US3676811A

US3676811A - Magnetic switch

Info

Publication number: US3676811A
Application number: US126068A
Authority: US
Inventors: Philip Joseph Parlato
Original assignee: Alarm Products International Inc
Current assignee: Alarm Products International Inc
Priority date: 1971-03-19
Filing date: 1971-03-19
Publication date: 1972-07-11
Anticipated expiration: 1989-07-11

Abstract

A magnetic switch device comprises a housing, two substantially planar bifurcated flexible members arranged in opposing relationship with one pair of distal ends of corresponding leg segments overlapping and being free to move while the other pair of distal ends are fixed to the housing. Armatures are attached to the corresponding leg segments and are moved responsive to a magnetic force to cause contacts on the overlapping distal ends to move together with a brushing motion.

Description

I United States Patent 1151 3,676,811 Parlato [4 July 11, 1972 54] MAGNETIC SWITCH 3,259,715 7/1966 Wagar ..335/154 2,210,701 8/1940 Bletz ..337/89 [72] Invent Philip Kmgs Park 2,987,593 6/1961 Alley ..335/154 [73] Assignee: Alarm Products International, Inc., Long Island y Primary Examiner-Harold Broome 221 Filed: March 19, 1971 Ammey-Rwm chen [21] Appl. No.: 126,068 57 ABSTRACT A magnetic switch device comprises a housing, two substan- [52] US. Cl. ..335/205 tiany planar bif d fl ibl members arranged in opposing [51] Int. Cl. ..H0lh 9/00 relationship with one pailof distal ends f corresponding leg [58] Field Of Search ..335/205, 154; 200/166 C; Segments pp g and being free to move while the other 337/89 pair of distal ends are fixed to the housing. Armatures are at- 56] References Cited tached to the corresponding leg segments and are moved responsive to a magnetlc force to cause contacts on the over- UNITED STATES PATENTS lapping distal ends to move together with a brushing motion.

3,284,743 1 l/l966 Spewock et al ..335/205 9 Claims, 6 Drawing Figures Patented July 11, 1972 3,676,811

"Hal

INVENTOR.

PHILIP JOSEPH PARLATO WM W ATTORNEYS MAGNETIC SWITCH BACKGROUND OF THE INVENTION This invention relates to a switch, and more particularly, to a magnetically operated switch.

Such switches find widespread use, particularly, with burglar alarm systems where the actuating element for the switch does not touch the switch contacts. The switch is mounted on a fixed member such as a doorway or window jamb, while a magnetic actuating element is fastened to a movable member such as a window or door, respectively. When the window or door is moved, the switch contacts move from either a normally open or closed position to the other, thus, providing an actuating signal for the alarm system.

The prior art is replete with such magnetic switches which are held in a plastic sealed housing. Unfortunately, they suffer from many disadvantages which detract from their performance, reliability, and durability. For instance, many of these switches are provided with a straight rectangularly shaped plate or spring arm which is fixed at one end to a housing and has the opposite end free and biased to flex in a predetermined direction. An armature is secured to the arm, and when a magnet is brought into proximity with the switch, the spring arm moves from its normal position thereby opening or closing a pair of contacts. Upon removal of the magnet, the spring arm again assumes its normal position. The flexing force is almost entirely borne at the fixed end and due to the structural characteristics of the spring arm, the repeated flexing can cause a structural failure at the fixed end.

Additionally, a contact is attached to the spring member and a corresponding contact is attached to a fixed plate member. As the two contacts touch, they close an electrical circuit causing an arcing to occur across the contacts as they move towards each other. Generally, the same areas on the respective contacts serve as the arcing points because of their uneven surface characteristics. Such arcing over a period of time causes degradation of the electrical contact between the contacts and possible welding thereof.

Generally, due to the complex construction of prior art magnetic switch devices, the terminal posts on the housing thereof are widely spaced apart, often on opposite surfaces. Such spacing makes it difficult to install and to provide a tamper-proof device because the terminals are accessible to an intruder who can easily disconnect the wires attached thereto. In addition, because of the large number of different parts employed in the construction of the prior art switches, they are expensive to manufacture and difficult to assemble.

SUMMARY OF THE INVENTION An object of this invention is to provide an improved magnetic switch.

Another object of this invention is to provide a magnetic switch which is durable and reliable and yet inexpensive to manufacture and easy to assemble and install.

Still another object of this invention is to provide a magnetic switch in which the terminal posts thereof are covered to prevent tampering.

Other objects, advantages and features of this invention will become more apparent from the following description.

In accordance with the principles of this invention, the above objects are accomplished by providing a magnetic switch device which comprises two substantially planar bifurcated flexible members, each being provided with first and I second leg segments terminating in first and second distal When the contacts touch, the armatures continue moving toward each other causing a brushing action between the contacts because of the arcuate movement thereof. One armature is attached in a cantilevered relationship with a corresponding leg segment so as to further contribute to the brushing action. It should be noted that the contacts are more closely spaced then are the armatures so that the contacts initially touch one another whereafter, subsequently the armatures move into an abutting relationship thereby causing the brushing action between the contacts to prevent welding therebetween.

As a further feature of this invention, the second distal ends are connected to terminal posts which are provided with threaded bores for communication with suitable screws for electrically connecting the members to an electric circuit controlled by the switch. A protective cover is suitably mounted to prevent the screws from being tampered with, thereby insuring reliability in a safety alarm system. The protective cover is mounted on the housing of the magnetic switch through the medium of a one-way tightening screw, which when tightened, is not susceptible of being thereafter removed or loosened.

IN THE DRAWINGS FIG. 1 is an exploded perspective view of a magnetic switch device and protective cover associated therewith in accordance with one embodiment of the invention;

FIG. 2 is a top view of the spring arm members and contacts of this magnetic switch invention;

FIG. 3 is a sectional view taken along line 3-3 of FIG. 2 illustrating the magnetic switch device having its contacts normally open;

FIGS. 4' and 5 illustrate the movement of the spring arm members and respective armatures responsive to a magnetic force; and

FIG. 6 is a view similar to FIG. 3 illustrating another embodiment in which the contacts are in a normally closed position and are movable to an open position responsive to a magnetic force.

DETAILED DESCRIPTION Referring to FIG. 1, there is shown a magnetic switch device of this invention which includes a housing 10, preferably of plastic, which may be sealed. The housing 10 is provided with a central section 11 enclosing movable spring arm members of the magnetic switch and

end portions

12 and 13 having through-

holes

14 and 15, respectively, for attaching the switch to a suitable surface. First and second terminals 16 and 17 are connected to respective terminal posts within the housing which are provided with threaded

bores

18 and 19, respectively, communicating with

respective screws

20 and 21 for electrically connecting a wire to the switch. An insulating separation block 22, which may be integrally formed with the housing, prevents inadvertent short circuiting between the terminals when the device is being installed. A protective plate or cover 23 for covering terminals 16 and 17 is secured to the housing by means of a one-way tightening screw 24 which communicates with a threaded recess 25 in the separation block 22 through a bore 26 in the cover. The one-way tightening screw, after being firmly tightened, prevents the cover 23 from being removed and, therefore, the terminals are prevented from being tamperproof with.

The switch mechanism is more clearly seen in FIGS. 2 and 3, in which the magnetic switch is illustrated as comprising substantially planar bifurcated

flexible members

30 and 32, disposed in opposing relationship with the members being formed of a monolithic flat sheet metal, preferably of phosphor bronze. The

members

30 and 32 are provided with first and

second leg segments

34 and 36 and 38 and 40, respectively, joined by respective

intermediate sections

42 and 43. Illustratively, the

members

30 and 32 are U-shaped for convenience of manufacturing and compactness of size, although other shapes such as V or J shapes would be suitable.

The

members

30 and 32 have overlapping

distal ends

44 and 46 which are free and

distal ends

48 and 50 which are fixed. The fixed ends are attached, as by riveting, to

terminal posts

52 and 54 which are electrically connected to terminals 16 and 17 through

screws

20 and 21, respectively. The outer corners of

first leg segments

34 and 38 are cut to assist the movement of

members

30 and 32.

Distal ends

44 and 46 have

respective contacts

56 and 58 secured thereto with the contacts in an opposted relationship. Each contact, preferably, is formed of silver or a silver alloy with contact 56 being rounded and contact 58 being cylindrical in shape.

Armatures

60 and 62 are attached to the

leg segments

36 and 40 of the

members

30 and 32 by riveting the respective armatures at

distal ends

48 and 50 thereof. Leg segment 36 extends beyond the end of armature 60 and is in a cantilevered relation therewith, while armature 62 is fixed to the leg segment 40 by fixedly attaching the leg segment to the armature.

With'reference to FIG. 3, the

contacts

56 and 58 are shown in a normally open position and are more closely spaced than are

armatures

60 and 62. When a magnet 71 is in proximity to the members and armatures, the two spring members move towards each other as shown in FIGS. 4 and because one at mature becomes magnetized as a North pole, while the other armature becomes a South pole in conventional manner. The flexing movement is distributed through-out the U-shaped

members

30 and 32.

As a feature of this invention, a brushing effect is achieved between the

contacts

56 and 58. When a magnet is proximate to the magnetic switch, the armatures become oppositely magnetized and are attracted towards each other causing the contacts to touch. When the contacts touch, a force is produced in the cantilevered leg restraining further movement of the armatures. But the magnet force attracting the armatures is greater than this restraining force, and since there is a larger spacing between the armatures than the contacts, the armatures continue their movement until they abut. The movement of the contacts is arcuate, and the subsequent movement of the armatures past the point of contact touching causes a brushing effect to be achieved between the contacts. Additionally, the armatures form a second closed circuit path for the flow of current through the switch, thereby distributing the heating effects of such current.

FIG. .6 shows another embodiment of this invention in which the contacts are in a normally closed position and are movable to an open position. The numerals in FIG. 6 correspond to those FIGS. 1 through 5 but are joined. Bifurcated member 32 is secured to armature 62 and its leg segment 40 overhangs the armature to be in a cantilevered relation therewith. Leg segment 36 is provided with a Z bend, thereby locating contact 56 above the armature 60 and causing contact 56' to touch contact 58 without the switchs being under the influence of a magnetic field. Armature 60 attached to leg segment 36 is attracted to armature 62' under the influence of a magnetic force and the

contacts

56 and 58 are caused to move away from each other, thereby opening the magnetic rpm switch. a

It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained and, since certain changes may be made in the above apparatus without departing from the scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

I claim:

1. A magnetic switch actuated by a magnetic force comprising a housing, two substantially planar bifurcated flexible members having first and second leg segments terminating in first and second distal ends, respectively, said members being coupled to said housing in an opposing relationship with corresponding first distal ends of said members being free and overlapping each other, electrical contacts mounted on said correspondin first distal ends, said second distal ends being fixed to said ousing, and magnetically responslve armatures connected to each of said first leg segments whereby said two members are adapted for moving from unflexed to flexed conditions responsive to a magnetic force and with the resultant stresses being distributed throughout said flexible members.

2. A magnetic switch as set forth in claim 1, wherein each of said two members comprises an intermediate zone joining respective first and second leg segments, each of said two members being monolithic and being of flat sheet metal.

3. A magnetic switch as set forth in claim 2, wherein said two members are U-shaped.

4. A magnetic switch as set forth in claim 1, wherein a brushing movement is effected between said contacts, at least one of said first leg segments being in a cantilevered relationship with the corresponding armature, said armatures being separated by greater distance than said contacts, said magnetic force causing said armatures to become oppositely magnetized and be attracted toward each other, said armatures moving toward each other causing said contacts to touch, a restraining force exerted by said leg segment in cantilevered relationship restraining further movement of said armatures, said oppositely magnetized armatures having a magnetic force of attraction greater than said restraining force, said armatures continuing to move towards each other after said contacts touch to effect said brushing.

5. A magnetic switch as set forth in claim 4, wherein said armatures overlap and touch each other responsive to said magnetic force.

6. A magnetic switch as set forth in claim 1, comprising terminal posts for said switch electrically connected to said second distal ends of said members.

7. A magnetic switch as set forth in claim 6, comprising a separate cover plate for covering said terminal posts.

8. A magnetic switch as set forth in claim 1, wherein said electrical contacts are normally in a closed position and are flexed to an open position.

9. A magnetic switch as set forth in claim 1, wherein said electrical contacts are normally in an open position and are flexed to a closed position.

Claims

1. A magnetic switch actuated by a magnetic force comprising a housing, two substantially planar bifurcated flexible members having first and second leg segments terminating in first and second distal ends, respectively, said members being coupled to said housing in an opposing relationship with corresponding first distal ends of said members being free and overlapping each other, electrical contacts mounted on said corresponding first distal ends, said second distal ends being fixed to said housing, and magnetically responsive armatures connected to each of said first leg segments whereby said two members are adapted for moving from unflexed to flexed conditions responsive to a magnetic force and with the resultant stresses being distributed throughout said flexible members.