US1760857A - Hair-spring-securing means for instruments - Google Patents

Description

L. BERG May 27, 1930.

HAIR SPRING SECURING MEANS FOR INSTRUMENTS Filed Sept; 17, 1928 ,jwuanfoz [2 1113 fizzy GUM we :24

,lvllay 27, 193i) ore ETD STATES PATENT OFFICE LCUZEF; BERG, 0F FLINT, MICHIGAN, ASSIGNOR TO A C SPARK PLUG COMPANY, 013 FLINT, MICHIGAN, A COMPANY OF MICHIGAN EAIR-SPRING-SECURING MEANS FOR INSTRUMENTS Application filed September 17, 1928. Serial No. 806,424.

This invention relates to measuring instruments and more particularly to the securing means for the hair spring functioning to restore the indicating means of such instruments to the zero position.

An object of the invention is to provide an improved securing means for the hair spring to obtain greater uniformity and efficiency.

As another object, the securing means is to such as to avoid twisting or deformation of the spring at its point of attachment.

Another object of the invention is to pro vide a securing means for the hair sprin whereby the hair spring at its end is hel concentrically in all positions of adjustment.

@ther objects and advantages will be understood from the following specification.

The invention is illustrated in the accompanying drawing, in which:

Figure 1 is an enlarged vertical central sectional view of a tachometer showing the hair spring friction adjuster applied;

Figure 2 is a vertical front elevation of the tachometer with the dial removed to show the adjuster in place;

Figure 3 is an enlarged fragmentary perspective view of the mounting bar showing the hair spring fastened at its end to the friction adjuster; and

Fi ire f is a perspective view of a modified orm.

Referring by reference characters to the drawing, numeral 12 is a cup-shaped frame having an apertured stem 11 for the passage of a rotor shaft 10. The rotor shaft is apertured to receive a driving connection with a suitable shaft, preferably a flexible shaft, which latter is to be connected to the rotatable member, the rate of rotation of which is to be measured.

The rotor shaft 10 may have an annular groove 3 to receive a key 5 carried bfy the stem 11 to prevent axial movement 0 said shaft 10. The stem 11 may be provided with a recess 21 containing a suitable wick 23 held in position by a cup 251 The purpose of the wick is to carry lubricant for lubricating the engaging surfaces of the stem 11 and shaft 10. An outer casing 27 houses the frame 12 and its sleeve 29 is sufficiently extended to retain both the key 5 and the cup 25, as shown in Figure 1., This casing 27 is secured to the frame by a plurality of bolts 31 and nuts 33. The bolts pass through lugs or projectlons 35 and 37 formed on the frame 12, as shown in Figure 2. There will be a third projection diametrically opposite lug 37.

pacing means 39 on the bolts between the casing 27 and frame 12, together with a washer 41 and an annular fabric washer 43 between the casing and the frame serve to secure these parts together in dust-tight relation.

An annular shoulder 45 in the frame supports a C-shaped magnet 13, the magnet having its interpolar gap adjacent bolt 31 in the projection 35. A temperature compensating plate of known characteristics is placed over the magnet poles. This is represented by numeral 46. To hold the magnet in position on shoulder 45 and to also hold the compensator on the poles of the magnet clip 46 is formed with an aperture by which it is dropped over bolt 31 and upon the extension 35. The washer 19 and nut 50 clamp the clip in position, the inner end of the clip firmly engaging the compensator 46.

For the purpose of calibration, a strip of brass or the like 131 may be clamped between parts 46 and 49 and extend substantially radially inward. The inner end of this strip of brass may be provided with a piece of magnetic material 133 being held to the brass strip by fastening means 135. By the provision of this calibrating means, the brass strip may be bent toward or from the plane of the magnet for the purpose of correcting the active magnetic field. Clips 46 on bolts 31 carried by lug 37 and by the diametrically opposite lug are also used. These last-named clips engage the flattened ends 53 of a bridge member 55 which is spilt as shown in Figure 2. The ends 53 of this bridge rest on the magnet and the clips hold the parts in assembled relation in an obvious manner.

A rotor 9 is secured in any convenient way to the upper end of shaft 10. As illustrated, the end of shaft 10 is reduced to receive on the shoulder so formed the opening within the rotor member 9 and, therea'lter, the en treme end oi the rotor shalt is crimped to hold the rotor in position. The rotor is formed with a plurality of radial arms 57. Within the openin oil the rotor shaft is a carrier 59 having in its lower end an end thrust bearing 61 and near its upper end a hole jewel 63. Secured by threads in the intermediate part of the bridge 55 is a second bearing carrier having a passage therethrough and a hole jewel 65.. The openings in the hole jewels 65 and 63 are in alignment and together with the end bearing 61 provide the necessary bearing support for a spindle 67 Secured by fastening means 69 to the spindle 67 is a metallic disc i l designed to serve as a drag member and to be rotated by the eddy currents against the tension of the hair spring 71 secured to the said spindle and to a rotatable adjusting member. Asflit is well known in such instruments, the degree of rotation of the drag disc it depends upon the rate at which rotor 9 travels, cutting as it travels the magnetic lines of force between the magnet poles.

A regulator arm 78 rests on bridge and is apertured to rotate about the extended end of carrier 65. This regulator arm extends across the bridge and on one side is bent down as at to and secured to the lower end of the bent-down portion 75 in a manner to be described is the outer end of spring 71. The other end oi the regulator arm is given a double bend and resiliently engages, by its extended end, forked as at 77, the underside of the bridge. Rotation of the regulator arm serves to vary the tension of spring 71.

At the upper end of the spindle is mount ed a part 7 9 carrying an indicating needle 16. The needle moves over a dial plate 19, the peripheral portion of which engages the marginal flanges of casing 27. In practice, there will be a glass cover and a fastening bezel, which parts are conventional and not illustrated,

The invention is more particularly concerned with the attachment of the outer end of hair spring 71. The down-turned end of the regulator arm is, as shown in Figure 3,

. provided with two slits 91 forming three tongues 93. The outermost of the tongues 93 are provided with bent portions, the direction of the bend being opposite that of a bend in the intermediate tongue 93. As shown best in Figure 3, an arc-shaped tubular member 94 is held between the bent portions of the tongues 93 which are sufliciently resilient to hold the member 94 firmly in position. The curvature of tube 94 corresponds with that of the hair spring. The end of the hair spring is inserted within the tubular member 94. By this means, the end of the hair spring has the same curvature as that of the major portion of the spring. After insertion in the tube,'the spring may be drawn through untilthe desired tension of the coil is had, after which the tube may be crimped to provide a permanent holding means for the end of the spring. After the sprin is firmly secured in the tube, the tube with t e end of the spring may be moved relative to the tongues 93, as by slightly pressing the tongues apart. In addition to this provision for adjustment, it will be understood that a fine adjustment may be thereafter made b the rotation of the regulator arm itself a out its pivot.

In the use of hair springs in connection with such instruments, it is customary to secure the end of the spring by a tapered pin, after which a fine ad ustment is bad by manipulating the regulator arm to increase or decrease the tension of the coil spring, this being accomplished by the rotation of the regulator arm on its pivot. In so securing the hair spring by wedging with the tapered pin, the concentricity of the coil at that point is destroyed, because of the flattening effect given to the hair spring at that point, producing a kink therein and more or less affooting the uniformity and efiiciency of the coil. By the means described, this disad vantage has been overcome. The hair spring is maintained erfectly concentric up to its very end and including its holding means. The hair spring is therefore not subject to twisting or deformation at its end when fastens Figure 4 represents a modified and some what simpler form which may be adopted when desired. In this form, the regulator arm is dispensed with and the hair spring supporting arm is formed as an integral part "or the supporting bar 97. The downwardly extending arm 98 is suitably split and the outer portions are angularly bent to form depressions 99, cutting down the length of these ends and leaving the center portion straight, its end extending further than the others, this arrangement facilitating the forcing apart of the ends to allow the end of the spring 71 to be pulled through. "With this arrangement, any adjustment of the hair spring coil may be quickly and easily made, after which the spring is permanently held in its adjusted position. This modified form employs a minimum number of parts since the conventional regulator arm and tapered pin are both dispensed with. It provides a means of reducing production cost, both in manufacture and assembly.

I claim:

1. In a measuring instrument, a rotary indicating member, a hair spring to restore said indicating member to a predetermined position, a retaining means for said spring holding an end of said spring in substantially concentric relation to the remainder of the spring, said retainings means including an are shaped tube, the end of the spring received within said tube.

2. In a measurin instrument, a rotary indicatin member, a air spring to restore said indicat ng member to a redetermined position, a retaining means or said spring holding an end of sald spring in substantially concentric relation to the remainder of the spring, said retaining means including an m arc-shaped tube, the end of the s ring received within said tube, said tube eing adjustable circumferentially within the retaining means.

3. In a measuring instrument, an indicating member, a hair sprin to restore said indicating member to a pre etermined position, retaining means for said hair spring, said retaining means having at least three resilient fingers, the outermost fin ers having bent portions, the end of the s rlng being received and held between said ngers, the intermediate finger having a reverse bend, an areshaped tube ositloned within the several bends and hel by the resiliency of said bent portions, the end of the spring being fixedly secured within said tube.

In testimony whereof I aflix m signature LOUI BERG.

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