l enclosing field windings 2 and the core, which are not shown in detail as they are well known constructions and conventional in form insofar as they relate to the present invention. The armature 3 is also merely indicated since it is electrically a standard type. The commutator 4 is also generally of known construction, although it is somewhat large with respect to the size of the armature, in order to carry the relatively high amperage and low voltage current required to produce the necessary power in the high speed motor. The motor windings, both on stator or field and armature, may be of any of the known types which permit the brushes to be mounted at right angles; in general this means a four pole motor operated with a single pair of brushes, preferably with equalizing connections between the commutator segments, but these factors 'are all well known in the art.

A commutator and brush housing 5 carries the bearings 1 for the motor shaft 9. The housing- 5 is generally of horseshoe shape, the open end of the horseshoe being closed by a cover plate I!) which supports the entire brush mechanism and also carries a conduit connection H through which the leads to the motor are run.

A plunger magnet coil I2 is supported on the cover plate It) with its axis mounted radially with respect to the commutator 4. A fixed core I3 is secured in the upper end of the coil. This core preferably has a generally conical inner face I4, and is traversed by a longitudinal slot through which passes a sliding plate [5 of nonmagnetic material, such as brass or duralumin, whose lower end is secured to a sliding core H. The upper end I9 of the core is concavely conical to cooperate with the convexly conical end of the core l3. Both cores are provided with counterbores- 20 and 2| respectively and the plate I5 is provided with a slot 22 coacting with the counterbores to receive a compression spring 23 which normally forces the two cores apart and retracts the upper end of the plate IS.

The two brush holders 24 and 25 are conventional in type, comprising boxlike channels wherein the brushes 29 and 30 can slide. The brushes are urged against; the commutator by springs 3| carried by studs 32 which are mounted on ears 33 projecting from the brush holders.

A mounting lug or plate 34 projects from each of the brush holders perpendicular to the plane of the brush and to the axis of the commutator, and these lugs are secured respectively on opposite sides of the plate l5, being insulated therefrom by layers of sheet material 35. The preferred method of fixing the mounting lugs to the plate [5 is by insulated rivets 36. As may be seen in the drawing the structure of the brush holder assembly is symmetrical about the axis of the soil and plunger, the brushes being perpendicular to each other and at 45 to the axis of the magnet and the plate IS.

The brushes are connected to terminals 39 and 40 respectively, having the customary pigtail connections 4|. The remainder of the connections are shown schematically, the terminal lug 39 connecting through the field coils 42 to ground, while the terminal 40 connects to a power source 43 (usually a battery as shown) and thence to ground. A branch circuit 44 connects through an actuating push button or switch 45 to one end of the plunger magnet coil I 2, and the other end of this coil connects to the grounded case.

When the switch 45 is closed, completing the circuit 44 through the plunger magnet, the latter is actuated, attracting the core l1, compressing the spring 22, and forcing the two brushes into contact with the commutator. The construction of the plunger magnet itself tion of the plunger, and brings the mechanism to rest with the brush holder and brushes positioned radially with respect to the commutator. The wide flat plate l5, operating in the slot in the cores l3, prevents the rotation of the plunger in th core and prevents angular displacement of the brush holder and brushes. The wide dimension of the plate I 5 being in the plane of rotation of the commutator, the plate is extremely rigid in this dimension. No stresses are applied to this plate parallel to the commutator axis, and its relatively small dimension in this direction is therefore of no disadvantage; if it be made of stiff brass or, preferably, dural or some similar light, stiif alloy, it will have adequate strength combined with lightness. The entire mechanism, therefore, combines light weight with great simplicity, thus resulting in economy of fabrication and assembly and maximum reliability of performance.

Although primarily designed for two-brush motors, it is obvious that by duplicating the lifting mechanism any number of pairs of brushes may be used.

I claim:

1. The combination with an electric motor having a commutator of a brush-lifting and relay mechanism comprising a magnet coil radially disposed with respect to said commutator, a plunger slidably mounted within said coil and secured against rotation therein, a pair of brush holders mounted on the end of said plunger, the axes of said brush holders being disposed rectangularly with respect to each other and at 45 with respect to the axis of said plunger, the latter being so positioned as to dispose each of said axes radially with respect to said commutator when said plunger is fully attracted, resilient means for normally retracting said plunger from limits the mosaid commutator, brushes mounted in said brush holders and a switch for energizing said coil to attract said plunger and bring said brushes into operating contact with said commutator.

2. The combination with an electric motor having a commutator of a brush-lifting and relay mechanism comprising a magnet coil radially disposed with respect to said commutator, a fixed core positioned in the end of said coil adjacent said commutator and having a slot formed therethrough, a sliding core in the opposite end of said coil, a non-magnetic plate fixed to said sliding core and extending through said slot, 2. pair of insulated brush holders mounted on the end of said plate in mutually rectangular positions and symmetrically with respect to said plate, brushes carried by said brush holders, and connections between said motor and said brushes for completing a circuit through and operating said motor when said sliding core is attracted, said coil and core being positioned to bring said brushes radially into contact with said commutator when said core is in fully attracted position.

3. The combination with an electric motor having a commutator of brush holder and energizing relay mechanism comprising a plunger magnet including a coil positioned radially with respect to said commutator, a fixed core in the end of said coil proximal to said commutator and a sliding core in the opposite end of said coil, said fixed core having a longitudinal slot therethrough, and both of said cores being counterbored in their abutting ends, a nonmagnetic plate secured to said sliding core and extending through the slot in said fixed core, a slot in said plate cooperating with said counterbores to receive a compression spring for retracting said sliding core and plate, a pair of insulated brush holders secured to said plate in mutually rectangular position, brushes mounted in said brush holders, said plunger magnet being so positioned as to bring said brushes into contact with said commutator in radial relation thereto when said sliding core is fully attracted, and connections to said brushes and said motor to energize the latter when said brushes ar in contact with said commutator.

4. Apparatus in accordance with claim 2 wherein said slot is disposed in a plane perpendicular to the axis of said commutator and said brush holders are secured to said plate by lugs riveted on opposite sides thereof.

5. The combination with an electric motor having a commutator, of a brush-lifting and relay mechanism, comprising a magnet coil radially disposed with respect to said commutator, a plunger slidable in said coil, brush holder supporting elements rigidly mounted on the end of said plunger, brush holders mounted on said supporting elements, resilient means to normally retract the plunger from the commutator and brushes mountedin said brush holders, the latter being so disposed that upon contact with the commutator their axes are radially positioned with respect to said commutator, when the plunger of the magnet coil is fully attracted by energization of said coil.

RALPH M. HEINTZ.

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