US3117201A

US3117201A - Magnetic switch cartridge construction

Info

Publication number: US3117201A
Application number: US7478A
Authority: US
Inventors: Glenn A Reese
Original assignee: Magnavox Co
Current assignee: Philips North America LLC
Priority date: 1960-02-08
Filing date: 1960-02-08
Publication date: 1964-01-07
Anticipated expiration: 1981-01-07

Description

Jan. 7, 1964 G. A. REESE v MAGNETIC SWITCH CARTRIDGE CONSTRUCTION Filed Feb. 8, 1960 United States Patent Ofiice 3,117,201 Patented Jan. 7, 1964 3,117,201 MAGNETIC SWITCH CARTRIDGE CONSTRUCTION Glenn A. Reese, Canoga Park, Calith, assignor to The Magnavox Company, Los Angeles, Calit., a corporation of Delaware Filed Feb. 8, 1960, Ser. No. 7,473 7 Claims. (Cl. 20087) This invention relates to magnetic switches and, more particularly, to such switches which are fast-operating and reliable.

A magnetic switch is operated by a changing magnetic field which moves the magnetic armature, and the movement of the armature transfers conductive connections through the armature from a first contact to a second contact. The armature then forms part of the electrical circuitry through the switch. There are many applications which require high speed switch operation for switching relatively small potentials measured in microvolts. Conventional magnetic switches are generally unsatisfactory for such applications because of speed limitations, and because of noise introduced through the capacitive coupling formed by the armature and the surounding switch components. When small potentials are being switched, a relatively minute bounce of the armature as it engages a stationary contact introduces noise of a magnitude corresponding to that of the potentials being switched. This later bounce difficulty is emphasized with high speed and rapid armature movement.

To illustrate applications in which the switch requirements are fairly stringent, in my copending patent applications Serial Nos. 652,968, filed on April 15, 1957 now Patent No. 2,945,931; 753,041, filed on August 4, 1958 now Patent No. 2,988,616; and 813,736, filed on May 18, 1959 now Patent No. 3,05 1,80 6, magnetic switching assemblies are disclosed in which each of the magnetic switches is operated and released during intervals measured in microseconds. The switching assemblies, moreover, are utilized for switching or sampling small potentials. Any noise introduced by contact bounce, by capacitive coupling or otherwise, would be deleterious. Moreover, in these switching assemblies, rapid switch operation is required to provide for sampling interval accuracy. Variations in the speed of operation of the magnetic switches would materially vary the sampling intervals because the entire interval or channel during which a switch is opera-ted and then reset is measured in microseconds.

In a specific illustrative embodiment of this invention, a magnetic switch is provided which may be utilized in the switching assemblies disclosed in the above-identified patent applications or in other applications where high speed, reliable, substantially noise-free, operation is required. In the illustrative embodiment, a magnetic switch is provided which has an armature electrically isolated from the contacts of the switch. The armature is not included as part of any electrical circuit through the switch. The armature may, therefore, be electrically grounded to avoid any noise producing capacitive effect. Moreover, any deleterious effects resulting from a contact between the armature and any of its surrounding components are avoided.

The armature supports a substantially cylindrical but slightly tapered armature contact by means of a contact insulator which separates it from the armature. When the switch is assembled, the operation of the switch may readily be adjusted by moving the armature longitudinally in the switch to vary the longitudinal position of the tapered armature contact in the switch. The armature contact is positioned centrally among four contact segments. The four contact segments form an essentially diamond shaped internal surface about the armature contact. When the switch is normal, the armature contact engages two of the contact segments, and, when the switch is operated by magneticaly influencing the armature, the armature contact engages the other two contact segments.

Features of this invention pertain to the provision of predetermined angles for the contact segments so that the armature contact does not bounce and the operating tolerances are quite small. The distances between the opposite internal surfaces of the four segments are identical and the armature contact can never simultaneously engage a pair of opposite internal surfaces. One pair of opposite segments is connected to simulate the common or armature electrical connection and the other pair of opposite segments electrically represents respectively the open and closed conditions of the switch. Effectively, the switch simulates a transfer contact wherein an armature is positioned to contact one or the other of two associated contacts.

Other features of this invention relate to the dimensions of the segments and of the armature contact such that the open and closed transfer contacts can never be electrically connected in the switch. Even though the switch is subjected to considerable shock and vibration, at no time can the contact armature engage simultaneously the two opposite contact segments which electrically form the transfer contacts of the switch.

Further advantages and features of this invention will become apparent upon consideration of the followiing description when read in conjunction with the drawing wherein:

FIGURE 1 is a sectional view of the magnetic switch of this invention;

FIGURE 2 is an exploded view of the magnetic switch illustrating the arrangement of its various components with portions of some of the components removed;

FIGURE 3 is a partial sectional view of the contact segments and the armature contact utilized in the magnetic switch of this invention; and

FIGURE 4 is a functional electrical representation of the magnetic switch of this invention.

Referring to FIGURES 1 through 4, a fast operating magnetic switch 10 has an upper cylindrically-shaped shell 11 and a lower cylindrically-shaped shell 12 together forming a casing for the magnetic switch 10. The two shells 11 and 12 have substantially similar outer and inner diameters and may be of magnetic material such as steel to form a magnetic shield for the components enclosed therein. The shielding function of the shells 11 and 12 is hereinafter described. The two shells 11 and 12 may be welded together to form a single composite cylindrical casing. At one end of the magnetic shell 12 is affixed an armature casing 13 which is preferably also cylindrical in shape and is adapted to be fitted into the end of the shell 12. The armature casing 13 is non-magnetic and may, for example, be of brass to permit magnetic flux through the casing 13 to a hollow armature 15 enclosed thereby. The armature 15 is made of magnetic material such as steel and is preferably cylindrical in shape, being fitted in the armature casing 13. An insulating collar 18 is mounted at one end of the armature 15 for pivotable movement with the armature 15. The insulating collar 18 has an outer diameter which is slightly greater than that of the armature 15 and less than the inner diameter of the armature casing 13.

The armature 15 and the collar 18 are supported on a resilient wire 16 which may be made of steel. The steel wire 16 is supported by a plug 17 which is fitted at one end of the armature casing 13. The plug 17 may be made of magnetic or nonmagnetic material and it may be made of conductive or insulating material. The

plug 17 need not be made of insulating material because, as is hereinafter described, the armature 15 does not form part of the electric circuitry through the switch 10. The armature casing 13 is filled with a viscous oil which forms a cushion for the magnetic armature 15. A thin layer of oil is formed between the insulating collar 18 and the inner surface of the armature casing 13. This layer of oil forms a dynamic pivot for the magnetic armature relative to the armature casing 13 with the collar 18 functioning as the fulcrum. As described above, the armature may be made of steel and the collar 18 may be made of an insulating material. The collar 18 may also be made of a conductive material, as the armature 15 need not be insulated from the armature casing 13 because it does not form a part of the electrical circuits through the switch 10. Though the collar 18 and plug 17 may be made of conductive material, in the specific illustrative embodiment, these components are made of insulating material to reduce the coupling between the casing 13 and the active components in the switch.

At one of its ends, the armature 15 supports the collar 18, and at its other end it supports a contact insulator 20 illustrated particularly in FIGURE 2. The contact insulator 20 is a double plug member fitting on one side into the hollow armature 15 and on its other side into an armature contact 22 which is supported thereby. The armature contact 22, which may be made of conductive material such as gold, is circular in cross section, but slightly tapered (approximately a degree taper) away from the armature 15. Due to the contact insulator 20, the armature contact 22 is insulated from the armature 15.

The tapered armature contact 22 fits among, and is encircled by four contact segments 24 through 27 of a contact disc 23. The position of the armature contact 22 relative to the four segments 24 through 27 is illustrated particularly in FIGURE 3. In the normal position of the armature 15, the contact 22 is in electrical contact with the two segments 27 and 26 and, when the armature 15 is in its operated condition under the influence of a magnetic field through the casing 13, the contact 22 is in electrical contact with the two segments 24 and 25. The stroke or movement of the contact 22 between the pairs of segments may be quite small, illustratively 0.001 inch. The spacing illustrated in FIGURE 3 is somewhat exaggerated to illustrate that the contact 22 is an electrical contact with only one pair of the four segments 24 through 26. The length of the stroke may be adjusted when the switch is assembled by moving the armature 15 longitudinally in the armature casing 13. Due to the taper of the armature contact 22, its longitudinal movement with respect to the disc 23 varies the spacing between it and the segments 24 through 27.

The minimum distance between the two

segments

25 and 27 is substantially equal to the minimum distance between the two segments 24 and 2s so that the armature contact 22 cannot simultaneously electrically contact a pair of opposite segments. For example, the contact 22 can never be simultaneously against the segment 25 and the segment 27 because the distance therebetween is greater than the diameter of the armature contact 22 at its cross section position in the disc 23. This particular configuration functions as a safety measure to prevent electrically connecting the two effectively stationary contacts of the switch which are depicted in FIGURE 4.

As indicated in FIGURE 4, the switch 10 has two stationary contacts 50 and 51 and a movable armature 52 which is normally positioned against the stationary contact 50 and which can be moved adjacent the stationary contact 51. The safety measure provided by the particular configuration of a disc 23 and the armature contact 22 avoids establishing an electrical connection between the two stationary contacts 50 and 51 at any position of the armature 22, even in the presence of shock or vibration of any magnitude. The two stationary contacts 5t) and 51 can never be electrically interconnected because the diameter of the armature contact 22 at the disc 23 is smaller than the distance between opposite pairs of the segments of the disc 23.

The contact segments 24 through 27 may be gold plated and may be formed as one continuous disc 23 which is brazed on one end of a ceramic insulator 35). The centrally located diamond shaped opening in the disc 23 is formed by an accurate punch die before the disc 23 is affixed to the insulator 30. After the disc 23 is brazed to the insulator 30, the disc 23 and a portion of the ceramic insulator 35) are cut to form the electrically isolated segments 24 through 27. The ceramic insulator 30 may be cylindrically shaped having a maximum diameter which is substantially the same as the maximum diameter of the disc 23. The ceramic insulator 30 has a small cylindrical opening 30a at the end to which the disc 23 is affixed so that the armature contact 22 can be inserted partially therein if necessary. The ceramic insulator 30 fits snugly into the steel shells 11 and 12, which were described above, having a maximum diameter slightly smaller than the inside diameters of the shells 11 and 12. When the ceramic insulator 30 is manufactured, four cylindrical holes are formed through the insulator 30 having axes parallel to the longitudinal axis of the ceramic insulator 30. The end of the ceramic insulator 30 adjacent the disc 23 and the surfaces of the four holes 40 are then metalized by a plating process.

When the disc 23 is cut to form the four segments 24 through 27, the end of the ceramic insulator 30 adjacent thereto is also cut to cut its plated metallic surface. In this manner, the four segments 24 through 27 are insulated from each other having no conductive connection across the metallic surface on the end of the ceramic insulator 30. The four contact segments 24 through 27 are oriented on the ceramic insulator 30 so that an electrically conductive connection is made from each of the segments 24 through 27 to one of the metalized holes 40 in the insulator 30. At the other end of the four metalized holes 40 are inserted, respectively, four wires 34 through 37 which provide for electrical connections to the magnetic switch 10. The four wires 34 through 37 extend through an opening 11a at the end of the steel shell 11 as indicated particularly in FIGURE 1. In this manner, four electrical connections are provided respectively through the four wires 34 through 37, the four metalized surface holes 40 to the four segments 24 through 27 of the contact disc 23.

This particular method of fabricating the switch components is relatively inexpensive and yet, as is hereinafter described, the timing accuracy and speed provided by the switch 10 are quite high.

As described above and indicated in FIGURE 3, the armature contact 22 is normally positioned to provide electrical connection between the two segments 27 and 26. When a magnetic field moves the armature 15, the armature contact 22 is moved to provide a connection between the other two segments 24 and 25. As also described above, the distances between the opposite internal faces of the segment pairs are similar and the dimensions therebetween are such that the armature contact 22 can never simultaneously contact or engage either opposite pair of segments. The two segments 24 and 26 may be electrically connected together, external to the switch 10, to form a common or an armature connection through the switch 10, and the two

segments

25 and 27 may be electrically isolated external of the switch 10 to form the two effectively stationary contacts of the switch 10. In other words, the two wires 34 and 36 are electrically connected to simulate the connection to the movable armature 50 of the functional representation in FIGURE 4. The other two wires 35 and 37 simulate the connections to the two stationary contacts 50 and 51.

' Just as the armature 52 in FIGURE 4 cannot simultaneously contact both contacts 50 and 51, so cannot the connection to the two segments 24 and 26 simultaneously be in electrical contact with the connections to both segments 25 and 2'7 at the disc 23. The operation of the magnetic switch It), in this manner, simulates the electrical break-before-make operation of the transfer switch shown in FIGURE 4.

The acute angle formed by the internal surface of either pair of two adjacent segments may be between 55 degrees and 60 degrees. The particular angle is selected to reduce any bounce of the armature contact 22. By making the angle acute, a slight skid is developed by the armature contact 22 as it wedges between the two adjacent internal surfaces. It the acute angle is made larger, the contact 22 hits the segment surfaces with a smaller skidding effect so that any tendency to bounce is increased. The more closely is the contacted segment surface aligned to be perpendicular to the direction of motion of the contact 22, the greater the bounce. Bounce is harmful because of the noise it introduces and because the timing of the switch becomes less accurate. By providing for an acute angle between the internal surfaces of the segments 24 and 25, the contact 22 wedges therebetween as it is moved on the armature so that any tendency to bounce is resisted.

In order to maintain the timing accuracy of the switch, there is a practical lower limit to the size of the acute angle formed by the adjacent internal surfaces of the segment pairs. As the acute angle is made smaller, the tolerances for the contact swing become greater because it is more difiicult to predict the exact point on the internal surface which will first engage the contact 22. By making the angle more acute, the dimension of the internal surface in the direction of the contact swing is greater and a small ecentricity in the contact swing varies the duration of the switching operation by a considerable factor. With a stroke of 0.001 inch given as an illustration above, the switching interval responsive to a change of the magnetic flux through the armature 15 may be approximately 200 microseconds. The more perpendicular are the alignments of the contacted internal surfaces with the direction of the movement of the contact-22, the less variation in the switching interval and, therefore, the more acurate the timing provided by the switch 10. The particular angle which is selected is, therefore, a compromise to both reduce bounce and maintain small tolerances in the timing of the switch 10.

As described above, shells 11 and 12 serve as a magnetic shield for the components enclosed thereby, namely the segments 24-27, holes 40, and wires 34 to 37. The shells 11 and 12 serve to prevent magnetic noise pulses from being induced to the contacts of the switch It) and to reduce any tendency for such pulses to initiate current flow in the electrical circuitry of the switch 10. Noise pulses are also not readily introduced by capacitive or electrical coupling to the armature 15 because it is electrically insulated from the electrical circuits through the switch 10. The contact insulator 10 prevents any electrical disturbances introduced to the armature 15 either by capacitive coupling with the casing 13 or by electrical contact therewith from being introduced to the segments 24 through 27 of the contact disc 23. With the armature 15 isolated in this manner from the electrical circuitry, a noise level ilustratively as small as 10 microvolts is present. The 10 microvolt illustrative noise level represents the total noise level due to all factors including due to bounce and stray capacity. Signals, for example, as low as microvolts may accordingly be switched by the switch 10 and readily separated from the noise.

Although this invention has been disclosed and illustrated with reference to particular applications, the principles involved are susceptible of numerous other applications which will be apparent to persons skilled in the art. The invention is, therefore, to be limited only as indicated by the scope of the appended claims.

I claim:

1. In a switching unit, a casing forming an envelope for the switching unit and having a cylindrical armature enclosing section, and a cylindrical contact enclosing section aifixed to said armature enclosing section and concentrically positioned with respect to said armature enclosing section, a cylindrical armature made of magnetic material and enclosed by said armature enclosing section, a resilient pivot support for said armature and permitting the pivotable movement of said armature in a first plane by magnetic flux through said armature enclosing section, an insulator member carried at one end of said armature, an armature contact carried by said insulator and enclosed by said contact enclosing section and insulated by said insulator from said armature whereby said armature is electrically isolated from the contacts of the switching unit, and a number of segments of con-' ductive material disposed in a second plane displaced angularly from the first plane encircling said armature contact and defining the stationary contacts of the switching unit.

2. In a switching unit, a casing forming an envelope for the switching unit and having a cylindrical armature enclosing section, and a cylindrical contact enclosing sec.- tion and concentrically positioned with respect to said armature enclosing section, a cylindrical armature made of magnetic material and enclosed by said armature enclosing section, a resilient support for said armature and permitting the movement of said armature in a first plane by magnetic flux through said armature enclosing section, an insulator member carried at one end of said armature, an armature contact carried by said insulator and enclosed by said contact enclosing section and insulated by said insulator from said armature whereby said armature is electrically isolated from the contacts of the switching unit, a first pair of conductive segments positioned in substantially a second single plane displaced angularly from the first plane in said contact enclosing section adjacent said armature contact for simultaneous contact thereby when said armature is in one position, a second pair of conductive segments positioned in substantially the second single plane in said contact enclosing section adjacent said armature contact for simultaneous contact thereby when said armature is in a second position, a common electrical conductor electrically connected to one of said segments of said first and of said second pairs of contacts, an electrical conductor electrically connected to the other segment of said first pair, and an electrical conductor electrically connected to the other segment of said second pair.

3. A magnetic switch, including, a movable armature having a normal and an operative position, a contact affixed at one end of said armature, and a contact member including four contact segments which are insulated from each other, said four segments defining a diamondshaped centrally located opening in which said armature contact is positioned, said armature contact being positioned adjacent one of the two acute angles of the diamond-shaped opening against two of said contact segments when said movable armature is in its normal position and adjacent the other acute angle of the diamondshaped opening when said movable armature is in its operative position.

4. A magnetic switch, including, a movable armature having a normal and an operative position, a contact afiixed at one end of said armature, and a contact member including four contact segments which are insulated from each other, said four segments defining a diamond-shaped centrally located opening in which said armature contact is positioned, said armature contact being positioned adjacent one of the two acute angles of the diamond-shaped opening against two of said contact segments when said movable armature is in its normal position and adjacent the other acute angle of the diamondshaped opening when said movable armature is in its operative position, the distance between the contact segments oppositely positioned about said armature contact being greater than the maximum cross sectional distance of said armature contact so that said armature contact cannot simultaneously contact a pair of oppositely positioned contact segments.

5. A magnetic switch, including, a movable armature having a normal and an operative position, a contact affixed at one end of said armature, an insulator member having four conductive connections passing through said member, and a contact member including four contact segments which are insulated from each other, said contact member being afiixed to said insulator member so that each of said contact segments is in electrical contact with a different one of said conductive connections through said insulator member, said four segments defining a diamond-shaped centrally located opening in which said armature contact is positioned, said armature contact being positioned adjacent one of the two acute angles of the diamondshaped opening against two of said contact segments when said movable armature is in its normal position and adjacent the other acute angle of the diamond-shaped opening when said movable armature is in its operative position.

6. In a switching unit, a casing forming an envelope for enclosing the various components of the switching unit including a portion made of magnetic material and a portion made of non-magnetic material, an armature made of magnetic material positioned in the non-magnetic portion of said casing, said armature having a normal position when not under the influence of a magnetic field and an operative position when under the influence of a magnetic field, a contact insulator supported by said armature, a movable contact supported by said contact insulator and insulated by said contact from said armature, said armature contact being movable with said armature and therefore having a normal position and an operative position, and a contact member including four contact segments which are insulated from each other, said four segments defining a diamond-shaped centrally l0 cated opening in which said armature contact is positioned, said armature contact being positioned adjacent one of the two acute angles of the diamond-shaped opening against two of said contact segments when said movable armature is in its normal position and adjacent the other acute angle of the diamond-shaped opening whe said movable armature is in its operative position, said armature contact and said four segments of said contact member being positioned in the magnetic portion of said casing so as to be shielded thereby from external magnetic fields.

7. A magnetic switch, including, a movable armature having a normal and an operative position, a contact afiixed at one end of said armature, and a contact disc including four contact segments which are insulated from each other, said four segments defining a diamond-shaped centrally located opening in which said armature contact is positioned, said armature contact being positioned adjacent one of the two acute angles of the diamondshaped opening against two of said contact segments when said movable armature is in its normal position and adjacent the other acute angle of the diamond-shaped opening when said movable armature is in its operative position, said armature contact being tapered having the shape of a truncated cone so that the stroke of said armature contact between the pairs of contact segments is determined by the position of the armature contact along its longitudinal axis with respect to the position of said contact disc.

References Qitetl in the tile of this patent UNITED STATES PATENTS 2,298,802 Meyerhoefer Oct. 13, 1942 2,402,744 Horman Sept. 17, 1946 2,541,398 Wood Feb. 13, 1951 2,886,668 Steward et al. May 12, 1959 2,908,780 Walters Oct. 13, 1959 2,914,634 Koda Nov. 24, 1959 2,921,161 Scata et al. Jan. 12, 1960 2,931,871 Dowds Apr. 5, 1960 2,976,379 Rhodes Mar. 21, 1961 3,001,046 Racz et al. Sept. 19, 1961 3,014,106 Jennings Dec. 19, 1961