US2786702A

US2786702A - Magnetic catch

Info

Publication number: US2786702A
Authority: US
Inventors: Macy O Teetor
Original assignee: Individual
Current assignee: Individual
Priority date: 1954-02-23
Filing date: 1954-02-23
Publication date: 1957-03-26
Anticipated expiration: 1974-03-26

Description

March 26, 1957 M. o. TEETOR 2,786,702

' MAGNETIC CATCH Filed Feb. 25, 1954- s Sheets-Sheet 1 1&2 36 3943*!" March 26, 1957 M.O'. TEETOR 2,786,702

MAGNETIC CATCH Filed Feb. 25, 1954 s Sheets-Sheet 2 67 g INVENTOR. 7 ar /e22? 6Q BW, 11A WM' Doy-Q March 26, 1957 M. o. TEETOR MAGNETIC CATCH I 3 Shets-Sheet 3 Filed Feb. 23, 1954 IN V EN TOR.

{92 gas 5 aiyafeeibv Mun/M 27 United States Patent 2,786,702 MAGNETIC CATCH Macy O. Teeter, New Orleans, La. Application February 23, 1954, Serial No. 411,827 17 Claims. (Cl. 292-4515) This invention relates to a novel device utilizing magentic principles for retaining a closure member in closed position adjacent a frame member and more particularly to a novel magnetic catch for use on a cabinet door.

Magnetic door catches of various types have been suggested heretofore in which cooperating magnet and armature units are mounted in coacting positions on door and frame members. In some cases, the magnetic attractive forces are exerted in a direction transverse to the plane of the hinged door so that as the door approaches closed position the magnet unit exerts a positive force tending to move the door to closed position. In other words, in an installation of this type the magnet unit may actually assist in effecting closure of the door as Well as retaining the door in closed position. in other cases, the magnet and armature units are mounted in coacting relation adjacent an edgewise surface of the door so that the magnetic attractive forces act in a lateral direction substantially in the plane of the door. In a device of the latter type the catch acts primarily to retain the door in closed position by reason of the surface contact and frictional resistance between the magnet and the armature elements.

In my prior Patent No. 2,508,305, I have shown one type of magnetic catch which is highly effective and provides a number of important advantages over other magnetic and non-magnetic catches heretofore suggested. One of the principal features of my prior invention involves the movable mounting of one of the catch elements, i. e. either the magnetic element or the armature element, and also the use of a spring member operatively coacting with the movable catch element for normally urging it into retracted position inwardly of its supporting door or frame member.

The present invention is directed to an improved and simplified magnetic catch including a movable magnet element having a unique design which results in increased magnetic holding power and a highly effective catch operation. The catch of the present invention is relatively inexpensive and is extremely simple to manufacture, assemble and install. Also, as will hereinafter appear, the catch of the present invention lends itself readily for either of the general modes of installation described above, i. c. with the magnetic attractive forces being exerted generally transversely to the plane of the door or generally laterally and substantially in the plane of the door.

Accordingly, a primary object of the present invention is to provide an improved and simplified magnetic catch characterized by a movable magnet element having great magnetic holding power.

A further object of the invention is to provide an improved magnetic catch having a novel movable magnet element adapted to engage a cooperating armature element and to be retracted therefrom either by the use of spring means or by magnetic means.

Another object of the invention is to provide a novel combination of a door knob structure and a magnetic catch for the door.

An additional object of the invention is to provide a novel magnetic door catch having a simple and economical construction and adapted for use as a friction catch with the magnetic attractive forces being exerted in a generally lateral direction and substantially in the plane 2,786,702 Patented Mar. 26, 1957 ice 2 of the door but also being readily adapted for use with the magnetic attractive forces being exerted generally transversely to the plane of the door.

Other objects and advantages of the invention will become evident from the subsequent detailed description taken in conjunction with the accompanying drawings, wherein:

Fig. l is a fragmentary front elevational view of a cabinet provided with a magnetic door catch comprising one specific embodiment of the invention;

Fig. 2 is a longitudinal sectional view through the magnetic catch as taken on an enlarged scale along the line 2-2' of Fig. l and showing the position of the catch elements when the door is closed;

Fig. 3 is a view similar to Fig. 2 with portions of the catch in elevation and showing the movable catch element in retracted position when the cabinet door is open;

Fig. 4 is an end view of the device as seen from the right in Fig. 3;

Fig. 5 is an elevational view of the armature element as seen along the line 5-5 of Fig. 2;

Fig. 6 is a fragmentary front elevational View of a cabinet provided with a magnetic door catch comprising a different embodiment of the invention;

Fig. 7 is a front elevational View on an enlarged scale showing a portion of the catch structure as it appears when the cabinet door is open;

Fig. 8 is a longitudinal sectional view on an enlarged scale as taken along the line 88 of Fig. 6 and showing the position of the catch elements when the door is closed;

Fig. 9 is a fragmentary sectional view taken along the line 9-9 of Fig. 7 and showing the movable catch element in retracted position when the door is open;

Fig. 10 is a fragmentary front elevational view of a cabinet structure provided with a pair of magnetic door catches constituting still another embodiment of the invention;

Fig. 11 is an enlarged vertical sectional view with portions thereof in elevation as taken along the line 11-11 of Fig. 10;

Fig. 12 is a transverse sectional view on a still further enlarged scale as taken along the line 1212 of Fig. 11 and showing the position of the catch elements when the door is closed;

Fig. 13 is a view similar to Fig. 12 but showing the position of the catch when the door is open; and

Fig. 14 is a rear elevational view on an enlarged scale as seen along the line l t-14 of Fig. 11.

Referring first to Figs. 1 to 5, this embodiment of the invention utilizes a retractable magnet element which does not require the use of a spring or like mechanical device and which is especially adapted for use as a friction type catch mounted adjacent the vertical edge portions of the cabinet frame and door. Thus, a portion of a cabinet is shown comprising a door 20 hingedly secured to a frame having

vertical side portions

21 and 22 and a sill or base 23. An elongated strip or door stop 24 is provided on the base 23 in inwardly recessed relation from the front thereof, the door 20 being adapted to abut the strip 24 when the door is in closed position.

The magnetic catch, in this instance, consists of a magnet unit 26 mounted in the frame 21 and a cooperating armature unit comprising an apertured washer or disk 27 mounted on the vertical edge of the door 20 by means of a screw 28. The head portion of the screw is countersunk in the washer 27 so as to provide a smooth contact surface on the armature. As will readily be apparent, the armature and magnet units are thus mounted in coacting positions in the free vertical edge of the door 20 and on the adjacent vertical frame portion 21, respectively, so that the armature 27 can coact with the magnet unit 26 when the door 20 is in closed position against the door stop 24. As a matter of convenience, the magnet unit will generally be mounted in the door frame with the armature secured to the door as shown in Fig. 1. However, it is also within the scope of my invention to reverse the respective mountings on t 1e magnet and armature units so that the magnet unit is located in the door and the armature unit is attached to the frame.

As seen in Fig. 2, the magnet unit 26 has an outer tubular housing or casing 2? of non-magnetic metal such as brass. The tubular housing 29 has a tight press within a complementary bore 31 extending inwardly on a horizontal axis from the vertical edge of the door frame 21, and the outer end of the non-magnetic tubular housing 29 is formed with an outwardly extending flange portion 32 which is recessed slightly in the door frame so as to provide a flush surface with the frame. At its inner end the tubular housing 29 is tapered, as at 33, to an inner end portion 34 of reduced diameter. A cup 36 of steel or other magnetic metal, i. e. a metal having a high magnetic permeability or attractability, is telescoped over the reduced inner end portion 34 of the tubular housing 29 and has a tight frictional fit thereon so that the non-magnetic tubular member 29 and the magnetic end cup 36 constitute in effect a one-piece housing. The inner end of the reduced portion 34 is turned inwardly to a slight extent to provide a radial flange or stop 37 for the purpose hereinafter described.

The movable magnet means of the catch includes a magnet element 33 in the form of an elongated cylindrical bar magnet having a positive pole at one end and a negative pole at the other end and movably disposed within the housing 29. Any suitable magnetic metal or alloy may be used for the magnet element 38, but the alloy of aluminum, nickel and cobalt comme cially known as Alnico is particularly desirable. For maximum convenience and economy, the magnet element 38 may be cut from elongated bar stock and no special machining or finishing operations are necessary for the rough cast surfaces of the individual magnet elements. In order to enhance the holding power of the magnet element 38 relative to the armature element 27, I utilize as part of the movable magnet means an external magnet shell of steel or other magnetic metal, the shell being an elongated tubular sleeve 39 having an inner end portion 41 of reduced diameter connected by a tapering portion 42 to the enlarged diameter portion 39 which extends concentrically with the magnet element 33 and terminates in alignment with the outer end of the latter. The reduced end portion 41 of the magnet shell has a tight frictional press fit with the inner end portion of the magnet element 3-3, and the enlarged diameter shell portion 39 provides an annular clearance space or leakage gap 43 between the outer shell and the magnet element. Although not necessary, this air gap 43 may be filled with a suitable non-magnetic material if desired.

By the above described arrangement, the outer or contact end of the magnet means is thereby provided with annularly spaced magnetic poles at the outer or operating end of the magnet unit so tnat the magnetic flux path is highly concentrated whereby to obtain a greatly enhanced holding power of the magnetic means for the armature element 27. in other words, the external magnet shell 39 is in effect an extension or pole piece for extending the inner pole of the magnet in close proximity to the outer magnet pole whereby to obtain a more effective flux path at the operating end of the magnet element. As hereinbefo-re pointed out, the magnet element 38 and its outer shell 39 rigidly mounted thereon are movable axially as a unit within the magnet housing 2 -36. For limiting the extent of outward movement of the magnet means, a stop collar 44 of brass or other non-magnetic material is rigidly fitted around the reduced end portion 41 of the magnet shell and coacts with the inwardly turned flange portion 37 of the non-magnetic housing.

When the cabinet door is open, the movable magnet means is held in retracted position, as seen in Fig. 3, by reason of the magnetic attraction between the inner end or pole of the magnet element 33 and the steel cup 36. However, when the door 2% is closed, the magnet means moves outwardly so that the aligned contact faces of the magnet element 38 and the shell 39 contact the armature element 27 for holding the door 29 in closed position as in Fig. 2. Because of the increased flux concentration at the outer end of the magnet means, it will be understood that the magnetic attractive forces 'cting between the outer or double pole end of the magnet and the armature 2'7 is substantially greater than the magnetic attractive forces between the inner or single pole end of the magnet element 33 and the coacting steel cup 36. Consequently, when the door is closed sufficiently so that the armature 27 is within the field of influence of th outer end of the magnet means, the magnetic contact which holds the magnet in its Fig. 3 retracted position is readily overcome and disrupted so that the magnet moves to its Fig. 2 position. ecause of the annular clearance between the outer magnet shell 39 and the magnet housing 29, it will be seen that the magnet element with its attached shell can undergo a slight degree of angular cocking movement relative to the housing so as to compensate for slight misalignment which may occur between the door 20 and the frame 21 due to warpage or improper installation. Consequently, full surface contact between the coacting contact faces of the magnet unit and the armature element is thereby insured. it should also be pointed out that the stop action provided by the collar i4 and the coacting flange 37 also serves to prevent inadvertent Withdrawal or theft of the magnet element.

In Figs. 1 to 5, the magnetic catch i' installed to operate as a friction catch. in other l s, the outer end of the magnet ele rent the out end of the shell 39 engage armature surface contact therewith. '1 his engag re magnet and armature elements pro rictional sistance against pivotal mo or 2-) so that the latter is securely held in closed position. Moreover, since the magnetic attractive forc of the door and subsaut' .iy in of operation of the catch depends almost entirely on the close correlation of the spring pressure of the plunger with the clearance between the door and the frame. Obvious ly, however, these clearances subject to wide variation and cannot be practically controlled and as a result the amount of frictional resistance which the catch provides for holding the door closed is frequently too great so that operation is difficult or is too slight so that the door is not held securely. A highly important advantage of a magnetic friction catch of the present type is that it will operate very effectively and provide the per de. "e of frictional resistance with door and frame assemblies having varying degrees of spacing or clearance therebetween.

When it is desired to open the door, a relatively slight manual pull will serve to effect 1 movement of contact surface of the armature c ends of the magnet and shell until the armature is cornpletely disengaged from the .et cl ncnt whereupon the magnet means is automatically retracted into its housing by the action described above. oecause of the rctractive operation of the magnet means, the magnet element cannot possibly interfere with the normal operation of the door since the magnet element will remain in its normally retracted position until the armature is moved into partial alignment or overlapping relation with the outer end of the magnet clement thereby permitting the attractive forces of the magnet to act on the armature ele- 5 ment. In other words, the magnet element can never move'out prematurely and cause the door to strike the magnet element because the armature will not effect axial shifting of the magnet element until some substantial portion of the outer end of the armature overlies the corresponding end of the magnet element.

As seen in Figs. 1 to 5, I prefer to mount the magnetic catch in a horizontal position when used as a friction catch because in this Way the catch can be positioned at the greatest distance relative to the hinges and the frictional resistance developed by the catch is most effective in holding the door closed. Moreover, the clearance be tween the vertical edges of the door and frame is less subject to change. However, it is also within the scope of the invention to mount the device shown in Figs. 1 to 5 in a vertical position either at the bottom or at the top of the door. Of course, if the magnet unit 26 is installed in a vertical position at the top of the door frame and with the armature secured in the top edge of the door, it will be necessary to design the magnet unit so that the magnetic attractive forces between the inner end of the magnet element and the steel cup at the inner end of the housing will be sufiicient to overcome the weight of the movable magnet and thereby insure retention of the magnet out of the path of the door during open position of the latter. On the other hand, if the magnet unit is installed vertically at the bottom of the door, a lesser degree of magnetic attraction at the rear or inner end of the magnet unit will suffice since the weight of the magnet element itself will tend to hold the magnet in retracted position.

In addition to its use as a friction type catch, the device of Figs. l-5 may also be mounted for direct pull operation, i. c. with the magnetic attractive forces acting generally transversely to the plane of the door. When this structure is mounted for direct pull operation, the magnetic attraction between the single pole inner end of the movable magnet means and the steel cup 36 at the inner end of the magnet housing will provide a sufficient inner pull or force to hold the door in closed position in the same general functional manner as if a spring were incorporated in the structure.

In Figs. 6 to 9, I have illustrated a modification of the invention which is particularly adapted for mounting of the magnet unit at right angles to the plane of the closed door so that the magnetic attractive forces act generally transversely to the plane of the door for holding the door in-closed position. Referring first to Fig. 6, a fragmentary portion of a cabinet is shown comprising an upright frame portion 46, a base 47 with a door stop or strip 48, a shelf 49 extending horizontally relative to the upright frame portion 46, and a hinged door 51. A magnet unit, designated generally at 52, is mounted at the underside of the shelf 49 for coacting with an armature 53 mounted on the door 51 by a screw 54.

As seen in Figs. 7 to 9, the magnet unit 52 has an external housing of non-magnetic material which in this case comprises a two-part plastic casting. The two halves of the plastic casting are secured together along a longitudinal center line 56 by means of a suitable adhesive. two pairs of coacting guide pins and recesses, as at 57, being provided in the respective halves for insuring accurate alignment. The assembled plastic housing has an elongated tubular extension 58 with a bore 59 and an enlarged rear portion 61 with an internal cavity 62 com municating with the bore 59. A pair of bosses 63 are formed on opposite sides of the housing at the rear thereof and contain elongated slots 64 for mounting the housing. The unit is secured to the underside of the shelf 49 by means of a pair of screws 65 extending upwardly through the boss apertures 64 into the shelf 49, the elongated slots 64 permitting adjustment of the magnet unit relative to the shelf 49 prior to final tightening of the screws 65. Washers 66 are provided for retaining the head portions of the screws 65.

- A movable magnet unit of the same general design heretofore. described in connection with Figs. 1 to 5 is disposed within the plastic housing and consists of an elongated cylindrical bar magnet element 67 and a tubular shell 68 of steel or other magnetic metal fitted on the magnet element 67 with an annular air gap 69 therebetween. As before, the inner end of the shell 68 tapers inwardly to a portion 71 of reduced diameter having a tight frictional fit around the inner end of the magnet element 67 so as to move as a unit with the magnet element. The inner end extremity of the magnet shell 68 is flanged outwardly, as at 72, and a helical spring 73 is interposed between the flange 72 and a shoulder 74 at the juncture between the cavity 62 and the bore 59 of the plastic housing.

As will readily be seen, the magnet 67 and its attached shell 68 can move outwardly from the housing for engagement with the armature 53 on the door 51 as seen in Fig. 8. Thus, the magnet makes contact with the armature element and the spring 73 tends to urge the magnet element inwardly of its housing whereby to hold the door in closed position. In opening the door 51, the spring 73 is collapsed so as to provide a breaker action for disruption of the magnetic contact between the magnet and armature elements upon continued opening movement of the door 51. When the door is fully open the spring 73 automatically retracts the magnet element and attached shell into its innermost position, as seen in Fig. 9, with the flange 72 abutting the end wall of the housing cavity 62. Thus, it will be apparent that in this embodiment of the invention retraction of the movable magnet means is accomplished by means of a resilient member or spring whereas in the previously described embodiment the retraction of the magnet is accomplished by magnetic means. In addition, in the Figs. 6 to 9 embodiment the door is held in closed position by both the magnetic attraction between the armature and magnet elements and also by the mechanical effect of the spring. As best seen in Fig. 8, when the magnet means and the armature element are in contact for holding the door in closed position, the clearance space between the tubular shell 68 and the housing bore 59 permits a limited degree of angular cocking movement of the magnet means so as to allow full face contact between the catch elements in spite of any slight relative misalignment between the door and frame members.

Figs. 10 to 14 illustrate a modification of the above described embodiment but involves the same general operating principles. In Fig. 10, a fragmentary section of a double door cabinet is shown having an upright center post 76, a horizontal shelf 77, and a pair or" hinged doors I 78 which close against the center post 76. The doors 73 are provided with knobs 79 each of which also houses a magnetic catch as hereinafter described.

Since the door knob 79 also constitutes the housing for the moveable magnet means, it is made of non-magnetic material such as brass or plastic. The body of the knob structure consists of an elongated tubular or barrel portion 81 having a relatively flat spiral thread 82 which engages the wall of an aperture 83 in the door 7 S for rigidly securing the knob structure thereon. As will readily be understood, the knob structure is installed on the door 78 merely by screwing the threaded end of the tubular portion 8! into the aperture 83 until an intermediate radial flange portion 84 on the tubular barrel 31 seats tightly against the outer surface of the door 78. In this instance, the open end of the barrel portion 81 projects to a slight extent beyond the inner face of the door 73. The opposite end of the barrel portion 81 is formed with an integral enlargement or handle 86 which also provides a closed end portion for the central bore, indicated at 87, of the barrel portion 81. A non-magnetic bushing 88 is press fitted into the open end of the barrel portion 31 to provide a coacting shoulder or stop for the movable magnet element as described below.

The magnet element is again an elongated cylindrical bar 89 movably disposed within the tubular housing and fitted with an external magnetic sleeve or shell 91 for the same purpose hereinbefore described. At the inner end of the bar magnet 8'3, the shell 9i is of reduced diameter, as at 92, and has a rigid press fit on the magnet element 89 for movement as a unit therewith. At the opposite or outer end of the magnet element 89, the sleeve 91 is enlarged and is spaced annularly, as at 93, from the magnet to provide the desired annularly spaced double pole arrangement. The magnet sleeve is also collapsed or crimped upon itself to provide a radial flange or abutment 94, and a helical spring 96 CGHLiS between the abutment 94 and the bushing 88 for normally urging the magnet element 3 its attached shell or sleeve inwardly of the door knob housing. in this case, the annature unit is shown as an angle element 97 having one leg 98 adapted to be engaged by the contact ends of the magnet element 89 and its concentric sleeve 91. The other leg 99 of the angle 97 is secured to the upright edge of the center post 7:: by means of a pair of screws 1"1 extending through elongated slots 1 32 in the leg 99, it being understood that the slots 362 permit adjustment of the armature element during installation for proper coaction with the magnet unit.

in this modification of the invention, the operation is generally the same as heretofore described in connection with 6 to 9. in other words, when the door is closed as in Fig. 12, the magnet and attached sleeve 91 move outwardly against the force of the spring 96 into magnetic contact with the armature 97 so that both the magnetic force and the force of the spring hold the door in closed position. When the door is open, as in Fig. 13, the movable magnet element 89 and its attached sleeve 91 are shifted into retracted position by the action of the spring 96 with the inner end of the reduced portion 2 of the sleeve abutting the end wall of the housing bore 87. The combination of the door knob with the magnet housing affords a highly advantageous arrangement inasmuch as the door must have a knob or handle for opening the same and this particular embodiment, therefore, constitutes a highly attractive and economical modification of the invention.

Although the invention has been described with particular reference to certain specific structural arrangements, it is to be understood that various modifications and equivalent structures may be resorted to without departing from the scope of the invention as defined in the appended claims.

I claim:

1. In a magnetic catch, a magnet unit adapted to be mounted on one of a pair of door and frame members for eoaction with an armature mounted on the other of said members, said magnet unit comprising a magnet element adapted to undergo limited outward movement relative to said one member, a sleeve of magnetic metal rigidly mounted on s d magnet element for movement as a unit therewith, said sleeve having a reduced diameter portion rigidly secured around said magnet element at one end thereof and said sleeve also having an enlarged diameter portion spaced annularly from said magnet element at the other end thereof whereby to provide a pair of annularly spaced magnetic poles at said other end adapted to coact magnetically with the armature upon outward axial movement of the magnet element and its attached sleeve relative to said one member, and means for normally urging the magnet element and attached sleeve into retracted position relative to said one member.

2. In. a magnetic catch a ma Y et unit adapted to be mounted on one of a pa door and frame mefnbgrs f coaction with an armature mounted on the other of said members, sait. magnet unit comprising a non-maguetic housing strt cture aria ted to be mounted rigidly on said one member and having an open end portion, movable magnet means mounted Within said housing structure and adapted to move outwardly therefrom for projection through said open end portion into magnetic contact with the armature, said magnet means including a magnet element and a sleeve of magnetic metal rigidly carried on said magnet element, said sleeve having a reduced diameter portion rigidly secured around and in magnetic contact with said magnet element adjacent the inner end of the iatter and said sleeve also having an enlarged diameter portion annularly spaced from the magnet element at the outer end thereof whereby to provide at the outer contact end of the magnet means a pair of annularly spaced magnetic poles for coaction with the armature, and means providing a retractive force between said movable magnet means and said housing structure for normally urging the magnet means into retracted position within. said housing structure.

c device of claim 2 further characterized in that said last-named means comprises a magnetic metal element associated with said housing structure adjacent the inner end of said magnet element whereby to provide a magnetic attractive force therebetween, said magnetic attractive force being less than the magnetic attractive force between the outer end of the magnet means and the armature.

4. The device of claim 2 further characterized in that said last-named means comprises a spring means operatively coacting between said housing structure and said movable magnet means.

5. In a magnetic catch, a magnet unit adapted to be mounted on one of a pair of door and frame members for coaction with an armature mounted on the other of said members, said magnet unit comprising an elongated non-magnetic tubular housing adapted to be rigidly mounted on said one member, an elongated cylindrical bar magnet element disposed for axial movement in said housing and having magnetic poles at its ends, a sleeve of magnetic metal surrounding said magnet element and rigid therewith for movement as a unit with the magnet element, said sleeve being in magnetic contact with said magnet element at the inner end of the latter and being annular-1y spaced from the magnet element at the outer end of the latter whereby to provide a pair of annularly spaced magnetic poles at said outer end adapted to contact the armature upon outward movement of the magnet element and attached sleeve, and a magnetic metal element affixed at the end of said housing adjacent the inner end of the magnet element for exerting a magnetic retractivc force on the inner end of the magnet element.

6. The device of claim 5 further characterized in that said magnetic metal element comprises a generally cupshaped member rigidly secured to the inner end of the tubular non-magnetic housing.

7. The device of claim 5 further characterized in that said housing and said magnet element have coacting abutments for limiting the extent of said outward movement.

8. The device of claim 7 further characterized in that said abutments comprise a radial inwardly extending flange portion on said housing and a non-magnetic stop collar rigidly surrounding said magnet element adjacent the inner end or the latter.

9. n a magnetic catch, a magnet unit adapted to be mounted on one of a pair of door and frame members for coaction with an armature mounted on the other of said members, said magnet unit comprising non-magnetic housing structure adapted to be rigidly mounted on said one member and having an elongated tubular portion with an open end, an elongated magnet element mounted for axial movement in said tubular portion of the housing structure and having magnetic poles at its opposite ends, a sleeve of magnetic metal surrounding said magnet element and rigid therewith for movement as a unit with the magnet element, said sleeve bein in magnetic contact with said magnet element at the inner end of the latter and being annularly spaced from the magnet element at the outer end of the latter whereby to provide a pair of annularly spaced magnetic poles at said outer end adapted to contact the armature upon outward movement of the magnet element and attached sleeve through the open end of said housing structure, and resilient means operatively coacting between said housing structure and said sleeve for normally urging the magnet element and its attached sleeve inwardly into retracted position within the housm g structure.

10. In a magnetic catch, a magnet unit adapted to be nounted on one of a pair of door and frame members for coaction with an armature mounted on the other of said members, said magnet unit comprising non-magnet c housing structure adapted to be rigidly mounted on said one member and having an elongated tubular portion with an open end, an inwardly extending radial shoulder portion in said housing structure, an elongated magnet element mounted for axial movement in said tubular portion and having magnetic poles at its opposite ends, a sleeve of magnetic metal surrounding said magnet element and rigid therewith for movement as a unit with the magnet element, said sleeve being in magnetic contact with said magnet element at the inner end of the latter and being annularly spaced from the magnet element at the outer end of the latter whereby to provide a pair of annularly spaced magnetic poles at said outer end adapted to contact the armature upon outward movement of the magnet element and attached sleeve through the open end of said housing structure, an outwardly extending radial flange portion on said sleeve, and a helical spring surrounding said sleeve and operatively coacting between said shoulder portion and said flange portion for normally urging the magnet element and its attached sleeve inwardly into retracted position within the housing structure.

11. In a magnetic catch, a magnet unit adapted to be mounted on one of a pair of door and frame members for coaction with an armature mounted on the other of said members, said magnet unit comprising a non-magnetic housing having an elongated tubular portion and an enlarged portion having an enlarged cavity communicating with said tubular portion and providing a radial shoulder thereb'eltween, said enlarged portion of the housing providing attaching means for rigidly mounting the housing on said one member, an elongated cylindrical bar magnet disposed for axial movement in said tubular portion and extending into said cavity, an elongated sleeve of magnetic metal surrounding said magnet element and having a reduced diameter portion rigidly fitted on the inner end of said magnet element for movement as a unit with the latter and in magnetic contact with the inner end of the magnet element, the opposite end of said sleeve being annularly spaced from the outer end of the magnet element whereby to provide a pair of annularly spaced magnetic poles adapted to contact the armature upon outward movement of the magnet element and attached sleeve, an outwardly directed radial flange at the inner extremity of said sleeve, and a helical spring surrounding said sleeve within said cavity and coacting at its ends with said flange and said shoulder for normally urging the magnet element and its attached sleeve into retracted po sition within the housing.

12. The device of claim 2 further characterized in that said housing structure includes an open-ended tubular portion adapted to be rigidly mounted in an aperture in the door member and an enlarged grasping portion formed integrally at one end of said tubular portion and adapted to be located at the outer side of the door to function as a door knob, and said magnet means being disposed in said tubular portion for axial movement therein and being adapted to move outwardly from said housing structure under magnetic attraction into contact with an armature mounted on the frame member.

13. The device of claim 12 further characterized in that said tubular portion has an external threaded portion adapted to engage the wall of the aperture in the door member and a radial flange adapted to seat against the outer side of the door member.

14. The device of claim 2 further characterized in that said housing structure comprises a one-piece non-magnetic body having an enlarged grasping portion and an elongated ltubulazr extension closed at one end by said grasping portion and open at the opposite end, means for rigidly mounting the body on the door member with said grasping portion at the outside to function as a door knob and said tubular extension projecting through the door memoer with said magnet means being disposed in said tubular extension and being adapted to move beyond the open end of said tubular extension into contact with an armature mounted on the frame member for holding the door closed, and said last-named means comprises a spring operative ly coacting between said tubular extension and said magnet means for normally urging the latter into retracted position within said tubular extension.

15. In a magnetic catch, a magnet unit adapted to be mounted on one of a pair of door and frame members for coaction with an armature mounted on the other of said members, said magnet unit comprising a magnet element adapted to undergo limited outward movement relative to said one member, a sleeve of magnetic metal rigidly mounted on said magnet element for movement as a unit therewith, said sleeve having a reduced diameter portion rigidly secured around said magnet element at one end thereof and said sleeve also having an enlarged diameter portion spaced annularly from said magnet element at the other end thereof whereby to provide a pair of annularly spaced magnetic poles at said other end adapted to enact magnetically with the armature upon outward movement of the magnet element and its attached sleeve relative to said one member, abutment means adjacent the inner end of said sleeve extending radially outwardly from the sleeve for limiting the extent of said outward movement, and means for normally urging the magnet element and attached sleeve into retracted position relative to said one member.

16. In a magnetic catch, a magnet unit adapted to be mounted on one of a pair of door and frame members for coaction with an armature mounted on the other of said members, said magnet unit comprising a non-magnetic housing structure adapted to be mounted rigidly on said one member and having an open end portion, movable magnet means mounted Within said housing structure and adapted to move outwardly therefrom for projection through said open end portion into magnetic contact with the armature, said magnet means including a magnet element and a sleeve of magnetic metal rigidly carried on said magnet element, said sleeve having a reduced diameter portion rigidly secured around and in magnetic contact with said magnet element adjacent the inner end of the latter and said sleeve also having an enlarged diameter portion annularly spaced from the magnet element at the outer end thereof whereby to provide at the outer contact end of the magnet means a pair of annularly spaced magnetic poles for coaction with the armature, abutment means adjacent the inner end of said sleeve extending radially outwardly from-the sleeve for coaction with said housing structure whereby to limit the extent of outward movement of said magnet means, and means providing a retractive force between said movable magnet means and said housing structure for normally urging the magnet means into retracted position Within said housing structure.

17. The device of claim 10 further characterized in that said tubular portion has a bushing rigidly mounted therein and providing said radial shoulder portion.

References Cited in the file of this patent UNITED STATES PATENTS 2,519,435 Byrd Aug. 22, 1950 FOREIGN PATENTS 672,928 Great Britain May 28, 1952 693,564 Great Britain July 1, 1953