US2141445A - Magnetic speedometer - Google Patents

Description

Dec. 27, 1938. T PAUL 2,141,445

MAGNETIC SPEEDOMETER Filed Jan. 13, 1956 flafo fai. jar/11 e11 h Jaye/W as 1455/72 63 5.

Patented Dec. 27, 1938 PATENT OFFICE MAGNETIC SPEEDODIETER Thorolf Paul, Chicago,

Ill., assignor to Stewart- Warner Corporation, Chicago, 111., a corpora tion of Virginia Application January 13, 1936, Serial No. 58,866

6 Claims.

This invention relates to speed-indicating and measuring instruments for vehicles, commonly termed speedometers, and its object is to provide improved features of construction contributing to compactness of design, efficiency of operation and economy in manufacture. The invention thus consists in such features and elements of construction as shown in the drawing and hereinafter described, and as indicated by the claims.

In the drawing: Figure 1 may be considered a top plan view of the assembly of the internal mechanism of a speedometer embodying this invention.

Figure 2 is an elevation taken partly in section, as indicated at line 2-2 on Figure 1.

Figure 3 is a transverse detail section taken as indicated at line 33 on Figure 2.

Figure 4 is a fragmentary side elevation to show the supporting means for the odometer dials.

t may be understood that, as seen in Figure l, the mechanism is viewed from a position opposite the plane of the dial plate but with the dial plate and outer casing omitted. The mechanism is supported in a die cast frame i which, as shown, is a single casting and includes mounting means for the speed-indicating mechanism and for the odometer or travel-registering ele- Sil? ments. The frame includes a journal bearing 2 for the shaft 3 by which the permanent magnet l is revolved. This shaft includes the usual constricted portion at 5 by which the bore in its lower end is given a squared cross-section for SI intermembering with a suitable squared terminal of a flexible drive shaft, not shown. At its upper end, as seen in Figure 2, the shaft is reduced at 6 to engage a central aperture in a drawn sheet metal carrier cup '1 and is riveted over for permanent attachment thereto. The annular flange of the cup I fits snugly in the annular magnet 4 and its upper edge may be offset outwardly at several points, as seen at 8 in Figure 3, for ensuring a strong frictional hold.

One of these offsets, indicated at 8 engages in the gap between the poles of the ring-shaped magnet 4. A compensating shunt member 4 of nickel steel alloy, such as "Monel is placed in position just lapping the poles at this gap and in contact with the ends of the magnet 4 to compensate for temperature changes, and a pocket for this pole-piece is formed in the cylindrical wall of the cup 1 below the offset at 8*.

This magnet is made from flat strip stock bent around an axis so that the larger dimension of its cross-section extends parallel to the axis of the cylinder thus formed. By bending the stock from a strip in the original longitudinal arrangement of its fibers is preserved from end to end. and thus from pole to pole of the magnet, improving the magnetic qualities of the element as compared with one which is stamped from sheet stock or merely cut from a block of material.

The frame I is formed with a. cylindrical cavity 10 which is concentric with the axis of the shaft 3 and its magnet 4. A pressed metal bearing support in the form of a cup 9 is set into this cavity Ill with its annular-skirt closely adjacent the magnet 4 but with ample clearance to permit the magnet to revolve freely. The lower edge of the skirt is flared outwardly in a flange H which fits snugly in the cavity I 0 and thus centers the cup 9 therein. The transverse wall of the cup is depressed at it and carries at its center a metallic plug it into which is set a jewel bear= ing it for the lower end of the spindle 15. The spindle carries the non-magnetic drag element in the form of a cup l6 which may he of aluminum and whose transverse web ii is fixed to a two-part hub whose member i8 fits tight on the shaft I5 while its applied ring 19 cooperates with the flange of the part I8 to clamp the central part of the web it. A stop lug ll projects from the web it to engage with a fixed stop lug iz struck out of the web I2 of the cup 9. The skirt of the cup encircles the annular portion of the supporting element 9 but with free running clearance so that the drag element may respond in the usual manner to the rotation of the magnet 3.

Just outside the aluminum cup 16 a steel field cup 20 is fitted frictionally into the cavity 10 so as to concentrate the magnetic fiux of the magnet 4, drawing it through the skirt and through the transverse wall or web of the drag element iii. The cavity H] has a groove Ill and the field cup 20 has a lug 2B fitting in the groove to anchor the field member against rotation; and a slot 20 in the skirt of the cup 20 adapts it to be sprung slightly and forced tightly into the socket If]. This adapts it to support the anchorage for the hair spring 2i which is employed to bias the drag element 16 toward its zero position, and to yieldingly impose the magnetic drag of the magnet 4 when the latter is revolved. The field cup 20 is apertured at the center of its web, and a collar 22 is rotatively clamped in the aperture by lugs 23 bent around the rim of the aperture, as seen in Figure 2.

An outwardly extending arm 24 integral with said collar, provides an anchorage for the outer end of the hair spring 2| which is threaded into a socket formed by oppositely offset portions 25 in the upstanding end of the arm 24 a tapered pin 26 being driven in to secure the end of the spring. A second arm 2! extending radially from the collar 22 is accessible after the instrument has been assembled and may be provided with an aperture 27 for conveniently engaging it by means of any suitable tool for rotatively adjusting the collar 22 to vary the final tension of the hair spring 2|; the frictional grip of the lugs '23 will hold the collar at any adjusted position. This provides a simple and effective means for final calibration of the instrument.

The upper end of the spindle i is shown re-- duced at 28 and journaled in a jewel bearing 29 carried in a metallic cup 30 which is fixed in the flange 3| of a stamped cross-bar 32 which extends across the top of the frame and is secured thereto by screws 33 entering the outturned lugs 34 of the frame. A suitable indicating needle 35 is provided with a hub 36 which frictionally engages the reduced end 28 of the spindle |5. It will be understood that the fiat extensions 31 of the cross-bar 32 will support a suitable dial plate (not shown) in a plane below that of the needle 35 and that any suitable form of external enclosing case may be applied, or the instrument may be mounted without any separate case back of an instrument panel board, and protected by some form of general enclosure attached to the panel board.

The odometer train consists of several cylindrical dials 4|! adapted to register total milage, and a lesser number of separately mounted dials 4| which are intended for registering individual trips, and are adapted to be reset to zero position at will. The resetting mechanism is of familiar construction, including a shaft 43 having a knurled finger grip 44 and carrying a gear 45 adapted to mesh with the drive gear 46 of the trip dial series when the shaft 43 is slidably moved in its bearings for this purpose. The conical end 41 of the shaft 43 acts as a cam against the rounded end 48 of the stub shaft 49 which carries the gear 45, thus shifting the latter automatically into the proper plane for meshing with the gear 45 and disconnecting it temporarily from the gear 5|], from which both sets of odometer dials are normally driven.

The dials 40 are supported loosely on a shaft 5| and the dials 4| are supported on a shaft 52. The frame includes an upstanding web 53 having a hole to receive the end 54 of the shaft 5|. The shaft 52 terminates within the elongated hub 55 of the right hand dial of the trip series. At their opposite ends the shafts 5| and 52 enter notches 56 in the upstanding web 5'! of the frame, and the reduced ends of the shafts are retained in apertures in the ends of a fiat spring member 58 secured to the web 51 by a single fastening 59 at the middle of its length. This greatly simplifies the assembly of the odometer dials in the frame, and also permits either of them to be readily removed for repair, if necessary. Each train includes spacer disks 60 disposed between adjacent dials, and serving to support idler gears (not shown) which transmit motion from one dial to the next in a familiar manner. The spacers 60 are formed with bifurcated lugs 6| extending beyond the periphery of the dial cylinders and anchored against rotation by engagement with rods 62 which may be removably carried in the frame webs 53 and 51 in the same manner as the shafts 5| and 52.

I claim:

1. In a magnetic instrument, a permanent magnet composed of a piece of bar stock completed for use by bending alone into cylindrical form with a gap between its ends, said bar having a width at least three times its thickness and being bent so that its width comprises the length of its cylindrical form while its thickness is disposed radially thereof. means supporting said magnet for rotation about the axis of its cylindrical form, and a non-magnetic drag element journaled to rotate independently of the magnet about the same axis, and having a portion extending in closely spaced relation to the cylindrical surface of the magnet with uniform clearance between said magnet and said portion of the drag element throughout their relative rotational movements.

2. In a speedometer, a frame casting, a rotary magnet of annular form, a shaft fixed to the magnet, the frame casting having a journal bearing for said shaft and a larger co-axlal recess in which the magnet rotates, a non-magnetic drag cup encompassing the magnet, a non-magnetic bearing cup disposed between the magnet and said drag cup and formed with a foot flange fitted in the recess to center said bearing cup, a spindle for the drag cup and a bearing for the spindle carried fixedly at the center of the hearing cup, said frame casting having supporting members extending above the bearing cup, a bar secured to said members with a second bearing for the spindle carried by said bar, the bar having end portions offset into a plane above that of the spindle bearing for positioning a dial plate.

3. In a speedometer, a frame casting, a rotary magnet of annular form, a shaft fixed to the magnet, the frame casting having a journal bearing for said shaft and a larger co-axial recess in which the magnet rotates, a non-magnetic drag cup encompassing the magnet and a field member in the form of a cup of magnetic metal fitting snugly into said recess in the frame casting and extending over the drag cup, said cup having a slot extending through its cylindrical portion and into its transverse web to render the cup yielding so as to be held in the recess by its own resilience.

4. In a speedometer, a frame casting, a rotary magnet of annular form, a shaft fixed to the magnet, the frame casting having a. Journal bearing for said shaft and a larger co-axial recess in which the magnet rotates, a non-magnetic drag cup encompassing the magnet and a field member in the form of a cup of magnetic metal fitting snugly into said recess in the frame casting and extending over the drag cup, said recess having a slot and said field cup having 3. lug projecting into the slot to anchor it against rotation, the field cup having a central opening in its web, a spindle for the drag cup extending through said opening, a collar fitted in the opening with portions frictionally gripping the web of the cup, a biasing spring of spiral form secured at its inner end to the spindle, an anchorage for the outer end of said spring carried by the collar, and an arm on the collar extending radially to facilitate rotative adjustment thereof for varying the tension of the spring.

5. In a speedometer, a frame casting, a rotary magnet of annular form, a shaft fixed to the magnet, the frame casting having a journal bearing for said shaft and a larger co-axial recess in which the magnet rotates, a non-magnetic drag cup encompassing the magnet and a field member in the form of a cup of magnetic metal fitting tightly into said recess in the frame casting and extending over the drag cup, the cup having a central opening in its web, a spindle for the drag cup extending through said opening, a collar fitted in the opening frictionally gripping the cup, a biasing spring of spiral form secured at its inner end to the spindle, an anchorage for the outer end of said spring carried by the collar, and an arm on the collar extending radially to facilitate rotative adjustment thereof for varying the tension of the spring.

6. In a magnetic instrument a permanent magnet composed of a piece of bar stock bent into cylindrical form with a gap between its ends, said bar having a width at least three times its thickness, and being bent so that its width comprises the length of its cylindrical form while its thickness is disposed radially thereof, means for rotating said magnet about the axis of its cylindrical form, and a non-magnetic drag cup journaled for rotation independently of the magnet but disposed in co-axial relation thereto with its flange or skirt extending adjacent the cylindrical wall of the magnet throughout the length thereof.

THOROLF PAUL.

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