US2877041A

US2877041A - Magnetic latch for refrigerator door

Info

Publication number: US2877041A
Application number: US538508A
Authority: US
Inventors: Thomas P Foley
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1955-10-04
Filing date: 1955-10-04
Publication date: 1959-03-10
Anticipated expiration: 1976-03-10

Description

T. P. FOLEY MAGNETIC LATCH FOR REFRIGERATOR DOOR March 10, 1959 v 2 Sheets-Sheet 1 Filed Oct. 4, 1955 FIG. l

FIG. 2

{Iii-1a Q 7 FIG. 3

INVENTOR.

THOMAS P. FOLEY BY H [5 ATTO RNEY March 10, 1959 "r. P. FOLEY 2,877,041

MAGNETIC LATCH FOR REFRIGERATOR DOOR Filed Oct. 4, 1955 2 Sheets-Sheet 2 FIG.4

FIG. 5

INVENTOR. THOMAS P. FOLEY HIS ATTORNEY United States Patent MAGNETIC LATCH FOR REFRIGERATOR DOOR Thomas P. Foley, Louisville, Ky., assignor to General Electric Company, a corporation of New York Application October 4, 1955, Serial No. 538,508 Claims. (Cl. 292-4515) The present invention relates to a magnetic latch and is more particularly concerned with a magnetic latch for refrigerators and similar appliances including a gasket or similar means for sealing the area around the cabinet access opening and between the cabinet and the door.

On cabinets such as refrigerator cabinets and the like where it is necessary to prevent air leakage from within the cabinet, it is customary to provide a gasket adapted to encircle the access opening of the cabinet for sealing the area around the access opening against leakage. Because of the air-tight seal effected when the door is in its closed position, the effect of a hard or even moderate slamming of the door is to compress the air within the cabinet so quickly and before it can escape that the compressed air sets up a counter force tending to re-open the door. No rebound problem of this type exists with the usual mechanical latches employed for latching refrigerator doors and the like since these latches are of the positive latching type and once the latch is in engagement with its cooperating strike, the compressed air counter force cannot break this engagement.

Unlike the usual mechanical latches, magnetic latches do not have a positive or interlocking action but rather depend upon the magnetic attraction between a magnet and a cooperating armature for their entire holding power. This attractive force is high set when the armature is in. actual contact with the magnet, that is, under zero air gap conditions, but rapidly decreases as the armature and magnet are moved away from one another. It will be seen therefore that a magnetic latch having a holding force sufficient to obtain the proper gasket sealing, may not be powerful enough to return the door to a gasket sealing position following a rebound of the door as a result of a moderate or hard slam once actual physical contact between the two has been broken. On the other hand, a magnetic latch including a magnet having suflicient pull or field strength to take care of the rebound problem is not only more expensive but may require an undesirably high door opening pull in order to obtain access to the cabinet.

An analysis of the requirements for a satisfactory magnetic latch which will take care of the rebound problem involved in the closing of a refrigerator door or the like indicates that a complete refrigerator door closure involves two separate phases whichare more orv less additive. The first phase is that of bringing the door from a fully or partially open position to a position or point where the gasket is about to touch or barely touches the outer case on the latch side. The second phase comprises sealing the door by applying a load which will compress the gasket against its mating surface.

To accomplish the first phase there is required a small force acting through a relatively large or long distance. The principal opposition to movement of the door are the door inertia at a fully stopped position, hinge 2,877,041 Patented Mar. 10, 1959 friction, and partial gasket compression on the hinge side and along the top and bottom edges of the door. To accomplish the second phase, there is required a large force acting through a relatively small distance in order that the proper compression of the entire gasket and the sealing thereof be obtained and that the door he held in a fully sealed position. For example, a magnetic latch having a zero air gap pull in the order of 12-20 pounds maximum was found to be ample for sealing the entire gasket perimeter of a refrigerator cabinet where the total compression of the gasket was of the order of 4-7 pounds. On the other hand when the same door was closed with a moderate or hard slam and measurements were made of the compressed air counter force it was found that the peak air force was of the order of 25-50 pounds total which is too high for the magnet to overcome.

Various schemes have been used or proposed to solve the rebound problem. One such scheme comprises air venting means to permit a rapid escape of air from the cabinet as the door closes. Such means may comprise a suitable opening provided with means such as a flapper valve or the like for sealing the opening after the air pressure equalizes. Primarily for economical reasons such schemes are not particularly satisfactory. Various other devices intended to bias the door to a closed condition or prevent rebound such as mechanical snubbers, camtype hinges, out of line hinges and spring-biased hinges also present problems from either the cost or the appearance standpoints. Furthermore, these means of eliminating or overcoming rebound, all of which involve the use of a device which most conveniently form part of the hinge structure or are positioned on the cabinet close to the hinge mechanism, have a relatively small mechanical advantage in those positions and cannot be satisfactorily applied to the latch side of the door or cabinet.

It is therefore a principal object of this present invention to provide a magnetic latch for refrigerator doors and the like including as part of the latch structure means for absorbing or overcoming the rebound of the door following a moderate or hard slam.

A further object of the invention is to provide an improved magnetic latch of simple and economical construction including an auxiliary or second armature adapted to return the door to a latching position with a, primary keeper following rebound thereof.

Further objects and advantages of the invention will become apparent as the following description proceeds and the features of novelty which characterize the invention will be pointed out with particularity in the claims annexed to and forming part of this specification.

In carrying out the object of the present invention, there is provided a magnetic latch including a magnet,

preferably of the permanent type, and an armature or keeper assembly which is adapted to cooperate with the magnet and which comprises a first, fixed or rigidly mounted armature and a second or auxiliary, movable means should not be so great as to require the application of excessive pull by the user to open the door. The movable armature includes means adapted to return the door to a latching position following a rebound resulting from a moderate or hard slamming of the door.

For a better understanding of the invention reference may be had to the accompanying drawings in which Fig. 1 is a general view of a refrigerator including a magnetic latch of the present invention;

Fig. 2 is a partial, sectional view along line 2-2 of Fig. 1 illustrating one embodiment of the present invention with the door in a closed position relative to the cabinet;

Fig. 3 is a view illustrating the operation of the embodiment of Fig. 2 under certain conditions including rebound of the refrigerator door;

Fig. 4 is a fragmentary sectional view of a second embodiment of the latch of the present invention showing the door in its normally closed position;

Fig. 5 is a similar view of the second embodiment showing the elements of the latch at the moment of contact of the door gasket with the cabinet; and

Fig. 6 is a view of the same modification showing the latch elements in a door rebound position.

Referring to the drawings, Fig. 1 illustrates a refrigerator including a cabinet 1 containing a storage compartment 2, the access opening to which is closed by a door 3. The door is suitably mounted on the cabinet by means of hinges (not shown) and in order to seal the refrigerator in the region of the access opening, a gasket 4 (Fig. 2) is provided which entirely encircles the access opening and seals the space between the cabinet face portion 5 and the door 3.

The magnetic latch of the present invention which is designed to hold the door in its closed position and to compress the gasket 4 into sealing relationship with the cabinet comprises a magnet means secured either to the door or to the cabinet member of the refrigerator and an armature assembly secured to the other of these members. The modification shown in Fig. 2 comprises a permanent magnet 10 having pole pieces 11 encased in a non-magnetic metal or plastic housing 12 with only the pole faces 13 exposed. It is to be understood that the non-magnetic housing 12 is provided primarily for appearance and support purposes and is not an essential element of the latch. In the modification shown the magnet means is secured to the door by screws 14 extending through the inner wall 15 of the door and engaging the non-magnetic housing 12.

Supported on the cabinet member, or more specifically on the face portion 5 thereof, for cooperation with the magnet 10 is an armature assembly generally indicated by the numeral 18. This armature assembly includes a fixed or rigidly mounted armature 19 secured as by means of screws 20 to the face 5 of the cabinet and a smaller movable armature 21 integrally secured to a guide rod 22 extending through an aperture 23 positioned adjacent the mid-section of the armature 19 and spring-biased to the position shown in Fig. 2 by means of a spring 24 arranged between the stop 25 on rod 22 and the inner surface of the cabinet face portion 5. The housing 26 having a guide aperture 27 in axial alignment with the aperture 23 serves to support and guide the rod 22 and maintain the cabinet insulation 28 away from the spring 24. The principal function of the armature 21 is that of maintaining contact with the magnet during door rebound and returning the door to a sealing position after the rebound forces have been dissipated.

In considering the operating of the latch shown in Figs. 2 and 3, Fig. 2 illustrates the relative position of the various elements of the latch both (a) when the door is in the fully closed and gasket sealing position and (b) at the instant of impact during a moderate or hard slamming of the door. Figure 3 illustrates the relative positions of the various latch elements (a) at the point of maximum rebound following a hard slam and (b) When the door is being normally opened during normal use thereof with the auxiliary armature 21 about to break contact with the magnet 10.

When the door is in its closed position as shown in Fig- 4 we 2, the gasket 4 is compressed into sealing engagement with thev face portion 5 of the cabinet by the magnetic forces which hold the poles 11 of the magnetic means in engagement with the principal armature 19. The auxiliary armature 21 is maintained in a position adjacent the face of the principal armature 19 by the compression spring 24. The particular forces which serve to hold the door in the closed position will depend upon a number of factors including the field strength of the magnet 10, the magnetic mass of the primary armature 19, the magnetic mass of the auxiliary armature 21 insofar as it may detract from the forces between the magnet and primary armature 19, and the air gap between the auxiliary armature 21 and the magnet 10 as represented by the layer 30 of non-magnetic material between the armature 21 and the magnet 10. Likewise the length of the auxiliary armature 21 or more specifically the distance between its end portion 31 and the poles 11 may become a factor in the same way as the magnetic mass of this armature.

By the use of a non-saturating fixed armature 19 which is in contact with the poles 11 of the magnet when the door is in the normally closed position substantially all of the magnetic lines of force pass through that armature so that the movable armature 21 and its biasing spring 24 do not substantially contribute to or detract from the forces holding the door in the closed position.

Since a high quality magnet means is the most expensive element in the latch structure, it is desirable to employ a permanet magnet having a field strength which is just suflicient to seal the gasket and maintain the door in a closed position against the compressive forces of the gasket during normal use of the refrigerator.

However in order to allow for manufacturing variations in the strength of the magnet, the sealing or compressive characteristics of the gasket etc., there is preferably employed a magnet having a field strength somewhat greater than that required to seal the average gasket and a nonsaturating armature 19 which will utilize fully the zero air gap pull of the magnet. The difference between the total zero air gap pull of the magnet and that required to seal the gasket, which, for example, ordinarily range from about 8 to 12 pounds, represents the pull necessary to open the door during normal use of the refrigerator.

The upper limit of this difference is of course controlled by the fact that too high a door opening pull may not be acceptable to the user.

During any movement of the door from its closed position, as soon as the actual physical contact between the pole faces 13 and the fixed armature 19 is broken thereby interrupting the magnetic flux flow through the fixed armature 19, there is a transfer of many of the magnetic lines of force from the fixed armature to the auxiliary armature 21 with the result that this armature is attracted to the magnet and moves with the door and away from the fixed armature 19 against the action of spring 24.

During normal opening of the door the movable armature 21 of course follows the magnet 10 until the spring 24 bottoms at which point contact between the armature and magnet is broken and the door swings freely. To take care of rebound conditions, this movable armature 21 and spring 24 are so designed that the armature will maintain magnetic contact with the magnetic means during the entire rebound movement. In other words the magnetic characteristics of the movable armature 21 and the strength of spring 24 must be such that this armature Will be attracted to the magnet or will continue to be attracted to the magnet against the biasing action of the spring 24 whenever the door rebounds away from its closed position. The term magnetic characteristics as used in this connection has reference to a balancing of a number of factors all of which contribute to the attainment of the desired result. Some of the factors involved are the magnetic mass of the auxiliary keeper 21, the air gap between the keeper and the magnet as represented by the non-magnetic layer 30, the distance between the ends of the armature 21 and the poles 13 of the magnet and the strength of the compression spring 24. In order to effectively use all of the zero air gap flow of the magnet for maintaining the door in its closed position the magnetic mass of the auxiliary keeper 21 preferably should be less than the magnetic mass of the principal armature 19. Also by employing an auxiliary keeper of relatively low magnetic mass the air gap 30 may if desired be omitted. However, its presence is preferred since it provides a more accurate control of the attractive forces between the magnet and the auxiliary armature 21 that can be obtained merely by a variation of the magnetic mass or shape of the armature. The distance between the ends 31 of the armature 21 and the pole faces 13, or more specifically the poles 11, is also an important factor but it is not critical in the sense that these distances may be zero and in fact the ends of the armature 21 may actually overlap a portion but not all of the pole faces 13 provided armature 21 has a magnetic mass substantially less than that of the fixed armature 19 so that it does not interfere with the holding action of the fixed armature. The importance of these factors collectively will best be appreciated from a consideration of the fact that the part which the movable keeper 21 can play in maintaining the door in a closed position is limited by the biasing action of the spring 24 in its extended or substantially relaxed state which in turn must be relatively small in order to permit the movable armature 21 to maintaincontact with the magnetic means during rebound of the door following a moderate or hard slam.

As has been previously indicated, the effect of a hard or even moderate slam is to compress the air within the refrigerator so quickly that a large force in the order of 25-50 pounds total at its peak instant acts upon the door to reopen it thus breaking contact between the pole faces 13 and the fixed armature 19. Employing a low cost magnet of a strength not substantially in excess of that required to seat the gasket and without the movable spring biased armature 21 adapted to maintain contact with the magnet means during the rebound period of the door and to return the door to a position where the fixed keeper 19 again enters the magnetic field of the magnet means 10, satisfactory closing and sealing of the door can be obtained only upon a light slam or closing force. To effect proper action of the latch under other closing conditions, the spring 24 should be light enough to permit movement of the armature 21 forwardly and away from the fixed armature and in magnetic contact with magnet 10 during a heavy rebound but on the other hand should be sufiiciently strong to limit or snub the rebound movement of the door and return the door to a latching position in which the fixed armature is attracted to the magnet.

The action of the auxiliary or movable armature during rebound is illustrated in Figure 3 showing the relative positions of the door and cabinet and the various elements of the latch at the point of maximum rebound following a hard slam of the door. Since the air trapped within the storage compartment of the cabinet during the slamming of the door is quickly released as soon as contact between the gasket 4 and the cabinet face 5 is broken, the action of the compressed air is practically instantaneous so that the spring 24 then needs only to overcome the inertia of the door and return it from the rebound position to a position where the magnet 10 can again act on the fixed keeper 19.

In the modification of the invention shown in Figures 4 to 6 inclusive a movable or auxiliary armature is employed which forms part .of the magnetic path between the magnetic means and the fixed armature under certain conditions where the force applied during closing of the door has not been sufiicient to establish physical contact between the fixed armature and the magnet. In order to obtain satisfactory sealing of a refrigerator door by the gasket, it is necessary that the gasket be of such thickness that it will be compressed somewhat when the door is in its normal closed position with the magnet poles in contact with the fixed armature. In other words during closing of the door, the gasket contacts its mating surface before actual physical contact is established between the fixed armature and the magnet poles. At this time, air is compressed, even though the gasket is not fully compressed and sealed, and rebound starts to occur.

The modification of the magnet latch shown in Figures 4 to 6 is particularly designed to avoid this possibility i. e. rebound due to air compression before poles engage main keeper. While in this modification only one pole indicated by the numeral 35 is shown it is to be understood that this pole forms part of the magnetic means including an additional pole and a permanent magnet arranged as shown for example in Figure 2. The magnetic means is suitably mounted on the door 36 in cooperative relationship with a fixed armature 37 mounted on a face portion 38 of a cabinet. Numeral 39 indicates the sealing gasket which seals the space between the door 36 and the face portion 38 of the cabinet.

The auxiliary or movable armature in this modification comprises a rod of magnetic material 40 having one end extending through an aperture 41 in the armature 37 opposite the magnetic pole 35 and the other end journalled in an opening 42 of the frame member 43. A heavy spring 44 and a light spring 45 position the magnet contacting end 46 of the rod 40 as shown in Figure 5 so that the end 46 is in contact with the pole 35 when the door is in a position in which the gasket 39 is in contact with the cabinet face 38 in a substantially uncompressed state. The light spring 45 is loaded to keep the rod end 46 in the position shown in Figure 5 both when the door gasket 39 is in uncompressed contact with the cabinet face 38 and also when the door is open. The heavy spring 44 is practically unloaded under these conditions as its function is the same as spring 24 of the latch modification shown in Figures 2 and 3, that is, to return the door to a closed position following a rebound.

On a light slam the magnet poles 35 approach the extending end 46 of the auxiliary armature 40 and upon contact therewith, the main armature is within the field of the magnet. Since a light slam builds up very little counter-force air pressure within the cabinet, and as the opposition of the spring 45 is very slight, the door moves to a position in which the magnet pole 35 engages the fixed armature 37. The result is a compression of the gasket 39 to seal the cabinet opening and a holding of the door in its closed position by the magnetic forces between the magnetic means and the fixed armature 37.

On a moderately hard or hard slam the movable keeper 40 acts in the same manner as the movable keeper 21 in that during the rebound movement of the door the armature 40 moves forwardly through the aperture 41 against the biasing action of the spring 44 to maintain contact with the pole 35 during the rebound movement and to return the door to a sealing position following the rebound. The fixed armature 37 then cooperates with the magnetic means to seal the gasket and hold the door in its closed position.

During a closing of the door by a force which may be described as between a light and moderate slam, the magnetic pole 35 approaches and contacts the end 46 of the movable armature 40 and rebound may occur before any actual physical contact is made between the pole 35 and the fixed armature 37 However by normally positioning the end 46 of the rod forward from the surface of the keeper or armature 37 or in aboutthe same plane vas the gasket surface, contact between the pole 35 and the armature 40 is made at the same time that the gasket 39 contacts the cabinet face portion 38. With the contact established the rod 40 follows the magnet 35 during the rebound and the heavy spring 44 returns the door to its normally closed position.

From the foregoing it will be seen that there has been provided a relatively inexpensive magnetic latch adapted to maintain a refrigerator door in sealing relationship with the cabinet and to return the door to a sealing relationship following any rebound thereof. While the fixed armature has been shown as a separate element it is to be understood that whenever the cabinet face portion is composed of a magnetizable material, this face portion may form the fixed armature component of the latch. Likewise when the face portion of the cabinet is magnetic additional magnetic mass for the fixed keeper may be in the form of a low-carbon steel member aifixed to the rear or insulation side of the cabinet face portion in a position to supplement the magnetic mass of the face portion and provide a non-saturating fixed armature. While specific embodiments of the present invention have been shown and described, it is to be understood that the invention is not limited thereto but it is intended by the appended claims to cover all such modifications and changes as fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. A magnetic latch for holding a door member in closing relation with a cabinet member comprising a magnet adapted to be secured to one of said members, a cooperating armature assembly adapted to be mounted on the other of said members, said assembly comprising a first substantially rigidly mounted armature and a second movable armature movable away from said first armature in the direction of said magnet and adapted to maintain magnetic contact with said magnet during a rebound period following closure of the door, and spring means biasing said movable armature toward said other member, said spring means being adapted to return said door to a position in which said first armature is within the field of said magnet following said rebound period.

2. A magnetic latch for holding a door member in closrelation with a cabinet member comprising a magnet adapted to be secured to one of said members, a cooperating armature assembly adapted to be mounted on the other of said members, said assembly comprising a first substantially rigidly mounted armature and a second movable armature spring-biased toward said other member and movable away therefrom in the direction of said magnet aud adapted to move with and maintain magnetic contact with said magnet during a rebound period follow ing closure of the door and return said door to a closed position.

3. A magnetic latch for holding a door member in closing relation with a cabinet member against the compressive force of a door sealing gasket comprising a magnet adapted to be secured to one of said members, a cooperating armature assembly adapted to be mounted on the other of said members, said assembly comprising a first substantially rigidly mounted armature of sulficient magnetic mass to seal said gasket and a second movable armature spring biased toward said other of said members and adapted to move with said magnet and away from said other of said members and maintain magnetic contact with said magnet during a rebound period following closure of the door.

4. The magnetic latch of claim 3 in which said rigidly mounted armature includes an aperture therein at the point of contact with a pole of said magnet and said second armature is in the form of a magnetic pin slidably extending through said aperture.

5. The magnetic latch of claim 3 in which said first armature includes an aperture therein at the point of contact with a pole of said magnet and said second armature includes a mounting portion extending through said aperture and a magnet engaging portion disposed forward from the face of said first armature when said door member is open for engaging said magnet when said gasket is in uncompressed Contact with the surfaces of both of said members. 7

6. A magnetic latch for holding a door member in sealing relation with a cabinet member against the compressive force of a sealing gasket, said latch comprising a ermancnt magnet adapted to be mounted on one of said members, and an armature assembly adapted to be mounted on the other of said members having a fixed portion and a movable portion spring biased toward said other member, the magnetic mass of said movable portion and the strength of said spring being such that said movable portion will move away from said other of said members and will maintain contact with said magnet during rebound of the said door following closure thereof to return said door to a closed position.

7. A magnetic latch for holding a door member in closing relation with a cabinet member, said latch comprising a magnet, means for securing said magnet to one of said members, a cooperating armature assembly and means for securing said assembly to the other of said members, said assembly including a first rigidly-mounted armature of relatively high magnetic mass, a second armature of lower magnetic mass, means including a spring for biasing said second armature to a position adjacent said first armature when said door member is open and being of a strength such that said second armature will move away from said other of said members to follow said magnet and maintain contact therewith during rebound of the door following closure thereof, said spring being adapted to return said door to a position in which said first armature is within the field of said magnet.

8. A magnetic latch for holding a door member in closing relation with a cabinet member, said latch comprising a magnet, means for securing said magnet to one of said members, a cooperating armature assembly and means for securing said assembly to the other of said members, said assembly including a first rigidly-mounted armature of relatively high magnetic mass, a second armature of lower magnetic mass, means including a spring for holding said second armature adjacent said first armature when said door member is open and for permitting said second armature to move away from said first armature and move with said magnet and maintain contact therewith during rebound of the door following closure thereof, said spring being adapted to return said door to a position in which said first armature is within the field of said magnet.

9. A magnetic latch for holding a door member in closing relation with a cabinet member against the compressive forces of a door sealing gasket, said latch comprising a magnet, means for securing said magnet to one of said members, a cooperating armature assembly and means for securing said assembly to the other of said members, said assembly including a first rigidly-mounted armature of a magnetic mass sufiicient to compress said gasket, a second armature, means including a spring for holding said second armature adjacent said first armature when said door member is open and for permitting said second armature to move away from said other of said members to follow said magnet and maintain contact therewith during rebound of the door following closure thereof, said spring being adapted to return said door to a position in which said first armature is within the field of said magnet.

10. A magnetic latch for holding a door member in closing relation with a cabinet member, said latch comprising a U-shaped magnet, means for securing said magnet to one of said members, a cooperating armature assembly and means for securing said assembly to the other of said members, said assembly including a first rigidlymounted armature adapted to make contact with the poles of said magnet, a second armature positioned intermediate the poles of said magnet when said door is closed, spring means for holding said second armature adjacent said first armature when said door is open and to permit said second armature to move with said magnet and maintain magnetic contact therewith during rebound of the door follow- 9 ing closure thereof, said spring being adapted to return 2,662,787 said door to a position in which said first armature is 2,673,755 within the filed of said magnet.

References Cited in the file of this patent 5 7 9 UNITED STATES PATENTS 2,252,144 Taylor et a1. Aug. 12, 1941 11 Horvay Dec. 15, 1953 Asp Mar. 30, 1954 FOREIGN PATENTS Great Britain June 1, 1955