US2910645A - Mercury switch spinner head timing unit - Google Patents

Description

Oct. 27, 1959 F. G. BOUCHER ET AL 2,910,645

MERCURY SWITCH SPINNERVHEAD TIMING 11km 2 Sheets-Sheet 1 Filed Aug. 14, 1950 FIG.!

INVENTORS.

ATTORNEY Oct. 27, 1959 F. G. BOUCHER ETAL 2,910,645

MERCURY SWITCH SPINNER HEAD [TIMING UNIT Filed Aug. 14, 1950 2 Sheets-Sheet 2 FIG.2

FIG. 4

INVENTURSV- FRANK G. BOUCHER BEN W. SEWELL FIG. 5

ATTORNEY United States Patent C) MERCURY SWITCH SPINNER HEAD TIMING UNIT Application August 14, 1950, Serial No. 179,112

8 Claims. (Cl. 32428) The present invention relates in general to a centrifugal tester for fuze safety switches, and relates more particularly to a spinner for testing delayed action mercury switches.

In certain electrically actuated fuzes, delayed action safety switches of the mercury type are provided for keeping the firing circuits short-circuited until a predetermined time after the fuze has acquired spin. These switches depend upon the shifting of a mass of mercury from an initial location, in which it forms a short circui-t across the firing circuit, to another location to remove the said short circuit, such shifting being accomplished by centrifugally produced pressure that causes the mercury to flow through a resisting medium, such as a porous partition. In spite of care in manufacture, it is not possible to make these switches always identical in their delay characteristics, mainly because of certain unavoidable variations in the porous partition, and hence it is highly desirable to provide apparatus for determining the characteristics of the individual switches.

The object of the present invention, therefore, is to provide a spinner capable of simulating the spin to which such switches are subjected in actual service, to determine the response of the switch.

A more specific object is to provide a variable-speed centrifugal spinner into which a mercury switch may be inserted for convenient and rapid testing, and in particular for determining the time required to open the switch.

; Other objects and many of the attendant advantages of this invention will be appreciated readily as the same becomes understood by reference to the following detailed description, when considered in connection with the accompanying drawings, wherein:

.Fig. lis a view partly in elevation and partly in axial section, through a mercury switch spinner embodying the invention, showing also a diagram of the electrical indicating circuit, the drive clutch being in its disengaged po:

sition, and the drive motor being partly broken away;

Fig. 2 is a corresponding partly elevational and partly axially sectional view, showing the clutch in engaged position; a

. Fig. 3 is a cross-section through the spinner in the plane 33 of Fig. 1, including also a fragmentary section in a lower plane, through a bayonet joint;

Fig. 4 is an axial section, on a larger scale, through the spinner head and clutch, with a mercury switch in position to be tested; and

Fig. is a cross-section of the clutch, in plane 5-5 Fig. 4.

. Referring now to the drawings, and more particularly to Figs. 1 and 2, there is shown a spinner comprising a drive member in the form of a cup 1 mounted on a vertical shaft S of a suitable motor M, capable of rotating said cup at the desired speed of spin. For convenience, the apparatus may be mounted on a supp ort such as a table top T, through which the cup 1 projects as shown, so that the motor M or other power source is beneath the table, and thus out of the way. The cup 1 is secured to a reduced end of the shaft S as: by a headless set screw 2. The inside surface 3 of the cup preferably is cylindrical, so that the bottom of the cup is of the same diameter as the top. Near its upper end, the cup may have a sharply chamfered or frusto-conical portion 4 with an annular groove 5 therein, to collect any lubricating oil thrown out by the centrifugal force.

A cylindrical casing 6 with an attaching flange 7, and open at both ends, surrounds the portion of the cup 1 that extends above the table top. Pins 8 are secured in the wall of the casing 6, near its upper edge. A cap 9 having a depending flange 10 cooperates with the casing 6 as shown, and may be removably secured to said casing by means of bayonet slots 11 formed in flange 10, to engage over the pins 8.

A shoulder 12 of the cap 9 provides a seat for a metal washer 13 which fits within the flange 10 and is secured to the top of the cap 9 by screws 14. This washer 13 has a central opening preferably slightly larger than the bore of the cup 1, and, in conjunction with the top of the cap 9, provides support for several cylindrical pivoted clamping members 15, and an additional clamping member 16 which has a shaft 17 extending through the top of cap 9. The clamping member 16 is mounted eccentrically upon its shaft 17, to which is secured a hub 18 having a handle 19, the whole being so arranged that a substantially turn of the said handle in one direction or the other will. secure or release a switch spinner head 20 with respect to said cover 9.

The said spinner head 20 is shown in detail in section, in Fig. 4. It comprises an upper head 21 made of insulating material, for example, Lucite, with two alined radial bores 22 and 23 formed therein. The bore 22, which is usually of larger diameter than bore 23, serves to hold the mercury switch 24 that is to be tested, while bore 23 contains a counterweight 25, secured in place by screws 26, to dynamically balance the mass of the switch, to prevent excessive vibration when spinning. A helicoidal spring 27 is mechanically supported by a lug 28 on the counterweight 25, and serves as an electric contact element, to make connection with the center contact 24a of the switch 24.

In orderto provide a circuit connection through these parts, a conducting plate 29 is mounted on the Lucite head 21, and a central pressure-and-contact plate 30 is secured to the radially-inner end; of said first plate 29, thus establishing metallic contact from said plate 30 to the spring 27 and thence to the central inner contact 24a of the switchundergoing the test. p V I Beneath the upper head 21 is mounted a clutch .jaw assembly that comprises two oppositely located clutch shoes, 31 and 32. Theseshoes are connected to anintermediate metal cap 33 in such way thatthey causesaid cap to rotate whenever the shoes are rotated, and as shown this is accomplished by securing the shoes to separate hemicylindrical blocks 34 and 35, by means of screws 36. These blocks may be made of any suitable material, preferably of wood or a plastic, for greater lightness.

In order to allow the blocks to move toward and away from each other, they are, as seen in Fig. 4, mounted on studs 37 screwed into threaded bores 38 in the cap .33, said studs extending into bores 39 in the respective blocks, with a loose sliding fit, so that when the clutch assembly is rotated, the resulting centrifugal force will cause both blocks to slide radially outward, and force the clutch shoes 31 and 32 against the inner surface of the cup 1. H

An internally threaded lug 40 is provided in the center of the upper surface of cap 9, and receives a correspondingly threaded tube 41, closed at its upper end bya-threaded cap 42,of.insulating materiaLhaving a cenralopeni g .43- Anin ula ing bu h ng .44 seats on ,a shoulder at the bottom of lug 40, and an insulating tube 45 fits within the tube 41. A metal terminal plate 46 fits into the ,cap 42 and has ,a threaded stem 47 with a nut .48 thereon, :to serve as ,xaiibinding-post.

Mounted for axial movement within the tube 45 is a metal rod 4-9, which is guided by an enlargement '50 thereonditting in the-;bore of tube 45, and-by the opening 51 in bushingi. Saidflrod 49 is urged downward by a helical spring 52, :whose upper end bears against plate 46, and whose lower end bears against the enlargement 50. As shown, the enlargement 50 is most readily providedby a washer bearing against acotter-pin 53 passing through rod 49. At its lowerend rod 49 carries ahardened pressure element 54 (Fig. 4) such as a steel ball, for example, which bears :on the contact plate 3.0.

An electrical circuit is shown diagrammatically as connecting the terminal plate 46 .to the frame of the motor M and thus to shaft S and cup 1. Thiscircuitcomprises a wire 55 clamped under the nut 48, and leading through a current indicating instrument 56 to one terminal of a battery 57, the other terminal of said battery being connected to the frame of the motor M through a wire 58.

The operation is as follows:

The cap 9 and the parts carried thereby are disconnected from the cup 1 and housing 6 by a partial turn that releases the bayonet joints 8, 11. The switch 24 to be tested is pushed into the cavity 22 and held between center-contact spring 27 and a retainer spring 59, which make electrical contact respectively with the center contact 24a and the shell '24bof the said switch. Next the head 20 is pushed as far as it will go, against the thrust of spring 52 and then clamped between members 15 and 16 by means of handle 19.

The cap 9 is then secured to the housing 6 by means of the bayonet joints, whereupon the parts will all be found positioned as shown in Fig. 1. In this condition, the clutch members 31 and 32 are barely out of contact with the inner surface? of cup 1, and the spring 52 is under compression. 7

Upon releasing the head 20 by turning the handle 19, said spring will immediately push downward the head 20'and .the parts carried thereby, until the clutch shoes 31 and 32 rest on the bottom :60 of the cup 1, as shown in Fig. 2. Assuming that the shaft S is continuously turning the cup 1 at the desired speed, the clutch will at once start to rotate, due to friction of the clutch shoes on the bottom of the cup, and thus centrifugal force will come into play and force the clutch members outward firmly against the inner cylindrical surface of said cup, thereby rapidly accelerating the spin until the clutch is turning at the full speed of the cup. j I

At a certain speed ofrotation the switch 24, due to centrifugal force, will push the end of the retaining spring 59 outward and into electrical contact with the inner surface of cup 1, and thus will establish a circuit through the battery 57 and the indicating instrument 56. As the contacts 24a and 24b of switch 24 at that time are still shorted by the mercury 24c therein, the instrument 56 willshow a reading, indicating that current is flowing through said circuit. The instant at which this attaining of proper spin speed occurs may be noted by a stop watch or by automatic electric timing means, as preferred.

As the mercury 24c flows radially outward through the porous metal partition 24d, due to the spin,;the switch 24 should become unshorted within a preset interval, and such unshorting will become manifest by the return of the indicator reading to Zero. By timing thisevent, the delay performance of the switch may thus be clocked and checked. Attention is called to the fact that a test of a mercury switch, as just disclosed, is not injurious to the switch, which is restored to its initial condition after testing by reversing the switch 4 and thus applying centrifugal force in the proper direction to .force the mercury back to its original location. Thus all the switches that are to be actually used may be individually pretested, to make sure that each will operate as intended.

Obviously many modifications and variations of the present invention are possible :in the light of the above teachings. It is therefore to be understood that within the scope ofthe appended claims, the invention may be practiced otherwise than as specifically described.

What is claimed is:

'1. A spinner for centrifugally testing delayed-action switches, comprising a driving clutch member, means for rotating said member, a driven head, a holder for the switch to be tested, carried by said'head, a driven clutch member secured .to said head, means for causing said driven clutch member to engage the driving clutch member to be rotated thereby, and means providing an electric circuit through said switch while being rotated by said head, said circuit including also a continuity indicator and a source of electric energy.

2. A spinner as defined in claim 1, wherein the .driving clutch member is cup-shaped and whereinthe driven clutch member is at least partly within the said-driving clutch member, and has radially shiftable clutch shoes that become centrifugally engaged with the inner surface of said cup-shaped driving clutch member.

3. A spinner for centrifugally testing delayed action switches, comprising a two-part clutch, the outer part of said clutch being a cup, a sourceof mechanical power rotating said cup, the inner part of the clutchbeing :located within the cup and having a head designed to receive and hold the switch to be tested, a housing surrounding the cup, a cap detachably secured to the housing and resilient means carried by said cap and urging the two parts of the clutch into engagement when said cap is in place on the housing.

4. A spinner as defined in claim 3, wherein the cap has releasable clamping means for holding the inner-part of the clutch while said cap is disengaged from the housing.

5. A spinner for centrifugally testing delayed action switches, comprising a clutch having a driving member, means maintaining said member in continual uniform rotation at the desired spin rate, said clutch having a driven member, means maintaining said driven menrber initially out of engagement with said driving member, but operable to cause such engagement at will, means mechanically connected to said driven member for holding the switch to be tested with its longitudinal axis substantially normal to the axis of rotation of the clutch, means establishing an electrical connection to one terminal ofithe switch, centrifugal means establishing an electrical .connection to the other terminal of the switch when the driven member attains a predetermined speed, and electrical means coacting with said connections and including an indicator to show whether the switch is open or closed.

6. A spinner for centrifugally testing mercury delayed action switches, comprising, a support for a switch to be tested, means for rotating said support about an axissubstantially normal to the longitudinal axis of the switch,

an open electrical circuit including the switch, a source of electricity and an indicator for disclosing the behavior of said switch, and centrifugally actuated means for closing said electrical circuit only upon the attaining by the support of a predetermined rate of spin, thereby causing a flow of electricity from said source through the switch and wherein such flow continues until the switch opens-at the termination of its delay period.

7. A spinner arrangement as set forth in claim 6, wherein the means for rotating the support includes a driving member connected to a means for imparting rotational movement, a driven member -to which saidsupport is secured, and means maintaining said driven member out of engagement with said driving member but operable to cause such engagement, at will.

8. A spinner arrangement as set forth in claim 6, wherein said electrical circuit includes means establishing continuous electrical connection at one terminal of said switch, and means restraining the establishment of electrical connection at the other terminal of said switch until the predetermined rate of spin has been attained.

References Cited in the file of this patent UNITED STATES PATENTS

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