US2698417A - Galvanometer construction - Google Patents

Description

Dec. 28, 1954 C, M HATHAWAY 2,698,417

GALVANOMETER CONSTRUCTION Filed Sept. 14, 1950 @haak MK2/Mayday United States Patent O GALVAN OlVIETER CONSTRUCTIDN Claude M. Hathaway, Littleton, Colo., assiguor to Hathaway Instrument Company, Denver, Colo., a corporation of Colorado Application September 14, 1950, Serial No. 184,868

3 Claims. (Cl. 324-97) The present invention relates to a galvanometer construction whereby a large number of galvanometer elements can be located in a relatively small space.

For certain oscillograph purposes it is desired to provide a relatively large number of oscillograph elements or galvanometers so as to provide a compact arrangement. It further is desired to provide moving elements, which may be damped with oil, if desired. In the past arrangements of this kind have employed a single relatively large permanent magnet with individualized pole pieces for the several galvanometer elements.

In order to Yprovide for convenient replacement of any element deemed to be defective or inaccurate, it would be desirable to provide an improved galvanometer wherein connections are readily made thereto. It furthermore would be desirable to have an improved magnet design which is not quite so bulky and which provides pivotedadjustment of the galvanometer element in a vertical plane.

Other and further objects of the present invention will subsequently become apparent by reference to the following description taken in conjunction with the accompanying drawing wherein:

Figure l is an end view of a galvanometer constructed in accordance with the present invention;

Figure 2 is a front view of the multi-element galvanometer shown in Figure l.

Figure 3 is an enlarged detailed cross-sectional view of a galvanometer element employed in the structure shown in Figures l and 2;

Figure 4 is an enlarged cross-sectional view of a portion of the device shown in Figure 3 as seen at right angles to that ligure;

Figure 5 is a horizontal cross-section as seen in the direction of the arrows along the line 5-5 of Figure 4; and

Figure 6 is a horizontal cross-section as seen in the direction of the arrows along the line 6-6 of Figure 4.

Referring to Figures l and 2 there is shown a multielement galvanometer having end plates 11 and 12 and a front plate 13. These plates are suitably secured to a base 14 by means of fastening means such as screws 15. The base 14 has a stepped portion 16 so as to serve as a locating device for a plurality of pole pieces 17 and 18. The pole piece 17 carries a permanent magnet element 19 having a curved surface 21. The pole piece 18 carries a permanent magnet 22 having a curved surface 23. The curved surfaces 21 and 23 comprise segments of a cylindrical surface having an axis passing through the center of a galvanometer element 24. The galvanometer element 24 comprises a non-magnetic housing 25 carrying a magnetic cradle 26 having surfaces complementary to the curved surfaces 21 and 23 of the permanent magnets. suitably supported between the end plates 11 and 12 is a terminal block 27 provided with a plurality of binding posts 28 and 29. Two such binding posts are provided for galvanometer element 24. The block 27 carries a threaded adjusting screw 31, which engages an upright post 32 carried by the cradle 26. The upper end of the post 32 is connected to a spring 33, which in turn engages a lug on the block 27. Thus the spring biases the element 24 to a certain position as determined by the adjusting screw device 31. By means of diierent adjustment the cradle 26 is rocked in the cooperating surfaces of the permanent magnets 19 and 22. In order to provide for adjustment of the element 24 through a horizontal angle a rotatable post 34 is provided which 2,698,417 Patented Dec. 28, 1954 carries a gear sector 35 for engagement with'a gear sector mounted on the casing 25 of the element 24.

Figures 3 to 6 inclusive show the details of construction of the galvanometer element contained within the casing 25. At the lower end there is provided an insulator 36 which carries a threaded rod 37, which is engaged by a nut 38 bearing against an insulated washer 39. The inner end of the rod 37 terminates in a hollow bifurcated portion 41 to provide a socket for a plug connector.

At the opposite end of the tube 25, which is of nonmagnetic material such as brass, an internal threaded portion 42 is engaged by a cap 43, which bears against a packing ring 44. The cap 43 is arranged to be removed so that access may be had to the element carried within the casing 25. Within the cap 43 there is an insulator bushing 45 carrying a terminal 46 having at its lower end a hollow bifurcated portion 47, which serves as a socket member. The upper end of the member 46 is electrically connected to a conductor 48.

Between the bifurcated members 41 and 47 there is located a generally rectangular frame 49 having a rectangular central opening 51. The frame 49 at its top has a central aperture fitted with an insulating sleeve 52 and carrying an electrical connector 53, which tits into the bifurcated socket 47. The electrical connector 53 is connected to one wire 54 of the suspended galvanometer element. At the lower end of the wire 54 there is provided a bale 55 carrying a mirror 56. The lower end of the bale 55 is connected to the movable coil 57, which in turn is connected to a wire 58. The wire 58 is connected to a spring 59 which is fastened to a connector 61 passing through an insulated sleeve 62 in the central aperture at the bottom of the rectangular frame 49. The lower end of the connector 61 engages the bifurcated socket 41.

In the proximity of the moving coil element 57 the outer tube 25 is provided with magnetic inserts to form two pole pieces 63 and 64 shown in Figure 6. The pole pieces 63 and 64 t into the central opening in the cradle 26 Immediately above the pole pieces 63 and 64 there is provided a lens 65 carried by a lens supporting structure 66 inserted into an opening in the tube 25. At the rear of the tube 25 there is located a cylindrical segment 67 having at its lower end a gear sector 68. This gear sector is the one which is engaged by the gear sector 35 of the adjusting member 34.

In order to replace any of the various galvanometer elements of the structure illustrated in Figures l and 2, the entire cylindrical assembly 24 may be removed. Thereupon access may be had to the galvanometer element per se contained within the tube 25 by removing the cap structure 43. Then by grasping the rectangular frame 49 or the upper end of the connector 53, the frame 49 may be withdrawn from the tube and out of engagement with the lower socket connector 41. 'Thus it will be appreciated that a compact structure is obtained, which is readily removed for examination or for repair.

If desired, the inside of the sleeve or tube 25 may be tilled with oil in order to provide oil damping of the moving element 57.

In the construction of the galvanometer elements it has been found that a certain arrangement and method of assembly offers certain advantages. In assembling the apparatus shown in Figures 3 and 4 the housing carries a lens 65. It might be thought that the leps 65 could be cemented directly into an aperture in the housing 25, particularly since it is desired to orient the lens with respect to the optical path of light passing therethrough. This light path extends from the source of light to the mirror 56 and back to the recording material. It, however, has been found advantageous to mount the lens 65 in a bezel 66 with a shellac base thermoplastic cement. The surfaces of the lens subsequently are highly polished. Then the bezel and lens are placed in position in the housing 25. The bezel 66 is cemented with a synthetic alkyd resin cement, such as Glyptal. Just before the cement is quite hard, the lens is oriented with respect to the optical path. While for the purpose of illustrating and describing the present invention certain preferred foi' saidframe having contacts therein for said connf'zc'torrpins,l on'e of said contacts being connected .to said case andv the vother insulated therefrom, Va cradle Yhaving a vertical opening for said case and having two supporting surfaces 'each forming segmental portions 'of ahorizntal cylinder; Va permanent 'magnet structure havingV surfaces' complementary to said cradle, means for adjustinfgfthe position of said case about the axis of saidl horizontal cylinder, means carried. by said cradle for rotating said 'case ielativ ther'to about its longitudinal axis including a ygear: mounted on said 'cradle arid-a lgear sector mounted 'on 'said case. Y

2i galvanometer eleinen't for a multi=element galvanrneter comprising an elongated coil suspended within a non-magnetic rectangular frame', aconne'ctor pin at each end `ofs'aid frame connected to said coil, a -nonmagnetic rcylindrical case having contacts therein to receive said; connector pins, a magnetic cradle' for said case having supporting surfaces -forming segments of a. ghorizontal cylinder, a' permanent magnet structure having 'complementary .supporting surfaces for each cradle, ime'ans carried by `said structure for rocking said 'cradle about a horizontal axis, "said, 'cylindrical ca'sehav'i'ng on it'snjexterioi: Ya gear sector, a manually adjustable gear mountedfons'aidcradle -for engaging said gear sector to vadjust lsaid case about a vertical axis, and

magnetic pole pieces carried by said cylinder and extend- 'Y ing'fromsaidcradie'- inwardly toward said coil;y f

3.` A galvanometer element for a multi-element galvanometer comprising a movable coil mounted within a rectangular frame, an insulated connector pin located at each end of said frame and connected to said coil, a non-magnetic cylindrical case' Ili'av'ing contacts therein to receive saidconnector pins, one of said contacts being connected to" 'said 'ease fand the vother contact insulated,

therefrom, a cradle for said casehaving surfacesforming seg'nie'zii'ts-Y of "aflioiz'oiital cylinder, said cradle having a' vertical cyiufdricai opening, 'a riia'gneficstr'uemre 'having supporting surfaces complementary thereto, Vsaid struc-V turerincluding permanent magnet, means :carried Yby said structure for rocking said cradle about a horizontal axis, said cylindrical'case]h''vingl attached to its exterior a gear sector, a manually operable gear mounted on said cradle for engaging said gear sector to rotate said i case about its longitudinal axis, magnetic `pole piec'es carried by said cylinder and extending inwardly toward said coil, said pole ,pieces'having exterior surfaces com plementary to the opening-in saidl cradle, a lens -car-r-ied by said case,and a mirror mountedv behind said leixs above said coil for actuation thereby.

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